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Physicochemical characterization of nanoparticles formed between DNA and phosphorylcholine substituted chitosans

CASE, Ana Helena; PICOLA, Isadora Pfeifer Dalla; ZANIQUELLI, Maria Elisabete Darbello; FERNANDES, Julio Cesar; TABOGA, Sebastiao Roberto; WINNIK, Francoise M.; TIERA, Marcio Jose
Fonte: ACADEMIC PRESS INC ELSEVIER SCIENCE Publicador: ACADEMIC PRESS INC ELSEVIER SCIENCE
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
27.54%
The interactions between phosphorylcholine-substituted chitosans (PC-CH) and calf-thymus DNA (ct-DNA) were investigated focusing on the effects of the charge ratio, the pH, and phosphorylcholine content on the size and stability of the complexes using the ethidium bromide fluorescence assay, gel electrophoresis, dynamic light scattering. and fluorescence microscopy. The size and colloidal stability of deacetylated chitosan (CH/DNA) and PC-CH/DNA complexes were strongly dependent on phosphorylcholine content, charge ratios, and pH. The interaction strengths were evaluated from ethidium bromide fluorescence, and at N/P ratios higher than 5.0, no DNA release was observed in any synthesized PC-CH/DNA polyplexes by gel electrophoresis. The PC-CH/DNA polyplexes exhibited a higher resistance to aggregation compared to deacetylated chitosan (CH) at neutral pH. At low pH values highly charged chitosan and its phosphorylcholine derivatives had strong binding affinity with DNA, whereas at higher pH Values CH formed large aggregates and only C-CH derivatives were able to form small nanoparticles with hydrodynamic radii varying from 100 to 150 nm. Nanoparticles synthesized at low ionic strength with PC-CH derivatives containing moderate degrees of substitution (DS = 20% and 40%) remained stable for weeks. Photomicroscopies also confirmed that rhodamine-labeled PC(40)CH derivative nanoparticles presented higher colloidal stability than those synthesized using deacetylated chitosan. Accordingly...

Desacetilação assistida por irradiação de ultrassom de alta intensidade aplicada a quitinas extraídas de gládios de lulas; Ultrasound-assisted deacetylation applied to extracted chitins of squid pens

Gonzaga, Virgínia de Alencar Muniz
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 10/12/2012 PT
Relevância na Pesquisa
18.23%
Neste trabalho, amostras de beta-quitina extraída de gládios de lulas foram submetidas ao processo DAIUS, desacetilação assistida por irradiação de ultrassom de alta intensidade, visando à produção de quitosanas extensivamente desacetiladas e de massa molar elevada. Para isso, os parâmetros do processo, a saber, diâmetro do reator, tempo de pulsação da irradiação do ultrassom e tempo de pré-condicionamento visando o intumescimento das partículas de beta-quitina, foram variados utilizando um planejamento fatorial fracionário (23-1). Desse planejamento resultou a execução de quatro experimentos e a triplicata do ponto central. A beta-quitina de partida e as quitosanas obtidas foram caracterizadas por espectroscopia de RMN 1H, espectroscopia da região do infravermelho, difração de raios X, viscosimetria capilar, microscopia eletrônica de varredura e termogravimetria. O parâmetro de acetilação (PA) das quitosanas obtidas foi determinado a partir dos espectros de RMN 1H de modo a permitir a avaliação do tipo de distribuição das unidades GlcNAc e GlcN predominante nas cadeias. As quitosanas apresentaram parâmetro de acetilação variando no intervalo 0,61<PA<0,82, indicando o predomínio da distribuição randômica das unidades GlcNAc e GlcN. A determinação da solubilidade das quitosanas foi baseada na turbidez de suas soluções...

