Development of a Photoelectrochemical Biosensor for the Detection of miRNA-106b Using Electrodeposited Gold Nanoparticles on SnO 2 Spin-Coated FTO

The early and precise detection of cancer biomarkers is essential for effective cancer therapy. This study introduces a photoelectrochemical (PEC) biosensor specifically designed for the quantification of microRNA-106b (miR-106b), a biomarker linked to gastric cancer. The PEC biosensor was developed through the synthesis of tin(IV) oxide (SnO2) nanoparticles on the surface of fluorine-doped tin oxide (FTO) via a spin-coating method. Subsequently, an amino-modified single-stranded DNA (ssDNA) was immobilized onto the SnO2/FTO electrode, which was further modified with gold nanoparticles (AuNPs). The fabrication processes of the PEC biosensor were assessed by using electrochemical impedance spectroscopy (EIS) and PEC measurements. Upon hybridization of the probe attached to the biosensor with miR-106b, a substantial reduction in photocurrent was observed due to the obstruction of the electrode surface, resulting in the formation of a steric barrier. This steric hindrance limits the diffusion of ascorbic acid (AA) to the electrode surface, consequently decreasing the level of trapping of photogenerated holes. The photocurrent responses of the proposed biosensor exhibited linearity within a concentration range of 1.0 fM to 0.1 μM miR-106b, with a detection limit of 0.12 fM. The biosensor demonstrated the capability to detect miR-106b in sequences with a single base mismatch and noncomplementary bases. Furthermore, the biosensor was successfully employed to quantify miR-106b in human serum samples, yielding satisfactory results. The innovation of this research resides in the development of a photoelectrochemical biosensor specifically targeting miRNA-106b. The incorporation of electrodeposited gold nanoparticles on SnO2 spin-coated FTO represents an approach to enhancing the performance and sensitivity of the sensor. This biosensor has potential applications across a range of areas in the field of miRNA detection.