Rozprawy doktorskie na temat „Nanofibres of chitosan”

Organophosphates and carbamates are potent inhibitors of the neurotransmitter acetylcholinesterase. This inhibition results in the blocking of nerve signal transference into the post synaptic neuron leading to loss of muscle action and death. Because of the universal mechanisms of signal transduction in animals, these inhibitors have been widely used as agricultural pesticides as well as chemical warfare agents (nerve agents). Health issues associated with pesticide usage result from the fact that both the pesticides and their breakdown products often end up in water and food sources as well as in the soil. As a result, there has been an increase in the number of studies aimed at the detection of these pesticides in the environment. One popular research area is enzyme based biosensor construction. Some important criteria for consideration during the construction of biosensors are the importance of a suitable solid support as well as the enzyme immobilisation method. Recently, there has been increased interest in using nano-scale material e.g. using nanoparticles as enzyme support material. This is largely due to their advantages such as large surface area to volume ratio as well as reduced mass transfer resistance. Electrospinning is a straight forward and cost effective method for producing nanofibres from any soluble polymer(s). The applications of electrospun nanofibres have been reported in clinical studies, biofuel production as well as bioremediation. In this study two polymers were selected: nylon for its mechanical stability and chitosan for its biocompatibility and hydrophilicity, for the fabrication of electrospun nanofibres which would function as immobilisation support material for acetylcholinesterase. The first objective of this study was to electrospin nanofibres from a nylon-6 and chitosan blend solution. A binary solvent system consisting of formic acid and acetic acid (50:50) successfully dissolved and blended the polymers which were subsequently electrospun. Scanning electron microscopy characterisation of the nanofibres showed that (i) a nylon-6: chitosan ratio of 16%: 3% resulted in the formation of bead free nanofibres and (ii) the fibres were collected in non-woven mats characterised by different size nanofibres with average diameters of 250 nm for the main fibres and 40 nm for the smaller nanofibres. Fourier transform infra-red (FT-IR) analysis of the nanofibres indicated that a new product had been formed during the blending of the two polymers. The second aim of the study was to carry out a facile immobilisation of electric eel acetylcholinesterase via glutaraldehyde (GA) cross-linking. Glutaraldehyde solution 5% (v/v) resulted in the immobilisation of 0.334 mg/cm² of acetylcholinesterase onto the nanofibres. The immobilisation procedure was optimised with reference to acetylcholinestease and crosslinker concentrations, incubation time and the cross-linking method. A comparative investigation into the optimum pH and temperature conditions, pH and thermal stabilities, substrate and inhibition kinetics was then carried out on free and immobilised acetylcholinesterase. The final objective of this study was to determine the storage stabilities of the immobilised and free enzymes as well as the reusability characteristics of the immobilised acetylcholinesterase. Several conclusions were drawn from this study. Acetylcholinesterase was successfully immobilised onto the surface of nylon-6:chitosan nanofibres with retention of its activity. There was a shift in the pH optimum of the immobilised acetylcholineseterase by 0.5 units towards a neutral pH. Although both free and immobilised acetylcholinesterase exhibited the same optimum temperature, immobilised acetylcholinesterase showed enhanced thermal stability. In terms of pH stability, immobilised acetylcholinesterase showed greater stability at acidic pH whilst free acetylcholinesterase was more stable under alkaline pH conditions. Relative to free acetylcholinesterase, the immobilised enzyme showed considerable storage stability retaining ~50% of its activity when stored for 49 days at 4°C. Immobilised acetylcholinesterase also retained > 20% of its initial activity after 9 consecutive reuse cycles. When exposed to fixed concentrations of carbofuran or demeton-S-methyl sulfone, immobilised acetylcholinesterase showed similar inhibition characteristics to that of the free enzyme. The decrease in enzyme activity observed after immobilisation to the nanofibres may have been due to several reasons which include some enzyme molecules being immobilised in structural conformations which reduced substrate access to the catalytic site, participation of the catalytic residues in immobilisation and enzyme denaturation due to the reaction conditions used for acetylcholinesterase immobilisation. Similar observations have been widely reported in literature and this is one of the major drawbacks of enzyme immobilisation. In conclusion, nylon-6:chitosan electrospun nanofibres were shown to be suitable supports for facile acetylcholinesterase immobilisation and the immobilised enzyme has potential for use in pesticide detection. Future recommendations for this study include a comparative study of the GA cross-linking method for AChE immobilisation which will lead to more intensely bound enzyme molecules to prevent non-specific binding. An investigation into the effect of inhibitors on stored immobilised AChE, as well as reactivation and reuse studies, may also be useful for determining the cost-effectiveness of reusing immobilised AChE for pesticide detection in environmental water samples. Several models have been designed for the determination of the kinetic parameters for immobilised enzymes. These take into account the mass transfer resistance as well as the overall charge of the immobilisation matrix. The use of these models to analyse experimental data will give a clear understanding of the effects of immobilisation on enzyme activity

Les biomatériaux sont très largement utilisés dans le soin de maladies, de brûlures ou de blessures. Ils sont utilisés sous la forme de dispositifs médicaux destinés à des applications extra ou intra corporelles : pansement, prothèses vasculaire, filet de réparation de hernie, ligament artificiel etc.. Ils se doivent donc notamment d’être biocompatibles et hémocompatibles, mais la recherche vise actuellement à leur apporter des propriétés bioactives supplémentaires (antibactérienne, anti inflammatoire, anti-thrombotique, régénérative etc.). Le chitosan (CHT) est un polymère cationique biosourcé couramment utilisé en tant que biomatériau pour ses propriétés biologiques intrinsèques (biocompatible, bio résorbable, antibactérien, hémostatique, pro-cicatrisant). Dans ce contexte, nous avons élaboré deux types de membranes bioactives (antibactérienne et anti thrombotique) constituées d’enchevêtrements de nanofibres (NFs) à base de chitosan grâce à la technologie innovante de l’electrospinning. Premièrement, des NF antibactériennes ont été élaborées par association du CHT avec un polymère anionique de cyclodextrine (PCD), molécule cage connue pour piéger puis libérer de façon ralentie des molécules bioactives. Deux types de NFs chargées en triclosan (TCL) choisi comme principe actif antibactérien ont été préparées : 1) par mélange homogène CHT+PCD/TCL, ou en structure cœur-peau avec [PCD/TCL] en cœur, et [CHT] en peau. Deuxièmement, des NFs à activité anti-thrombotiques ont été obtenues en modifiant chimiquement le CHT par des fonctions sulfonates qui ont apporté des propriétés anticoagulantes similaires à celles de l’héparine (heparin-like), suivi de l’étape d’électrofilage
Biomaterials are designed to cure people suffering from chronic diseases or suffer injuries or burns. They are developed for intra or extra bodily applications (wound dressings, vascular prostheses, inguinal meshes artificial ligaments etc.). Thus, they must be biocompatible and hemocompatible at first, but research presently aims to give them additional properties (antibacterial, anti-thrombotic, regenerative). Chitosan (CHT) is a cationic biosourced polymer commonly used for these applications thanks to its intrinsic biological properties (biocompatible, bioresorbable, antibacterial, hemostatic, healing)In this context, we developed two kinds of bioactive membranes based on chitosan nanofibers by using the innovative electrospinning technology. Firtsly antibacterial NF have been obtaines by associating CHT with a anionic cyclodextrin polymer (PCD), known to trap and slowly release some bioactive compounds. Twotwo kinds of NFs loaded with triclosan (TCL) have been prepared: mixed CHT+PCD/TCL and core-sheath with PCD/TCL in core, and [CHT] as sheath. Secondly, antithrombotic NFs have been elaborated by chemically modifying CHT with sulfonate groups giving heparin-like properties to the NFs after electrospinning

Les textiles sont utilisés dans le domaine biomédical, notamment pour le soin des plaies ou pour la conception de prothèses de substitution ou de régénération d’organes endommagés par la maladie ou par cause accidentelle. Le cahier des charges des textiles médicaux évolue vers l’élaboration de biomatériaux biorésorbables et bioactifs capables d’interagir spécifiquement avec les tissus vivants en fonction de leur nature. Dans ce contexte, le projet de recherche consiste à concevoir, par electrospinning, deux types de membranes nanofibreuses bioactives à base de chitosane. Dans une première approche, des nanofibres de chitosane à ont été fonctionnalisées par la polydopamine qui contient des groupements catéchols capables d’induire la biominéralisation in vitro dans un milieu riche en ions calcium et phosphate. Ces membranes à propriétés ostéoinductrices pourraient être utilisées comme scaffolds pour la régénération tissulaire guidée en parodontologie. Dans une deuxième approche, l’élaboration de nanofibres à propriétés anticoagulantes à base de chitosane a été menée. Le chitosane a été d’abord chimiquement modifié par des groupements sulfonates. Les paramètres de synthèse ont permis de contrôler le degré de sulfonation du chitosane et ses nouvelles propriétés caractéristiques d’un polyampholyte ont été observées. Les essais biologiques effectués ont montré que ces dérivés sulfoniques sont non hémolytiques et bénéficient de propriétés anticoagulantes. Puis, des nanofibres de chitosane sulfoné ont été obtenues par electrospinning conduisant à des membranes à propriétés antithrombotiques, ce qui en fait des candidats de choix pour la fonctionnalisation de stents vasculaires
Textiles are widely used in the biomedical field, in particular for the care of wounds or the design of prostheses for strengthening or regenerating organs damages by the disease of by accidental cause. The specifications for medical textile are evolving towards the development of bioresorable and bioactive biomaterials that are capable of interacting with living tissues according to their nature. In this context, the research project consists of generating, by electrospinning, two types of biomimetic and bioactive nanofibrous membranes based on chitosan. In a first approach, nanofibres of chitosan have been functionalized by polydopamine that contains catechol groups capable of inducing the in vitro biomineralization in a medium rich in calcium and phosphate ions. Thus, these nanofibrous membranes with osteoinductive properties could be used as scaffolds for guided tissue engineering in periodontology. In a second approach, the development of chitosan-based nanofibers with anticoagulant properties was conducted. Chitosan was initially chemically modified by sulfonate groups. The synthesis parameters allowed to control the degree of sulfonation of chitosan and its new polyampholyte specific character was observed. The different biological assays carried out have shown that these sulfonic derivatives are non-hemolytic and benefit from anticoagulant properties. Then, sulfonated chitosan-based nanofibres were obtained by electrospinning leading to membranes with antithrombotic properties, make them suitable candidates for the functionalization of vascular stents

The paper presents the results of the preparation of the nanofiber coatings from chitosan biopolymer by electro-spinning. Structure and uniformity distribution of the fibers in the resulting coatings are investigated by a scanning electron microscope JEOL JSM-5610 LV. The optimum concentration of the chitosan solution in the mold, which provide forming nanofibers with fewer defects, was determinated. The obtained data are used for the development of the technology for production of hemostatic and wound-healing dressings for medical purposes in order to organize their production at OJSC "Mineral Wax Plant".

Submitted by Marilene Donadel (marilene.donadel@unioeste.br) on 2018-11-13T20:42:28Z No. of bitstreams: 1 Desiree_Scheidt_2018.pdf: 2702009 bytes, checksum: acf3f21bfb597257a2a34ce95b6f6002 (MD5)
Made available in DSpace on 2018-11-13T20:42:28Z (GMT). No. of bitstreams: 1 Desiree_Scheidt_2018.pdf: 2702009 bytes, checksum: acf3f21bfb597257a2a34ce95b6f6002 (MD5) Previous issue date: 2018-08-27
Fundação Araucária de Apoio ao Desenvolvimento Científico e Tecnológico do Estado do Paraná (FA)
Nanofibers generated using polymers are generally produced by the electrospinning method. It is a simple, economical and versatile technique that uses an electric force to generate ultrafine fibers. Chitosan is a non-toxic, biodegradable, biocompatible polymer obtained from renewable natural sources that attracts the interest of researchers. However, due to the difficulty of electrospinning pure chitosan, it has been tried to ally the poly (ethylene oxide) PEO to the polymeric matrix of chitosan, in order to facilitate the process of obtaining fibers. In this context, the initial objective of this work was to obtain a polymeric blends containing chitosan and PEO capable of generating nanofibers when subjected to the electrospinning process. The poly (ethylene oxide) was excellent as a helper in chitosan spinning, allowing the obtaining of fibers with up to 90% of the same and the average diameter obtained was of 320nm. The process parameters were evaluated and the ones that showed the best result were a concentration of 4% of chitosan and 2% of PEO, applied tension of 18kv and distance between the collector and needle of 20cm. The incorporation of PEO into the polymeric matrix of chitosan proved to be an effective strategy for obtaining nanofibers by the electrophilic process. The study was then carried out for the incorporation of the drug neomycin sulfate into the electrophilic matrix. Membranes in the ratio of 90/10 (v / v) chitosan / 4% PEO / 4% (m / v), as well as membranes in the ratio 80/20 (v / v) chitosan / PEO (4% / 2%) were studied as support for the incorporation of the drug. When the neomycin sulfate was incorporated together with the solution and subjected to electrospinning, the diameter of the fibers obtained were even smaller, with a mean of 258nm. The obtained membranes were subjected to physico-chemical analysis, which proved the miscibility of the polymers chitosan and PEO as well as confirmed the incorporation of the neomycin sulfate to the blend. The antimicrobial activity for the drug and non-drug membranes was investigated against Gram positive and Gram negative bacteria and the registered inhibition halos were larger or near the control. The neomycin sulfate release test indicated that it had a rapid release profile, and with only 120 minutes, much of the drug had already been released from the polymer film. In view of this, the membranes developed in this study suggest to be promising candidates for the application as a biomaterial in wound healing.
Nanofibras poliméricas podem ser produzidas utilizando o método de eletrofiação. Trata-se de uma técnica simples, econômica e versátil que utiliza um potencial elétrico para gerar fibras em escala nanométrica. Dentre os polímeros eletrofiados, pode-se destacar a quitosana, a qual é um polímero atóxico, biodegradável, biocompatível, obtido por meio de fontes naturais renováveis, que vem despertando o interesse de pesquisadores. No entanto, devido à dificuldade de eletrofiação desse material puro, tem-se buscado aliar o poli (óxido de etileno) PEO à matriz polimérica da quitosana, a fim de se facilitar o processo de obtenção de fibras. Nesse contexto, o objetivo inicial deste trabalho foi a obtenção de uma blenda polimérica contento quitosana e PEO capaz de gerar nanofibras quando sujeitas ao processo de eletrofiação. O poli (óxido de etileno) mostrou-se excelente como auxiliador na fiação da quitosana, permitindo a obtenção de fibras com até 90% da mesma e o diâmetro médio obtido foi de 320nm. Os parâmetros de processo foram avaliados e os que mostraram melhor resultado foi uma concentração de 4% (m/v) de quitosana em ácido acético 90% (v/v) e 2% (m/v) de PEO em ácido acético 50% (v/v), tensão aplicada foi de 18kV e distância entre o coletor e agulha de 20cm. A incorporação do PEO à matriz polimérica de quitosana se mostrou, então, uma estratégia eficaz para a obtenção de nanofibras por meio do processo de eletrofiação. Seguiu-se então o estudo para a incorporação do fármaco sulfato de neomicina à matriz eletrofiada, com a finalidade de ampliar a atividade antimicrobiana do filme obtido. Membranas na proporção 90/10 (v/v) de quitosana/PEO 4%/4% (m/v), assim como membranas na proporção 80/20 (v/v) quitosana/PEO 4%/2% (m/v) foram estudadas como suporte para a incorporação do fármaco. Quando o sulfato de neomicina foi incorporado junto a solução e submetido a eletrofiação, o diâmetro das fibras obtidas foram ainda menores, com média de 258nm. As membranas obtidas foram sujeitas a análises físico-químicas, as quais comprovarem a miscibilidade dos polímeros quitosana e PEO assim como confirmaram a incorporação do sulfato de neomicina à blenda. A atividade antimicrobiana para as membranas com fármaco e sem fármaco foi investigada contra bactérias Gram positivas e Gram negativas e os halos de inibição registrados foram maiores ou próximo ao controle, demonstrando uma alta capacidade antimicrobiana. O teste de liberação do sulfato de neomicina indicou que o mesmo apresenta um perfil de liberação rápido, sendo que com apenas 120 minutos grande parte do fármaco já havia se desprendido do filme polimérico. Diante disso, as membranas desenvolvidas nesse estudo sugerem ser promissoras candidatas para a aplicação como um biomaterial na cicatrização de feridas, sendo ainda necessários estudos de viabilidade celular.