Filmes automontados de quitosona/ftalocianinas metálicas:caracterização e aplicação em sensores; Layer-by-layer films of chitosans and phthalocyanines: characterization and use in sensors

Siqueira Junior, Jose Roberto
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 24/04/2006 PT
Relevância na Pesquisa
27.22%
Este trabalho descreve a fabricação de filmes nanoestruturados de quitosana (Q) e metaloftalocianinastetrassulfonadas de níquel (NiTsPc), cobre (CuTsPc) e ferro (FeTsPc) pela técnica de automontagem. A formação dos filmes foi monitorada por espectroscopia na região do UV−vis, focalizando a absorbância da banda Q das metaloftalocianinas. A absorção aumentou linearmente com o número de bicamadas, indicando que a quantidade de metaloftalocianina adsorvida no filme é a mesma a cada bicamada depositada. A espessura média por bicamada variou entre 1,1 e 1,3 nm. Interações específicas nos filmes automontados foram analisadas por espectroscopia FTIR, nos modos de transmissão e reflexão, e Micro−Espectroscopia Raman, evidenciando a formação de interações iônicas entre grupos sulfônicos (SO3− da metaloftalocianina e grupos amina (NH3+) protonados da quitosana. Medidas de voltametria cíclica mostraram que os filmes de QNiTsPc sobre ITO são eletroativos, possuindo um par redox estável, reversível e bem definido em 0,80 V e 0,75 V, respectivamente. A corrente de pico anódica aumentou linearmente com a velocidade de varredura, indicando que a reação eletroquímica é controlada por um mecanismo de transferência de carga na superfície do eletrodo via saltos de elétrons (electronhopping). Entretanto...

Physicochemical characterization of nanoparticles formed between DNA and phosphorylcholine substituted chitosans

Case, Ana Helena; Dalla Picola, Isadora Pfeifer; Darbello Zaniquelli, Maria Elisabete; Fernandes, Julio Cesar; Taboga, Sebastiao Roberto; Winnik, Francoise M.; Tiera, Marcio Jose
Fonte: Academic Press Inc. Elsevier B.V. Publicador: Academic Press Inc. Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 125-133
ENG
Relevância na Pesquisa
27.54%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Processo FAPESP: 07/00339-7; The interactions between phosphorylcholine-substituted chitosans (PC-CH) and calf-thymus DNA (ct-DNA) were investigated focusing on the effects of the charge ratio, the pH, and phosphorylcholine content on the size and stability of the complexes using the ethidium bromide fluorescence assay, gel electrophoresis, dynamic light scattering. and fluorescence microscopy. The size and colloidal stability of deacetylated chitosan (CH/DNA) and PC-CH/DNA complexes were strongly dependent on phosphorylcholine content, charge ratios, and pH. The interaction strengths were evaluated from ethidium bromide fluorescence, and at N/P ratios higher than 5.0, no DNA release was observed in any synthesized PC-CH/DNA polyplexes by gel electrophoresis. The PC-CH/DNA polyplexes exhibited a higher resistance to aggregation compared to deacetylated chitosan (CH) at neutral pH. At low pH values highly charged chitosan and its phosphorylcholine derivatives had strong binding affinity with DNA, whereas at higher pH Values CH formed large aggregates and only C-CH derivatives were able to form small nanoparticles with hydrodynamic radii varying from 100 to 150 nm. Nanoparticles synthesized at low ionic strength with PC-CH derivatives containing moderate degrees of substitution (DS = 20% and 40%) remained stable for weeks. Photomicroscopies also confirmed that rhodamine-labeled PC(40)CH derivative nanoparticles presented higher colloidal stability than those synthesized using deacetylated chitosan. Accordingly...

Synthesis and characterization of phosphorylcholine-substituted chitosans soluble in physiological pH conditions

Tiera, Marcio J.; Qiu, Xing-Ping; Bechaouch, Sofiane; Shi, Qin; Fernandes, Julio C.; Winnik, Francoise M.
Fonte: Amer Chemical Soc Publicador: Amer Chemical Soc
Tipo: Artigo de Revista Científica Formato: 3151-3156
ENG
Relevância na Pesquisa
27.22%
A polymer analogous synthesis involving the reductive amination of phosphorylcholine (PC)-glyceraldehyde with primary amines of deacetylated chitosan (M-w approximate to 57000 g mol(-1)) was used to prepare phosphorylcholine-substituted chitosans (PC-CH) with a degree of substitution (DS) ranging from similar to 11 to similar to 53 mol% PC-substituted glucosamine residues. The PC-CH derivatives were characterized by H-1 NMR spectroscopy, FTIR spectroscopy, and multiangle laser light scattering gel permeation chromatography (MALLS-GPC). The pKa of the PC-substituted amine groups (pKa approximate to 7.20) was determined by H-1 NMR titration. The PC-CH samples (1.0 g L-1) were shown to be nontoxic using an MTT assay performed with human KB cells. Aqueous solutions of PC-CH samples (4.0 g L-(1)) of DS g 22 mol% PC-substituted glucosamine residues remained clear, independently of pH (4.0 < pH < 11.0). The remarkable water solubility and nontoxicity displayed by the new PC-CH samples open up new opportunities in the design of chitosan-based biomaterials and nanoparticles.

