Enoxacin-Tb complex as an environmentally friendly fluorescence probe for DNA and its application

The fluorescence intensity of the enoxacin (ENX)-Tb³⁺ complex enhanced by DNA was studied. On the basis of this study, an environmentally friendly fluorescence probe of enoxacin-Tb³⁺ for the determination of single-stranded and double-stranded DNA was developed. Under the optimal conditions, the enhanced fluorescence intensity was in proportion to the concentration of DNA in the range of 2.0 × 10⁻⁸ to 2.0 × 10⁻⁶ g mL⁻¹ for hsDNA, 1.0 × 10⁻⁸ to 1.0 × 10⁻⁶ g mL⁻¹ for ctDNA and 5.0 × 10⁻⁹ to 1.0 × 10⁻⁶ g mL⁻¹ for thermally denatured ctDNA. The detection limits (S/N = 3) were 5.0, 9.0 and 3.0 ng mL⁻¹, respectively. The interaction modes between ENX-Tb³⁺ and DNA and the mechanism of the fluorescence enhancement were also discussed in details. The experimental results from UV absorption spectra, fluorescence spectra and the competing combination tests between the ENX-Tb³⁺ complex and EB probe indicated that the possible interaction modes between enoxacin-Tb³⁺ complex and DNA had at least two different binding modes: the electrostatic binding and the intercalation binding. Additionally, this fluorescence probe was used to study the interaction between heavy metals and DNA.