A colorimetric assay method for invA gene of Salmonella using DNAzyme probe self-assembled gold nanoparticles as single tag

•This work provided a novel and simple colorimetric sensing strategy for Salmonella detection.•DNAzyme probes self-assembled gold nanoparticles were used for signal amplification effectively.•The color change of target DNA could be easily observed by naked eye.•This method was successfully applied to detect Salmonella sample in water.

A simple colorimetric sensing method was developed for detection of invA gene of Salmonella by combining DNAzyme probe self-assembled gold nanoparticles and polymerase chain reaction (PCR) technique. Amino-modified capture probe was covalently immobilized on the surface of DNA–BIND plate, and further hybridized with target sequence and DNAzyme probe self-assembled gold nanoparticles to form a sandwich-type hybridization structure. In the presence of hemin, the DNAzyme probe could form a G-quadruplex/hemin complex, which catalyzed the H2O2-mediated oxidation of 3,3′,5,5′-tetramethylbenzidine dihydrochloride hydrate (TMB) to cause a dramatic color change. The invA gene was isolated from Salmonella and amplified using a polymerase chain reaction technique, and signal was further enhanced by DNAzyme probe self-assembled gold nanoparticles. Under optimal conditions, the absorbance value was linear with the logarithm of target sequence concentrations in the range of 0.5–50 nM, with a limit of detection of 0.44 nM for target sequence. In addition, the designed method allowed the quantitative Salmonella detection in water from 3 × 103 to 3 × 106 CFU mL−1. This strategy exhibited good stability, sensitivity and simplicity and might be a potential tool for the practical Salmonella detection in clinical diagnosis, food safety and environmental monitoring.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide