Design, Implantation, and Biodistribution Study of a Resorbable Epidural Electrode Array Embedding Bioresorbable Polymeric Conductive Ink

Transient electronic devices that dissolve after use without causing inflammatory reactions could open avenues to alternative medical applications. This article describes the development of an innovative device designed for two-month electrophysiological monitoring followed by biodegradation. The bioresorbable electrode array is composed of poly(lactic-co-glycolic acid) (PLGA), molybdenum (Mo), and an innovative poly(3,4-ethylenedioxythiophene) (PEDOT):hyaluronan (HA) conducting polymer. First, we characterized in vitro the device's biocompatibility and lifetime, monitoring the mass loss and the evolution of the electrode's electrochemical properties. Second, the devices were implanted cortically in rats and used to record electrochemical impedance and visual evoked potentials over a period of 205 days. In vitro and in vivo characterizations demonstrated the benefits of using bioresorbable conductive polymer ink for medium-term monitoring of biological signals since the device with ink coating showed a decrease in impedance compared to the electrode without ink coating. The lifetime of the conductive polymer was estimated at 28 days and 45 days, respectively, in vitro and in vivo. According to post-mortem neuroinflammation assessment in cortical tissues, we can claim that the devices remained biocompatible for their implantation lifetime. No measurable traces of Mo were found in either the brain or the liver, even using advanced characterization methods. We can assume that the conductive polymer safely degraded in vivo in less than two months. Such devices could be used in the future either for neural recording to guide the resection of epileptic foci or for electrical stimulation to improve wound healing mechanisms.