Degradation of nerve guidance channels based on a poly(l-lactic acid) poly(trimethylene carbonate) biomaterial

Poly(l-lactic acid) (PLLA) and in-house synthesized poly(trimethylene carbonate) (PTMC) were used for development of nerve guidance tubes for support of peripheral nervous system regeneration after an injury. Phase separation of a viscous solution of the polymer mixture on a rod in a non-solvent resulted in fabrication of tubular structure of large porosity. After radiation sterilization by electron beam (EB) applied to assure safety of the product, tensile properties and elasticity of manufactured tubes were sufficient for proposed application. Influence of in vitro hydrolytic degradation on molecular weight, thermal properties of the polymers, morphology and mechanical properties of the tubes was evaluated. Besides minor mass loss in the course of 12 months hydrolytic degradation, molecular weight of PLLA component decreased steadily due to hydrolysis of ester bonds. Consequently changes in thermal properties of the polymers such as change in glass transition and melting temperatures were identified. Admixture of methyl cellulose (MC) to PLLA and PTMC synthetic polymers resulted in slight change of mechanical performance of the channels after an initial two weeks of degradation since this water-soluble polymer of natural origin was extracted from the synthetic polymer matrix. Other parameters of the tube and those of synthetic polymers were not affected by the presence of MC. Based on the experimental data, it is confirmed that proposed polymeric material of PLLA/PTMC blend with and without addition of MC is suitable for further biological and in vivo study.