Gold decorated polystyrene particles for lateral flow immunodetection of Escherichia coli O157:H7

Conventional lateral flow immunoassays for pathogen detection usually make use of gold nanoparticles to impart the color necessary for a readout. Unfortunately, these immunoassays require an extra-long time enrichment process before the detection. The synthesis of gold-decorated polystyrene particles (Au-PS), and their incorporation in a lateral flow immunoassay (LFIA) with improved sensitivity for detection of the model pathogen Escherichia coli O157:H7 (E. coli O157:H7) were described in this article. The synthesis of the Au-PS particles occurred through the citrate reduction method. Then the particles underwent surface modification through coating with branched polyethylenimine, followed by grafting of the anti-E. coli O157:H7 antibody. The effect of Au-PS particle size and of the surface coverage on the detection limit of the assay was investigated. The Au-PS particles with 0.46 mu m PS and 10% Au surface coverage achieved 500 CFU.mL(-1) limit of detection (LOD) for E. coli O157:H7 in apple juice, ground beef, and spiked buffer solutions. Furthermore, these particles achieved 100 CFU.mL(-1) LOD when the secondary a signal amplification reaction via gold reduction method was used. While the antibody-antigen interaction has a well-known role in detection, a precise optimization of the Au-PS particles used in LFIA assays can significantly affect performance. In our perception, Au nanoparticles coverage on sub-micron sized polystyrene particles was the critical factor that allowed reaching the reported low concentration of E. coli O157:H7 in real food samples.