Bimetallic Metal−Organic framework nanorods with peroxidase mimicking activity for selective colorimetric detection of Salmonella typhimurium in food

Foodborne disease caused by pathogenic bacteria remains a great threat to public health throughout the world. Herein, a colorimetric assay was developed for rapid and selective detection of Salmonella typhimurium (S. typhimurium) based on Fe/4Cu-metal organic framework nanorods (Fe/4Cu-MOF). The Fe/4Cu-MOF exhibited peroxidase mimicking activity which can catalyze oxidizing 3,3′,5,5′-tetramethylbenzidine (TMB) to generate a visible blue color The negative charged S. typhimurium-specific aptamers were anchored onto the surface of Fe/4Cu-MOF, acting as both the catalysis enhancers of Fe/4Cu-MOF and the specific recognition elements of S. typhimurium. In the presence of S. typhimurium, aptamers bound to S. typhimurium specifically, leading to the decline of catalytic activity. Under the optimized conditions, the catalytic activity of Fe/4Cu-MOF decreased in proportion to the concentration of S. typhimurium with a linear range of 3.6 × 102-3.6 × 107 CFU/mL and the detection limit of 1.0 × 102 CFU/mL. The colorimetric assay was applied to the determination of S. typhimurium in chicken and beef with spiked recoveries of 98.3%–104% and 96.1%–102%, respectively. The assay exhibits advantages of convenience, rapidness (∼35 min), good selectivity and low cost. Moreover, such a catalysis-based strategy can be extended to other analytes by replacing target-specific aptamers, providing a universal candidate for rapid analysis.