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Rozprawy doktorskie na temat „Biomaterials for orthopedic applications”

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Data publikacji: 6 września 2023

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1

Vidal, Girona Elia. "Development of metallic functionalized biomaterials with low elastic modulus for orthopedic applications". Doctoral thesis, TDX (Tesis Doctorals en Xarxa), 2021. http://hdl.handle.net/10803/671888.

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Titanium (Ti) and Ti alloys have been used for decades for bone implants and prostheses due to its mechanical reliability and good biocompatibility. However, implant-related infections, lack of osseointegration with the surrounding bone, and the mismatch of mechanical properties between implant and bone, remain among the leading reasons for implant failure. In the present PhD thesis, two strategies have been studied to increase implant viability: fabrication of porous Ti structures and surface functionalization. The stiffness mismatch between titanium implant and bone can cause significant bone resorption, which can lead to serious complications such as periprosthetic fracture during or after revision surgery. Titanium surface plays a major role in the bone prosthesis interactions, not only to promote initial cell adhesion but also to avoid bacterial adhesion. One strategy studied in the thesis has been the development and manufacturing of porous Ti structures. A scaffold with a porosity of 75% has been prepared by direct ink writing, with the objective of reducing the apparent modulus elasticity of Ti prostheses. In this work, porous Ti structures with a stiffness and compressive strength of 2.6 GPa and 64.5 MPa respectively has been manufactured. To this end, a new ink formulation was designed based on the mixture of a thermosensitive hydrogel with Ti irregular powder particles with a mean particle size of 22.45 μm. A thermal treatment was optimized to ensure the complete elimination of the binder before the sintering process, in order to avoid contamination of the titanium structures. The understanding of infections is closely linked to the concept of the “race for the surface”. The winner of this race (cell versus bacteria) decides if a solid anchoring between implant and bone will be achieved or if bacterial growth will lead to a periprosthetic infection. Another strategy studied on this thesis focuses on the functionalization of the Ti surface. First, surface of Ti scaffolds were functionalized with a cell adhesion fibronectin recombinant fragment for optimizing cell adhesion. Additionally, a multifunctional coating based on the potential of calcium phosphate coatings to be used as carriers for drug delivery was also studied to achieve a balance between cell attachment and reduction of bacterial adhesion. Porous Ti structures have been successfully coated with a one-step pulsed electrodeposition process achieving a uniform calcium phosphate layer both on the inner and outer the surface of the scaffold, with adhesion strengths over 22 MPa. The codeposition of an antibacterial agent with a pulsed and reverse pulsed electrodeposition was achieved on both smooth and open-cell Ti surfaces. The release rate of the antibacterial agent can be modulated within hours or days timeframe by adjusting the coating conditions and without altering the antimicrobial potential of the loaded antibacterial agent itself. The biofunctionalized coatings exhibited a noteworthy in vitro antibacterial activity against S. aureus and E. coli bacteria strains, with a significant decrease of viable attached bacteria to the treated surfaces. Cell culture tests also showed that Ti structures loaded with the antibacterial agent presented an improved cell adhesion compared to that of untreated Ti. Therefore, the proposed strategies can efficiently improve orthopedic implants in terms of improving biointegration and microbial adhesion resistance.
El titani (Ti) i els seus aliatges s'han emprat durant dècades per a implants i pròtesis òssies a causa de la seva fiabilitat mecànica i bona biocompatibilítat. Tanmateix, les infeccions relacionades amb els implants, la manca d'osteointegració amb l'os circumdant i el desajust de les propietats mecàniques entre l'implant i l'os, continuen sent els principals motius de fallida de l'implant En la present tesi doctoral, s'han estudiat dues estratègies per augmentar la viabilitat de l'implant fabricació d'estructures poroses de Ti i funcionalització superficial. El desajust de la rigidesa entre l'implant de titani i l'os pot causar una reabsorció òssia important, que pot provocar complicacions greus com la fractura periprotètica durant o després de la cirurgia de revisió . La superfície del titani té un paper important en les interaccions os-pròtesi, no només per promoure l'adhesió inicial de les cèl·lules, sinó també per evitar l'adhesió bacteriana. Una estratègia estudiada a la tesi ha estat el desenvolupament i fabricació d'estructures poroses de Ti. S'ha preparat un andamiatge amb una porositat del 75% mitjançant Direct lnk Writing, amb l'objectiu de reduir l'elasticitat del mòdul aparent de les pròtesis de Ti. En aquest treball, s'han fabricat estructures poroses de Ti amb una rigidesa i resistència a la compressió de 2,6 GPa i 64,5 MPa respectivament. Per això, es va dissenyar una nova formulació de tinta basada en la barreja d'un hidrogel termosensible amb partícules de pols irregulars de Ti amb una mida mitjana de partícula de 22,45 µm. Es va optimitzar un tractament tèrmic per assegurar l’eliminació completa de l'aglutinant abans del procés de sinterització, per evitar la contaminació de les estructures de titani. La lluita contra les infeccions està estretament lligada al concepte de "carrera per la superfície". El guanyador d'aquesta carrera (cèl·lula contra bacteris) decideix si s'aconseguirà un ancoratge sòlid entre l'implant i l'os o si el creixement bacterià conduirà a una infecció periprotètica. Una altra estratègia estudiada en aquesta tesi se centra en la funcionalització de la superfície de Ti. En primer lloc, la superfície d'andamiatges de Ti es va funcionalitzar amb un fragment recombinant fibronectina d'adhesió cel·lular per optimitzar l’adhesió cel·lular. A més, també es va estudiar un recobriment multifuncional basat en l'ús de recobriments de fosfat de calci com a portadors per a l'alliberament de medicaments per aconseguir un equilibri entre la adhesió cel·lular i la reducció de l'adhesió bacteriana. Les estructures poroses de Ti s'han recobert amb èxit amb un procés d'electrodeposició polsada d'un pas, aconseguint una capa uniforme de fosfat de calci tant a la superfície interna com exterior de les estructures, amb resistències d’adhesió superiors a 22 MPa. La co-deposició d'un agent antibacterià amb una electrodeposició polsada i polsada inversa es va aconseguir tant a les superfícies de Ti d'estructura oberta coma les llises. La velocitat de l'agent antibacterià es pot modular en un terminí d'hores o dies ajustant les condicions de recobriment i sense alterar el potencial antimicrobià del propi agent antibacterià carregat. Els recobriments biofuncionalitzats van mostrar una notable activitat antibacteriana in vitro contra les soques de bacteris S. aureus i E. coli, amb una disminució significativa de bacteris adherits viables a les superfícies tractades. Les proves de cultiu cel·lular també van demostrar que les estructures de Ti carregades de l'agent antimicrobià presentaven una millor adhesió cel·lular en comparació amb la Ti no tractat. Per tant. les estratègies proposades poden millorar els implants ortopèdics de manera eficient en termes de millora de la biointegració la resistència a l'adherència microbiana.
Ciència i enginyeria de materials
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2

Clem, William Charles. "Mesenchymal stem cell interaction with nanonstructured biomaterials for orthopaedic applications". Birmingham, Ala. : University of Alabama at Birmingham, 2008. https://www.mhsl.uab.edu/dt/2009r/clem.pdf.

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Thesis (Ph. D.)--University of Alabama at Birmingham, 2008.
Additional advisors: Yogesh K. Vohra, Xu Feng, Jack E. Lemons, Timothy M. Wick. Description based on contents viewed July 8, 2009; title from PDF t.p. Includes bibliographical references.
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3

Smith, Michael E. "Method Development for On-Site Air Quality Analysis and Design of Hydrogen Sensors for Orthopedic Applications". University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1583999801696302.

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Raghuraman, Kapil. "Synthesis and Evaluation of a Zn-Bioactive Glass Series to Prevent Post-Operative Infections in Craniofacial Applications". University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1525241500626456.

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Ahn, Edward Sun 1972. "Nanostructured apatites as orthopedic biomaterials". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8627.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2001.
Includes bibliographical references.
Historically, using suitable mechanical replacements for bone has been a priority in designing permanent, load-bearing orthopedic implants. As a result, the biomaterials used in these implants have been largely limited to bioinert titanium-based alloys, as well as to polycrystalline alumina and zirconia ceramics. However, analysis of implants incorporating these traditional biomaterials indicated that most failures involved an unstable implant-tissue interface and/or a mismatch of the mechanical behavior of the implant with the surrounding tissues. As a result, up to 20% of patients receiving permanent, load-bearing implants may undergo a revision operation. The objective of this research was to develop an alternative biomaterial that combined both mechanical resilience and an osteoconductive surface to provide a stable interface with the surrounding connective tissue so that the need for revision operations may be significantly reduced. In the effort to address the issue of mechanical strength and bioactivity simultaneously, hydroxyapatite (HAP) has generated considerable interest. Though a commonly used bioceramic, HAP has been limited by its processability. This material is sensitive to non-stoichiometry and impurities during synthesis and processing due to its complex composition and crystal structure (Ca10(P04)6(OH)2, P63/m).
(cont.) Consequently, conventionally processed HAP materials lack phase purity and homogeneity. Densification of HAP requires high temperatures that result in grain growth and decomposition into undesired phases with poor mechanical and chemical stability. To circumvent densification at high temperatures, glassy additives have been introduced to promote liquid-phase sintering at a lower temperature. However, the presence of a secondary glassy phase gave rise to poor mechanical characteristics. Hence, clinical applications of HAP have been limited to powders, coatings, porous bodies, and non-load-bearing implants. To overcome the deficiencies of conventionally processed HAP, nanostructure processing was applied, which allowed for materials design from the molecular level. By using an aqueous chemical precipitation technique, a fully dense, transparent, nanostructured HAP-based bioceramic that exhibited superior mechanical properties and enhanced tissue bonding was obtained. Processing parameters affecting the molecular and structural development of HAP were used to tailor HAP stoichiometry, crystallite size, morphology and surface chemistry for optimal thermal stability and sinterability. Unlike conventionally processed HAP, the stoichiometric, equiaxed, nanocrystalline HAP powders demonstrated significantly enhanced sinterability by fully densifying at a remarkably low temperature of 900ʻC with pressure-assisted sintering.
(cont.) Furthermore, high-resolution electron micrographs illustrated that the sintered compact possessed a uniform and ultrafine microstructure with an average grain size of -100 nm, with no glassy or amorphous interfaces along the grain boundaries. The crystallinity of the HAP grains and grain boundaries and the minimal flaw sizes could be credited for the superior strength of nanostructured HAP compared to conventional HAP. Compared to polycrystalline HAP, nanocrystalline HAP also provided greater osteoblast function. In vitro experiments indicated that nanocrystalline HAP surfaces enhanced cell attachment, proliferation and mineralization. The larger grain boundary volume resulting from the ultrafine microstructure might have enhanced protein adsorption, ...
by Edward Sun Ahn.
Ph.D.
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Devlin, Sean M. "Improving Degradable Biomaterials for Orthopedic Fixation Devices". Diss., Temple University Libraries, 2016. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/394989.

