On-site colorimetric detection of Salmonella typhimurium

Rapid qualitative and quantitative detection of Salmonella typhimurium (S. typhimurium) takes an important role in ensuring food safety. Herein, a colorimetric assay aptasensor for S. typhimurium utilizing intrinsic peroxidase-like activity of gold nanoparticles embedded spherical covalent organic framework and the affinity and specificity of S. typhimurium-aptamer has been explored. This aptasensor can capture the S. typhimurium via the selective binding effect of aptamer, and the catalytically active sites were shielded. As a result, the colorimetric signals of the 3,3 ',5,5 '-tetramethylbenzidine-H2O2 system were turned off. Under optimum conditions, the aptasensor gave a linear response over the range of 10 to 10(7) CFU/mL for S. typhimurium. The detection limit of 7 CFU/mL was obtained within 45 min and was effectively applied to detect S. typhimurium in milk and lake water samples with recoveries in the range from 96.4 to 101.0%. More importantly, combined with a self-developed smartphone-based image analysis system, the proposed aptasensor can be used for point-of-care testing applications.

Automated summary

A colorimetric assay aptasensor for the detection of Salmonella typhimurium was developed using gold nanoparticles embedded spherical covalent organic framework with peroxidase-like activity and the affinity and specificity of S. typhimurium-aptamer. The aptasensor showed a low detection limit and good recovery rates, and can be combined with a smartphone-based image analysis system for point-of-care testing.