A simple QD-FRET bioprobe for sensitive and specific detection of hepatitis B virus DNA.

We report here a simple quantum dot-FRET (QD-FRET) bioprobe based on fluorescence resonance energy transfer (FRET) for the sensitive and specific detection of hepatitis B virus DNA (HBV DNA). The proposed one-pot HBV DNA detection method is very simple, rapid and convenient due to the elimination of the washing and separation steps. In this study, the water-soluble CdSe/ZnS QDs were prepared by replacing the trioctylphosphine oxide on the surface of QDs with mercaptoacetic acid (MAA). Subsequently, DNA was attached to QDs surface to form the functional QD-DNA bioconjugates by simple surface ligand exchange. After adding 6-carboxy-X-rhodamine (ROX)-modified HBV DNA (ROX-DNA) into the QD-DNA bioconjugates solution, DNA hybridization between QD-DNA bioconjugates and ROX-DNA was formed. The resulting hybridization brought the ROX fluorophore, the acceptor, and the QDs, the donor, into proximity, leading to energy transfer from QDs to ROX. When ROX-DNA was displaced by the unlabeled HBV DNA, the efficiency of FRET was dramatically decreased. Based on the changes of both fluorescence intensities of QDs and ROX, HBV DNA could be detected with high sensitivity and specificity. Under the optimized conditions, the linear range of HBV DNA determination was 2.5 - 30 nmol L(-1), with a correlation coefficient (R) of 0.9929 and a limit of detection (3σ black) of 1.5 nmol L(-1). The relative standard deviation (R.S.D.) for 12 nmol L(-1) HBV DNA was 0.9% (n = 5). There was no interference to non-complementary DNA. Time-resolved fluorescence spectra and fluorescence images were performed to verify the validity of this method and the results were satisfying.