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Bioengineering
Ph.D.
Current degradable orthopedic fixation devices do not typically facilitate tissue integration during healing. Proposed here is a novel combination of processing methods to enhance the tissue integration capability of degradable thermoplastics used in temporary orthopedic fixation devices. The provision of open pores in devices used to affix reconstructed hard tissues would allow for local cells to infiltrate during the healing process. Any openly porous structure is inherently weakened in comparison to its monolithic peers (i.e. decreased relative bulk modulus), such that the matrix materials must be made more resilient in keep the device from becoming friable. These processing methods aim to improve degradable surgical fixation devices at multiple levels of design: both through the inclusion of porous morphology, processing changes, and additives to regain mechanical integrity. Biomimetic pores are added for cellular infiltration by dissolving a porogen’s interpenetrating polymer network. The addition of open pores significantly reduces the bulk stiffness. More uniform phase separation has led to better pores, but the objects still need more resilience. Carbon nanomaterials are used to improve on the mechanics and surface chemistry of the polymer matrix material, composites of polylactide/nanodiamond are produced through cryogenic milling and solid state polycondensation. The addition of minute amounts of functionalized nanodiamond has remedied the brittle failure of the material, by cryogenic milling and solid state polycondensation of poly((D,L)lactide-co-glycolide) and hydroxyl functionalized detonation nanodiamonds. This composite has also demonstrated increased cytocompatability with 7F2 osteoblasts, as analyzed by cellular adhesion through fluorescence microscopy and alamar blue assay.
Temple University--Theses
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Ensing, Geert Tone. "Prevention and treatment of biomaterial related infection in orthopedics a study of application of ultrasound and of antibiotic release /". [S.l. : [Groningen : s.n.] ; University Library Groningen] [Host], 2006. http://irs.ub.rug.nl/ppn/291344038.

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Gianforcaro, Anthony L. "Improvement Of Biodegradable Biomaterials For Use In Orthopedic Fixation Devices". Master's thesis, Temple University Libraries, 2019. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/599834.

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Bioengineering
M.S.
Current orthopedic internal fixation devices, such as pins and screws, are typically made from metals and have a long list of complications associated with them. Most notably, complications such as infection or decreased wound healing arise from revisional surgeries needed to remove the used hardware. A new class of fixation devices is being produced from biodegradable biomaterials to eliminate the need for revisional surgery by being naturally broken down in the body. While currently available polymers lack the necessary mechanical properties to match bone strength, the incorporation of small amounts of hydroxylated nanodiamonds has been proven to increase the mechanical properties of the native polymer to better resemble native bone. Additionally, modern polymers used in biodegradable fixation devices have degradation rates that are too slow to match the growth of new bone. Poly-(D, L)-lactic-co-glycolic acid (PDLG) incorporated with hydroxylated nanodiamonds has not only been proven to start out stronger, but then also helps the polymer degrade faster when compared to the pure polymer in vivo and prevents effusion of the polymer into the surrounding environment. Nanodiamond incorporation is accomplished via solid state polycondensation of PDLG to create a uniform material with increased mechanical properties, faster degradation rates, and enhanced calcification when tested in simulated body fluid.
Temple University--Theses
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Wong, Kai-lun, i 黄棨麟. "Strontium-substituted hydroxyapatite reinforced polyetheretherketone biomaterials in orthopaedic implants". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42182505.

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Wong, Kai-lun. "Strontium-substituted hydroxyapatite reinforced polyetheretherketone biomaterials in orthopaedic implants". Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B42182505.

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López, Alejandro. "Injectable Biomaterials for Spinal Applications". Doctoral thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-215606.

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The use of injectable biomaterials is growing as the demands for minimally invasive procedures, and more easily applicable implants become higher, but their availability is still limited due to the difficulties associated to their design. Each year, more than 700,000 vertebral compression fractures (VCF’s) are reported in the US and 500,000 VCF’s in Europe due to primary osteoporosis only. VCF’s can compromise the delicacy of the spinal canal and also cause back pain, which affects the patient’s quality of life. Vertebroplasty was developed in the 80’s, and has proven to be a safe minimally invasive procedure that can, quickly and sustainably, relieve the pain in patients experiencing VCF’s. However, biomaterials for vertebroplasty still have limitations. For instance, ceramic bone cements are difficult to distinguish from the bone using X-ray techniques. On the other hand, acrylic bone cements may cause adjacent vertebral fractures (AVF’s). Large clinical studies have indicated that 12 to 20% vertebroplasty recipients developed subsequent vertebral fractures, and that 41 to 67% of these, were AVF’s. This may be attributed to the load shifting and increased pressure on the adjacent endplates reached after vertebroplasty with stiff cements. The primary aim of this thesis was to develop better injectable biomaterials for spinal applications, particularly, bone cements for vertebroplasty. Water-soluble radiopacifiers were first investigated to enhance the radiopacity of resorbable ceramic cements. Additionally, different strategies to produce materials that mechanically comply with the surrounding tissues (low-modulus bone cements) were investigated. When a suitable low-modulus cement was produced, its performance was evaluated in both bovine bone, and human vertebra ex vivo models. In summary, strontium halides showed potential as water-soluble radiocontrast agents and could be used in resorbable calcium phosphates and other types of resorbable biomaterials. Conversely, linoleic acid-modified (low-modulus) cements appeared to be a promising alternative to currently available high-modulus cements. It was also shown that the influence of the cement properties on the strength and stiffness of a single vertebra depend upon the initial bone volume fraction, and that at low bone volume fractions, the initial mechanical properties of the vertebroplasty cement become more relevant. Finally, it was shown that vertebroplasty with low-modulus cements is biomechanically safe, and could become a recommended minimally invasive therapy in selected cases, especially for patients suffering from vertebral compression fractures due to osteoporosis.
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Lawson, McKinley C. "Structure-function relationships of polymerizable vancomycin derivatives for the antimicrobial surface modification of orthopedic biomaterials". Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3315775.

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Yeung, Che-yan, i 楊芷茵. "Antibacterial properties and biocompatibility of novel peptide incorporated titanium alloy biomaterials for orthopaedic implants". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hdl.handle.net/10722/197133.

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Lahiri, Debrupa. "Hydroxyapatite-Nanotube Composites and Coatings for Orthopedic Applications". FIU Digital Commons, 2011. http://digitalcommons.fiu.edu/etd/444.

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Hydroxyapatite (HA) has received wide attention in orthopedics, due to its biocompatibility and osseointegration ability. Despite these advantages, the brittle nature and low fracture toughness of HA often results in rapid wear and premature fracture of implant. Hence, there is a need to improve the fracture toughness and wear resistance of HA without compromising its biocompatibility. The aim of the current research is to explore the potential of nanotubes as reinforcement to HA for orthopedic implants. HA- 4 wt.% carbon nanotube (CNT) composites and coatings are synthesized by spark plasma sintering and plasma spraying respectively, and investigated for their mechanical, tribological and biological behavior. CNT reinforcement improves the fracture toughness (>90%) and wear resistance (>66%) of HA for coating and free standing composites. CNTs have demonstrated a positive influence on the proliferation, differentiation and matrix mineralization activities of osteoblasts, during in-vitro biocompatibility studies. In-vivo exposure of HA-CNT coated titanium implant in animal model (rat) shows excellent histocompatibility and neobone integration on the implant surface. The improved osseointegration due to presence of CNTs in HA is quantified by the adhesion strength measurement of single osteoblast using nano-scratch technique. Considering the ongoing debate about cytotoxicity of CNTs in the literature, the present study also suggests boron nitride nanotube (BNNT) as an alternative reinforcement. BNNT with the similar elastic modulus and strength as CNT, were added to HA. The resulting composite having 4 wt.% BNNTs improved the fracture toughness (~85%) and wear resistance (~75%) of HA in the similar range as HA-CNT composites. BNNTs were found to be non-cytotoxic for osteoblasts and macrophages. In-vitro evaluation shows positive role of BNNT in osteoblast proliferation and viability. Apatite formability of BNNT surface in ~4 days establishes its osseointegration ability.
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Boroujeni, Nariman Mansouri. "Monetite Cement Composites for Orthopedic and Dental Applications". University of Toledo / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1341378401.

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GOLOB, SAMUEL. "INNOVATIVE ANTIBACTERIAL SYSTEMS FOR ORTHOPEDIC AND TRAUMATOLOGY APPLICATIONS". Doctoral thesis, Università degli Studi di Trieste, 2016. http://hdl.handle.net/11368/2907984.

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Le infezioni ortopediche sono una problematica devastante che colpisce il 2% dei pazienti che si sottopongono ad interventi di sostituzione articolari. Il lavoro di ricerca di questo dottorato ha come scopo l'individuazione di sistemi tecnologicamente innovativi per la profilassi e la cura di tali infezioni.
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17

Cai, Yanling. "Titanium Dioxide Photocatalysis in Biomaterials Applications". Doctoral thesis, Uppsala universitet, Nanoteknologi och funktionella material, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-160634.

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Despite extensive preventative efforts, the problem of controlling infections associated with biomedical materials persists. Bacteria tend to colonize on biocompatible materials and form biofilms; thus, novel biomaterials with antibacterial properties are of great interest. In this thesis, titanium dioxide (TiO2)-associated photocatalysis under ultraviolet (UV) irradiation was investigated as a strategy for developing bioactivity and antibacterial properties on biomaterials. Although much of the work was specifically directed towards dental materials, the results presented are applicable to a wide range of biomaterial applications. Most of the experimental work in the thesis was based on a resin-TiO2 nanocomposite that was prepared by adding 20 wt% TiO2 nanoparticles to a resin-based polymer material. Tests showed that the addition of the nanoparticles endowed the adhesive material with photocatalytic activity without affecting the functional bonding strength. Subsequent studies indicated a number of additional beneficial properties associated with the nanocomposite that appear promising for biomaterial applications. For example, irradiation with UV light induced bioactivity on the otherwise non-bioactive nanocomposite; this was indicated by hydroxyapatite formation on the surface following soaking in Dulbecco’s phosphate-buffered saline. Under UV irradiation, the resin-TiO2 nanocomposite provided effective antibacterial action against both planktonic and biofilm bacteria. UV irradiation of the nanocomposite also provided a prolonged antibacterial effect that continued after removal of the UV light source. UV treatment also reduced bacterial adhesion to the resin-TiO2 surface. The mechanisms involved in the antibacterial effects of TiO2 photocatalysis were studied by investigating the specific contributions of the photocatalytic reaction products (the reactive oxygen species) and their disinfection kinetics. Methods of improving the viability analysis of bacteria subjected to photocatalysis were also developed.
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Heath, Daniel Edward. "Methacrylic Terpolymer Biomaterials for Cardiovascular Applications". The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1276802114.

