Regulation of Electronic Properties of Metal Oxide Nanoparticles to Reveal Their Toxicity Mechanism and Safe-by-Design Approach.

Metal oxide (MO) nanoparticles (NPs) are widely applied to medicine, agriculture, industry, and other fields, however, their potential toxicity is often concerned. Various toxicological studies are carried out to investigate the toxicity and underlying mechanism of MO NPs. A series of physicochemical properties of MO NPs, such as primary size, charge, solubility, crystal structure, crystalline phase, etc., are correlated with their induced toxicity. Recently, electronic properties of MO NPs have exhibited intense correlation with the oxidative injury in cells and mice. The overlap between the conduction band energy (E_c) of MO NPs and the biological redox potential range (-4.12 to -4.84 eV) of biological systems shows increasing evidence in causing the oxidative injury. Charge carrier types (hole or electron) of MO NPs are further found to potentiate or alleviate these injuries. Based on this knowledge, safer MO NPs can be prepared through regulation of energy edges of MO NPs. Herein, the relationship between the electronic properties of MO NPs and their induced oxidative injury is summarized, and the new safe-by-design approach for preparing safer MO NPs is introduced. [ABSTRACT FROM AUTHOR]