Gold nanoparticles-functionalized microorganisms assisted construction of immunobiosensor for sensitive detection of ochratoxin A in food samples

A simple and novel immunochromatographic assay (ICA) was developed for specific and sensitive determination of ochratoxin A (OTA) employing microorganism (MO) as reducers and carriers. In this work, microorganism loaded gold nanoparticles (MO@AuNPs) composites were synthesized by reacting Yeast/Lactobacillus (LAB) with HAuCl4 via biosorption and subsequent bioreduction. The synthesis conditions (pH and reaction time) and main parameters (morphology, diameter and functional groups) of MO@AuNPs were investigated. Owing to the large sizes (about 2 mu m) and high adsorption abilities of MO@AuNPs, the few antibodies were labeled, resulting a lower detection limit for ICA. After optimization, the linear detection of OTA using MO@AuNPs-based immunoassay ranged from 0.1 to 1.6 ng/mL, and the visual limit of detection (vLOD) was 0.1 ng/mL, which was nearly 8-fold lower than traditional AuNPs-ICA. Meanwhile, the proposed strategy also possessed high specificity for OTA against other mycotoxins. The applicability of the platform was successfully assessed through the detection of OTA in rice, corn, ginger and green bean samples. The results indicated that these creative sensing elements are promising alternatives and bring an innovative inspiration for biological detections.