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In this study, the depolymerization of chitosan was carried out in an acetic acid aqueous solution and was followed by viscometry for molecular weight determination. It was found that the depolymerization rate increased with elevated temperatures and with high acid concentrations. Based on FTIR analysis, the chitosan was depolymerized randomly along the backbone; no other structural change was observed during the acid depolymerization process. Revealed in the TGA study, the degradation temperature and char yield of LMWCs (low molecular weight chitosan) were molecular weight dependent. The blood compatibility of LMWCs was also investigated: rouleaux formation was observed when erythrocyte contacted with LMWCs, which showed that LMWCs are able to interfere with the negatively charged cell membrane through its polycationic properties. Furthermore, as regards a kinetics investigation, the values of M(n) (number-average molecular weight) were obtained from an experimentally determined relationship. The kinetics study showed that the complex salt, formed by amine on chitosan and acetic acid, acted as catalyst. Finally, the activation energy for the hydrolysis of the glycosidic linkage on chitosan was calculated to be 40kJ/mol; the mechanism of acid depolymerization is proposed. In summary, LMWCs could be easily and numerously generated with acid depolymerization for further biological applications., (2010 Elsevier Ltd. All rights reserved.)

In this study, we prepared a polyelectrolyte complex (PEC) hydrogel comprising chitosan as the cationic polyelectrolyte and gamma-poly(glutamic acid) (gamma-PGA) as the anionic polyelectrolyte. Fourier transform infrared spectroscopy revealed that ionic complex interactions existed in the chitosan-gamma-PGA PEC hydrogels. The compressive modulus increased upon increasing the degree of complex formation in the chitosan-gamma-PGA PEC hydrogel; the water uptake decreased upon increasing the degree of complex formation. At the same degree of complex formation, the compressive modulus was larger for the chitosan-dominated PEC hydrogels; the water uptake was larger for the gamma-PGA-dominated ones. Scanning electron microscopy images revealed the existence of interconnected porous structures (pore size: 30-100mum) in all of the chitosan-gamma-PGA PEC hydrogels. The chitosan-gamma-PGA PEC hydrogels also exhibited antibacterial activity against Escherichia coli and Staphylococcus aureus. In addition, in vitro cell culturing of 3T3 fibroblasts revealed that all the chitosan-gamma-PGA PEC hydrogels were effective in promoting cell proliferation, especially the positively charged ones (chitosan-dominated). Therefore, the chitosan-gamma-PGA polyelectrolyte hydrogel appears to have potential as a new material for biomedical applications., (Copyright 2010 Elsevier Ltd. All rights reserved.)

Abstract: This study presents a novel design for an easily stripped polyelectrolyte complex (PEC), which consists of chitosan as a cationic polyelectrolyte and γ-poly (glutamic acid) (γ-PGA) as an anionic polyelectrolyte, as a wound dressing material. The physical and chemical properties of the chitosan/γ-PGA PECs are fully investigated. Experimental results show that the physical and chemical properties and the in vitro degradation of the chitosan/γ-PGA PECs directly reflect the degree of complex formation. In addition, chitosan/γ-PGA PECs provide suitable moisture content and exhibit good mechanical properties, both favorable for allowing dressing to be easily stripped off from the wound surface without damaging newly regenerated tissue. Furthermore, in vivo experiments are conducted on a mouse model to study wounds treated with the chitosan/γ-PGA PECs. Histological examinations reveal that, more than 50% of re-epithelialization and regeneration of the wound are achieved by dressing it with the chitosan/γ-PGA PECs. On the basis of wound-healing efficacy, chitosan/γ-PGA PECs can be potentially applied as a wound dressing material. [Copyright &y& Elsevier]