The Research Of Wound Dressing For Artificial Skin

Collagen which is mainly structural protein in human beings and vertebrates isthe fundamental component in sustainable and connective tissue. It plays manyimportant physiological roles, and theirs medical products possesses manydistinctive merits. However, in order to be widely used, purified collagen needschemical modification, such as cross-linking and esterification, to improve itschemical and biomechanical properties. This study aims at exploring theregularity of collagen preparation and modification, as well as providingexperimental support for the future study of cross-linking and esterification ofcollagen.The natural collagen from tendon dose not meet the demand of application,such as denaturation temperature, mechanic intensity and anti-digest etc, so weshould modify the collagen material. The methods of cross-linking are mainlyphysical method and chemical method and the chemical method is primary way.While attempting to find a suitable crosslinking reagent for biopolymers, anaturally occurring proanthocya-nidin (PA) obtained from grape seeds wasselected to fix biological tissues. The cytotoxicity and crosslinking rate,reflectedby the in vitro and in vivo degradation of fixed matrices has been studied.Firstly we research the reagent conditions. Because the peculiarity ofanti-digest is the mainly deficiency of the collagen, we select anti-digest as thestandard to find out the fundamental parameter of cross-linking, such astemperature, pH and concentration of cross-linking reagents.We found that thebest reagent conditions ofproanthocya-nidin (PA) is 0.5%proanthocyanidin 40%ethanol PBS solution (pH 7.4). A cytotoxicity assay using fibroblast cultures revealed that PA is 120 times lesstoxic than glutaraldehyde (GA), a currently used tissue stabilizer. In vitrodegradation studies showed that fixed tissue was resistant to digestion by bacterialcollagenase. Crosslinks between PA and tissues can be stabilized by decreasingthe dielectric constant of the solution during storage.After subcutaneous implantation for periods ranging between 3 and 6 weeks,we found no apparent degradation of the GA-or PA-fixed tissues, whereas freshtissue controls rapidly disintegrated. Beyond 6 weeks PA crosslinks began todegrade. More fibroblasts migrated and proliferated inside the PA-fixed implantscompared with GA counterparts. Tissues crosslinked with PA manifested anenhanced collagen expression and deposition and did not calcify afterimplantation. GA, on the other hand, even after thorough rinsing continued to becytotoxic, inhibited collagen synthesis and encouraged dystrophic calcification.Collagen matrices crosslinked with PA are expected to be of value in the design ofmatrices that will encourage cell ingrowth and proliferation, which are temporaryin nature,and that are intended to regenerate or replace missing tissues, which candelay the biogradation of collagen. As such they should be of significant value inthe emerging field of tissue engineering.