We present a facile method for the preparation of quantum dots(QDs)-DNA nanoprobe.Firstly,histidine-capped QDs were prepared as described previously [1,2].Due to the weak binding of histidine and QDs,sulfhydryl modified DNA(5-SH-AAT TGA ATA AGC TGG TAT-3,SH-DNA)was mixed with histidine-capped QDs and bound with QDs efficiently.The binding was then monitored by capillary electrophoresis coupled with fluorescence detection(CE-FL)and agarose gel electrophoresis(Fig.1).CE-FL results indicated the migration time(tm)of free QDs was 415 s(Fig.1A,curve a).At a DNA/QD molar ratio of 25:1,a new peak emerged at 480 s(Fig.1A,curve b),which suggested that the QDs began to bind with DNA.When the molar ratio reached 50:1,almost no QDs were found and all DNA molecules were self-assembled with QDs(Fig.1A,curve c).Additionally,agarose gel electrophoresis further indicated the efficient binding between QDs and HS-DNA(Fig.1B).By functionalizing QDs with SH-DNA,the QDs-based DNA probe could be easily extended to the disease diagnose and drug delivery in the future.