Study On The Electrochemical Immunosensor For The Detection Of Ochratoxin A

In recent years, food safety issues resulted from biotoxin contamination have attracted much attention due to the increasing occurrence of food safety problems. Ochratoxin A is one kind of highly toxic compound threatening kidney and liver, could be detected in agriculture products, such as cereals, legumes, and vegetable oils. In order to ensure food safety, the development of a rapid and sensitive method is highly desired for the determination of OTA.A novel ultrasensitive, signal amplified electrochemical immunosensor based on Poly(amidoamine) dendrimer was developed. PAMAM dendrimer could provide numerous amino groups to allow highly dense immobilization of antibody, so that the electrochemical reponses could be improved. The composite material G4-PAMAM dendrimer encapsulated Au nanoparticles were also synthesized. The composite material could increase conductivity because of the excellent conductivity and biocompatibility of Au nanoparticles. The working principle was based on direct competition towards immobilized antibody between tested OTA and HRP labeled OTA. After an immunoassay process, the HRP on the electrode serface reduced H2O2 in the presence of enzymatically oxidized thionine and then electrocatalytic responses were produced, which were inversely proportional to the concentration of OTA. Under the optimal conditions, this immunosensor showed a good linearity denpendency upon the concentration of OTA in the range from 1.0 × 10-3 to 100 μgL-1 with a detection limit of 6.9 × 10-5μg-L-1(S/N=3).Recoveries of OTA in corn and grape juice samples under three concentrations [2.5、 5、10 μg-kg-1 (L-1)] were 81.2%-94.3%. The results obtained from immunosensor showed a correlation coefficient of 0.9926 with those obtained ria HPLC analysis. All the results indicated that the established method in this work provided a effective, rapid and stable method for trace analysis and detection of OTA in foods.