Preparation And Capabilities Of Composite Asymmetric Chitosan/Carboxymethyl-chitosan Membrane

Chitosan(CS) , as a bio-copolymer comprising glucosamine and N-acetylglucosamine, has perfect antibacterial activity and biocompatibility. Chitosan has been examined to be used in a wide variety of biomedical application, such as drug delivery carriers, surgical thread, bone healing materials, especially wound dressing. As an amphoteric and water-soluble chitosan derivative, carboxymethyl chitosan (CM-CS ) contains carboxylic acid (-COOH) groups and amido(-NH₂) in the molecule. And CM-CS membrane is better than chitosan membrane on histological affinity. In this article, a novel design for a composite asymmetric C-P-C membrane was prepared by casting method with CS, CM-CS and polyvinyl alcohol (PVA) and evaluated as artificial skin iatro-material. Physicochemical properties and permeable property of the composite asymmetric membrane were investigated. Besides, the antimicroorganism and histological examinations of the wound healing towards the asymmetric chitosan membranes were also investigated.The top-layer and sub-layer of the CS/PVA/CM-CS (C-P-C) membrane were smooth and homogeneous. The skin surface of the asymmetric C-P-C membrane was thin and dense but the CM-CS layer was more porous than CS layer. The light transmission rate (LTR) of homogeneous membranes was higher than C-P-C membranes and that of CS membrane which could reach above 90% was higher than PVA and CM-CS. LTR of C-P-C-2 membrane was the highest among the C-P-C membranes. The higher water sorption ability of the C-P-C membranes would be attributed to the increased PVA. This result reveals that the more PVA could have potential to prevent wound from accumulation of fluid by the adsorption of exudate. It was recommended that a rate of 2500 g/ m2 per day, which being in the mid-range of loss rates from injures skin, would provide an adequate level of moisture without risking wound dehydration. The water vapor transmission rate (WVTR) of the asymmetric membranes are ranged from 1876 to 2685 g/ m² per day and that of homogenous membranes are ranged from 1931 to 3128 g/ m² per day depending on the thickness of membrane especially that of PVA layer. Nevertheless, the dependence ofwater vapor flux upon the increased thickness of membrane is less evident. The experiment reveals that C-P-C-l and C-P-C-2 membranes could have potential to provide controlled water evaporation and to promote exudate drainage, which can fit the basic requirements for a membrane to be used as a wound dressing. CS and CM-CS which are proved to possess good antibacterial ability inhibit the growth of Escherichia coli strain, Staphylococcus aureus strain and Candida albicans. C-P-C membranes achieve a local antimicrobial effect against Escherichia coli strain, Staphylococcus aureus strain and Candida albicans.In the animal experiment, in early period after the insertion of the membrane, the tissue implanted with the C-P-C membranes had the more distinct inflammatory reaction than surgical suture group. And the processes reduced with the membrane degraduation. At 6th week postoperatively, the inflammatory cells surrounding the tissues implanted with C-P-C-l and C-P-C-2 membranes had almost disappeared. However, there were still inflammatory cells present in the tissue implanted with the surgical suture and the degree in inflammatory reaction for the tissue implanted with C-P-C-3 membrane was less than that in surgical suture. The C-P-C membrane has desirable histocompatibility.This research shows that the C-P-C membrane comprising CS, CM-CS and PVA layers fits the concept of triple-layer artificial skin (Coenen) not only in the structure but also functions. And it provides the evidence to fabricate ideal artificial skin.