Oxygen vacancy and Z-Scheme BiOIO3@Bi4O5Br2 heterojunction cooperate to enhance the sensitivity of photoelectrochemical biosensors for the detection of DNA demethylase MBD2

The advanced structural design of semiconductor photoactive materials is the core element to improve the performance of photoelectrochemical (PEC) biosensors. By constructing a BiOIO 3 @Bi 4 O 5 Br 2 Z-Scheme heterojunction with abundant oxygen vacancies to significantly improve the photoelectric conversion efficiency, a sensitively PEC biosensor for MBD2 detection was designed by combining DNA isothermal cycle double amplification technology. Specifically, the chitosan-modified BiOIO 3 @Bi 4 O 5 Br 2 was modified on the surface of ITO electrode. Methylene blue (MB)-DNA was immobilized on due to the covalent reaction of its carboxyl group with the amino group of chitosan, and the excess amino group was blocked with acetaldehyde. In the absence of MBD2, the cleavage activity of HpaII is inhibited due to the retention of cytosine methylation. which triggers ISDPR and large amounts of single-stranded DNA complementary to MB-DNA was produced. After MB-DNA hybridization, Exo III was triggered to assist the MB-DNA hydrolysis cycle, resulting in the drop of MB, causing a decrease in the photoelectric signal. Conversely, in the presence of MBD2, it removed cytosine methylation, triggering HpaII hydrolysis and inhibiting subsequent reactions, so that the MB connected to the electrode is retained and the photoelectric signal is enhanced. The sensor had a detection range from 0.07 to 500 ng/mL with a detection limit of 0.018 ng/mL (3σ). The study also explores the effects of environmental pollutants on MBD2 activity and validated with molecular docking models, offering insights into epigenetic regulation and environmental health assessments. This work underscores the potential of advanced photoactive materials and heterojunction designs in biosensor applications.