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Miao, Tianxin. "Smart Synthetic Biomaterials for Therapeutic Applications". ScholarWorks @ UVM, 2016. http://scholarworks.uvm.edu/graddis/610.

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In the field of biomaterials, naturally-derived and synthetic polymers are utilized individually or in combination with each other, to create bio-inspired or biomimetic materials for various bioengineering applications, including drug delivery and tissue engineering. Natural polymers, such as proteins and polysaccharides, are advantageous due to low or non-toxicity, sustainable resources, innocuous byproducts, and cell-instructive properties. Synthetic polymers offer a variety of controlled chemical and physical characteristics, with enhanced mechanical properties. Together, natural and synthetic polymers provide an almost endless supply of possibilities for the development of novel, smart materials to resolve limitations of current materials, such as limited resources, toxic components and/or harsh chemical reactions. Herein is discussed the synthetic-biological material formation for cell-instructive tissue engineering and controlled drug delivery. We hypothesized that the combination of hydrogel-based scaffold and engineered nanomaterials would assist in the development or regeneration of tissue and disease treatment. Chemically-modified alginate was formed into alginate-based nanoparticles (ABNs) to direct the intracellular delivery of proteins (e.g., growth factors) and small molecular drugs (e.g., chemotherapeutics). The ABN surface was modified with cell-targeting ligands to control drug delivery to specific cells. The ABN approach to controlled drug delivery provides a platform for studying and implementing non-traditional biological pathways for disease (e.g., osteoporosis, multiple sclerosis) and cancer treatment. Through traditional organic and polymer chemistry techniques, and materials engineering approaches, a stimuli-responsive alginate-based smart hydrogel (ASH) was developed. Physical crosslinks formed based on supramolecular networks consisting of β-cyclodextrin-alginate and a tri-block amphiphilic polymer, which also provided a reversible thermo-responsiveness to the hydrogel. The hydrogel was shear-thinning, and recovered physical crosslinks, i.e., self-healed, after un-loading. The ASH biomaterials provide a platform for injectable, therapeutics for tissue regeneration and disease treatment. Indeed, various hydrogel constituents and tunable mechanical properties created cell-instructive hydrogels which promoted tissue formation.
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TARUSHA, LORENA. "Novel nanostructured biomaterials for biomedical applications". Doctoral thesis, Università degli Studi di Trieste, 2016. http://hdl.handle.net/11368/2908088.

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The research activity reported in this thesis was focused on bottom-up design, production and characterization of biomaterials in the form of medical devices for biomedical applications. More specifically, both a biomaterial for anastomosis after colorectal cancer resection, and a biomaterial for chronic non-healing wounds have been designed and developed, by exploiting the same manufacturing strategy. In the first part of the work, the research has been mainly aimed to obtain a device for preventing the leakage of the anastomosis following surgical treatment of colorectal cancer. The anastomotic leakage is a defect of the intestinal wall at the anastomotic site, which leads to a communication between the intra- and extra-luminal compartments. This study was part of the scientific activity forecasted by the European project AnastomoSEAL (FP7, c.n.280929). The project aim was to develop a patch to be wrapped around the anastomosis, capable to promote the healing of the wound. Specific biomolecules were chosen as biomaterial components. Alginate was selected for its ability to form gels thus providing the physical matrix; Hyaluronic Acid (HA) was chosen for its ability to stimulate wound healing; Butyric acid (But) was chosen since recent data demonstrated its beneficial effect on colorectal anastomosis in animal models. The last two components have been also chemically combined in the Hyaluronic Acid Butyric ester (HABut) molecule. Patches with alginate and HA were produced by using various polymer concentrations, different alginate types (algal sources), and HA with different molecular weights, in order to fine-tune the composition and the performances for the final application. Moreover, in vitro biological tests were performed on the patch components (raw materials): the effects on cell viability, proliferation and extracellular matrix production were studied on primary human fibroblasts and on a normal-derived colonocyte cell line. Additional biological in vitro tests were conducted in order to study more in depth the effect of But on colonocytes. The obtained in vitro data enabled the selection of the best performing formulation and lead to the decision to exclude the use of HABut and But from the medical device. The second part of the work was focused on a biomaterial for chronic non-healing wounds treatment. Chronic non–healing wounds are defined as wounds that do not heal in eight weeks and are characterized by a prolonged inflammation, excess of proteolytic enzymes, reduced cell proliferation and migration, and infections which further sustains these deregulations. For the development of the medical device for chronic non-healing wounds application alginate and HA were also chosen. Moreover, silver nanoparticles (nAgs) were added for their antibacterial and anti-inflammatory activity, and for their ability to inhibit proteolytic enzymes. nAgs are produced in wet conditions from silver nitrate and reducing compounds in the presence of the biopolymer Chitlac as dispersion agent. A foamed biomaterial was prepared in order to increase the ratio surface/volume and therefore to enhance the bacterial exposure to nAg. The foam has been obtained by using hydroxy-methyl-2-propyl cellulose (HPMC), a cellulose water soluble derivative already employed for this purpose in many biomedical and pharmaceutical applications. The HPMC-foamed patch was characterized by structural, mechanical and biological analysis: scanning electron microscopy (SEM) and tensile strength measurement were performed. The overall data confirmed that the biomaterial obtained is a promising material for the chronic non-healing wound application.
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21

Chan, Yee-loi. "Surface modification of NiTi for long term orthopedic applications". Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/HKUTO/record/B39557406.

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22

Chan, Yee-loi, i 陳以來. "Surface modification of NiTi for long term orthopedic applications". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39557406.

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23

Blanquer, Jerez Andreu. "Biocompatibility of new biomaterials for orthopaedic applications". Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/386500.

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L’ús de materials biocompatibles ha assolit una importància creixent en aplicacions ortopèdiques i quirúrgiques, degut a l’envelliment de la població. Els aliatges metàl·lics que s’empren actualment en medicina presenten propietats físiques i mecàniques diferents a les de l’os humà, incrementant la probabilitat de pèrdua de l’implant. Per aquesta raó, s’estan desenvolupant nous aliatges metàl·lics amb millors propietats. En aquest sentit, la present tesi té com objectiu l’anàlisi de la biocompatibilitat de nous aliatges pel seu ús en implants ortopèdics. En primer lloc, s’ha demostrat la biocompatibilitat del vidre metàl·lic massís TiZrCuPd en termes de citotoxicitat, i d’adhesió i de diferenciació d’osteoblasts. En segon lloc, s’ha avaluat l’efecte de dues modificacions de superfície, anodització electroquímica i modificació física, dels aliatges TiZrCuPd i Ti-6Al-4V sobre el comportament dels osteoblasts. En aquest cas, no hem observat cap efecte de la topografia en la proliferació, l’adhesió i la diferenciació. En tercer lloc, hem demostrat que els aliatges TiZrPdSi i TiZrPdSiNb són biocompatibles i afavoreixen l’adhesió, la proliferació i la diferenciació d’osteoblasts. Finalment, hem avaluat l’efecte electroestimulador de dos nous nanogeneradors piezoelèctrics, basats en ZnO, emprant dues línies cel·lulars implicades en la regeneració òssia (osteoblasts i macròfags). Els resultats observats indiquen que els nanogeneradors són biocompatibles i que la seva interacció amb les cèl·lules produeix un camp elèctric local que estimula la motilitat dels macròfags i l’augment de la concentració intracel·lular de Ca2+ en osteoblasts. Aquests nous materials intel·ligents presenten propietats força interessants pel seu ús en aplicacions biomèdiques. En conjunt, els resultats obtinguts en els nostres estudis contribueixen en el desenvolupament de materials per millorar la reparació i la regeneració òssia.
The use of biocompatible materials has attained an increasing importance for medical surgery and orthopaedics due to population aging. Metallic alloys currently used in bone implants have physical and mechanical properties different from those of the bone, which increases the probability of implant loosening. For this reason, new metallic alloys with better properties are being developed. In this regard, the present thesis aims to analyse the biocompatibility of new biomaterials for orthopaedic applications. First, we demonstrated the biocompatibility of TiZrCuPd bulk metallic glass in terms of cytotoxicity, and osteoblast adhesion and differentiation. Second, we assessed the effect of surface modification of TiZrCuPd and Ti-6Al-4V alloys by electrochemical anodization and physical modification on osteoblast behaviour. Differences in topography did not cause changes on osteoblasts adhesion, proliferation and differentiation. Third, we demonstrated that TiZrPdSi and TiZrPdSiNb alloys are also biocompatible and enhance osteoblasts adhesion, spreading, proliferation and differentiation. Fourth, we evaluated the electrostimulation effect of two new ZnO piezoelectric nanogenerators using two cell lines involved in bone regeneration (osteoblasts and macrophages). We observed that both nanogenerators are biocompatible and that their interaction with cells produces a local electric field that stimulate macrophages motility and the increase in intracellular Ca2+ concentration in osteoblasts. Thus, these new smart materials have interesting properties for their use in biomedical devices. Collectively, the results obtained in our studies contribute to the progress in the development of better materials for bone repair and regeneration.
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24

Venturato, Andrea. "2D and 3D applications of polymeric biomaterials". Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31045.

