Multi-residue detection of pesticides using a sensitive immunochip assay based on nanogold enhancement

- A colorimetric immunochip assay for simultaneous detection of seven pesticides.
- Nanogold was adopted for signal enhancement in the competitive immunoassay.
- The sensitivity was comparable to that of enzyme-labeled monoplex immunoassay.

This paper describes the development of a new multiplex immunoassay for simultaneous detection of seven pesticides (triazophos, methyl-parathion, fenpropathrin, carbofuran, thiacloprid, chlorothalonil, and carbendazim). Sixteen pairs of pesticide antibodies and antigens were screened for reactivity and cross-reaction. A microarray chip consisting of seven antigens immobilized on a nitrocellulose membrane was then constructed. Nanogold was employed for labeling and signal amplification to obtain a sensitive colorimetric immunoassay. The direct and indirect detection formats were further compared using primary antibody-gold and secondary antibody-gold conjugates as tracers. An integrated 7-plex immunochip assay based on the indirect model was established and optimized. The detection limits for the pesticides were 0.02-6.45 ng mL−1, which meets detection requirements for pesticide residues. Naked-eye assessment showed the visual detection limits of the assay ranged from 1 to 100 ng mL−1. Spiked recovery results demonstrated that the immunochip assay had potential for multi-analysis of pesticide residues in vegetables and fruits. The proposed microarray methodology is a flexible and versatile tool, which can be applied to other competitive multiplex immunoassays for small molecular compounds.