EFFECT OF PHYSICAL CROSS-LINKING METHODS ON COLLAGEN-FIBER DURABILITYIN PROTEOLYTIC SOLUTIONS

We previously demonstrated that ultraviolet (UV) or dehydrothermal (DH T) crosslinking partially denatured fibers extruded from an insoluble type I collagen dispersion. In this study denaturation effects were ev aluated by measuring collagen-fiber sensitivity to trypsin. Shrinkage- temperature measurements and sensitivity to collagenase served as indi ces of crosslinking. UV or DHT crosslinking increased the collagen-fib er shrinkage temperature, resistance to degradation in collagenase, an d durability under load in collagenase. However, in trypsin solutions, solubility was significantly increased for UV (approximate to 11%) or DHT (approximate to 15%) crosslinked fibers compared with UV-crosslin ked fibers (approximate to 4%). Size-exclusion chromatography indicate d that no intact collagen alpha-chains were present in the soluble fra ction of fibers exposed to trypsin (MW <1 kD). Interestingly, UV-cross linked collagen fibers remained intact an order of magnitude longer (4 840 +/- 739 min) than DHT-crosslinked (473 +/- 39 min) or uncrosslinke d (108 +/- 53 min) fibers when placed under load in trypsin solutions. These data indicate that mechanical loading during incubation in a tr ypsin solution measures denaturation effects not detected by the tryps in-solubility assay. Our results suggest that DHT-crosslinked collagen fibers should not be used as load-bearing implants. UV-crosslinked fi bers may retain more native structure and should exhibit greater resis tance to nonspecific proteases in vivo. (C) 1996 John Wiley & Sons, In c.