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The field of biomaterials has seen huge development over the past decade with enormous efforts invested in discovering materials with improved biocompatibility, application and versatility. Polymers can display many properties that make them ideal biomaterials, such as their potential flexibility, low weight, low cost and biodegradability. Moreover, they can be prepared in a wide variety of compositions and forms and be readily fabricated into various shapes and structures. Polymer microarrays represent an efficient high-throughput platform for the screening and discovery of new materials compared to conventional assays with advantages such as high-density screening, internal consistency of assays and the requirement for only small quantities of material. The first part of this thesis describes work in the area of diabetes research with a focus on how dysfunctional β-cells could be replaced by the transplantation of β-cells obtained from pluripotent stem cells. To achieve this aim, high numbers of β-cells are required. A polymer microarray screening approach was used to identify a number of polymers that promoted the attachment of pancreatic progenitor cells and enhanced cell proliferation. Multiple scale-up fabrication techniques were assessed to establish the most suitable approach and surface for long term cell culture leading to the obtainment of reproducible in situ polymerised polymer layers with enhanced binding properties toward pancreatic progenitor cells. These surfaces have the potential to support cell adhesion and proliferation and could find potential use in the industrial sector to increase the production of pancreatic progenitor cells in vitro. In the second part, efforts were made to gain a better understanding of the maturation of β-cells and their behaviour, with the development of 3D hydrogels based on the previously identified polymers. In this scenario, parameters such as stiffness and porosity were evaluated to identify the best environmental conditions to support 3D cell culturing of pancreatic progenitor cells. Several approaches were tested to generate scaffolds with suitable stiffness and porosity leading to the obtainment of scaffolds based on the previously identified polymer composition and with controlled porosity and stiffness. These scaffolds could represent a suitable environment to allow a better understanding of cell organisation and regulation. In a third avenue of work, arrays of 3D biocompatible materials, which were tailored for varying elasticity, hardness, and porosity (to provide the necessary physical cues to control cellular functions) were fabricated. In this chapter, details of the development of an array of eighty 3D double-network hydrogel features are reported. The array features can be produced as single or double networks and modulated in terms of stiffness, viscoelasticity and porosity to assess cell response to materials with a wide range of properties. The final part of the thesis describes the development and screening of polymeric materials to allow a better understanding of cell–surface interactions with various cell types. To investigate the correlation between cell attachment and the nature of the polymer, a series of random and block copolymers were synthesised and examined for their abilities to attach and support the growth of human cervical cancer cells (HeLa) and human embryonic kidney cells (HEK293T), with attachment modelled on monomer ratios, arrangement, and polymer chain length. The results of this screening showed differences between block copolymers and random copolymers in cell adhesion and provide interesting insight into the improvement of polymer coatings for cell culture.
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25

Khurshid, Z., S. Najeeb, M. S. Zafar i Farshid Sefat. "Advanced Dental Biomaterials: Chemistry, Manipulation and Applications". Elsevier, 2019. http://hdl.handle.net/10454/18383.

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No
Advanced Dental Biomaterials is an invaluable reference for researchers and clinicians within the biomedical industry and academia. The book can be used by both an experienced researcher/clinician learning about other biomaterials or applications that may be applicable to their current research or as a guide for a new entrant into the field who needs to gain an understanding of the primary challenges, opportunities, most relevant biomaterials, and key applications in dentistry.
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26

Zhao, Weiyu. "Development of Functionalized Biomaterials for Biomedical Applications". The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1594988786199951.

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Zhang, Rui. "Converting macroalgal biomass into biomaterials and applications". Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/20122.

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This thesis focused on the extraction of value-added biomaterials from brown seaweed and the potential applications of the extracted biomaterials as well as an analysis of the prospects of building a general bio-refinery pathway for brown seaweed. Microwave assisted extraction (MAE) was used as an innovative extraction method for phlorotannins extraction from brown seaweed. Comparison of the extraction efficiency of phlorotannins by means of MAE and conventional solid–liquid extraction from three species of brown seaweeds determined that an optimized MAE protocol increased yields by 70%. The antioxidant activities of phlorotannins and their thermal stabilities were determined. Phlorotannins extracted from C. flexuosum by MAE had the highest antioxidant activity. The composition of the most active phlorotannin extracts was also determined by HPLC-MS. Phlorotannins extracted from C. flexuosum were polymerised to make polymerised phlorotannin nanoparticles which were tested for their ability to remove heavy metal ions from aqueous solution. Calcium carbonate (CaCO3) and hybrid CaCO3–phlorotannin microparticles were also prepared for comparation. Polymerised phlorotannin particles showed highly efficient removal capacity of Pb2+ from aqueous solution (460mg/g of adsorbent). Compared with CaCO3 microparticles, the Pb2+ removal capacity of hybrid CaCO3–phlorotannin microparticles was increased when the initial Pb2+ concentration was below 1000 mg/L. However, at higher initial Pb2+ concentrations, the synergistic adsorption effect diminished. A cascading bio-refinery process was also developed for brown seaweed. This process sequentially extracted of several product streams including pigments, mannitol, phlorotannins, carbohydrates, alginate and residual seaweed. The proposed biorefinery process may provide the possibility of fully utilizing brown seaweed to provide both bio-materials and bio-energy.
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28

Costanza, Frankie. "Design, Synthesis and Applications of Polymer Biomaterials". Scholar Commons, 2015. https://scholarcommons.usf.edu/etd/5462.

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The emergence of antibiotic resistant bacteria has prompted the research into novel kinds of antibacterial small molecules and polymers. Nature has solved this issue with the use of cationic antimicrobial peptides, which act as nonspecific antibiotics against invading species. Herein, we have tried to mimic this general mechanism in a biocompatible and biodegradable polymer micelle based on the polymerization of naturally occurring amino acids lysine and phenylalanine linked to a PEG tether. This amphiphilic structure allows for the spontaneous collapse into stable nanoparticles in solution, which contains a hydrophilic outer layer and a hydrophobic core. Our polymers have shown activity against clinically relevant strains including Methicillin Resistant S. epidermidis, B. subtilis, K. pneumoniae, and P. aeruginosa. To further the application of our biopolymers, we have used them as drug delivery vehicles as well. First, we have used an anionic analogue based on glutamic acid to encapsulate a super hydrophobic drug Tanshinone IIA, and use it against a hepatoma bearing mouse model. Second, we have used a cationic analogue to form a complex with miRNA-139 and use it against a hepatoma bearing mouse model as well. In both cases, our PEG poly(amino acids)s have shown promising efficacy in drastically reducing the tumor size compared to the control only. Taken together, our results show that our nanoparticles have the potential to be versatile biomaterials as antibacterials as well as drug delivery vehicles in vivo.
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29

RUINI, FRANCESCA. "Chitosan based biomaterials: soft tissue engineering applications". Doctoral thesis, Politecnico di Torino, 2015. http://hdl.handle.net/11583/2602188.

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In recent years, considerable attention has been given to chitosan (CS)-based biomaterials and their applications in the field of soft tissue engineering (TE). CS is a glycosaminoglycan derived from chitin, the primary structural polymer in crustacean exoskeletons. CS is biocompatible, biodegradable, easily formed into various structures (i.e. sponges, nanofibers and films) under mild processing conditions and can be chemically modified through graft copolymerization and crosslinking. However, the rapid degradation of CS and its low mechanical strength are concerns that may limit its use in clinical applications. In the first part of the thesis, different non cytotoxic crosslinkers were used aiming at improving the structural properties of CS. Genipin (GP), γ-glycidoxypropyltrimethoxysilane (GPTMS), dibasic sodium phosphate (DSP) were selected as biocompatible CS crosslinkers as reported in literature. After a preliminary physico-chemical and mechanical characterization, the proper crosslinking compounds were selected for the development of different typologies of CS scaffolds for both human and veterinary applications. CS- based scaffolds were developed as nerve guidance channels (NGCs) and internal fillers fabrication to promote peripheral nerve regeneration in humans. Two CS based hollow NGCs were prepared and tested in vitro and in vivo (coded as CS flat membrane and bi-layer CS membrane) and a CS based nanostructured internal filler was optimized and characterized in vitro. i. CS flat membranes were prepared by solvent casting. According to the results obtained in the first part of the thesis, DSP alone (CS/DSP) or in association with the GPTMS (CS/GPTMS_DSP) were used as crosslinkers. CS crosslinked membranes showed permeation to nutrients and did not exert any cytotoxic effect on RT4-D6P2T. The higher mechanical stability of CS/GPTMS_DSP under wet state allowed to confirm the RT4-D6P2T attachment and proliferation as well as the neurite outgrowth of dorsal root ganglia (DRG) on CS substrates. Before in vivo implantation in rats, CS/GPTMS_DSP and CS/DSP membranes were easily rolled up to form a NGC. Then, membranes were used to bridge median nerve defects in rats. After 12 week post-operative CS/GPTMS_DSP tubes were found to be detached from the distal suturing site and functional recovery did not occurred. On the other hand, crushed nerve encircled with CS/DSP membranes, allowed nerve fibre regeneration and functional recovery, showing similar results to autografts. ii. Bi-layer CS membranes were developed using a two-step coating technique. CS/DSP and CS/GPTMS_DSP flat membranes were combined to produce scaffold structures with good biocompatibility in the inner layer (CS/DSP) and with the desired mechanical strength imparted by the outer (CS/GPTMS_DSP, GPTMS 25% wt./wt.). Gradual water uptake and permeation to small molecules was observed compared to single layers. From in vivo tests, median nerves treated with bi-layer tubes displayed regenerated and aligned fibres at the injury site. iii. CS crosslinked electrospun nanofibres were fabricated by electrospinning solutions containing CS, polyethylene oxide (PEO), and dimethylsulphoxide (DMSO). PEO and DMSO were introduced to allow the spinnability of CS solutions at high polymer concentration with controllable fiber size and increase fiber yields by relaxing CS chain entanglement. Optimization of the process and solution parameters allowed to obtain CS nanofibres with size of 128±17 nm. To increase CS stability in aqueous media, DSP was used as crosslinker After DSP crosslinking fibre size decreased to 109±17 nm while an increase in the mechanical strength (E, from 63±10 MPa to 113±8 MPa) was observed compared to uncrosslinked nanofibrous matrices. In the third part of the thesis, CS porous membranes with improved antimicrobial properties were prepared for veterinary application. The developed scaffolds were fabricated by freeze-drying to promote the wound healing process and to reduce the bacterial proliferation in chelonian shell injury site. Different ratios of silver nanoparticles (AgNPs, 5%, 10% and 15% wt. /wt.) and gentamicin sulphate (GS, 3.5 mg/ml) were loaded into the CS/GPTMS_DSP membranes to impart the proper antibacterial properties and to favor drug release avoiding the risk of systemic toxicity. After a preliminary in vitro characterization, CS/GPTMS_DSP loaded with AgNPs at a concentration of 10% wt./wt (CS/GPTMS_DSP_AgNP10) was selected as ideal candidate for this application field. GS release profile from CS/GPTMS_DSP_GS evidenced high burst release of the antibiotics in the first day (about 70%). Finally, GS and AgNPs (10 % wt./wt.) effect on bacterial inhibition was evaluated and confirmed against Gram+ and Gram-. The results reported in this thesis work demonstrate that CS is a promising candidate for applications in human and veterinary soft TE. Mechanical and physico-chemical properties of CS scaffolds can be tuned by using different crosslinking methods. By the in vitro characterization, GPTMS and DSP were selected as ideal compounds to the development of scaffolds for peripheral nerve regeneration (in human) and wound healing (in animals). Four different morphologies (3 for peripheral nerve regeneration and 1 for wound healing application) were obtained by varying the fabrication methods and the final composition. All membranes were found to satisfy the requirements for the application of interest. CS based membranes developed for peripheral nerve regeneration were found to be biocompatible, and successful functional recovery was observed in case of CS/DSP and bi-layer membranes. Porous membranes with improved antimicrobial properties were prepared to enhance wound healing in chelonians and were found to be effective against a broad spectrum of bacteria following the release of two different investigated antimicrobial agents (AgNPs and GS).
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Rubini, Katia <1966&gt. "Biomaterials for osteoarticular applications: role of functionalization". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amsdottorato.unibo.it/10077/1/Rubini_Katia_submitted-1-140.pdf.

