Dual-signal lateral flow immunoassay for rapid detection of ochratoxin A based on polydopamine nanoparticles and gold nanocluster

Ochratoxin A (OTA) is a mycotoxin which can seriously affect people's health. Therefore, it is urgent to establish a convenient, rapid and efficient method for detecting OTA. In this paper, a lateral flow immunoassay strip based on polydopamine nanoparticles (PDANs) and gold nanocluster (AuNC) was developed for rapid detection of OTA with colorimetric and fluorescence dual mode. Without OTA, the monoclonal antibody (mAb)-PDANs was captured by OTA-BSA on the Test line (T-line), and a brown line can be observed by naked eyes. Meanwhile, the fluorescence of AuNC which was pre-coated on the T-line was quenched by the PDANs. With OTA, the mAb-PDANs combined with OTA, and mAb-PDANs cannot be captured on the T-line by OTA-BSA. As a result, the brown line disappeared, and the fluorescence of AuNC recovered. The linear ranges of colorimetric and fluorescence modes were 3.90–62.5 ng/mL and 0.98–15.63 ng/mL with the limits of detection (LOD) of 0.084 ng/mL and 0.032 ng/mL, respectively. And the visual limits of detection (VLOD) were 0.25 ng/mL and 0.49 ng/mL, respectively. This novel test strip was convenient in on-site instant detection with good selectivity and satisfactory recovery.