Integrating multiple probes for simplifying signal-on photoelectrochemical biosensing of microRNA with ultrasensitivity and wide detection range based on biofunctionalized porous ferroferric oxide and hypotoxic quaternary semiconductor

A facile and signal-on photoelectrochemical (PEC) biosensing strategy was designed based on hypotoxic Cu₂ZnSnS₄ NPs nanoparticles (NPs) and biofunctionalized Fe₃O₄ NPs that integrated recognition units with signal elements, without the need for immobilization of probes on the electrode. Cu₂ZnSnS₄ NPs were used as the PEC substrate to produce intensive and stable photocurrent. The porous magnetic Fe₃O₄ NPs displayed favorable loading capacity for CdS QDs and easy biofunctionalization by negatively charged capture DNA (cDNA). cDNA sealed the pore of Fe₃O₄ NPs, avoiding the escape of CdS QDs as a PEC sensitizer. After hybridizing with target microRNA (miRNA), cDNA split away off Fe₃O₄ NPs whose porous channel might open and release sealed CdS QDs (signal element), resulting in a dramatical enhancement of PEC response. Herein, miRNA hardly contacted with CdS QDs, effectively avoiding harm to the target miRNA. This proposed strategy simplified procedures of assembly and made the biorecognition process sufficient for promoting a stationary quantity of probes, which was expected to obtain satisfactory performance for bioassay. Using miRNA-155 as a model analyte and combining with duplex-specific nuclease (DSN)-assisted amplification, a simplified and signal-on PEC biosensing platform for miRNA-155 with wonderful performance was proposed. DSN-assisted amplification further promoted PEC signal increment, leading to ulteriorly improving sensitivity (detection limit of 0.17 fM) and linear range (6.5 orders of magnitude) for miRNA-155 assay. Moreover, the developed PEC biosensing platform exhibited satisfactory stability, excellent specificity, and favorable accuracy for miRNA-155, which would have a promising prospect for monitoring miRNA expression in tumor cells.