Gold nanoparticle-based strip sensor for multiple detection of twelve Salmonella strains with a genus-specific lipopolysaccharide antibody

Abstract

In this study, an innovative competitive im-munochromatographic strip sensor was developed for rapid detection of Salmonella based on a genus-specific anti-lipopolysaccharide (LPS) monoclonal antibody (mAb) and the heterogeneous coating antigen of a LPS-bovine serum albumin conjugate. Gold nanoparticles labeled anti-LPS mAb specifically reacted with the conserved outer core of the Salmonella LPS in the sample and the color formed on the T line was negatively correlated with the number of Salmonella cells. The sensitivity of Ra mutant LPS (without O-specific chains but has the conserved outer core) was 25 ng mL –1 , which explained the detection of Salmonella at the genus level. Based on the gray values on the test line, the limit of detection of Salmonella was 10 3 colony-form-ing unit (CFU) for all twelve typical strains of Salmonella. The analysis of common Gram-negative and Gram-positive bacteria demonstrated that the strip assay was specific to Salmonella. A milk sample test showed that Salmonella at a low level (1–5 CFU mL –1) was detected without complex biochemical confirmation steps, sophisticated instruments and professional training.