Conducting Polymer-Hydrogel Interpenetrating Networks for Improving the Electrode-Neural Interface

Implantable neural microelectrodesare recognized as a bridge forinformation exchange between inner organisms and outer devices. Combinedwith novel modulation technologies such as optogenetics, it offersa highly precise methodology for the dissection of brain functions.However, achieving chronically effective and stable microelectrodesto explore the electrophysiological characteristics of specific neuronsin free-behaving animals continually poses great challenges. To resolvethis, poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate)/poly(vinylalcohol) (PEDOT/PSS/PVA) interpenetrating conducting polymer networks(ICPN) are fabricated via a hydrogel scaffold precoating and electrochemicalpolymerization process to improve the performance of neural microelectrodes.The ICPN films exhibit robust interfacial adhesion, a significantlylower electrochemical impedance, superior mechanical properties, andimproved electrochemical stability compared to the pure poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate)(PEDOT/PSS)films, which may be attributed to the three-dimensional (3D) porousmicrostructure of the ICPN. Hippocampal neurons and rat pheochromocytomacells (PC12 cells) adhesion on ICPN and neurite outgrowth are observed,indicating enhanced biocompatibility. Furthermore, alleviated tissueresponse at the electrode-neural tissue interface and improvedrecording signal quality are confirmed by histological and electrophysiologicalstudies, respectively. Owing to these merits, optogenetic modulationsand electrophysiological recordings are performed in vivo, and an anxiolytic effect of hippocampal glutamatergic neurons onbehavior is shown. This study demonstrates the effectiveness and advantagesof ICPN-modified neural implants for in vivo applications.