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This work was focused on the development of functionalized materials with potential applications for the substitution/repair of damaged tissues. The materials utilized as substrates were calcium orthophosphates, namely hydroxyapatite, β-tricalcium phosphate, monetite and brushite, and gelatin films. This choice was based on a biomimetic strategy: the inorganic component of the hard tissues of vertebrates is a basic calcium phosphate similar to synthetic hydroxyapatite, and gelatin is a degradation product of the main proteic component of the human body, collagen. Functionalization of calcium phosphates was performed through ionic substitution, adsorption of metallic nanoparticles, organic molecules, amino and polyamino acids. The results indicated that the possibility of ionic substitution depends both on the type of calcium phosphate and of the foreign ion. Strontium substitutes for calcium up to 100at% in the structure of monetite an up to about 80at% in β-tricalcium phosphate, whereas the replacement is limited to 38at% in brushite. The maximum incorporation of zinc into β-tricalcium phosphate is much lower. Hydroxyapatites were utilized as supports for Pt nanoparticles and β-lactams. The amount of adsorbed β-lactam can reach values greater than 20wt% and depends both on the type of molecule and on the polarity of the loading solution. Adsorption of Pt nanoparticles provided materials with very good anti-oxidant properties. Both Pt nanoparticles and β-lactams displayed a controlled release over time. The interaction of aspartic acid and polyaspartic acid with brushite revealed that both molecules inhibit crystallization. However, the specific interaction of polyaspartic acid causes its adsorption up to 2.3wt%, whereas aspartic acid is not adsorbed at all. Both molecules inhibit brushite hydrolysis. Finally the properties of gelatin films were modified using two polyphenols, quercetin and curcumin, which are known for their good anti-inflammatory, anti-oxidant and anti-cancer activities. The results indicate that the functionalizing agents provide new materials with enhanced beneficial characteristics.
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31

SCOGNAMIGLIO, FRANCESCA. "Nano-engineered adhesive biomaterials for biomedical applications". Doctoral thesis, Università degli Studi di Trieste, 2016. http://hdl.handle.net/11368/2907994.

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This thesis is focused on the development of adhesive systems for biomedical applications and has been carried out in the framework of the European Project “AnastomoSEAL” (EU-FP7). Within this project, a bioactive membrane based on polysaccharides was developed for the prevention of anastomotic leakage (AL) after colo-rectal cancer (CRC) resection. The membrane was designed to be wrapped around the intestinal tissue in order to stimulate the healing of the surgical wound, thus accelerating its closure. The main components of the system were the two polysaccharides alginate and hyaluronan (HA), the former representing the physical matrix, the latter exerting a bioactive function in the terms of stimulating the healing of wounds. The main goals of this thesis were to manufacture and characterize the membranes and to design tissue-adhesives that could be implemented in the medical device. In the first part of the work, the procedure for the membrane preparation was set up, followed by the characterization of the product as to its mechanical, chemical and biological properties. The membranes were prepared by freeze-drying alginate-HA hydrogels crosslinked by calcium ions (Ca2+). Several formulations of the membrane were screened to tailor its performance in the terms of mechanical resistance, stiffness and deformation. In vitro biological test pointed out the the non-cytotoxicity of the membranes, as well as the ability of the released HA to stimulate the healing of fibroblasts. Degradation tests and release studies were performed to predict the in vivo behavior of the membrane, pointing out that, in simulated physiological conditions, the release of HA occurs during the first hours, whereas a complete degradation of the membrane is achieved in 21 days. Sterilized membranes were also characterized to investigate the effect of terminal sterilization on the membrane properties; in particular, the effect of supercritical carbon dioxide (scCO2) supplemented with H2O2 was studied. In parallel, adhesive strategies were designed and tailored to the peculiar features of both membrane and intestinal tissue. The adhesive strategies developed in this thesis were based either on the use of exogenous compounds (i.e. H2O2), or on the use of molecules displaying bioadhesive properties. In the first case, adhesion studies proved the enhancement of the adhesion strength between membrane and tissue after the treatment with H2O2, and pointed out the ability of this compound to induce the formation of an adhesive interface made of gelatin, which was integrated in the structure of the tissue. In the latter case, bio-inspired adhesive strategies were designed considering the adhesion mechanism employed by natural organisms (i.e. mussels). The key adhesive molecules of mussel’s adhesive (i.e. catechol-based compounds) were implemented into the structure of the membrane by chemical modifications. In vitro adhesion tests showed an improved adhesion of the modified-membrane in simulated physiological conditions, which was confirmed in vivo by preliminary adhesion studies. A second mussel-inspired adhesive strategy was based on the development of nanoparticles displaying a catecholic core, named melanin-like nanoparticles (MNPs). MNPs were characterized from a biological point of view and used to prepared adhesive coatings for the AnastomoSEAL membrane, whose adhesive properties were evaluated by in vitro adhesion tests. In conclusion, the tests performed allowed the development of a medical device endowed with adhesive components that enabled an efficient adhesion in a physiological environment.
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32

Rivera, Miguel A. "Powder processing of porous polysulfone for orthopedic and dental applications". Thesis, Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/10288.

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Benezra, Valarie Ilene 1971. "Electron microscopic investigation of interfaces in materials for orthopedic applications". Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9690.

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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1998.
Includes bibliographical references (leaves 214-230).
About 250,000 people undergo knee and hip arthroplasty each year in North America alone, with hundreds of thousands more receiving joints over the rest of the world. Two factors are key to the success of these implants: first, the quality of attachment of the prosthetic joint to the patient's bone, and second, the low generation of wear particles as the components of the prosthesis articulate against each other. This thesis is a study of both of these factors. First, the mechanism of bone apposition to hydroxyapatite (HA) coatings on Ti-6Al-4V was investigated via transmission electron microscopy (TEM). In this section of the study, Ti alloy cylinders were coated with HA by two different methods to yield three types of coatings - annealed and unannealed plasma-spray (PSHA) coatings and an annealed ion-beam assisted deposited (IBAD-HA) coating. These cylinders were implanted in trabecular bone in dogs from periods ranging from 3 hours to 14 days. Mechanical testing indicated that the bone/implant interface with the PSHA coated implants was significantly stronger than that with the IBAD-HA coated or uncoated Ti alloy implants. However, there were no differences in the degree of bone apposition to the three HA-coated materials; thus indicating that bone apposition is not a sufficient indicator of mechanical integrity of the bone/HA interface. In the second section of this study, the microstructural factors contributing to the observed wear properties of the oxide on Zr-2.5Nb were investigated via TEM. Zr-2.5Nb barstock which had been rotary-forged to impart an anisotropic microstructure was sectioned and oxidized in dry air at 600°C and 635°C for a variety of times ranging from 30 minutes to 40 hours. Cross-sections across the oxide/metal interface were observed via TEM. The oxide scale comprises primarily monoclinic zirconia, with small amounts of tetragonal zirconia. Evidence of a mixed oxide phase, 6Zr02.Nb205, was also observed. The microstructure of this oxide is dependent on oxidation temperature, the microstructure of the underlying metal, and oxide depth. Two oxide microstructures originating from beta-Zr grains in the alloy were also identified. A third study concerned the architecture and microstructure of naturally-derived and synthetic bone substitute materials (BSMs). While BSMs are used clinically to promote healing in large bone defects, they were useful to this study as a control for the organization of mineral in mature bone. Low voltage high resolution scanning electron microscopy (LVHRSEM) enabled observations of the three dimensional architecture of these materials which were then correlated with TEM observations. The crystallites in an anorganic bovine-derived BSM were organized in a hierarchical fashion which paralleled the organization of collagen. In contrast, the synthetic materials were organized in an isotropic network. The difference in organization was attributed to the formation of the mineral matrix of bone on an anisotropic collagen template.
by Valarie Ilene Benezra.
Ph.D.
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34

Yang, Xia. "Multi-functional Hyaluronan Based Biomaterials for Biomedical Applications". Doctoral thesis, Uppsala universitet, Polymerkemi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-224371.

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This thesis presents strategies for constructing multi-functional biomaterials based on hyaluronan (HA) derivatives for various biomedical applications, such as drug delivery, tissue regeneration, and imaging biomaterials. The aim of this study is to improve the functionalities of HA biomaterials as well as simplify the preparation procedures.  Native HA polymer contains D-glucuronic acid residue with a carboxyl group per disaccharide unit that can be easily modified by carbodiimide-mediated amidation reaction. Therefore, we have designed a series of orthogonal groups (hydrazide, carbazate, aldehyde, and thiol) that can be linked to HA under mild conditions using the carbodiimide chemistry. Multiple functionalities can be introduced to the obtained HA derivatives via chemoselective “click”-type transformations.   The modified HA derivatives were used for the preparation of either nanogel particles (NPs) or bulk hydrogels. Due to “click” character of the reactions used, structural HA transformations were performed with high fidelity on different scales including molecular (polymers), nanometer (NPs), and a visible scale (bulk hydrogels). By linking pyrene or camptothecin to hydrophilic HA backbone, amphiphilic polymers were obtained and utilized as drug delivery carriers or prodrugs, respectively. Subsequently, physically loaded drug (doxorubicin) could be released upon degradation of HA carriers, while the chemically linked camptothecin was released intact by a thiol-triggered cleavage reaction. Bisphosphonated HA (HA-BP) polymers were prepared to induce hydrogel scaffold bio-mineralization for bone regeneration application. Moreover, we could recruit strong binding capacity of bisphosphonate (BP) groups to calcium ions for the formation of physically crosslinked HA-BP gel upon simple mixing of the polymer and calcium phosphate nanoparticle components. This gel was more stable in vivo compared to hydrazone crosslinked HA gels. Furthermore, the hydrogel composed of fluorine-19 (19F) linked HA polymer was successfully observed by both 1H and 19F MR imaging.         In conclusion, the presented herein study describes new approaches for building up multi-functional biomaterials from the HA-based blocks. The utilization of carbodiimide and click chemistries along with the enzymatic degradation of HA allowed simple and efficient interconversion between HA macromolecules, nanoparticles and macroscopic hydrogels. These HA-based biomaterials show high potential for use in the fields of drug delivery, bone regeneration, and imaging techniques.
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Banwell, Eleanor Frances. "Self-assembling fibrous biomaterials for cell-biology applications". Thesis, University of Bristol, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441317.

