Dual‐Mode Detection of RNA Demethylation Protein ALKBH3 Using a Two‐Legged DNA‐Walker‐Mediated BiOI/In ₂ O ₃ ‐Gated Organic Photoelectrochemical Transistor Biosensor

Abstract Organic photoelectrochemical transistor (OPECT) biosensors have emerged as prevalent candidates for bioanalytical technologies because of their intrinsic amplification properties and excellent detection performance. Herein, a novel OPECT biosensor for analyzing the RNA demethylation protein ALKBH3 is developed. A BiOI/In ₂ O ₃ type‐II heterojunction is employed as the photoactive material for the gate, and an organic semiconductor, poly(3,4‐ethylenedioxythiophene): poly(styrenesulfonic) (PEDOT:PSS), is used as the channel modification material. ALKBH3‐mediated RNA demethylation, as a switch, triggered the trans‐cleavage activity of the CRISPR‐Cas12a system, which subsequently leads to a failure in the formation of a bipedal DNA walker. Contrarily, ferrocenecarboxylic acid (FcA), which acts as an effective electron donor, cannot be captured, leading to modulation of the gating characteristics and degradation of the channel current response. Compared to the conventional photoelectrochemical method, the OPECT biosensor exhibits higher sensitivity and a lower detection limit for ALKBH3 protein, thereby facilitating the monitoring of ALKBH3 protein activity changes under the effect of environmental pollutants and demonstrating the crucial biomarker potential of ALKBH3 protein in evaluating its toxicological effects.