Assembling ″Balloon-String″ Colorimetric Probes through Click Chemistry and Hybridization Chain Reaction for Dual-Signal Amplification in Aptamer-Based Lateral Flow Assays

As a simple and visually assessable point-of-care testing method, lateral flow assays (LFAs) are widely used for detecting procymidone in vegetable samples. Meanwhile, an increasing number of aptamer-based LFAs are being developed for rapid detection. However, the sensitivity of conventional gold nanoparticles (AuNPs) aptamer-based LFAs is limited, which is a challenge to meet the detection requirements. This study proposed a dual amplification strategy of click chemistry and hybridization chain reaction (HCR) to construct a colorimetric probe to enhance the sensitivity. The nucleic acid nanostructure (HCR-ALK) constructed by HCR was used as a programming template to guide the click chemical reaction to induce the cross-linking of AuNPs-N₃ and HCR-ALK to form a uniform and stable ″ballon-string″ colorimetric probe (HCR-AuNPs). This strategy achieved dual-signal amplification. Under optimal conditions, the limit of detection (LOD) of this LFA was 5.4 × 10^–2 ng/mL. Compared with the conventional AuNPs aptamer-based LFAs, its LOD had been improved by 13.69-fold, and its color display time had been reduced to one-tenth. In specificity and stability experiments, this LFA showed a satisfactory performance. Moreover, it was successfully applied to the detection of procymidone in vegetable samples, with a recovery rate maintained between 93.44%–104.00%. Thus, this study provides a signal amplification strategy to address the issue of insufficient sensitivity in aptamer-based LFAs. This will offer new insights for the development of aptamer-based LFAs.