Дисертації з теми "Antimicrobial propertie"
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1
Prats, Ejarque Guillem. "Exploring the pharmacological properties of human antimicrobial ribonucleases." Doctoral thesis, Universitat Autònoma de Barcelona, 2021. http://hdl.handle.net/10803/671628.
Анотація:
Aquesta tesi s’enfoca en la caracterització estructural i funcional de les propietats biològiques de les RNases antimicrobianes de la superfamília de la RNasa A. Concretament, s’han assolit els següents objectius a curt termini:
La caracterització estructural i funcional de la RNasa 6 per cristal·lografia de raigs X, dinàmica molecular, mutagènesi dirigida i anàlisis enzimàtics destaca el paper clau de les regions remotes d’unió al substrat. A part, hem identificat un possible segon centre actiu en la RNasa 6. Finalment, un estudi evolutiu dels diversos membres de la superfamília de la RNasa A ha revelat una tendència clara, al llarg de l’evolució en vertebrats, des de la preferència de guanina cap a la d’adenina en l’arquitectura de la regió secundària d’unió a bases B2.
Al llarg del treball experimental realitzat en aquesta tesi, hem buscat la caracterització del mecanisme d’acció bactericida de les RNases, una de les principals línies de recerca del nostre grup de recerca. En aquest treball, ens hem enfocat específicament en l’optimització del pèptid antimicrobià derivat de l‘N-terminal de la RNasa 3, ECP(5-17P24-36), i en el disseny d’una RNasa quimèrica antimicrobiana (RNasa 3/1).
Respecte el pèptid ECP(5-17P24-36), s’ha optimitzat mitjançant diverses metodologies, arribant a la conclusió que el millor candidat antimicrobià és el seu enantiòmer total D-ECP(5–17P24–36). Pel que fa a la RNasa 3/1, aquesta incorpora les característiques estructurals de les RNases 1 i 3, combinant així la seva elevada activitat catalítica i bactericida, respectivament. Es va dissenyar un primer constructe amb èxit, malgrat que no presentava els mateixos nivells d’activitat bactericida que la RNasa 3. Aleshores, vam dissenyar dues versions noves de la RNasa 3/1 que incorporaven el loop C-terminal de la RNasa 3, en el qual es va identificar un motiu estructural específic associat al reclutament de l’autofagosoma. És interessant destacar la capacitat de la primera versió de la quimera RNasa 3/1 d’endarrerir l’adquisició de resistència a la colistina en un assaig evolutiu in vitro d’exposició a la colistina en cultius d’Acinetobacter baumannii.
En global, aquests resultats ajudaran a elucidar el mode d’unió a l’RNA de les ribonucleases i el seu mecanisme antimicrobià, així com la seva contribució en el sistema immunitari innat, amb prometedores aplicacions farmacològiques.Esta tesis se enfoca en la caracterización estructural y funcional de las propiedades biológicas de las RNasas antimicrobianas de la superfamilia de la RNasa A. Concretamente, se han alcanzado los siguientes objetivos en el corto plazo: La caracterización estructural y funcional de la RNasa 6 por cristalografía de rayos X, dinámica molecular, mutagénesis dirigida y análisis enzimáticos destaca el papel clave de las regiones remotas de unión al sustrato. A parte, hemos identificado un posible segundo centro activo en la RNasa 6. Finalmente, un estudio evolutivo de los distintos miembros de la superfamilia de la RNasa A ha revelado una tendencia clara, a lo largo de la evolución en vertebrados, desde la preferencia de la guanina hacia adenina en la arquitectura de la región secundaria de unión a bases B2. A lo largo del trabajo experimental realizado en esta tesis, hemos buscado la caracterización del mecanismo de acción bactericida de las RNasas, una de las principales líneas de investigación de nuestro grupo de investigación. En este trabajo, nos hemos enfocado específicamente en la optimización del péptido derivado del N-terminal de la RNasa 3, ECP(5-17P24-36), y en el diseño de una RNasa quimérica antimicrobiana (RNasa 3/1). Respecto al péptido ECP(5-17P24-36), se ha optimizado mediante varias metodologías, llegando a la conclusión que el mejor candidato antimicrobiano es su enantiómero total D-ECP(5-17P24-36). Por lo que respecta a la RNasa 3/1, esta incorpora las características estructurales de las RNasas 1 y 3, combinando así su elevada actividad catalítica y bactericida, respectivamente. Se diseñó un primer constructo con éxito, pese a que no presentaba los mismos niveles de actividad bactericida que la RNasa 3. Entonces, diseñamos dos nuevas versiones de la RNasa 3/1 que incorporaban el loop C-terminal de la RNasa 3, en el que se identificó un motivo estructural específico asociado al reclutamiento del autofagosoma. Es interesante destacar la capacidad de la primera versión de la quimera RNasa 3/1 de retrasar la adquisición de resistencia a la colistina en un ensayo evolutivo in vitro de exposición a la colistina en cultivos de Acinetobacter baumannii. En global, estos resultados ayudarán a elucidar el modo de unión al RNA de las ribonucleasas y su mecanismo antimicrobiano, así como su contribución en el sistema inmunitario innato, con prometedoras aplicaciones farmacológicas.
This thesis project focuses on the structural-functional characterization of the biological properties of antimicrobial RNases from the RNase A superfamily. Specifically, the following short-term goals have been achieved: Structural and functional characterization of RNase 6 by X-ray crystallography, molecular dynamics, site-directed mutagenesis and enzymatic analysis have highlighted the key role of remote binding subsites. Besides, we have identified in RNase 6 a putative novel secondary active site. In addition, an evolutionary study of several members of the RNase A superfamily have revealed a clear drift from guanine to adenine preference at the secondary base binding site (B2) architecture along vertebrate evolution. During this thesis’ experimental work, we have pursued the characterization of RNases’ bactericidal mechanism of action, a long-term object of study in our research group. Here, we have specifically focused on the optimisation of the antimicrobial peptide derived from RNase 3, ECP(5-17P24-36), and the design of a chimeric antimicrobial RNase (RNase 3/1). Regarding the N-terminus peptide ECP(5-17P24-36), it has been optimised by several methodologies. We have concluded the best antimicrobial candidate to be its total enantiomer, D-ECP(5-17P24-36). As for RNase 3/1, this chimera encompasses structural features from RNases 1 and 3 parental proteins to combine both high catalytic and bactericidal activities. A first construct was successfully achieved, albeit not reaching the bactericidal activity levels of RNase 3. Therefore, we designed two more versions of RNase 3/1 that incorporate the RNase 3 C-terminus loop. A specific tag motif was identified in that region associated to autophagosome recruitment. Interestingly, the hybrid chimera RNase 3/1 was able to delay the acquisition of bacterial resistance to colistin using an in vitro evolutionary exposure assay in Acinetobacter baumannii cultures. Overall, the results shed light on the elucidation of substrate binding architecture and antimicrobial mechanism of action of RNases and their contribution to the innate immune system, with promising pharmacological applications.
Universitat Autònoma de Barcelona. Programa de Doctorat en Bioquímica, Biologia Molecular i Biomedicina
2
Cai, Zhiwei. "Nouveaux matériaux à base de polyoxotitanates (POTs) dopé ou à base de complexe salicylate de titane (IV) et d'argent (I)." Electronic Thesis or Diss., Strasbourg, 2023. http://www.theses.fr/2023STRAF062.
Анотація:
Ces dernières années, le dioxyde de titane a attiré beaucoup d'attention en tant que matériau hautement stable avec une large gamme d'applications allant du pigment blanc à des applications en tant que semi-conducteur ou dispositifs photoniques de pointe. En utilisant des approches synthétiques récemment développées, la synthèse de molécules cages de type polyoxotitanate (POT, [TixOy(OR)z]) atomiquement bien définies peut être menée. Les POTs peuvent être considérés comme des modèles solubles du TiO2. Des cages dopées avec un métal M (M-POT) présentant de nouvelles propriétés peuvent être aussi préparées.Deux nouvelles cages dopées au cérium ont été synthétisées par une réaction solvothermique. Les cages [Ti28O38(OEt)38CeCl](EtOH)1,4 et [Ti8O7(OEt)21Ce](EtOH) ayant des solubilités différentes, elles vont pouvoir être séparées et caractérisées par RMN du 1H et diffraction des rayons X. Des cages POTs dopées au Fe : [Ti4(OEt)15O(FeCl)] et [FeTi14(OEt)28O14(OH)2] ont été également synthétisés.Puis après hydrolyse avec ou sans calcination, les matériaux à base de Ce ou Fe et TiO2 peuvent être obtenus. Des émulsions de ses matériaux et avec le polymère PVDC dopées au cérium ou au fer ont ensuite été déposées sur une surface de PVC. Les performances d'absorption UV et de barrière à l'eau augmentent progressivement avec l'augmentation de la quantité de matériaux déposés. Les résultats sont intéressants pour l’emploi de ces matériaux en surface d’’emballage de tablettes de médicaments, ce qui permettra d’augmenter la date de péremption de ceux-ci.La cage Eu-POT dopée avec l’Eu (III) : Ti2O(OEt)8EuIIICl(EtOH)]2 a été synthétisé, puis après hydrolyse et calcination, les propriétés de photoluminescence du matériau obtenu ont été étudiées.Enfin, un complexe AgITiIV(SC)2(HSC)(CH3CN) (SC2- = l'acide salicylique) a été préparé. Après hydrolyse et calcination, les propriétés antimicrobiennes des matériaux fabriqués ont été testé vis-à-vis avec succès du S. aureus ou de E. ColisIn recent years, titanium dioxide has attracted much attention as a highly stable material with a wide range of applications from white pigment to its applications as a semiconductor or advanced photonic devices. Using recently developed synthetic approaches, the synthesis of atomically well-defined polyoxotitanate (POT, [TixOy(OR)z]) cage molecules can be determined. POTs may be preferred as soluble models of TiO2. Cages doped with a metal M (M-POT) presenting new properties can also be prepared.Two new cages doped with cerium were synthesized by a solvothermal reaction. The cages [Ti28O38(OEt)38CeCl](EtOH)1.4 and [Ti8O7(OEt)21Ce](EtOH) having different solubilities, they will be able to be separated and characterized by 1H NMR and X-ray diffraction. The Fe-doped POTs: [Ti4(OEt)15O(FeCl)] and [FeTi14(OEt)28O14(OH)2] were also synthesized. Then after hydrolysis with or without calcination, materials based on Ce or Fe and TiO2 can be obtained. Emulsions of its materials and with the cerium-doped PVDC polymer were then deposited on a PVC surface. UV absorption and water barrier performance gradually increases with increasing amount of deposited materials. The results are interesting for the use of these materials on the packaging surface of drug tablets, which will increase their expiry date. The Eu-POT cage doped with the Eu(III): Ti2O(OEt)8EuIIICl(EtOH)]2 was also synthesized, then after hydrolysis and calcination, the photoluminescence properties of the obtained material were studied.Finally, an AgITiIV(SC)2(HSC)(CH3CN) complex (SC2- = salicylate) was prepared. After hydrolysis and calcination, the anti-microbial properties of the materials were successfully tested against S. aureus or E. Colis
3
Cinar, Dursun. "Purification and antimicrobial properties of oleuropein." Thesis, University of West London, 2009. https://repository.uwl.ac.uk/id/eprint/381/.
Анотація:
Olive leaves contain substantial amounts of phenolic substances, including the polyphenol oleuropein. This compound has been reported to possess antimicrobial properties. The purpose of this study was to develop an improved method for the extraction and purification of oleuropein from olive leaves and characterise its activity as well as the mode of action against a range of bacteria. Phenolic compounds from olive leaves were extracted in methanol and oleuropein was separated from the mixture by countercurrent chromatography (CCC). Separation was confirmed by high performance liquid chromatography. CCC processing resulted in a purity of oleuropein of 60% and this was later improved to 90% (compared to 83% in a commercially available oleuropein product). Flash chromatography was successfully introduced as an additional purification step and this eliminated some of the surfactants in the extract. Fifteen strains of bacteria and one yeast, including species commonly associated with hospital infections, were tested for their sensitivity to oleuropein in agar supplemented with oleuropein and by disc diffusion on agar media. Most of the bacteria used in this study were inhibited by oleuropein but the amount of oleuropein required for inhibition varied from 0.25 to 3.0%. The two most sensitive strains were Enterobacter faecalis and one strain of group A Streptococci in agar supplemented with oleuropein. Staphylococcus spp. were inhibited by oleuropein concentrations of 0.5 to 1.5%. Gram-negative species, such as Escherichia coli and Pseudomonas aeruginosa, the Gram-positive Micrococcus Iuteus and Bacillus subtilis as well as the fungus Candida albicans were not inhibited in the same assay. In the disc diffusion test, 10% oleuropein inhibited Gram-negatives (4-15 mm) whereas 5 and 10% oleuropein resulted in inhibition zones from 12 to 30 mm in Gram-positives and C. albicans. Four strains of S. aureus were subjected to further studies. In bacterial-time kill assays, exposure to 2% oleuropein resulted in reductions of up to 6 log cfu mL-1 in 4 hours and 6 hours for two methicillin resistant and two methicillin susceptible strains, respectively. A methicillin susceptible and a methicillin resistant S. aureus were investigated using transmission electron microscopy following exposure to 2% oleuropein. Cells of both types showed leakage of cell contents and ultimately lysis within two and four hours of exposure. Further work on leakage of cell constituents based on absorbance measurements was inconclusive due to interference by coloured compounds formed by the oxidation of oleuropein. Leakage of amino acids from cells treated with oleuropein was investigated using ninhydrin and Bradford assays. It was observed that 12 to 38% of amino acids leaked from S. aureus treated with oleuropein. The results were confirmed by sodium dodecyl acrylamide electrophoresis where several bands were absent from treated cell extracts. In addition, fluorescent microscopy of lectin labelled S. aureus cells was attempted to investigate damage of glycoproteins attached on the extracellular cell wall. Lectin binding was unsuccessful and was replaced by fluorescein isocyanate, which selectively binds to lysine groups; the latter indicated reduced fluorescence in treated cells. In conclusion this work demonstrated the application of a novel purification method based on countercurrent chromatography to obtain oleuropein with improved purity. The antimicrobial studies showed that oleuropein has the potential to eliminate bacteria. The mode of action studies showed that denaturation of proteins by oleuropein occurred, resulting in irreversible cell degradation. Oleuropein might be contemplated as a cleaning agent in envirnoments where strong acids and bases are harmful for equipment.
