Ochratoxin A nanostructured electrochemical immunosensors based on polyclonal antibodies and gold nanoparticles coupled to the antigen

Competitive electrochemical immunosensors, based on disposable screen-printed electrodes (SPCEs), have been developed for the determination of the mycotoxin ochratoxin A (OTA). Two indirect immunoassays schemes were assessed using polyclonal antibodies and through the physical adsorption of OTA conjugated to albumin from bovine serum (OTA-BSA) and newly synthesized OTA-BSA bound to gold nanoparticles (OTA-BSA-AuNPs) onto the working electrode surface. After the competition step, detection was facilitated by a secondary algG antibody labelled with alkaline phosphatase and differential-pulse voltammetry using alpha-naphtyl-phosphate as substrate. The performance of the optimized immunosensors in terms of sensitivity, reproducibility and selectivity was studied. The linear working range of the described biosensors ranged between 0.9 and 9.0 ng mL(-1) for the OTA-BSA based immunosensor and between 0.3 and 8.5 ng mL(-1) for the gold nanostructurecl immunosensor, with a limit of detection (LOD) equal to 0.86 ng mL(-1) (RSD = 10.6%) and 0.20 ng m L-1 (RSD = 8.0%) of OTA, respectively. The nanostructured immunosensor was applied to a certified wheat standard and a non-contaminated wheat material spiked with OTA, obtaining recoveries from about 104 +/- 0.07% to 107 +/- 0.08%. The influence of the wheat matrix on the analytical performance of the immunoassay was also studied.