Orientador: Nelson Eduardo Durán Caballero
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
Made available in DSpace on 2018-08-26T20:45:34Z (GMT). No. of bitstreams: 1 Ridolfi_DanielaMissiani_D.pdf: 3264748 bytes, checksum: faea0a4fec50e345e79d3072a773bb48 (MD5) Previous issue date: 2014
Resumo: Neste trabalho nanofibras de quitosana/poli (óxido de etileno) (PEO) (5:1) com nanocristais de celulose (NCC) foram produzidas com sucesso por eletrofiação e foi verificado o efeito da adição dos NCC nas propriedades das nanofibras obtidas. Os ensaios de eletrofiação foram realizados com amostras de NCC obtidas por hidrólise ácida. A eletrofiação de soluções de quitosana, sem e com NCC, resultaram na formação de muitas gotas (beads). Portanto, foi necessário adicionar o PEO nas soluções. Embora a adição de PEO tenha favorecido a formação de fibras, as soluções de quitosana/PEO sem NCC geraram também gotas enquanto que as soluções de quitosana/PEO contendo NCC resultaram em fibras uniformes. As soluções de quitosana/PEO com NCC apresentaram maior viscosidade em relação à solução sem NCC, o que pode ter favorecido a formação de fibras uniformes. As soluções de quitosana/PEO contendo 10% (m/m) de NCC produziram fibras mais finas em relação às soluções com 5% (m/m) de NCC provavelmente devido à maior condutividade da solução. Análises termogravimétricas mostraram que os NCC interferem na decomposição do PEO, mas sem prejudicar o desempenho do material. As nanofibras de quitosana/PEO contendo NCC apresentaram menor cristalinidade em relação às nanofibras sem NCC. Resultados de ensaios com células em culturas de fibroblastos 3T3 mostraram que as nanofibras de quitosana/PEO (com 10% de NCC) promoveram a adesão celular e mantiveram a morfologia celular característica o que sugere um potencial dessas nanofibras para aplicações em engenharia de tecidos
Abstract: In this work chitosan/ poly (ethylene oxide) (PEO) (5:1) nanofibers with cellulose nanocrystals (CNC) were successfully produced by the electrospinning technique and the effect of the addition of CNC on the nanofibers properties was evaluated. The electrospinning assays were performed with samples of CNC obtained by acid hydrolysis. The electrospinning of chitosan solutions, with and without CNC, resulted in the formation of many drops (beads). Therefore, it was necessary to add PEO on solutions. Although the PEO addition has favored the fiber formation, the chitosan/PEO solutions without CNC showed beads while chitosan/PEO solutions with CNC resulted in uniform fibers. The chitosan/PEO solutions with CNC showed higher viscosity compared to the solution without CNC, which may have favored the formation of uniform fibers. Solutions of chitosan/PEO containing 10% (w/w) of CNC produced thinner fibers compared to solutions containing 5% (w/w) of CNC probably due the higher solution conductivity. Thermogravimetric analysis (TGA) showed that the CNC has an effect on the PEO decomposition, however, it does not impair the performance of the material. The chitosan/PEO nanofibers with CNC showed lower crystallinity compared the nanofibers without CNC. Results from cell assay in cultures of 3T3 fibroblasts showed that the chitosana/PEO nanofibers (with 10% of CNC) promoted cell attachment and maintained the characteristic cell morphology which suggests potential applications of these nanofibers in cell tissue engineering
Doutorado
Físico-Química
Doutora em Ciências

Orientador: Alexandre Luiz Souto Borges
Coorientador: Artur José Monteiro Valente
Banca: Bruno Vinícius Manzolli Rodrigues
Banca: Fernanda Alves Feitosa
Banca: Lafayette Nogueira Júnior
Banca: Eduardo Shigueyuki Uemura
Resumo: Os atuais avanços no desenvolvimento de biomateriais caminham para 2 áreas promissoras: a de regeneração tecidual e a de entrega controlada de fármacos. Assim, o presente estudo objetivou a síntese e caracterização de diferentes matrizes (fibras e hidrogel) à base de quitosana, a fim de se obter materiais biomiméticos para atuação em ambas áreas. Para regeneração, delineou-se a síntese de um arcabouço de fibras de quitosana com e sem cristais de nanohidroxiapatita onde, para isso, foram eletrofiadas soluções de quitosana (Ch) e de quitosana com nanohidroxiapatita (ChHa). Os espécimes de Ch apresentaram maior homogeneidade e maior diâmetro médio de fibras (690 ± 102 nm) que ChHa (358 ± 49 nm). No teste de viabilidade celular e na atividade da fosfatase alcalina não houve diferença estatística entre os grupos experimentais (Ch e ChHa), porém ambos diferiram do grupo controle (p < 0,001). Para o âmbito de liberação de fármacos, sintetizou-se, pela técnica de emulsão, dois tipos de hidrogéis: o primeiro, uma mistura da fase aquosa da solução de Ch (1 mL) e da solução de DNA (1 mL) (1:1) e o segundo, mistura da fase aquosa da solução de Ch (1 mL) e solução de Pectina (1 mL) (1:1). Ambas misturas foram realizadas em álcool benzílico (5 mL) com instrumento de dispersão de alto desempenho (31-34000 rpm min-1 por 5 min). Após a obtenção dos géis, 20mg de cada grupo foram imersos em uma solução aquosa de Própolis Verde (PV), na concentração de 70 μg/mL por 2 h e a cinética de liberação... (Resumo completo, clicar acesso eletrônico abaixo)
Current advances in biomaterial development are moving to 2 promising areas: tissue regeneration and controlled drug delivery. Thus, the present study aimed the synthesis and characterization of different matrices (fibers and hydrogel) based on chitosan, in order to obtain biomimetic materials for performance in both areas. For regeneration, the synthesis of a scaffold of chitosan fibers with and without nanohydroxyapatite crystals was delineated, where chitosan (Ch) and chitosan with hydroxyapatite (ChHa) solutions were electrospun. Ch specimens presented higher homogeneity and larger mean fiber diameter (690±102nm) than ChHa (358 ± 49nm). In the cell viability test and alkaline phosphatase activity there was no statistical difference between the experimental groups. (Ch and ChHa), but both differed from the control group (p < 0,001). For the drug release scope, two types of hydrogels were synthesized by the emulsion technique: the first, a mixture of the aqueous phase of Ch solution (1 mL) and DNA solution (1 mL) (1:1) and the second, mixture of the aqueous phase of the Ch solution (1mL) and Pectin solution (1 mL) (1:1). Both mixtures were performed in benzyl alcohol (5 mL) with high performance dispersion instrument (31-34000 rpm min-1 for 5 min). After obtaining the gels, 20mg from each group were immersed in an aqueous solution of Propolis Green (PV), at a concentration of 70 µg/mL for 2 h and the release kinetics of PV were analyzed at 25 and 37oC in water and artificial saliva. The obtained specimens were lyophilized and then physically-chemically characterized. The presence of pectin and DNA was confirmed by FTIR. PV sorption induced a significant modification of the gel surface. A phase separation was found between chitosan and DNA. Encapsulation efficiency did not change significantly between 25 and 37oC. The release kinetics in water or saliva presented a two-step mechanism. And the biological results...
Doutor

Schwann cell-seeded guidance channels have been exploited to bridge and guide axonal re-growth across gaps in lesioned nerves. Mis-orientation of Schwann cells in the channels can however distort axonal growth within the lesion. We therefore propose to orient the growth of Schwann cells on aligned nanofibers such that axonal growth can be guided along the designated direction towards the target. Chitosan was the choice scaffold material given its biocompatibility and the tunable susceptibility to biodegradation. To be suitable for electrospinning, chitosan was dissolved in trifluoroacetic acid/methylene chloride solution. By replacing the grounded plate collector of the conventional electrospinning setup with parallel collector plates placed 1.6 cm apart, the positively charged chitosan fibersbecame alternately attracted to the parallel plates and ended up uniaxially aligned as fiber suspension across the plates. Stability of the chitosan fibers in aqueous, physiological environment was achieved with the use of sodium carbonate to neutralize residual acidity in the chitosan fiber preparation. Schwann cells seeded onto these stabilized aligned chitosan nanofibers aligned uniaxially with the chitosan nanofibers. In addition, by seeding dissociated cells of dorsal root ganglia (DRG, E14/15 rats) onto the uniaxially aligned nanofibers, both neurons and Schwann cells were aligned with uniaxial arrangement of nanofibers, and the Schwann cells showed myelination ofthe axons. A model of the chitosan nerve conduit was constructed with a core nanofiberbundle, and seeding of Schwann cells. Thesein vitro results provide proof-of-principle for pursuing improvement in post-traumatic recovery from nerve injury with use of uniaxially aligned chitosan nanofibers in Schwann cell-seeded nerve guidance channels.
published_or_final_version
Biochemistry
Master
Master of Philosophy

Orientadores: Lucia Helena Innocentini Mei, Marcos Akira D'Ávila
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2018-08-20T02:05:21Z (GMT). No. of bitstreams: 1 Bizarria_MariaTrindadeMarques_D.pdf: 4483205 bytes, checksum: 44e9caae2b1e4e2bd5569681573ba911 (MD5) Previous issue date: 2012
Resumo: A obtenção de nanofibras de polímeros biocompatíveis, baseadas em quitosana, bem como a montagem de equipamento capaz de produzi-las, foi o principal objeto deste trabalho. Com este propósito, buscou-se de início reunir os dispositivos eletrônicos e mecânicos indispensáveis à prática da eletrofiação e um equipamento básico, de baixo custo, mas funcional foi construído. Com base na literatura, o ácido acético glacial a 90% em água deionizada foi o solvente utilizado para preparo das soluções de quitosana. Para viabilizar o processo da produção das nanofibras pela técnica da eletrofiação utilizaram-se blendas de soluções de quitosana com soluções de outros polímeros biocompatíveis em vez de soluções de quitosana pura. Assim, blendas de soluções de quitosana com soluções aquosas do poli(óxido de etileno) - PEO , bem como, com soluções aquosas de Poli(álcool vinílico) - PVA, em diversas proporções, foram eletrofiadas. O Poli(óxido de etileno) mostrou superior desempenho, como auxiliar na fiação da quitosana, permitindo a obtenção de fibras com até 80% de quitosana, e com diâmetros inferiores àqueles obtidos com as blendas de soluções de quitosana/PVA. A adição de um eletrólito (NaCl) às soluções blendas de quitosana/PEO proporcionou um processo fácil ininterrupto, sendo assim, buscou-se um melhor entendimento sobre as propriedades das soluções da quitosana e do PEO que norteiam comportamentos mais ou menos favoráveis ao processo da eletrofiação, caracterizando-se essas soluções através de estudos de viscosidade, de medidas de tensão superficial e de condutividade elétrica. A morfologia das fibras obtidas foi caracterizada por microscopia eletrônica de varredura (MEV) e, as propriedades térmicas, das membranas nanoestruturadas resultantes da eletrofiação das soluções de Quitosana/PEO, foram avaliadas por análise termogravimétrica (TGA) e calorimetria diferencial exploratória (DSC). A biocompatibilidade das membranas com teor de quitosana mais elevado (80% quitosana/20% PEO) foi avaliada através de testes de citotoxicidade in vitro, biocompatibilidade in vivo e adesão e crescimento celular in vitro. Adicionalmente, foram conduzidos experimentos visando avaliar o desempenho destas mesmas membranas como carreadoras de fármacos sendo que, a incorporação de nanopartículas de prata (AgNPs), bem como de digluconato de clorexidina apresentaram resultados promissores
Abstract: The development of biocompatible polymer nanofibers based on chitosan and the design and assembly of equipment capable of producing them were the main objectives of this work. For this purpose, the basic electronic and mechanical devices were obtained and a low-cost functional electrospinning setup was built. Based on the literature, glacial acetic acid with concentration of 90% in deionized water was the solvent used to prepare the chitosan solutions. In order to enable the nanofiber production by electrospinning, blends of chitosan solutions with other biocompatible polymers were used instead of pure chitosan solutions. Thus, blends of chitosan solutions with aqueous solutions of poly (ethylene oxide) PEO as well as with aqueous solutions of poly (vinyl alcohol) PVA, in various proportions, were electrospun. The PEO presented superior performance as an aid to obtain chitosan fibers, resulting in fibers with up to 80% of chitosan, and with smaller diameters than those obtained with solutions of blends of chitosan / PVA. The addition of an electrolyte (NaCl) to the chitosan/PEO solution blends has provided an easy and uninterrupted process. Thus, to obtain a better understanding about the properties of chitosan and PEO solutions that lead to more or less favorable behaviors to the electrospinning process, these solutions were characterized by performing viscosity studies and measurements of surface tension and electrical conductivity. The morphology of the fibers was evaluated by scanning electron microscopy (SEM) and the thermal properties of nanostructured membranes resulting from electrospinning of chitosan/PEO solutions were evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC).The biocompatibility of the higher-content-chitosan membranes (80%chitosan /20% PEO) was evaluated by tests of in vitro cytotoxicity, in vivo biocompatibility and in vitro cell adhesion and growth. In addition, experiments were conducted to evaluate the performance of the same membrane as a carrier of drugs. In this way, the incorporation of silver nanoparticles (AgNPs) and chlorhexidine digluconate showed promising results
Doutorado
Ciencia e Tecnologia de Materiais
Doutor em Engenharia Química

