In this study, a simple and sensitive aptamer-based colorimetric method for the detection of Ochratoxin A by using gold nanoparticles (AuNPs) has been developed. In this assay, unmodified gold nanoparticles (AuNPs) were used as probes with a 36-mer aptamer as recognition element. In the absence of ochratoxin A, free aptamer could be adsorbed onto the surface of AuNPs and protect AuNPs from aggregation even with high concentrations of salt. The salt-induced aggregation of AuNPs was caused by the specific recognition of aptamers with OTA. Under optimum conditions, calibration modeling showed that the analytical linear range covered from 32 to 1024 ng/mL and the detection limit of 20 ng/mL was realized successfully. This proposed colorimetric bio-assay also showed high selectivity over other antibody based methods. Meanwhile, this strategy was further used to determine the concentrations of ochratoxin A in white wine sample with satisfying recovery rates.
Keywords: Colorimetric detection; aptamers; fortified white grape wine; gold nanoparticles; ochratoxin A.