Enzymatically Mediated In Situ Generation of Z-Scheme Bi₂S₃/Bi₂MoO₆ Heterojunction-Based Organic Photoelectrochemical...

The OPECT biosensing platform, which connects optoelectronics and biological systems, offers significant amplification and more possibilities for research in biological applications. In this work, a homogeneous organic photoelectrochemical transistor (OPECT) biosensor based on a Bi₂S₃/Bi₂MoO₆ heterojunction was constructed to detect METTL3/METTL14 protein activity. The METTL3/METTL14 complex enzyme was used to catalyze adenine (A) on an RNA strand to m⁶A, protecting m⁶A-RNA from being cleaved by an E. coli toxin (MazF). Alkaline phosphatase (ALP) catalyzed the conversion of Na₃SPO₃ to H₂S through an enzymatic reaction. Due to the adoption of the strategy of no fixation on the electrode, the generated H₂S was easy to diffuse to the surface of the ITO electrode. The Bi₂S₃/Bi₂MoO₆ heterojunction was formed in situ through a chemical replacement reaction with Bi₂MoO₆, improving photoelectric conversion efficiency and realizing signal amplification. Based on this "signal on" mode, METTL3/METTL14 exhibited a wide linear range (0.00001-25 ng/μL) between protein concentration and photocurrent intensity with a limit of detection (LOD) of 7.8 fg/μL under optimal experimental conditions. The applicability of the developed method was evaluated by investigating the effect of four plasticizers on the activity of the METTL3/METTL14 protein, and the molecular modeling technique was employed to investigate the interaction between plasticizers and the protein.