Gold nanoparticles-based colorimetric assay of pesticides: A critical study on aptamer’s role and another alternative sensor array strategy

Pesticide residue is an important problem in environmental pollution, and colorimetric methods are suitable for on-site fast assay of pesticides. Analytes-triggered aptamer desorption from gold nanoparticles (AuNPs) has been widely used to develop label-free colorimetric assays. But the direct interactions between pesticides and AuNPs have not been considered previously, leading to one possible misinterpretation of analysis results. In this work, we studied the direct adsorption of pesticides on AuNPs, and further performed a comprehensive analysis of aptamer’s role. Here the colorimetric response was independent on DNA sequences, and a similar aggregation of AuNPs was shown for all the tested DNA sequences. Our study demonstrated a misinterpretation in the previous assays, while pesticides adsorption by AuNPs was the main mechanism for these colorimetric assays. Finally, we designed another alternative sensor array based on different parameters (pH, ionic strength and [DNA]) for accurate discrimination of four pesticides including acetamiprid, carbendazim, pymetrozine and thiabendazole. Due to the different functional groups in these four pesticides, the fingerprints of AuNPs’ colorimetric responses allow intuitively identifying different pesticides for environmental or food application.