4
Nilebäck, Linnea. "Recombinant spider silk with antimicrobial properties." Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-102804.
Анотація:
Immobilizing antimicrobial substances onto biocompatible materials is an important approach for the design of novel, functionalized medical devices. By choosing antimicrobial substances from innate immune systems, the risk for development of resistance in pathogenic microbes is lower than if conventional antibiotics are used. Combining natural antimicrobial peptides and bactericidal enzymes with strong and elastic spider silk through recombinant protein technology would enable large-scale production of materials that could serve as functionalized wound dressings. Herein, fusion proteins with the engineered spider silk sequence 4RepCT and five different antimicrobial substances were constructed using two different strategies. In the first, the fusion proteins had a His-tag as well as a solubility-enhancing domain N-terminally to the antimicrobial agent during expression. The tags were cleaved and separated from the target protein during the purification process. The other approach provided a His-tag but no additional solubility domain. The antimicrobial agents included in the work were a charge engineered enzyme and four antimicrobial peptides herein called Peptide A, Peptide B, Peptide C and Peptide D. Four out of five fusion proteins could be expressed in Escherichia coli without exhibiting noticeable toxicity to the host. However, most target proteins were found in the non-soluble fraction. For D-4RepCT, neither soluble nor non-soluble proteins were identified. An operating strategy for expression and purification of antimicrobial spider silk proteins was developed, where the construct system providing the solubility-enhancing domain N-terminally to the antimicrobial sequence, and long time expression at low temperatures is a promising approach. The fusion proteins A-4RepCT and C-4RepCT could be produced in adequate amounts, and they proved to possess the ability to assemble into stable fibers. When incubating solutions of Escherichia coli on the functionalized silk material A-4RepCT, it showed to decrease the number of living bacteria in solution, in contrary to wild-type 4RepCT on which bacteria continued to proliferate. Initial studies of the viability of bacteria adhered to the surface of the functionalized spider silk are so far inconclusive. A larger sample size, complementary experiments and methodology optimization is needed for a proper assessment of antibacterial properties. However, preliminary results for the development of antimicrobial spider silk are positive, and the approach elaborated in this work is believed to be applicable for the construction of functional spider silk with a wide range of natural antimicrobial agents for future wound healing applications.
5
Bortolin, M. "ANTIMICROBIAL PROPERTIES OF PLATELET-RICH PLASMA." Doctoral thesis, Università degli Studi di Milano, 2014. http://hdl.handle.net/2434/233150.
Анотація:
Autologous platelet concentrates have been widely used in various medical fields in order to promote tissue regeneration. The significance behind their use lies in the presence of growth factors in platelets α-granules that enhance wound healing by promoting cell chemotaxis, proliferation and differentiation. In addition, anti-inflammatory and antibacterial properties of platelet concentrates have been recently pointed out.
In this study, the antimicrobial effect of pure platelet-rich plasma (P-PRP) was evaluated against microorganisms isolated from oral cavity, such as Candida albicans, Enterococcus faecalis, Pseudomonas aeruginosa, Streptococcus agalactiae and Streptococcus oralis.
Blood samples were obtained from healthy donors. The antibacterial activity of P-PRP, was evaluated as the minimum inhibitory concentration (MIC), determined through the microdilution two-fold serial method, and the minimum microbicidal concentration (MMC), determined by subculturing microbial samples from MIC tests to solid media.
MIC results showed that P-PRP was able to inhibit the growth of E. faecalis, C. albicans, S. agalactiae and S. oralis, but not of P. aeruginosa strains. Moreover, MMB tests showed that C. albicans was less suceptible to P-PRP than other microorganisms.
In conclusion, this study shows that, in adjunct to its well established regenerative properties, P-PRP possess an antimicrobial activity and so might represent a valuable product in the fight against infections
6
Khadambi, Tshiwela Norah. "Antimicrobial properties of phenolic compounds from sorghum." Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-03022007-164705.
7
Parr, J. A. "Antimicrobial properties of silicone quaternary ammonium compounds." Thesis, Bucks New University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375600.
8
Liu, Harris K. (Harris Ken-Ming). "New immobilized antimicrobial polyethylenimines : synthesis and properties." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/93039.
Анотація:
Thesis: S.M., Massachusetts Institute of Technology, Department of Chemistry, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references.
Surfaces modified with immobilized N-alkyl-polyethylenimines (N-alkyl-PEls) containing various alkyl groups were synthesized and tested against various pathogenic human influenza viruses to establish structure-to-virucidal activity relationships. Various physical-chemical properties of each surface were correlated with their virucidal activities to identify key antiviral surface properties. The accessibility of N-alkyl-PEI quaternary ammonium groups to influenza virus was subsequently identified as the key determinant of antiviral efficacy, as demonstrated by FITC-lysozyme surface titration. Previously used multistep syntheses to create antimicrobial surfaces by immobilizing Nalkyl- PEls were replaced with a novel aerosol-assisted plasma deposition procedure. N,N-hexyl,methyl-polyethylenimines were directly plasma-coated onto a glass surface. The resulting material was thoroughly characterized and demonstrated to be robust, scalable, bactericidal against Escherichia cofi, and virucidal against human influenza virus. Biocompatibility and bactericidal properties of N-alkyl-PEls immobilized on Boston Keratoprosthetic implants were evaluated in vivo. Surface-attached N,N-hexyl,methylpolyethylenimines exhibited inhibitory effects on Staphylococcus aureus biofilm formation, with no toxicity or adverse reactivity detected.
by Harris K. Liu.
S.M.
9
Sharma, Shagun. "Investigation of Antimicrobial Properties of Spider Silk." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1418647204.
10
Desai, Prerak T. "Antimicrobial Properties of Syringopeptin 25A and Rhamnolipids." DigitalCommons@USU, 2006. https://digitalcommons.usu.edu/etd/5526.
Анотація:
The increasing bacterial resistance to available antibiotics requires the search for new antibacterial compounds to be broadened. This study investigated the antimicrobial properties of two secondary metabolites from fluorescent pseudo monads -- syringopeptin 25A, a lipodepsipeptide produced by Pseudomonas syringae pv. syringae, and a rhamnolipid mixture produced by Pseudomonas aeruginosa. The rate of antimicrobial action was determined by monitoring the rate of uptake of propidium iodide during exposure to the compounds. Inhibition was also confirmed by the microbroth dilution method to determine the MI Cs. Both the compounds inhibited growth of Gram-positive organisms, including Mycobacterium smegmatis, staphylococci, and listeria. Inhibition of spore germination was also notable. SP 25A inhibited two multiple antibiotic strains of Staphylococcus aureus subsp. aureus and Enterococcus faecalis, while RLs failed to do so, even at 60 μg/ml. Addition of the compounds together showed a synergistic activity against Listeria monocytogenes. Neither compound was toxic to human cells in vitro at 8 μg/ml.
It is postulated that both compounds exert their antimicrobial effect by forming pores in the bacterial cell membrane, but we did not observe a relation between membrane permeabilization and inhibition of growth in each case. At sub-MIC concentrations RLs did cause pores in the membrane of L. monocytogenes, while SP 25A did not. However, RLs did not inhibit cell growth, while SP 25A completely inhibited cell growth.
To investigate these effects gene expression was monitored just before treating the cells with the antimicrobials, 30 min after treatment and 120 min after treatment. The gene expression profile was distinct when cells were treated with both the antimicrobials. SP 25A repressed genes related to cell division, intermediary metabolism, transcription, translation, and virulence genes. These effects were not produced when cells were treated with RLs, hence giving indications that even though both the antimicrobials may act on the same site (i.e. the cell membrane), the cellular response was different, which led to different phenotypes for growth.
This work indicates that SP 25A holds promise for further development as a therapeutic agent and provides evidence that the proposed pore-forming model alone does not suffice to explain the mode of action of SP 25A.
11
Mwangi, Henry Maina. "Phytochemical and antimicrobial studies on Rhus natalensis." Thesis, University of the Western Cape, 2011. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_3552_1365671232.
Анотація:
Extracts from the root bark, stem bark, and leaves of R. natalensis were screened for antibacterial activity against standard bacterial strains
Staphylococcus aureas, Escherichia coli and Pseudomonas aureginosa, and fungi
Candida albicans, Trichophyton mentagrophytes or Microsporum gyseum. Chromatographic techniques were utilized to isolate pure compounds. This study validates and documents, in a systematic way, the antimicrobial properties of the R. natalensis used for many years by many people of the world. It also provides valuable information for
further phytochemical isolation and characterization studies of active compounds, necessary for the development of new drugs. The extractions were carried out using broad spectrum of solvents
(hexane, dichloromethane, ethyl acetate, and methanol). Fractionation was done using standard chromatographic techniques. A total of seven (7) compounds were isolated from R. natalensis.
Three of the isolates were characterized and their structures were unambiguously established by detailed spectroscopic analysis that involved high resolution mass spectrometry, 1D and
2D-NMR spectral data experiments 1H, 13C, DEPT, COSY, HMBC, and NOESY. These compounds are: 3-(1-(2,4-dihydroxyphenyl)-3,3-bis(4- hydroxyphenyl)-1-oxopropan-2-yl)-7-methoxy- 4H-chromone-4-one (39), Rhuschromone, a
novel compound isolated for the first time, 2&rsquo
,4&rsquo
-dihydroxychalcone-(4-O-5&rsquo
&rsquo
&rsquo
)-4&rsquo
&rsquo
,2&rsquo
&rsquo
&rsquo
,4&rsquo
&rsquo
&rsquo
- trihydroxychalcone (40) and 3-((Z)-heptadec-13-enyl) benzene- 1,2-diol (41), an urushiol. Compound 39 recorded the highest activity zone of inhibition (21mm) against S. aureas, which was found to be 50% as active the chloramphenicol standard used. The
traditional use of the extracts in infections and inflammatory conditions is rationalized based on the content of theisolated compounds, and it has been proposed that the total crude extract, with its
contents of so many bioactive compounds, could be formulated for use in many infections, microbial or fungal. Furthermore, not all of the species studied to date have been fully characterized
for potential bioactivities. Thus, there remains a significant research gap spanning the range from lead chemical discovery through process development and optimization in order to better
understand the full bioactive potential of many of these plants.
12
Gule, Nonjabulo Prudence. "Electrospun antimicrobial and antibiofouling nanofibres." Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/18057.
Анотація:
Thesis (PhD)--Stellenbosch University, 2011.ENGLISH ABSTRACT: The main objective of this study was to develop electrospun nanofibres with both antimicrobial and antibiofouling properties for possible application in water filtration. To do this, two routes were investigated: firstly, the use of biocides and bactericidal copper salts to introduce bactericidal properties on electrospun nanofibres. Secondly, the modification of polymers using furanone compounds to obtain nanofibres with the ability to repel microbial attachment. Fabrication of biocide-containing PVA nanofibres was successful. This was achieved through direct doping of PVA solutions with AquaQure which is an aqueous biocide comprising of mainly Cu2+ and Zn2+, prior to the electrospinning process coupled with chemical crosslinking using glyoxal. The conventional needle based electrospinning technique was used to fabricate these nanofibrous mats. The presence of the constituents of AquaQure on surfaces of PVA/AquaQure nanofibrous mats was confirmed using energy dispersive x-ray analysis (EDX). ATR/FTIR, XRD, TGA, DSC and SEM techniques were used to do chemical and thermal analysis of the nanofibres in comparison with pristine PVA nanofibres. These nanofibres demonstrated antimicrobial activity of up to 5 log against the Gram-positive strain S. aureus Xen 36 and Gram-negative strains E. coli Xen 14, S. typhimurium Xen 26, P. aeruginosa Xen 5 and K. pneumoniae Xen 39. Because of crosslinking, these fibres also demonstrated good water stability. Leaching of the ions constituting AquaQure was limited and compared with South African national standards for drinking water, the water filtered through these nanofibress was deemed safe for human consumption. Bioluminescence imaging and fluorescence microscopy were used to confirm antimicrobial activity results obtained from plate counting. These nanofibres demonstrated satisfactory antimicrobial efficiency but did not repel microbial attachment. The second part of this study entailed the investigation of copper-doped PVA and SMA nanofibres for antimicrobial activity. Although bactericidal properties of copper are well documented, its selection was based on the fact that it is the main constituent of the AquaQure. Bubble electrospinning was used instead of needle electrospinning to upscale nanofibre production. Similar techniques as those used in PVA/AquaQure nanofibres were used to characterize the copper functionalized nanofibres. Even though these nanofibres demonstrated exceptional antimicrobial efficacy (up to 5 log) for all the strains, bioluminescence imaging indicated a trend for these cells to enter a dormant state on contact with the copper containing-nanofibres. The last part of this project involved testing of free furanone compounds as well as surface-tethered furanone-modified nanofibres for their antibiofouling potentials. To do this, blends of 2,5-dimethyl-4-hydroxy-3(2H)furanone (DMHF) (5% wt/vol) with PVA (10% wt/vol) were prepared and electrospun to produce PVA/DMHF nanofibres. The free furanones and furanone-modified nanofibres demonstrated not only antibiofouling properties but also antimicrobial activity. Other furanone compounds with 3(2H) and 2(5H) cores were synthesized. The synthesis of these furanone compounds (5-(2-(2-aminoethoxy)ethoxy)methyl)-2(5H)furanone and 4-(2-(2-aminoethoxy)-2,5-dimethyl-3(2H)-furanone) was successful. Their structures and molar masses were confirmed using 1H NMR and ES mass spectroscopy. These furanones were then covalently immobilized on the SMA backbone. To test their antimicrobial and antibiofouling activity, the furanone-modified polymer was dissolved in an ethanol and methanol mixture (1:1) and electrospun to produce nanofibres. The free furanone and furanone-modified SMA nanofibres derived from 4-(2-(2-aminoethoxy)-2,5-dimethyl-3(2H)-furanone demonstrated high antibiofouling and antimicrobial efficiency against the Gram-positive strain S. aureus Xen 36 and Gram-negative strains E. coli Xen 14, S. typhimurium Xen 26, P. aeruginosa Xen 5 and K. pneumoniae Xen 39. The 2(5H) furanone on the other hand had limited activity against the strains. These nanofibres were also characterized and compared with their pristine polymer counterparts and leaching experiments were conducted using GC-MS.
