Study on the Interaction between Quinine Sulfate and DNA by Multiple Spectral Methods and Their Analytical Applications

The interaction of quinine sulfate (QS) and DNA has been investigated by spectra methods including fluorescence spectroscopy and resonance light scattering (RLS) technique in aqueous solutions. The QS showed an obvious decrease of fluorescence intensity upon the addition of trace amounts of DNA, and the quenching mechanism was suggested to be static quenching according to the Stern–Volmer equation. Under the acidic condition of pH 2.5, the quenched fluorescence intensity of the QS–DNA system was linearly dependent on the concentration of ctDNA ranging from 0.02 to 2.5 mg/L. The interaction between QS and DNA as well as the detection of DNA was further confirmed by RLS technique, and the results showed that enhanced RLS intensity was linearly related to the concentration of ctDNA from 0.01 to 3.5 mg/L. Therefore, two spectral methods for the detection of ctDNA have been established with the use of a QS small molecular probe.