Toxicity of Metal Oxide Nanoparticles: Mechanisms, Characterization, and Avoiding Experimental Artefacts

Abstract

Metal oxide nanomaterials are widely used in practical applications and represent a class of nanomaterials with the highest global annual production. Many of those, such as TiO2 and ZnO, are generally considered non-toxic due to the lack of toxicity of the bulk material. However, these materials typically exhibit toxicity to bacteria and fungi, and there have been emerging concerns about their ecotoxicity effects. The understanding of the toxicity mechanisms is incomplete, with different studies often reporting contradictory results. The relationship between the material properties and toxicity appears to be complex and diifficult to understand, which is partly due to incomplete characterization of the nanomaterial, and possibly due to experimental artefacts in the characterization of the nanomaterial and/or its interactions with living organisms. This review discusses the comprehensive characterization of metal oxide nanomaterials and the mechanisms of their toxicity.

Dual UV irradiation-based metal oxide nanoparticles for enhanced antimicrobial activity in <em>Escherichia coli</em> and M13 bacteriophage

“…36 The surface topologies and electrostatic properties are considered as critical factors when monitoring antimicrobial activities of MO nanoparticles with and without dual UV irradiation based on biomembrane adsorption and ROS generation. 28,35,37,38 The nanocrystalline structures of MO nanoparticles ( Figure 4) were matched with PXRD and FE-SEM results. In terms of electrostatic characteristics, MO nanoparticles function as photocatalysts that lead to antimicrobial activities 10,22 based on ROS generation by the electronic curvatures in reciprocal space of the conduction band minimum and valence band maximum, and dispersions of electron-hole effective masses.…”

“…8,28 MO nanoparticles generally have a highly crystalline structure, uniform particle shape, nanoscale size, and large surface area with mesopores for chemical and biological adsorption. 7,10 These properties were dependent on the synthesis techniques (e.g., sol-gel processing 11 and thermal evaporation 29 ) and the conditions which affect MO nanocrystal growth.…”

Comparative phytotoxicity of undoped and Er-doped ZnO nanoparticles onLemna minor L.: changes in plant physiological responses

“…Although there is no clear evidence showing damage due to the low discharge levels of nanomaterials, it is well recognized that there is a gap in our understanding of the behavior and fate of nanomaterials in the environment (Djurišić et al, 2015). Therefore, their potential hazards to biological systems and their interactions with organisms should be understood.…”

Nanotoxicology of Metal Oxide Nanoparticles

“…Nanoparticles themselves can interfere with many tests, and it is often necessary to adapt the protocol to obtain reliable results [134,135]. A standardization of toxicity protocols, long-term study of nanoparticle toxicity and the fate of these nanomaterials in human tissue and in the environment need to be further investigated.…”