A novel lateral flow assay for lead ion detection based on G-quadruplex

Lead ion residues pose potential health risks to humans. To develop a cost-effective and user-friendly portable lead ion detection method, a novel lateral flow test strip was designed and fabricated based on the G-quadruplex structure. Initially, G4 and its complementary strand antiG4 are in a double-stranded form in the assay solution. After adding lead ions, these ions compete with antiG4 to bind to G4 and form G-quadruplex structures, thus releasing a large number of antiG4 single strands. Through base pairing, one end of the antiG4 was linked to a recognition element containing gold nanoparticles, while the other end was captured by a test line probe, resulting in a red band on the test line. The color change of the test line was positively correlated with the concentration of lead ions. Results showed that by observing the color change of the test line under optimized experimental conditions, lead ion concentration could be detected with a visual detection limit of 20 nM. Quantitative analysis using ImageJ software indicated that the test strip had a linear detection range of 10–2000 nM, with a detection limit of 7.32 nM and significant specificity. The recovery rate in bottled drinking water ranged from 91.19 % to 126.04 %, providing a portable and simple new method for on-site detection of residual lead ions in water environments.