Preparation of carboxylic graphene oxide-composited polypyrrole conduits and their effect on sciatic nerve repair under electrical stimulation.

Carboxylic graphene oxide-composited polypyrrole/poly-l-lactic acid (C-GO/PPy/PLLA) films were fabricated by electrochemical deposition of C-GO-composited PPy on PLLA fibers-film, and their conductivity and tensile strength (∼4.6 S/cm and 26.4 MPa, respectively) were stably remained after the immersion of 4 weeks, due to the hydrogen bond interaction between graphene oxide's carboxylic groups and pyrrole's imino groups. Their specific surface areas of ∼57.5 m /g and pore volume of ∼0.02 cm /g were significantly larger than those of PPy/PLLA films, due to the addition of C-GO nanosheets. Then, C-GO/PPy/PLLA conducting conduit with 2 mm inner diameter was prepared to bridge 10 mm sciatic nerve defect of rats, and the direction of fiber-axis in the conduit was the same as the conduit central axis. Electrical stimulation (ES) of 1 V and 20 Hz through the conducting conduit was exerted on the defect site. The results of in vivo electrophysiological and histological evaluation indicated that, the sciatic nerve defect could be repaired in C-GO/PPy/PLLA conduit, moreover the re-innervated gastrocnemius muscle and nerve conduction in C-GO/PPy/PLLA conduit & ES group were obviously better than the conduit without ES group. The results of transmission electron microscope analysis also demonstrated that the mean thickness of myelin sheath and diameter of axon in C-GO/PPy/PLLA conduit & ES group were significantly larger than those without ES, suggesting that the repair efficiency of ES & conduit group was closer to that of autograft group. These results indicated the great potential of C-GO/PPy/PLLA with the in vivo ES in the application of sciatic nerve repair.