Target-Induced Chemical Reaction Modulated Optical Fiber-Gated Organic Photoelectrochemical Transistor for in Vivo H2S Detection.

Real time detection of hydrogen sulfide (H2S) in deep brain regions is of great significance. Photoelectrochemical (PEC) biosensors hold promise for real-time monitoring but low sensitivity due to the use of small electrode restrained its application. In this study, a miniaturized sensor that integrates organic photoelectrochemical transistors (OPECTs) with optical fiber (OF) microelectrodes was designed for the first time, which can amplify the small PEC signal into large channel current change. A conductive gold layer and cuprous oxide nanoparticles (Cu2O NPs) were sequentially deposited onto the OF, followed by a Nafion polymer coating to enhance anti-interference capabilities. Cu2O reacts with H2S to generate Cu2S. The resulting Cu2O/Cu2S heterojunction induces changes in the PEC signal and channel current. Compared to a conventional PEC system, the OPECT sensor has higher sensitivity and lower detection limit, enabling monitoring of H2S concentration fluctuations within the rat brain, which demonstrates the approach's capability for highly sensitive in vivo biomarker detection.