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.

Potassium complexes supported by monoanionic tetradentate amino-phenolate ligands: synthesis, structure and catalysis in the ring-opening polymerization of rac-lactide.

A series of potassium complexes bearing monoanionic tetradentate amino-phenolate ligands, [LK]2 (L = {(2-R1)C6H4CH2N[(CH2)2R2]CH2(4-R4-6-R3)C6H2O-}, R1 = NMe2, R2 = NEt2, R3 = CPh3, R4 = Me (1); R1 = R2 = NEt2, R3 = CPh3, R4 = Me (2); R1 = NMe2, R2 = NEt2, R3 = R4 = cumyl (4); R1 = R2 = OMe, R3 = tBu, R4 = Me (6); L = (2-NMe2)C6H4CH2N[[CH2-(S)-1-butylpyrrolidinyl]CH2(4-Me-6-CPh3)C6H2O-] (3)), have been synthesized via reactions of KN(SiMe3)2 and 1 equiv. of the corresponding aminophenols. The solid-state structures of typical complexes 4 and 6 are determined via X-ray diffraction studies, which reveal the dinuclear nature of these complexes. By contrast, DOSY measurements of 1, 4 and 6 suggest that these complexes are monomeric in solution. It is noteworthy that the coordination chemistry of these potassium complexes is versatile, which is closely related to the nature of the ortho-substituent of the phenolate ring, as indicated by the results of the corresponding spectroscopic studies. In the presence of iPrOH, 1-4 and 6 could initiate the polymerization of 500 equiv. of rac-lactide to achieve high monomer conversions within several minutes but afford atactic PLAs with slightly isotactic-enriched microstructures (Pm = 0.58-0.60). Experimental results also demonstrated that a bulky trityl substituent at the ortho-position of the phenolate ring of the ligand framework is beneficial for the enhancement of the activities of these potassium complexes.