Nanoscale surface modification of thin film microelectrodes to improve biocompatibility

The promise of multichannel thin film microelectrodes for closed-loop neural prosthetic control has been hindered by the inability of these electrodes to record for long periods of time. Recently, we have shown that thin film electrodes produced using a ceramic substrate and insulation (CBMSE arrays) can consistently record single neuron action potentials for three months in the rat, which is comparable to microwire electrodes. To enhance their biocompatibility and increase the recording time, we have recently modified the surface of these microelectrodes with nanoscale polymers. We have used electrospinning to coat our CBMSE arrays with nanoscale poly(DL-lactic-co-glycolic acid) (PLAGA) fibers. Coated and uncoated arrays were implanted into the somatosensory barrel field cortex of the rat. Single neuron action potentials recorded from the two electrodes were indistinguishable. After 1 week, the tissue was processed for histological assessment to examine 1) growth of new neural processes, 2) glial activity and 3) cell survival. There was no significant difference between the tissue surrounding the coated and uncoated electrodes. These results suggest that PLAGA nanofibers are biocompatible and do not interfere with signal recording. We are in the process of drug loading these fibers with bioactive molecules to enhance longterm recordings.