Synthesis, characterization and antifungal activity of quaternary derivatives of chitosan on Aspergillus flavus

de Oliveira Pedro, Rafael; Takaki, Mirelle; Gorayeb, Teresa Cristina Castilho; Bianchi, Vanildo Luiz Del; Thomeo, João Cláudio; Tiera, Marcio José; de Oliveira Tiera, Vera Aparecida
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 50-55
ENG
Relevância na Pesquisa
27.22%
Two series of new chitosan derivatives were synthesized by reaction of deacetylated chitosan (CH) with propyl (CH-Propyl) and pentyl (CH-Pentyl) trimethylammonium bromides to obtain derivatives with increasing degrees of substitution (DS). The derivatives were characterized by 1H NMR and potentiometric titration techniques and their antifungal activities on the mycelial growth of Aspergillus flavus were investigated in vitro. The antifungal activities increase with DS and the more substituted derivatives of both series, CH-Propyl and CH-Pentyl, exhibited antifungal activities respectively three and six times higher than those obtained with commercial and deacetylated chitosan. The minimum inhibitory concentrations (MIC) were evaluated at 24, 48 and 72h by varying the polymer concentration from 0.5 to 16g/L and the results showed that the quaternary derivatives inhibited the fungus growth at polymer concentrations four times lower than that obtained with deacetylated chitosan (CH). The chitosans modified with pentyltrimethylammonium bromide exhibited higher activity and results are discussed taking into account the degree of substitution (DS). © 2012 Elsevier GmbH.

Preparação, modificação quimica e calorimetria do biopolimero quitosana

Oyrton Azevedo de Castro Monteiro Junior
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 01/12/1999 PT
Relevância na Pesquisa
18.09%
As quitosanas C e F foram preparadas a partir do biopolímero natural quitina de casca de camarão. O efeito interativo de Cu com a quitina, com as quitosanas C e F e com a quitosana comercial A, foi estudado via calorimetria. A quitosana F foi modificada quimicamente com o glutaraldeído e com silanos organofuncionalizados. Foi investigada a capacidade de adsorção de Cu e de imobilização de quatro diferentes enzimas pela quitina, quitosana F e quitosanas modificadas. A energia livre de Gibbs das interações quitina-Cu e quitosanas-Cu demonstram que os processos são favoráveis à interação polímero-Cu .As entalpias dessas interações são exotérmicas, sendo que para as interações quitosanas-Cu são bem superiores à interação quitina-Cu.A entropia da interação quitina-Cu demonstra um aumento na desordem do sistema, o contrário foi observado para as entropias das interações quitosanas-Cu. A concentração do glutaraldeído afeta as propriedades fisicas e químicas das quitosanas modificadas com este reagente formador de ligações cruzadas, gerando uma série de produtos QGX (X = 0,0 a 25,0). Estes possuem maior capacidade em adsorver o Cu que a quitosana original, entretanto, menor que a QG0,0. Conforme aumenta a concentração de glutaraldeído diminui a capacidade de adsorção de Cu. Os híbridos obtidos com agentes sililantes apresentam-se no estado de hidrogel. Depois de secos mostram ser amorfos e insolúveis em solventes orgânicos...

Study of the antibacterial effects of chitosans on bacillus cereus (and its spores) by atomic force microscopy imaging and nanoindentation

Fernandes, João C.; Eaton, Peter; Gomes, Ana M.; Pintado, Manuela E.; Malcata, F. Xavier
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2009 ENG
Relevância na Pesquisa
27.54%
Bacillus cereus is a Gram-positive, spore-forming bacterium that is widely distributed in nature. Its intrinsic thermal resistance coupled with the extraordinary resistance against common food preservation techniques makes it one of the most frequent food-poisoning microorganisms causing both intoxications and infections. In order to control B. cereus growth/sporulation, and hence minimize the aforementioned hazards, several antimicrobial compounds have been tested. The aim of this work was to assess by atomic force microscopy (AFM) the relationship between the molecular weight (MW) ofchitosan and its antimicrobial activity upon both vegetative and resistance forms of B. cereus. The use ofAFM imaging studies helped us to understand how chitosans with different MW act differently upon B. cereus. Higher MW chitosans (628 and 100 kDa) surrounded both forms of B. cereus cells by forming a polymer layer-which eventually led to the death of the vegetative form by preventing the uptake of nutrients yet did not affect the spores since these can survive for extended periods without nutrients. Chitooligosaccharides (COS) (<3kDa), on the other hand, provoked more visible damages in the B. cereus vegetative form-most probably due to the penetration of the cells by the COS. The use of COS by itself on B. cereus spores was not enough for the destruction ofa large number of cells...

