Biocompatible AgInS2@hydrogel microelectrode with enhanced photoelectrochemical sensitivity for real-time in vivo dopamine monitoring

Abstract

In situ monitoring of neurochemical dynamics is pivotal for understanding brain function and diagnosing neurological disorders. Conventional photoelectrochemical (PEC) sensors face limitations due to poor tissue compatibility and insufficient light penetration depth in vivo. Herein, we present a transparent and conductive hydrogel-based microelectrode (AgInS₂@hydrogel) that integrates a biocompatible topological hydrogel with an AgInS₂ semiconductor for selective dopamine (DA) detection. The hydrogel, synthesized via copolymerization of acrylamide and PR-PEGMA crosslinker with PEDOT:PSS as a conductive filler, exhibits tissue-matching elasticity (Young's modulus ≈118 kPa) and high conductivity (177 mS m⁻¹). The AgInS₂ semiconductor, in situ grown on the hydrogel surface, generates reactive oxygen species under visible light, triggering DA polymerization into polydopamine (PDA). This process establishes a self-enhancing feedback loop between AgInS₂ and PDA, enabling selective DA detection with a linear range of 0.2–4 μM and limit of detection of 64 nM. Implanted into the mouse striatum, the sensor successfully tracked dynamic DA fluctuations induced by nomifensine maleate, demonstrating its capability for real-time in vivo neurochemical analysis. This work advances the development of minimally invasive, high-sensitivity tools for brain research.