Neural electrodes used for in vivo biomedical applications (e.g., prostheses, bionic implants) result in glial invasion, leading to the formation of a nonexcitable scar that increases the distance between neurons and electrode and increases the resistance to current flow. The result is progressive deterioration in the performance of stimulation or recording of neural activity and inevitable device failure. Also, electrodes with a 2D surface have a limited proximity to neurons. In the present study, a macroporous and fibrous 3D neural electrode is developed using poly-L-lactic acid fibrous membranes imbued with electroactive properties via a coating of the conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT), using vapor phase polymerization. The electrical properties of the PEDOT-coated substrates are studied using sheet resistance and impedance. PEDOT electrode biocompatibility is assessed through in vitro assays using patch-clamp electrophysiology and calcium imaging of isolated and cultured rat hippocampal neurons. PEDOT fibers support robust normal functional development of neurons, including synaptic networking and communication. Stimulation and recording of activity in brain slices and from the surface of the brain using 3D-PEDOT fibrous electrodes are indistinguishable from recordings using conventional glass or platinum electrodes. In vivo studies reveal minimal reactive gliosis in response to electrode implantation.
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