Evaluation of collagen cross-linking techniques for the stabilization of tissue matrices

The use of glutaraldehyde (GTA) for cross-linking biological tissue implants has a number of undesirable side effects, including cytotoxicity and induction of calcification. In an attempt to find an improved cross-linking agent for tissue implants, we have evaluated a number of cross-linking procedures shown previously to be effective with pure collagen or collagenous substrates, including GTA, succinic anhydride, cyanamide, 1-ethyl-3-(dimethylaminopropyl)carbodi-imide, dimethyl suberimidate, ascorbate-copper, glucose-lysine and acyl azide treatments. Apart from GTA, only acyl azide treatment significantly cross-linked human dermis, the degree of cross-linking being better than that seen after treatment of dermis with 1 mM GTA. Acyl azide treatment of thicker vascular tissue (porcine aorta) also resulted in a significantly cross-linked tissue. Preliminary cytotoxicity studies suggested that acyl azide treatment was not toxic, and, therefore, coupled with its cross-linking ability, this treatment is worthy of further investigation and may prove to be an alternative to GTA for the treatment of bioprostheses.