Visando o desenvolvimento de materiais biodegradáveis para embalagens, blendas de amido/quitosana estruturadas com nanopartículas de montmorilonita (MMT) ou nanofibras de bambu (NFBs) em concentrações de (0,0; 0,5 e 1,0) g de NPs/100 g de polímero foram obtidas pelas técnicas de casting e extrusão. Os bionanocompósitos obtidos das duas técnicas foram caracterizados, bem como foi avaliada a influência da dispersão das nanopartículas sobre as principais propriedades físico-químicas dos bionanocompósitos. Para os filmes produzidos de blendas de amido/quitosana por casting, foram avaliadas as proporções de (5/0; 3,75/0,25; 2,5/2,5; 1,25/0,75 e 0/1) g/100 g base polímero, e a adição dos reforçadores na solução filmogênica. Observou-se uma dispersão assim como uma intercalação satisfatória da MMT nos bionanocompósitos, confirmadas pelas mudanças da cristalinidade devido ao deslocamento do pico característico de 7,2 º para 5,2 º; e os filmes estruturados com NFBs apresentaram variações nas frequências vibracionais dos arranjos moleculares indicando a formação de ligações fortes entre as blendas e os reforçadores. A partir da extrusão da mistura de homo pellets e pellets masterbatch, das blendas de amido/quitosana nas proporções de (100/0; 75/25 e 50/50) g/100 g, foram obtidos compósitos em processo contínuo os quais exibiram propriedades qualitativas satisfatórias assim como mudanças de cristalinidade e interações moleculares. Em relação às propriedades mecânicas, os bionanocompósitos apresentaram um aumento da resposta à tensão assim como da elongação e módulo de elasticidade em relação às concentrações dos reforçadores em cada umas blendas avaliadas. Por outro lado, tanto a formação das blendas como as interações dos reforçadores modificaram significativamente a rede tridimensional dos filmes em relação à taxa de transferência de vapor de água, obtendo-se valores de (155 e 139) g m-2 d-1 para os compósitos obtidos da blenda amido/quitosana 100/0 estruturados com (0,5 e 1,0) g MMT/100 g, respectivamente. Os valores de PVA obtidos são inferiores aos reportados por produtos comerciais como o (PBS) Bionolle™ (330 g m-2 d-1) e (PBAT) Ecoflex® (272 g m-2 d-1). Neste trabalho foi possível desenvolver um material promissor com características diferenciadas e alta aplicabilidade no setor de embalagens biodegradáveis para uso industrial.
Aiming at the development of biodegradable packaging materials, starch/chitosan blends structured with montmorillonite nanoparticles (MMT) or bamboo nanofibers (NFBs) at concentrations of (0.0,0.5 and 1.0) g NPs/100 g of polymer were obtained by the casting and extrusion techniques. The obtained bio-nanocomposites were characterized, as well as, how the dispersion of nanoparticles influenced the main physicochemical properties of the films. For the films from starch/chitosan blends produced by the casting method, the proportions of (5/0, 3.75/0.25, 2.5/2.5, 1.25/0.75 and 0/1) g/100 g based on polymer, were tested and the introducing of the reinforcers into filmogenic solution were evaluated. Satisfactory dispersion and exfoliation of MMT in bio-nanocomposites were confirmed by changes of crystallinity due to displacement of the characteristic peak from 7.2 ° to 5.2 °. In the same way, films structured with NFBs showed variations of the vibrational frequencies of the molecular arrangements indicating strong bonds between the polymer blends and the reinforcers. By the extrusion from the mixture of homo pellets and masterbatch pellets, from starch/chitosan blends at proportions of (100/0, 75/25 and 50/50) g/100 g, the obtained films have exhibited changes of the crystallinity and the molecular interactions. In relation to mechanical properties, the films presented increase of the tension response as well as the elongation and modulus of elasticity in relation to the reinforcer concentration in each evaluated blend. On the other hand, the formation of polymer blends and the interactions of reinforcers with the matrix changed significantly the three-dimensional network and consequently the water vapor transmission (WVT). Films produced from starch/chitosan 100/0, nanostructured with (0.5 and 1.0) g MMT/100 g, exhibited lower values of WVT 155 e 139) gm-2 d -1, respectively, when compared to commercial products such as Bionolle ™ (PBS) 330 g m-2 d-1) and (PBAT) Ecoflex® (272 g m-2 d-1). In this work, it was possible to develop a promising material with desired characteristics in the biodegradable packaging sector with wide application in the industry.

Thesis (MSc)--Stellenbosch University, 2016.
ENGLISH ABSTRACT: Tuberculosis (TB) is one of the world’s deadliest diseases, with one third of the population being infected by it. The diagnosis of active tuberculosis entails finding and identifying Mycobacterium tuberculosis (Mtb), the causative pathogen in a specimen of bodily fluid from the patient. Multiple samples will improve the diagnostic yield and specimen volumes should therefore be as large as possible, which is often challenging for patients and especially younger children. Alternatively, a smaller volume could be required if there was a manner in which to concentrate the bacteria within a specimen, through use of a substrate which has an affinity for the pathogenic species. Polymers having intrinsic cellular activity are of interest as such substrates, one such being the natural polysaccharide, chitosan. In this thesis, a variety of modified chitosan derivatives were prepared as potential Mtb-capturing substrates. This was achieved by modifying chitosan with a variety of moieties, selected based on possible interactions with the Mtb cell wall, to render various quaternary ammonium salts of the polymer chitosan. The quaternized chitosan derivatives were then used to synthesize nano-substrates having an affinity for Mtb. Polymer coated superparamagnetic magnetite nanoparticles (SPMNs) were synthesized via an in situ co-precipitation technique, in which modified chitosan is able to chelate with the metal core. Polymer nanofibers were also electrospun via the electrospinning technique. The prepared derivative, N-trimethylammonium chitosan chloride (TMC), was electrospun into nanofibers by blending with suitable non-ionogenic polymers, namely polyvinyl alcohol (PVA), polyethylene oxide (PEO), polyvinyl pyrrolidone (PVP) and polyacrylamide (PAM), required to facilitate nanofiber formation. Affinity studies were conducted between the modified chitosan nano-substrates and the bacillus Calmette-Guérin (BCG) strain of Mycobacterium bovis, the attenuated Mtb-mimic bacteria, for evaluation as mycobacterium capturing substrates. The successful capture of BCG onto the surfaces of the various modified chitosan nanofibers and modified chitosan coated superparamagnetic nanoparticles was confirmed by fluorescence microscopy (FM), light microscopy (LM), transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM). Analysis of the FM, TEM and FE-SEM images indicated that the chitosan coated nanoparticles functionalized with a C12 aliphatic quaternary ammonium moiety (CS-qC12), captured the most BCG through a combination of ionic and hydrophobic interaction. TMC blended with PVA, to produce nanofibers crosslinked with genipin, were found to have the strongest interaction with BCG of the nanofibrous mats tested. These findings were corroborated by water contact angle measurements, which established that PVA was the least hydrophilic of the non-ionogenic polymers and had hydrogen bond donating groups only, factors influencing the cellular adhesive properties of affinity substrates.
AFRIKAANSE OPSOMMING: Tuberkulose (TB) is een van die wêreld se mees dodelikste siektes, met ‘n derde van die bevolking wat geïnfekteer is daarmee. Ten einde aktiewe TB te diagnoseer moet Mycobacterium tuberculosis (Mtb), die voorsakende patogeen in ʼn monster van die pasiënt se liggaamlike vloeistof, gevind en ïdentifiseer word. Veelvuldige monsters sal die diagnotiese opbrengs verhoog en monster volumes moet dus so groot as moontlik wees wat dikwels ʼn uitdaging vir pasiënte en veral jonger kinders kan bied. Alternatiewelik kan ʼn kleiner monster van die pasiënt vereis word indien daar ʼn manier was om die bakterieë in ʼn monster te konsentreer deur die gebruik van ʼn substraat wat ʼn affiniteit toon vir die patogeniese spesie. Polimere met ʼn intrinsieke sellulêre aktiwiteit, wek belangstelling as sodanige substraat, een synde die natuurlike polisakkaried, chitosan. In hierdie tesis is ʼn verskeidenheid gemodifiseerde chitosan afgeleides voorberei as potensiële Mtb-vaslegging substrate. Dit is gedoen deur chitosan te modifiseer met ʼn verskeidenheid funksionele groepe, gekies op grond van moontlike interaksies met die Mtb selwand, ten einde ʼn verskeidenheid kwaternêre ammonium soute van die chitosan polimeer te bekom. Die kwaternêre chitosan afgeleides is gevolglik gebruik om nano-substrate te sintetiseer wat ʼn affiniteit toon vir Mtb. Polimeer bedekte superparamagnetiese magnetiet nanopartikels (SPMNs) is gesintetiseer via ʼn in situ mede-neerslag metode, waarvolgens die gemodifiseerde chitosan polimere in staat is om met die metaal kern te chelaat. Polimeer nanovesels is ook geëlektrospin deur die elektrospin tegniek te gebruik. Die voorbereide afgeleide N-trimetielammonium chitosan chloried (TMC) is tot nanovesels geëlektrospin deur vermenging met geskikte nie-ionogeniese polimere, naamlik poliviniel-alkohol (PVA), polietilene-oksied (PEO), poliviniel-pirrolidoon (PVP) en poliakrielamied (PAM), wat vereis word ten einde nanovesels te produseer. Affiniteit studies is uitgevoer tussen die gemodifiseerde chitosan nano-substrate en die bacillus Calmette-Guérin (BCG) stam van Mycobacterium bovis, die verswakte Mtb-mimiek bakterieë vir evaluering as mycobakterium-vaslegging substrate. Die suksesvolle vasvang van BCG op die oppervlaktes van die verskillende gemodifiseerde chitosan nanovesels en gemodifiseerde chitosan bedekte SPMNs is bevestig deur fluoressensie mikroskopie (FM), lig mikroskopie (LM), transmissie elektron mikroskopie (TEM) en veld-emissie-skandering elektron mikroskopie (FE-SEM). Analise van die FM, TEM en FE-SEM beelde het getoon dat die chitosan bedekte nanopartikels met byvoeging van ʼn C12 alifatiese kwaternêre ammonium groep, die meeste BCG vasgevang het deur ʼn kombinasie van ioniese en hidrofobiese interaksie. TMC vermeng met PVA om nanovesels te vorm, gekruisbind met genipin, is gevind om die sterkste interaksie met BCG te toon. Hierdie bevindings is bevestig deur water-kontak-hoek-metings, wat getoon het dat PVA die minste hidrofilies van die nie-ionogeniese polimere was en slegs waterstof-binding skenkings groepe het, alles faktore wat die sellulêre bindingskwaliteite van affiniteit-substrate sal beïnvloed.

Electrospinning is a technique, which can be used to produce nanofibrous materials by introducing electrostatic fields into the polymer solution. Due to their intrinsic properties, such as small fiber diameter, small pore size and large surface area, nanofibres are suitable for use in a variety of applications including wound dressing, filtration, composites and tissue engineering. The study demonstrates the successful and optimised production of Poly(ethylene oxide) (PEO) and chitosan nanofibres by electrospinning. The biocidal effects of chitosan, chitosan-silver nanofibres and silver nanoparticles were successfully investigated. To set up a functional electrospinning apparatus, the PEO solution parameters (concentration, molecular weight, solvent, and addition of polyelectrolyte) and applied potential voltage on the structural morphology and diameter of PEO nanofibres were studied. At lower PEO concentrations, the fibres had morphology with a large variation in fibre diameter, whereas at the higher concentrations, the nanofibres exhibited ordinary morphology with uniform but larger fibre diameters. Higher molecular weight showed larger average diameters when compared to that obtained with the same polymer but of a lower molecular weight. The addition of polyelectrolyte to the polymer solution had an influence on the structural morphology of the PEO. Flow simulation studies of an electrically charged polymer solution showed that an increase in the flow rate was associated with an increase in poly(allylamine hydrochloride) (PAH) concentration for the low molecular weight polymer, the shape and size of the Taylor cone increasing with an increase in PAH concentration for the low molecular weight polymer. During optimization of the PEO nanofibres, based on statistical modelling and using the Box and Behnken factorial design, the interaction effect between PAH concentration and the tip-to-collector distance played the most significant role in obtaining uniform diameter of nanofibres, followed by the interaction between the tip-to-collector distance and the applied voltage and lastly by the applied voltage. The production and optimization of chitosan nanofibres indicated that the interactions between electric field strength and the ratio of trifluoroacetic acid (TFA) and dichloromethane (DCM), TFA/DCM solvents as well as between electric field strength and chitosan concentration had the most significant effect, followed by the concentration of chitosan in terms of producing nanofibres with uniform diameters. Chitosan and chitosan-silver nanofibres could be successfully electrospun by controlling the solution properties, such as surface tension and electrical conductivity with the silver nanoparticles in the chitosan solutions affecting the electrospinnability. The silver nanoparticles in the chitosan solution modified the morphological characteristics of the electrospun nanofibres, while the conductivity and the surface tension were elevated. The fibre diameter of the chitosan and chitosan-silver nanoparticles decreased with an increase in the silver content. The electrospun chitosan nanofibres had a smooth surface and round shape as compared to the silver-chitosan nanofibres with a distorted morphology. The chitosan and chitosan-silver nanofibres as well as the silver nanoparticles exhibited antimicrobial or inhibition activity against S. aureus than against E. coli. S. aureus bacterial culture showed good cell adhesion and spreading inwards into the chitosan nanofibrous membrane. The chitosan-silver nanofibres exhibited a greater minimum inhibitory concentration (MIC), followed by silver nanoparticles and then chitosan nanofibres; suggesting a synergistic effect between the chitosan and silver nanoparticles.

Orientador: Prof. Dr. Wendel Andrade Alves
Coorientadora: Dra. Irina Marinho Factori
Tese (doutorado) - Universidade Federal do ABC, Programa de Pós-Graduação em Nanociências e Materiais Avançados, Santo André, 2018.
A técnica de eletrofiação é um método versátil para fabricar polímeros em fibras contínuas com diâmetros que variam alguns nanômetros. A alta razão superfície/volume, as dimensões nanométricas, que possibilitam obter ótimo desempenho com pouca quantidade de nanomaterial, e a alta porosidade, tornam as nanofibras eletrofiadas sistemas muito atraentes para aplicações como filtração, engenharia de tecidos, fabricação de roupas de proteção, esteiras têxteis não tecidas, feixes fibrosos orientados, até andaimes estruturados tridimensionais. Nos últimos anos, muitas estratégias sintéticas foram desenvolvidas para obter nanomateriais poliméricos unidimensionais (1D). Em particular, a poliamida 6 foi extensivamente investigada devido às suas boas propriedades mecânicas e físicas. Além disso, as suas propriedades funcionais podem ser moduladas pela adição de polieletrólitos como a quitosana. A quitosana é um polissacarídeo com excelente biocompatibilidade e admirável biodegradabilidade com atividades biológicas versáteis, como atividade antimicrobiana, baixa imunogenicidade e baixa toxicidade. Neste trabalho, é apresentada a proposta de um material, preparado por eletrofiação, composto por poliamida 6 (PA6) e quitosana (Q) de baixa massa molar. O material foi avaliado à temperatura ambiente nas proporções 100/0; 90/10; 80/20; 70/30 e 60/40 de PA6/Q. Devido às suas características intrínsecas, essas nanofibras poliméricas são atrativas para aplicações biomédicas e biotecnológicas, tais como nanocompósitos, implantes médicos e biossensores. As propriedades morfológicas e estruturais das nanofibras foram investigadas por técnicas de análise térmica (DSC, DTG e TGA), espectroscópicas (FTIR) e microscópicas (MEV). Os resultados obtidos mostraram que as nanofibras eletrofiadas apresentam uma diminuição do grau de cristalinidade com a adição da quitosana (~27 para ~16%). Revelou ainda que o processo de eletrofiação promove uma redução da cristalinidade na PA6 (~45 para ~27%). Além disso, a adição da quitosana diminuiu a temperatura de degradação da PA6 (437 ¿ 420°C), mas proporcionou a obtenção de nanofibras de diâmetro menor (~100 - ~30 nm). A intenção futura deste trabalho é aplicar essas nanofibras no campo dos biossensores, como substrato para ancoragem. O uso do dispositivo de cobre de duas hastes, como coletor no processo de eletrofiação, permitiu obter nanofibras de PA6 sem e com adição de diferentes teores de quitosana.
The electrospinning technique is a versatile method to manufacturing polymers into continuous fibers with diameters ranging a few nanometers. The high surface/volume ratio, the nanometric dimensions, that allow to obtain optimum performance with little amount of nano-material and the high porosity, make electronanofibers as very attractive systems for applications such as filtration, tissue engineering, e others, non-woven textile mats, oriented fibrous bundles, even three-dimensional structured andaimes. Over the last few years, many synthetic strategies have been developed to obtain one-dimensional polymer nanomaterials (1D). In particular, polyamide 6 has been extensively investigated cause of its good mechanical and physical properties. Their properties can be modulated by adding polyelectrolytes such as chitosan, that is a polysaccharide having excellent biocompatibility and admirable biodegradability with versatile biological activities such as antimicrobial activity, low immunogenicity and low toxicity. In this work, it is be results showed that the electrophilic blankets showed a decrease in the degree of crystallinity with the addition of chitosan (27 to 16%). It also revealed that the electrochemical process promotes a reduction of crystallinity in PA6 (45 to 27%). In addition, addition of chitosan lowered the degradation temperature of PA6 (437-420 ° C), but yielded nanofibers of smaller diameter (100 - 30 nm). The future intention of this work is to apply these nanofibers in the biosensors field, as substrate for anchorage. The use of the two-presented the proposal of a material, prepared by electro-spinning, composed of polyamide 6 (PA6) and chitosan (Q) with low molar mass. The material was evaluated at room temperature in proportions 100/0; 90/10; 80/20; 70/30 and 60/40 PA6 /Due to their intrinsic features, these polymeric nanofibers are attractive for biomedical and biotechnological applications such nanocomposites, medical implants and biosensors. The morphological and structural properties of nanofibers were investigated by thermal (DSC, DTG and TGA), spectroscopic (FTIR) and microscopic (SEM) techniques. The results showed that the electrophilic blankets showed a decrease in the degree of crystallinity with the addition of chitosan (27 to 16%). It also revealed that the electrochemical process promotes a reduction of crystallinity in PA6 (45 to 27%). In addition, addition of chitosan lowered the degradation temperature of PA6 (437-420 ° C), but yielded nanofibers of smaller diameter (100 - 30 nm). The future intention of this work is to apply these nanofibers in the biosensors field, as substrate for anchorage. The use of the two-rod copper device, as a collector in the electro-spinning process, allowed to obtain PA6 blankets without and with the addition of different contents of chitosan.

