文摘
An optical and rapid sandwich immunoassay of Salmonella pullorum and Salmonella gallinarum (S. pullorum and S. gallinarum) was designed using anti-S. pullorum and S. gallinarum antibody-functionalized blue silica nanoparticles (IgG-Blue-SiNPs) and magnetic nanoparticles (IgG-MNPs) as immunosensing probes in this article. The IgG-MNPs were used for enrichment of S. pullorum and S. gallinarum, IgG-Blue-SiNPs were used for signal amplification. The Blue-SiNPs were synthesized by doping C.I. reactive blue 14 into silica nanoparticles using an inverse microemulsion method. The morphology, surface charge and functional groups of Blue-SiNps were characterized by SEM, Zeta potential and FTIR spectroscopy. S. pullorum and S. gallinarum in sample solution was captured, enriched and separated by IgG-MNPs. Then IgG-Blue-SiNps were added into the above mixture solution, S. pullorum and S. gallinarum was sandwiched by IgG-MNPs and IgG-Blue-SiNps, forming a blue plaque. Under optimal conditions, the detection limit for pure S. pullorum and S. gallinarum was from 8.8 × 101. The detection limit for S. pullorum and S. gallinarum in milk powder was 8.8 × 102 CFU/ml. Besides, this qualitative detection method was economic, simple, rapid, specific and good stability. Such a simple optical sandwich immunoassay holds great potential as an on-site tool for clinical diagnosis of bacteria and viruses.