Ce/Zr-MOF-and TCEP-Mediated Ascorbic Acid Generationfor In Situ Oxygen Vacancy Regulation in Bi4O5I2/Bi2S3 Gate: A Triple-Mode Biosensorfor ALKBH5 Detection

Abstract An organic photoelectrochemical transistor (OPECT) biosensor featuring a Bi4O5I2/Bi2S3 type-II heterojunction gate and Ce/Zr-MOF signal amplification unit was developed for RNA demethylase ALKBH5 with photoelectrochemical (PEC), OPECT, and colorimetric analysis. ALKBH5 catalysis demethylation of RNA was utilized to induce the inhibition on ascorbic acid (AA) generation through dehydroascorbic acid reduction by tris(2-carboxyethyl)phosphine and l-ascorbic acid 2-phosphate hydrolysis by Ce/Zr-MOF catalysis, where AA acted as the bifunctional roles to trigger an increased detection signal with reductant agent to engineer the oxygen vacancy of Bi4O5I2 and electron donor to capture photogenerated holes. The biosensor achieved sensitive PEC and OPECT detection based on the intrinsic signal amplification induced by the organic photoelectrochemical transistor itself as well as the extrinsic signal amplification derived from the heterojunction structure and bifunctional AA. Moreover, based on the Ce/Zr-MOF bifunctional nanozyme with phosphatase-mimetic activity toward PNPP and oxidase-mimetic activity toward TMB, ALKBH5 detection using colorimetry was also realized by PNPP hydrolysis and TMB oxidation to generate yellow and blue, respectively. The biosensor was further applied to evaluate the effect of phthalate plasticizers on the ALKBH5 activity. This work not only provides a versatile multimodal detection technology for ALKBH5 but also offers an approach for evaluating the toxicological effects of pollutants using ALKBH5 as a biomarker.