Evaluation of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) conduits for peripheral nerve regeneration

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) was investigated for possible application in repairing damaged nerves. Porous nerve conduits with both uniform wall porosity and non-uniform wall porosity were prepared using a particle leaching method. Adult Sprague-Dawley (SD) rats weighing 200-250 g were used as the animal model. The conduits were employed to bridge the 10mm defects in the sciatic nerve of the Sprague-Dawley (SD) rats. Mechanical tests showed that the PHBHHx nerve conduits had proper mechanical properties including maximal loads of 3.1N and 1.3N for the conduits with non-uniform wall porosity and with uniform wall porosity, respectively, and maximal stresses of 2.3 MPa and 0.94 MPa for the conduits with non-uniform wall porosity and with uniform wall porosity, respectively. At the same time, both types of conduits were permeable to three compounds tested including glucose, lysozyme and bovine serum albumin, indicating the suitability of the conduits for free exchanges of nutrients. Compound Muscle Action Potentials (CMAPs) were clearly observed in both types of the PHBHHx nerve conduits after 1 month of implantation, indicating a rapid functional recovery for the disrupted nerves. The results of histological sections demonstrated that the internal sides of the conduits with non-uniform wall porosity were compact enough to prevent the connective tissues from ingrowth penetration. After implantation for 3 months in the rats, the conduits with uniform wall porosity and those with non-uniform wall porosity lost 24% and 20% of their original weight average molecular weights, respectively. Combined with the strong mechanical properties, good nerve regeneration ability and non-toxicity of its degradation products, PHBHHx nerve conduits can be developed into a useful material to repair nerve damage.