"Molecular Velcro": Design of coupled AuNPs with streptavidin-biotin immobilized nanobody in lateral flow immunoassay for sensitive Salmonella typhimurium detection

Abstract

The synthesis of nanoparticle-nanobody (Nb) conjugates exhibiting high stability and affinity remains challenging in the development of lateral flow immunoassay (LFIA). Herein, we utilized the streptavidin-biotin system as a “Molecular Velcro” to enhance the bioactivity of nanogold-Nb probes through oriented conjugation of biotinylated nanobodies with streptavidin-coated gold nanoparticles. The Au/SA@Bio-Nb probe presented higher stability and affinity. On this basis, an improved LFIA was established for rapid and sensitive detection of S. typhimurium in food. The visual detection limit of the Au/SA@Bio-Nb-LFIA is 10³ CFU mL⁻¹, and the linear detection range is 10³–10⁷ CFU mL⁻¹. In addition, the recovery rate of the portable immunosensor for detecting S. typhimurium in food samples is 81.23 %–105.01 %. Overall, this study provides great promise for the design and preparation of Nb-based probes to enhance the detection performance of LFIA methods.