Photo-driven gated dual-mode aptasensor based on CQDs@PCN-224@ZIF-8 and Exo I-HCR cascade amplification for ultrasensitive bisphenol A detection.

Dual-mode biosensors offer an effective strategy for reducing signal ambiguity and improving the reliability of trace small-molecule detection. However, integrating photo-driven transduction, fluorescence modulation, and nucleic acid cascade amplification into a single sensing system remains challenging. Herein, a photo-driven fluorometric/colorimetric dual-mode aptasensor was developed for ultrasensitive bisphenol A (BPA) detection by coupling a CQDs@PCN-224@ZIF-8 nanoplatform with Exonuclease I (Exo I)-mediated target recycling and hybridization chain reaction (HCR) amplification. The CQDs@PCN-224@ZIF-8 interface enabled fluorescence quenching of FAM-labeled probes and visible-light-driven TMB oxidation, while the Exo I-HCR cascade converted BPA recognition into amplified optical responses. The proposed aptasensor achieved detection limits of 0.76 pM and 3.47 pM for the fluorometric and colorimetric modes, respectively. The dual-output readout provided mutually supportive signal validation, improving the reliability of BPA detection. The aptasensor showed satisfactory selectivity, stability, and reproducibility, and was applied to BPA-spiked milk, bottled water, and canned yellow peach samples with acceptable recovery results, which were consistent with those obtained using the LC-MS/MS-based national standard method. Furthermore, smartphone-assisted RGB readout enabled visual quantification, highlighting the potential of the proposed platform for on-site BPA monitoring in food safety applications.