Rapid Visual Detection of Salmonella typhimurium Using a Colormetric Aptamer Sensor Based on Gold Nanoparticles

An aptamer sensor (aptasensor) based on gold nanoparticles (AuNPs) was developed for the rapid visual detection of Salmonella typhimurium in foods. The aptamer specifically bound to S. typhimurium in samples to be analyzed, and a capturing probe that could adsorb onto the surface of AuNPs was released, avoiding subsequent aggregation of AuNPs induced by salts. In the absence of S. typhimurium, salts induced the aggregation of AuNPs, leading to color changes visible to the naked eye in the solution, thus allowing for the rapid and simple detection of S. typhimurium. The feasibility, detection performance, and specificity of the developed aptasensor were characterized. The aptasensor had a good response performance to S. typhimurium in the range of 10-10⁹ CFU/mL. A linear regression model equation was fitted as follows: y = -0.12998x + 1.24411 (R² = 0.99262), and the detection limit was as low as 124 CFU/mL. Four kinds of non-target bacteria were detected by this aptasensor with good specificity. Because of its high sensitivity, simple operation, rapidity and low cost, it holds great promise for rapid and in situ food safety detection.