An Assay of DNA by Resonance Light Scattering Technique and its Application in Screening Anticancer Drugs

In this contribution, a novel assay has been developed to detect the interaction between DNA and drugs using ethidium bromide (EB) as a probe based on the decreased resonance light scattering (RLS) technique. It was found that, in pH 2.0 Britton-Robinson buffer solution, EB underwent dramatic enhancement of RLS signal when binding to DNA. Additionally, the strong RLS signal of the EB-DNA system was remarkably decreased after the addition of DNA-targeted anticancer drugs. The results showed a linear relationship between the enhanced RLS intensity of the EB-DNA system and concentration of DNA in the range of 0.015-40.8 μg mL -1. The linear regression equation is represented as follows: ΔI RLS = 4.15 + 21.14c with regression coefficient r = 0.9970 (n = 10). The detection limit was 0.3 ng mL -1. Only 2.0 × 10 -8 mol L -1 was selected as the optimum EB concentration in this assay. Further study demonstrated that the anticancer efficacy of anticancer drugs varied inversely with RLS intensity of the EB-DNA-drug system. So, it is intuitive to see the sequence of antitumor efficiency of anticancer drugs without data processing by RLS screening spectra. Compared with the traditional cell-based screening methods, the proposed method was more convenient, rapid and intuitive. The reaction mechanism is discussed. © 2012 The Royal Society of Chemistry.