Effects of aspect ratio (AR) and specific surface area (SSA) on cytotoxicity and phototoxicity of ZnO nanomaterials.

With growing interests in the applications of high aspect ratio (AR) ZnO nanomaterials (NMs), their potential toxicity to human health and nature environment remains a critical concern because these NMs have extremely large specific surface area (SSA) that could dramatically enhance interactions between NMs and surrounding molecules. In addition, originated to their intrinsic photocatalytical activity, ZnO NMs may induce phototoxicity under environmentally UV exposure. In this paper, ZnO spheres, grains, rods and needles with increasing AR (from 1.1 to 17.8) and various SSA (from 2.0 m(2) g(-1) to 27.4 m(2) g(-1)) were used to study the influence of AR and SSA on viabilities of WIL2-NS human lymphoblastoid cells in both dark and UV conditions. In dark, SSA was the main influencing factor for toxicity of NMs with low AR (spheres, grains and rods) and smaller SSA leads to higher cell viability. However, ZnO needles with the smallest SSA did not further enhance cell viability which may be possibly attributed to its high AR. Cell viability measured under UV irradiation did not show evident relationship with SSA or AR, but indicated that lower photocatalytic activity could mitigate phototoxicity.