Photoelectrochemical biosensor based on FTO modified with BiVO4 film and gold nanoparticles for detection of miRNA-25 biomarker and single-base mismatch

MicroRNAs (miRNAs) are of great important as non-invasive biomarkers for early diagnosis of cancer. Based on this, a photoelectrochemical (PEC) biosensor was developed to measure the concentration of microRNA-25 (miR-25), as a lung cancer biomarker. To fabricate the PEC biosensor, a suitable amino modified probe was immobilized on the surface of a florin tin oxide (FTO) electrode modified with bismuth vanadate (BiVO4) film and gold nanoparticles (AuNPs). The fabrication steps of the PEC biosensor were monitored by electrochemical impedance spectroscopy (EIS) and PEC measurements. The results indicate that the combination of BiVO4 film and AuNPs enhances the separation of photogenerated electrons and increase the photocurrent signal. Upon hybridization of the probe immobilized on the biosensor with miR-25, the photocurrent is significantly decreased. This current decrease is attributed to the fact that the hybridization processes blocks the electrode surface by creating a steric hindrance and by decrease the diffusion of AA to the electrode surface, it reduces the AA oxidation and subsequently decreases the capture photogenerated holes. Therefore, the amount of photocurrent decrease is dependent on the miR-25 concentration, and this PEC biosensor can be used to measure miR-25. The developed PEC biosensor shows good sensitivity for the determination of miR-25 in the linear concentration range of 1.0 × 10−14 M to 1.0 × 10−6 M with a detection limit of 3.4 fM, under optimal conditions. Using this biosensor, miR-25 can be detected from a non-complementary and one base mismatch sequence. It is also possible to measure miR-25 in human serum samples with satisfactory results using the PEC biosensor.