Competitive near-infrared PEC immunosorbent assay for monitoring okadaic acid based on a disposable flower-like WO-Modified screen-printed electrode.

The long-term toxic effects of okadaic acid (OA) in shellfish pose a serious threat to public health, negatively impacting the development of the shellfish aquaculture industry. In this study, a novel competitive near-infrared-mediated photoelectrochemical immunosorbent assay (cNIR-PECIA) was developed for ultrasensitive and highly selective detection of OA based on NaYF:Yb, Tm upconversion nanophosphors (UCNPs) and a flower-like WO-modified screen-printed electrode (FL-WO SPE). The UCNPs function as a self-powder to convert NIR excitation into visible emissions. FL-WO fully utilizes the visible illumination and induces the separation of electron-hole pairs, thus generating a photocurrent. After conjugating monoclonal antibodies against OA on UCNPs (UCNPs-Ab), the bright PEC immunoprobe selectively captured OA molecules, which were then determined by a competitive indirect immunosorbent assay. Under optimal conditions, the 50% inhibitory concentration of the immunosensor was 0.09 ng mL. The OA concentration had a linear relationship with the antibody binding rate in the range of 0.01-60 ng mL with an extremely low detection limit of 0.007 ng mL. Finally, the proposed cNIR-PECIA was successfully utilized to analyze OA content in mussel samples. This study affords new ideas for constructing NIR PEC sensors by using upconversion luminescent materials to match semiconductors. The superior sensing properties indicate their potential applicability in food safety analysis.