Submitted by Tabata Prado Sato (tatapsique@gmail.com) on 2016-01-28T12:55:14Z No. of bitstreams: 1 Dissertação FINAL - 21.01.16 final.pdf: 3278095 bytes, checksum: 2ce6cc39a4cc3a95d0e54b5efc6f2ecf (MD5)
Rejected by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br), reason: Solicitamos que realize uma nova submissão seguindo as orientações abaixo: No campo “Versão a ser disponibilizada online imediatamente” foi informado que seria disponibilizado o texto completo porém no campo “Data para a disponibilização do texto completo” foi informado que o texto completo deverá ser disponibilizado apenas 6 meses após a defesa. Caso opte pela disponibilização do texto completo apenas 6 meses após a defesa selecione no campo “Versão a ser disponibilizada online imediatamente” a opção “Texto parcial”. Esta opção é utilizada caso você tenha planos de publicar seu trabalho em periódicos científicos ou em formato de livro, por exemplo e fará com que apenas as páginas pré-textuais, introdução, considerações e referências sejam disponibilizadas. Se optar por disponibilizar o texto completo de seu trabalho imediatamente selecione no campo “Data para a disponibilização do texto completo” a opção “Não se aplica (texto completo)”. Isso fará com que seu trabalho seja disponibilizado na íntegra no Repositório Institucional UNESP. Por favor, corrija esta informação realizando uma nova submissão. Agradecemos a compreensão. on 2016-01-29T18:28:27Z (GMT)
Submitted by Tabata Prado Sato (tatapsique@gmail.com) on 2016-01-29T19:11:06Z No. of bitstreams: 1 Dissertação FINAL - 21.01.16 final.pdf: 3278095 bytes, checksum: 2ce6cc39a4cc3a95d0e54b5efc6f2ecf (MD5)
Approved for entry into archive by Sandra Manzano de Almeida (smanzano@marilia.unesp.br) on 2016-02-01T17:43:29Z (GMT) No. of bitstreams: 1 sato_tp_me_sjc.pdf: 3278095 bytes, checksum: 2ce6cc39a4cc3a95d0e54b5efc6f2ecf (MD5)
Made available in DSpace on 2016-02-01T17:43:29Z (GMT). No. of bitstreams: 1 sato_tp_me_sjc.pdf: 3278095 bytes, checksum: 2ce6cc39a4cc3a95d0e54b5efc6f2ecf (MD5) Previous issue date: 2015-12-11
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
A eletrofiação é um método para a síntese de fibras poliméricas. Neste sentido, a quitosana é um polímero que por meio deste processo origina biomateriais com boas propriedades biológicas. Já a hidroxiapatita é a principal de reserva de cálcio dos vertebrados. Assim, o presente estudo fabricou mantas de nanofibras a partir de solução de quitosana pura 7% (m/v)(Ch) e de solução de quitosana com adição de cristais de nanohidroxiapatita 0,5% (m/v)(ChHa), na tentativa de unir, sob diferentes parâmetros de eletrofiação (distância, tensão elétrica e fluxo da solução), as propriedades do biopolímero e do complexo de fosfato de cálcio. Ambas soluções foram eletrofiadas e, as mantas obtidas, caracterizadas de acordo com a morfologia (diâmetro médio das fibras), topografia superficial (perfilometria e AFM) e características físicas, químicas, estruturais e térmicas (EDS, FTIR, DRX, ângulo de contato, taxa de degradação, termogravimetria). As amostras Ch, quanto à análise morfológica, apresentaram maior diâmetro de fibras (690,3±102,5nm) em relação às ChHa (358,7±49,2nm) e quanto à topografia, Ch mostrou maior homogeneidade, lisura superficial do que ChHa. O EDS foi capaz de identificar presença de Cálcio nas amostras de ChHa. A partir do FTIR, verificou-se bandas caracteríscas de formação de sal de TFA, respaldando a instabilidade de todas as amostras em meio aquoso, sofrendo imediata dissolução sob os testes de molhabilidade e taxa de degradação. As análises térmicas mostraram que, tanto em Ch como em ChHa, três principais estágios de degradação, sendo a primeira, representação de uma grande perda de água.
The electrospinning is a method used to synthesize polymeric fibers. Chitosan polymer was the one used by this process that originates a biomaterial with good biological properties. The hydroxyapatite is a important calcium reserve of vertebrates. The synthesize process to create nanofibers were made using pure chitosan solution 7% (w/v) (Ch) and chitosan solution added with nanohydroxyapatite (0,5%, w/v) (ChHa), as an attempt to unite, under different electrospinning parameters (distance, electric tension and flow rate), the properties of the biopolymer and calcium phosphate complex. Both solutions were electrospun and the specimens obtained were characterized according to the superficial morphology (mean diameter) topography (profilometry and atomic force microscopy) and physico-chemical characteristics (EDS, FTIR, DRX, contact angle and thermogravimetry). The Ch samples showed from the morphology analysis, a higher mean diameter (690,3±102,5nm) in comparison to ChHa (358,7±49,2nm) and the topograpghy analysis indicated a greater homogeneity and surface smoothness. The EDS was able to identify the presence of calcium in samples of ChHa. From the FTIR, it was verified characteristic peaks of TFA salt formation, which explains the instability of all samples in aqueous solution, with immediate dissolution under the contact angle and degradation rates tests. The thermal analysis presented three main stages of degradation in Ch and ChHa nanofibers with a higher water loss.

O emprego de polímeros naturais na preparação de filmes poliméricos usados na liberação de espécies bioativas tem sido proposto para controlar, a partir das propriedades da matriz polimérica, a cinética de liberação das espécies devido a difusão na matriz e biodegradação desta depois de contato com o meio. Neste trabalho, filmes de quitosana modificados com nanofibras de celulose (NFC) foram preparados para incorporação de glifosato e o estudo das propriedades físico-químicas deste sistema. Os filmes e os nanocompósitos são semicristalinos e estáveis a temperatura ambiente. Os ensaios de transporte de água, permeação ao vapor de água e inchamento em água mostram que as NFC oferecem efeito de barreira, pois a permeação diminui com o aumento da porcentagem de NFC, sendo este efeito benéfico no controle da liberação de espécies bioativas. O glifosato foi eficientemente incorporada aos filmes de NFC, quitosana e nanocompósitos. A presença do glifosato foi observada nos espectros na região do infravermelho, sendo mais evidente nos filmes de NFC e nos compósitos com maior concentração de NFC. Este aspecto indica maior interação entre a quitosana e o glifosato com melhor dispersão deste na matriz de quitosana. O trabalho desenvolvido é promissor, pois possibilitará o desenvolvimento de sistemas para liberação controlada do herbicida mais utilizado comercialmente usando matrizes poliméricas de origem natural.
The use of natural polymers in the preparation of polymer films with the purpose of releasing bioactive species has been proposed to control, through its matrix properties, the kinetics release of the species due to diffusion on its matrix and further biodegradation after contact with the medium. In this work, chitosan films modified with cellulose nanofibers (CNF) were prepared for incorporation of glyphosate and used to the study of physicochemical system properties. The films and nanocomposites showed up semi-crystalline and stable at room temperature. The water transport, steam permeation and water swelling tests have evidenced that CNFs offer a barrier effect, since the permeation decreases with increasing percentage of CNF, providing a beneficial effect in controlling the release of bioactive species. Glyphosate was efficiently incorporated into CNF films, chitosan and nanocomposites. The presence of glyphosate was observed in the infrared spectrum, being more evident and clear in CNF films and composites with higher CNF concentration. This aspect indicates a great interaction between chitosan and glyphosate and its excellent dispersion in the chitosan matrix. This is a promising investigation, as it will allow the development of systems for controlled release of the most commercially used herbicide, through the use of polymer matrices of natural origin.
Dissertação (Mestrado)

Submitted by Aelson Maciera (aelsoncm@terra.com.br) on 2017-03-22T19:16:28Z No. of bitstreams: 1 DissTTB.pdf: 2398693 bytes, checksum: 0a0148927746ba0af71705e6c51cb65e (MD5)
Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-03-22T19:21:20Z (GMT) No. of bitstreams: 1 DissTTB.pdf: 2398693 bytes, checksum: 0a0148927746ba0af71705e6c51cb65e (MD5)
Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-03-22T19:21:41Z (GMT) No. of bitstreams: 1 DissTTB.pdf: 2398693 bytes, checksum: 0a0148927746ba0af71705e6c51cb65e (MD5)
Made available in DSpace on 2017-03-22T19:26:28Z (GMT). No. of bitstreams: 1 DissTTB.pdf: 2398693 bytes, checksum: 0a0148927746ba0af71705e6c51cb65e (MD5) Previous issue date: 2016-02-26
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA)
The production of biodegradable films based on renewable low cost resources has increased considerably. The research and development of new materials in this segment make possible to replace, even still partially, the synthetic plastics derived from petrol and to add value to agro-industrial waste and agricultural commodities. The fruit purees (or pulp) represent an alternative for obtaining these low-cost arrays. It can be obtained from the fruit itself or from its processing wastes. Amongst the suited fruits for this purpose is the papaya (Carica papaya), largely available. Brazil is the largest producer of this fruit and, due to its high perishability, is a rich source of waste material for pulp and edible film processing. Although the films prepared from fruit puree lacks in mechanical and permeability properties, such features may be minimized by the addition of nanofillers associated to film forming biopolymers. Thus, the evaluation of papaya puree, in over-ripe stage, as raw material for film processing using a Mathis System (in batch mode) with reinforced nanostructure was the main aim of this study. The films were characterized considering mechanical and thermal properties, permeability, colorimetric and antimicrobial activity. The best results were recorded to formulations in which the pectin was added at 0.5 % (w/v), increasing the maximum fracture strength (σmax), in 12 times when compared to neat puree films (control). The insertion of cellulose nanofibers and chitosan nanoparticles also promoted a σmax increasing, nevertheless in inferior proportion (6.2 and 5 times respectively). The presence of pectin also was positive in reducing the permeability rates (WVP) with values of 77.72 % lower than those measured to the control films. Concerning the colorimetric properties, the films with filler additions (chitosan nanoparticles with glycerol) suffered the greater color changes (ΔE). The addition of chitosan nanoparticles also speed the surface browning index (BI). Again the pectin acted positively in preserving the original color characteristics. The antimicrobial essays indicated that the chitosan in nanoparticle format inside the polymeric matrix did not present any antimicrobial activity. The over-ripe papaya pulp showed to be a raw material suitable for edible biodegradable film processing and the addition of nanofillers and pectin necessary to improve the barrier and mechanical properties and to preserve the original colorimetric features.
A produção de filmes biodegradáveis baseados em recursos renováveis, fazendo uso de matrizes biopoliméricas de baixo custo, vem aumentando consideravelmente. A pesquisa e o desenvolvimento de novos materiais neste segmento possibilitam a substituição, ainda que parcial, dos plásticos sintéticos derivados do petróleo, além de agregar valor a resíduos agroindustriais e commodities agrícolas. Os purês de frutas (ou polpa) representam uma alternativa viável para a obtenção destas matrizes, podendo ser empregados a própria fruta ou rejeitos provenientes de seu processamento. Dentre os frutos adequados para este fim está o mamão papaia (Carica papaya), fartamente disponível no país. O Brasil é seu maior produtor mundial e, devido à sua alta perecividade, é uma fonte rica de rejeitos adequados à produção de polpas e ao processamento de filmes comestíveis. Embora os filmes processados a partir de purê de frutas apresentem limitações mecânicas e de permeabilidade, estas características podem ser minimizadas pela formação de compósitos através da inserção de nanoestruturas de reforço e associação com outros biopolímeros com características filmogênicas. Assim, avaliar o uso de polpas de mamão papaia, em adiantado estado de maturação no processamento de filmes em Sistema Mathis (no modo batelada) e o efeito da inserção de estruturas de reforço, foram os principais objetivos deste trabalho. Os filmes foram caracterizados quanto às suas propriedades mecânicas, térmica, de permeabilidade, colorimétrica e antimicrobiana. Os melhores resultados foram obtidos para as composições em que a pectina foi adiciona em 0,5 % (m/v), elevando a tensão máxima de ruptura (σmax), em 12 vezes quando comparada aos filmes de polpa sem aditivos (controle). A adição de nanofibras de celulose e a nanopartículas de quitosana também melhoraram σmax, mas em valores inferiores (6,2 e 5 vezes respectivamente). A inserção da pectina também foi favorável na redução das taxas de permeabilidade (WVP) com valores 77,72 % inferiores aos filmes controle. Com relação às medidas colorimétricas, as maiores alterações registradas foram para os filmes processados com os reforços (quitosana em conjunto com o glicerol), os quais resultaram em uma maior variação total de cor (ΔE). A presença de nanopartículas de quitosana também acelerou o escurecimento superficial (IE). A adição de pectina nas formulações atuou positivamente na preservação das características colorimétricas iniciais. Os testes antimicrobianos indicaram que a quitosana na forma de nanopartículas inseridas na matriz biopolimérica não apresentou atividade antimicrobiana. A polpa de mamão papaia, na condição sobremadura, mostrou ser uma matéria-prima adequada ao processamento de filmes comestíveis biodegradáveis e a adição de nanoreforços e de pectina necessárias para a melhoria das propriedades mecânicas e de barreira e para a preservação das características colorimétricas iniciais dos filmes.

