Photometric sandwich immunoassay for Salmonella pullorum and Salmonella gallinarum using horseradish peroxidase and magnetic silica nanoparticles

The article describes a sensitive and rapid method for the colorimetric determination of Salmonella pullorum and Salmonella gallinarum (S. pullorum and S. gallinarum). Silica coated magnetic nanoparticles (MNP) were modified with antibodies against S. pullorum and S. gallinarum to act as the capture probes. Horseradish peroxidase (HRP) and antibodies against S. pullorum and S. gallinarum on silica nanoparticles (HRP-IgG-SiNP) were used as detection probes (secondary antibody). In the presence of S. pullorum and S. gallinarum, the target bacteria are captured by capture probes and detection probes to form sandwich structures. This sandwich complexes were then magnetically isolated and used to catalytically oxidize the chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB). The absorbance at 450 nm is proportional to the concentration of S. pullorum and S. gallinarum. Under the optimized conditions, the assay has a detection range that extends from from 8.4 x 10(3) to 8.4 x 10(7) CFUai...mL(-1), and the limit of detection is 1.7 x 10(3) CFUai...mL(-1). The approach is cost-effective and specific. Sample preconcentration is not required. In our perception, this immunomagnetic nanoparticle-based detection strategy holds great promise for on-site detection of a wide range of pathogens by using the respective antibodies.