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Hodgkinson, Tom. "Silk fibroin biomaterials for skin tissue engineering applications". Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/silk-fibroin-biomaterials-for-skin-tissue-engineering-applications(75958c4c-dacf-466f-ae6f-e8c9bb7c20b8).html.

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The limited reparative capacity of the skin and the inadequacy of conventional treatments have necessitated the development of tissue engineered skin substitutes. Several substitutes, including Integra Dermal Regeneration Template, are finding increasingly widespread application in the treatment of acute and chronic wounds. To date, these substitutes are unable to fully recreate the functionality and aesthetics of skin prior to injury. This thesis applied an integrated approach combining solution preparation, material fabrication control and biological testing to investigate electrospun silk fibroin (SF) nano-microfibrous scaffolds as potential biomimetic skin substitutes. Further to this, the improvement of the existing Integra scaffold through the incorporation of hyaluronan (HA) was assessed. Through rheological analysis of regenerated SF solutions under shear and extensional deformation a concentration regime transition at 20 wt% SF was identified. Solutions with relaxation times under 0.001 seconds were found to be unsuitable for electrospinning. The incorporation of poly(ethylene oxide) (PEO) was found to significantly increase solution relaxation times and extensional viscosity, making them much more suitable for electrospinning. Solution viscoelastic properties were shown to directly influence electrospun fibre morphology, with increases in viscosity resulting in increases in fibre diameter under stable spinning conditions. The effects of electrospinning parameters on electrospun fibre morphologies were investigated using SF-PEO blended solutions. Increased electrical field, spinneret height and decreased flow rate were found to decrease fibre diameter. In vitro assessment of the attachment, spreading, proliferation, viability and gene expression of primary human dermal fibroblasts (PHDFs) and bone marrow-derived mesenchymal stem cells (BM-MSCs) was conducted. Both PHDFs and BM-MSCs attached and proliferated with greater rapidity on fibres of the smallest diameters (~250-300 nm) with proliferation decreasing as fibre size increased until fibre diameters reached ~1200 nm. Cells were observed to be spread, with multiple attachments between fibres in scaffolds composed of ~250-300 nm diameter fibres. Cells aligned themselves to single fibres in scaffolds composed of fibres greater than 1 micrometre. HA supplementation to Integra resulted in increased proliferation, viability and migration of PHDFs. In ex vivo cutaneous wound healing models, the invasion of Integra was enhanced when scaffolds were supplemented with HA, with increased matrix deposition observed. Optimal supplementation concentrations for in vitro and ex vivo increases in cell proliferation and migration were at 1.5 – 2 mg ml-1 HA. SF electrospun scaffolds facilitated epithelial migration in ex vivo artificial wounds, with the migratory epidermis more closely resembling the structures observed in vivo. Additional preliminary investigations into the efficacy of a paste-form of Integra, Integra Flowable Wound Matrix (IFWM) were performed ex vivo, with cell invasion comparable to the conventional scaffold format. The potential for the incorporation of viable PHDFs and BM-MSCs was also investigated and keratinocyte migration was enhanced in these scaffolds. The results in this thesis provide valuable optimisation information on the development of SF electrospun scaffolds for skin engineering. Additionally, the supplementation of Integra with HA may provide a simple and effective way to enhance the performance of the scaffold in vivo.
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37

Ma, Weili. "Engineered Biomaterials for Human Neural Stem Cell Applications". Diss., Temple University Libraries, 2019. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/594172.

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Bioengineering
Ph.D.
Within the last decade, neurodegenerative diseases such as Alzheimer’s and Parkinson’s have emerged as one of the top 5 leading causes of death globally, and there is currently no cure. All neurodegenerative diseases lead to loss of the functional cells in the nervous system, the neurons. One therapeutic approach is to replace the damaged and lost neurons with new, healthy neurons. Unfortunately, this is a difficult endeavor since mature neurons are not capable of cell division. Instead, researchers are turning to neural stem cells, which are able to self-renew and be rapidly expanded before being differentiated into functional cell phenotypes, such as neurons, allowing for large numbers of cells to be generated in vitro. Controlled differentiation of human neural stem cells into new neurons has been of interest due to the immense potential for improving clinical outcomes. Adult neural stem cell behavior, however, is not well understood and the transplanted stem cells are at risk for tumorigenesis. The focus of this dissertation is the development of engineered biomaterials as tools to study human neural stem cell behavior and neurogenesis (differentiation). A novel cell penetrating peptide was developed to enhance intracellular delivery of retinoic acid, a bioactive lipid known to induce differentiation. A hydrogel platform fabricated from hyaluronic acid, a naturally-occurring polysaccharide found in brain extracellular space, was designed to serve as a biomimetic soft substrate with similar mechanical properties to the brain. The biological behavior of the stem cells was characterized in response to chemical and physical cues.
Temple University--Theses
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38

Curcio, Mariangela. "Thin coatings of biomaterials for hard tissue applications". Doctoral thesis, Universita degli studi di Salerno, 2018. http://hdl.handle.net/10556/3055.

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2016 - 2017
The goal of the present study is the production of new-generation coatings suitable for hard tissue implants, intended to decrease the healing time, limit infections and rejections and improve patients' life quality. Materials designed for implant coatings are mainly bioactive ceramics. Belonging to this class of biomaterials, hydroxyapatite (HAp), bioglass (BG) and glass-ceramic (BGC) are indicated for application in hard tissue replacement and regeneration. However the use of each one has strengths and weaknesses; therefore the attention has been focused on their peculiarity in the coating of metallic materials, suitable for hard tissue replacement. In particular, in order to overcome their drawback and enhance their strengths, possible solutions, like the adding of helpful component in the basic material or the choice of composites, have been investigated. The main technique used for the coatings production has been the Pulsed Laser Deposition (PLD). Furthermore the Electrophoretic Deposition (EPD) has been performed to produce composite biopolymer/bioceramic coatings, which cannot be accomplished by the conventional PLD. Hydroxyapatite has been deposited with IONPs (iron oxide nanoparticles). The IONPs have been previously obtained by the means of a really "green" technique, the PLAL (pulsed laser ablation in liquid). The obtaining of HAp/IONPs films has demonstrated how PLD is a successful deposition technique for the production of magnetic composite coatings. BG_Cu films have been also successfully deposited trough PLD and their bioactivity has been demonstrated by the hydroxyapatite growth on their surface during the soaking in simulated body fluid (SBF). The use of electrophoretic deposition (EPD) has allowed the coating of SS substrate with polymer/bioglass composite films. Also in this case a Cu-doped bioaglass has been used together with a protein-based polymer, zein, and the films bioactivity has been proved. RKKP (glass-ceramic) pulsed laser deposited has been proved functional coatings for celldelivery implantation and for the reduction of the corrosion of biodegradable implant. Although glass-ceramics show superior mechanical properties than bioglasses, they are still not enough for load-bearing application. Therefore, RKKP&C60 has been used as target for the deposition of composite films with improved hardness. Finally, RKKP has been modified by the adding of another component, manganese, useful for the bone regeneration, and its biocompatibility has been proved. [edited by author]
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39

Perin, Danilo. "Biomaterials for biotechnological applications: synthesis and activity evaluations". Doctoral thesis, Università degli studi di Trieste, 2010. http://hdl.handle.net/10077/3518.

