Competitive binding assay for G-quadruplex DNA and sanguinarine based on room temperature phosphorescence of Mn-doped ZnS quantum dots

•Mn-doped ZnS quantum dots have been synthesized and characterized.•Sensor system for investigating binding ability of DNA with drug was developed.•Interactions of six G-quadruplex DNA and sanguinarine were comparatively probed.•Conformational changes of the G-quadruplex DNA induced by drug were evaluated.•Binding mechanism of G-quadruplex DNA with the drug was explored and discussed.

sG-quadruplex DNA is an effective target for anticancer drug, and investigation of the G-quadruplex DNA with natural compounds plays a key role in the development of anticancer drugs.In this article, room temperature phosphorescence sensing system based on l-cysteine-capped Mn-doped ZnS QDs has been established. Sanguinarine can adsorb on the surface of Mn-doped QDs and quenched the phosphorescence emission of the sensor. When the G-quadruplex sequences combined with the sanguinarine of the QDs-sanguinarine system, the phosphorescence intensities of the QDs sensors would be restored, and the binding abilities of the G-quadruplex DNA with the sanguinarine can be evaluated by the phosphorescence recoveries of the sensor system. Based on the developed approach, the interaction of sanguinarine and six G-quadruplex DNA with various sequences (tel24-1, tel24-2, tel22, k-ras, HIF-1α and c-kit1) has been investigated. The results showed that the binding abilities of the G-quadruplex DNA with sanguinarine were related to their number of bases and conformations. The conformational changes of the six G-quadruplex DNA, after binding with sanguinarine, have also been probed by circular dichroism. Combining the changes of the phosphorescence lifetime, the binding mechanism of the G-quadruplex DNA and sanguinarine has been discussed. The developed method was simple, rapid and specific, and can avoid fluorescence interferences of the system, and it would be prospective to evaluate the interaction of the drug with different G-quadruplexes.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide