Showing papers on "Chitin published in 2009"
TL;DR: In this paper, a review discusses the various attempts reported on solving this problem from the point of view of the chemistry and the structure of these polymers highlighting the drawbacks and advantages of each method and proposes that based on considerations of structure-property relations, it is possible to obtain chitin fibers with improved strength by making use of their nanostructures and/or mesophase properties of chitins.
2,278 citations
TL;DR: Three possible and accepted antimicrobial mechanisms for chitosan are presented and the activity dependence on polymeric molecular weight and degree of acetylation are described.
Abstract: 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.
1,048 citations
TL;DR: A functional characterization of chitin and chitosan regarding some biological properties and some specific applications (drug delivery, tissue engineering, functional food, food preservative, biocatalyst immobilization, wastewater treatment, molecular imprinting and metal nanocomposites) is presented.
Abstract: Chitin and its deacetylated derivative chitosan are natural polymers composed of randomly distributed � -(1-4)- linked D-glucosamine (deacetylated unit) and N-acetyl-D-glucosamine (acetylated unit). Chitin is insoluble in aqueous media while chitosan is soluble in acidic conditions due to the free protonable amino groups present in the D-glucosamine units. Due to their natural origin, both chitin and chitosan can not be defined as a unique chemical structure but as a fam- ily of polymers which present a high variability in their chemical and physical properties. This variability is related not only to the origin of the samples but also to their method of preparation. Chitin and chitosan are used in fields as different as food, biomedicine and agriculture, among others. The success of chitin and chitosan in each of these specific applica- tions is directly related to deep research into their physicochemical properties. In recent years, several reviews covering different aspects of the applications of chitin and chitosan have been published. However, these reviews have not taken into account the key role of the physicochemical properties of chitin and chitosan in their possible applications. The aim of this review is to highlight the relationship between the physicochemical properties of the polymers and their behaviour. A functional characterization of chitin and chitosan regarding some biological properties and some specific applications (drug delivery, tissue engineering, functional food, food preservative, biocatalyst immobilization, wastewater treatment, molecular imprinting and metal nanocomposites) is presented. The molecular mechanism of the biological properties such as biocompatibility, mucoadhesion, permeation enhancing effect, anticholesterolemic, and antimicrobial has been up- dated.
1,015 citations
TL;DR: The introduction of azido functions in chitosan has provided photo-sensitive hydrogels for surgical use as coatings, scaffolds, drug carriers and implants capable to deliver cells and growth factors, which remain unmatched by other polysaccharides.
1,003 citations
TL;DR: In this paper, the authors extracted chitin in the α and the β forms from different marine crustacean from the Arabian Gulf, and the contents of the various exoskeletons have been analyzed and the percent of the inorganic salt (including the various elements present), protein and the chitins was determined.
501 citations
TL;DR: Crab chitosan was prepared by alkaline N -deacetylation of crab chitin for 60, 90 and 120 min and the yields were 30.0-32.2% with that of chitosa C120 being the highest as discussed by the authors.
446 citations
TL;DR: It was confirmed that the nanofibers were extracted from the natural chitin/protein/mineral composites of crab shell in their original state and the N-acetyl group was not removed and the alpha-chitin crystal structure was maintained, as confirmed by elemental analysis data, FT-IR spectra, and X-ray diffraction profiles.
410 citations
TL;DR: Chitin contains size-dependent pathogen-associated molecular patterns that stimulate TLR2, dectin-1, and the mannose receptor, differentially activate NF-κB and spleen tyrosine kinase, and stimulate the production of pro- and anti-inflammatory cytokines.
