Oxidative stress induced by reactive oxygen species (ROS) is one of the most important antibacterial mechanisms of engineered nanoparticles (NPs). To elucidate the ROS-generation mechanisms, we investigated the electronic structure (i.e., the band gaps, valence and conduction band positions) on the ROS production kinetics of selected metallic nanoparticles including metals and metal oxides under room light and UV irradiation (365 nm). The results show that different metal oxides had distinct photogenerated ROS kinetics under the same environmental conditions. Particularly, TiO2 nanoparticles and ZnO nanoparticles generated three types of ROS (superoxide radical, hydroxyl radical, and singlet oxygen), whereas other metal oxides generated only one or two types or did not generate any type of ROS. Similar observations were achieved for metal NPs (e.g., AgNPs, AuNPs, NiNPs). The ROS-generation was found to be influenced by the electronic structures of semiconductor-type NPs such as metal oxides and SiNPs as shown in Figure 1 , whereas the ROS generation on metal NPs was more likely affected by surface plasmon resonance (SPR). Lastly, a linear relationship between oxidative stress (expressed as the average ROS concentration) and the viability of E. coli cells was established (R2=0.84) as shown in Figure 2  . This relation will facilitate the quantitative evaluation of oxidative stress and toxic potential of engineered nanomaterials. Overall, the reported findings lay the groundwork for unraveling the ROS photogeneration mechanisms and antibacterial activities of metallic NPs.

Effects of electronic structures of metallic nanoparticles on photogeneration of reactive oxygen species and antibacterial activity

247th National Meeting (2014)

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