An aptamer based lateral flow strip for on-site rapid detection of ochratoxin A in Astragalus membranaceus

An aptamer based lateral flow strip based on competitive format was developed for on-site rapid detection of ochratoxin A (OTA) in Astragalus membranaceus. Some crucial parameters that might influence the sensitive detection, such as the characterization of the colloidal gold, size and shape of gold nanoparticles (AuNPs), amount of AuNPs-aptamer conjugate, migration rate and the addition amount of methanol, were investigated to provide the optimum assay performance. To perform the test, 1g sample was extracted with 2.5mL of methanol-water (80:20, v/v) and diluted by 4-fold running buffer to eliminate the matrix and methanol interferences. Under optimized conditions, the aptamer-based assay showed a visual limit of detection (LOD) of 1ngmL(-1), and with no significant cross-reactivity with several homologous toxins. The whole detection could be completed within 15min without special equipment because of available visual results. One out of nine A. membranaceus samples was found to be positive of OTA, which was in a good agreement with those obtained from LC-MS/MS analysis. The results demonstrated that the aptamer-based lateral flow assay could be used as a rapid, reliable, cost-effective and robust on-site screening technique for mycotoxins at trace level in complex matrices without special instrumentation.