Chiral-Specific Recognition-Based Organic Photoelectrochemical Transistor Biosensor for Ultrasensitive Detection of Okadaic Acid

Chiral functional materials have garnered extensive attention due to their unique optical effects, such as circular dichroism and circularly polarized luminescence. However, their implementation in organic photoelectrochemical transistors (OPECT) remains a largely unexplored area. The application of chiral self-assembly to OPECT can facilitate the direct perception and conversion of chiral information, allowing for highly selective recognition of enantiomers. In this study, a competitive immunoassay was developed for the quantitative detection of the marine algal toxin okadaic acid (OA), using liposome-encapsulated l-cysteine (l-Cys) as an electron donor. In this method, OA competes with okadaic acid-bovine serum albumin (OA-BSA) immobilized on the liposome surface for binding to antibodies. After binding, the liposomes are lysed to release l-Cys, which undergoes chiral recognition self-assembly with l-porphyrin on the gate electrode, leading to a significant increase in photocurrent. Under light irradiation, cations from the electrolyte migrate into the poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) channel, resulting in a pronounced decrease in the channel current (IDS). Since different concentrations of OA competitively affect the amount of l-Cys released, thereby modulating the extent of chiral self-assembly and the photocurrent signal, a straightforward approach for the determination of OA by utilizing the chiral effect was established based on a CdIn₂S₄/l-porphyrin-gated OPECT biosensor, exhibiting excellent sensitivity and a low detection limit of 33.8 pM. The OPECT platform based on chiral-specific recognition effects holds significant implications for the effective monitoring of marine ecological environment safety and food security.