AFRIKAANSE OPSOMMING: Die hoofdoel van hierdie studie was om nanovesel filtrasie nanofibre met beide antimikrobiese en aanpakwerende eienskappe te ontwikkel. Twee verskillende metodes is ondersoek. Eerstens is biosiede en bakteriee-dodende koper soute gebruik om antimikrobiese nanovesels te lewer. Tweedens is nanovesels met furanoon samestellings gemodifiseer om nanovesels te lewer wat mikrobiese aanhegting voorkom. Die fabrisering van biosied-bevattende PVA nanovesel nanofibre was suksesvol. AquaQure, ‟n biosied wat hoofsaaklik uit Cu2+ en Zn2+ bestaan, is direk by PVA oplossings gevoeg voor die elektrospin proses, en is gevolg deur chemiese kruisbinding deur middel van “glyoxal”. Die nanovesels is neergele in ‟n ongeweefde mat deur middel van die konvensionele naald-gebasseerde elektrospin proses. Verspreidings X-staal analises (EDX) is gebruik om die teenwoordigheid van AquaQure komponente in en op die oppervlakte van die PVA/aquaqure nanovesel matte te bevestig. ATR/FTIR, UV-Vis, XRD, TGA, DSC en SEM tegnieke is gebruik vir chemiese en termiese analises om sodoende PVA/aquacure nanovesels met ongemodifiseerde PVA nanovesels te vergelyk. PVA/aquacure nanovesels het ‟n antimikrobiese aktiwiteit van tot 5 log reduksie getoon teen Gram-positiewe S. aureus Xen 36 en Gram-negatiewe E. coli Xen 14, S. typhimurium Xen 26, P. aeruginosa Xen 5 en K. pneumoniae Xen 39. Die vesels was stabiel in water na kruisbinding. Slegs beperkte uitloging van Aquaqure Cu2+ en Zn2+ ione is waargeneem, en water wat deur die PVA/aquacure nanovesels gefiltreer is, is volgens Suid Afrikaanse Nasionale Standaarde vir drinkwater steeds veilig vir menslike gebruik. Behalwe vir die plaat-tellingsmetode het bio-lumiserende fotos en fluoroserende mikroskopie ook die antimikrobiese aktiwiteit van die vesels bevestig. Die vesels het bevredigende antimikrobiese efektiwiteit getoon, maar kon nie mikrobiese aanhegting voorkom nie. In die tweede gedeelte van die werk is die antimikrobiese aktiwiteit van PVA en SMA vesels wat met koper verreik is, ondersoek. Alhoewel die bakteriee dodende eienskappe van koper reeds goed gedokumenteer is, is hierdie ondersoek gedoen op grond van die feit dat koper een van die hoof komponente van aquaqure is. Nanovesels is uit koper-verreikte oplossings van PVA en SMA deur middel van die borrel-gebasseerde elektrospin tegniek gefabriseer, ten einde die opbrengs van nanovesels te verhoog. Fisiese kruisbinding deur middel van hitte behandeling is toegepas ten einde die stabiliteit van die vesels in water te verbeter. Dieselfde karakteriseringstegnieke wat gebruik is vir die PVA/aquacure vesels is op hierdie vesels toegepas. Alhoewel die vesels uitstekende antimikrobiese aktiwiteit van tot 5 log reduksie gedemonstreer het, het bio-lumiserende beeldvorming getoon dat die selle ‟n dormante stadium binnegaan na kontak met hierdie vesels. In die laaste gedeelte van die projek is vrye furanoon samestellings en nanofibre met oppervlak-gehegde furanone getoets vir aanpakwerende potensiaal. Om dit te bewerkstellig was „n mengsel van 2,5 – dimethyl-4-hydroxy-3(2H) furanone (DMHF) (5% wt/vol) en PVA (10% wt/vol) voorberei en gebruik om PVA/DMHF nanovesel filtrasie nanofibre te produseer deur middel van die elektrospin proses. Die vrye furanone en furanoon-gemodifiseerde nanofibre het nie alleen aanpak weerstandbiedende einskappe gedemonstreer nie maar ook antimikrobiese eienskappe. DMHF was gebruik as die begin material om furanoon samestellings te produseer met 3(2H) en 2(5H) kerne. Die sintesis van hierdie furanone se samestellings (5-(2-(2-aminoethoxy)ethoxy)methyl)-2(5H)furanone en 4-(2-(2-aminoethoxy)-2,5-dimethyl-3(2H)-furanone) was suksesvol. Hulle strukture en molere massas was bevestig met 1H NMR en ES massa spektrometrie. Hierdie furanone is daarna kovalent ge-immobiliseer op die SMA rugbeen. Om hulle antimikrobiese en aanpakwerende aktiwitiet te toets, is die furanoon-gemodifiseerde polimeer opgelos in „n etanol en metanol mengsel (1:1) en ge-elektrospin om nanovesel filtrasie nanofibre te produseer. Die furanone en furanoon-gemodifiseerde nanovesel filtrasie nanofibre afkomstig van 4-(2-(2-aminoethoxy)-2,5-dimethyl-3(2H)-furanone het hoe aanpakwerende en antimibrobiese effektiewitiet getoon teenoor die Gram-positiewe S. aureus Xen 36 en Gram-negatiewe E. coli Xen 14, S. typhimurium Xen 26, P. aeruginosa Xen 5 and K. pneumoniae Xen 39. Hierdie nanovesel filstrasie nanofibre is ook gekarakteriseer en vergelyk met die ongemodifiseerde polimeer. „n Uitlogings eksperiment is uitgevoer deur gebruik te maak van GC-MS.
13
Rodrigues, Maria do Livramento Linhares. "Tilapia skin Gelatin: Alternative for obtaining films with antimicrobial property by nanosilver incorporation." Universidade Federal do CearÃ, 2015. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=14546.
Анотація:
CoordenaÃÃo de AperfeiÃoamento de NÃvel SuperiorAn alternative for the recovery of industrial fish waste is the production of films, which can be applied in food packaging. However, a major challenge is to obtain films with antimicrobial properties aiding in increased food shelf life as well as films with good mechanical properties and barriers. Therefore, in order to improve these limitations, silver nanoparticles were used due to its potential antimicrobial in food, and tannic acid (TA) as crosslinker in order to improve the mechanical and barrier properties. This study focuses in the extraction of gelatin from the Nile tilapia skin (Oreochromisniloticus) in order to produce gelatin films with embedded nanosilver (AgNPs) generated by green process and evaluate the addition of tannic acid (TA) in synthesis of AgNPs and mechanical properties of the films and barrier. A pre-treatment was conducted to obtain gelatin followed by a collagen denaturing. The characterization was done by gel strength, isoelectric point, electrophoretic analysis, fourier transform infrared (FTIR) and thermogravimetric analysis (TGA). The incorporation was performed by in situ method, the films were obtained with and without the presence of TA and AgNO3 concentrations were 0, 45, 90 and 180 mmol.L-1.The films were characterized by UV-Vis, FTIR, TGA, Mechanical properties (tensile strength and elongation at break), water vapor permeability (WVP), scanning electron microscopy (SEM) and antimicrobial analysis. It was possible to use gelatin as a reducing agent and stabilizer in the reduction of silver nanoparticles. Films produced with the addition of AT showed more suitable properties for the usage as packaging material for food, showing better WVP, water solubility and were more resistant to applied loads. In addition, they presented better antimicrobial activity. Therefore, it was possible to obtain the green AgNPs method through the incorporationof thegelatin matrix and to obtain films with excellent properties after the TA addition.
Uma alternativa de valorizaÃÃo de resÃduo de pescado produzidos por indÃstrias à a produÃÃo de filmes, que pode ser aplicados em embalagens para alimentos. PorÃm, um dos grandes desafios à obter filmes com propriedades antimicrobianas, auxiliando no aumento da vida de prateleira dos alimentos, bem como obter filmes com boas propriedades mecÃnicas e de barreiras. Para isso, a fim de melhorar essas limitaÃÃes, nanopartÃculas de prata foram utilizadas devido a sua potencial aÃÃo antimicrobiana em alimentos, e Ãcido tÃnico (AT) como agente reticulante a fim de melhorar as propriedades mecÃnicas e de barreiras. Nesse estudo objetivou-se fazer a extraÃÃo da gelatina a partir de pele de tilÃpia do Nilo (Oreochromis niloticus), visando a produÃÃo de filmes de gelatina incorporados com nanopartÃculas de prata (NPAg) geradas por processo verde e avaliar a adiÃÃo de Ãcido tÃnico (AT) na sÃntese das NPAg e nas propriedades mecÃnicas e de barreira dos filmes. Para a obtenÃÃo da gelatina foram feitos prÃ-tratamentos e em seguida a desnaturaÃÃo do colÃgeno. A caracterizaÃÃo foi feita por ForÃa de Gel, Ponto IsoelÃtrico, DistribuiÃÃo de Massa Molar, Espectroscopia no Infravermelho pro Transformada de Fourrier (FTIR) e AnÃlise TermogravimÃtrica (TGA). A incorporaÃÃo foi feita pelo mÃtodo in situ, Os filmes foram obtidos sem e com a presenÃa de AT e as concentraÃÃes de AgNO3 foram 0, 45, 90 e 180 mmol.L-1. Os filmes foram caracterizados por: UV-Vis, FTIR, TGA, Ensaios MecÃnicos, Permeabilidade ao Vapor de Ãgua (PVA), Microscopia EletrÃnica de Varredura (MEV) e AnÃlise Antimicrobiana. Foi possÃvel utilizar a gelatina como agente redutor e estabilizante na reduÃÃo de nanopartÃculas de prata. Os filmes produzidos com a adiÃÃo de AT apresentaram propriedades mais adequadas para uso como embalagem para alimentos, apresentando melhores PVA, solubilidade em Ãgua e mostraram-se mais resistentes a esforÃos aplicados. AlÃm de apresentarem melhor atividade antimicrobiana. Logo, foi possÃvel, obter pelo mÃtodo verde a incorporaÃÃo de NPAg na matriz de gelatina, alÃm, de se obter filmes com excelentes propriedades apÃs a adiÃÃo de AT.
14
Page, Kristopher. "Photocatalytic thin films : their characterisation and antimicrobial properties." Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/17547/.
Анотація:
This thesis is concerned with the synthesis and characterisation of TiO2 based photocatalyst thin films and the assessment of their antimicrobial properties. When exposed to light of wavelength less than 380 nm TiO2 films can demonstrate self-cleaning and self-disinfecting properties. This is due to photocatalytic processes occurring on the film surface resulting in film superhydrophilicity and reactive oxygen species (ROS) production. These ROS and radicals readily oxidise organic pollutants and microbes adherent to the material surface. Consequently, TiO2 thin films are of great research interest as self-cleaning, antimicrobial coatings. TiO2 and doped TiO2 materials were prepared by a simple sol-gel route from titanium n-butoxide as the principle precursor material. Film deposition was carried out using a dip-coating technique, with substrates withdrawn from the precursor sol at a fixed speed. Deposited films were calcined to produce crystalline thin films, with excellent adherence to the substrate (glass slides). Films were characterised using a number of analytical techniques including UV-visible spectroscopy, X-ray diffraction, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy and EXAFS/XANES. Photocatalysis and film hydrophilicity were investigated using established methods. Stearic acid photodegradation, monitored by FT-IR was used to assess film photocatalysis, by monitoring the peak areas of the C-H stretching region. Relative film hydrophilicities were determined by measuring the contact angle of a sessile droplet of water. Antimicrobial properties of the films were assessed with typical examples of Gram- positive and Gram-negative organisms. Staphylococcus aureus (NCTC 6571) and Escherichia coli (NCTC 10418) were selected. Films demonstrated microbicidal activity against both organisms under 365nm UV illumination, and under illumination by a typical hospital lamp (28W 2-D fluorescent). Microbial adhesion to various substrates was also examined, using a dip-blot method. Films produced in this study demonstrate excellent potential as durable surface coatings with significant antimicrobial activity against microbes of clinical importance.
15
Wallock-Richards, Daynea Juaneckah. "Natural products : biosynthesis, antimicrobial properties and protein targets." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/14188.
Анотація:
The diversity of biosynthetic pathways in prokaryotes and eukaryotes has led to numerous bioactive natural products (NPs) which occupy a vast chemical space. Despite the current challenges in NP research, these molecules are still relevant today as they are a major source of human medicine as well as being useful biological tools. The elucidation of their biosynthetic pathways has also provided information about the biochemical and biophysical properties of fascinating enzyme families such as the α- oxoamine synthases (AOSs). The AOSs are an expanding group of pyridoxal 5’- phosphate (PLP)-dependent enzymes, which are involved in the biosynthesis of several important NP, including those essential for life. This study reports the characterization and structural analysis of a unique AOS denoted as TamD from Pseudoalteromonas tunicata. This enzyme plays a major role in tambjamine biosynthesis and consists of both an acyl carrier protein (ACP) domain and a PLP-binding catalytic domain. UV/vis spectroscopy and mass spectrometry (MS) of the recombinant TamD purified from E. coli revealed that the enzyme forms a Schiff base with PLP via Lys380, which is responsible for its characteristic yellow colour. It binds L-serine as a natural substrate with a Kd of 5.01 ± 0.64 mM. This thesis also reports structural data for TamD from xray crystallography at a resolution of 4.98 Å, which shows four molecules in the asymmetric unit (ASU) suggesting the enzyme exist as a dimer. The absence of the Nterminal region where the ACP domain is located in the crystal strucuture also suggests intrinsic flexibility and disorder within that region. With the increasing demand for new anti-infective therapies, investigations of the molecular interactions between NPs and their protein targets are vital in understanding the inhibition or activation properties of these molecules. The cysteine transpeptidases known as sortases produced by Gram positive bacteria have been identified as attractive targets for NP inhibitors. In this thesis, the molecular basis for the inhibition of Streptococcus mutans sortase A (SrtA) by the plant flavonoid, trans-chalcone is explored, using a combination of MS, enzyme kinetics, molecular modelling and x-ray crystallography. This study reports the first high resolution crystal structure of the H139A mutant of S. mutans SrtA, which reveals a unique N-terminal α-helix domain. Trans-chalcone was found to inhibit the in vitro activity of S. mutans SrtA in a slow, tight–binding manner, with a half maximal inhibitory concentration (IC50) of 5.0 ± 0.6 μM. The interaction resulted in a covalent adduct with the active site cysteine residue (Cys205) via a Michael addition mechanism. Additionally, trans-chalcone showed evidence of S. mutans anti-biofilm activity in a concentration dependent manner up to 250 μM with an efficacy cut-off point at higher concentations. These results indicate that chalcone flavonoids are worth further investigation as potential antibiofilm inhibitors. A renewed interest in plant NPs has also led to a collaborative investigation on the antimicrobial potential of garlic-derived allicin, against Burkholderia cepacia complex (Bcc), the major bacterial phytopathogen for alliums and an intrinsically multiresistant and life-threatening human pathogen. Allicin is the principal antibacterial agent in fresh preparations of garlic extracts. This investigation reports the first evidence that allicin and allicin-contaning garlic extracts possess inhibitory and bactericidal activities against Bcc. The minimum inhibitory concentrations (MICs) of aqueous garlic extract (AGE) against 38 Bcc isolates ranged from 0.5 to 3% (v/v). An investigation into the possible molecular mechanisms of allicin with a recombinant thiol-dependent peroxiredoxin (BCP) from B. cenocepacia revealed that allicin and AGE modify an essential BCP catalytic cysteine residue and suggests a role for allicin as a general electrophilic reagent that targets protein thiols. Present therapeutic options against these life-threatening pathogens are limited; thus, allicin-containing compounds merit further investigation as adjuncts to existing antibiotics.
