Biofunctionalized Conducting Polymer/Carbon Microfiber Electrodes for Ultrasensitive Neural Recordings

Carbon microfibers (MFs) coated with conducting polymers may provide a solution for long-term recording of activity from individual or small groups of neurons. Attaching cell adhesion molecules to the electro-sensitive surface might further improve electrode-neuron contact, thus enhancing signal stability and fidelity. We fabricated biofunctionalized microelectrodes consisting of 7-μm diameter carbon MFs coated with poly(3,4-ethylenedioxythiophene) doped with poly[(4-styrenesulfonic acid)-co-(maleic acid)] (

PSS-co-MA), and linked N-Cadherin to the polymer surface. These electrodes were tested for recording artificially generated electric potentials, as well as multiunit activity (MUA), sharp wave-ripple complexes (SWRs), and field excitatory postsynaptic potentials (fEPSPs) in rat hippocampal slices. The effects of electrode length and functionalization were compared.

PSS-co-MA coating improved electric current detection and reduced the electrical noise but had no significant effect on the amplitude of recorded biopotentials. Surface biofunctionalization lowered the electric current flow, and further reduced the electrical noise. Additionally, it increased the amplitude of the recorded MUA, finally doubling the signal-to-noise ratio achieved with bare carbon MFs. Biofunctionalization benefits were apparent only for potentials from cells putatively adjacent to the microelectrode. Analysis of fEPSPs excluded adverse effects of functionalized electrodes in basal synaptic transmission. These results demonstrate the possibility of enhancing the amplitude and signal-to-noise ratio of neural recordings by coating the microelectrodes with conducting polymers modified with neural cell adhesion molecules, and support the use of biofunctionalized MFs in advanced neuroprosthetic devices.