Enhancement of the peroxidase-like activity of aptamers modified gold nanoclusters by bacteria for colorimetric detection of Salmonella typhimurium.

A colorimetric aptasensor was developed for selective and sensitive detection of Salmonella typhimurium (S. typhimurium) based on the enhancement of bacteria for the peroxidase-like activity of dual aptamers modified bovine serum albumin stabilized-gold nanoclusters (aptamers@BSA-AuNCs). Micro-sized bacteria was found to be able to capture aptamers@BSA-AuNCs and 3,3',5,5'-tetramethylbenzidine (TMB), thus promoting the proximity of aptamers@BSA-AuNCs to TMB and greatly increasing the local concentrations of the enzyme-mimetic nanoparticles and their substrate. As a result, addition of bacteria promoted the formation of blue products in the catalytic system, which was utilized to achieve bacteria detection by colorimetry. The parameters influencing the colorimetric aptasensor were optimized by an orthogonal test. Under the selected conditions, the aptasensor exhibited a wide linear response to S. typhimurium in the concentration range of 101-106 cfu mL-1 with a detection limit as low as 1 cfu mL-1. The feasibility of the aptasensor was verified by successful detection of S. typhimurium in egg samples with recoveries in the range of 92.4%-110%.