In vivo and in vitro biodegradation of oxychitin–chitosan and oxypullulan–chitosan complexes

Oxychitin–chitosan complexes prepared from crustacean chitin and oxypullulan–chitosan complexes prepared from three different preparations of Aureobasidium pullulans pullulan were contacted with solutions of egg white lysozyme, Carica papaya papain, wheat germ lipase, Clostridium histolyticum collagenase, porcine pancreas α-amylase, barley malt α-amylase, and sweet potato α-amylase at nearly neutral pH values and 25 and 37°C, for at least three days. The reducing capacity of the solutions in contact with the complex, due to oligomer release, was measured with the aid of ferricyanide and expressed as net absorbance vs time. The oxychitin–chitosan complex was degraded by lysozyme, lipase and papain. The other enzymes were ineffective. Histological evidence indicated that the oxychitin–chitosan complex tested as a bone prosthesis coating in an animal model, was biochemically active and biodegradable, therefore capable to promote osteoconduction and greater bone formation at the bone-prosthesis interface, with no adverse effect on mineralization. Pullulans of different origins were susceptible to enzymatic hydrolysis, particularly so with animal amylase, nevertheless the chitosan complexes obtained from the corresponding oxypullulans were not degraded over the three-day observation period.