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"Pilado add Value": valorisation of non-traditional marine resources

Avelelas, Francisco Pires
Fonte: Instituto Politécnico de Leiria Publicador: Instituto Politécnico de Leiria
Tipo: Dissertação de Mestrado
Publicado em //2013 POR
Relevância na Pesquisa
56.36%
Dissertação para obtenção do Grau de Mestre em Biotecnologia dos Recursos Marinhos apresentada à ESTM - Escola Superior de Turismo e Tecnologia do Mar do Instituto Politécnico de Leiria.; In recent years, the valorisation of by-products resulted from fisheries discards has received much attention due to the awareness of economic and environmental negative impacts. However, the crustacean shellfish by-products contain several compounds that can be processed to yield chitin which has a myriad of industrial and biotechnological applications. The swimming crab, Polybius henslowii, despite being an extremely abundant marine resource, it is not presently subject to commercial use. Given the negative impact on the fishing nets fisherman´s see this marine resource as a plague and not as a potential source of economic incomes. Thereby, this work aims to be a contribution for the economic valorisation of Polybius henslowii as a raw material for polymer extraction, aiming for biotechnological purposes. Chitin and chitosan were extracted and produced from segmented body parts of Polybius henslowii: pereopods and carapace. Chitosan served then as raw material for the production of water-soluble chitosans (WSC) and chitooligosaccharides (COS)...

Chitosan as a Bioadhesive Agent Between Porphyrins and Phospholipids in a Biomembrane Model

LUZ, Priscilla P.; NOBRE, Thatyane M.; SERRA, Osvaldo A.; ZANIQUELLI, Maria E. D.
Fonte: AMER SCIENTIFIC PUBLISHERS Publicador: AMER SCIENTIFIC PUBLISHERS
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.18%
Porphyrins are currently used in photodynamic therapy as photosensitizers. In this paper we studied the interaction of two charged porphyrins, 5, 10, 15, 20-mesotetrakis(N-metyl-4-pyridyl) porphyrin, (TMPyP/chloride salt) cationic, and 5, 10, 15, 20-meso-tetrakis(sulfonatophenyl) porphyrin, (TPPS(4)/sodium salt) anionic, nanoassembled in phospholipid Langmuir monolayers and Langmuir-Blodgett films. Furthermore, we used chitosan to mediate the interaction between the porphyrins and the model membrane, aiming to understand the role of the polysaccharide in a molecular level. The effect of the interaction of the photosensitizers on the fluidity of the lipid monolayer was investigated by using dilatational surface elasticity. We also used photoluminescence (PL) spectroscopy to identify the porphyrins adsorbed in the phospholipid films. We observed an expansion of the monolayer promoted by the adsorption of the porphyrins into the lipid-air interface which was more pronounced in the case of TMPyP, as a consequence of a strong electrostatic interaction with the anionic monolayer. The chitosan promoted a higher adsorption of the porphyrins on the phospholipid monolayers and enabled the porphyrin to stay in its monomeric form (as confirmed by PL spectroscopy)...

Immobilization of fibronectin in chitosan substrates improves cell adhesion and proliferation

Custódio, Catarina A.; Alves, C. M.; Reis, R. L.; Mano, J. F.
Fonte: Wiley Publicador: Wiley
Tipo: Artigo de Revista Científica
Publicado em //2010 POR
Relevância na Pesquisa
46.15%
Covalent grafting of biomolecules is a strategy to improve the biocompatibility and bioactivity of materials. However, it is critical to maintain the biological activity of the biomolecule upon its attachment to the surface. In the present study we compared the biological properties of chitosan, in which the surface was enriched with fibronectin (Fn), using two methodologies: chemical immobilization, using a water-soluble carbodiimide; and simple adsorption. X-ray photoelectron spectroscopy studies confirmed the successful immobilization of Fn onto modifiedmembranes. SaOs- 2 cells were seeded onto these surfaces to assess the biological consequences of such modifications. The presence of Fn stimulated cell adhesion on chitosan. It was found that after 7 days of culture in the presence of covalently attached Fn, the cells are confluent; significantly fewer cells were detected in unmodified film and in film with adsorbed Fn. This result is consistent with the fact that considerable desorption of Fn from chitosan takes place within 24 h in culture medium. This study showed that Fn may be easily covalently attached onto chitosan substrates, improving the biological performance of the material. The technique could find applications in tissue-engineering strategies...