16
Oriani, Vivian Boesso 1986. "Desenvolvimento e caracterização de coberturas comestíveis à base de fécula de mandioca adicionadas de óleos essenciais." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/255153.
Анотація:
Orientador: Miriam Dupas HubingerDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
Made available in DSpace on 2018-08-22T05:48:31Z (GMT). No. of bitstreams: 1 Oriani_VivianBoesso_M.pdf: 12741078 bytes, checksum: 5f41652e5d2d38885c526edf6c2e0cf7 (MD5) Previous issue date: 2013
Resumo: Coberturas comestíveis foram desenvolvidas e caracterizadas pela combinação de fécula de mandioca (2 e 3% p/v) com óleos essenciais de casca de canela (Cinnamomum zeylanicum) (0,05 a 0,30% v / v) ou de erva doce (Foeniculum vulgare L.) (0,05-0,30 % v / v). A adição do óleo teve como propósito desenvolver uma cobertura com propriedades antimicrobianas, antioxidantes e com capacidade de barreira ao vapor de água, já que os óleos essenciais têm característica hidrofóbica. Foram avaliados estabilidade física, tamanho de gota e viscosidade das coberturas comestíveis emulsionadas e os filmes foram caracterizados através das propriedades mecânicas, solubilidade e microscopia de força atômica. As coberturas emulsionadas com 2% de fécula de mandioca mostraram-se estáveis e as de 3% de fécula apresentaram separação da água do sistema emulsionado. A cobertura foi feitas em fatias de maçãs para o teste de resistência ao vapor de água e medida da taxa de respiração. A formulação com a concentração máxima dos dois óleos essenciais, em ambas as concentrações de fécula de mandioca, resultou em aumento da resistência ao vapor de água. A taxa respiratória das fatias de maçãs com cobertura mostrou efeito de barreira ao CO2 em relação aos frutos sem cobertura. As análises de propriedades mecânicas e microscopia de força atômica dos filmes mostraram que as películas com óleo essencial de casca de canela podem ter apresentado descontinuidade da matriz formadora de filmes. As coberturas com óleo essencial de casca de canela apresentaram efeito significativo para a atividade antioxidante. O teste de halo de inibição dos microrganismos mostrou que a formulação com 0,3% de óleo essencial de casca de canela apresenta uma pequena inibição para Staphylococcus aureus e Salmonella choleraesius
Abstract: Edible coatings formed by a combination of cassava starch (2 and 3% w / v) with essential oil of cinnamon bark (Cinnamomum zeylanicum) (0.05 to 0.30% v / v) or fennel (Foeniculum vulgare L.) (0.05 to 0.30% v / v) were developed and characterized. The addition of oil had the objective of developing a coating with antimicrobial and antioxidant properties and capacity to form a better water vapor barrier, due to the aggregation of the hydrophobic characteristics of essential oil. Physical stability, particle size and viscosity of the edible coatings were analyzed and films were characterized by mechanical properties, solubility and atomic force microscopy measures. Coatings emulsified with 2% cassava starch were stable and the 3% starch concentration with added essential oil showed water separation from the emulsified system. The coatings were applied to apple slices for water vapor resistance and respiration rate tests. The formulation with maximum concentration of both essential oils, at both concentrations of cassava starch, resulted in increased water vapor resistance, and respiration rates of coated apple slices showed a CO2 barrier effect in relation to fruit without coating. Mechanical properties analysis and atomic force microscopy showed that films added with cinnamon bark essential oil presented discontinuity on its matrix-forming capacity. Coating with cinnamon bark essential oil had significant antioxidant capacity. Inhibition of microorganisms tests proved that the formulation with 0.3% essential oil of cinnamon bark had a small inhibiting activity against Staphylococcus aureus and Salmonella choleraesius
Mestrado
Engenharia de Alimentos
Mestra em Engenharia de Alimentos
17
Erkan, Arcan. "Investigation Of Thin Semiconductor Coatings And Their Antimicrobial Properties." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/3/12606306/index.pdf.
Анотація:
Regular disinfection of surfaces is required in order to reduce the number of microorganisms, unable to transmit infections and maintaining the surfaces sterilized. For this purpose, antimicrobial thin film coatings on the various surfaces such as glass and ceramic surfaces, capable of killing harmful microorganisms are being investigated.
Generally a semiconducting material which can be activated by UV light tends to exhibit a strong antimicrobial activity. With holes (h+) and hydroxyl radicals (OH*) generated in the valence band, electrons and the superoxide ions (O2-) generated in the conduction band, illuminated semiconductor photocatalysts can inactivate microorganisms by participating in a series of oxidation reactions leading to carbon dioxide.
The aim of this current study was developing semiconductor coatings, increasing the photocatalytic activity of these coatings by metal doping, particularly palladium doping, and investigating the antimicrobial properties of these coatings.
In this study, glass surfaces were coated with titanium dioxide (TiO2), tin dioxide (SnO2) and palladium doped TiO2 and SnO2 sol-gels. After achieving thin, dense and strong coatings, antimicrobial properties of the coatings were investigated by applying the indicator microorganisms directly onto the coated glasses. Different cell wall structure of microorganisms can strongly affect the photocatalytic efficiency of the coatings. Hence Escherichia coli as a Gr (-) bacteria, Staphylococcus aereus as Gr (+) bacteria, Saccharomyces cerevisiae as a yeast and Aspergilus niger spores were used in the experiments.
Photocatalytic efficiency of TiO2 was better than SnO2 coatings. Palladium doping increased the antimicrobial activity of both coatings. The reduction efficiencies were found to decrease in the following order of E. coli [Gr (-)] >S. aereus [Gr (+)] >
S.cerevisiae (yeast) >
A. niger spores. The complexity and the density of the cell walls increased in the same order. As a result of this study, with the coating that shows the best photocatalytic activity, 98% of Escherichia coli, 87% of Staphylococcus aereus, 43% Saccharomyces cerevisiae were killed after 2 hours illumination.
18
Vangala, Lakshmisri Manisha. "Size Dependent Antimicrobial Properties of Sugar Encapsulated Gold Nanoparticles." TopSCHOLAR®, 2012. http://digitalcommons.wku.edu/theses/1166.
Анотація:
The antimicrobial properties of dextrose encapsulated gold nanoparticles (dGNPs) with average diameters of 25 nm, 60 nm, and 120 nm (± 5 nm) synthesized by green chemistry principles were investigated against both Gram-negative and Gram-positive bacteria. Studies were performed involving the effect of the dGNPs on the growth, morphology and the ultrastructural properties of bacteria. dGNPs were found to have significant dose dependent antibacterial activity which was directly proportional to their size and also their concentration. The microbial assays revealed the dGNPs to be bacteriostatic as well as bactericidal. The dGNPs exhibited their bactericidal action through the disruption of the bacterial cell membrane causing leakage of cytoplasmic content. The overall outcomes of this study suggest that dGNPs hold promise as a potent antimicrobial agent against a wide range of disease causing bacteria and can control and prevent possible infections or diseases.
19
Amengor, Dzifa. "Antimicrobial Properties of Verbesina negrensis Extracts against Helicobacter pylori." Thesis, Southern Illinois University at Edwardsville, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10792975.
Анотація:
Helicobacter pylori is a bacterium that can cause chronic gastritis and gastrointestinal cancers in some infected people due to the overexpression of inflammatory cytokines and oxidative stress resulting from accumulation of reactive oxygen species. Verbesina negrensis is a plant that is routinely used in the treatment of gastric complaints. The purpose of this research is to isolate pure bioactive compounds from V. negrensis and evaluate the antimicrobial properties of the isolates against H. pylori. Additionally, we will determine the toxicity of the plant extracts on gastric epithelial cells (NCI-N87) using the MTT assay. We hypothesized that V. negrensis pure compounds would have anti-Helicobacter properties and low cytotoxicity to the epithelial cells. To test this hypothesis pure compounds were isolated from the V. negrensis ethanolic crude extract using silica gel and bioassay guided chromatography. Two pure compounds were isolated AG2 and AQ2B with MICs of 16 µg/mL and 128 µg/mL respectively. AQ2B was cytotoxic to NCI-N87 cells at MIC 128 µg/mL and sub-MIC values of 64, 32 and 16 µg/mL.
20
Song, Ronghui. "Synthesis, Characterization and Antimicrobial Properties of Novel Naphthoquinone Derivatives." Kent State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=kent1586783242508385.
21
Rosa, Marguerita Evangelho da. "Production and purification of IgY antibodies with antimicrobial properties." Master's thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/22545.
Анотація:
Mestrado em Biotecnologia - Biotecnologia Industrial e AmbientalA Aquacultura tem recebido especial destaque nos últimos anos como alternativa às atividades de pesca tradicional, atualmente restritas pelos limites legais de captura. Neste sentido, têm-se desenvolvido novas técnicas de modo a aumentar o lucro e o rendimento das atividades associadas à aquacultura. No entanto, a sobre-exploração de espécies, poluição, surgimento de doenças e o aumento de microorganismos resistentes a antibióticos, surgem como consequências deste desenvolvimento. Vibrio anguillarum é uma bactéria Gram-negativa que causa infeções em peixes de sistemas de aquacultura e que origina perdas económicas significativas. Estas infeções são normalmente tratadas com recurso a agentes antimicrobianos, tais como antibióticos. No entanto, a prevalência de bactérias resistentes a estes compostos destaca a necessidade crucial de desenvolvimento de estratégias terapêuticas alternativas. O uso de anticorpos, nomeadamente a imunoglobulina Y (IgY) produzidas em aves poedeiras e purificado a partir de gemas de ovos é uma abordagem promissora para o controlo de infeções por V. anguillarum na aquacultura. O atual trabalho centrou-se no desenvolvimento de anticorpos IgY específicos contra os determinantes de virulência associados a V. anguillarum como uma estratégia antimicrobiana capaz de melhorar a produtividade dos sistemas de aquacultura. Neste são apresentados resultados da produção, purificação e caracterização de anticorpos IgY de galinha e codorniz contra antigénios (extratos celulares, frações da membrana externa e péptidos do canal TolC) de V. anguillarum. Aves hiperimunes foram produzidas com sucesso para cada antigénio e foram purificadas as respetivas frações específicas de IgY (> 95% de pureza). Por fim, estudou-se o potencial antimicrobiano dos anticorpos anti-extrato celular de V. anguillarum por ensaios de crescimento bacteriano que revelaram um efeito bacteriostático promissor com 50% de inibição. Em suma, e face aos resultados obtidos, os anticorpos podem ser usados como agentes antimicrobianos alternativos para combater e prevenir infeções por V. anguillarum em sistemas de aquacultura.
Aquaculture has received remarkable attention in recent years as an alternative to traditional fishing activities, currently restricted by fishing quotas. New techniques have therefore been developed to increase production and profit of aquaculture activities. However, over-exploitation, pollution, appearance of infectious diseases and antimicrobial resistance, have emerged as concerning consequences of such development. Vibrio anguillarum is a Gram-negative bacterium causing fish infections in aquaculture systems and leading to significant economic losses. These infections are usually treated with antibiotics; however, the prevalence of bacteria resistant to such drugs urges the development of alternative therapeutic strategies. The use of antibodies, namely avian Immunoglobulin Y (IgY) purified from bird egg yolks, is a promising approach for the control of V. anguillarum infections in aquaculture. The current work focused on the development of specific IgY antibodies against virulence determinants associated to V. anguillarum, envisaging an antimicrobial strategy capable of improving the productivity of aquaculture systems. In this work, the production, purification and characterization of chicken and quail IgY antibodies against V. anguillarum antigens are presented. Whole-cell extracts, outer-membrane fractions and outer-membrane TolC channel peptides were used as antigens in independent protocols to elicit target-specific V. anguillarum antibodies. Hyperimmune birds were successfully generated for each antigen and respective target-specific IgY fractions were purified (>95% purity) from selected bird eggs for downstream studies. Finally, the antimicrobial potential of anti-whole-cell V. anguillarum antibodies was studied by bacterial growth assays, revealing a promising bacteriostatic effect, with 50% of bacterial growth inhibition. In summary, and according to the results obtained, such antibodies can be used as alternative antimicrobial agents to prevent and combat infections by V. anguillarum in aquaculture systems.
22
Sandhu, Guneev. "Characterization of Lactose Esters for Their Antimicrobial and Emulsification Properties." DigitalCommons@USU, 2014. https://digitalcommons.usu.edu/etd/3855.
Анотація:
Sucrose esters have an established use in food industry as emulsifiers. Two novel lactose esters (lactose monodecanoate and lactose monomyristate) were synthesized and studied for their antimicrobial and emulsification properties. Lactose is a byproduct in cheese production and is an inexpensive carbohydrate source.
