An ultrasensitive photo-driven self-powered aptasensor for microcystin-RR assay based on ZnIn2S4/Ti3C2 MXenes integrated with a matching capacitor for multiple signal amplification.

A photo-driven self-powered aptasensor was constructed based on a matching capacitor and the ZnIn2S4/Ti3C2 heterojunction as the photoanode and Cu2O as the photocathode in a dual-photoelectrode sensing matrix for multiple signal amplification for the ultrasensitive detection of microcystin-RR (MC-RR). The introduction of Ti3C2 MXene nanosheets on the photoanode surface can not only accelerate the transfer and separation of photoinduced electron/hole pairs, thus enhancing the output signal of the photo-driven self-powered system, but also provide a larger specific surface area for the immobilization of the bio-recognition unit aptamer. More importantly, for a portable and miniaturized device, a micro-workstation with the size of a universal serial bus (USB) disk and a novel short-circuit current access was proposed to capture the instantaneous output electrical signal for real-time data tracking. In such a way, a sensitivity of 2.7 mA pM-1 was achieved when the matching capacitor was integrated into the self-powered system, which was 22 times that without a capacitor. After the interaction between MC-RR and the corresponding aptamer, a 'signal-off' detection configuration was formed via the steric hindrance effect. Therefore, such a multiple signal amplification system realized the ultrasensitive and selective determination of MC-RR successfully. Under optimal conditions, the linear range of the self-powered aptasensor was 0.1 to 100 pM and the detection limit was 0.033 pM (S/N = 3). The aptasensor was applied to the detection of MC-RR in fish, exhibiting good reproducibility (≈3.88%), paving the way for detecting microcystins in real-life samples.