Novel materials based on chitosan, its derivatives and cellulose fibres

Fernandes, Susana Cristina de Matos
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Tese de Doutorado
ENG
Relevância na Pesquisa
46.56%
O presente trabalho tem como principal objectivo o desenvolvimento de novos materiais baseados em quitosano, seus derivados e celulose, na forma de nanofibras ou de papel. Em primeiro lugar procedeu-se à purificação das amostras comerciais de quitosano e à sua caracterização exaustiva em termos morfológicos e físicoquímicos. Devido a valores contraditórios encontrados na literatura relativamente à energia de superfície do quitosano, e tendo em conta a sua utilização como precursor de modificações químicas e a sua aplicação em misturas com outros materiais, realizou-se também um estudo sistemático da determinação da energia de superfície do quitosano, da quitina e seus respectivos homólogos monoméricos, por medição de ângulos de contacto Em todas as amostras comerciais destes polímeros identificaram-se impurezas não polares que estão associadas a erros na determinação da componente polar da energia de superfície. Após a remoção destas impurezas, o valor da energia total de superfície (gs), e em particular da sua componente polar, aumentou consideravelmente. Depois de purificadas e caracterizadas, algumas das amostras de quitosano foram então usadas na preparação de filmes nanocompósitos, nomeadamente dois quitosanos com diferentes graus de polimerização...

Production of Coated Papers with Improved Properties by Using a Water-Soluble Chitosan Derivative

Fernandes, Susana C. M.; Freire, Carmen S. R.; Silvestre, Armando J. D.; Desbrières, Jacques; Gandini, Alessandro; Neto, Carlos Pascoal
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.51%
Eucalyptus globulus-based paper sheets were coated with chitosan and a water-soluble chitosan derivative on a pilot-size press machine. Different coating weights were attained by the deposition of 1-5 coating layers. The morphological, mechanical, barrier, and optical properties as well as the paper aging and inkjet print quality of the ensuing coated papers were investigated and assessed. In general, both chitosan and water-soluble chitosan coatings had a positive impact on the final properties of the coated papers, which was quite dependent on the number of deposited chitosan layers. The results obtained also showed that the water-soluble chitosan-coated papers presented superior optical properties and printability and better results on aging measurements than chitosan-coated papers. Therefore, the use of water-soluble chitosan derivatives on paper coating processes represents an interesting and sustainable strategy for the development of new functional paper materials or for the improvement of the end-user properties of paper products.; FCT - SFRH/BD/41388/2007

A review of the antimicrobial activity of chitosan

Goy,Rejane C.; Britto,Douglas de; Assis,Odilio B. G.
Fonte: Associação Brasileira de Polímeros Publicador: Associação Brasileira de Polímeros
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 EN
Relevância na Pesquisa
56.15%
Chitosan, a versatile hydrophilic polysaccharide derived from chitin, has a broad antimicrobial spectrum to which gram-negative, gram-positive bacteria and fungi are highly susceptible. In the current review, three possible and accepted antimicrobial mechanisms for chitosan are presented and briefly discussed. The activity dependence on polymeric molecular weight (MW) and degree of acetylation (DA) are described. The chitosan minimum inhibitory concentrations (MIC) are summarized according to recent data found in the literature. The potential to improve inhibitory growth of bacteria by using water soluble chitosan derivatives is also discussed. The data indicate that the effectiveness of chitosan varies and is dependent on species of target microorganisms.

