Highly Efficient Fabrication of Fluorescent “Turn-On” Lateral Flow Strips for Highly Sensitive Detection of Small Molecules Based on Self-Assembly of AuAg Nanoclusters

Currently, fluorescent "turn-on" lateral flow assay (FONLFA) has shown enhanced "naked eye" detection sensitivity for small molecules, while it is urgent to adopt biocompatible fluorescent nanomaterials and needs new strategies to simplify the preparation process. In this study, a highly effective method was proposed to produce FONLFA strips for the detection of small molecules. The gold–silver nanoclusters (AuAgNCs) were immobilized onto the nitrocellulose membrane of the strips by the self-assembly of poly(sodium 4-styrenesulfonate), antigen, and AuAgNCs. The immobilization process entails a straightforward mixing of the three components, taking merely 1 min, thereby bypassing the necessity for chemical modification of fluorescent nanomaterials. The strategy offers a significantly simplified process, which substantially enhances the efficiency of the strip fabrication. Utilizing this method, a FONLFA was developed for carbendazim with a visual limit of detection (vLOD) reduced by 40-fold compared with the conventional colorimetric lateral flow assay (LFA). Furthermore, the approach demonstrates versatility by enabling the immobilization of AuAgNCs and streptavidin, which facilitates the development of aptamer-based FONLFAs. The designed aptamer-based FONLFA for kanamycin exhibited a 50-fold reduction in the vLOD compared with conventional colorimetric LFAs. Therefore, FONLFA holds promising potential for widespread applications in the analysis of small molecules.