Quantum dots modified molecular beacons as fluorescent DNA sensors with different acceptors

A DNA biosensor system based on fluorescence resonance energy transfer (FRET) of CdTe quantum dots (QDs) as energy donors modified molecular beacons was presented in this paper when organic dyes, 4-(4´-(dimethylamino) phenylazo) benzoic acid (DABCYL) or black hole quencher 1 (BHQ1), as energy acceptors. CdTe QDs with 3 nm in diameters were prepared in water and were linked to molecular beacons (MB) when 1-ethyl-3-(3-dimethylaminopr opyl) carbodi-imide hydrochloride (EDC) was existed. Compared with the fluorescence spectrum of CdTe QDs, the fluorescence intensity of MB decreased extremely, which indicated that the FRET occurred between CdTe QDs and quenchers, and BHQ1 as quencher had a higher FRET efficiency than that of DABCYL. The results indicated that this kind of molecular beacon has a good specificity to distinguish complementary DNA and mutant.