Mechanochemical studies of enzymatic degradation of insoluble collagen fibers.

A mechanochemical method was developed for studying the enzymatic degradation of insoluble collagen fibers. The method involves stretching the collagen fiber to a fixed extension in the presence of a solution of collagenase and measuring the rate of relaxation of the force induced in the fiber. In this work, bacterial collagenase was used for reasons of availability. We observed invariably an exponential decrease in force with respect to ttime. The slope of the linear plot of logarithm of the force versus time was taken as a measure of the rate of enzymatic degradation. This rate was found a) to vary linearly with collagenase concentration; b) to be maximal at pH 7-8; c) to vary with temperature according to the Arrhenius relationship in the range 10-56 degrees C; d) to be reduced to varying extent by addition of EDTA omicron-phenanthroline, 2,3-dimercaptopropanolol, and D,L-cysteine; e) to be minimal when the strain on the fiber was ca. 4%; f) to be increased dramatically by denaturation of the collagen fiber; and g) to be reduced by an increase in the crosslink density of the collagen fiber. Except for the effect of strain, which can not be conveniently studied by existing methods these results are consistent with those observed by other methods for the study of the enzymatic degradation of collagen. The mechanochemical method is, however, uniquely suited to monitor continuously the enzymatically induced decay in the stress-bearing ability of collagen fibers. It has also been found useful in the design of collagenous implants with specified resistance to enzymatic degradation in vivo.