Antimicrobial effects of chitosans and chitooligosaccharides, upon Staphylococcus aureus and Escherichia coli, in food model systems

Fernandes, João C.; Tavaria, Freni K.; Soares, José C.; Ramos, Óscar S.; Monteiro, M. João; Pintado, Manuela E.; Malcata, F. Xavier
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2008 ENG
Relevância na Pesquisa
27.87%
The objective of this study was to elucidate the controversial relationship between the molecular weight (MW) of chitosans and their antibacterial activity (upon different inoculum levels, at several concentrations). The influence of food components on the activity was also ascertained, as well as acceptance by a sensory panel. All the compounds tested exhibited antibacterial activity against Staphylococcus aureus and Escherichia coli. This activity was shown to be closely dependent on the inoculum level, MW and concentration used. Within 4 h at 10³ cells/mL, all five compounds, at every concentration (0.5%, 0.25% and 0.1%, w/v), proved to be bactericidal; for higher inocula, 0.1% (w/v) was only bacteriostatic; at 107 or 105 cells/mL, and independently of the inoculum level, 0.25% (w/v) of any chitooligosaccharide (COS) mixture was sufficient to reduce the E. coli initial population by at least 3 log cycles; COS never exhibited bactericidal action over S. aureus, unlike high and medium MW chitosans—which, at 0.5% (w/v), presented a bactericidal effect even against 107 cells/mL. When incorporated in liquid food matrices, medium and high MW chitosans maintained their activity, for both matrices and bacteria, although a slower activity was noticeable in milk; however...

Atomic force microscopy study of the antibacterial effects of chitosans on Escherichia coli and Staphylococcus aureus

Eaton, Peter; Fernandes, João C.; Pereira, Eulália; Pintado, Manuela E.; Malcata, F. Xavier
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2008 ENG
Relevância na Pesquisa
27.22%
Chitosan has been reported to be a non-toxic, biodegradable antibacterial agent. The aim of this work was to elucidate the relationship between the molecular weight of chitosan and its antimicrobial activity upon two model microorganisms, one Gram-positive (Staphylococcus aureus) and one Gramnegative (Escherichia coli). Atomic force microscopy (AFM) imaging was used to obtain high-resolution images of the effect of chitosans on the bacterial morphology. The AFM measurements were correlated with viable cell numbers, which show that the two species reacted differently to the high- and lowmolecular-weight chitosan derivatives. The images obtained revealed not only the antibacterial effects, but also the response strategies used by the bacteria; cell wall collapse and morphological changes reflected cell death, whereas clustering of bacteria appeared to be associated with cell survival. In addition, nanoindentation experiments with the AFM revealed mechanical changes in the bacterial cell wall induced by the treatment. The nanoindentation results suggested that despite little modification observed in the Gram-positive bacteria in morphological studies, cell wall damage had indeed occurred, since cell wall stiffness was reduced after chitooligosaccharide treatment.

Thermorheological complex behaviour of maltosyl-chitosan derivatives in aqueous solution

Lopes da Silva, J.A.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
27.22%
N-maltosyl-chitosans with different substitution degrees were prepared by reductive N-alkylation. Dynamic shear experiments were used to study the influence of degree of substitution (DS), polymer concentration and temperature on the viscoelastic properties of these semi-synthetic polysaccharides. The attachment of the disaccharide as side chains drastically changed solubility and rheological behaviour of the ‘native’ biopolymer. At lower DS extensive interchain associations may develop, yet allowing for water solubility, but originating temporary gel-like networks. At higher DS, the bulky of the disaccharide groups leads to less extensive hydrogen bonding or hydrophobic interactions and the viscoelastic profile resembles more to an entangled high-molecular weight polymer. The combined effect of different types of interactions among the polysaccharide chains, including topological entanglements, but also more specific hydrogen bonding and hydrophobic interactions, is responsible for several peculiar rheological characteristics, such as strain-induced structuring, complex relaxation processes, elastic plateaus at low frequencies, anomalous scaling behaviour on concentration regarding the relaxation times and modulus, and complex temperature effects...

