Detection of Specific DNA Sequence with a Non-labeled Molecular Beacon and a Nucleic Acid Dye Hoechst 33258

A highly sensitive and selective method for specific DNA sequence detection is developed using a non. labeled molecular beacon (MB) and a nucleic acid dye Hoechst 33258. It is demonstrated by a specific DNA sequence of wild. type HBV as a model system. In this strategy, the stem of MB is completely designed as C/G base pairs. In the absence of target DNA, the interaction between Hoechst 33258 and the MBs is very weak, and the fluorescence signals of Hoechst 33258 is very low. In the presence of target DNA, the MBs hybridize with the target DNA and form double. stranded structure. Hoechst 33258 binds to dsDNA, and the fluorescence intensity is significantly enhanced. Under the optimum conditions, the fluorescence intensity of Hoechst 33258 exhibits good linear dependence on target DNA concentration in the range of 2 x 10(-10) -2 x 10(-8) mol/L. The fitted regression equation is. Delta I = 3. 3439C(10(-10) mol/L) + 18. 6949(R-2 = 0. 9982) with a correlation coefficient of 0. 9982 (R-2), and the detection limit is 9 x 10(-11) mol/L (3 sigma). The proposed method has good precision, simple operation, fast detection speed, low detection limit, high accuracy and high sensitivity.