Electrochemical Investigation of Tartrazine and Brilliant Blue Interactions with Surface-Immobilized DNA on DES-Modified Carbon Paste Electrodes

We present a novel DNA electrochemical biosensor based on a carbon paste electrode modified with deep eutectic solvents as a binder to evaluate the interaction mechanisms between ds-DNA and the food colorants tartrazine and brilliant blue. The DES-modified CPE (CPE-DES) exhibited enhanced conductivity and charge-transfer rates for the oxidation of DNA residues, specifically the purine bases adenine and guanine, as evidenced by increased peak current values. The higher oxidation current observed for dGuo in the presence of a choline chloride-based deep eutectic solvent suggests greater exposure of the ds-DNA base moiety on the electrode surface, likely due to a stronger interaction between the choline ion and the dGuo residue. The interaction mechanisms between ds-DNA and the dyes were investigated using differential pulse voltammetry and electrochemical impedance spectroscopy. The results indicate that TZ interacts with ds-DNA primarily through groove binding, inducing conformational changes and strong DNA condensation. TheBB interacts with ds-DNA via electrostatic binding, causing the DNA helix to lengthen. For the TZ-BB mixture, the interactions likely involve both groove binding and electrostatic interaction. UV–vis and DC spectroscopy further supported these findings. Modifying CPE binders with DES demonstrates significant potential for evaluating interactions between ds-DNA and target molecules.