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

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 Chi 10(3) to 3 Chi 10(6) 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. (C) 2014 Elsevier B.V. All rights reserved.