Sensitive single-color fluorescence “off–on” switch system for dsDNA detection based on quantum dots-ruthenium assembling dyads

Abstract

Due to the high importance of detecting DNA with both fast speed and high sensitivity, we proposed a new dsDNA detection method relying on a novel single-color fluorescence “off–on” switch system. Water-soluble glutathione capped CdTe QDs (emission at 605nm) was prepared for taking advantage of the readily tunable emission property of QDs. Initially, QDs was completely quenched by the Ru(phen)2(dppz)2+, as the spontaneous formation of QDs-Ru assembling dyads. Then, in the case of the addition of dsDNA, the Ru(phen)2(dppz)2+ was removed away from the CdTe QDs, producing free CdTe QDs and the Ru-dsDNA complex. Both of them could be excited at the same wavelength and emit overlaid fluorescence. This single-color fluorescence “off–on” signal was sensitive to the concentration of dsDNA. Native dsDNA with the concentration of 10pg/mL could be detected when 0.5nM CdTe QDs was used, and ssDNA, RNA or BSA had no interference on it. With this system, the dsDNA samples of hepatitis B virus (HBV) patients were tested. The results were in good agreement with those detected by fluorescence quantitative PCR (P>0.05), and for those samples with very low DNA concentrations, this system could provide more accurate results, demonstrating the possible clinical applicability of this “off–on” switch system. For this system, chemical conjugation or labeling of probes is not required, and unmodified native DNA targets could be detected in less than half an hour. Therefore, a simple, fast, sensitive, low cost, highly selective and practically applicable detection system for dsDNA has been described.