Design and optimizing gold nanoparticle-cDNA nanoprobes for aptamer-based lateral flow assay: Application to rapid detection of acetamiprid.

The aptamer-based lateral flow assay strips (Apt-LFAs) have shown promising application prospects in the detection of small molecules. The general principle of Apt-LFAs used for the detection of small molecules is based on the target-induced dissociation (TID) competitive binding among the aptamer, target and gold nanoparticle (AuNP)-complementary DNA (cDNA) nanoprobes. One of the most important components in this device is AuNP-cDNA nanoprobe, which has strong effect on the sensitivity and specificity of Apt-LFAs. In this report, we designed an AuNPs@polyA-cDNA nanoprobe, which consists of a poly adenine (polyA) anchor blocker, a partial complementary DNA fragment to aptamer strand (cDNAa) and complementary DNA fragment to control DNA strand (cDNAc), for rapid detection of acetamiprid. cDNAa of AuNPs@polyA-cDNA nanoprobe was carefully investigated in terms of the hybridization site and length with the aptamer. A specific cDNAa sequence containing key binding bases of acetamiprid aptamer was obtained and verified by molecular docking analysis. After systematic optimization, the Apt-LFA was able to detect a minimum concentration of 0.33 ng mL-1 acetamiprid. The Apt-LFA was successfully applied to detect spiked acetamiprid in tomato and rape samples with the recoveries ranged from 94 to 106%. Based on the strong versatility and verified molecular interaction mechanism, the design strategy could be extended to develop various Apt-LFAs for other small molecules.