Ökningen av världspopulationen har orsakat en ökad avfallsgenerering. Avfallet kan innehålla betydelsefulla ämnen, vilka kan användas som råvaror i många olika material och för olika ändamål. Därför har omfattande forskning genomförts för att ta till vara på avfall som orsakar miljöföroreningar och ur dessa utveckla mer hållbara och biologiskt nedbrytbara material. Exempel på detta är fibrer och textilier framställda av polysackaridmaterial, särskilt från kitin och kitosan, som finns tillgängliga som biprodukt från såväl skaldjur som insekter och cellväggar från svampar. Kitin är efter cellulosa den vanligaste aminopolysackarid-polymeren som har en liknande struktur, medan kitosan är den deacetylerade formen av kitin som är den mest välkända och det viktigaste derivatet av kitin. Kitosan kan framställas från kitin genom antingen kemisk deacetylering eller enzymatiska beredningar, men för kommersiell skala idag, är produktion av kitosan med kemisk metod som deacetylering av kitin med en alkali såsom NaOH, mer lämplig och att föredra. Både kitin och kitosan är biobaserade material som har speciella egenskaper såsom hög specifik styvhet och hållfasthet, samtidigt som biologisk nedbrytbarhet är möjlig. Dessutom förekommer materialen rikligt i naturen, vilket gör dem till passande och konkurrenskraftiga ersättare till traditionella fibrer. Textilier är en stor källa till koldioxidutsläpp på grund av massiv global produktion och att även icke-nedbrytbara fibrer i vissa fall används i produktionen. Fibrer är den elementära enheten i textilier förutom bomull, som traditionellt används för textilproduktion. Det finns olika typer av fibrer som vanligtvis delas in i syntet- och biobaserade fibrer härrörande från förnybara resurser. Dessa förnybara fibrer har skapat ett stort intresse från världens textiltillverkare för att ställa om sin produktion och exempelvis producera gasbindor med återvinningsbara och biologiskt nedbrytbara material. Användningen av kitin och kitosan i textilindustrin är mycket intressant och viktig, dels på grund av deras mångsidighet och stora överflöd i naturen, dels då materialen annars anses vara spill eller restprodukter utan signifikant betydelse. Syftet med denna avhandling var att göra en litteraturöversikt om metoder för produktion av fibrer och textilier från kitin och kitosan, samt att undersöka hur de kan användas och dess miljövänliga aspekter. I denna avhandling har olika metoder baserade på många undersökningar och experiment introducerats, för att förstå och utvärdera möjliga processer för bildning av kitin- och kitosanfibrer. Dessutom har egenskaperna hos de framtagna fibrerna såsom draghållfasthet och töjning undersökts. För kitinproduktion har fem olika metoder studerats med användning av olika lösningsmedel av joniska vätskor såsom 1-etyl-3-metylimidazoliumacetat [C2mim] OAc, 1-butyl-3-metylimidazoliumklorid [C4mim] Cl och 1-etyl-3-metylimidazoliumklorid [C2mim] Cl, triklorättiksyra (TCA) och metylenklorid, en kombination av TCA, klorhydrat och metylenklorid, en blandning av myrsyra (FA), diklorättiksyra (DCA) och isopropyleter (iPE), liksom en direkt upplösning i NaOH/tiourea/urea. Produktion av nanofibrer från krabbskal, räkskal, kommersiella kitinpulver och svamp har undersökts, samt sårförband som en icke-vävd textil, genom att undersöka två olika produktionsmetoder. Många studier på kitosanproduktion har listats med fokus på typen av spinnteknik såsom våtspinning med användning av en cellulosa/kitosan-kompositlösning samt fibrer bildade av myrsyramodifierad kitosan. Dessutom listas olika typer av tekniker för torrspinning, torrstråle-våtspinning och elektrospinning. Slutligen har sårförbandsprocessen med användning av icke-vävda textilier av chitosan/hyaluronan också inkluderats. Sammanfattningsvis är produktion av textilfibrer med kitin och kitosan möjlig och kan göras på olika sätt. På grund av deras egenskaper och antimikrobiella effekter blir de intressanta alternativ till medicinska tillämpningar såsom suturer, sårförband, vävnadsteknik och antimikrobiellt medel. I likhet med andra material har kitin och kitosan fördelar, men även vissa nackdelar såsom svag och låg draghållfasthet hos de framtagna fibrerna och att de är delvis lösliga i substanser med pH under 5,5. Produktion av fibrer och textilier baserade på kitin och kitosan är fortfarande en utmaning på grund av de många modifieringssteg som krävs. Bland annat måste man ta hänsyn till lösningsmedlet som används för upplösning, välja rätt spinnteknik samt att använda ett lämpligt koagulationsbad följt av en flerstegs tvätt- och torkningsprocess. Dessa metoder hjälper till för att uppnå önskade fibrer med en mycket god kvalitet. För att uppnå en kostnadseffektiv, miljövänlig, konkurrenskraftig och storskalig textilproduktion - särskilt inom klädindustrin - krävs därför framtida arbete för att förfina och utveckla tekniken.
The growing of the world population caused an increase in waste generation which may contain high-value substances that can be used as raw materials in many applications. Therefore, tremendous research has been done towards the conversion of those wastes, that cause environmental pollution, in more sustainable and biodegradable materials. Part of these materials are fibers and textiles produced from polysaccharide materials especially from chitin and chitosan. Both chitin and chitosan are available as a by-product of seafood as well as in insects and cell walls of fungi, and can be used in many different applications. Chitin is the most abundant amino polysaccharide polymer after cellulose which has a very similar structure to cellulose, while chitosan is the deacylated form of chitin and it is the well-known and the most important derivative of chitin. Chitosan can be produced from chitin by either chemical deacetylation or enzymatic preparations. However, at commercial scale nowadays, the production of chitosan by chemical method like deacetylation of chitin with an alkali such as NaOH, is more suitable and preferable. Both chitin and chitosan are bio-based materials that have special properties such as high specific stiffness and strength, they are biodegradable and plentifully available in the nature, which make them an active competitive to the production of the synthetic fibers. Textiles are a big source for carbon emissions because of their large volume production and origin, in some cases, from non-biodegradable fibers. Fibers are the elementary units of textiles besides cotton that is traditionally used for textile production. There are different types of fibers that are usually divided into synthetic- and bio-based fibers derived from renewable resources which are getting a lot of interest in order to produce more biodegradable materials. Therefore, using chitin and chitosan in the textile industry is very important due to their versatility and large abundancy in nature. Additionally, they are biodegradable, biocompatible, non-toxic, and they are essentially able to form fibers and textiles. The purpose of this thesis was to make a literature review about the methods for the production of fibers and textiles from chitin and chitosan, including their applications and their environmentally friendly aspects. Different methods have been introduced in this thesis based on many researches and experiments in order to understand and evaluate which are the possible processes for chitin and chitosan fiber formation as well as the properties of the resulted fibers such as tensile strength and elongation. For fiber production from chitin has been studied by using different solvents including ionic liquids such as 1-ethyl-3-methylimidazolium acetate [C2mim]OAc, 1-butyl-3-methylimidazolium chloride [C4mim]Cl and 1-ethyl-3-methylimidazolium chloride [C2mim]Cl, trichloroacetic acid (TCA) and methylene chloride, a combination of TCA, chloral hydrate and methylene chloride, a mixture of formic acid (FA), dichloroacetic acid (DCA) and isopropyl ether (iPE), as well as a direct dissolution in NaOH/ thiourea/ urea. Additionally, nanofibers production from crab shells, prawn shells, shrimp shells, commercial chitin powders and mushrooms has been studied. Finally, wound dressing which is one of the nonwoven fabrics applications is introduced by referring to two methods of production. For fiber production from chitosan, many studies have been listed focusing on the type of the spinning technique such as wet spinning by using a cellulose/chitosan composite solution as well as fibers formed from formic acid modified chitosan. In addition, dry spinning, dry-jet wet spinning and electrospinning techniques have been studied. The wound dressing process by using chitosan/hyaluronan nonwoven fabrics has also been introduced. In conclusion, the production of textile fibers made of chitin and chitosan is possible and can be made in different ways. And because of their properties as biocompatibility, nontoxicity as well as their antimicrobial effects, they become interesting candidates for medical applications such as in sutures, wound dressing, tissue engineering and as antimicrobial agent. Similar to other manufactural industries, the production of fibers and textiles from chitin and chitosan have many advantages such as good values for dry tensile strength and elongation at break, antimicrobial activity and many more. At the same time, this production has some disadvantages such as the weak and low tensile strength of the resulted fibers and that they are partially soluble at pH below 5.5. Producing fibers and textiles based on chitin and chitosan is still a challenge because of the many modification steps that are needed. The modifications include the solvent used for dissolution, choosing the proper spinning technique as well as using an appropriate coagulation bath followed by the conditions of washing and drying steps. Thus, the desired fibers with a very good quality mentioned before would be achieved. Therefore, a lot of future work is needed in this manner because the intention is to achieve a cost-effective, environmentally friendly and a competitive technology for the large scale textile production especially in clothing industries.

The present Thesis focuses on the fabrication of polysaccharide – based nanofibrous mats via electrospinning technique primarily for, but not limited to, the development of wound healing patches with enhanced tissue regeneration capabilities. Specifically, this project arose to overcome the lack of methodologies concerning the proficient electrospinning of polysaccharides due to their poor processability, the requirement of hazardous and/or toxic solvents, and nanofiber inadequate stability in aqueous environments. To tackle this task, this Thesis proposes the use of poly(ethylene oxide), a biocompatible and water – soluble synthetic polymer able to increase the polysaccharide – based formulation spinnability, along with a simple washing – physical crosslinking treatment to fabricate pure polysaccharide nanofibers with boosted water resistance and marked biocompatibility. In the first Chapters, after a general discussion concerning the technological relevance and versatility of electrospinning technique together with its main applications, this Thesis concentrates on briefly presenting the properties of polysaccharide materials and their advantages with respect to synthetic polymers, as well as the experimental methodologies and characterization approaches used to achieve the investigated purpose. Then, either alginate or chitosan polysaccharides are employed for the fabrication of nanofibrous mats, whose physical – chemical properties, drug delivery capabilities, and biological responses are fully characterized. As a matter of fact, the developed systems effectively display a significant capacity to promote cell adhesion and proliferation along with proper mechanical, water – related, and drug release features, hence representing promising materials to be used in several biomedical and pharmaceutical products. Finally, the preparation of a multilayer nanofibrous patch comprised of an external hydrophobic stratum and an internal bioactive one is explored and discussed. To this end, combining a polyurethane nanofibrous layer with an alginate nanofibrous layer enriched with ZnO nanoparticles allows the fabrication of potential wound healing patches endowed with superior support and protective performances. These results are an important first step in making straightforward the electrospinning of polysaccharide materials granting the possibility to easily prepare nanofibrous meshes with potential uses in various application fields, with particular relevance in the biomedical and pharmaceutical industries where the bioactivity of these materials with respect to synthetic polymers plays a topical role.

A possível escassez dos recursos fósseis, juntamente com o aumento imprevisível dos respectivos preços, levou, nas últimas décadas, a um aumento considerável de iniciativas dedicadas não só à procura de fontes alternativas de produtos químicos e polímeros a partir de fontes renováveis, mas também de fontes alternativas de energia - em particular a biomassa vegetal. O estudo desenvolvido no presente trabalho está inserido neste contexto. A despolimerização de celulose de sisal pode ocorrer via hidrólise, ácida ou enzimática, podendo resultar nos açúcares fermentescíveis necessários para a produção do chamado etanol celulósico e, em etapas intermediárias do processo, em micro e nanopartículas, que podem atuar como reforço de matriz polimérica baseada, por exemplo, em quitosana. O estudo aqui relatado está relacionado à análise do material celulósico não reagido durante a hidrólise, e do licor que contém principalmente glicose. As reações de hidrólise ácida e enzimática de polpa de sisal (constituída de celulose e hemicelulose) foram exploradas. Uma importante característica que envolve a hidrólise ácida de biomassa é a possibilidade de utilização de diversos ácidos, pois a princípio, necessita-se apenas de uma fonte de prótons no meio aquoso para que a reação ocorra. Neste contexto, em uma primeira etapa, uma série de reações de hidrólise ácida de polpa de sisal, previamente tratada com solução alcalina (mercerizada) ou não, foi feita com ácido sulfúrico (0,9 - 4,6 molL-1, 100°C, 6h de reação). Em uma segunda etapa, o ácido sulfúrico foi substituído por ácido oxálico, e os tempos de reação foram maiores (18h) que aqueles considerados para o ácido sulfúrico, tendo em vista o menor valor do pKa do ácido oxálico. Reações de hidrólise enzimática foram realizadas com o uso de um complexo enzimático comercial (Accellerase 1500 - Genencor), e dois diferentes pré-tratamentos, ambos visando à eliminação de hemiceluloses, foram avaliados, sendo: mercerização e tratamento com solução de ácido oxálico 0,9 molL-1. Para acompanhar os processos, em determinados intervalos de tempo, foram retiradas alíquotas do meio reacional, sendo que os licores foram analisados por cromatografia líquida de alta eficiência (CLAE), a fim de avaliar a natureza e o teor dos produtos da hidrólise. As polpas residuais (não hidrolisadas), suspensas no licor, foram avaliadas por microscopia eletrônica de varredura, massa molar média por viscosimetria capilar, índice de cristalinidade por difração de raios X e tamanhos médios das fibras a partir de um analisador de fibras (MorFi - analisador de tamanho médio de fibras por imagem), e espalhamento de luz (FOQELS). Para todas as reações de hidrólise ácida estudadas, as massas molares médias das polpas residuais diminuíram até dez vezes logo nos primeiros minutos de reação e os valores de índice de cristalinidade mostraram que as regiões não cristalinas da celulose são primeiramente hidrolisadas, sendo as regiões cristalinas uma grande barreira frente à hidrólise. Os resultados mostraram que o aumento da concentração do catalisador ácido elevou consideravelmente a porcentagem de hidrólise, principalmente no caso do ácido oxálico que, quando usado na concentração de 0,9 molL-1, não foi capaz de hidrolisar com eficiência as cadeias de celulose, mas apenas eliminou as hemiceluloses presentes na polpa, motivo que levou à sua aplicação como agente de pré-tratamento para a polpa frente à hidrólise enzimática. Os rendimentos das reações mostraram que o ácido sulfúrico chega a ser aproximadamente 25% mais eficiente que o ácido oxálico em termos de produção de glicose. Entretanto, o ácido oxálico possui a grande vantagem de ser proveniente de fontes renováveis e, se usado nas concentrações adequadas, pode ser uma excelente opção como pré-tratamento da polpa de celulose para as reações de hidrólise. Os resultados de hidrólise enzimática mostraram que a polpa que passou pelo pré-tratamento da mercerização foi mais eficiente como material de partida do que aquela tratada com ácido oxálico, já que a primeira levou a concentrações de glicose até 2,5 vezes maiores, nas mesmas condições de concentração de enzima, temperatura e tempo de reação. As reações de hidrólise ácida e enzimática de material lignocelulósico são de grande importância no que diz respeito à produção de etanol de segunda geração e micro/nanofibras que podem ser incorporadas em materiais. Filmes de matriz de quitosana foram produzidos com a inserção de fibras de celulose sem tratamento, mercerizada, e residuais das reações de hidrólise ácida e enzimática, em diferentes concentrações (2,5, 7,5 e 15% em massa). Os filmes foram submetidos à solicitação de tração, e a morfologia foi acessada por microscopia eletrônica de varredura de emissão de campo (FEG-MEV). Os resultados mostraram que, no geral, o filme de quitosana (69 MPa), assim como os baseados em quitosana/celulose (75 MPa), apresentam resistência à tração superior ou no mesmo patamar de filmes similares descritos na literatura. Este trabalho forneceu resultados promissores e está largamente inserido no interesse atual de utilização de materiais provenientes de fontes renováveis preferencialmente àqueles de fontes fósseis.
The possible shortage of crude oil and the unpredictable increase in its prices have led to an impressive expansion of initiatives in the last decades dedicated not only to the search of alternative sources of chemicals and polymers, but also to suppliers of energy, both from vegetal biomass. The depolymerization of sisal cellulose may occur via acid or enzymatic hydrolysis, resulting in the fermentable sugars used in the production of the so-called cellulosic ethanol and also at the intermediate steps of the process, in micro and nanoparticles that may act as reinforcement in polymeric matrices, including those derived from cellulose. The study here reported is related to the analysis of the unreacted cellulosic material and to the liquor containing mainly glucose, from acid and enzymatic hydrolysis of sisal pulp formed by cellulose and hemicellulose. An important characteristic that involves the acid hydrolysis of biomass is the possibility of utilization of different acids, since only a source of protons in the media is required for the reaction to occur, in principle. In this context, a series of reactions of acid hydrolysis of sisal pulp was carried out under varying concentrations of sulfuric acid, from 0,9 to 4,6 molL-1, at 100°C as a first step. In a second step, the acid catalyst was replaced by oxalic acid, and the reaction lengths were bigger than those considered for sulfuric acid due to the lower value of pKa of oxalic acid. The reactions of enzymatic hydrolysis were carried out with a commercial enzymatic complex (Accellerase 1500 - Genencor), and two different pretreatments, both aiming at the elimination of hemicelluloses, were essayed as follows: mercerization and treatment with oxalic acid 0,9 molL-1. To follow the processes of acid and enzymatic hydrolysis in determined time intervals, aliquots were withdrawn from the reaction media so as to be analyzed by High Performance Liquid Chromatography (HPLC) aiming at the evaluation of the nature and content of the hydrolysis products. The unreacted cellulose suspended in the liquor was characterized by Scanning Electron Microscopy, capillary viscometry, X ray diffraction, and average size of fibers by using a fiber analyzer and light scattering. For all acid hydrolysis reactions studied, the average molar mass of the unreacted cellulose decreased up to ten times in the first minutes of reaction, and the values of crystallinity index showed that the non-crystalline regions of cellulose are firstly hydrolyzed, and the crystalline regions act as barriers to the hydrolysis. The results of HPLC showed that an increase in concentration considerably increases the yield of hydrolysis, mainly in the case of oxalic acid as a catalyst, which was not able to hydrolyze the chains of cellulose when in low concentrations (0,9 molL-1). It only eliminated the hemicellulose present in the pulp, reason why this acid was used as a pretreatment agent in enzymatic hydrolysis at this concentration. The reaction yields showed that the sulfuric acid can be up to 25% more efficient than the oxalic acid in terms of glucose production. However, the oxalic acid has the great advantage of possibly being produced from natural resources as well as being an excellent choice as a pretreatment agent for the lignocellulosic biomass to be used in hydrolysis reactions if used in the adequate concentrations. The results of enzymatic hydrolysis showed that the mercerized pulp was more efficient as raw material than the one treated with oxalic acid, as the first led to higher glucose content at the same conditions of concentration, temperature and time of reaction. The reactions of acid and enzymatic hydrolysis of lignocellulosic materials are of great importance to the production of second generation ethanol and micro and nanofibers, which may be incorporated into biocomposites. Films of chitosan matrix were prepared with the addition of cellulose fibers (untreated, mercerized and residual from the acid and enzymatic hydrolysis reactions) under various concentrations (2,5, 7,5 e 15% wt%). The films were subjected to traction analysis and its morphology was accessed by field emission scanning electron microscopy (SEM-FEG). The results showed that, in general, chitosan films (69 MPa), just like films based on chitosan-cellulose (75 MPa) presented tensile strength values that are superior or the same as similar films described in literature. Therefore, the study here reported produced promising results and is widely inserted in the current interest of utilization of materials from renewable resources instead of those from fossil resources.

