In vitro biodegradation kinetics of chitosan-based tubes in saliva at 37°C.
Chitosan is degraded by enzymatic hydrolysis and selectively catalyzed by lysozymes into soluble oligomers and further into glucosamine metabolites. Lyzozyme (EC 22.214.171.124) catalyzes hydrolysis of 1.4-beta-linkages between N-acetyl-D-glucosamine residues. Lysozyme is abundant in a number of secretions, such as tears, saliva, human milk and mucus. It is also present in blood, cytoplasmic granules of the polymorphonuclear neutrophils (PMNs).
The degradation time usually varies between from a few weeks to a few months. This depends on chitosan characteristics, the formulation and the implantation site. In particular, the rule tends to be the higher the DA, the faster the biodegradation rate. Chitosan-based devices can be customized in order to reach the desired biodegradation rate. As an example, the biodegradation kinetics of chitosan-based tubes was followed in human saliva at 37°C. These tubes are part of a two layer prosthesis designed to act as a scaffold for the repair of tubular organs such as the esophagus, which in the case of cancer is to be implanted after the resection of the esophagus, in place of the non-degradable polyethylene tubes. This technology is patented (WO2009/027537, EP2180906, US2011/0035023) and at the 28 day mark, the implant starts to erode and becomes less resistant.