Multi-Center Catalytic Oxidation of the Sotalol Drug Adsorbed on Gold Nanoparticles

Currently, gold nanoparticles are increasingly used in targeted drug delivery nanostructures. However, their intrinsic catalytic activity is often overlooked when using them as a carrier. In this study, the interaction between the sotalol drug from the beta-blocker family and gold nanoparticles was investigated using capillary electrophoresis and high-performance liquid chromatography. Both methods showed that sotalol undergoes catalytic oxidation on the surface of citrate-stabilized gold nanoparticles into three products. Together with a cleavage of the isopropyl group from the nitrogen atom, the oxidation at the hydroxyl group occurs with the formation of a ketone. Analysis of electropherograms showed 100% conversion of sotalol after 48 h of incubation at a surface coverage of 1.2 × 10¹⁹ molecules per m². To examine the role of reactive oxygen species, the experiments were performed in oxygen-saturated and oxygen-deficient gold nanoparticle dispersions. The effects of radical scavenger additives and pH of nanoparticle dispersion were also assessed. The influence of surface ligands on sotalol conversion was studied using gold nanoparticles coated with thiols, surfactants, and polyelectrolytes. Based on comprehensive data, the mechanism of gold-nanoparticle-assisted multicenter oxidation of sotalol is proposed.