A novel interpenetrating conductive hydrogel neural electrode interface was revealed

Long-term effective electrophysiological signal detection is essential for the accurate interpretation and regulation of neural circuits. However, issues such as the stability and biocompatibility of neural electrode interfaces still seriously hinder the in vivo application of implantable neural electrodes.

Recently, the latest research results of Lu Yi’s team, a researcher at the Institute of Brain Cognition and Brain Diseases of the Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, and the Shenzhen-Hong Kong Institute of Brain Science Innovation, were published in ACS Applied Materials and Interfaces. The team developed a conductive polymer-hydrogel interface with an interpenetrating structure, which significantly improved the long-term stability and effectiveness of neural electrodes, and provided an important tool for the functional elucidation of neural circuits in freely active animals.

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Poly(3,4-ethylenedioxythiophene) (PEDOT) is a modified conductive polymer material widely used at the interface of neural electrodes, with low electrochemical impedance and good biocompatibility. However, poor electrochemical and mechanical stability makes PEDOT films easily detached from the electrode substrate, which seriously affects the long-term use of neural electrodes.

In this regard, a novel electrode interface modification strategy is proposed. The research team first prepared a polystyrene sulfonic acid/polyvinyl alcohol (PSS/PVA) hydrogel membrane and formed a pre-coating on the surface of the microelectrode array to form a three-dimensional network hydrogel scaffold rich in pective ions (PSS-). Subsequently, the researchers electropolymerized 3,4-ethylenedioxythiophene monomer in a PSS/PVA scaffold to form a PEDOT/PSS/PVA conductive polymer-hydrogel electrode interface with a three-dimensional interpenetrating structure.

It was found that the prepared PEDOT/PSS/PVA conductive polymer-hydrogel membrane had a three-dimensional porous structure with pore sizes ranging from 0.1 to 1.0 microns. The above structure can effectively counteract the membrane deformation caused by repeated charge transport processes, significantly improving its electrochemical stability. In addition, this conductive polymer-hydrogel membrane has a low Young’s modulus (191 kPa) and high stretchability (72%), with excellent mechanical stability. The research team also found that this conductive polymer-hydrogel membrane has low electrochemical impedance, high capacitance, and excellent biocompatibility, making it an ideal neural electrode interface material.

Subsequently, the research team compared the electrophysiological signal quality of PEDOT/PSS/PVA and PEDOT/PSS neural electrode arrays after 12 weeks of implantation in the hippocampal region of mice, and found that PEDOT/PSS/PVA conductive polymer-hydrogel membrane can significantly improve the long-term stability of electrophysiological signals. The research team combined interface modification technology with optogenetic technology to achieve electrophysiological recordings under precise neural regulation on freely mobile mice, which provided a powerful tool for the functional study of neural circuits.

This work not only provides important technical support for neural circuit function research and brain-computer interface research, but also is expected to provide new tools for the diagnosis and treatment of neuropsychiatric diseases. (Source: China Science News, Diao Wenhui)

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