The antimicrobial activity of lactose monodecanoate (LMD) and lactose monomyristate (LMM) was tested against the growth of seven different bacteria. Both esters, when dissolved in dimethoxy sulfoxide (DMSO), proved bactericidal against Bacillus cereus, Mycobacteria KMS and Streptococcus suis. LMM/DMSO was bactericidal against B. cereus at concentrations between 1 and 3 mg/ml. LMM/DMSO was bactericidal against M. KMS and S. suis at concentrations between 3 and 5 mg/ml. LMD/DMSO was bactericidal against B. cereus and S. suis at concentrations between 1 and 3 mg/ml and against M. KMS at concentrations between 0.1 and 1 mg/ml. LMM/DMSO and LMD/DMSO were not effective in inhibiting the growth of Listeria monocyotgenes and Enterococcus faecalis.
The antimicrobial effects of LMD on the growth of Listeria monocytogenes and Enterococcus faecalis were found to be solvent dependent. LMD, when dissolved in 30% ethanol, was able to inhibit the growth of L. monocytogenes at concentration between 1 and 3 mg/ml and E. faecalis at concentration between 3 and 5 mg/ml. The growth of Streptococcus mutans and Escherichia coli O157:H7 remained unaltered in the presence of LMD/ETOH, LMD/DMSO and LMM/DMSO up to 5 mg/ml.
LMM was also analyzed for its emulsification properties. The destabilization rates and droplet size of the emulsion were determined for five consecutive days. At a concentration of 0.5%, LMM produced 20% oil in water emulsion with destabilization rate of 1.1 mm/day, which can be considered a stable emulsion. The droplet size of the emulsion was also within the range of 0-10 μm. Lower droplet size range signifies the effective work of the LMM as an emulsifier. Also the droplet size of the emulsion was found to be consistent over five days, which is indicative of a stable emulsion.
23
Schwartz, Véronique Bernadette [Verfasser]. "Design of nanoparticle systems with antimicrobial properties / Véronique Bernadette Schwartz." Mainz : Universitätsbibliothek Mainz, 2012. http://d-nb.info/1019668938/34.
24
Smith-Palmer, Mary Alison. "The antimicrobial properties of plant essential oils against foodborne pathogens." Thesis, Queen Margaret University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327082.
25
Belkhair, Sama Salem. "Antimicrobial properties of Ag zeolites and Ag zeolite containing polymers." Thesis, Manchester Metropolitan University, 2016. http://e-space.mmu.ac.uk/617118/.
Анотація:
Ag zeolites have been studied in this thesis for antibacterial applications in powder form or in composite materials. The influence of the textural characteristics (crystal size and mesoporosity) of silver-exchanged FAU- and BEA-type zeolites on their antimicrobial efficacy was studied. Two pairs of zeolite X and zeolite beta with different sizes as well as a mesoporous zeolite beta were tested against Escherichia coli (E. coli) and Candida albicans (C. albicans). Reduction of crystal size resulted in a slight decrease in the killing efficacy against both microorganisms. Zeolite beta showed higher activity than zeolite X despite the lower Ag content in that sample, which was attributed to the higher concentration of silver released from zeolite beta samples to the medium. Introduction of mesoporosity had a beneficial effect on the antimicrobial efficacy. Cytotoxicity measurements using peripheral blood mononuclear cells indicated that Ag zeolite X was more toxic compared to Ag beta, particularly the nanosized sample. The influence of the form of silver (metallic or ionic) on the antimicrobial efficacy was determined using Ag-loaded EMT zeolites. The killing efficacy of pure EMT, Ag+-EMT and Ag0-EMT against E. coli was studied semi-quantitatively. The antibacterial activity increased with increasing Ag content for both types of samples (Ag+-EMT and Ag0-EMT). The Ag0-EMT samples show slightly enhanced antimicrobial efficacy compared to that of Ag+-EMT, however, the differences are not substantial and the preparation of Ag nanoparticles is not viable considering the complexity of preparation steps. A multidisciplinary approach has been applied to the preparation of antibacterial Ag zeolite/silicone elastomer composites aimed at products that satisfy a range of requirements, namely good mechanical properties after zeolite incorporation and strongly antibacterial. The composites showed strong efficacy against E. coli and Staphylococcus epidermidis (S. epidermidis). Organic functionalisation of the zeolite with organo-silanes prior blending with the matrix usefully improved composite mechanical properties and reduced colour development in Ag zeolite containing silicone elastomers. The same approach was applied for the preparation of dental acrylic resins. Antibacterial dental resin containing Ag zeolites at loadings of 0.2, 0.4, 0.7 and 2 wt.% were prepared. The composites showed strong efficacy against E. coli and no viable E. coli were detected after 5 hours of incubation. The presence of Ag zeolites within the acrylic resin resulted in resin discolouration, which was more pronounced at high Ag zeolite loadings. A sustained Ag release over long periods of time (54 days) was observed with a greater Ag release in artificial saliva compared to that in distilled water. Dental resins loaded with Ag-free zeolites followed by post-fabrication insertion of Ag by ion-exchange were prepared to overcome discolouration. The materials prepared using this approach had a similar colour to that of the original polymer as determined by the colour measurements. These composites showed strong efficacy against E. coli and no viable E. coli cells were detected after 5 hours of incubation.
26
BERTON, FEDERICO. "BIORESORBABLE ENGINEERED MEMBRANES FOR GUIDED BONE REGENERATION WITH ANTIMICROBIAL PROPERTIES." Doctoral thesis, Università degli Studi di Trieste, 2020. http://hdl.handle.net/11368/2963760.
Анотація:
Gli argomenti principali di questa tesi di dottorato sono la rigenerazione ossea e l'analisi del tessuto osseo mediante strategie nanotecnologiche per entrambi gli scopi. In breve, sono stati esplorati lo sviluppo di membrane e impalcature nanostrutturate per le procedure di rigenerazione ossea nella chirurgia orale, insieme all'ottimizzazione dei protocolli di analisi su micro e nanoscala. Sono stati acquisiti, assemblati e testati i componenti necessari per il processo ELS. Sono state testate diverse combinazioni di solventi per la preparazione di membrane a base di policaprolattone (PCL). Successivamente, è stato applicato un processo aria-plasma al fine di aumentare l'idrofilia della membrana. La caratterizzazione qualitativa delle membrane ottenute da ELS, prima e dopo il trattamento al plasma, è stata eseguita insieme all'analisi morfologica mediante microscopia elettronica a scansione.
Il chitosano modificato con lattosio (CTL) è stato aggiunto mediante adsorbimento chimico sulle membrane del PCL al fine di aumentarne la bioattività. L'analisi microscopica confocale ha mostrato un miglior assorbimento del CTL per le membrane trattate con aria-plasma rispetto a quelle non trattate. Inoltre, CTL è stato utilizzato per fornire, sulle membrane, nanoparticelle d'argento (nAg) sintetizzate all'interno della soluzione CTL. L'analisi ETAAS, ha mostrato un maggiore contenuto di nAg nelle membrane trattate con un trattamento plasma-aria a bassa energia e CTL-nAg a pH 7, confermando così i risultati di Raman. Le cellule MG63 coltivate su membrane PCL con o senza CTL, hanno mostrato una crescita più sostenuta dopo 7 giorni sulle membrane rivestite con CTL rispetto alle membrane PCL non trattate e alle membrane trattate con aria-plasma PCL. Inoltre, la presenza di nAg non ha ostacolato la vitalità cellulare rispetto alle membrane PCL, come confermato dal test della lattato deidrogenasi (LDH). L'attività antibatterica delle membrane PCL-nAg è stata testata in termini di inibizione del biofilm su Pseudomonas aeruginosa e Staphylococcus aureus, utilizzando il test MTT. I dati di vitalità e l'imaging SEM hanno mostrato chiaramente che la formazione di biofilm era fortemente inibita sulla superficie delle membrane PCL-CTL-nAg. La resistenza meccanica delle membrane prodotte, imbevute e invecchiate nel fluido corporeo simulato (SBF) è stata testata mediante prove di trazione uniassiali per la valutazione del modulo elastico e la massima deformazione e stress. Come secondo capitolo di questa tesi, è stata esplorata la potenzialità di un altro approccio per produrre membrane a base di fibrina nanostrutturate. Queste membrane sono state ottenute mediante centrifugazione del sangue e sono state adattate con molecole che inducono l'osso, come la nano-idrossiapatite (nHAp). Pertanto, è stata testata la durabilità della membrana incontaminata in SBF. Ad ogni momento, un campione è stato analizzato con SEM con strumenti di elaborazione rivelando un diametro medio della fibra di 0,103 ± 0,05 µm senza differenze statisticamente significative nel tempo; il saggio di degradazione ha mostrato un aumento di due volte del peso correlato all'assorbimento di SBF nei primi 2 giorni. Dal terzo giorno è stato osservato un costante degrado. Successivamente, sono stati studiati gli effetti dell'aggiunta di nHAp durante il processo di formatura di PRF (quindi durante la centrifugazione). Poiché tutte le tecniche sopra menzionate erano orientate a rigenerare l'osso maxillo-facciale, è stato ottimizzato un protocollo di analisi istomorfometrica dell'osso che, al momento della stesura della presente tesi, non era ancora presente all'Università di Trieste). Questo protocollo è stato preparato e implementato con l'analisi ultrastrutturale SEM-EDS (Energy Dispersive Spectroscopy) dei tessuti duri montati sulle diapositive istologiche.The main topics of this doctoral thesis are bone regeneration and bone tissue analysis by means of nanotechnological strategies for both purposes. Briefly, the development of nanostructured membranes and scaffolds for bone regeneration procedures in oral surgery have been explored, together with the optimization of analysis protocols at the micro- and nano-scale. The first attempts were addressed to reproduce some of the recent results reported in the scientific literature. Thereafter the necessary components for the ELS process were acquired, assembled and tested. Different combinations of solvents for the preparation of polycaprolactone (PCL) based membranes were tested. Thereafter, an air-plasma cleaning process was applied in order to increase the membrane hydrophilicity. Qualitative characterization of membranes obtained by ELS, before and after plasma treatment has been performed together with the morphological analysis through Scanning Electronic Microscopy. The determination of surface wettability with contact angle measurements was performed. Lactose-modified chitosan (CTL) was added by chemical adsorption on PCL membranes in order to increase their bioactivity. Confocal microscopy analysis showed an improved adsorption of CTL for the membranes treated with air-plasma if compared with the untreated ones. Moreover, CTL was used to deliver, on the membranes, silver nanoparticles (nAg) synthesized within CTL solution. ETAAS analysis, performed to quantify nAg, showed a higher nAg content in membranes treated with a low energy air-plasma treatment and CTL-nAg at pH 7, thus confirming Raman findings. MG63 cells cultured on PCL membranes with or without CTL, showed a more sustained growth after 7 days on the CTL-coated membranes compared with untreated PCL membranes and PCL air-plasma treated membranes. Moreover, the presence of nAg did not hamper cell viability with respect to PCL membranes, as confirmed by lactate dehydrogenase (LDH) assay. The antibacterial activity of PCL-nAg membranes was tested in terms of biofilm inhibition on Pseudomonas aeruginosa (ATCC 27853) and Staphylococcus aureus (ATCC 25923), using the MTT test. The viability data and the SEM imaging clearly showed that the biofilm formation was strongly inhibited on the surface of PCL-CTL-nAg membranes. Mechanical resistance of the produced membranes, soaked and aged in Simulated Body Fluid (SBF) was tested by means of uniaxial tensile tests for the evaluation of elastic modulus and maximal deformation and stress. As second chapter of this thesis, the potentiality of another approach to produce nanostructured fibrin-based membranes was explored. These membranes were obtained by means of blood centrifugation and were tailored with bone-inducing molecule, such as nano-hydroxyapatite (nHAp). Thus, the durability of pristine membrane in SBF was tested. At each time point, one sample was analyzed with SEM with ImageJ processing tools revealing a mean fiber diameter of 0.103 ± 0.05µm without any statistically significant differences during time; degradation assay showed a two-folds increase of the weight related to the SBF absorption in the first 2 days. From the third day a constant degradation was observed. In the time frame of this experiment, the dimensional stability of the fibrin structure up to day 7 suggested that PRF membranes may also be used uncovered in the oral cavity. Subsequently, the effects of the nHAp addition during the forming process of PRF (thus during centrifugation) were investigated. As all the above-mentioned techniques were oriented to regenerate maxillofacial bone, a bone histomorphometric analysis protocol that, at the time of writing of the present thesis, was not already present in the University of Trieste) was optimized. This protocol was prepared and implemented with the ultrastructural SEM-EDS (Energy Dispersive Spectroscopy) analysis of hard tissues mounted on the histological slides).
27
Chindera, Kantaraja. "Cell uptake properties of Polyhexamethylene Biguanide (PHMB) and applications in intracellular delivery." Thesis, Royal Veterinary College (University of London), 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.618319.
28
Gilles, Martin. "Screening of the antimicrobial properties of four Australian native Eucalyptus species /." Sion, 2007. http://doc.rero.ch/search.py?recid=8350&ln=fr.
29
Fitzgerald, Daniel J. "Investigation of the antimicrobial properties of the phenolic flavour compound vanillin." Thesis, University of East Anglia, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273578.
30
Gledhill, L. "Antimicrobial and beta-lactamase inhibitory properties of chlorinated 6-spiro-epoxypenicillins." Thesis, University of Nottingham, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233715.
31
Wong, Sze Yinn (Sze Yinn Jessie). "Polyelectrolyte multilayer thin films with antimicrobial, antifouling and drug releasing properties." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/65768.
Анотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 152-160).