Antibacterial activity of chitosan and the interpolyelectrolyte complexes of poly(acrylic acid)-chitosan

Ortega-Ortiz,Hortensia; Gutiérrez-Rodríguez,Baltazar; Cadenas-Pliego,Gregorio; Jimenez,Luis Ibarra
Fonte: Instituto de Tecnologia do Paraná - Tecpar Publicador: Instituto de Tecnologia do Paraná - Tecpar
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2010 EN
Relevância na Pesquisa
46.15%
The antimicrobial activity of chitosan and water soluble interpolyelectrolyte complexes of poly(acrylic acid)-chitosan was studied. Chitosans of two different molecular weights were tested at different concentration for 0.5 to 5 g·L-1 as antimicrobial agents against P. aeruginosa and P. oleovorans. In both cases, the best microbial inhibition was obtained with the concentration of 5 g·L-1. However, the interpolyelectrolyte complexes of poly(acrylic acid)-chitosan with composition φ =2 produced higher antibacterial activity than the two chitosans at the concentration of 0.5 g·L-1. The NPEC2 complex was more effective than chitosans. This could be attributed to the number of moles of the amino groups of chitosan and the carboxylic acid groups of the interpolyelectrolyte complexes poly(acrylic acid).

Antibacterial effect of water-soluble chitosan on representative dental pathogens Streptococcus mutans and Lactobacilli brevis

Chen,Chih-Yu; Chung,Ying-Chien
Fonte: Faculdade De Odontologia De Bauru - USP Publicador: Faculdade De Odontologia De Bauru - USP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2012 EN
Relevância na Pesquisa
76.63%
Dental caries is still a major oral health problem in most industrialized countries. The development of dental caries primarily involves Lactobacilli spp. and Streptococcus mutans. Although antibacterial ingredients are used against oral bacteria to reduce dental caries, some reports that show partial antibacterial ingredients could result in side effects. OBJECTIVES: The main objective is to test the antibacterial effect of water-soluble chitosan while the evaluation of the mouthwash appears as a secondary aim. MATERIAL AND METHODS: The chitosan was obtained from the Application Chemistry Company (Taiwan). The authors investigated the antibacterial effects of water-soluble chitosan against oral bacteria at different temperatures (25-37ºC) and pH values (pH 5-8), and evaluated the antibacterial activities of a self-made water-soluble chitosan-containing mouthwash by in vitro and in vivo experiments, and analyzed the acute toxicity of the mouthwashes. The acute toxicity was analyzed with the pollen tube growth (PTG) test. The growth inhibition values against the logarithmic scale of the test concentrations produced a concentrationresponse curve. The IC50 value was calculated by interpolation from the data. RESULTS: The effect of the pH variation (5-8) on the antibacterial activity of water-soluble chitosan against tested oral bacteria was not significant. The maximal antibacterial activity of water-soluble chitosan occurred at 37ºC. The minimum bactericidal concentration (MBC) of water-soluble chitosan on Streptococcus mutans and Lactobacilli brevis were 400 µg/mL and 500 µg/mL...

Microfluidic wet spinning of chitosan-alginate microfibers and encapsulation of HepG2 cells in fibers

Lee, Bo Ram; Lee, Kwang Ho; Kang, Edward; Kim, Dong-Sik; Lee, Sang-Hoon
Fonte: American Institute of Physics Publicador: American Institute of Physics
Tipo: Artigo de Revista Científica
Publicado em 29/06/2011 EN
Relevância na Pesquisa
46.17%
The successful encapsulation of human hepatocellular carcinoma (HepG2) cells would greatly assist a broad range of applications in tissue engineering. Due to the harsh conditions during standard chitosan fiber fabrication processes, encapsulation of HepG2 cells in chitosan fibers has been challenging. Here, we describe the successful wet-spinning of chitosan-alginate fibers using a coaxial flow microfluidic chip. We determined the optimal mixing conditions for generating chitosan-alginate fibers, including a 1:5 ratio of 2% (w∕w) water-soluble chitosan (WSC) solution to 2% (w∕w) alginate solution. Ratio including higher than 2% (w∕w) WSC solution increased aggregation throughout the mixture. By suspending cells in the WSC–alginate solution, we successfully fabricated HepG2 cell-laden fibers. The encapsulated HepG2 cells in the chitosan-alginate fibers were more viable than cells encapsulated in pure alginate fibers, suggesting that cross-linked chitosan provides a better environment for HepG2 cells than alginate alone. In addition, we found that the adhesion of HepG2 cells on the chitosan-alginate fiber is much better than that on the alginate fibers.

