High-sensitive flow-based kinetic exclusion assay for okadaic acid assessment in shellfish samples

Episodes of shellfish contamination with okadaic acid (OA) are a human health threat that is causing increasing concern. As a way to overcome the shortcomings involved in the reference methods of analysis set by legislations, alternative procedures are envisaged. This paper describes the development of different immunosensors for the analysis of OA, focusing on the comparison of their sensitivity, precision, ease of use and sample matrix effects. Initially, a surface plasmon resonance (SPR)-based immunosensor was developed, which enabled the quantification of the toxin in mussel samples at concentrations in the range of the 160 μg kg^-1 European regulatory limit with good percentages of recovery. Nevertheless, calibration curves with spiked mussel samples showed that matrix effects could not be neglected. Alternatively, a flow-immunosensing system based on kinetic exclusion measurements was developed achieving the theoretical lowest limit of detection enabled by the affinity of the anti-OA antibody (IC₇₀ = 0.03 μg L^-1 in the assay solution). This highly sensitive automated system allows rapid and reliable OA quantification, with no significant matrix effects for the analysis of spiked mussel and scallop samples. Performance features such as high sensitivity and precision, low limits of detection and simplicity of the analysis protocol, shows the biosensing-systems based on kinetic exclusion measurements for toxin detection in shellfish samples as highly performing tools for rapid and continuous screening.