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2008/2009
A biomaterial was defined as any non-living material used in a medical device that interacts with biological systems. Many different applications involve the use of biomaterials: pharmacology, controlled drug release, extracorporeal devices (contact lens, emodialysis devices, cardiopulmonary bypass oxygenators), artificial prostheses. One of the most interesting biomaterials application regards the release of nucleic acids and their derivatives as therapeutic agents. These molecules, defined as “nucleic acid base drugs” (NABDs), allows highly targeted cellular metabolism modifications. The aim of this research project concerns the characterization of biomaterials for biotechnological applications and evaluation of their activities. In particular, because of the great therapeutics and commercial interest and the delivery problems that are largely unresolved, the attention is focused on the study of new delivery systems for siRNA, proposed as model system as they represent the most common and best characterized NABD. SiRNA proved to be useful for what concerns the in-stent restenosis, pathology implying the re-occlusion of the artery due to the iper-proliferation of smooth muscle cells induced by the presence of the stent, a metal prosthesis that is applied to avoid the elastic recoil of the artery wall after balloon angioplasty. In this system, the siRNA should act as an anti-proliferative of smooth muscle cells without interfering with endothelial cells. In order to design an appropriate delivery system, it is crucial a precise structural and dimensional characterization of polymeric mesh. This purpose was achieved by the use of various techniques such as Rheology, low field NMR and Cryoporometry. Rheology allows the evaluation of the macroscopic mechanical properties of the system under investigation (Young's and shear modulus for example). Low field NMR, instead, allows evaluating the microscopic properties and, coupled to the rheology, provides an estimation of the polymeric mesh size distribution. Cryoporometry is another method to assess the mesh size distribution. In vivo release tests represent the final step of the experimental process. The polymeric system ability to carry and deliver the liposome-siRNA complexes, was tested in culture models of smooth muscle cells and endothelial cells. The attention has been focused on polymeric hydrogels, whose biocompatibility and biodegradability is well known: • Alginate (polymeric concentration 1% - 2% - 3%), crosslinked by Ca2+ or Cu2+ water solution • Pluronic™ F127 18% in water • Dextran 5% or 30% methacrylate (respectively D40MA5% and D500MA30%; polymeric concentration 5%) crosslinked by UV • Gel systems derived from benzofulvene And polymeric blends: • Pluronic™-alginate hydrogels respectively at 18% and 2% in water • Dextran methacrylate-alginate respectively at 5% and 3% in water (A3D40MA5% or A3D500MA30%)
Un biomateriale è definito come qualsiasi materiale non-vivente utilizzato in un dispositivo medico interagente con i sistemi biologici. Diverse applicazioni comportano l'uso di biomateriali: farmacologia, sistemi di controllato rilascio di farmaci, dispositivi extracorporei (lenti a contatto, dispositivi per emodialisi, ossigenatori, bypass cardiopolmonari, ecc.), protesi artificiali. Una delle applicazioni più interessanti dei biomateriali riguarda il rilascio di acidi nucleici e loro derivati come agenti terapeutici. Queste molecole, definite come " nucleic acid base drugs " (NABDs), consentono modifiche altamente mirate del metabolismo cellulare. L'obiettivo di questo progetto di ricerca riguarda la caratterizzazione dei biomateriali per applicazioni biotecnologiche e la valutazione delle loro attività. In particolare, dato il notevole interesse terapeutico e commerciale, oltre ai problemi di delivery tutt’ora in gran parte irrisolti, l'attenzione è stata focalizzata sullo studio di nuovi sistemi di somministrazione di siRNA, proposti come sistema modello in quanto rappresentano il più comune e meglio caratterizzato NABD. I siRNA si sono rivelati utili per il trattamento della ristenosi in-stent, una patologia che comporta la ri-occlusione dell'arteria in seguito alla iper-proliferazione delle cellule muscolari lisce indotta dalla presenza dello stent, una protesi di metallo applicata per evitare la contrazione elastica della parete arteriosa in seguito ad angioplastica con palloncino. In questo sistema, il siRNA dovrebbe agire come un anti-proliferativo delle cellule muscolari lisce, senza interferire con le cellule endoteliali. Al fine di progettare un adeguato sistema di rilascio, è di fondamentale importanza una precisa caratterizzazione strutturale e dimensionale delle maglie polimeriche. Questo scopo è stato raggiunto mediante l’utilizzo di varie discipline quali la Reologia, l’NMR a basso campo e la Crioporimetria. La Reologia permette una valutazione macroscopica delle proprietà meccaniche del sistema in esame (ad esempio attraverso il modulo di Young ed il modulo di taglio). L’NMR a basso campo, invece, permette di valutare le proprietà microscopiche e, accoppiato alla reologia, fornisce una stima della distribuzione dimensionale delle maglie polimeriche. La Crioporimetria è metodo alternativo per la valutazione della distribuzione dimensionale delle maglie. I test di rilascio in vivo rappresentano l'ultima fase del processo sperimentale. La capacità del sistema polimerico di trasportare e rilasciare liposomi complessati a siRNA, è stata valutata in modelli di cellule muscolari lisce e cellule endoteliali in coltura. L’attenzione e stato focalizzata soprattutto su sistemi idrogel polimerici la cui biocompatibilità e biodegradabilità è ben nota: • Alginato (concentrazione polimero 1% - 2% - 3%), reticolato attraverso soluzioni acquose di Ca2+ o Cu2+ • Pluronico F127 al 18% in acqua • Destrano 5% o 30% metacrilato (rispettivamente D40MA5% e D500MA30% ad una concentrazione polimerica pari al 5% in acqua), reticolati tramite UV • Sistemi gel derivati da benzofulvene E le miscele polimeriche costituite da: • Idrogel di pluronico-alginato rispettivamente al 18% e 2% in acqua • Destrano metacrilato-alginato rispettivamente al 5% e 3% in acqua (A3D40MA5% o A3D500MA30%)
XXII Ciclo
1980
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40

Flamant, Quentin. "Surface modification of zirconia-based bioceramics for orthopedic and dental applications". Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/436899.

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Debido a sus excelentes propiedades mecánicas y una excelente biocompatibilidad, el uso de las cerámicas de base de circona en aplicaciones dentales y ortopédicas ha crecido rápidamente durante las últimas décadas. Sin embargo, tanto la alúmina como la circona son bioinertes, lo cual dificulta su implantación en contacto directo con el hueso. Además, las infecciones siguen siendo una de las principales causas de fallo de implantes. Para resolver ambos problemas, se requiere un mejor diseño de la superficie: en particular, una topografía adecuada puede promover la osteointegración y limitar la adhesión bacteriana. Por otro lado, la fiabilidad a largo plazo es un asunto crítico para los implantes estructurales, y las cerámicas que contienen circona requieren una atención especial. Como para otras cerámicas, las alteraciones superficiales pueden comprometer sus propiedades mecánicas. Además, la transformación de fase de tetragonal a monoclínica, que les proporciona una tenacidad excepcional, puede ocurrir espontáneamente en presencia de agua, lo cual puede afectar las propiedades del material. La cinética de este fenómeno, conocido como envejecimiento hidrotérmico, es muy sensible a los cambios de procesamiento. Por lo tanto, cualquier modificación de la superficie debe ir acompañada de una evaluación de su impacto en la fiabilidad de los implantes. Basado en estas observaciones, el objetivo de esta tesis fue desarrollar procesos para modificar la superficie de los implantes a base de circona, en particular la topografía, sin comprometer sus propiedades mecánicas y estabilidad hidrotérmica. El esfuerzo de investigación se centró en dos materiales: la circona estabilizada con itria (3Y-TZP), que se utiliza cada vez más para aplicaciones dentales (por ejemplo: coronas, implantes), y la alúmina reforzada con circona (ZTA), que es el estándar actual en ortopedia para la fabricación de componentes cerámicos estructurales. Por lo tanto, este trabajo se puede dividir en dos partes principales. En la primera parte, se llevó a cabo un amplio estudio del ataque de la circona con ácido fluorhídrico (HF). Se demostró que ajustando el tiempo de decapado es posible controlar la rugosidad y la dimensión fractal de la superficie. Además, los resultados indican condiciones adecuadas para incrementar la rugosidad de forma rápida y uniforme, sin comprometer su resistencia mecánica ni tampoco su resistencia al envejecimiento. Basándose en estos hallazgos, se obtuvieron muestras con gradientes de rugosidad mediante inmersión con una velocidad controlada en una solución de ataque. Gracias a este método, que reduce drásticamente los esfuerzos y recursos necesarios para estudiar las interacciones célula-superficie, se realizó un análisis rápido de la influencia de la micro- y nano-topografía inducida por HF en las células madre mesenquimales. Se determinaron correlaciones entre parámetros de rugosidad y morfología celular, destacando la importancia de la optimización de la topografía a múltiples escalas para inducir la respuesta celular deseada. En la segunda parte, una estrategia integrada fue desarrollada para proporcionar propiedades antibacterianas y osteointegrativas a las superficies de ZTA La micro-topografía se controló mediante moldeo por inyección. Mientras tanto, un nuevo procedimiento que implica la disolución selectiva de la circona por HF (ataque selectivo) se utilizó para producir nano-rugosidad y una nanoporosidad superficial interconectada. La utilización potencial de la porosidad para la liberación de antibióticos fue demostrada, y se evidenció que la encapsulación liposomal puede aumentar la cantidad de fármaco cargada. Además, se demostró que el impacto del ataque selectivo sobre las propiedades mecánicas y la estabilidad hidrotermal era limitado. Por lo tanto, la combinación del moldeo por inyección y del ataque selectivo parece prometedora para la fabricación de componentes de ZTA implantables en contacto directo con el hueso
Due to their outstanding mechanical properties and excellent biocompatibility, the use of zirconia-based ceramics in dental and orthopedic applications has grown rapidly over the last decades. However, both alumina and zirconia are bioinert, which hampers their implantation in direct contact with bone. Furthermore, infections remain one of the leading causes of implant failure. To address both issues, an improved surface design is required: in particular, an adequate topography can promote osseointegration and limit bacterial adhesion. On the other hand, long-term reliability is a major concern for load-bearing implants, and zirconia-containing ceramics require special attention. As for other ceramics, surface alterations can impair their mechanical properties. Besides, the tetragonal to monoclinic phase transformation, which accounts for their exceptional toughness, can occur spontaneously in the presence of water, potentially deteriorating the material properties. The kinetics of this phenomenon, known as hydrothermal ageing, are highly sensitive to processing changes. Any surface modification of zirconia-containing ceramics should thus be accompanied by a careful assessment of its impact on implant reliability. Based on these observations, the objective of this thesis was to develop processes to modify the surface of zirconia-based implants, in particular the topography, without compromising their mechanical properties and hydrothermal stability. The research effort focused on two materials of particular interest: yttria-stabilized zirconia (3Y-TZP), which is increasingly used for prosthodontic applications (e.g., crowns, implants), and zirconia toughened alumina (ZTA), which is the current gold Standard in orthopedics for the fabrication of load-bearing ceramic components. Accordingly, this work can be divided into two main parts. In the first part, an extensive study of the hydrofluoric acid (HF) etching of zirconia was carried out. It was shown that monitoring etching time allows controlling the roughness and fractal dimension of the surface. Furthermore, the results indicated suitable processing conditions for a fast and uniform roughening of zirconia components, without compromising substantially their strength and ageing resistance. Based on these findings, zirconia samples with roughness gradients were obtained by immersing specimens into an etching solution with a controlled speed. Thanks to this method, which drastically reduces the efforts and resources necessary to study cell-surface interactions, a rapid screening of the influence of HF-induced micro- and nano-topography on mesenchymal stem cell morphology was conducted. Correlations between roughness parameters and cell morphology were evidenced, highlighting the importance of multiscale optimization of topography to induce the desired cell response. In the second part, an integrated strategy was developed to provide both osseointegrative and antibacterial properties to ZTA surfaces. The micro-topography was controlled by injection molding. Meanwhile a novel process involving the selective dissolution of zirconia by HF (selective etching) was used to produce nano-roughness and interconnected Surface nanoporosity. Potential utilization of the porosity for delivery of antibiotic molecules was demonstrated, and it was shown that liposomal encapsulation could improve drug loading. Furthermore, the impact of selective etching on mechanical properties and hydrothermal stability was shown to be limited. The combination of injection molding and selective etching thus appears promising for fabricating a new generation of ZTA components implantable in direct contact with bone.
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41

Koju, Naresh. "Smart Piezoelectric Calcium Phosphates for Orthopedic, Spinal-fusion and Dental Applications". University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1524047236280822.

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42

Fang, Liming. "Processing of HA/UHMWPE for orthopaedic applications /". View abstract or full-text, 2003. http://library.ust.hk/cgi/db/thesis.pl?MECH%202003%20FANG.

