On the toxicity of lipid and metal oxide nanoparticles of pharmaceutical and cosmetic interest

Lipid, TiO2, and ZnO nanoparticle toxicological profiles have been studied in vitro and in vivo. Their cytotoxicity and genotoxicity have been investigated on A549 cells using trypan blu and the comet assay, respectively. Acute toxicity and teratogenicity were assessed in chicken embryos using two different experimental setups. In the short-term (48 hours), somite number and morphology were evaluated while in the long-term (12 days), bone morphology and morphometry were assessed after whole-mount staining for bone and cartilage. Lipid nanoparticles were not genotoxic while TiO2 nanoparticles demonstrated a moderate dose-dependant genotoxicity and ZnO nanoparticles were highly genotoxic with (highest dose) higher DNA damages than the positive control, 4-nitroquinoline 1-oxide. On the contrary, in vivo experiments did not corroborate genotoxicity data. In fact, somite numbers were not statistically different (p<0.005) from the untreated group and no somite malformation was observed. Embryos treated with retinoic acid, the positive control, were characterized by a lower number of somites (p<0.001) and malformations (i.e., somite fusion, open neural chanel) in about 50% of embryos. In long-term experiments, no differences (p<0.005) in bone morphology and morphometry were recorded for embryos treated with nanoparticles with respect to the negative control. In conclusion, lipid nanoparticles showed an encouraging toxicity profile both in vitro and in vivo. Metal oxide nanoparticle in vitro genotoxicity was not paralleled to teratogenicity in vivo. The importance of these results resides on the fact that many warnings on nanoparticle toxicity rose only from in vitro evidences.