Highly efficient photoelectrochemical biosensor for the evaluation of bisphenol A-induced microRNA-21 expression alterations.

Herein, we developed a photoelectrochemical (PEC) biosensor integrating SrTiO3 and SnO2 materials with a dumbbell DNA mediated target recycling system to quantify microRNA-21 levels under bisphenol A (BPA) exposure. The engineered SrTiO3/SnO2 photoelectrode demonstrated enhanced charge separation efficiency due to band alignment, yielding a remarkable 33-fold photocurrent enhancement compared to that of pure SrTiO3. In addition, a dumbbell DNA-based signal amplification strategy was designed and the target microRNA-21 was converted to DNA nanospheres, which can "switch-on" the PEC signal by loading the signal mediator methylene blue. Through the synergistic optimization of photoelectric performance and signal amplification, the biosensor achieved ultrasensitive microRNA-21 detection with a detection limit of 2.1 fM. The PEC biosensor was employed to monitor the BPA-induced microRNA expression alterations. This study provides a promising paradigm for the construction of PEC biosensors for use in potential environmental toxicological evaluation.