Gellan gum doped polypyrrole neural prosthetic electrode coatings

Abstract

Surface modification of neural prosthetic electrodes with polymeric materials, in particular, conducting polymers and hydrogels, has the potential to circumvent many problems associated with currently used electrode platforms. These problems include the disparity in mechanical properties between implanted electrodes and host neural tissue and the lack of biofunctionality at the electrode surface, both of which dissuade favourable reception of the implanted device. We have developed conducting polymer electrode coatings doped with the polysaccharide gellan gum, as a platform for improved functionality of neural prosthetic electrodes. Our electrode coatings, prepared by galvanostatic electropolymerisation, significantly reduced the impedance magnitude at frequencies relevant to neural cells, relative to uncoated gold Mylar electrodes (24 ± 3 Ω at 1 kHz). Cyclic voltammetry was used to explore the electrochemical stability of the coatings, which lose only 23 ± 2% charge carrying capacity when subjected to 400 redox cycles. The coatings show no change in impedance magnitude at 1 kHz when subject to 32 h of clinically relevant charge balanced current stimulation.