Biocompatibility of a Silicon Based Peripheral Nerve Electrode

The biocompatibility of a silicon neuroelectric interface for chronic use in mammalian peripheral nerves was investigated. New Zealand white rabbits were used as the animal model. The implant was made of (110) silicon coated with one micron of silicon dioxide. An anisotropic etch was used to form a grid of ten silicon bars each 40 microns wide and spaced 160 microns apart. A Silastic nerve cuff was molded onto each side of the grid. Using microsurgical techniques, the nerve was transected and sutured into the implant cuff. One implanted rabbit was completely analyzed and is reported here. By 32 days post operatively, the EMG of the affected muscles had partially recovered. The EMG of the affected muscles was indistinguishable from the contralateral control muscles after 150 days. At 332 days, the conduction properties of the implanted nerve confirmed that the nerve was capable of conduction through the silicon grid. Histological observations were consistent with normal peripheral nerve regeneration following microsurgical neurrorhaphy. Seven additional rabbits have been implanted and will be fully analyzed in the future. It was concluded that the silicon peripheral nerve implant described here should be pursued as a substrate for a chronic neuroelectric interface.