Iridium Oxide Nanoparticle–Protein Corona Neural Interfaces with Enhanced Electroactivity and Bioactivity Enable Electrically Manipulatable Physical and Chemical Neuronal Activation

Abstract

Iridium oxide (IrOx) is a promising implantable electrode material owing to its remarkable neural stimulation capacity. However, presently, IrOx electrodes lack biocompatibility and bioactive interactions with nerve tissues. Application of polymeric surface coatings results in a weak physical adhesion at the organic/inorganic interface, which limits their wide‐scale application. Herein, a smart iridium oxide‐plasma protein (IrOx‐PP) electrode with enhanced electroactivity, electrochemical stability, cytocompatibility, and bioactivity that can provide controllable topographical, electrical, and chemical stimuli to enhance neuronal activity is proposed. In the inorganic/organic nanoparticle (NP)‐protein corona structures, the soft NP‐corona led to repeated burst‐to‐zero‐to‐burst PP release, while the hard NP‐corona with an ordered atomic structure enhanced the electrochemical stability and bioactivity. The incorporated PP resulted in a higher current storage capacity, lower impedance, better cell growth, and significant neurite outgrowth compared with those obtained with pristine IrOx. The application of electrical stimulation to IrOx‐PP enabled simultaneous neuromodulation, on‐demand PP release, and cell uptake, with a 2‐fold higher cell density and significant neurite outgrowth on IrOx‐PP than on pristine IrOx. This bioactive inorganic‐organic hybrid electrode with the combined features of physical properties and improved neuromodulation is expected to be a revolutionary platform for efficient and biocompatible neural implantation.

Conducting polymer‐based nanostructured materials for brain–machine interfaces

“…Another approach involves the electrochemical or layer‐by‐layer deposition of Au, Ag, or IrOx to create nanoparticles (Bao et al, 2019; Chan et al, 2021; D. Lee et al, 2018; H. Zhang et al, 2012) or nanograins (R. Kim et al, 2013) on the electrode surface. Zhang et al used a layer‐by‐layer technique to deposit CNTs or Au NPs in poly(diallyl dimethylammonium chloride) (PDDA) on the electrode (H. Zhang et al, 2012).…”

Strategies for interface issues and challenges of neural electrodes

“…13,14 To achieve a high performance nerve-electrode interface, attention should be paid to the following aspects: (i) the charge transfer mechanism of diverse electrode materials needs to be clarified, since the electrical deviations of neural interfaces bring about obstacles to signal transmission and detection. 15–17 (ii) An excellent electrochemical performance of the neural electrode is highly desired, 18,19 including electrochemical impedance, 20,21 charge storage capacity (CSC), 22,23 charge injection limit (CIL, it is defined as the maximum charge density that can be injected into the tissue under the safe potential window measured by cyclic voltammetry) 24–26 and so on. Among them, a low impedance favors monitoring the electrophysiological signal with more details.…”

In Vivo Chronic Brain Cortex Signal Recording Based on a Soft Conductive Hydrogel Biointerface

“…Nanostructured hydrogels are a combination of nanotechnology and biomaterial science that can improve electrical properties. Hydrogel matrices have been loaded with conductive materials such as metallic fillers ( e.g ., nanowires, nanoflakes, or micro- or nanoparticles), and carbon-based conductive materials ( e.g ., nanotubes or graphene) to form a percolation network within a hydrogel matrix. − The advantages of this approach include signal transmission by the transfer of ions and small molecules, similarly to human biological tissues . Thus, tissues have a much higher electrical conductivity than when electrons and holes are used as the charge carriers in metal electronic devices.…”