Monitoring of DNA structural changes after incorporation of the phenylpyrazole insecticide fipronil

The use of insecticides presents a risk to the environment because they can accumulate in the water, soil, air, and organisms, endangering human and animal health. It is therefore essential to investigate the effects of different groups of insecticides on individual biomacromolecules such as DNA. We studied fipronil, which belongs to the group of phenylpyrazole insecticides. The interaction of fipronil with calf thymus DNA was investigated using spectroscopic methods (absorption and fluorescence spectroscopy) complemented with infrared spectroscopy and viscosity measurement. Fluorescence emission spectroscopy showed the formation of a fipronil/DNA complex with a combined static and dynamic type of quenching. The binding constant was 4.15 × 10³ L/mol. Viscosity changes were recorded to confirm/disconfirm the intercalation mode of interaction. A slight change in DNA viscosity in the presence of fipronil was observed. The phenylpyrazole insecticide does not cause significant conformational changes in DNA structure or increase of its chain length. We hypothesize that fipronil is incorporated into the minor groove of the DNA macromolecule via hydrogen interactions as indicated by FT-IR and CD measurements.