Characterization of Quinacrine-Induced Structural and Antigenic Modifications in Calf Thymus DNA Using Biophysical and Immunological Techniques

Abstract

Background: Quinacrine, a heterocyclic acridine derivative, has been historically used as an antimalarial drug and is now investigated for its anticancer potential. However, its interaction with DNA raises concerns about potential carcinogenicity due to structural alterations induced in the DNA molecule.

Objective: This study aimed to investigate the structural and antigenic modifications in calf thymus DNA induced by quinacrine in a concentration- and time-dependent manner using biophysical and immunological approaches.

Methods: Calf thymus DNA was treated with quinacrine at various concentrations and incubation times. Structural alterations were characterized using ultraviolet (UV) spectroscopy, circular dichroism (CD), Fourier-transform infrared (FT-IR) spectroscopy, fluorescence emission analysis, dynamic light scattering (DLS), agarose gel electrophoresis, and electron microscopy (TEM and SEM). Antigenic changes were assessed through enzyme-linked immunosorbent assay (ELISA) and inhibition assays using New Zealand White rabbits immunized with native and quinacrine-modified DNA.

Results: UV analysis revealed significant hypochromicity at 260 nm, with 35–52% reduction in absorbance depending on quinacrine concentration and incubation time. CD spectra demonstrated altered ellipticity, suggesting disruptions in the native B-DNA conformation. FT-IR spectroscopy revealed shifts in vibrational bands indicative of perturbations in purine, pyrimidine, and phosphate backbone regions. Fluorescence analysis showed a 60% increase in intensity at 492 nm in quinacrine-modified DNA, confirming binding interactions. ELISA and inhibition assays demonstrated high specificity of induced antibodies for quinacrine-modified DNA, with differential recognition of various inhibitors.

Conclusion: Quinacrine induces significant structural modifications in DNA through intercalation and groove binding, as evidenced by spectroscopic and immunological analyses. These findings underscore the need for caution in the therapeutic use of quinacrine due to potential carcinogenic effects and offer insights into its interaction with DNA for future drug design.