Development of the chitosan tube prepared from crab tendon for nerve regeneration

Crystalline chitosan was successfully prepared from crab tendons with aligned chitin molecules. Chitosan obtained preserved the tube structure with a suitable size for nerve conduits (t-chitosan tube). The chitosan tubes were compounded with hydroxy apatite (HAp) using an alternate soaking method (t-chitosan/HAp tube) to enhance the strength of the tube walls. HAp crystals formed in the walls of the chitosan tubes, and their c-axis aligned well in parallel with the chitosan molecules. The growth of the HAp crystals was found to occur at the nucleation sites, most probably by forming complexes with amino groups on chitosan mediated by Ca ions. Furthermore, these tubes were treated at 120 °C to prevent from swelling. These treatments preserved well the hollow nature of the tubes. And the mechanical test showed that the force was significantly higher in the t-chitosan/HAp tube when compared to the circular or triangular t-chitosan tube at each strain.Bridge grafting (15 mm) into the sciatic nerve of SD rats was carried out using the t-chitosan tubes having either a circular or triangular cross-section as well as t-chitosan/HAp tubes (N=18 in each group). Specimens were taken after two, four, six and eight weeks for histology (N=3 in each group). And nerve regeneration was evaluated histologically after 12 weeks (N=6 in each group). The t-chitosan/HAp tubes, demonstrated preferable biodegradation and biocompatibility. In addition to the mechanical properties of the tubes, the results of histological findings suggest that a triangular shape of the tube's cross-section and HAp coating may benefit nerve regeneration.