Degradation of collagen suture in vitro and in vivo

In vitro and in vivo degradation of collagen suture was investigated focussing on the change in the mechanical properties and weight. The in vitro hydrolysis was carried out for catguts using collagenase (pH 7.4) and pepsin (pH 1.6), simulating the in vivo environments. The kinetic study on the weight loss of the fibre at the collagenase hydrolysis suggested that the degradation proceeded gradually from the surface of the fibre into the core. The enzymatic hydrolysis was different from the non-enzymatic acidic hydrolysis which resulted in almost homogeneous degradation throughout the cross-section of the fibre from the beginning of the hydrolysis reaction. The rate of weight loss with enzymatic hydrolysis was in good agreement with that predicted under the assumption of continuous erosion from the surface. When the collagen sutures were implanted in the subdermal tissue of rabbits, severe infiltration of macrophages and neutrophils was observed at 4 wk post-implantation, probably because of the degradation products from the implanted sutures. Comparison of the tensile strength decrease with the weight loss observed at the in vivo degradation revealed that enzymatic and non-enzymatic hydrolysis occurred concurrently in the subcutaneous tissue.