The diploma thesis if focused on the study of bioactive hydrogél and nanofiber wound dressings composed of natural biopolymers, which were functionalized by active compounds in the form of analgesic, antibiotics and enzymes. Hydrogél wound dressings were constituted from alginate and chitosan and nanofibers were created from polyhydroxybutyrate. The following 7 active compounds were selected to be added to the wound dressings: ampicillin, streptomycin, ibuprofen, papain, bromelain, collagenase and trypsin. In the theoretical part the structure of the skin and types of wound injuries were described. This part also talks about types of wound dressing and their applications, as well as treatment of skin wounds using enzymes and compounds with analgesic and antimicrobial properties. In addition, this section describes safety assays, in particular cytotoxicity assays on human cells. At the beginning of the experimental part, the process of preparation of hydrogél wound dressing was optimised. Subsequently, the dressings were enriched with active compounds and the rate of gradual releasing of the substances into model environment was monitored. In the case of enzymes, their proteolytic activity was also tested after their incorporation to the wound dressings. Furthermore, the prepared bioactive wound dressings were analyzed for possible cytotoxic effect on human keratinocytes. Finally, the wound dressing with combined content of active substances was created and also characterized for the rate of substance release, proteolytic activity and cytotoxicity. Antimicrobial activity of this wound dressings, against two selected strains of microorganisms: Escherichia coli and Staphylococcus epidermidis, was also evaluated.

Les maladies cardiovasculaires représentent la première cause de mortalité dans les pays développés. Ces maladies ont pour étiologie l’athérosclérose, une pathologie artérielle provoquée par l’accumulation de dépôts lipidiques sur la paroi de l’artère engendrant une obstruction partielle (sténose) ou totale de l’artère (thrombose). L’angioplastie avec pose de stent élué de principe actif antiprolifératif ou anti-inflammatoire est le traitement de référence pour lutter contre ces pathologies, qui sont les principales causes d’infarctus du myocarde et d’accidents vasculaires cérébraux. Cependant, le traumatisme subi par la paroi de l’artère lors de la pose de stents et l’utilisation de principes actifs non sélectifs provoquent des complications post-opératoires graves telles que la resténose intra-stent et la thrombose aigüe. Dans ce contexte, l’objectif de ce travail est de développer un stent vasculaire recouvert de nanofibres (NFs) par electrospinning dans le but de prévenir l’apparition de la resténose et de la thrombose après l’intervention. Ainsi, le stent développé est enrobé de deux couches de NFs : une première couche anti-thrombotique pour prévenir la coagulation intra lumen, et une deuxième couche chargée de simvastatine, qui sera directement en contact avec la paroi artérielle, pour prévenir la resténose. Les NFs à propriétés anti-coagulantes sont élaborées à partir de CHT modifié porteur de groupements sulfonés présentant des propriétés biologiques proches de celles de l’héparine. Les NFs à propriétés anti resténose sont composées d’un complexe de polyélectrolytes formé à partir d’interactions électrostatiques entre le chitosan (CHT), qui assurera également la fonction de matrice biorésorbable des nanofibres, et de polymère anionique de cyclodextrines (PCD). Les NFs sont chargées de simvastatine, molécule pleiotrope avec une activité anti-resténose, qui est libérée de façon prolongée grâce aux propriétés d’inclusion des cyclodextrines
Cardiovascular diseases are the first cause of death in developed countries. Atherosclerosis is the first pathophysiological cause promoting this disease that interests the arterial wall and would promote the development of lumen stenosis and thrombosis. Angioplasty and implantation of Drug-Eluting stents can be suggested to re-open the arterial lumen; however, restenosis (anarchic wall healing) and thrombosis can occur after the surgery. This work aims at functionalizing a vascular stent by electrospinning with two layers of nanofibers (NFs) based on biopolymers: the first layer would contain antithrombotic properties to prevent blood clot formation within the lumen and a second drug layer that would deliver simvastatin (SV) to the vessel wall, for preventing restenosis. Antithrombotic layer is based on modified chitosan containing sulfonated groups having a similar biological effect than heparin. The second layer with antirestenosis properties is based on a polyelectrolyte complex composed of chitosan (cationic), also used as bioresorbable matrix, and β-cyclodextin polymer (anionic), and are loaded with simvastatin, a pleiotropic drug acting against restenosis. Cyclodextrins are used to extend the release of simvastatin thanks to inclusion complexes formation

The diploma thesis is focused on the study of fibrous wound dressings prepared by electrospinning method from natural biopolymers. Three active ingredients were added to the dressings: ampicillin, ibuprofen and collagenase, which are responsible for relieving pain, reducing the risk of infection and selectively removing necrotic tissue in the wound. The theoretical part describes the therapeutic dressings currently available on the market and the most common methods of nanofiber production. The experimental part evaluates the optimization of the preparation of gelatin, alginate and chitosan fibrous wound dressings, which were subsequently enriched with active substances and their gradual release into the model environment was determined spectrophotometrically. Antimicrobial effects against E.coli and S. epidermidis strains andantifungal activity against C. glabrata yeast were monitored. Finally, two cytotoxicity tests on the human keratinocyte cell line HaCaT confirmed the safety of the prepared products, which can serve as bioactive skin dressings in the future.

Les textiles sont utilisés dans le domaine biomédical, notamment pour le soin des plaies ou pour la conception de prothèses de substitution ou de régénération d’organes endommagés par la maladie ou par cause accidentelle. Le cahier des charges des textiles médicaux évolue vers l’élaboration de biomatériaux biorésorbables et bioactifs capables d’interagir spécifiquement avec les tissus vivants en fonction de leur nature. Dans ce contexte, le projet de recherche consiste à concevoir, par electrospinning, deux types de membranes nanofibreuses bioactives à base de chitosane. Dans une première approche, des nanofibres de chitosane à ont été fonctionnalisées par la polydopamine qui contient des groupements catéchols capables d’induire la biominéralisation in vitro dans un milieu riche en ions calcium et phosphate. Ces membranes à propriétés ostéoinductrices pourraient être utilisées comme scaffolds pour la régénération tissulaire guidée en parodontologie. Dans une deuxième approche, l’élaboration de nanofibres à propriétés anticoagulantes à base de chitosane a été menée. Le chitosane a été d’abord chimiquement modifié par des groupements sulfonates. Les paramètres de synthèse ont permis de contrôler le degré de sulfonation du chitosane et ses nouvelles propriétés caractéristiques d’un polyampholyte ont été observées. Les essais biologiques effectués ont montré que ces dérivés sulfoniques sont non hémolytiques et bénéficient de propriétés anticoagulantes. Puis, des nanofibres de chitosane sulfoné ont été obtenues par electrospinning conduisant à des membranes à propriétés antithrombotiques, ce qui en fait des candidats de choix pour la fonctionnalisation de stents vasculaires
Textiles are widely used in the biomedical field, in particular for the care of wounds or the design of prostheses for strengthening or regenerating organs damages by the disease of by accidental cause. The specifications for medical textile are evolving towards the development of bioresorable and bioactive biomaterials that are capable of interacting with living tissues according to their nature. In this context, the research project consists of generating, by electrospinning, two types of biomimetic and bioactive nanofibrous membranes based on chitosan. In a first approach, nanofibres of chitosan have been functionalized by polydopamine that contains catechol groups capable of inducing the in vitro biomineralization in a medium rich in calcium and phosphate ions. Thus, these nanofibrous membranes with osteoinductive properties could be used as scaffolds for guided tissue engineering in periodontology. In a second approach, the development of chitosan-based nanofibers with anticoagulant properties was conducted. Chitosan was initially chemically modified by sulfonate groups. The synthesis parameters allowed to control the degree of sulfonation of chitosan and its new polyampholyte specific character was observed. The different biological assays carried out have shown that these sulfonic derivatives are non-hemolytic and benefit from anticoagulant properties. Then, sulfonated chitosan-based nanofibres were obtained by electrospinning leading to membranes with antithrombotic properties, make them suitable candidates for the functionalization of vascular stents

This diploma thesis is focused on the study of bioactive wound dressings. During the thesis, hydrogel, lyophilized and nanofiber wound dressings were prepared. Hydrogel and lyophilized wound dressings were prepared on basis of two polysaccharides – alginate and chitosan. Nanofiber wound dressings were prepared by spinning polyhydroxybutyrate. All prepared wound dressings were enriched with bioactive substances, which represented analgesics (ibuprofen), antibiotics (ampicillin) and enzymes (collagenase). Into hydrogel and lyophilized wound dressings were all the mentioned active substances incorporated, whereas nanofiber wound dressings were only with ibuprofen and ampicillin prepared. The theoretical part deals with the anatomy and function of human skin. There was explained the process of wound healing and also there were introduced available modern wound dressings. The next chapter of the theoretical part deals with materials for preparing wound dressings (alginate, chitosan, polyhydroxybutyrate) and with active substances, which were used during the experimental part of this thesis. In the theoretical part, the methods of preparation of nanofiber wound dressings and also the methods of cytotoxicity testing used in this work were presented. The first part of the experimental part of this thesis was focused on preparing already mentioned wound dressings. Then, their morphological changes over time and also the gradual release of incorporated active substances into the model environment were monitored. The gradual release of ampicillin was monitored not only spectrophotometrically, but also by ultra-high-performance chromatography. In wound dressings, in which collagenase was incorporated, was also the final proteolytic activity of this enzyme monitored. The effect of the active substances was observed on three selected microorganisms: Escherichia coli, Staphylococcus epidermidis and Candida glabrata. The cytotoxic effect of the active substances on the human keratinocyte cell line was monitored by MTT test and LDH test. A test for monitoring the rate of wound healing – a scratch test – was also performed.

Electrospun nanofibers have been used for many applications, but a reliance on organic solvents limits their use in biomedical fields. In this study, we successfully electrospun nanofibers from aqueous chitosan-hyaluronic acid complex coacervates. We studied how solvent’ properties affected the average nanofiber diameter by using pure water as a solvent versus ethanol-water solutions. Experimentally, we investigated the effect of electrospinning apparatus parameters, such as how the applied voltage affected fiber formation and morphology. The smallest average nanofiber diameter was determined to be around 115 ± 30 nm when 3 wt% ethanol coacervate samples were electrospun using the applied voltage of 24 kV. Linear viscoelastic measurements were used to study the rheological characterization of complex coacervate with different salt concentrations and cosolvents (e.g., ethanol weight percent). Chitosan-hyaluronic acid nanofibers hold potential in biomedical applications such as wound dressing, tissue engineering, would healing scaffolds.

碩士
國立臺北科技大學
化學工程研究所
99
Tissue engineering includes three major elements: cells, scaffolds, and signal molecules. We are focuses on how to prepare the mimic extracellular matrices whose components and porous structures are analogous to those of the native extracellular matrices (ECMs). Electrospun nanofibers have amazing characteristics such as very large surface area-to-volume ratio and high porosity with very small pore size. The process was an efficient technique for the fabricationof both natural and synthetic polymers nanofibers and various polymer have been electrospun. Collagen, chitosan, polyvinyl alcohol(PVA) are biodegradable, biocompatible materials. We using concentrated acetic acid solution(90%) as a solvent. Because more concentrated acetic acid in water progressively decreased surface tension of the chitosan solution and concomitantly increased charge density of jet. Electrospun collagen/chitosan/PVA nanofibers were crosslinked by glutaraldehyde(GTA) vapor to enhanced stability. The morphology of the electrospun collagen/chitosan/PVA nanofiber scaffolds was observed by scanning electron microscopy (SEM) and stabilized by glutaraldehyde (GTA) vapor via crosslinking. Fourier transform infrared spectra analysis showed that the collagen/chitosan/PVA nanofibers scaffold do not change significantly, except for enhanced stability after crosslinking by GTA vapor. The thermal behavior was studied by thermal gravimetric analysis and the mechanical properties were Studied by tensile testing. To assay the biocompatibility of electrospun scaffolds, cellular behavior on the nanofibrous scaffolds was also investigated by SEM, methylthiazol tetrazolium testing(MTT) and dsDNA content. The cyototoxic effecy of GA-vapor crosslinked scaffolds was observed. The scaffolds show almosted no cellular activity.