This thesis work focuses on designing thin polyelectrolyte multilayer (PEM) films via layer-bylayer (LbL) deposition technique with the ability to kill pathogenic bacteria and inactivate human viruses, especially the influenza (flu) virus on contact. This work builds on four years of research at the Institute for Soldier Nanotechnologies (ISN) focusing on creating new, nonleaching microbicidal material; this film is envisioned to be used as permanent surface coatings for weapons, equipments, uniforms, personal items, etc. because a small reduction in the rate of infection will greatly enhance the readiness and performance of soldiers and other military personnel. Extending this application to everyday life, commonly handled objects such as doorknobs, computer keyboards, and touch screens can also be made sterile by coating them with these highly effective microbicidal PEM films. These films can also be used to prevent infections and long-term bacterial biofilms on implant surfaces. The ultimate aim of this thesis work is to create a broadly applicable multifunctional platform film technology that will satisfy various thin film surface coating applications; this film will impart a surface with long term antimicrobial / antifouling functionality via a permanent microbicidal base, and controlled delivery of a therapeutic agent via a hydrolytically degradable top film as needed. Efforts were focused on maximizing and understanding the factors that influence the microbicidal / antifouling property of the film; thus far, we successfully designed a set of contact-killing ionically cross-linked polymeric thin films; a hydrophobic polycation, linear NNdodecyl, methyl- poly(ethylenimine) (DMLPEI) with microbicidal activity was layered with a hydrophilic polyanion, such as poly(acrylic acid) (PAA), to create LbL films highly effective against Escherichia coli and Staphylococcus aureus (Gram negative and positive bacteria, respectively), as well as the influenza A/WSN (H1N1) virus. The microbicidal film was also demonstrated to significantly resist adsorption of protein from blood plasma relative to an uncoated substrate. By generating PEM films assembled with the hydrophobic N-alkylated poly(ethylenimine) and the hydrophilic poly(acrylic acid), an ultrathin film that exhibited antifouling and antimicrobial properties was created. Results showed that a fine balance of hydrophobicity and hydrophilicity on the surface of the films was needed to create molecularlevel heterogeneities unfavorable to protein adsorption; due to the contrasting nature of the polymer making up the film, nanoscale segregation of the polymer segments into hydrophobic and hydrophilic moieties could occur on the surface. We then moved on to design a dual functional LbL film construct combining the permanent microbicidal / antifouling base film with a hydrolytically degradable PEM top film offering controlled and localized delivery of therapeutics (e.g. antibiotic, anti-inflammatory drug, etc.). When the degradable top film is completely eroded, the surface will be left with the permanent microbicidal film for long-term prevention of fouling by biomolecules and microorganisms (e.g., proteins and bacteria).
by Sze Yinn (Jessie) Wong.
Ph.D.
32
Melaiye, Abdulkareem M. "Synthesis and Antimicrobial Properties of Silver(I) N-Heterocyclic Carbene Complexes." University of Akron / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=akron1124310734.
33
Mody, Shreena Himanshu. "The Antimicrobial Properties of Honey and Their Effect on Pathogenic Bacteria." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7042.
Анотація:
Honey has been used to heal wounds since ancient times. There are many references in ancient literature that cite honey for its medicinal uses. It is used as an alternative agent to cure infections of wounds, burns, ulcers etc. Researchers have shown some of the antimicrobial properties of honey when used as an ointment. When applied to an affected area, it helps to promote the growth of healthy tissue. One of the factors on which the quality of the honey depends, is its geographical origin. Based on the location, honey types can vary as much as 100-fold from each other in color, aroma, viscosity, and antimicrobial properties. The important components in honey that play an essential part in healing wounds and contributing to the antimicrobial properties are enzymes. Their presence allows honey to kill various types of pathogenic bacteria, viruses, fungi etc. A higher antimicrobial effect is seen in monofloral honey (when a single plant species is the source of nectar), which is often more potent than other types of honey in terms of antibacterial activity. Resistance of pathogens to these antimicrobial actions has never been shown, which makes honey a more promising source of antimicrobial research. Presently, infections of burns and wounds are very challenging to treat, especially when they are caused by antibiotic-resistant bacteria. The purpose of this study was to examine the antimicrobial properties of honey from Utah and other locales, and to identify promising antimicrobial activities that could be useful in treating infections caused by resistant bacteria.
34
Bensaci, Mekki F. "The Bioactive Properties of Syringomycin E-Rhamnolipid Mixtures and Syringopeptins." DigitalCommons@USU, 2009. https://digitalcommons.usu.edu/etd/247.
Анотація:
The need for new antimicrobial agents has become important in the last decade due to emerging resistance to a number of conventional antimicrobial agents. New approaches and sources are needed to generate novel and effective antimicrobials. For example, synergistic combinations between two or more agents may lead to new antimicrobial therapies. Furthermore, the increase in health problems caused by the exposure to agricultural crop pesticides and synthetic fungicides and the emerging development of organic farming has increased the necessity to develop natural products than can be used safely in controlling crop diseases.
In this work, I present the first studies on the bioactive properties, particularly fungicidal activities, of mixtures of SRE and rhamnolipids. The in vitro results clearly showed strong synergism between SRE and rhamnolipids against phytopathogenic fungi and yeast. However, no activity was observed against bacteria. The hemolytic activities and cytotoxicities of SRE and SYRA were dose dependent.
SRE acts on yeast and plant plasma membranes to cause numerous cellular effects. The effects are consistent with SRE's ability to form ion-conducting voltage sensitive channels in membrane bilayers. In addition, studies with yeast have revealed that sphingolipids and sterols modulate the fungicidal activity of SRE. Saccharomyces cerevisiae sphingolipid and sterol biosynthetic mutants were used to investigate the mechanism of action of SYRA against fungi. These results suggest that similar to SRE, SYRA antifungal action is promoted by sphingolipids and sterols of the plasma membrane and involves pore formation.
I further explored the antimicrobial spectrum of syringopeptin SP25A and show that it specifically inhibits Gram-positive bacteria and yeast. I also investigated its mechanism of action against yeast and bacteria. The results revealed the role for D-alanylation of teichoic acids in modulating the susceptibility of B. subtilis to SP25A and other syringopeptins. This is consistent with the charged nature of the cyclic peptide portions of the syringopeptins, and it provides an explanation for SP25A's higher degree of specificity for Gram-positive bacteria. In addition and similar to SRE, SP25A antifungal action is promoted by sphingolipids and sterols of the plasma membrane and involves pore formation.
Overall, the research shows that SRE and rhamnolipids are synergistically active against yeast and fungi and that the syringopeptins have antimicrobial activities against yeast and Gram-positive bacteria. Insights into the mechanisms of action of the SRE and rhamnolipid mixtures and the syringopeptins and their potential as novel antimicrobial agents are revealed.
35
Zhang, Manrui. "Studies of a click reaction route to antimicrobial polymer latexes." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/studies-of-a-click-reaction-route-to-antimicrobial-polymer-latexes(b6c2b634-ec41-44b6-a88f-2d908e1f422c).html.
Анотація:
The objective of this project was to prepare alkyne-functionalized polymer latexes using surfactant-free emulsion polymerization, and then functionalize these polymer latexes with three quaternary ammonium azides via Cu(I)-catalyzed azide/alkyne cycloaddition (CuAAC) in order to produce antimicrobial polymer latexes. Three quaternary ammonium azides with different linear alkyl chain lengths (C4, C8 and C12) were successfully synthesised in high yield ( > 70%) using established procedures, and their purity determined by elemental analysis, Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. Alkyne-functionalized polymer latexes were prepared via surfactant-free emulsion polymerization using 2,2'-azobis(2-methylpropionamidine)dihydrochloride (AIBA) as initiator, [2-(methaccryloyloxy)ethyl]trimethylammonium chloride (MATMAC) as cationic comonomer, propargyl methacrylate (PMA) to provide the alkyne groups, and for some latexes, ethylene glycol dimethacrylate (EGDMA) as crosslinking comonomer. The effects of temperature and the concentrations of AIBA, MATMAC, PMA and EGDMA on monomer conversion, the rate of polymerization, particle diameter and colloidal stability have been investigated. The studies showed that the very high rates of polymerization were due to high values of the number of radicals per particle (in the range 3-2300). The observations also determined that the reaction conditions required to produce small particles (diameter of 150-350 nm) of narrow size distribution were: 75 oC reaction temperature, AIBA at 0.2 wt% to the total mass of monomer, MATMAC level of smaller or equal to 12 mol% to total monomer (including MATMAC), and EGDMA level of < 2.0 mol% to total monomer (excluding EGDMA). Three series of alkyne-functionalized polymer latexes have been synthesised using these conditions: non-crosslinked (NCL), crosslinked (CL) and core-shell (CS). All the latex particles were functionalized with the three quaternary ammonium azides by CuAAC. Zeta potential analysis, FTIR and Raman spectroscopy analysis confirmed the success of the click reactions. The quantitative analysis of FTIR and Raman spectra showed similar values of conversion of click reaction for both NCL and CL particles, indicating NCL and CL particles have similar swellability. The data also showed that significantly higher click reaction conversions were achieved for CS particles (around 60%) than for NCL/CL particles (less than 40%), which indicates that the click reaction only occurred at the surface of particles and that a higher proportion of alkyne groups are located on the surface of CS particles than on NCL/CL particles. The antimicrobial properties of all QAAs, MATMAC, NCL, CL and CS polymer latexes against E. coli bacteria (ATCC 25922) have been investigated using a modified liquid microdilution method in M9 medium, which was shown not to affect latex colloidal stability. It was found that all the polymer latexes showed much higher antimicrobial activities (MIC 6.5-75 µg ml-1) than many antimicrobial polymers reported recently in the literature (MIC 100-2000 µg ml-1); (Ganewatta, M.S. and C.B. Tang, Controlling macromolecular structures towards effective antimicrobial polymers. Polymer, 2015. 63: p. A1-A29). Polymer latexes with clicked-on QAAs showed significantly higher antimicrobial activities than the original latexes. The magnification of the increase in antimicrobial properties of CS particles after click reaction (~3.5 times) was greater than for NCL/CL particles (~2.5 times), showing that a larger amount of QAAs have been clicked onto the surface of CS particles than NCL/CL particles and that the clicked-on QAAs enhance the antimicrobial activity significantly.
36
Xu, Youhong. "Adaptive immune response-modifying and antimicrobial properties of Andrographis paniculata and andrographolide." University of Southern Queensland, Faculty of Sciences, 2009. http://eprints.usq.edu.au/archive/00005134/.
Анотація:
Andrographis paniculata (AP) is a traditional herbal medicine which is widely used for the treatment of many diseases in Asia. Recently, various biological activities of AP extract or andrographolide (AND), such as immunostimulatory activity, anti-inflammatoryeffect, cytokine induction or deduction, a potential cancer therapeutic agent and T cell activation suppression, have been reported. However the potential ofAP extract or AND to stimulate the specific or adaptive immune response using microbial vaccines has not been determined. In this project, AND has been purifiedfrom AP and its identity confirmed by the melting point, colour test, TLC, UV absorption spectrum, ESI-MS and H-NMR. An aqueous and two ethanolic extracts ofAndrographis paniculata and AND, an active principle of Andrographis paniculata, were investigated for their antimicrobial activity against nine bacterial species in vitro using the disc diffusion method. It was discovered that neither the aqueous extract nor AND were bacteriostatic or bactericidal against S. typhimurium, E. coli, S. sonnei, S. aureus, P. aeruginosa, S. pneumoniae, S. pyogenes, L. pneumophila or B. pertussisbut the two ethanolic extracts of AP were bacteriostatic against L. pneumophila and B. pertussis. It was also observed that the ethanol extract of AP and AND stimulatedboth antibody and cell-mediated immunity (CMI) responses to a killed S. typhimurium vaccine. Mice were vaccinated with either one dose or two doses of killed S. typhimurium vaccine. They were fed two different quantities of an ethanol extract of AP or AND for 14 days in mice immunised with one dose of the vaccine, and for 28 days in mice immunised with two doses of vaccine, respectively. Both the extract and AND significantly increased the IgG antibody titres against S. typhimurium, with theincrease in antibody titres being statistically significant in the two dose vaccine group. Although not statistically significant, there was also a substantial increase in the IgG antibody titres in the one dose vaccine group. Splenocyte cultures from mice fromboth the immunisation groups treated with the extract or AND stimulated with the S. typhimurium lysate showed a significant increase in the production of IFN-γ in both14 and 28 day AP extract or AND treatment groups. The increase indicates the induction of a cell-mediated immune response. To confirm the immunomodulatory potential of AP extract and determine the immunomodulatory potential of AND, experiments were conducted using mouse salmonellosis as a model system. Mice were vaccinated with two doses of killed S. typhimurium vaccine by intraperitoneal(i/p) route and orally dosed with AP extract at 25 mg/kg bodyweight or AND at 4 mg/kg bodyweight for total 28 days, followed by oral challenge with virulent S. typhimurium. Both AP extract and AND substantially increased the survival rate by 50% after mice were challenged with 10 fold of a sublethal dose (1.5x10 6 cfu) of virulent S. typhimurium. They also promoted clearance of S. typhimurium from challenged mice by days 8 or 12 post-challenge with 1.5x10 cfu virulent S. typhimurium respectively. Sera IgG, IgA antibody titres against S. typhimurium and IFN-γ or IL-2 were detected after the mice were challenged by the oral route with a sublethal dose (1.5x10 cfu) of virulent S. typhimurium for 12 days. It was thus concluded that both Andrographis paniculata and AND not only elicited both humoral and cell-mediated immune responses in the mouse model, but also increasedthe protective efficacy against salmonellosis on mice vaccinated with inactivated S. typhimurium. Therefore the ability of Andrographis paniculata and AND to promoteacquired immunity, particularly in inducing CMI may be important in protection against intracellular pathogen infection.
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Kwok, Hoi-shan, and 郭凱珊. "The comparison of biological properties of L- and D-enantiomeric antimicrobial peptides." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206507.
Анотація:
Antibiotics have been used widely for the treatment of bacterial infections for over half a century. However, the emergence of resistance to antibiotics has aroused public health concern, leading to the development of antimicrobial peptides (AMPs) as potential alternative therapeutic agents against bacterial infections. AMPs are naturally found in many species and have important roles in our innate immune defense systems. AMPs are usually cationic amphipathic peptides with membrane destabilizing property. They have a relatively broad spectrum of antimicrobial activity and pathogens are less likely to develop resistance against AMPs. The major challenge of using AMPs as therapeutic agents is their toxicity towards mammalian cells. The biological stability of AMPs to protease in human body is another concern.