Transcriptional Responses of Bacillus cereus towards Challenges with the Polysaccharide Chitosan

Mellegård, Hilde; Kovács, Ákos T.; Lindbäck, Toril; Christensen, Bjørn E.; Kuipers, Oscar P.; Granum, Per E.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 08/09/2011 EN
Relevância na Pesquisa
46.15%
The antibacterial activity of the polysaccharide chitosan towards different bacterial species has been extensively documented. The response mechanisms of bacteria exposed to this biopolymer and the exact molecular mechanism of action, however, have hardly been investigated. This paper reports the transcriptome profiling using DNA microarrays of the type-strain of Bacillus cereus (ATCC 14579) exposed to subinhibitory concentrations of two water-soluble chitosan preparations with defined chemical characteristics (molecular weight and degree of acetylation (FA)). The expression of 104 genes was significantly altered upon chitosan A (weight average molecular weight (Mw) 36.0 kDa, FA = 0.01) exposure and 55 genes when treated with chitosan B (Mw 28.4 kDa, FA = 0.16). Several of these genes are involved in ion transport, especially potassium influx (BC0753-BC0756). Upregulation of a potassium transporting system coincides with previous studies showing a permeabilizing effect on bacterial cells of this polymer with subsequent loss of potassium. Quantitative PCR confirmed the upregulation of the BC0753 gene encoding the K+-transporting ATPase subunit A. A markerless gene replacement method was used to construct a mutant strain deficient of genes encoding an ATP-driven K+ transport system (Kdp) and the KdpD sensor protein. Growth of this mutant strain in potassium limiting conditions and under salt stress did not affect the growth pattern or growth yield compared to the wild-type strain. The necessity of the Kdp system for potassium acquisition in B. cereus is therefore questionable. Genes involved in the metabolism of arginine...

Enhanced cellular uptake and long-term retention of chitosan-modified iron-oxide nanoparticles for MRI-based cell tracking

Bakhru, Sasha H; Altiok, Eda; Highley, Christopher; Delubac, Daniel; Suhan, Joseph; Hitchens, T Kevin; Ho, Chien; Zappe, Stefan
Fonte: Dove Medical Press Publicador: Dove Medical Press
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.15%
Tracking cells after therapeutic transplantation is imperative for evaluation of implanted cell fate and function. In this study, ultrasmall superparamagnetic iron oxide nanoparticles (USPIO NPs) were surface functionalized with water-soluble chitosan, a cationic polysaccharide that mediates enhanced endocytic uptake, endosomal escape into the cytosol, and subsequent long-term retention of nanoparticles. NP surface and chitosan were independently fluorescently labeled. Our NPs enable NP trafficking studies and determination of fate beyond uptake by fluorescence microscopy as well as tracking of labeled cells as localized regions of hypointensity in T2*-weighted magnetic resonance imaging (MRI) images. Adult rat neural stem cells (NSCs) were labeled with NPs, and assessment of NSC proliferation rates and differentiation potential revealed no significant differences between labeled and unlabeled NSCs. Significantly enhanced uptake of chitosan NPs in comparison to native NPs was confirmed by transmission electron microscopy, nuclear magnetic resonance (NMR) spectroscopy and in vitro cellular MRI at 11.7 Tesla. While only negligible fractions of native NPs enter cells, chitosan NPs appear within membranous vesicles within 2 hours of exposure. Additionally...

Preparation of Chitosan and Water-Soluble Chitosan Microspheres via Spray-Drying Method to Lower Blood Lipids in Rats Fed with High-Fat Diets