博士
國立臺灣科技大學
化學工程系
100
Chitosan (CS) nanoparticles were fabricated by an electrospraying method. The effects of CS molecular weight on electrospraying were investigated. The size and morphology of CS particles were strongly influenced by CS molecular weight. Moreover, CS concentration, electrical field, acetic acid concentration, and solution flow rate in the electrospraying process were also studied. The electrosprayed CS nanoparticles were applied for drug delivery and metal-ion adsorption. To evaluate the potential of electrosprayed CS nanoparticles in drug delivery, indomethacin (ID) was used as a model drug, where the encapsulation efficiency, the loading capacity, and the releasing profiles were identified. The spherical CS-ID nanoparticles were fabricated by the electrospraying technique with an average diameter of 340 nm. Zeta potential of the ID-CS particles indicated that the particles were stable in suspension. The encapsulation efficiency (EE) and loading capacity (LC) of ID were higher for 150-kDa CS than for 310-kDa CS. The EE of ID in electrosprayed CS particles was higher than that in particles prepared by other methods. The release profiles revealed that there were two stages for releasing and the long-term delivery could be obtained in the second stage. In summary, this research optimized the electrospraying process for the fabrication of CS nanoparticles and demonstrated the potential of electrosprayed CS nanoparticles as a drug carrier. The CS nanoparticles were also applied for the removal of Cu(II) ions from a bath aqueous solution. The electrosprayed CS nanoparticles were cross-linked by glutaraldehyde to enhance the stability in an acidic medium. In the removal process, the effects of pH, adsorbent amounts, and contact time were also studied. The metal removal strongly depended on the pH of the Cu (II) solution, the contact time, and the adsorbent amounts. The equilibrium data were analyzed by an isotherm model. The maximum adsorption capacity for Cu(II) ions was 192.3 mg/g. Hydrochloric acid (HCl) and ethylenediaminetetraacetic acid (EDTA) with various concentrations were used for the desorption of Cu(II) ions to recycle the adsorbent. Chitosan (CS) nanofibers were prepared by an electrospinning technique. The main parameters of the electrospinning process were optimized to obtained homogeneous CS nanofibers. The temperature of CS solutions as well as the chamber strongly affected on the morphology of electrospun CS nanofibers. Moreover, the effects of applied voltage, CS concentration, solvent, co-solvent, CS molecular weight, and tip-to-collector distance were all investigated in this research. The morphology of electrospun CS nanofibers was observed by SEM. The surface of the electrospun CS nanofibers were modified the surface by hydroxyapatite (HA), which was produced by two methods: in situ precipitation in a stimulated body fluid (SBF) and a wet chemical process. In SBF process, CS nanofibers were incubated in SBF for various times to form HA layers on the surface of CS nanofibers. The CS/HA nanofibers were characterized by SEM, EDS, FTIR, and XRD for confirming the HA formation as well as checking the morphology of the nanofibrous scaffolds. From the SEM image, the distribution of HA on the CS nanofibers was homogeneous. The results from EDS and XRD indicated that HA was formed on the nanofibrous surfaces after 6-day incubation in the SBF with a Ca/P ratio close to that of natural bones. To identify biocompatibility, CS/HA scaffolds were applied for the culture of rat osteosarcoma cells (UMR–106). Cell proliferation and early differentiation on the CS/HA nanofibers were better than those on the CS nanofibers, the CS/HA film, and the CS films. Biocompatibility and cell affinity were enhanced by using the composite nanofibers. Conclusively, the electrospun CS/HA scaffolds would be a potential material in bone tissue engineering. In the wet chemical process, the CS nanofibers were cross-linked by GA before mineralization by the reaction of Ca(NO3)2 and (NH4)2NO3. The time of reaction with three cycles (C3) was optimized for the preparation of electrospun CS/HA nanofibers. The time of mineralization by using wet process was about 3 hours. Meanwhile, the time of mineralization by using SBF treatment was at least 144 hours (6 days). HA XRD, SEM, FTIR, EDS analyses confirmed the formation of HA, which was similar to HA found in nature bone. The attachment and spreading of UMR cells on CS/HA nanofibers were better than those on CS nanofibers. The scaffolds of electrospun CS/HA nanofiber were suitable for bone cells.

碩士
國立成功大學
材料科學及工程學系碩博士班
100
Chitosan, known as sustainable materials with high metal binding activity and potential antibacterial properties is a promising natural polymer for high performance filtration. In case of “environmental concern”, creating an antibacterial material with a “green technology” and is an urgent. Through this research, low pressure plasma is used to synthesize silver nanopaticles in electrospinning chitosan nanofibers. Low pressure plasma offers way to reduce the usage of toxic chemical, time efficiency, and lower temperature processing in compare to other method such as chemical reduction, thermal, and UV- irradiation. This incorporation is expected to increase antibacterial properties of chitosan nanofibers. Chitosan nanofibers had been successfully electrospun on pvc grid from 5.4% w/v of chitosan and 0.6% PEO. Fibers diameter was 136 nm ± 18% without bead structures. AgNO3 addition up to 2% did not significantly change chitosan nanofibers diameter. Plasma treatment reduced Ag+ from AgNO3 precursor into Ag0 so that Ag nanoparticles were created. Besides, plasma also etched chitosan nanofibers so that reduction of fibers diameter is observed. UV- visible spectroscopy and XPS analysis revealed silver intensity will be increasing proportionally with plasma treatment time. XPS analysis also observed interaction between chitosan and Ag nanoparticles (N--Ag). Furthermore, TEM evaluation showed particle size average after 1.5 minutes plasma treatment was 1.5 nm in average. By addition of Ag nanoparticles, antibacterial activity of chitosan nanofibers could be enhanced.

Electrospinning is used to produce fibers in the nanometer range by stretching a polymeric jet using electric field of high magnitude. Electrospinning leads to the formation of continuous fibers ranging from 0.01 to 10 ìm . The ultra-fine fibers produced by electro spinning are expected to have two main properties, a very high surface to volume ratio, and a relatively defect free structure at the molecular level . The development of nanofibers by electrospinning process has led to potential applications in filtration, military protective clothing, and biological applications such as tissue engineering scaffolds, drug delivery devices , artificial organ components etc. The present study is an attempt to fabricate composite nanofibers that can be used as tissue engineering scaffolds. The approach involves the blending of two different polymers both being biocompatible and biodegradable but one is natural and other is synthetic along with a surfactant. Composites in the form of nanofibers were formed via electrospinning technique. Different ratios of Chitosan:PEO(Polyethylene glycol:DATB(Dodecyltrimethylammonium bromide) blends were prepared and successfully electrospunned so that the nanofibers obtained could mimic the natural ECM(Extra Cellular Matrix). It was found that usage of DTAB in the blend yielded fibers in the range of 50-250 nm which could be suitable for tissue engineering.. The prepared composite scaffolds were characterised using several techniques such as SEM(Scanning Electron Microscopy), FTIR(Fourier Transform Infrared Spectroscopy, XRD(X-ray Diffraction) . Also solubility and biodegradability tests were carried out for the prepared scaffolds. It was found that at feed rate 0.5ml/hr and voltage 25kV ,Chitosan:PEO ratios of 70/30 and 80/20 with DTAB concentration of 15mM yielded better nanofibers as compared to higher DTAB concentrations.

碩士
長庚大學
生化與生醫工程研究所
95
Electrospinning is a simple and effective method for producing nonwoven mat containing nanofibers. It has a special property that could fabricate nano-sized fibers directly from polymeric materials. These nanofibers have the advantages of huge surface areas and forming microporous membranes. Therefore, application of electrospinning in wound dressing manufacture potentially offers many advantages over conventional processes. Composite nanofiber membranes of chitosan, hyaluronic acid and PEO was used in this study as an artificial scaffold for wound healing and cell growth. The nanofibrous membranes had several thousands folds of surface area when compared with traditional nonwovens with fibers size in micrometer scales. Consequently the scaffold could send important signals to cells and attract fibroblast cells to derma layer, which can secrete extracellular matrix (ECM) components such as collagen and repair damaged tissue. The goal of present research is to study the production of chitosan/ hyaluronic acid composite nanofibrous membrane by electrospinning and use it as wound dressing for quick and scarless wound healing. Non-woven membranes intended as wound dressings were obtained for the first time by electrospinning of hyaluronic acid and chitosan blends in acetic acid. Our results indicate that the average diameter of chitosan/ hyaluronic acid/ PEO nanofibers were in the range of 160-455 nm. The electrospun membranes have good water uptake abilities and good water retention abilities. They are also suitable for 3T3 fibroblast growth and have good biocompatibility in vitro. From animal studies, the nanofibrous membranes were better than gauze, and commercial product in wound healing. This novel electrospun membrane will have potential in tissue engineering as a wound dressing for skin regeneration.

碩士
國立臺灣科技大學
化學工程系
102
In this research, chitosan/biphasic calcium phosphate (CS/BCP) nanofibers were prepared by electrospinning. The main parameters in electrospinning process, including applied voltage, BCP concentration, flow-rate and tip-to-collector distance, were optimized to obtaine most uniform CS/BCP nanofibers. To enhance the stability of CS/BCP nanofibers, photocrosslinking was applied with the addition of tetra-ethyleneglycol diacrylate (TTEGDA) and 2,2-dimethoxy-2-phenylacetophenone (DMPA), where the UV irradiation was incorporated with electrospinning set-up and thus a one-step crosslinking was achieved. By using the photocrosslinking process proposed in this research, nanofibers with good stability were produced continuously and efficiently. With suitable crosslinker concentrations and irradiation energy, the swelling degree of CS/BCP electrospun fibers greatly decreased, keeping network structures of nanofibers in aqueous condition. Meanwhile, the morphology of nanofibers was not changed due to the photocrosslinking. From the culture of osteogenic cells, the biocompatibility of CS/BCP nanofibrous substrates was identified and increased by the photocrosslinking. The enhancement in cell attachment and proliferation was caused by the improvement in nanofibers’ mechanical properties. The biocompatibility to osteoblasts was also promoted with the content of BCP. The osteogenic differentiation in early, middle and late stage was encouraged by the addition of BCP on nanofibrous substrates. The CS/BCP nanofibers were highly specific to osteogenic cells, revealed by difficulties in the growth of non-osteogenic cells on this composite nanofibrous scaffold. A modified electrospinning process which can continuously and easily produce biocompatible and osteoconductive CS/BCP nanofibers with high stability was developed in this study. The novel nanofibrous scaffolds showed great potential in the tissue engineering of bones.

博士
國立成功大學
化學工程學系碩博士班
101
Hyperthermia has been reported as one of the effective cancer treatment modalities since the tumor cells are more temperature sensitive than their normal counterparts. Magnetic nanoparticles were the thermoseeds under an alternating magnetic field and can be used to produce highly localized hyperthermia effect on deep-seated tumor. Nevertheless, effective and precisive delivery of nanoparticles to the treatment-intended site remains a challenge. In this study, Fe3O4 nanoparticles were incorporated onto the crosslinked electrospun chitosan nanofibers using chemical co-precipitation from the Fe ions adsorbed. Such magnetic nanoparticle nanofiber composites could be delivered to the treatment site precisely by surgical or endoscopic method. In this preliminary investigation we have explored various characteristics of the biodegradable electrospun chitosan nanofibers containing magnetic nanoparticles that were prepared by different methods. These methods including (1) E-CHS-Fe3O4: the electrospun chitosan nanofibers immersed directly into magnetic nanoparticle solution; (2) E-CHS-Fe2+: the electrospun chitosan nanofibers immersed into Fe+2/Fe+3 solution initially then followed by chemical co-precipitation for magnetic nanoparticles. Iminodiacetic acid (IDA) functionality was grafted onto the chitosan with an aim to increase the amount of magnetic nanoparticles formed in the electrospun magnetic nanofiber composite. The morphology, crystalline phase as well as the magnetism characteristic of the magnetic electrospun nanofiber matrixes was analyzed. The heating properties of these magnetic electrospun nanofibers matrixes under an alternating magnetic field (AMF) were investigated under a frequency of 750 kHz and magnetic intensity of 0.8T. In vitro cell incubation experiments indicated that these magnetic electrospun nanofibers matrixes can effectively reduced the tumor cell proliferation under the application of magnetic field. This finding suggested the magnetic electrospun chitosan nanofiber composite can be of potential for hyperthermia treatment.

碩士
長庚大學
生化與生醫工程研究所
94
Electrospinning (ES) has been a novel technique of nanoscience during the last few years. It has a special property that could fabricate nano-sized fibers directly from polymeric materials. These nanofibers have the advantages of huge surface areas and forming microporous membranes. Therefore, application of electrospinning in wound dressing manufacture potentially offers many advantages over conventional processes. Composite nanofiber membranes of type I collagen, chitosan, and PEO was used in this study as an artificial scaffold for wound healing and cell growth. The nanofibrous membranes had several thousands folds of surfaces areas when compared with traditional nonwovens with fibers size in micrometer scales. Consequently the scaffold could send important signals to cells and attract fibroblast cells to the derma layer, which can process extracellular matrix (ECM) components such as collagen and several cytokines (e.q. growth factors and angiogenic factors) and repair damaged tissue. The goal of present research is to study the production of collagen/ chitosan composite nanofibrous membrane by electrospinning and to use it as wound dressing for quick and scarless wound healing. Our results indicate that the average diameters of collagen/ chitosan/ PEO nanofibers were in the range of 134-598 nm. The electrospun membranes have good water sorption ability and the water vapour transmission rate was similar to wet human skin and better than commercial dressing. They are also suitable for 3T3 fibroblast growth and have good biocompatibility in vitro. From animal studies, the nanofibrous membranes were better than gauze, and were similar to or better than commercial product in wound healing. Histological examination indicated that the rate of epithelialization was increased and the dermis became well organized if wounds were covered with electrospun nanofibrous membrane. This novel electrospun membrane will have potential in tissue engineering as a wound dressing for skin regeneration.

碩士
長庚大學
機械工程學系
101
We developed biodegradable nanofibrous polylactide/chitosan membranes for the removal of heavy metal ions. Polylactide and chitosan were first separately dissolved intrifluoroacetic acid (TFA). The solutions were then mixed and electrospun into nanofibrous membranes via an electrospinning process. The morphology of as-spun nanofibers was examined by scanning electron microscopy. The average diameter of electrospun nanofibers ranged from 410 nm to 710 nm. The adsorption capability of nanofibrous polylactide/chitosan membranes was measured and compared with that of bulk chitosan. The influence of various process conditions on adsorption efficiency was also examined. The experimental results suggested that the electrospun nanofibrous polylactide/chitosan membranes exhibit good silver ion uptake capabilities. The metal uptake of nanofibrous membranes increased with the initial metal ion concentrations and decreased with the filtering rate of the solutions. Furthermore, the electrospun membrane could be reused after the recovery process. The empirical results in this study suggested that electrospun nanofibrous polylactide/chitosan membranes can be a good candidate for the removal of heavy metal ions.

