Colorimetric Detection System for Salmonella typhimurium Based on Peroxidase-Like Activity of Magnetic Nanoparticles with DNA Aptamers

Recently, much attention has been devoted to food-related health issues. In particular, food-poisoning bacteria are becoming a serious threat to human health. So far, techniques used to detect these bacteria are time-consuming and laborious. To overcome these challenges, a biosensor with a simple platform was developed to detect Salmonella typhimurium. The colorimetric strategy is attractive because it enables simple and rapid sensing with the naked eyes. We used magnetic nanoparticles (MNPs), specific aptamers, and a colorimetric substrate, 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2. Because MNPs display enzyme-like activities, they can undergo color changes with the help of a colorimetric substrate. In this system, MNPs were first incubated with aptamers that specifically interact with the Salmonella species, reducing the peroxidase activity of the MNPs via DNA-mediated shielding of catalytic activity. After the addition of Salmonella cells to the solution, specific aptamers on the MNPs interact with the Salmonella, consequently enhancing the peroxidase activity of the MNPs. Considering their low cost, easy separation, and stable activity, MNPs could be applied to various detection systems.