Graphene-labeled synthetic antigen as a novel probe for enhancing sensitivity and simplicity in lateral flow immunoassay.

Lateral flow immunoassay (LFIA), which combines immune-specific recognition properties with sensitive nano-signaling features, has emerged as an excellent tool for point-of-care testing (POCT) in food safety and clinical diagnosis. Exploring novel probes with a simple preparation process, improved signal intensity and good stability is conducive to the development and application of LFIA. Herein, a potent non-antibody probe, graphene-labeled synthetic antigen (G-Ag), was created for LFIA, in which graphene endowed a naked-eye visual colorimetric signal with high sensitivity, and the synthetic antigen competed with the target for binding to the antibody on the test line. During the G-Ag probe manufacturing process, only one simple mixing step was needed because graphene nanosheets presented a strong adsorption capacity toward the protein (BSA) on the synthetic antigen, significantly saving time, labor and cost. Especially, the synthetic antigen forms a fabulous probe element without the need for antibody, and thus the proposed LFIA avoids the destruction of antibody activity, and exhibits excellent sensitivity and stability. After optimization, LFIA was successfully applied to analyze clenbuterol; the lowest visually detectable concentration was 0.1 ng mL, and the probe could be well-applied in pork, mutton, sausage and bacon samples, demonstrating favorable specificity and repeatability. Owing to the advantages of simplicity, non-antibody probe, sensitivity and reliability, G-Ag probe-based LFIA has application potential for small-molecule target monitoring and rapid detection.