Tao, Yi; Zhang, Hong-Liang; Hu, Yin-Ming; Wan, Shuo; Su, Zheng-Quan
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 19/02/2013 EN
Relevância na Pesquisa
66.24%
This experiment aimed to investigate the effects of the chitosan (CTS) and water-soluble chitosan (WSC) microspheres on plasma lipids in male Sprague-Dawley rats fed with high-fat diets. CTS microspheres and WSC microspheres were prepared by the spray-drying technique. Scanning electron microscopy (SEM) micrographs showed that the microspheres were nearly spherical in shape. The mean size of CTS microspheres was 4.07 μm (varying from 1.50 to 7.21 μm) and of WSC microspheres was 2.00 μm (varying from 0.85 to 3.58 μm). The rats were classified into eight groups (n = 8) and were fed with high-fat diets for two weeks to establish the hyperlipidemic condition and were then treated with CTS microspheres and WSC microspheres, CTS and WSC for four weeks. The results showed that CTS and WSC microspheres reduced blood lipids and plasma viscosity and increased the serum superoxide dismutase (SOD) levels significantly. This study is the first report of the lipid-lowering effects of CTS and WSC microspheres. CTS and WSC microspheres were found to be more effective in improving hyperlipidemia in rats than common CTS and WSC.

Oxidative Degradation of Chitosan to the Low Molecular Water-Soluble Chitosan over Peroxotungstate as Chemical Scissors

Ma, Zhanwei; Wang, Wenyan; Wu, Ying; He, Yiming; Wu, Tinghua
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 27/06/2014 EN
Relevância na Pesquisa
66.3%
Low molecular water-soluble chitosan was prepared by the depolymerization of chitosan in the presence of a series of catalysts with active W(O2) sites. Both the peroxo species [W2O3(O2)4]2- and {PO4[WO(O2)2]4}3- showed high efficiency in the degradation of chitosan, indicating that the degradation mechanism did not follow the radical mechanism. That means •OH is not the active species, which has been proven by the fluorescence spectra. H2O2 acted as an oxidant to regenerate the active W(O2) sites in the depolymerization of chitosan. The developed catalyst (TBA)3{PO4[WO(O2)2]4} is recoverable.

Antimicrobial Activity of Chitosan Derivatives Containing N-Quaternized Moieties in Its Backbone: A Review

Martins, Alessandro F.; Facchi, Suelen P.; Follmann, Heveline D. M.; Pereira, Antonio G. B.; Rubira, Adley F.; Muniz, Edvani C.
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 13/11/2014 EN
Relevância na Pesquisa
46.17%
Chitosan, which is derived from a deacetylation reaction of chitin, has attractive antimicrobial activity. However, chitosan applications as a biocide are only effective in acidic medium due to its low solubility in neutral and basic conditions. Also, the positive charges carried by the protonated amine groups of chitosan (in acidic conditions) that are the driving force for its solubilization are also associated with its antimicrobial activity. Therefore, chemical modifications of chitosan are required to enhance its solubility and broaden the spectrum of its applications, including as biocide. Quaternization on the nitrogen atom of chitosan is the most used route to render water-soluble chitosan-derivatives, especially at physiological pH conditions. Recent reports in the literature demonstrate that such chitosan-derivatives present excellent antimicrobial activity due to permanent positive charge on nitrogen atoms side-bonded to the polymer backbone. This review presents some relevant work regarding the use of quaternized chitosan-derivatives obtained by different synthetic paths in applications as antimicrobial agents.

Design of Chitosan and Its Water Soluble Derivatives-Based Drug Carriers with Polyelectrolyte Complexes

Wu, Qing-Xi; Lin, Dong-Qiang; Yao, Shan-Jing
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 19/12/2014 EN
Relevância na Pesquisa
46.36%
Chitosan, the cationic polysaccharide derived from the natural polysaccharide chitin, has been studied as a biomaterial for more than two decades. As a polycationic polymer with favorable properties, it has been widely used to form polyelectrolyte complexes with polyanions for various applications in drug delivery fields. In recent years, a growing number of studies have been focused on the preparation of polyelectrolyte complexes based on chitosan and its water soluble derivatives. They have been considered well-suited as biomaterials for a number of vital drug carriers with targeted/controlled release profiles, e.g., films, capsules, microcapsules. In this work, an overview highlights not only the favorable properties of chitosan and its water soluble derivatives but also the good performance of the polyelectrolyte complexes produced based on chitosan. Their various types of applications as drug carriers are reviewed in detail.

