Revealing the oxidative stress mechanism induced by defect engineering of magnesium oxide nanoparticles under dark conditions

Abstract

The spread of drug-resistant bacteria poses a serious threat to public health. Nano-sized MgO exhibits excellent biocompatibility, low toxicity, and broad-spectrum antibacterial effects. Its ability to generate reactive oxygen species (ROS) even in dark conditions makes it a promising antibacterial material. However, its production of ROS is limited, and the mechanism of ROS generation under dark conditions is not yet clear, which restricts its practical application. To address this challenge, we have developed a metal-doped MgO nanomaterial with enhanced ROS generation capability. The use of spray drying simplifies the preparation of the nanoparticles, while high-temperature calcination can facilitate the effective substitution of external metal ions into the MgO crystal lattice. Doping with foreign metals do not compromise the inherent biocompatibility of MgO. A key aspect is that differences in ionic radius and charge among the doped metal ions induce the detachment of oxygen molecules from the MgO surface and cause lattice distortions, resulting in additional surface oxygen vacancies. The increased concentration of surface oxygen vacancies enhances electron transfer on the material’s surface, thereby promoting the generation of ROS. By doping with Li of similar radius but lower valence state to induce lattice defects, LiMgO (0.4 mg/mL) can inactivate more than 99.99 % of Escherichia coli (E. coli) with a concentration of 10⁸ cfu/mL within 15 min through the physical contact and oxidation mechanism of ROS. The strong antibacterial performance observed in dark environments suggests that MgO has broad application prospects as an antibacterial agent.