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Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2003.
Includes bibliographical references (leaves 128-138). Also available in electronic version. Access restricted to campus users.
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43

Woo, Gregory Lu-Yuen. "Development of novel biodegradable antimicrobial polymers for biomaterials applications". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0001/MQ40915.pdf.

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Wang, Ling. "Syntheses and applications of bisphosphonate-based biomaterials and nanomaterials /". View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202007%20WANG.

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45

Zheng, Jukuan. "Synthesis and Modification of Biomaterials for Tissue Engineering Applications". University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1427581327.

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46

Fraioli, Roberta. "Functionalization of titanium with integrin-selective ligands for orthopedic and dental applications". Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/404303.

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Despite being biocompatible and with adequate mechanical properties for application as a bone replacement material, titanium lacks osteoinductive capacity, i.e. it supports new bone growth on its surface but does not foster its formation. This may lead to failure of the implant due to poor osseointegration. Together with infection, this is in fact the main cause of failure of orthopedic and dental implants. Therefore, this thesis explores the possibility to convert titanium surface into a bioactive substrate, which is actively capable of influencing cell fate in vitro and enhance implant osteointegration in vivo. To install such bioactivity, surface chemical functionalization was chosen, since it allows for the modification of the external layer of the material, which is responsible for the interactions with the surrounding tissues, while leaving the bulk properties unaffected. Two families of extracellular matrix (ECM)-inspired integrin-binding biomolecules were tested. Integrins are the major cell surface receptor, whose main role is to mediate cell-surface interactions; thus, addressing these receptors could be beneficial to tune cell response to the surface. One type of biomolecule tested is a double-branched peptidic ligand that allows for the simultaneous presentation of the cell-adhesive RGD (Arg-Gly-Asp) motif and the synergic PHSRN (Pro-His- Ser-Arg-Asn) motif, which synergizes the RGD-mediated binding to integrin a5ß1. Alternatively, non peptidic integrin-selective ligands were tested as surface coating molecules. These highly stable ligands were designed by the group of Prof. Kessler at the Technische Universität München (TUM, Munich, Germany) to be selective for either integrins a5ß1 or avß3 and are introduced in a review paper included in the thesis. The role of both of these receptor subtypes in several bone biology events is currently matter of discussion in literature. Grafting of the ligands on titanium was either carried out via physisorption or chemical anchoring. Silanization was used to create a covalent bond between the synthetic molecules and the metallic oxide. Two cell types were used for the in vitro testing of the functionalization system: human osteoblast-like cells (SaOS-2) and mesenchymal stem cells. The testing of different combinations of biomolecule, grafting technique and cell type is the subject of the four full-papers reported in the thesis. Two of these papers also include the in vivo study of the effect of the chemical functionalization in an animal model. The thesis also includes a work focused on the merging of two surface modification techniques, namely chemical functionalization and topographical modification, to create a multifunctional titanium substrate that simultaneously addresses the problem of infection and poor osseointegration: the nanostructure of the topography acts as the bactericidal element, while the surface-grafted biomolecules give eukaryotic cell-instructive properties to the material. This work was carried out during a stay at the Centre for Cell Engineering at the University of Glasgow (Prof. Dalby, UoG, Glasgow, UK). Overall, the collection of works presented in the thesis delineates a comprehensive scenario of how chemical functionalization with ECM-inspired ligands can act as a powerful tool to tune cell behavior and, ultimately, guide the biological response at the peri-implant site.
El objetivo principal de este proyecto de tesis es la instalación de bioactividad en la superficie de titanio para implantes ortopédicos y dentales a través de un proceso de funcionalización superficial. A pesar de ser biocompatible y con buenas propiedades mecánicas para substituir el tejido óseo dañado o ausente, el titanio carece de capacidades osteoinductivas, es decir, soporta pero no favorece los procesos de formación de hueso. Esto puede llevar a la fallida del implante debido a una falta de osteointegración. Las modificaciones superficiales permiten transformar la superficie bioinerte del titanio en una superficie bioactiva que estimula la producción de hueso, sin afectar las propiedades mecánicas del material. Para lograr dicha bioactividad, en este trabajo de tesis se inmovilizaron dos familias de moléculas peptidicas inspiradas en la matriz extracelular de las células que interactúan con las integrinas, los receptores celulares más importantes que transmiten la información entre las células y su matriz. El primer tipo de biomolécula testada es una molécula ramificada, cuyas dos extremidades llevan dos motivos peptídicos distintos: el motivo de adhesión celular RGD (Arg-Gly-Asp) y el motive de sinergia PHSRN (Pro-His-Ser-Arg-Asn), que incrementa la afinidad para la integrina a5ß1, muy relevante en procesos de crecimiento óseo. La segunda familia de biomoléculas abarca dos peptidomiméticos selectivos para la integrina a5ß1 o la integrina avß3, cuyo rol en la formación de hueso es también objeto de discusión en la literatura, y que fueron sintetizados por el grupo del Prof. H. Kessler de la Technische Universität München. Para la inmovilización de las moléculas en el titanio se utilizaron dos técnicas distintas: la fisisorción, que sólo está basada en la formación de enlaces débiles electrostáticos, puentes hidrogeno, etc., y la unión covalente, más estable, mediante la silanización de la superficie metálica. Las superficies de titanio modificadas se testaron con dos tipos celulares relevantes en el contexto de la substitución de material óseo: células de osteosarcoma (SaOS-2) y células mesenquimales (hMSCs), ambas de procedencia humana. La combinación de esos factores originó cuatro estudios, tres de los cuales son reportados como trabajos publicados. Dos de esos estudios incluyen también un análisis in vivo en un modelo animal, que permitió comprobar el efecto de la funcionalización en un escenario clínico real. Finalmente, se llevó a cabo un estudio en colaboración con el Prof. M. Dalby del Centre for Cell Engineering de la University of Glasgow para combinar la funcionalización química y la nanotopografia, obteniendo así una superficie de titanio multifuncional: las nanoestructuras superficiales son bactericidas, pero carecen de propiedades adhesivas, que pueden ser proporcionadas a través de la inmovilización de motivos peptídicos. En conjunto, los resultados de esta tesis demuestran que la funcionalización química es una herramienta poderosa para optimizar la respuesta celular en la superficie del biomaterial e inducir la respuesta biológica deseada.
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Nysjö, Johan. "Interactive 3D Image Analysis for Cranio-Maxillofacial Surgery Planning and Orthopedic Applications". Doctoral thesis, Uppsala universitet, Avdelningen för visuell information och interaktion, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-301180.

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Modern medical imaging devices are able to generate highly detailed three-dimensional (3D) images of the skeleton. Computerized image processing and analysis methods, combined with real-time volume visualization techniques, can greatly facilitate the interpretation of such images and are increasingly used in surgical planning to aid reconstruction of the skeleton after trauma or disease. Two key challenges are to accurately separate (segment) bone structures or cavities of interest from the rest of the image and to interact with the 3D data in an efficient way. This thesis presents efficient and precise interactive methods for segmenting, visualizing, and analysing 3D computed tomography (CT) images of the skeleton. The methods are validated on real CT datasets and are primarily intended to support planning and evaluation of cranio-maxillofacial (CMF) and orthopedic surgery. Two interactive methods for segmenting the orbit (eye-socket) are introduced. The first method implements a deformable model that is guided and fitted to the orbit via haptic 3D interaction, whereas the second method implements a user-steered volumetric brush that uses distance and gradient information to find exact object boundaries. The thesis also presents a semi-automatic method for measuring 3D angulation changes in wrist fractures. The fractured bone is extracted with interactive mesh segmentation, and the angulation is determined with a technique based on surface registration and RANSAC. Lastly, the thesis presents an interactive and intuitive tool for segmenting individual bones and bone fragments. This type of segmentation is essential for virtual surgery planning, but takes several hours to perform with conventional manual methods. The presented tool combines GPU-accelerated random walks segmentation with direct volume rendering and interactive 3D texture painting to enable quick marking and separation of bone structures. It enables the user to produce an accurate segmentation within a few minutes, thereby removing a major bottleneck in the planning procedure.
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Hassan, S. M. Mahmudul. "Development of Novel High Strength Composite Calcium Phosphate Cement for Orthopedic Applications". University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1533212629435654.

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Fan, Dongmei. "Mesoporous silicon/biopolymer composities for orthopedic tissue engineering and drug delivery applications". [Fort Worth, Tex.] : Texas Christian University, 2008. http://etd.tcu.edu/etdfiles/available/etd-12192008-090502/unrestricted/fan.pdf.

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Zhang, Xi. "Polymer composites incorporating engineered electrospun fibres : flexible design and novel properties for biomedical applications". Thesis, Queen Mary, University of London, 2017. http://qmro.qmul.ac.uk/xmlui/handle/123456789/30904.

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Due to their unique structure and flexible choice of materials, electrospun degradable and biocompatible polymer fibres are considered to be extremely suitable for biomedical applications such as tissue engineering and drug delivery, either on their own or integrated within composites. Conventional electrospun fibre composites are typically based on non-woven mats and therefore limited to simple-curved geometries (films, membranes, etc.). For aqueous composites such as hydrogels, the hydrophobicity of the materials sometimes prohibits fibres to be easily integrated or distributed in these composites. In this thesis, a review on the topic is firstly presented in Chapter 2, introducing and discussing engineering of electrospun fibre as well as their biomedical applications. In Chapter 3, electrospun polylactide (PLA) fibres reinforced poly(trimethylene carbonate) (PTMC) composites are prepared. The composites are loaded with both continuous and short PLA fibres, achieving significant mechanical enhancement and offering opportunities to produce composites conveniently using liquid formulations. Chapter 4 presents the development of shape memory polymer composites based on a combination of PLA fibres and a PTMC matrix. By loading different amounts of short fibres with different aspect ratios or by using plasticisers, the shape memory behaviour is modulated; and composites of more complex geometries are produced. In Chapter 5, PTMC-PLA fibre composites are made into drug release system. Dexamethasone-loaded PLA fibres are integrated into a PTMC matrix, showing sustained drug release and stimulating stem cell osteogenic differentiation. This concept gives promise to loading various drugs into photo-crosslinked structures without denaturation. In Chapter 6, electrospun PLA fibres are functionalized by amphiphilic block copolymer polylactide-block-poly[2-(dimethylamino)ethyl methacrylate] (PLA-b-PDMAEMA) for the development of carboxymethylcellulose composites hydrogels. Functionalization of PLA fibres not only allows for easy integration and dispersion into the hydrogel, but also enhances the interfacial bonding between fibre and hydrogel. In the last chapter (Chapter 7), some conclusions are drawn and future works are discussed.
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