Abstract: Chitin is a ubiquitous polysaccharide in fungi, insects, and parasites. We hypothesized that chitin is a size-dependent regulator of innate immunity. To test this hypothesis, we characterized the effects of chitins of different sizes on murine bronchoalveolar or peritoneal macrophages. In these studies, large chitin fragments were inert, while both intermediate-sized chitin (40–70 μm) and small chitin (SC; <40 μm, largely 2–10 μm) stimulated TNF elaboration. In contrast, only SC induced IL-10 elaboration. The effects of intermediate-sized chitin were mediated by pathways that involve TLR2, dectin-1, and NF-κB. In contrast, the effects of SC were mediated by TLR2-dependent and -independent, dectin-1-dependent pathways that involved the mannose receptor and spleen tyrosine kinase. Chitin contains size-dependent pathogen-associated molecular patterns that stimulate TLR2, dectin-1, and the mannose receptor, differentially activate NF-κB and spleen tyrosine kinase, and stimulate the production of pro- and anti-inflammatory cytokines.
239 citations
TL;DR: Some novel applications of this biopolymer in different fields are reviewed and it is shown that chitosan is a nontoxic, biodegradable, and biocompatible natural polymer.
Abstract: Chitosan is prepared from chitin, the second most abundant natural polymer in the world. It is primarily composed of glucosamine and N-acetyl glucosamine residues with a 1,4-β-linkage. It can be obtained by deacetylation of chitin, which is produced from shells of crustaceans, insects, and other sources. Chitosan is a nontoxic, biodegradable, and biocompatible natural polymer and can be used in a wide range of applications such as in the areas of biomedicine, membranes, drug delivery systems, hydrogels, water treatment, food packaging, etc. In this paper, some novel applications of this biopolymer in different fields are reviewed.
232 citations
TL;DR: There is a threshold for chitosan concentration able to switch the induction of a cell death programme into necrotic cell death (cytotoxicity) and it must be pointed out that biological activity of chitOSan, besides the plant model, strictly depends on its physicochemical properties.
Abstract: Chitosan, a deacetylated chitin derivative, behaves like a general elicitor, inducing a non-host resistance and priming a systemic acquired immunity. The defence responses elicited by chitosan include rising of cytosolic H* and Ca2+, activation of MAP-kinases, callose apposition, oxidative burst, hypersensitive response (HR), synthesis of abscissic acid (ABA), jasmonate, phytoalexins and pathogenesis related (PR) proteins. Putative receptors for chitosan are a chitosan-binding protein, recently isolated, and possibly the chitin elicitor-binding protein (CEBiP). Nevertheless, it must be pointed out that biological activity of chitosan, besides the plant model, strictly depends on its physicochemical properties (deacetylation degree, molecular weight and viscosity), and that there is a threshold for chitosan concentration able to switch the induction of a cell death programme into necrotic cell death (cytotoxicity).
174 citations
TL;DR: The UV-irradiation induced morphological changes, such as less entangled cellulose fibers, as observed by scanning electron microscopy, prompted to enhance the chitosan incorporation, which was similar to that obtained with a commercial antimicrobial cellulose fiber.
TL;DR: The ability to produce chitin is more widespread and likely plays a more central role in diatom biology than previously considered, and protein domain predictions and differential gene expression patterns provide evidence that chit in synthases have multiple functions within a diatom cell.
Abstract: Chitin is a globally abundant polymer widely distributed throughout eukaryotes that has been well characterized in only a few lineages. Diatoms are members of the eukaryotic lineage of stramenopiles. Of the hundreds of diatom genera, two produce long fibers of chitin that extrude through their cell walls of silica. We identify and describe here genes encoding putative chitin synthases in a variety of additional diatom genera, indicating that the ability to produce chitin is more widespread and likely plays a more central role in diatom biology than previously considered. Diatom chitin synthases fall into four phylogenetic clades. Protein domain predictions and differential gene expression patterns provide evidence that chitin synthases have multiple functions within a diatom cell. Thalassiosira pseudonana possesses six genes encoding three types of chitin synthases. Transcript abundance of the gene encoding one of these chitin synthase types increases when cells resume division after short-term silicic acid starvation and during short-term limitation by silicic acid or iron, two nutrient conditions connected in the environment and known to affect the cell wall. During long-term silicic acid starvation transcript abundance of this gene and one additional chitin synthase gene increased at the same time a chitin-binding lectin localized to the girdle band region of the cell wall. Together, these results suggest that the ability to produce chitin is more widespread in diatoms than previously thought and that a subset of the chitin produced by diatoms is associated with the cell wall.
