Target-induced elimination of photosensitizer and formation insulation layer enabling ultrasensitive photoelectrochemical detection of ochratoxin A

An efficient photoelectrochemical aptasensor with triple signal amplification was developed for sensitive determination of ochratoxin A (OTA). Briefly, gold nanoparticles were decorated onto the GO-CdS-MoS2 nano-composites to form GO-CdS-MoS2-AuNPs nanostructure, which was utilized as the photoelectrochemical matrix to immobilize the auxiliary DNA (aDNA) for the following hybridization with the complementary OTA aptamer (OTA Apt). Then, porphyrin (TMPyP) molecules employed as an efficient photosensitizer can be intercalated into double-stranded DNA (dsDNA). Thus, an enhanced initial PEC signal was acquired. Upon introduction of OTA, the aptamer-OTA complex was formed and detached from the electrode, while the TMPyP molecules releasing from the platform. The photocurrent signal was highly decreased ascribed to the target induced elimination of photosensitizer. Then, the SiO2@helpDNA (SiO2 @hDNA) can be assembled on the electrode through the re-exposed aDNA. Notably, the steric hindrance of the SiO2 and hDNA may effectively depress the electron transfer, thus obviously enlarge the decrement of the photocurrent responses. Under optimized condition, the program shows satisfied analytical performance for OTA with a low detection limit of 0.00021 ng mL(-1). Meanwhile, it also presents outstanding reproducibility, stability and specificity. Importantly, the sensing platform provides a new ideal for detection of toxins.