Detection of Shiga-like Toxin Produced by E. coli O157:H7 based on the LSPR Property of Gold Nanoparticles

Shiga-like toxin-producing E. coli (STEC) was first introduced as a human pathogen in 1982. STEC serotypes were isolated from animals, foods, and other samples. This serotype is the leading cause of single and epidemic Hemorrhagic colitis and Haemolytic uremic syndrome. STEC serotype produces two potent toxins named Shiga-like toxin 1 and 2, whose genomes are encoded by phage. These toxins have a cytopathic effect on intestinal epithelial cells that cause bloody diarrhea. This study aimed to design and evaluate a nanobiosensor based on the LSPR (Local Surface Plasmon Resonance) property of citrated gold nanoparticles (GNP), by modifying the pH of the GNP environment and conjugation (non-covalent bonding) of GNP with rabbit anti- Shiga-like toxin polyclonal antibody (IgG). In this process, the binding of gold nanoparticles to antibodies and the detection of Shiga-like toxin were confirmed using UV-visible and DLS methods and the sensitivity and specificity of the produced nanobioprobe were evaluated using the ELISA method. The results showed that the sensitivity of this method in detecting Shiga-like toxin is about 10 ng/ml and the visible color-changing of the nanoprobe suspension was confirmed for all vials containing the target antigen in less than 1 h. In conclusion, the advantage of the produced nanobioprobe over other methods is the detection of small quantities of analytes, low cost, and detection in less than 2 h.