碩士
國立臺灣科技大學
材料科學與工程系
102
In this thesis, nanofibers of poly(lactic acid) (PLA) blended with chitosan (CS) were fabricated via the electrospinning from solutions containing CS and PLA in various ratios. In particular, the solvent of the solution was a mixture of chloroform, ethanol, acetic acid and water. The morphological characteristics of nanofibers was examined using scanning electron microscope (SEM). The cytotoxicity of nanofibers was evaluated based on the proliferation of fibroblasts. The presence of chitosan in CS-PLA nanofibers were characterized using UV-Visible spectrophotometer. The antibacterial activity of these CS-PLA nanofibers was determined against Escherichia coli (E. coli). SEM images showed that average diameter of Chitosan-PLA nanofibers were nanometer length of scale. In addition, the number of beads increased with the increase of chitosan content in the Chitosan-PLA nanofibers. The uptake of an acidic dye (orange II sodium salt) indicated the presence of chitosan in the nanofibers. By culturing with L929 fibroblasts, CS-PLA nanofibers showed good cell viability, indicating non-cytotoxicity. Furthermore, CS-PLA nanofibers exhibited antibacterial activity against E. coli. The high antibacterial activity and biocompatibility suggests that these CS-PLA nanofibers have a potential in biomedical fields, especially for wound dressing applications.

碩士
國立臺灣科技大學
化學工程系
101
In this research, chitosan nanofibers were fabricated through electrospinning process under optimized conditions. The chitosan nanofibers had average diameter of 178 nm. To enhance the physical properties of chitosan nanofibers, two post-treatments were applied on chitosan nanofibers. One was the UV irradiation. The other one was photo-crosslinking with UV after photo-crosslinking agents, tetra-ethyleneglycol diacrylate (TTEGDA) and 2,2-Dimethoxy-2-phenylacetophenone (DMPA), were added into chitosan solutions used for electrospining. Electrospun fibers were characterized with scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), water contact angle and brunauer emmett teller (BET). Photocrosslinked chitosan nanofibers were successfully fabricated with the addition of TTEGDA ranging from 0 to 50-wt %. The completion of photocrosslinking reaction on chitosan nanofibers was confirmed by FTIR and TGA after the exposure to the UV light for at least 3 hours. The exposure to UV light increased the water resistance and thermal stability of chitosan nanofibers, and the enhancement was more significant when photocrosslinking agents were added. The culture of rat osteosarcoma cells (UMR) indicated that on UV-irradiated and photocrosslinked chitosan nanofibers, cell viability was increased. According to results of swelling tests, the structures of chitosan nanofibers would be maintained with the addition of photo-crosslinking agent, leading to the increase in cell viability. Thus, the osteogenic differentiation was also improved, including the expressions of alkaline phosphatase (ALP), osteocalcin (OCL), bone sialoprotein (BSP) and collagen type I (COL1). In conclusion, the present research supported that the water resistance and mechanical stability of chitosan nanofibers were improved by the exposure of UV irradiation and photocrosslinking. Moreover, photocrosslinking was able to promote the biocompatibility and osteoconductivity of electrospun nanofibers. The results in this study proved that photocrosslinked chitosan nanofibers are promising materials in the biomedical applications.

碩士
明志科技大學
化學工程系生化工程碩士班
102
The amount of phycobiliprotein is as high as 60% within Spirulina platens is cells. According to the pigment and absorption characteristics, the phycobiliprotein mainly includes C-phycocyanin (CPC) and allophycocyanin (APC). In this study, various functional groups onto the nanofiber membrane (e.g., dye-ligand, Histidine, and chitosan membranes) were obtained via different chemical synthesis. The adsorption characteristics for CPC and APC by membrane chromatography were assessed by measurements of the breakthrough curves. Moreover, the membrane chromatography was used and evaluated the dynamic adsorption behavior for CPC in clarified S. platensis. All of the experiments were carried out with a membrane module and the dynamic adsorption behavior of the membranes was monitored using an AKTA Prime chromatographic system (GE Healthcare Biosciences). Firstly, the dye and histidine modified membrane were used to investigate the adsorption performance. Unfortunately, the results showed that the total protein (TP), CPC and APC broke through the membrane at the same time. This is due to the lack of selectively of these two types of membranes. Hence, further experiments were carried out with chitosan modified membrane to examine the adsorption characteristics. The influences of NaCl concentration (0.1-1.0 M), adsorption pH (6-8), chitosan concentration (0.1-3.0 %), CPC concentration (0.05-0.50 mg/ml), and liquid flow rate (0.2-1.0 mL/min) on the adsorption performance of membrane for CPC (10 mL) were also investigated in membrane chromatography. The results showed that the order of selectivity of chitosan-membrane for proteins was found to be TP > APC > CPC under the optimal operating conditions. In this case, APC and TP molecules were more easily adsorbed by the membrane. However, the CPC molecules would most easily penetrate the membrane without being adsorbed. Hence, the filtrate containing CPC would enhance its purity. The purification factor and total mass flux was found to be 3.3 folds and 66%, respectively. Under the circumstances, the optimal operating conditions were 0.1 M NaCl, 0.3 % disrupted cells, pH 7, and liquid flow rate 0.2 mL/min. Therefore, the chitosan modified membrane can be used to remove undesired proteins and further to enhance the purity of CPC.

碩士
國立臺灣科技大學
化學工程系
105
In this research , chitosan as an organic phase and cement as an in-organic phase were combined by electrospinning as bioactive scaffolds. The composition was designed by mimicking the structure of extracel-lular matrix (ECM) of nature human bones. The main parameters in the electrospinning process, including relative humidity, cement concentra-tion and viscosity, were optimized to obtain uniform chitosan-cement nanofibers with the diameter about 250 nm. With the addition of cement, the electrospinnability of chitosan was improved. To enhance the stability of cement nanofibers, photo-crosslinking was applied with the addition of tetra-ethyleneglycol diacrylate (TTEGDA) and 2,2 dimethoxy-2-phenylacetophenone (DMPA), where the UV irra-diation was incorporated with electrospinning and thus a one-step cross-linking was achieved. By using the photo-crosslinking process proposed in this research, nanofibers with high stability were produced continu-ously and efficiently. With suitable crosslinker concentrations and irradi-ation energy, the swelling degree of electrospun fibers greatly decreased, keeping network structures of nanofibers in aqueous environment. More important, the morphology of nanofibers was not changed due to the photo-crosslinking. Compared with using only cement as cell culture substrates, chi-tosan/cement did not change pH value and temperature significantly in aqueous solution. This would be one of the reason that the composite nanofibers prepared in this study showed high biocompatibility. From the culture of osteogenic cells on nanofibers, adding cement promoted the adhesion and viability of osteoblasts. This was possibly because calcium silicate induced the formation of calcium phosphate deposition on nanofibers, which was highly bioactive to osteogenic cells. The osteogenic differentiation in early, middle and late stage were en-couraged by the addition of cement on nanofibrous substrates, revealed by the expression of ALPase, OPN and biomineralization. In this re-search, uniform and stable cement/chitosan composite nanofibers were synthesized and proved to be a promising biomaterial for the bone re-generation.

碩士
國立中央大學
化學工程與材料工程學系
105
Chitosan is a frequently used material for scaffold fabrication because it can promote cancer cells to form spheroid and enhance stem cell-relative characteristics. To mimic in vivo microenvironment, chitosan nanofibers were prepared using electrospinning technology, and their superposition can form a 3D porous structure. To effectively promote cancer stem cell adhesion, hyaluronic acid (HA) was grafted to electrospun chitosan fibers, and HA grafted chitosan films were applied as the control groups. The growth curve analysis demonstrated that HA modification reduced proliferation rates of surface cells because of its similarity to the cancer stem cell niche. On the other hand, cells grew on the fibers were faster than those on the films. The results of drug resistance examinations indicated that the chemotherapy tolerance of the cells collected from HA modified fibers was greatly improved. The levels of gene transcription determined by quantitative polymerase chain reaction (qPCR) indicated that the cells collected from HA modified fibers demonstrated high stemness, epithelial–mesenchymal transition, matrix degradation, angiogenesis, and drug resistance abilities. These results were consistent to their superior performances in colony formation, migration, and matrix invasion. Finally, flow cytometry analysis was applied to identify cell makers. The results indicated that the screened cells highly expressed the cancer stem cell-related makers CD24 and CD44, suggesting that the use of HA grafted chitosan fibers indeed increased the ratio of cancer stem cells. We expect these selected cells should be applicable to the development of anticancer drugs and the research of cancer therapy.

碩士
中華科技大學
健康科技研究所
104
Ferulic acid, a component of Chinese medicinal herbs, has been reported to possess several pharmacological effects including antioxidant, anti-inflammatory, anticancer, and antibacterial effects. In this study, electrospinning was used in preparing the composite nylon 6/chitosan nanofiber mats containing ferulic acid. The scanning electron microscopy (SEM), equilibrium water content (EWC), and water vapor transmission rate (WVTR) were used for the physicochemical characterization of the nylon 6/chitosan nanofibrous mats. Electrospinning produced nanofibrous mats with uniform structure and with an average fiber diameter ranging from 370 to 470 nm. The 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferrous iron chelating and total phenolic content assays showed that ferulic acid had retained its antioxidant activity after incorporation into the nylon 6/chitosan nanofiber mats. The biocompatibility of L929 mouse fibroblasts on the ferulic acid-loaded nylon 6/chitosan nanofiber mats was analyzed by in vitro cytotoxicity assay. In conclusion, the ferulic acid-loaded nylon 6/chitosan nanofiber mats can be applied in skin care and wound healing.

碩士
中原大學
化學工程研究所
97
In this study, the effect of spinning solution compositions and spinning parameters on the morphology of electrospun chitosan(CS) nanofiber and the application for compatibility of cell attachment and proliferation were investigated. In this article, the effects of the degree of deacetylation(D.D.) of chitosan, molecular weight of PEO, concentration of spinning solution, degradation time, feed flow rate, operating voltage and working distance on the fiber morphology and diameter were studied. From viscosity measurement, viscosity of spinning solution between 500 to 700 cp was applicable for electrospinning. Uniform nanofibers were fabricated by 90 wt% acetic acid as the solvent, blend ratio of CS(D.D.=95%) and PEO was 95:5(w/w) as the polymer, but some drops still observed. The different preparation methods of PEO/CS/90wt%AA solution possessed different spinnability. Uniform drop-free nanofiber was fabricated by blending the PEO into the chitosan solution before spinning. Forthemore, different diameter of chitosan nanofiber in the range of 240 nm to 1050 nm can successfully fabricated by tuning degradation time of chitosan solution, M.W. of PEO, feed flow rate, and the operating voltage and working distance were not dominant. Furthermore, the biocompatibility of two different collecting amount, 20 and 100 g/cm2 of CS nanofiber membrane with mouse fibroblast(L929) and human fibroblast(H68) were compared with thin film of CS, glass and tissue culture polystyrene(PS) for cell culture in this study. The results of MTT assay show that, chitosan possess good biocompatibility for both mouse fibroblast and human fibroblast.

碩士
國立雲林科技大學
化學工程與材料工程系碩士班
101
A bilayer membrane composed of chitosan and electrospun nanofibers was prepared as a novel skin substitute. Chitosan is widely applied for wound dressings due to good biocompatibility and antibacterial property. However, cells can not attach on the surface of chitosan membrane in a short time. This study prepared various ratios of gelatin and fish collagen peptide nanofibers via electrospinning to improve cells attachment. The nanofibers consisted of different weight ratios of gelatin to fish collagen peptides (10:0 (GF100), 9:1 (GF91) and 8:2 (GF82)). The lithospermi radix was incorporated into the nanofibers to improve the antibacterial property of membranes. The nanofibers were then crosslinked with glutaraldehyde vapor to improve their structural stability in water. The compositions, surface morphology, swelling ratio, degradation rate, drug release rate and cell compatibility of materials were evaluated. The result shows that N=C bond was formed on the surface of chitosan membrane after surface treatment with glutaraldehyde vapor. The nanofibers were then fixed onto the surface of chitosan membrane via the reaction between N=C bond and nanofibers. The chitosan membrane had a high swelling ratio of 1909 wt% in water due to its porous structure. After incubation in water for 28 days, the degradation rate of chitosan membrane was about 10.5 wt%. Scanning electron microscopy (SEM) pictures revealed that the diameter of nanofibers decreased with the increase of voltage. The diameters of GF100, GF91 and GF82 nanofibers were 279.20 ± 20.00, 182.86 ± 48.67 and 206.66 ± 50.34 nm,respectively. GF82 nanofibers have a higher degradation rate than GF91 and GF100 nanofibers. Moreover, GF82 nanofibers degraded completely within 21 days. Lithospermi radix was totally released from GF82 nanofibers within 1.5 hours. However, lithospermi radix was released slowly from GF91 nanofibers. Additionally, lithospermi radix was not able to release from GF100 nanofibers. Cytotoxicity analysis demonstratrd that gelatin, fish collagen peptides and chitosan released from the membranes were not toxic to human fibroblasts. SEM pictures showed that nanofibers could enhance cells attachment. Moreover, these cells exhibited flattened morphology. These results indicates that the bilayer membrane prepared in this study has a good potential as a skin substitute.

The development of artificial structures (scaffolds), that mimic the extracellular matrix as closely as possible, and that aid in the regeneration of living tissues, has been one of the main areas of study in tissue engineering. Two-dimensional nanofibrous can be obtained by electrospinning, but three-dimensional structures are very difficult to obtain directly by electrospinning. Because of that, a group of researchers recently developed a technique called Thermally Induced Self-Agglomeration (TISA) that allows transforming two-dimensional electrospun membranes into three-dimensional structures. The objective of this work was to produce and characterize electrospun membranes of PCL/chitosan blends, to then convert them into 3D structures by TISA, followed by freeze drying. The obtained products were nanofibrous 3D scaffolds with increasing amounts of chitosan (10, 15 and 20%), highly porous (>90%) and with interconnected pores of different sizes. Compression modulus indicated compatibility for cartilage tissue engineering. The results demonstrated that the obtained scaffolds presented high similarity both in morphology and properties to the natural extracellular matrix. Therefore, its application in tissue engineering should be very promising
O desenvolvimento de estruturas artificiais (scaffolds), que imitem, o mais perfeitamente possível, a matriz extracelular, e que auxiliem na regeneração dos tecidos vivos, tem sido uma das principais áreas de intervenção em engenharia de tecidos. Arquiteturas nanofibrosas bidimensiomais podem ser obtidas por electrofiação (electrospinning), enquanto que estruturas tridimensionais são muito difíceis de obter diretamente pelo mesmo método. Posto isto, um grupo de investigadores, recentemente desenvolveu uma técnica chamada Thermally Induced Self-Agglomeration (TISA) que permite transformar membranas bidimensionais obtidas por electrofiação em estruturas tridimensionais. Este trabalho teve como objetivo, produzir e caracterizar, membranas por electrofiação de uma mistura de PCL/quitosano, para a seguir convertê-las em estruturas 3D por TISA, seguida de liofilização. Os produtos obtidos foram scaffolds 3D nanofibrosos com crescentes quantidades de quitosano (10, 15 e 20%), altamente porosos (>90%) com poros interconectados de variados tamanhos. Módulos de compressão indicaram compatibilidade para engenharia de tecidos da cartilagem. Os resultados mostraram que os scaffolds apresentavam alta similaridade tanto na morfologia como nas suas propriedades com a matriz extracelular natural e que por isso, a sua aplicação em engenharia de tecidos deverá ser bastante promissora
Mestrado em Materiais e Dispositivos Biomédicos