To address the latter problem, instead of the naturally occur L-enantiomers, Denantiomeric AMPs were introduced to enhance their stability. This study aimed to test the hypothesis that the D-enantiomeric AMPs are more resistant than the Lenantiomeric AMPs against proteolytic degradation. Three pairs of synthetic D-/LAMPs (D-LAO160-P13/LAO160-P12; D-LAO160-H/LAO160-H; and D-LAK-120-HP13/LAK-120-HP13) were employed to test for their stability when treated with trypsin, serum and gastric fluid, and the samples were analyzed by high performance liquid chromatography (HPLC). Generally, all the D-enantiomeric AMPs were found to be resistant towards proteolysis. Besides, to compare the cytotoxicity of D-/LAMPs, MTT and LDH assays of the D/L-LAK120-HP13 pair were carried out on two different cell lines, A549 cells (human lung adenocarcinoma epithelial cells) and RAW264.7 cells (mouse macrophage cells). Significant difference in cytotoxicity of D-LAK120-HP13 and LAK120-HP13 on RAW264.7 cells were obtained from MTT assay, but not in LDH assays or on A549 cells. Further analysis has to be done to validate the findings obtained from this research.published_or_final_version
Pharmacology and Pharmacy
Master
Master of Medical Sciences
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Mann, Maryssa Gudrun Ailsa. "An investigation of the antimicrobial and antifouling properties of marine algal metabolites." Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1007465.
Анотація:
Prevention of the accumulation of undesirable biological material i.e. biofouling upon a solid surface requires the use of antifouling systems. The solid surface may be a contact lens, an off shore oil rig or a living organism. When chemicals are employed as a mechanism of defense against biofouling, the agents involved are known as antifouling agents. Marine algae must protect themselves from fouling organisms and it is thought that one of the mechanisms used by these organisms is the production of secondary metabolites with an array of biological activities. In vitro studies have shown numerous compounds isolated from marine algae to possess antibacterial, antifungal and antimacrofouling activity. The aim of this study was to evaluate the secondary metabolite extracts of selected Southern African marine macro-algae as a potential source of compounds that inhibit biofilm formation and that could be used as antifouling agents. In this project, marine macro-algae were collected from various sites along the South African coastline. Their extracts were screened for antimicrobial activity against four ubiquitous microorganisms, Staphylococcus aureus, Klebsiella pneumoniae, Mycobacterium aurm and Candida albicans. Results of screening assays guided the fractionation of two Rhodophyta, Plocamium corallorhiza and Laurencia flexuosa. The algae were fractionated using silica gel column chromatography and compounds were isolated by semi-preparative normal phase HPLC. Compound characterization was performed using UV, IR and advanced one- and two-dimensional NMR (¹H, ¹³C NMR, COSY, HSQC, HMBC and NOESY) spectroscopy and mass spectrometry. Ten halogenated monoterpenes including four members of the small class of halogenated monoterpene aldehydes were isolated from extracts of P. corallorhiza. The compounds isolated included the known compounds 3,4,6,7-tetrachloro-3,7-dimethyl-1-octene; 4,6-dibromo-1, 1-dichloro-3,7 -dimethyl-2E,7 octadiene; 4,8-d ibromo-1,1,7 -trichloro-3, 7-dimethyl-2,5Eoctadiene;1 ,4,8-tribromo-3, 7 -dichloro-3,7-dimethyl-1 E,5E-octadiene; 8-bremo-6, 7-dichloro-3,7-dimethyl-octa-2E,4E-dienal; 4-Bromo-8-chloro-3,7-dimethyl-octa-2E,6E-dienal; 4,6- Dibromo-3,7-dimethyl-octa-2E,7-dienal; 2,4-dichloro-1-(2-chlorovinyl)-1-methyl-5-methylidene-cyclohexane and two new metabolites 4,8-chloro-3,7-dimethyl-2Z,4,6Z-octatrien-1-al and Compound 3.47. Methodology was developed for the chemical derivatization and mass spectrometric analysis of the aldehydic compounds, The aldehyde trapping reagent 0-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride was used to derivatize the molecules, stabilizing them and allowing for their complete characterization. From Laurencia flexuosa a new cuparene sesquiterpene 4-bremo-2-(5-hydroxy-1,2,2- trimethylcyclopent-3-enyl)-5-methylphenol was isolated along with two geometric isomers of the vinyl acetylene bromofucin , An halogenated monoterpene 3S*,4R*-1-bromo-3,4,8-trichloro-9-dichloromethyl-1-E,5-E,7-Z-octatriene was also isolated but was suspected to be a contaminant and an investigation into its biological source revealed that it originated from Plocamium suhrii. A third alga, Martensia elegans was extracted based on published reports of antimicrobial compounds in related species. A new a-alkyl malate derivative was isolated and characterized. Selected compounds isolated during the course of the study were employed in preliminary assays that tested their ability to inhibit biofilm formation by Pseudomonas aeruginosa. The halogenated monoterpenes isolated from the Plocamium species were the only active compounds. 3S*,4R*-1-bromo-3,4,S-trichloro-g-dichloromethyl-1-E,5-E,7-octatriene from P. suhrii inhibited biofilm formation through antibacterial activity on planktonic cells but could not prevent biofilm formation when employed as a film on the surface of microtitre plate wells. 1,4,8-tribromo-3,7-dichloro-3,7-dimethyl-1E,5E-octadiene and 4,6-dibromo-1,1-dichloro-3,7-dimethyl-2E,7-octadiene inhibited biofilm formation when applied as a film to the microtitre plate wells but had no significant antibacterial activity. No potential antifouling agents were identified in this project but the antimicrobial activity exhibited by the crude algal extracts was highly encouraging and a number of new research areas have been identified.KMBT_363
Adobe Acrobat 9.54 Paper Capture Plug-in
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Hetrick, Evan M. Schoenfisch Mark H. "Antimicrobial and wound healing properties of nitric oxidereleasing xerogels and silica nanoparticles." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2008. http://dc.lib.unc.edu/u?/etd,1928.
Анотація:
Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2008.Title from electronic title page (viewed Dec. 11, 2008). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Chemistry Analytical Chemistry." Discipline: Chemistry; Department/School: Chemistry.
40
Torrey, Jason Robert. "Antimicrobial Properties Of Metal And Metal-Halide Nanoparticles And Their Potential Applications." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/338682.
Анотація:
Heavy metals have been known to possess antimicrobial properties against bacterial, fungal, and viral pathogens. Silver and copper in particular have been used for millennia to control bacterial and fungal contamination. Metal nanoparticles (aggregations of metal atoms 1-200 nm in size) have recently become the subject of intensive study for their increased antimicrobial properties due to their increased surface area and localized release of metal ions when attached to pathogens. In the current studies, metal and metalhalide nanoparticles including silver (Ag), silver bromide (AgBr), silver iodide (AgI), and copper iodide (CuI) nanoparticles were evaluated for their antibacterial efficacy against two common bacterial pathogens. All of the nanoparticles significantly reduced bacterial numbers within 24 hours of exposure and were more effective against the Gram-negative Pseudomonas aeruginosa than the Gram-positive Staphylococcus aureus. CuI nanoparticles were found to be highly effective, reducing both organisms by >4.43 log₁₀ within 15 minutes at 60 ppm Cu. CuI nanoparticles were selected for further evaluation against a range of microorganisms to determine their broad spectrum efficacy. CuI nanoparticles formulated with different stabilizers (sodium dodecyl sulfate, SDS; PVP) were tested against representative Gram-positive and Gram-negative bacteria, Mycobacteria, a fungus (Candida albicans), and a non-enveloped virus (poliovirus). Both nanoparticles caused significant reductions in most of the Gram-negative bacteria within five minutes of exposure (>5.09-log₁₀). The Gram-positive bacterial species were more sensitive to the CuI-SDS than the CuI-PVP nanoparticles. Likewise, C. albicans was also more sensitive to the CuI-SDS than the CuI-PVP nanoparticles. In contrast, the acid-fast Mycobacterium smegmatis was more resistant to the CuI-SDS than the CuI-PVP nanoparticle solutions (2.54-log₁₀ vs. 3.80-log₁₀ after 30 minutes). Poliovirus was more resistant than the other organisms tested except for Mycobacterium fortuitum. M. fortuitum was more resistant to both CuI nanoparticle solutions than any of the other organisms tested, requiring longer exposure times to achieve comparable reductions (~4.15 log₁₀ after 24 hours). As an example of a real world antimicrobial application, polymer surface coatings with embedded CuI nanoparticles were investigated to determine their potential use as self-disinfecting surfaces. Brushed polyurethane, spincoated acrylic, and powder coated polyester-epoxy coatings containing various concentrations of CuI nanoparticles were tested for antibacterial efficacy against P. aeruginosa and S. aureus. Polyester-epoxy powder coatings were superior to the other coatings in terms of uniformity and stability under moist conditions and displayed antimicrobial properties against both organisms (>4.92 log₁₀) after six hours at 0.25% Cu. Polyester-epoxy coatings were selected for more rigorous testing under adverse conditions. These surfaces were negatively impacted when tested under dry conditions with high organic content, with organic content appearing to have a greater impact on antimicrobial efficacy. At 0.25% Cu, the antibacterial activity of the powder coatings was not impacted by washing with several commercial cleaners; however, at concentrations of 0.05% Cu, antibacterial activity was reduced by multiple washings with water, Windex®, and Pine Sol®. Additionally, ultrasonic cleaning of the coatings appeared to decrease their antimicrobial efficacy. Despite this, CuI nanoparticles were found in all studies to have great potential as a new class of fast-acting, broad-spectrum antimicrobial.
41
Korshed, Peri. "The molecular mechanisms of the antimicrobial properties of laser processed nano-particles." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/the-molecular-mechanisms-of-the-antimicrobial-properties-of-laser-processed-nanoparticles(731afee1-17f3-4698-b182-b604fb48492f).html.
Анотація:
Microbial resistance to the current available antibiotics is considered a global health problem, especially for the Multi-Drug Resistant pathogens (MDR) including methicillin resistant Staphylococcus aureus. Recently nanoparticles (NPs) have been involved in variety of antimicrobial applications due to their unique properties of antibacterial effects. However, the molecular mechanisms behind their antibacterial activity are still not fully understood. In this study, we produced silver Ag NPs (average size 27 nm) and silver-Titanium Ag-TiO2 NPs (average size 47 nm) using picosecond laser ablation. Our results showed that both laser NPs had obvious size-dependent antibacterial activity. The laser Ag NPs with a size of 19 nm and Ag-TiO2 NPs with a size 20 nm presented the highest bactericidal effect. The laser generated Ag and Ag-TiO2 NPs with concentrations 20, 30, 40, and 50 Î1⁄4g/ml showed strong antibacterial effect against three bacterial strains: E. coli, P. aeruginosa, and S. aureus, and induced the generation of reactive oxygen species (ROS), lead to cell membrane interruption, lipid peroxidation, DNA damages, glutathione depletion and the eventual cell death. Both types of laser NPs at two concentrations (2.5 and 20 Î1⁄4g/ml) showed low cytotoxicity to the in vitro cultured five types of human cells originated from the lung (A549), kidney (HEK293), Liver (HepG2), skin (HDFc) and blood vessel cells (hCAECs). The antibacterial activity of the laser generated Ag and Ag-TiO2 NPs had lasted for over one year depending on the degree of air exposure and storage conditions. Frequent air exposure increased particle oxidation and reduced the antibacterial durability of the laser generated Ag NPs. The laser generated Ag NPs had lower antibacterial activity when stored in cold compared to that stored at room temperature. The antibacterial activity of laser generated Ag and Ag-TiO2 NPs were also compared with four types of commercial based-silver wound dressings (Acticoat TM, Aquacel® Ag, Contreet ®Foam, and Urgotul® SSD) against E. coli to inform future application in this area. In conclusion, laser generated Ag and Ag-TiO2 NPs have strong bactericidal effect and low toxicity to human cells which could be a type of promising antibacterial agents for future hygiene and medical applications.
42
Dodge, Luke A. "FRACTIONATION OF LIGNIN DERIVED COMPOUNDS FROM THERMOCHEMICALLY PROCESSED LIGNIN TOWARDS ANTIMICROBIAL PROPERTIES." UKnowledge, 2018. https://uknowledge.uky.edu/bae_etds/54.
Анотація:
The overuse of antibiotics in agriculture is an emerging concern, due to their potential detrimental impact to the environment. This study focuses on exploring antimicrobial properties of lignin derived compounds. Lignin is of interest as a feedstock to replacing some petroleum-based chemicals and products because it is the most abundant source of renewable aromatic compounds on the planet. Two lignin rich streams, residues from the enzymatic hydrolysis of dilute acid and alkaline pretreated corn stover, were decomposed via pyrolysis and hydrogenolysis, respectively. The resulting liquid oils were subjected to sequential extractions using a series of solvents with different polarities. Chemical compositions of the extracted fractions were characterized through HPLC and GC/MS. These extracted compounds were screened against Saccharomyces cerevisiae (S. cerevisiae), Escherichia coli, and Lactobacillus amylovorus for antimicrobial properties. Six lignin model monomers: guaiacol, vanillin, vanillic acid, syringaldehyde, 2,6-dimethoxyphenol, and syringic acid were compared to the oils and extracted fractions for antimicrobial properties. Development of lignin-derived chemicals with antimicrobial properties could provide a novel use for this underutilized natural resource.
43
Munir, Muhammad Tanveer. "Wood and hospital hygiene : Investigating the hygienic safety and antimicrobial properties of wood materials." Thesis, Ecole centrale de Nantes, 2021. http://www.theses.fr/2021ECDN0008.
