Highly sensitive and rapid determination of Escherichia coli O157:H7 in minced beef and water using electrocatalytic gold nanoparticle tags

A simple, highly sensitive and specific immunosensing assay for rapid detection and quantification of Escherichia coli O157:H7 in meat and water samples based on the electrocatalytic properties of gold nanoparticles (AuNPs) towards hydrogen evolution reaction and superparamagnetic microbeads (MBs) as pre-concentration/purification platforms without the need of broth enrichment is developed for the first time. Minced beef and water samples inoculated with different concentrations of E. coli O157:H7 have been tested using anti-E. coli O157-magnetic beads conjugate (MBs-pECAb) as a capture platform and sandwiching afterwards with AuNPs modified with secondary antibodies (AuNPs-sECAb) and detected using chronoamperometric measurement with screen-printed carbon electrodes (SPCEs). Detection limits (LOD) of 148, 457 and 309 CFU/mL were obtained in buffer solution, minced beef and tap water samples respectively, with a broad detection range of 102-105 CFU/mL in all cases. Recoveries percentages after spiking of 5 different samples of both minced beef and tap water with 103 and 104 CFU/mL were 94.7 and 90.4 (in beef) and 91.3 and 94.8% (in water), respectively. Specificity, reproducibility and comparison with a commercial lateral flow kit in terms of LOD and detection range were also studied showing clear advantages of the electrochemical method performance. The successful application of this AuNPs based technology in minced beef and tap water indicates the possibility of its using in various food items and other water resources.