Dose metrics assessment for differently shaped and sized metal-based nanoparticles.

The mean primary diameter (d) of nanoparticles (NPs) is commonly used as the best basis to assess the dose metric for expressing the toxicity of spherical NPs. However, d bears no relevance for nonspherical NPs. In the present study, the mean surface area to volume ratio, applicable to both spherical and nonspherical NPs, was used to replace d given the aim of obtaining the best dose metric (volume, surface area, or number) of differently shaped metallic NPs in vivo (9 organisms) and in vitro (6 mammalian cell lines). The slope of the curves obtained by relating the total particle number of NPs at various effect concentrations to the mean surface area to volume ratio was subsequently used to deduce the best dose metric. For the majority of the organisms studied, it was found that NP volume is the most appropriate dose metric, independent of the composition of the NPs tested. For 3 organisms exposed to Ag NPs, however, surface area was found to be the best dose metric. It is therefore concluded that the optimum dose metric depends on organism and NP properties. Environ Toxicol Chem 2016;35:2466-2473. © 2016 SETAC.