In vitro cytotoxicity of hydrothermally synthesized ZnO nanoparticles on human periodontal ligament fibroblast and mouse dermal fibroblast cells

•Zinc oxide nanoparticles can be toxic to periodontal ligament and skin fibroblasts.•ZnO NPs were characterized using AFM, BET and DLS analyses.•Cytotoxicity was evaluated using the MTT, LDH and ROS assays.•Cellular response to ZnO NPs was monitored by real-time cell impedance measurements.•ZnO NPs have high risk of cellular toxicity at 50-100 μg/mL.

The use of metal oxide nanoparticles (NPs) in industrial applications has been expanding, as a consequence, risk of human exposure increases. In this study, the potential toxic effects of zinc oxide (ZnO) NPs on human periodontal ligament fibroblast cells (hPDLFs) and on mouse dermal fibroblast cells (mDFs) were evaluated in vitro. We synthesized ZnO NPs (particle size; 7-8 nm) by the hydrothermal method. Characterization assays were performed with atomic force microscopy, Braun-Emmet-Teller analysis, and dynamic light scattering. The hPDLFs and mDFs were incubated with the NPs with concentrations of 0.1, 1, 10, 50 and 100 μg/mL for 6, 24 and 48 h. Under the control and NP-exposed conditions, we have made different types of measurements for cell viability and morphology, membrane leakage and intracellular reactive oxygen species generation. Also, we monitored cell responses to ZnO NPs using an impedance measurement system in real-time. While the morphological changes were visualized using scanning electron microscopy, the subcellular localization of NPs was investigated by transmission electron microscopy. Results indicated that ZnO NPs have significant toxic effects on both of the primary fibroblastic cells at concentrations of ∼50-100 μg/mL. The cytotoxicity of ZnO NPs on fibroblasts depended on concentration and duration of exposure.