TL;DR: It is shown that a filigree chitin-based scaffold is an integral component of the I. basta skeleton and can be isolated from the sponge skeletons using an isolation and purification technique based on treatment with alkaline solutions.
TL;DR: TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation was applied to β-chitins, originating from tubeworm and squid pen, to prepare chitin nanofibrils.
TL;DR: Recent findings on the role of chitin and C/CLP in allergic inflammation and tissue remodeling will be highlighted and controversial and unsolved issues in this field of studies will be discussed.
Abstract: Chitin, the second most abundant polysaccharide in nature after cellulose, consist exoskeleton of lower organisms such as fungi, crustaceans and insects except mammals. Recently, several studies evaluated immunologic effects of chitin in vivo and in vitro and revealed new aspects of chitin regulation of innate and adaptive immune responses. It has been shown that exogenous chitin activates macrophages and other innate immune cells and also modulates adaptive type 2 allergic inflammation. These studies further demonstrate that chitin stimulate macrophages by interacting with different cell surface receptors such as macrophage mannose receptor, toll-like receptor 2 (TLR-2), C-type lectin receptor Dectin-1, and leukotriene B4 recepptor (BLT1). On the other hand, a number of chitinase or chitinase-like proteins (C/CLP) are ubiquitously expressed in the airways and intestinal tracts from insects to mammals. In general, these chitinase family proteins confer protective functions to the host against exogenous chitin-containing pathogens. However, substantial body of recent studies also set light on new roles of C/CLP in the development and progression of allergic inflammation and tissue remodeling. In this review, recent findings on the role of chitin and C/CLP in allergic inflammation and tissue remodeling will be highlighted and controversial and unsolved issues in this field of studies will be discussed.
TL;DR: The gene cloning, purification, properties, kinetics, and antifungal activity of chitinase from marine Streptomyces sp.
Abstract: The gene cloning, purification, properties, kinetics, and antifungal activity of chitinase from marine Streptomyces sp. DA11 associated with South China sponge Craniella australiensis were investigated. Alignment analysis of the amino acid sequence deduced from the cloned conserved 451 bp DNA sequence shows the chitinase belongs to ChiC type with 80% similarity to chitinase C precursor from Streptomyces peucetius. Through purification by 80% ammonium sulfate, affinity binding to chitin and diethylaminoethyl-cellulose anion-exchange chromatography, 6.15-fold total purification with a specific activity of 2.95 Umg−1 was achieved. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed a molecular weight of approximately 34 kDa and antifungal activities were observed against Aspergillus niger and Candida albicans. The optimal pH, temperature, and salinity for chitinase activity were 8.0, 50°C, and 45 g‰ psu, respectively, which may contribute to special application of this marine microbe-derived chitinase compared with terrestrial chitinases. The chitinase activity was increased by Mn2+, Cu2+, and Mg2+, while strongly inhibited by Fe2+ and Ba2+. Meanwhile, SDS, ethyleneglycoltetraacetic acid, urea, and ethylenediaminetetraacetic acid were found to have significantly inhibitory effect on chitinase activity. With colloidal chitin as substrates instead of powder chitin, higher Vmax (0.82 mg product/min·mg protein) and lower Km (0.019 mg/ml) values were achieved. The sponge’s microbial symbiont with chitinase activity may contribute to chitin degradation and antifungal defense. To our knowledge, it was the first time to study sponge-associated microbial chitinase.
TL;DR: A dynamic change of composition of cell wall polysaccharides occurs during plant infection in M. grisea, which spatially and functionally masks β‐1,3‐glucan and chitin in the cell wall of infectious hyphae.