Growth rate inhibition of phytopathogenic fungi by characterized chitosans

Oliveira Junior,Enio N.; Gueddari,Nour E. El; Moerschbacher,Bruno. M.; Franco,Telma T.
Fonte: Sociedade Brasileira de Microbiologia Publicador: Sociedade Brasileira de Microbiologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 EN
Relevância na Pesquisa
27.87%
The inhibitory effects of fifteen chitosans with different degrees of polymerization (DP) and different degrees of acetylation (F A) on the growth rates (GR) of four phytopathogenic fungi (Alternaria alternata, Botrytis cinerea, Penicillium expansum, and Rhizopus stolonifer) were examined using a 96-well microtiter plate and a microplate reader. The minimum inhibitory concentrations (MICs) of the chitosans ranged from 100 µg × mL-1 to 1,000 µg × mL-1 depending on the fungus tested and the DP and F A of the chitosan. The antifungal activity of the chitosans increased with decreasing F A. Chitosans with low F A and high DP showed the highest inhibitory activity against all four fungi. P. expansum and B. cinerea were relatively less susceptible while A. alternata and R. stolonifer were relatively more sensitive to the chitosan polymers. Scanning electron microscopy of fungi grown on culture media amended with chitosan revealed morphological changes.

Comparison of the Ability of Partially N-Acetylated Chitosans and Chitooligosaccharides to Elicit Resistance Reactions in Wheat Leaves1

Vander, Peter; Vårum, Kjell M.; Domard, Alain; Eddine El Gueddari, Nour; Moerschbacher, Bruno M.
Fonte: American Society of Plant Physiologists Publicador: American Society of Plant Physiologists
Tipo: Artigo de Revista Científica
Publicado em /12/1998 EN
Relevância na Pesquisa
27.87%
Chitin, a linear polysaccharide composed of (1→4)-linked 2-acetamido-2-deoxy-β-d-glucopyranose (GlcNAc) residues, and chitosan, the fully or partially N-acetylated, water-soluble derivative of chitin composed of (1→4)-linked GlcNAc and 2-amino-2-deoxy-β-d-glucopyranose (GlcN), have been proposed as elicitors of defense reactions in higher plants. We tested and compared the ability of purified (1→4)-linked oligomers of GlcNAc (tetramer to decamer) and of GlcN (pentamer and heptamer) and partially N-acetylated chitosans with degrees of acetylation (DA) of 1%, 15%, 35%, 49%, and 60% and average degrees of polymerization between 540 and 1100 to elicit phenylalanine ammonia-lyase (PAL) and peroxidase (POD) activities, lignin deposition, and microscopically and macroscopically visible necroses when injected into the intercellular spaces of healthy, nonwounded wheat (Triticum aestivum L.) leaves. Purified oligomers of (1→4)-linked GlcN were not active as elicitors, whereas purified oligomers of (1→4)-linked GlcNAc with a degree of polymerization ≥ 7 strongly elicited POD activities but not PAL activities. Partially N-acetylated, polymeric chitosans elicited both PAL and POD activities, and maximum elicitation was observed with chitosans of intermediate DAs. All chitosans but not the chitin oligomers induced the deposition of lignin...

Comparison of Proteinase Inhibitor-Inducing Activities and Phytoalexin Elicitor Activities of a Pure Fungal Endopolygalacturonase, Pectic Fragments, and Chitosans 1

Walker-Simmons, Mary; Jin, Donald; West, Charles A.; Hadwiger, Lee; Ryan, Clarence A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/1984 EN
Relevância na Pesquisa
27.22%
Rhizopus stolonifer endopolygalacturonase, an elicitor of casbene synthetase activity in castor bean seedlings, was found to be a potent elicitor of the phytoalexin pisatin in pea pods and of proteinase Inhibitor I in tomato leaves. The enzyme was an active elicitor or inducer only in its active native state; heat-denatured enzyme was inactive in all three systems. The activities of (a) the tomato pectic polysaccharide proteinase inhibitor-inducing factor, (b) a partially acid hydrolyzed proteinase inhibitor-inducing factor, (c) citrus pectic fragments, and (d) chitosan, were also compared in the three bioassay systems. The four oligosaccharide preparations were active in all three systems, but with different degrees of potency. In tomato leaves and pea pods, chitosans were most active, whereas in castor beans, the citrus pectic fragments were the best elicitors. The data presented support the hypothesis that plant and fungal cell wall fragments are important signals in mobilizing a wide variety of biochemically different types of plant defense responses, and that endopolygalacturonases play a key role in releasing the plant cell wall fragments during pest attacks.

