Novel Orthogonal FL-OPECT Bimodality Enabled by Magnetic-Switchable HOF@Bi2S3 Channels for One-Pot Binary Toxin Decoding

Abstract Integrating optical and optoelectronic readouts for dual-target detection remains a formidable task using conventional designs. In this study, a novel fluorescence-organic photoelectrochemical transistor (FL-OPECT) dual-mode biosensor was constructed for simultaneous detection of marine red tide algal toxins okadaic acid (OA) and gonyautoxin 1/4 (GTX 1/4) based on a HOF-101@Bi2S3 heterojunction and dual-magnetic bead separation system (DMBSS). The HOF-101@Bi2S3 type-II heterojunction served as the photo-gate electrode, highly enhancing visible light absorption and charge separation. Leveraging aptamer-based capture and competitive displacement, the DMBSS enabled both high-specificity recognition and efficient isolation of the dual targets. After magnetic separation, the supernatant was employed for OA quantification via FL intensity, whereas the precipitate-bound MB2 modulated the photocurrent response for GTX 1/4 detection. Under optimal conditions, the biosensor exhibited linear ranges of 0.1−100.0 nM for both toxins, with detection limits of 14.5 pM and 31.94 pM for OA and GTX 1/4, respectively. Moreover, the platform presented a high selectivity, good stability, and satisfactory performance in real samples. This FL-OPECT strategy offers a new approach for simultaneous phycotoxin detection and shows great potential for marine food safety monitoring.