Simultaneous electrochemical determination of ochratoxin A and fumonisin B1 with an aptasensor based on the use of a Y-shaped DNA structure on gold nanorods

A complementary DNA (cDNA) was designed to simultaneously hybridize with the ochratoxin A (OTA) aptamer and the fumonisin B1 (FB1) aptamer to form a unique Y-shaped DNA structure and to achieve simultaneous detection. Gold nanorods (AuNRs) were used to immobilize thionine (Th), thiolated ferrocene (Fc), thiolated OTA aptamer (Apt1), and thiolated FB1 aptamer (Apt2), to form an amplified signal element and a recognition element. The Apt1-AuNRs-Th complex and the Apt2-AuNRs-Fc complex hybridize with cDNA to form a unique Y-DNA structure on a gold electrode. This produces two initial electrochemical signals [with 177 mu Alpha cm(-2) near -0.2 V, and 3121 mu Alpha cm(-2) near +0.46 V (vs. Ag/AgCl)] by differential pulse voltammetry. Upon addition of 0.1 ng mL(-1) OTA and 0.1 ng mL(-1) FB1, the aptamers bind the two toxins. This results in the release of Apt1-AuNRs-Th and Apt2-AuNRs-Fc, so the peak currents densities decrease to 115 mu Alpha cm(-2) and 209 mu Alpha cm(-2). The assay allows simultaneous determination of OTA and FB1 in the 1.0 pg center dot mL(-1) to 100 ng center dot mL(-1) concentration ranges, with LODs of 0.47 and 0.26 pg center dot mL(-1). The assay is reproducible, stable and specific. It was applied to the determination of OTA and FB1 in spiked beer, with recoveries between 89.0% and 102.0%.