CROSS-LINKING OF DERMAL SHEEP COLLAGEN WITH TANNIC-ACID

The purpose of this study was to investigate cross-linking-of (damaged ) collagen by tannic acid, with a view to reconsider its use as a poss ible therapeutical agent in the treatment of burn wounds. Because of c ontradictory reports in the literature, and increased purity of tannic acid, this method has again become valuable for re-evaluation. A labo ratory study using dermal sheep collagen was conducted to analyse the influence of several metal ions on collagen cross-linking with tannic acid. The tannic acid concentration vs degree of cross-linking, tannic acid uptake and release, influence of the addition of metal ions, and the rate of degradation of treated collagen were established. We have shown that tannic acid mediated collagen cross-linking in a concentra tion-dependent manner. Cross-linking was influenced by the presence of metal ions: Fe3+ and Ag+ were shown to exert a stimulatory effect on the degree of cross-linking by a 2% tannic acid solution, whereas Zn2 had an inhibitory effect. Ce3+ Ca2+ and Na+ did not influence the deg ree of cross-linking. The degree of cross-linking was proportional to the uptake of tannic acid, which varied between 6 and 35 wt%. Reversib ility of cross-linking was established. Tannic acid-treated dermal she ep collagen showed a slow degradation rate relative to differently cro ss-linked collagen materials when subjected to collagenase or pancreat ic proteolytic enzymes. The results of this study suggest that tannic acid could have a function in vivo in burn treatment by binding burn t oxins and inhibiting degradation of the (remaining) dermal matrix, and allows combination with metal ions as antimicrobials. Optimal cross-l inking was obtained using a 2 wt% tannic acid solution; combination wi th Ce3+ as a potential antimicrobial agent is possible without diminis hing cross-linking. (C) 1997 Elsevier Science Limited.