Degradation of a collagen-chondroitin-6-sulfate matrix by collagenase and by chondroitinase.

Highly porous, type I collagen-chondroitin-6-sulfate (collagen-GAG) scaffolds, produced by freeze-drying techniques, have proven to be of value as implants to facilitate the regeneration of certain tissues. The objective of this project was to evaluate changes in the microstructure and mechanical properties of selected collagen-GAG scaffolds as they degrade in an in vitro model system. Environmental scanning electron microscopy and video imaging demonstrated that collagenase degradation caused strut erosion through the creation of 1-3 microm diameter micropits within a 2-h period, leading to eventual removal of strut material and strut breakage. Loss of microstructural topography may have been due to gelatinization when collagen was cleaved by collagenase. Chondroitinase degradation of GAG resulted in swelling of the struts, causing the pores to become smaller and rounder. The compressive modulus of the collagen-GAG matrix decreased when degraded by collagenase, but remained unchanged when degraded by chondroitinase. Carbodiimide-cross-linked matrices were found to have a higher cross-link density, a higher compressive stiffness and a greater resistance to collagenase and chondroitinase, compared to non-cross-linked controls and matrices that were cross-linked by the dehydrothermal process. This investigation provides information that can be used to design collagen-GAG scaffolds with desired compressive stiffness and degradation rate to collagenase and chondroitinase.