Surface plasmon resonance immunoassay for ochratoxin a based on nanogold hollow balls with dendritic surface

A surface plasmon resonance (SPR)-immunosensor based on nano-size gold hollow ball (GHB) with dendritic surface has been developed for detection of Ochratoxin A (OTA). A thionine thin film was initially electropolymerized onto the SPR-probe surface, and then anti-OTA monoclonal antibody (anti-OTA) was immobilized onto the SPR-probe surface by means of GHB conjugation. The binding of target molecules onto the immobilized antibodies causes an increase in the resonant angle of the sensor chip, and the resonant angle shift was proportional to the OTA concentration in the range of 0.05-7.5 ng/ml with a detection limit of 0.01 ng/ml at a signal/noise ration of 3. A glycine-HCl solution (pH 2.8) was used to release antigen-antibody complexes from the biorecognition surface. Good reusability was exhibited. Moreover, spiking various levels of OTA into three milk samples was assayed using the proposed immunoassay. Analytical results show the precision of the developed immunoassay is acceptable. Compared with the conventional enzyme-linked immunosorbent assay, the proposed immunoassay system was simple and rapid without multiple labeling and separation steps. Importantly, the proposed immunoassay system could be further developed for the immobilization of other antigens or biocompounds.