Nanobodies-based colloidal gold immunochromatographic assay for specific detection of parathion

Parathion is one of organophosphorus pesticide, which has been prohibited in agricultural products due to its high toxicity to human beings. However, there are still abuse cases for profit in agricultural production. Hence, we established nanobodies-based colloidal gold immunochromatographic assay (GICA) in which nanobodies (Nbs) as an excellent recognition element, greatly improving the stability and sensitivity of ICA. Under the optimal conditions, the developed Nbs-based GICA showed a cut-off value of 50 ng/mL for visual judgment and a half-inhibitory concentration (IC₅₀) of 2.39 ng/mL for quantitative detection. The limit of detection (LOD) was as low as 0.15 ng/mL which was significantly 50-fold higher sensitivity than the commercial mAb-ICA. Additionally, this method exhibited good recoveries for the detection of cabbage, cucumber, and orange samples and excellent correlation with the UPLC-MS/MS method. The results showed that this method developed in this work based on nanobody can be used in practical detection of parathion in foods and nanobody is novel prospective antibody resource for immunoassays of chemical contaminants.