Introduction: Development of advanced neuroprosthetic systems depend on the creation of implantable microelectrodes capable of selectively interfacing peripheral nerve tissue. Regenerative sieve electrodes have previously demonstrated the ability to achieve a highly stable and selective interface with peripheral nerve tissue yet have largely been unexplored as a platform for functional electrical stimulation of peripheral axons. The present study aimed to examine the use of regenerative sieve electrodes as a chronic platform for selective stimulation of peripheral motor and sensory axons and restoration of sensorimotor function.
Methods: Custom-designed sieve electrodes were fabricated out of polyimide and gold using sacrificial photolithography. (Fig. 1) Sieve electrodes were implanted in the sciatic nerve of male Lewis rats utilizing a dorsolateral gluteal muscle splitting incision. Post-operatively, functional nerve regeneration through implanted devices was assessed via nerve conduction studies. Functional neural interfacing was assessed in situ via evoked muscle force measurement and cortical mapping within the sensory cortex conducted upon electrical stimulation of implanted microelectrodes. Regenerated nerve segments were terminally explanted and fixed for histomorphometric evaluation.
Results: Histological analysis demonstrated that sieve electrode assemblies supported robust axonal regeneration and were well incorporated into peripheral nerve tissue 3 months post-operatively. Retrograde labeling studies demonstrated successful regeneration of both motor and sensory nerve fibers through implanted electrodes. Implanted sieve electrodes demonstrated a threshold of motor activation of ~10uA and recruited regenerated motor units with 99.5% selectivity. Implanted sieve electrodes demonstrated a similar threshold of sensory activation and elicited activation of local field potentials in sensory cortex.
Conclusions: The present study demonstrates that regenerative sieve electrodes offer a suitable platform for chronic functional electrical stimulation of motor and sensory nerve fibers for future neuroprosthetic applications.
Patient Care: The present study highlights the design and use of a novel class of microelectrode capable of improving future neuroprosthetic systems and faciliting new therapeutic devices and strategies for patients suffering from complex neurological injuries and sensorimotor deficits.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Appreciate the need for advanced neuroprosthetic platforms in
the setting of motor and sensory rehabilitation, 2) Discuss the advantages and benefits of regenerative electrodes as a stable, chronic platform for functional nerve stimulation, and 3) Discuss various approaches to interfacing the peripheral nervous system