Fluorescence enhancement effect for the determination of DNA with calcein-cetyl trimethyl ammonium bromide system

A new spectrofluorimetric method was developed for the determination of trace amounts of DNA using the calcein as a fluorescent probe. In the presence of appropriate amounts of the cationic surfactant cetyl trimethyl ammonium bromide (CTAB), the anionic dye calcein dimerizes. The weak fluorescence intensity of the dimer was enhanced by adding DNA at pH 6-7. The interaction between calcein-CTAB and DNA was studied on the basis of this behavior and a new method was developed for determining DNA. Under the optimal conditions, the enhanced fluorescence intensity was in proportion to the concentration of DNA in the range of 4.0x10(-6) to 8.0x10(-5) g L(-1) for fsDNA and thermally denatured ctDNA (4.5x10(-6) to 9.0x10(-5) g L(-1)). The detection limits (S/N=3) were 2.0x10(-6) and 2.2x10(-6) g L(-1), respectively. This method was used for determining the concentration of DNA in synthetic samples with satisfactory results.