Efficient Removal Performance of Purpurin from Pollutants Based on Interaction with DNA in Vitro

Abstract

This study systematically investigated the interaction characteristics between purpurin and DNA by using multiple spectroscopic techniques, with a particular focus on the interaction mode between purpurin and free DNA in vitro. Evidence obtained through UV-Vis spectroscopy, fluorescence spectroscopy, circular dichroism, fluorescence microscopy, and resonance light scattering spectroscopy showed that purpurin could form a stable purpurin–DNA complex via intercalation. A DNA thermal denaturation experiment revealed a 6.5 ℃ increase in the melting temperature (Tm) upon the addition of purpurin, indicating that purpurin enhanced the stability of the DNA double helix via intercalation. Fluorescence microscopy showed that a selective adsorption between purpurin and DNA was formed, similar to the adsorption between ethidium bromide (EB) and DNA. The DNA binding saturation value (DBSV) further confirmed the strong intercalative binding of purpurin; the DBSV value was 6.41, which was significantly higher than those of its analogues except for EB (EB: 14.70, chrysophanol: 0.53, physcion: 0.15, and alizarin: 0.19). Under optimal conditions, the purpurin removal efficiency of DNA reached 97.8%. By contrast, the purpurin removal efficiency of activated carbon was only 4.25%. Adsorption kinetics indicated that the process was identified as a spontaneous process (ΔG < 0) and followed the pseudo-second-order model (0.9929 ≤ R2 ≤ 0.9967) and the Langmuir isotherm model (0.9933 ≤ R2 ≤ 0.9965). This study provided a reference for developing a novel strategy to remove anthraquinone dyes from pollutants via intercalation with DNA in vitro, demonstrating broad application prospects.