Synthesis of quantum dot encoded multicolour nanobeads for the ultrasensitive and multiplex immunochromatographic detection of neonicotinoid insecticides

In this study, a novel fluorescent immunochromatographic assay (ICA) strip based on quantum dot encoded multicolour nanobead (QB) was developed to detect three neonicotinoid insecticides in the vegetable samples simultaneously. The results showed that three QBs with red-, yellow- and green-emitting were successfully synthesized by embedding different ratios of two kinds of hydrophobic CdSe/ZnS QDs (λ em = 565 nm and λ em = 620 nm) into the polymer matrix. The obtained three QBs were further used to label the monoclonal antibodies (mAbs) specific to imidacloprid (IMI), clothianidin (CLT) and thiamethoxam (TMX). The resultant QB@mAbs nanoprobes, including QB red @IMI mAbs, QB yellow @CLT mAbs and QB green @TMX mAbs, presented excellent monodispersity with distinguishable emission colours. Furthermore, the fabricated QB-ICA strip based on QB@mAbs nanoprobes achieved a more sensitive simultaneous detection for three neonicotinoids with the detection limits of 14.58 ng/mL for IMI, 0.27 ng/mL for CLT, and 0.36 ng/mL for TMX, respectively. This was better than most of the conventional based enzyme-linked immunosorbent assay (ELISA). Moreover, the QB-based ICA strips also exhibited good stability and specificity for the multiplex detection of IMI, CLT, and TMX. In the spiked Chinese cabbage samples, the recovery of IMI, CLT, and TMX ranged from 72.08% to 98.70%, with RSD values ranging from 3.60% to 13.09%. In brief, the great performance of the developed QB-ICA approach demonstrates its potential for simultaneous and quantitative neonicotinoids detection in agricultural products. • The mAbs specific to IMI, CLT and TMX were labelled by quantum dot encoded multicolour nanobead (QB). • Three QB@mAbs were used to fabricate the QB-ICA system for the detection of IMI, CLT and TMX. • The QB-ICA strip has a high sensitivity for IMI, CLT and TMX detection with a LOD of 14.58, 0.27 and 0.36 ng/mL. • This work achieves the simultaneous detection of three neonicotinoids via ICA.