Анотація:
Le matériau bois est un composant bien connu des thèmes de construction basés sur la nature en raison de son aspect naturel, de sa nature écologique et de ses effets biophiles chez l'homme. L'utilisation de ce matériau dans des endroits sensibles sur le plan de l'hygiène est toutefois remise en question en raison de sa nature organique et poreuse. Des études antérieures ont montré que le bois possède des propriétés antimicrobiennes contre de nombreux microorganismes importants du point de vue de l'hygiène. Les travaux sont encore nécessaires pour démontrer cette action antimicrobienne et sa relation avec le bois et les variables microbiologiques. Cette recherche visait à rassembler et à générer des informations pour guider les acteurs de l'hygiène hospitalière en ce qui concerne la sécurité hygiénique du matériau bois. Les méthodes ont été développées pour étudier l'action antimicrobienne du bois et identifier les variables qui influencent ce comportement. La première méthode développée dans ce contexte a été une méthode de diffusion directe sur gélose (appelée antiboisgram) qui a donné de bons résultats en ce qui concerne le - - dépistage de plusieurs espèces de bois pour leur action antibactérienne et antifongique. Elle a également permis d'identifier le rôle du bois et des variables microbiennes dans la détermination des propriétés antimicrobiennes du matériau en bois. En outre, une méthode de récupération bactérienne basée sur l'élution a été étudiée, qui a montré que la plupart des bactéries nosocomiales courantes survivent moins bien sur le bois que sur les surfaces lisses. Parallèlement, un outil innovant a été mis au point, impliquant l'utilisation de sondes fluorescentes pour étudier la distribution des bactéries sur et à l'intérieur des matériaux en bois à l'aide de la microscopie laser spectrale confocale. Ces expériences ont permis d'obtenir des informations fructueuses qui pourraient améliorer la compréhension du rôle du bois dans la sécurité hygiénique des bâtiments de soins de santé. En outre, les futures recherches et les directives d'application ont été fournies concernant la prévalence des pathogènes dans les bâtiments de soins de santé en bois et la perception des occupants des hôpitaux vis-à-vis de l'environnement intérieur en boisThe wood material provides a nature-based theme to construction because of its natural appearance, ecofriendly nature and biophilic effects on humans. However, its organic and porous nature is questioned when using it in hygienically important places such as hospitals. Studies have shown that wood has antimicrobial properties against some pathogens; work is still needed, however, to demonstrate this antimicrobial action and its relation to wood and microbiological variables. This research gathers and generates information to guide stakeholders of hospital hygiene on the hygienic safety of wood materials. First, a simple and direct method was developed to study the antibacterial and antifungal activity of solid wood, which also identified the role of wood and microbial variables on antimicrobial behavior. Further, an elution based bacterial recovery method was investigated which showed that the most common nosocomial bacteria did not survive as well on wood as compared to smooth surfaces such as aluminum, steel and polycarbonate. Meanwhile, an innovative tool was developed, involving the use of fluorescent probes to study the bacterial distribution on and inside wood using confocal spectral laser microscopy. These experiments produced the information that will help the decision makers regarding the choice of wood material in the healthcare buildings. It not only enhances our understanding of hygienic safety of wood in healthcare buildings but also provides the basis for future research on the prevalence of pathogens in the wooden healthcare institutes and the perception of the occupants those buildings
44
Zhang, Tian. "Investigation of The Structure-Property Correlations of Pendent Functionalized Antimicrobial Polyurethanes." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1522936710295726.
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Korkmaz, Erdural Beril. "Photocatalytic Antimicrobial And Self-cleaning Properties Of Titania-silica Mixed Oxide Thin Films." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12615137/index.pdf.
Анотація:
In this study photocatalytic antibacterial and self-cleaning activities of TiO2-SiO2 thin films as a function of TiO2/SiO2 ratios were investigated. TiO2-SiO2 mixed oxides were synthesized by sol-gel method and coated over soda-lime glass plates by dip coating technique. Escherichia coli was used as a model microorganism for the photocatalytic antibacterial tests. Degradation rate of methylene blue (MB) molecules was used to characterize photocatalytic self-cleaning activities of thin film surfaces.
The maximum antibacterial activity was achieved over 92 wt% SiO2 containing thin films. However, when the SiO2 content exceeds 92 wt%, photocatalytic antibacterial activity decreased considerably, which was explained by the dilution of TiO2 phase and inaccessibility of TiO2. Increase in photocatalytic antibacterial activity was attributed to increases in the relative surface area, roughness, hydroxyl (OH-) groups and bacterial adhesion. The favored bacterial adhesion enhanced direct contact of bacteria with TiO2 particles and surface reactive oxygen species.
The highest initial decomposition rate of MB was obtained for 60 wt% SiO2 and the activity decreases as SiO2 concentration increases. The increase in photocatalytic activity by the SiO2 addition can be explained by the increase of the amount of MB per unit area of TiO2-SiO2 thin films.
Different adsorption capability of thin films against MB molecule and E. coli cell was explained as the first reason why the antibacterial and self-cleaning activities reached their maximum values at different SiO2 ratios. The second reason could be related with the different control mechanisms of self-cleaning and antibacterial activities by different textural and surface properties.
46
Deyrieux, Charlotte. "Identification, characterisation and application of plant extracts with combined antioxidant and antimicrobial properties." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTG070.
Анотація:
L’oxydation et le développement microbien constituent les paramètres majeurs à l’origine de l’altération des produits alimentaires, notamment des aliments pour animaux. Ces dégradations affectent les qualités nutritionnelles et sensorielles des produits et peuvent avoir des répercussions au niveau sanitaire. Dans ce contexte, différents moyens de prévention sont disponibles pour limiter ces phénomènes. Parmi eux, la valorisation d’ingrédients d’origine végétale à des fins alimentaires représente un enjeu majeur pour la recherche et l’industrie. Leur utilisation en tant que conservateurs naturels pourrait constituer une alternative attractive aux antioxydants et antimicrobiens synthétiques qui souffrent d’une moindre acceptation par le consommateur.Au travers de cette étude nous avons identifié et caractérisé la performance de quinze extraits végétaux d’un point de vue antioxydant et antimicrobien. Après une caractérisation moléculaire des extraits, leur pouvoir antioxydant a été mesuré puis leur pouvoir antimicrobien sur trois souches de Salm onella. Pour cela, une procédure de sélection a été mise en place. Enfin les extraits présentant les caractéristiques les plus intéressantes ont été testés sur une vraie matrice alimentaire : des croquettesOxidation and microbial growth are the major parameters causing the deterioration of food products, including pet food. These degradations affect the nutritional and sensory qualities of the products and may lead to health issues. In this context, various ways of prevention are available to limit these phenomena. Among them, the promotion of plant extracts for food is a major challenge for research and industry. Their use as natural preservatives could be an attractive alternative to synthetic antioxidants or antimicrobials that suffer from lower consumer acceptance.Through this study we have identified and characterized the performance of fifteen plant extracts from an antioxidant and antimicrobial point of view. After a molecular characterization of the extracts, their antioxidant capacity was measured as well as their antimicrobial property on three Salmonella strains. The establishment of a selection procedure was made. Finally, the extracts presenting the most interesting characteristics were tested on a real food matrix: kibbles
47
Oree, Glynis. "Chitin hydrolysis with chitinolytic enzymes for the production of chitooligomers with antimicrobial properties." Thesis, Rhodes University, 2019. http://hdl.handle.net/10962/67887.
Анотація:
There are many diseases and illnesses in the world that require new drug treatments and chitin has been shown to produce chitooligomeric derivatives which exhibit promising antimicrobial and immune-enhancing properties. However, the rate-limiting step is associated with the high recalcitrance of chitinous substrates, and low hydrolytic activities of chitinolytic enzymes, resulting in low product release. To improve and create a more sustainable and economical process, enhancing chitin hydrolysis through various treatment procedures is essential for obtaining high enzyme hydrolysis rates, resulting in a higher yield of chitooligomers (CHOS). In literature, pre-treatment of insoluble biomass is generally associated with an increase in accessibility of the carbohydrate to hydrolytic enzymes, thus generating more products. The first part of this study investigated the effect of alkali- (NaOH) and acid pre-treatments (HCl and phosphoric acid) on chitin biomass, and chemical and morphological modifications were assessed by the employment of scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Energy-Dispersive X-ray spectrometery (EDX) and x-ray diffraction (XRD). Data obtained confirmed that pre-treated substrates were more chemically and morphologically modified. These results confirmed the fact that pre-treatment of chitin disrupts the structure of the biomass, rendering the polymer more accessible for enzymatic hydrolysis. The commercial chitinases from Bacillus cereus and Streptomyces griseus (CHB and CHS) are costly. Bio-prospecting for other chitin-degrading enzymes from alternate sources such as Oidiodendron maius, or the recombinant expression of CHOS, was a more economically feasible avenue. The chit1 gene from Thermomyces lanuginosus, expressed in Pichia pastoris, produced a large range CHOS with a degree of polymerisation (DP) ranging from 1 to above 6. TLC analysis showed that O. maius exhibited chitin-degrading properties by producing CHOS with a DP length of 1 to 3. These two sources were therefore successful in producing chitin-degrading enzymes. The physico-chemical properties of commercial (CHB and CHS) and expressed (Chit1) chitinolytic enzymes were investigated, to determine under which biochemical conditions and on which type of biomass they can function on optimally, for the production of value-added products such as CHOS. Substrate affinity assays were conducted on the un-treated and pre-treated biomass. TLC revealed that chitosan hydrolysis by the commercial chitinases produced the largest range of CHOS with a DP length ranging from 1 to 6. A range of temperatures (35-90oC) were investigated and CHB, CHS and Chit1 displayed optimum activities at 50, 40 and 45 oC, respectively. Thermostability studies that were conducted at 37 and 50oC revealed that CHB and CHS were most stable at 37oC. Chit1 showed great thermostablity at both temperatures, rendering this enzyme suitable for industrial processes at high temperatures. pH optima studies demonstrated that the pH optima for CHB, CHS and Chit1 was at a pH of 5.0, with specific activities of 33.459, 46.2 and 5.776 μmol/h/mg, respectively. The chain cleaving patterns of the commercial enzymes were determined and exo-chitinase activity was exhibited, due to the production of CHOS that were predominantly of a DP length of 2. Enzyme binary synergy studies were conducted with commercial chitinases (CHB and CHS) on colloidal chitin. Studies illustrated that the simultaneous combination of CHB 75%: CHS 25% produced the highest specific activity (3.526 μmol/h/mg), with no synergy. TLC analysis of this enzyme combination over time revealed that predominantly chitobiose was produced. This suggested that the substrate crystallinity and morphology played an important role in the way the enzymes cleaved the carbohydrate. Since CHOS have shown great promise for their antimicrobial properties, the CHOS generated from the chitinous substrates were tested for antimicrobial properties on Bacillus subtilis, Escherichia coli, Klebsiella and Staphlococcus aureus. This study revealed that certain CHOS produced have inhibitory effects on certain bacteria and could potentially be used in the pharamceutical or medical industries. In conclusion, this study revealed that chitinases can be produced and found in alternate sources and be used for the hydrolysis of chitinous biomass in a more sustainabe and economically viable manner. The chitinases investigated (CHB, CHS and Chit1) exhibited different cleaving patterns of the chitinous substrates due to the chemical and morphological properties of the biomass. CHOS produced from chitinous biomass exhibited some inhibitory effects on bacterial growth and show potential for use in the medical industry.
48
Van, der Vyver Petrus Jacobus. "Antimicrobial properties and smear layer management of nine different root canal irrigation solutions." Diss., Pretoria : [s.n.], 2007. http://upetd.up.ac.za/thesis/available/etd-082222008-163721/.
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Al-Dulaimi, Omar Ahmed Abass. "Phytochemical composition and antimicrobial properties of four plants indicated for traditional medicine use." Thesis, Keele University, 2017. http://eprints.keele.ac.uk/3078/.
Анотація:
The rapid development of seriously drug-resistant pathogen strains has created a dangerous problem to public health. The discovery of new effective antimicrobials remains an urgent task to control microbial resistance. Natural products can offer special stereochemistry and unlimited diversity of natural leads which are biologically active or ready for development and structure optimization strategies. Four medicinal plants Cylicodiscus gabunensis (CG), Pogostemon cablin (PC), Perilla frutescens (PF) and Magnolia biondii (MB) were selected for investigation of their phytochemical composition and antiplasmodial and/or antibacterial properties. A bioassay guided fractionation method has been followed to characterize the antiplasmodial and antibacterial constituents of CG. Flash column chromatography and preparative HPLC were used to obtain the bioactive compounds. GC-MS, LC-MS, and NMR have been used for chemical analysis purposes. For evaluation of the antibacterial activity, disk diffusion assay, alamar blue microplate assay, time kill kinetic and scanning electron microscopy (SEM) methods have been used. The work led to the isolation of the most potent antiplasmodial fraction of CG with IC50 of 4.7.
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CALAMELLO, CATERINA. "TRP ACTIVE COMPOUNDS FROM FOOD PLANTS AND THEIR PROPERTIES AS ANTIMICROBIAL AND BIOCIDES." Doctoral thesis, Università degli Studi di Milano, 2012. http://hdl.handle.net/2434/168879.
Анотація:
Nowadays plant derived compounds constitute a promising resource in ecofriendly pest and diseases management because they are ‘generally recognized as safe’ (GRAS). Plants have evolved ingenious defense mechanisms by production of pungent and irritant compounds. These substances produce their psychophysical effects by targeting the TRPA1 receptor, belonging to transient receptor potential (TRP) channels. Two secondary metabolites contained in the Asian food plant Perilla frutescens, perillaldehyde (PA) and perillaketone (PK), are potent agonists of TRPA1. The aim of the present PhD project was to determine the antimicrobial activity of the crude extracts and essential oils from the leaves of two Perilla frutescens varieties grown experimentally in Northern Italy. Commercial PA and PK, obtained by chemical synthesis, were also assayed in vitro and in vivo (PA, only). In addition, the nematicidal efficacy of pure PK was evaluated against 2nd instar larvae juveniles of cyst nematode Heterodera daverti. Chemical analysis allowed the identification of PA and PK as the main constituents in the two investigated cultivars respectively, and the consequent classification in PA and PK chemotypes. The organic extracts PA and PK-type (PA-Ex and PK-Ex) and the essential oils PA and PK type (PA-EO and PK-EO) exhibited a broad spectrum of activity against tested phytopatogenic organisms. The antibacterial activity of the tested substances resulted generally scanty. In vitro antifungal activity varied according to compound and target species. The essential oils appeared to be significantly more active compared with the crude extracts. At 500 µg mL-1 PA-EO showed fungicidal activity against several fungi while PK-EO exhibited a fungistatic one. Both oils and commercial PA displayed high inhibition on Cladosporium cladosporoides IPV-F167 spore germination, while PA-Ex and pure PA proved good preventive activity reducing powdery mildew disease on cucumber plants. Besides, P. frutescens demonstrated to possess efficient nematicidal activity due to PK.