Microwave irradiated collagen tubes as a better matrix for peripheral nerve regeneration

Collagen is one of the best materials used for nerve guide preparation due to its biocompatibility and desirable tensile strength. In this work, we have compared regeneration and functional reinnervation after sciatic nerve resection with bioresorbable crosslinked collagen guides in 10 mm gap. The crosslinking was carried out either with glutaraldehyde (GTA) or microwave irradiation (MWI). The multilayered collagen membrane used for nerve guides are prepared by lamellar evaporation technique. Functional evaluations of the regenerated nerves were performed by measuring the sciatic functional index (SFI), nerve conduction velocity (NCV), and electromyography (EMG). Transmission electron microscopic studies showed growth of axonal cable with fewer myelinated axons, Schwann cells and more unmyelinated axons present in the case of group treated with uncrosslinked collagen tubes after 1 month of implantation. However, we have observed more myelinated axons in the case of autograft, GTA, and MWI crosslinked collagen tube implants across the gap of 1 cm after the same period of implantation. Smaller myelinated fiber diameter was observed in the case of GTA crosslinked collagen tube group when compared with the autograft and MWI collagen tube groups. There were more myelinated axons during the 3rd and 6th months postoperatively using these conduits as substantiated by light microscopic studies of the regenerated nerve. The conduction velocity and recovery index improved significantly after 5 months reaching the normal values in the autograft and MWI crosslinked collagen groups compared to GTA and uncrosslinked collagen tubes.