Polydopamine nanoparticle-mediated, click chemistry triggered, microparticle-counting immunosensor for the sensitive detection of ochratoxin A

A rapid and accurate detection method is needed for the quantitation of ochratoxin A in agricultural products due to its high toxicity. A microparticle-counting immunosensor based on polydopamine nanoparticle-mediated click chemistry was established for the highly-sensitive detection of ochratoxin A. Polydopamine nanoparticles with good biocompatibility and a strong metal-chelating ability were synthesized and conjugated with the antibody. The Coupled compounds were then used as an immune carrier to change the Cu 2+ concentration via an immuno-reaction. Some of the remaining Cu 2+ ions were reduced to Cu + ions, which caused azide-polystyrene microspheres and alkyne-polystyrene microspheres to aggregate via a Cu + ion-mediated click reaction. Particle counting was used to distinguish changes in the sizes of the polystyrene microspheres from dispersed to aggregated to detect ochratoxin A. It showed a wide linear detection range of 0.5–800 ng/mL, and a detection limit of 0.2 ng/mL. This assay provides an attractive analytical tool for the accurate detection of trace targets in complex samples. • Polydopamine nanoparticle can excellently couple antibodies and chelate Cu 2+ ions. • Click ligand-modified polystyrene microparticles are efficient signal probes. • Microparticle-counting immunosensor is an enzyme-free sensor to detect ochratoxin A.