DETECTION OF OCHRATOXIN A BASED ON NITROGEN DOPED POROUS CARBON-APTAMER SENSOR

As the specific identification element,the aptamer of ochratoxin A was immobilized on the surface of gold electrode (AuE) based on its strong affinity and high stability.Using nitrogen doped porous carbon with a large specific surface area to carry more complementary strand DNA (cDNA),the hybridization was carried out on the AuE to obtain the nitrogen doped porous carbon-DNA/aptamer/AuE electrochemical sensor.The detection of OTA was studied by using methylene blue as the electrochemical signal probe.The main experimental parameters were optimized in the preparation process of the aptamer sensor.The optimal experimental conditions were as follows:the incubation time of the aptamer was 2 h,the concentration of the carbon aerogels-cDNA was 5 μmol/L,and the hybridization time between the aptamer and nitrogen doped porous carbon-cDNA was 1.5 h.The electric current was reduced by 1.1 μA when incubating with 5.0×10^-6μg/mL OTA,and this signal change can be explained as follows:in the absence of OTA,MB can intercalate into single-stranded cDNA through the guanine bases and double-stranded DNA,and produce a strong current signal.In the presence of OTA,the binding of OTA and aptamer is considerably greater than that of cDNA and aptamer,which results in the release of MB from the electrode surface and reduces current signal.The linear equation was obtained in the OTA concentration range fnrm 1.0×10^-7to 5.0×10^-5μg/mL.The sensor had good reproducibility and repeatability,and acceptable stability.The rice samples were tested by the spiking method,and the average recovery was 102%.