Activity of Chitosans in combination with antibiotics in Pseudomonas aeruginosa

Tin, San; Sakharkar, Kishore R.; Lim, Chu Sing; Sakharkar, Meena K.
Fonte: Ivyspring International Publisher Publicador: Ivyspring International Publisher
Tipo: Artigo de Revista Científica
Publicado em 21/01/2009 EN
Relevância na Pesquisa
27.74%
Chitosan and its derivative water soluble Chitosan oligosaccharide are used in a variety of applications in pharmaceutical preparations. In this study, 2 wild (ATCC 15729 and PAO1) and 2 mutant strains (PT121 and PT149) of P. aeruginosa are investigated for drug-drug interactions in vitro. 10 antimicrobial agents (antibiotics) are combined with different degree of deacetylated Chitosans and Chitosan oligosaccharide. All the chitosans show synergistic activity with sulfamethoxazole, a sulfonamide antimicrobial agent. It is interesting to observe that the MIC value for the MexEF-OprN overexpressing mutant strain of P. aeruginosa is 5 fold higher than the other strains under investigation suggesting a possible role of this efflux pump in Sulfamethoxazole efflux. The findings suggest on the use of chitosans as enhancing agent in combination with antibiotics in pharmaceutical preparations.

Chitins and Chitosans as Immunoadjuvants and Non-Allergenic Drug Carriers

Muzzarelli, Riccardo A. A.
Fonte: Molecular Diversity Preservation International Publicador: Molecular Diversity Preservation International
Tipo: Artigo de Revista Científica
Publicado em 21/02/2010 EN
Relevância na Pesquisa
27.54%
Due to the fact that some individuals are allergic to crustaceans, the presumed relationship between allergy and the presence of chitin in crustaceans has been investigated. In vivo, chitin is part of complex structures with other organic and inorganic compounds: in arthropods chitin is covalently linked to proteins and tanned by quinones, in fungi it is covalently linked to glucans, while in bacteria chitin is diversely combined according to Gram(+/−) classification. On the other hand, isolated, purified chitin is a plain polysaccharide that, at the nano level, presents itself as a highly associated structure, recently refined in terms of regularity, nature of bonds, crystallinity degree and unusual colloidal behavior. Chitins and modified chitins exert a number of beneficial actions, i.e., (i) they stimulate macrophages by interacting with receptors on the macrophage surface that mediate the internalization of chitin particles to be degraded by lysozyme and N-acetyl-β-glucosaminidase (such as Nod-like, Toll-like, lectin, Dectin-1, leukotriene 134 and mannose receptors); (ii) the macrophages produce cytokines and other compounds that confer non-specific host resistance against bacterial and viral infections, and anti-tumor activity; (iii) chitin is a strong Th1 adjuvant that up-regulates Th1 immunity induced by heat-killed Mycobacterium bovis...

Growth rate inhibition of phytopathogenic fungi by characterized chitosans

Oliveira Junior, Enio N.; Gueddari, Nour E. El; Moerschbacher, Bruno. M.; Franco, Telma T.
Fonte: Sociedade Brasileira de Microbiologia Publicador: Sociedade Brasileira de Microbiologia
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.87%
The inhibitory effects of fifteen chitosans with different degrees of polymerization (DP) and different degrees of acetylation (FA) on the growth rates (GR) of four phytopathogenic fungi (Alternaria alternata, Botrytis cinerea, Penicillium expansum, and Rhizopus stolonifer) were examined using a 96-well microtiter plate and a microplate reader. The minimum inhibitory concentrations (MICs) of the chitosans ranged from 100 μg ×mL-1 to 1,000 μg ×mL-1 depending on the fungus tested and the DP and FA of the chitosan. The antifungal activity of the chitosans increased with decreasing FA. Chitosans with low FA and high DP showed the highest inhibitory activity against all four fungi. P. expansum and B. cinerea were relatively less susceptible while A. alternata and R. stolonifer were relatively more sensitive to the chitosan polymers. Scanning electron microscopy of fungi grown on culture media amended with chitosan revealed morphological changes.

