Function-inspection scheme for an injured peripheral nerve using a polymer based microelectrode array

This paper presents a compound nerve action potential (CNAP) monitoring system of a peripheral nerve which is composed of a sieve-shape flexible microelectrode array (MEA), a polyglycolic acid (PGA) conduit and a bio-potential amplifier. The system observes a regenerated peripheral nerve by measuring its CNAP. An MEA is fabricated through micromachining technology, and its interfacial impedance (420 kΩ/μm2) and signal transfer characteristics were analyzed. The fabricated MEA was assembled with the PGA conduit, and then the assembly had been implanted into a sciatic nerve of a rat. After 12 week-implantation periods, regenerated state of the damaged sciatic nerve was investigated by gait analysis and CNAP measurement. From the gait analysis, sciatic function index (SFI) was calculated to be −48.5 ± 15.0. According to the CNAP measurement, threshold potential was 250 μV in contrast to 110 μV for a normal nerve. After the functional tests, regenerated nerves were harvested and their morphologies were examined through toluidine blue (TB), Hematoxylin and Eosin (H&E) and transmission electron microscope (TEM) images. According to the morphology study, it was confirmed that proximal and distal nerve stump showed similar morphology and axon number.