Zr‐MOF Mediated Gate Polarity Switching in Organic Photoelectrochemical Transistor‐Photoelectrochemical‐Colorimetric Three‐Mode Biosensor for m ⁶ A RNA Detection

Abstract A Bi 4 O 5 I 2 /BiOBr Z‐Scheme heterojunction‐gated organic photoelectrochemical transistor (OPECT) biosensor is developed for ultrasensitive detection of N 6 ‐methyladenosine (m 6 A). Catalyzed by the FTO protein, m 6 A in RNA is oxidized to be N 6 ‐hydroxymethyladenosine (hm 6 A), and this RNA sequence is then hydrolyzed by RNase A to generate N 6 ‐hydroxymethyladenosine monophosphate (hm 6 AMP), which is further captured on the gate by hexakis‐(6‐mercapto‐6‐deoxy)‐α‐cyclodextrin based on the covalent reaction between ─CH 2 OH and ─SH. Subsequently, Zr‐MOF is immobilized through coordination between the phosphate group of hm 6 AMP and Zr 4+ . Leveraging its phosphatase‐like activity, Zr‐MOF catalyzes the hydrolysis of Na 3 SPO 3 to generate H 2 S, which in situ reacts with Bi 4 O 5 I 2 /BiOBr gate to form double‐II heterojunction of Bi 2 S 3 /Bi 4 O 5 I 2 /BiOBr gate, enabling photocurrent polarity inversion and better adapting to depletion transistors employing PEDOT:PSS as the organic semiconductor layer. Concurrently, Zr‐MOF catalyzes the conversion of colorless p ‐nitrophenyl phosphate to yellow p ‐nitrophenol, achieving the colorimetric (CL) detection of m 6 A‐RNA. Most importantly, the prepared novel OPECT‐PEC‐CL three‐mode biosensor has excellent selectivity and high sensitivity for m 6 A detection with detection limits as low as 3 f m , 0.15 p m, and 0.24 n m , respectively. Additionally, this study explores the effects of plasticizers and microplastic contaminants on root and leaf growth and m 6 A levels in rice seedlings.