Ultrasensitive photoelectrochemical biosensor based on black/red phosphorus heterojunction@Bi2Te3 hybrid and enzymatic signal amplification for the detection of colorectal cancer-related piRNA-823

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Piwi-interacting RNAs (piRNAs) are a class of noncoding small RNAs that have been identified as promising biomarkers for cancer detection. However, the development of emerging detection methods for piRNAs has not attracted widespread attention. In this work, we proposed an ultrasensitive photoelectrochemical (PEC) biosensor that combines photosensitive hybrid with enzymatic signal amplification strategy for detecting colorectal cancer (CRC)-related piRNA-823. The synergy of the type-II heterostructure between red phosphorus (RP) and black phosphorus (BP), the photothermal effect of BP, and the excellent electron transfer capability and thermoelectric effect of Bi2Te3 endowed the BP/RP heterojunction@Bi2Te3 hybrid with excellent photoelectric conversion performance. The connection of the poorly conductive composite probe system (SiO2-COOH-p2-p1) significantly reduced the photocurrent. The target triggered the release of SiO2-COOH-p2 from the electrode surface and the subsequent specific cleavage of p1 by duplex-specific nuclease, which significantly restored the photocurrent. The released target could react with other composite probes to form a photocurrent signal-increasing cycle. The PEC biosensor showed a linear detection range of 0.1–106 fM and a calculated detection limit of 0.016 fM. In addition, the PEC biosensor exhibited a stable photocurrent response under continuous on-off irradiation and could clearly distinguish the target from the mismatch sequences. The accuracy of the PEC biosensor in detecting piRNA-823 in clinical serum samples was verified by RT–qPCR, and the PEC biosensor could distinguish healthy controls from CRC patients. This work provides a new strategy for ultrasensitive liquid biopsy of piRNAs.