Abstract: Oligosaccharides derived from cell wall of fungal pathogens induce host primary immune responses. To understand fungal strategies circumventing the host plant immune responses, cell wall polysaccharide localization was investigated using fluorescent labels during infectious structure differentiation in the rice blast fungus Magnaporthe grisea. alpha-1,3-glucan was labelled only on appressoria developing on plastic surfaces, whereas it was detected on both germ tubes and appressoria on plant surfaces. Chitin, chitosan and beta-1,3-glucan were detected on germ tubes and appressoria regardless of the substrate. Major polysaccharides labelled at accessible surface of infectious hyphae were alpha-1,3-glucan and chitosan, but after enzymatic digestion of alpha-1,3-glucan, beta-1,3-glucan and chitin became detectable. Immunoelectron microscopic analysis showed alpha-1,3-glucan and beta-1,3-glucan intermixed in the cell wall of infectious hyphae; however, alpha-1,3-glucan tended to be distributed farther from the fungal cell membrane. The fungal cell wall became more tolerant to chitinase digestion upon accumulation of alpha-1,3-glucan. Accumulation of alpha-1,3-glucan was dependent on the Mps1 MAP kinase pathway, which was activated by a plant wax derivative, 1,16-hexadecanediol. Taken together, alpha-1,3-glucan spatially and functionally masks beta-1,3-glucan and chitin in the cell wall of infectious hyphae. Thus, a dynamic change of composition of cell wall polysaccharides occurs during plant infection in M. grisea.
TL;DR: The unusual elastomeric behavior of this protein suggests possible utility in biomaterials applications and little structural organization was found by these biophysical methods, suggesting structural order was not induced by the dityrosine crosslinks.
TL;DR: The purpose of this research is not only to produce two kinds of chitin oligosaccharides or N -acetyl chito-oligosACcharides (NA-COSs) with different molecular weights from crab chit in hydrolysis solution but also to determine their effect against oxidative stress in live cells.
TL;DR: The results suggest that chitin/nanosilica composite scaffolds can be useful for bone tissue engineering applications.
TL;DR: In this paper, a mathematical model between degradation conditions (H2O2 level, time and temperature) and the recovery of water-soluble chitosan was constructed using response surface methodology.
Abstract: Crude chitosan was prepared from shrimp shell by HCl, NaOH and ethanol solution successively. Hydrogen peroxide was used to degrade the crude chitosan into water-soluble chitosan. A mathematical model between degradation conditions (H2O2 level, time and temperature) and the recovery of water-soluble chitosan was constructed using response surface methodology. Each factor showed a significant effect on the recovery. The model was confirmed to have a good fitness by analysis of variance. The optimal conditions to obtain the highest recovery of water-soluble chitosan were 5.5% of H2O2 level, 3.5 h of time and 42.8 °C of temperature. The predicted recovery was 93.5%. Through testing the number of colony, both crude and water-soluble chitosan showed good inhibition activities against B. subtilis. By determination of inhibition zone diameter, water-soluble chitosan showed significantly (P Industrial relevance Chitin is the second abundant polymer next to cellulose over the world. Its deacetylated product, chitosan, is an important ingredient in medicine and food. However, the low solubility in water limits the application of chitosan. In this work, the chitosan was degraded by H2O2 to produce water-soluble chitosan. Response surface methodology was taken to construct a model between degradation conditions and the recovery of water-soluble chitosan. By determination of the antibacterial activity, water-soluble chitosan showed better antibacterial activity than crude chitosan without degradation treatment. The results indicated the high potential of water-soluble chitosan as an antibacterial agent. This work was helpful for applying this product in industry.
TL;DR: Cross-linking provided dimensional stability in acidic medium and significantly decreased the equilibrium water uptake and incorporation of chitin nanocrystals provided increased permeation selectivity to chitosan in neutral and acidic medium.
TL;DR: The state of art concerning this polysaccharide, as well as one of its most important derivatives known as chitosan, is appraised, which has vast applications in various fields.
Abstract: Chitin is the second-most natural polysaccharide in the world, next to cellulose. The main sources of chitin are two marine crustaceans, shrimp and crab. Our objective is to appraise the state of art concerning this polysaccharide, as well as one of its most important derivatives known as chitosan. Chitosan is soluble in acidic aquous media and has vast applications in various fields. Here we briefly describe the characterization, chemical modification, de-polymerization and applications of chitin and chitosan. This review emphasizes recent papers on high value adding applications of these materials in gene therapy, drug delivery, wastewater treatment, packaging, etc.
