Visual diagnostic of Helicobacter pylori based on a cascade amplification of PCR and G-quadruplex DNAzyme as a color label.

Helicobacter pylori is a spiral-shaped, Gram-negative, microaerophilic and fastidious bacterium. It is the main cause of chronic gastritis as well as gastric and duodenal ulcers. The diagnosis of H. pylori infection is significant for the selection of therapy and for the follow up of eradication success. A simple and robust strategy based on the cascade of PCR and DNAzyme catalyzed reaction was utilized to detect H. pylori. The design of the primer pair would enable PCR to synthesize aptamer of DNAzyme at the 3' end of PCR products. G-quadruplex DNAzyme as a color label can exhibit peroxidase-like activity to amplify the specific signal and demonstrate a colorimetric signal to indicate the diagnostic result. This assay can detect genomic DNA of H. pylori specifically with as low as 100 pg/reaction by the naked eye. This is a powerful demonstration of G-quadruplex DNAzyme to be used for PCR-based assay with significant advantages of high sensitivity, low cost and simple manipulation over existing approaches and offers the potential opportunity for clinical application.