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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This article describes the preparation of porous chitosan, a hydroxyapatite hybrid, by partial enzymatic degradation. Two enzymes, chitosanase and lysozyme, were selected to hydrolyze a chitosan-reinforced matrix and create pores within the chitosan-hydroxyapatite composite. The degree of enzymatic hydrolysis of the chitosan-hydroxyapatite composite was determined by measuring the % weight loss of the chitosan matrix and the hydroxyapatite component. Hydroxyapatite loss from the chitosan matrix increased with the degree of enzymatic hydrolysis of the chitosan-reinforced matrix. After hydrolysis, the composite was further characterized by FTIR. Quantitative analysis revealed a decrease in the characteristic pyranose ring peak (1072 cm(-1)), compared with Po4(2-) (1110 cm(-1)), showing that the chitosan matrices were enzymatically hydrolyzed. The surface of the porous chitosan-hydroxyapatite composite, prepared by controlling enzymatic hydrolysis, was also observed by SEM.
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PMID:Inorganic-organic polymer hybrid scaffold for tissue engineering--II: partial enzymatic degradation of hydroxyapatite-chitosan hybrid. 1246 61

Pepsin (EC 3.4.4.1) from porcine stomach mucosa caused depolymerization of a chitosan sample (a copolymer of glucosamine and N-acetylglucosamine linked by beta-1-4-glycosidic bonds). N-terminal sequence and zymogram analyses confirmed dual (proteolytic and chitosanolytic) activities of pepsin. Optimum depolymerization occurred at pH 5.0 and 45 degrees C with an activity of 4.98 U. Low molecular weight chitosan (LMWC), the major depolymerization product, was obtained in a yield of 75-82%, the degree of polymerization of which depended on reaction time. The LMWC showed a nearly 10-14-fold decrease in the molecular mass as compared to native chitosan, which was also confirmed by GPC and HPLC analyses. IR and 13C NMR spectra indicated a decrease in the degree of acetylation (DA, approximately 13.4-18.8%) as compared to native chitosan (approximately 25.7%), which was in accordance with the CD analysis. Native chitosan had a crystallinity index (CrI) of approximately 70%, whereas there was a decrease in the CrI of LMWC (approximately 61%). The latter showed a better bactericidal activity toward both Bacillus cereus and Escherichia coli, which was more toward the former. The bactericidal activity was essentially due to the lytic and not static effect of LMWC, as evidenced by the pore formation on the bacterial cell surface when observed under SEM. This study suggests the possible use of pepsin in place of chitosanase, which is expensive and unavailable in bulk quantities for the production of LMWC of desired molecular mass that has diversified applications in various fields.
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PMID:Low molecular weight chitosan--preparation with the aid of pepsin, characterization, and its bactericidal activity. 1725 86