RECORDING PROPERTIES AND BIOCOMPATIBILITY OF CHRONICALLY IMPLANTED POLYMER-BASED INTRAFASCICULAR ELECTRODES

We implanted polymer-based longitudinal intrafascicular electrodes (po lyLIFEs) in feline dorsal rootlets acutely and for periods of two to s ix months to evaluate their electrical properties and biocompatibility . A total of 38 implanted electrodes were analyzed. Some 25 of the 38 electrodes were implanted with an insulative flexible polymer cuff, wh ich was required for recording of afferent activity in situ. Electrode impedances remained stable for the duration of the experiments. The d istributions of axons were measured at three levels of the implanted r ootlets: the implant level, 1-2 mm proximal to the implant with respec t to the cell body, and 1-2 mm distal to the implant with respect to t he cell body. Similar measurements were made in five samples of fascic les neighboring an implant and six samples of control tissue from anim als in which no implants were placed. The polyLIFEs demonstrated a hig h degree of biocompatibility, as no adverse effects on axon size were observed in either the implanted fascicle or neighboring neural tissue . However, the insulative cuffs were found to be a source of compressi on, resulting in necrosis of the neural tissue. (C) 1998 Biomedical En gineering Society. [S0090-6964(98)01606-3].