Analytical, thermodynamical and kinetic characteristics of photoluminescence immunosensor for the determination of Ochratoxin A

Ochratoxin A (OTA) is one of the most widespread and dangerous food contaminants. Therefore, rapid, label free and precise detection of low OTA concentrations requires novel gensing elements with advanced bioanalytical properties. In the present paper we report photoluminescence (PL) based immunosensor for the detection of OTA. During the development of immunosensor photoluminescent ZnO nanorods (ZnO-NRs) were deposited on glass substrate. Then the ZnO-NRs were silanized and covalently modified by Protein-A (Glass/ ZnO-NRs/Protein-A). The latest structure was modified by antibodies against OTA (Anti-OTA) in order to form OTA-selective layer (Glass/ZnO-NRs/Protein-A/Anti-OTA). In order to improve immunosensors selectivity the surface of Glass/ZnO-NRs/Protein-A/Anti-OTA was additionally blocked by BSA. Formed Glass/ZnO-NRs/ Protein-A/BSA &Anti-OTA structures were integrated within portable fiber optic detection system, what is important for the development of low cost and portable immunosensors. The immunosensor has been tested in a wide range of OTA concentrations from 10(-4) ng/ml until 20 ng/ml. Interaction isotherms were derived from atialytical signals of immunosensor. Association constant and Gibbs free energy for the interaction of Glass/ ZnO-NRs/Protein-A/Anti-OTA with OTA were calculated, analyzed and compared with some other related results. Sensitivity range and limit of detection were determined as 0.1(-1) ng/ml and 10(-2) ng/ml, respectively. Interaction kinetics of ZnO-NRs with OTA was evaluated. Response time of the immunosensor toward OTA was in the range of 500-800 s. Some insights related to the mechanism of PL-signal generation are proposed and discussed.