Smartphone-assisted dual-mode portable sensor for highly sensitive detection of ochratoxin A in foods

Ochratoxin A (OTA), a highly toxic mycotoxin that widely contaminates cereal foods, not only poses a serious threat to human health but also endangers the safety of livestock through accumulation in the food chain. To address this concern, we developed a novel portable paper-based dual-mode sensing platform utilizing BSA-coated gold nanoclusters (BSA@AuNCs) for the sensitive detection of OTA. This innovative strategy synergistically integrates electrochemical immunosensing with paper-based fluorescence sensing, enabling collaborative detection and cross-validation of signals via two independent yet complementary mechanisms. In the electrochemical mode, a uniform BSA@AuNCs nanocomposite layer was deposited on a carbon paper substrate, followed by the immobilization of anti-OTA antibodies via EDC/NHS chemistry. This configuration achieved a wide linear detection range from 0.002 to 200 ng mL^-1 and an ultra-low detection limit of 0.8 pg mL^-1. The high accuracy and reliability of the electrochemical method were further validated by the elliptical joint confidence region test. Simultaneously, the fluorescence mode combines the inherent fluorescence of BSA@AuNCs with smartphone imaging technology to achieve a linear range of 0.01-50 ng mL^-1 and a detection limit of 2 pg mL^-1. This mode allows for visual and semi-quantitative detection, making it ideally suited for rapid on-site screening. The developed dual-mode platform demonstrates high sensitivity, robustness, and practical utility, offering a powerful and reliable technical approach for OTA monitoring with promising applications in food safety surveillance.