In vitro degradation rates of partially N-acetylated chitosans in human serum.

The initial degradation rates (r) in human serum of three chitosans with FA = 0.42, 0.51, and 0.60 were determined by measuring the decrease in viscosity as a function of time. A strong increase in r with increasing FA of the chitosans was observed, with r increasing proportionally to FA4.5. With increasing concentrations of lysozyme added to the reaction mixtures of chitosan and serum, the relative increase in degradation rate of chitosans with increasing FA was almost the same as that without lysozyme added. Addition of the chitinase inhibitor allosamidin (50 microM) did not inhibit the degradation rate of chitosan (FA = 0.60) by human serum. The results suggest that chitosans are actually mainly depolymerized by lysozyme in human serum, and not by other enzymes or other depolymerization mechanisms.