Chitin-Methacrylate: Preparation, Characterization and Hydrogel Formation.

Chitin-methacrylate (CM) was prepared by the reaction of methacrylic acid on chitin in 5% LiCl/DMAc in the presence of N,N'-dicyclocarbodiimide and dimethylaminopyridine. The resultant chitin-methacrylate product was isolated in 61% yield and was found to be readily water-soluble. The derivative was found to be a mixture of methacrylate and methacrylic-dimethylaminopyridine complex substituents at the C-6 position in approximately equal amounts.

Complete cDNA sequence of chitin deacetylase from Gongronella butleri and its phylogenetic analysis revealed clusters corresponding to taxonomic classification of fungi.

A cDNA library containing a chitin deacetylase (CDA) gene from a zygomycete Gongronella butleri was constructed and the complete gene was sequenced. The complete gene contains an open reading frame of 1290 nucleotides which encodes a sequence of 430 amino acid residues. The gene sequence consists of nucleotides encoding a polysaccharide deacetylase domain located in the middle, covering 34% of the entire sequence.

Transfection efficiency of chitosan vectors: effect of polymer molecular weight and degree of deacetylation.

Chitosans of defined molecular weight (Mw 10-213 kDa) and degree of deacetylation (DD 46-88%) were synthesized, complexed with pEGFP-C2 plasmid into nanoparticles (NP) and evaluated for cellular uptake and transfection efficiency in the A549 cell model. DNA condensation of >90% was achieved at the N/P ratio of 6, independent of the chitosan Mw and DD. However, chitosan vectors of lower Mw or DD were less efficient at retaining the DNA upon dilution, and consequentially, less capable of protecting the condensed DNA from degradation by DNase and serum components.

Preparation of C-6 substituted chitin derivatives under homogeneous conditions.

Tosylation of chitin under homogeneous conditions was achieved by the reaction of tosyl chloride with chitin in a DMAc/LiCl solvent system. The resultant tosyl-chitin was fully N-acetylated with acetic anhydride in methanol. The fully acetylated tosyl-chitin was subsequently reacted with the sodium salts of ethyl p-hydroxybenzoate, diethyl malonate, and diethyl phosphite in DMAc to give the corresponding chitin derivatives of 6-O-ethyl benzoate-chitin, 6-deoxy-diethyl malonate-chitin, and 6-(deoxydiethyl) phosphite-chitin, respectively.

Flexible chitin films: structural studies.

Chitin gels were transformed into thin, flexible chitin films with minimal dimensional shrinkage and maximum flexibility and thickness in the range of 25-80 microm by a cold-press process. Solvent residue was removed by heating the films at 50 degrees C for 12 h, followed by rinsing in 95% ethanol. The crystallinity and mechanical properties of the flexible chitin films were found to be a function of the amount of shrinkage from the gel to the final film that was obtained.

Uptake and cytotoxicity of chitosan molecules and nanoparticles: effects of molecular weight and degree of deacetylation.

Purpose: To evaluate the effects of molecular weight (Mw) and degree of deacetylation (DD) on the cellular uptake and in vitro cytotoxicity of chitosan molecules and nanoparticles.

Methods: Chemical depolymerization and reacetylation produced chitosans of Mw 213,000 to 10,000 and DD 88-46%, respectively. Chitosan was labeled with FITC and transformed into nanoparticles by ionotropic gelation.

Hydroxyapatite-chitin materials as potential tissue engineered bone substitutes.

Hydroxyapatite (HA) in 25%, 50% and 75% w/w fractions was incorporated into chitin solutions and processed into air- and freeze-dried materials. These HA-chitin materials were exposed to cell cultures and implanted into the intramusculature of a rat model. The HA-chitin materials were found to be non-cytotoxic and degraded in vivo.

Flexible chitin films as potential wound-dressing materials: wound model studies.

Chitin films possessing increased flexibility, softness, transparency, and conformability have been prepared. These attributes enable the potential application of chitin films as occlusive, semipermeable film wound dressings similar to commercial products such as Opsite trade mark. The chitin films are generally nonabsorbent, exhibiting a total weight gain of only up to 120-160% in physiological fluid.

Implantable applications of chitin and chitosan.

Chitin, extracted primarily from shellfish sources, is a unique biopolymer based on the N-acetyl-glucosamine monomer. More than 40 years have lapsed since this biopolymer had aroused the interest of the scientific community around the world for its potential biomedical applications. Chitin, together with its variants, especially its deacetylated counterpart chitosan, has been shown to be useful as a wound dressing material, drug delivery vehicle and increasingly a candidate for tissue engineering.

Uptake of FITC-chitosan nanoparticles by A549 cells.

Purpose: The objective of this study was to evaluate the extent and mechanism of uptake of fluorescent chitosan nanoparticles by the A549 cells, a human cell line derived from the respiratory epithelium.

Methods: Covalent conjugation with fluorescein-5-isothiocyanate yielded stably labeled chitosan molecules, which were successfully formulated into nanoparticles by ionotropic gelation. Uptake of fluorescein-5-isothiocyanate-chitosan nanoparticles and chitosan molecules by confluent A549 cells was quantified by fluorometry.

Chitosan-alginate PEC membrane as a wound dressing: Assessment of incisional wound healing.

Flexible, thin, transparent, novel chitosan-alginate polyelectrolyte complex (PEC) membranes, cast from aqueous suspensions of chitosan-alginate coacervates with CaCl(2), were evaluated as potential wound-dressing materials. MTT and NR assays suggested that the chitosan-alginate PEC membranes and their aqueous extracts were nontoxic towards mouse and human fibroblast cells. Cell growth was also not hindered by co-incubation with the membranes.

Selection of Gongronella butleri strains for enhanced chitosan yield with UV mutagenesis.

This paper describes the selection of Gongronella butleri strains producing higher chitosan yield using UV mutagenesis. We have devised an enzyme-linked immunosorbent assay for the selection of high chitin deacetylase (CDA) yielding strains. Mutant strains M+1, M+2 and M+7 could produce twice the extractable chitosan yield and double the CDA activity, as compared to the wild type strain.