Antimicrobial Action of Water-Soluble β-Chitosan against Clinical Multi-Drug Resistant Bacteria

Park, Seong-Cheol; Nam, Joung-Pyo; Kim, Jun-Ho; Kim, Young-Min; Nah, Jae-Woon; Jang, Mi-Kyeong
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 10/04/2015 EN
Relevância na Pesquisa
56.3%
Recently, the number of patients infected by drug-resistant pathogenic microbes has increased remarkably worldwide, and a number of studies have reported new antibiotics from natural sources. Among them, chitosan, with a high molecular weight and α-conformation, exhibits potent antimicrobial activity, but useful applications as an antibiotic are limited by its cytotoxicity and insolubility at physiological pH. In the present study, the antibacterial activity of low molecular weight water-soluble (LMWS) α-chitosan (α1k, α5k, and α10k with molecular masses of 1, 5, and 10 kDa, respectively) and β-chitosan (β1k, β5k, and β10k) was compared using a range of pathogenic bacteria containing drug-resistant bacteria isolated from patients at different pH. Interestingly, β5k and β10k exhibited potent antibacterial activity, even at pH 7.4, whereas only α10k was effective at pH 7.4. The active target of β-chitosan is the bacterial membrane, where the leakage of calcein is induced in artificial PE/PG vesicles, bacterial mimetic membrane. Moreover, scanning electron microscopy showed that they caused significant morphological changes on the bacterial surfaces. An in vivo study utilizing a bacteria-infected mouse model found that LMWS β-chitosan could be used as a candidate in anti-infective or wound healing therapeutic applications.

Transparent chitosan films reinforced with a high content of nanofibrillated cellulose

Fernandes, Susana C.M.; Freire, Carmen S.R.; Silvestre, Armando J.D.; Neto, Carlos Pascoal; Gandini, Alessandro; Berglund, Lars A.; Salmén, Lennart
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.41%
This paper reports the preparation and characterization of nanocomposite films based on different chitosan matrices and nanofibrillated cellulose (NFC) for the purpose of improving strength properties. The nanocomposite films were prepared by a simple procedure of casting a water-based suspension of chitosan and NFC, and were characterized by several techniques: namely SEM, X-ray diffraction, visible spectrophotometry, TGA, tensile and dynamic-mechanical analysis. The films obtained were shown to be highly transparent (transmittance varying between 90 and 20% depending on the type of chitosan and NFC content), flexible, displayed better mechanical properties, with a maximum increment on the Young's modulus of 78% and 150% for high molecular weight (HCH) and water-soluble high molecular weight (WSHCH) filled chitosans, respectively; and of 200% and 320% for low molecular weight (LCH) and water-soluble filled (WSLCH) chitosans, respectively. The filled films also showed increased thermal stability, with, for example, an increase in the initial degradation temperature (Td(i)) from 227 degrees C in the unfilled LCH film up to 271 degrees C in filled LCHNFC50% nanocomposite films, and a maximum degradation temperature (Tdi) raising from 304 degrees C to 313 degrees C for the same materials. (C) 2010 Elsevier Ltd. All rights reserved.; FCT - SFRH/BD/41388/2007; National Program for Scientific re-equipment; Rede/1509/RME/2005; REEQ/515/CTM/2005

Antibacterial action of a novel functionalized chitosan-arginine against gram-negative bacteria

Tang, Hong; Zhang, Peng; Kieft, Thomas L.; Ryan, Shannon J.; Baker, Shenda M.; Wiesmann, William P.; Rogelj, Snezna
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.17%
The antimicrobial activity of chitosan and chitosan derivatives has been well established. However, although several mechanisms have been proposed, the exact mode of action is still unclear. Here we report on the investigation of antibacterial activity and the antibacterial mode of action of a novel water-soluble chitosan derivative, arginine-functionalized chitosan, on the gram-negative bacteria Pseudomonas fluorescens and Escherichia coli. Two different arginine-functionalized chitosans (6% arginine-substituted and 30% arginine-substituted) each strongly inhibited P. fluorescens and E. coli growth. Time-dependent killing efficacy experiments showed that 5000 mg L-1 of 6% substituted and 30% substituted chitosan-arginine killed 2.7 logs and 4.5 logs of P. fluorescens, and 4.8 logs and 4.6 logs of E. coli in 4 h, respectively. At low concentrations, the 6% substituted chitosan-arginine was more effective in inhibiting cell growth even though the 30% substituted chitosan-arginine appeared to be more effective in permeabilizing the cell membranes of both P. fluorescens and E. coli. Studies using fluorescent probes, 1-N-phenylnaphthylamine (NPN), nile red (NR) and propidium iodide (PI), and field emission scanning electron microscopy (FESEM) suggest that chitosan-arginine's antibacterial activity is...

