Advanced Materials in Wireless, Implantable Electrical Stimulators that Offer Rapid Rates of Bioresorption for Peripheral Axon Regeneration

Abstract

Injured peripheral nerves typically exhibit unsatisfactory and incomplete functional outcomes, and there are no clinically approved therapies for improving regeneration. Post-operative electrical stimulation (ES) increases axon regrowth, but practical challenges, from the cost of extended operating room time to the risks and pitfalls associated with transcutaneous wire placement, have prevented broad clinical adoption. This study presents a possible solution in the form of advanced bioresorbable materials for a type of thin, flexible, wireless implant that provides precisely controlled ES of the injured nerve for a brief time in the immediate post-operative period. Afterward, rapid, complete, and safe modes of bioresorption naturally and quickly eliminate all of the constituent materials in their entirety, without the need for surgical extraction. The unusually high rate of bioresorption follows from the use of a unique, bilayer enclosure that combines two distinct formulations of a biocompatible form of polyanhydride as an encapsulating structure, to accelerate the resorption of active components and confine fragments until complete resorption. Results from mouse models of tibial nerve transection with re-anastomosis indicate that this system offers levels of performance and efficacy that match those of conventional wired stimulators, but without the need to extend the operative period or to extract the device hardware.