Emerging Biomedical Applications of Nano-Chitins and Nano-Chitosans Obtained via Advanced Eco-Friendly Technologies from Marine Resources

Muzzarelli, Riccardo A. A.; El Mehtedi, Mohamad; Mattioli-Belmonte, Monica
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 19/11/2014 EN
Relevância na Pesquisa
27.22%
The present review article is intended to direct attention to the technological advances made in the 2010–2014 quinquennium for the isolation and manufacture of nanofibrillar chitin and chitosan. Otherwise called nanocrystals or whiskers, n-chitin and n-chitosan are obtained either by mechanical chitin disassembly and fibrillation optionally assisted by sonication, or by e-spinning of solutions of polysaccharides often accompanied by poly(ethylene oxide) or poly(caprolactone). The biomedical areas where n-chitin may find applications include hemostasis and wound healing, regeneration of tissues such as joints and bones, cell culture, antimicrobial agents, and dermal protection. The biomedical applications of n-chitosan include epithelial tissue regeneration, bone and dental tissue regeneration, as well as protection against bacteria, fungi and viruses. It has been found that the nano size enhances the performances of chitins and chitosans in all cases considered, with no exceptions. Biotechnological approaches will boost the applications of the said safe, eco-friendly and benign nanomaterials not only in these fields, but also for biosensors and in targeted drug delivery areas.

Effect of the Characters of Chitosans Used and Regeneration Conditions on the Yield and Physicochemical Characteristics of Regenerated Products

Hsu, Chu Hsi; Chen, Szu Kai; Chen, Wei Yu; Tsai, Min Lang; Chen, Rong Huei
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 17/04/2015 EN
Relevância na Pesquisa
27.54%
The objective of this study was to explore the effect of the character of chitosans used, and the regeneration conditions employed on, the yield and physicochemical characteristics of regenerated products. Different concentrations of acetic acid were used to dissolve chitosans of 61.7% and 94.9% degree of deacetylation (DD), and weight-average molecular weight (Mw) of 176 and 97 kDa, respectively; they were then precipitated with an 8 N NaOH solution, followed by washing and neutral and freeze drying to get the regenerated products. Yields of regenerated products and their physicochemical properties, such as ash content, bulk density, Mw, polydispersity index (PDI), DD, and crystallinity were measured. A higher concentration of acetic acid used resulted in a higher yield. The purity of the regenerated product increased significantly, whereas the bulk density and crystallinity decreased significantly after regeneration. The regeneration process showed its merits of narrowing down the PDI of regenerated products. The DD and structure of chitosan was changed insignificantly after the regeneration process.

Immunostimulative Activity of Low Molecular Weight Chitosans in RAW264.7 Macrophages

Wu, Ning; Wen, Zheng-Shun; Xiang, Xing-Wei; Huang, Yan-Na; Gao, Yang; Qu, You-Le
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 30/09/2015 EN
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Chitosan and its derivatives such as low molecular weight chitosans (LMWCs) have been reported to exert many biological activities, such as antioxidant and antitumor effects. However, complex and molecular weight dependent effects of chitosan remain controversial and the mechanisms that mediate these complex effects are still poorly defined. This study was carried out to investigate the immunostimulative effect of different molecular weight chitosan in RAW264.7 macrophages. Our data suggested that two LMWCs (molecular weight of 3 kDa and 50 kDa) both possessed immunostimulative activity, which was dependent on dose and, at the higher doses, also on the molecular weight. LMWCs could significantly enhance the the pinocytic activity, and induce the production of tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), interferon-γ (IFN-γ), nitric oxide (NO) and inducible nitric oxide synthase (iNOS) in a molecular weight and concentration-dependent manner. LMWCs were further showed to promote the expression of the genes including iNOS, TNF-α. Taken together, our findings suggested that LMWCs elicited significantly immunomodulatory response through up-regulating mRNA expression of proinflammatory cytokines and activated RAW264.7 macrophage in a molecular weight- and concentration-dependent manner.