In Vitro Comparative Skin Irritation Induced by Nano and Non-Nano Zinc Oxide

Abstract

This study was designed to determine whether nano-sized ZnO has the potential to cause acute cutaneous irritation using cultured HaCaT keratinocytes and a human skin equivalent as in vitro models, compared to non-nanomaterials. Commercial nano ZnO with different sizes (50 nm and 100 nm) was characterized by dynamic light scattering (DLS) and microscopy (SEM) in different media. Nano ZnO reduced the cell viability of HaCaT in a dose-dependent and time-dependent manner, in a similar way to macro ZnO. However, the 3D-epidermis model revealed no irritation at 1 mg/mL after 24 h of exposure. In conclusion, nano-sized ZnO does not irritate skin, in a similar manner to non-nano ZnO.

Keywords: 3D-epidermal model; cytotoxicity; keratinocytes; skin irritation; zinc oxide.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1

Transmission electron microscopy (TEM) images of ZnO 50 nm (a) and 100 nm (b) in distilled water, phosphate buffered saline (PBS) and Dulbecco’s modified Eagle medium (DMEM) cell culture medium, respectively.

Figure 2

Cell viability of HaCaT cells exposed to different concentrations of ZnO (a) and ZnO 50 (b) and 100 nm (c), respectively, after 24, 48 and 72 h incubation. Mean values ± standard deviation of triplicates of at least three independent experiments. ap < 0.05, bp < 0.01 and cp < 0.001 compared to controls.

Figure 3

IC50 values calculated from the curves of cell viability of HaCaT cells exposed to ZnO and ZnO 50 and 100 nm after 24, 48 and 72 h incubation. Mean values ± standard deviation of triplicates of at least three independent experiments.

Figure 4

Images of HaCaT cell by phase contrast microscopy. Control cells without treatment (a), cells treated for 24 h with 25 µg/mL of ZnO (b), ZnO 50 nm (c) and ZnO 100 nm (d).

Figure 5

Episkin histological images. Tissues were processed for paraffin sections and stained with hematoxylin and eosin stain for histological examination. Normal control group treated with PBS (a), ZnO non-nanometric (b), ZnO 50 nm (c) and ZnO 100 nm (d).