Synthesis and unusual swelling behavior of combined cationic/non-ionic hydrogels based on chitosan

Tapia Villanueva, Cristián; Arias, José Luis; Retuert de la Torre, Pedro Jaime; Yazdani-Pedram Zobeiri, Mehrdad
Fonte: WILEY-V C H VERLAG GMBH Publicador: WILEY-V C H VERLAG GMBH
Tipo: Artículo de revista
EN
Relevância na Pesquisa
46.26%
Hydrogel-forming copolymers based on chitosan grafted with different amounts of polyacrylamide were synthesized and its swelling capacity determined in distilled water, sodium chloride solutions, as well as in buffer solutions at pH 1.2 and 8.0. The resulting products are highly efficient as hydrogel-forming materials with swelling at equilibrium going approximately from 300 to 3000 times the volume of the dry solid polymer in all the investigated media. The products, different to usual hydrogels, swells considerably more and quickly in electrolyte-containing solutions compared to in distilled water. This has been attributed to their structure that contains non-ironic polyacrylamide macromolecules grafted onto the trunk polymer chitosan, which is cationic in nature. In-vitro drug-release behavior of formulations containing grafted copolymers have been tested using theophylline as a water-soluble drug and the results were compared with similar formulations containing unmodified chitosan. It was found that tablets based on formulations containing grafted chitosan show higher erosion and swelling compared with those of the matrix based on unmodified chitosan, leading to a higher fraction of theophylline released. It can be concluded that formulations based on the synthesized copolymers are potentially useful for fluid absorbency and as prolonged drug-release matrices.

Antibacterial effect of water-soluble chitosan on representative dental pathogens Streptococcus mutans and Lactobacilli brevis

Chen, Chih-Yu; Chung, Ying-Chien
Fonte: Universidade de São Paulo. Faculdade de Odontologia de Bauru Publicador: Universidade de São Paulo. Faculdade de Odontologia de Bauru
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; Formato: application/pdf
Publicado em 01/12/2012 ENG
Relevância na Pesquisa
76.63%
Dental caries is still a major oral health problem in most industrialized countries. The development of dental caries primarily involves Lactobacilli spp. and Streptococcus mutans. Although antibacterial ingredients are used against oral bacteria to reduce dental caries, some reports that show partial antibacterial ingredients could result in side effects. OBJECTIVES: The main objective is to test the antibacterial effect of water-soluble chitosan while the evaluation of the mouthwash appears as a secondary aim. MATERIAL AND METHODS: The chitosan was obtained from the Application Chemistry Company (Taiwan). The authors investigated the antibacterial effects of water-soluble chitosan against oral bacteria at different temperatures (25-37ºC) and pH values (pH 5-8), and evaluated the antibacterial activities of a self-made water-soluble chitosan-containing mouthwash by in vitro and in vivo experiments, and analyzed the acute toxicity of the mouthwashes. The acute toxicity was analyzed with the pollen tube growth (PTG) test. The growth inhibition values against the logarithmic scale of the test concentrations produced a concentrationresponse curve. The IC50 value was calculated by interpolation from the data. RESULTS: The effect of the pH variation (5-8) on the antibacterial activity of water-soluble chitosan against tested oral bacteria was not significant. The maximal antibacterial activity of water-soluble chitosan occurred at 37ºC. The minimum bactericidal concentration (MBC) of water-soluble chitosan on Streptococcus mutans and Lactobacilli brevis were 400 µg/mL and 500 µg/mL...