Enzyme-Activated Biosensing with a Split-Type, Self-Powered, Near-Infrared-Responsive Photoelectrochemical Platform:...

Self-powered photoelectrochemical (SP-PEC) sensing systems address the limitations of traditional PEC systems by eliminating external bias interference and enabling stable signal generation via Fermi level-driven electron transfer. Herein, a near-infrared (NIR)-responsive split-type SP-PEC biosensor for sensitive and specific tyrosinase (TYR) detection was constructed based on leveraging quinone-amine bioconjugation chemistry. The sensing platform consisted of a CuInS₂/CuO photocathode and a MoS₂/BiO_2-X/Bi₂S₃@PDA photoanode, both designed to operate efficiently under NIR illumination. In such a sensor, dopamine (DA) played two roles, namely, as a conductive medium at the photoanode and as a substrate for TYR at the photocathode. When TYR was present, it activated DA oxidation in a 96-well microplate to generate quinones, which were then conjugated onto a chitosan-modified photocathode to behave as an electron acceptor, resulting in promoted photoelectric conversion and detection accuracy. Thus, the photocathode formed the sensing interface, and the photoanode further amplified the output signal when connected with the photocathode. Under optimum conditions, the sensor achieved an ultralow detection limit of 0.00089 U/mL with a linear detection range from 0.001 to 6.0 U/mL. Its practical applicability was confirmed through successful TYR analysis in real potato samples, validated by the high-performance liquid chromatography method. The split-type design enabled sensing without electrode-bound biorecognition elements, with the biological process separate from the photoelectrode, ensuring simplified operation, fast response, and improved accuracy.