A Biophysical Investigation of DNA-Binding Interactions of Push-Pull Dibenzodioxins and Implications for in Vitro Anti-Cancer Activity

Dibenzodioxin-DNA interactions were studied using biophysical techniques. UV-visible spectral titrations were performed against calf thymus (CT)-DNA to determine the binding constants. Spectrofluorimetric dye-displacement assay and DNA viscometric assay were used to understand the nature of binding interactions. Molecules with intercalative binding preference increased DNA viscosity, similar to a standard intercalator. Dibenzodioxin cytotoxicity was evaluated against HeLa cells. The most active molecules also had the highest binding constants with CT-DNA. Select dibenzodioxins were docked against DNA in silico. The binding behavior was compared using a known DNA binding small molecule. Dibenzodioxins with good cytotoxicity also had high DNA-binding affinity, implying that DNA could be a likely target for these dibenzodioxins. One fluorescent dibenzodioxin was used to study intra-cellular localization in HeLa cells using fluorescence microscopy. This derivative with weaker cytotoxicity was located mainly in the cytoplasm than in the nuclei, again hinting toward dibenzodioxin-DNA-binding interaction as the main mechanism of cytotoxicity.