A PtRu nanozyme and aggregation-induced emission nanoparticle mediated novel fluorescent and colorimetric dual-mode immunoassay for xylazine detection.

Xylazine (XYL) is an α2 receptor agonist for veterinary use and has abused as an illicit adulterant of opioids. Its abuse poses serious risks including food safety events, drug-facilitated crimes, and even death. Therefore, it is necessary to establish a sensitive, accurate, and rapid method for on-site screening of XYL. In this work, we synthesized a bimetallic PtRu nanoclusters (NCs) nanozyme with high peroxidase-like activity, and an aggregation-induced emission polystyrene nanoparticles (AIE-PSNPs) with strong fluorescence emission at 590 nm. The PtRu NCs catalyze the oxidation of substrate 3,3',5,5'-tetramethylbenzidine (TMB), generating a colorimetric signal. Then resulting oxidized TMB quenches the fluorescence of the AIE-PSNPs by inner filter effect, providing a fluorescent signal output. Based on this mechanism, a novel fluorescent and colorimetric dual-mode nanozyme-linked immunosorbent assay (NLISA) was fabricated for sensitive and accurate sensing XYL. The limit of detection of the proposed dual-mode NLISA in fluorescent mode was 0.011 ng mL-1, and in colorimetric mode was 0.049 ng mL-1, with high specificity and accuracy demonstrated in both modes.