TL;DR: The benzoylphenylurea diflubenzuron and lufenuron that are widely used as insect growth regulators are studied for their impact on Drosophila cuticle differentiation for understanding their mode of action on a cellular pathway that is seemingly conserved between vertebrates and invertebrates.
TL;DR: Reexamination of the previously used procedure revealed that the β(1-3)glucanase preparation used (zymolyase) is contaminated with a small amount of endochitinase, which caused erroneous results with the double mutant.
Abstract: Previous work, using solubilization of yeast cell walls by carboxymethylation, before or after digestion with beta(1-3)- or beta(1-6)glucanase, followed by size chromatography, showed that the transglycosylases Crh1p and Crh2p/Utr2p were redundantly required for the attachment of chitin to beta(1-6)glucan. With this technique, crh1Delta crh2Delta mutants still appeared to contain a substantial percentage of chitin linked to beta(1-3)glucan. Two novel procedures have now been developed for the analysis of polysaccharide cross-links in the cell wall. One is based on the affinity of curdlan, a beta(1-3)glucan, for beta(1-3)glucan chains in carboxymethylated cell walls. The other consists of in situ deacetylation of cell wall chitin, generating chitosan, which can be extracted with acetic acid, either directly (free chitosan) or after digestion with different glucanases (bound chitosan). Both methodologies indicated that all of the chitin in crh1Delta crh2Delta strains is free. Reexamination of the previously used procedure revealed that the beta(1-3)glucanase preparation used (zymolyase) is contaminated with a small amount of endochitinase, which caused erroneous results with the double mutant. After removing the chitinase from the zymolyase, all three procedures gave coincident results. Therefore, Crh1p and Crh2p catalyze the transfer of chitin to both beta(1-3)- and beta(1-6)glucan, and the biosynthetic mechanism for all chitin cross-links in the cell wall has been established.
TL;DR: Functional analysis showed a high-affinity and calcium-dependent binding of acetylated components to the fibrinogen domain, and a function in endocytosis was demonstrated, suggesting FIBCD1 may play an important role in controlling the exposure of intestine to chitin and chit in fragments.
Abstract: Chitin is a highly acetylated compound and the second most abundant biopolymer in the world next to cellulose. Vertebrates are exposed to chitin both through food ingestion and when infected with parasites, and fungi and chitin modulate the immune response in different directions. We have identified a novel homotetrameric 55-kDa type II transmembrane protein encoded by the FIBCD1 gene and highly expressed in the gastrointestinal tract. The ectodomain of FIBCD1 is characterized by a coiled-coil region, a polycationic region and C-terminal fibrinogen-related domain that by disulfide linkage assembles the protein into tetramers. Functional analysis showed a high-affinity and calcium-dependent binding of acetylated components to the fibrinogen domain, and a function in endocytosis was demonstrated. Screening for ligands revealed that the FIBCD1 is a high-affinity receptor for chitin and chitin fragments. FIBCD1 may play an important role in controlling the exposure of intestine to chitin and chitin fragments, which is of great relevance for the immune defense against parasites and fungi and for immune response modulation.
TL;DR: In this paper, a chitin-based polyurethane elastomers (PUEs) were synthesized by step growth polymerization techniques using poly (e-caprolactone) (PCL), 4, 4′- diphenylmethane diisocyanate (MDI) and blends of chitIN and 1,4-butane diol (BDO).
TL;DR: A chitosan nanoscaffold in the form of a colloidal solution was obtained from the deacetylation of chitin whiskers under alkaline conditions by using a microwave technique in only 1/7 of the treatment time of the conventional method.
TL;DR: Results indicated that the chitin membranes could be used for tissue-engineering applications and were bioactive, and confirmed the formation of calcium phosphate layer on the surface of the both chitIn membranes.
TL;DR: It was revealed that starch and yeast extract served as good carbon and nitrogen sources to enhance chitinase yield and an optimum concentration of colloidal chitInase production was determined.