Immunoassay utilizing imaging surface plasmon resonance for the detection of cyclopiazonic acid (CPA) in maize and cheese.

α-Cyclopiazonic acid (CPA) is a tremorgenic mycotoxin produced by Aspergillus and Penicillium fungal species, commonly found on agricultural commodities or fermented food products. A sensitive and rapid imaging surface plasmon resonance (iSPR) assay was developed to detect CPA in maize and cheese by combining an indirect competitive immunoassay and signal amplification based upon a secondary antibody (Ab2) conjugated with gold nanoparticles. Matrix-matched calibration curves were used to determine CPA content in maize and cheese samples. Recoveries, at two spiking levels in maize and cheese, were 89 to 126%, with standard deviations of repeatability (RSDr) of less than 16%. The limits of detection were 17 and 6 μg/kg in maize and cheese, respectively. To separate the CPA-contaminated samples from uncontaminated samples, a cutoff validation level of 40 μg/kg was introduced. The assay was applied to samples of naturally contaminated maize and was compared with competitive inhibition enzyme-linked immunosorbent assay (CI-ELISA). This is the first report to detect CPA using an immuno-biosensor iSPR format.