Author/Editor		Kocbek, Petra; Teskač, Karmen; Erdani-Kreft, Mateja; Kristl, Julijana
Title		Toxicological aspects of long-term treatment of keratinocytes with ZnO and TiO2 nanoparticles
Type		članek
Source		Small
Vol. and No.		Letnik 6, št. 17
Publication year		2010
Volume		str. 1908-17
Language		eng
Abstract		Sunscreens containing ZnO and TiO(2) nanoparticles (NPs) are increasingly applied to skin over long time periods to reduce the risk of skin cancer. However, long-term toxicological studies of NPs are very sparse. The in vitro toxicity of ZnO and TiO(2) NPs on keratinocytes over short- and long-term applications is reported. The effects studied are intracellular formation of radicals, alterations in cell morphology, mitochondrial activity, and cell-cycle distribution. Cellular response depends on the type of NP, concentration, and exposure time. ZnO NPs have more pronounced adverse effects on keratinocytes than TiO(2). TiO(2) has no effect on cell viability up to 100 mug mL(-1), whereas ZnO reduces viability above 15 mug mL(-1) after short-term exposure. Prolonged exposure to ZnO NPs at 10 mug mL(-1) results in decreased mitochondrial activity, loss of normal cell morphology, and disturbances in cell-cycle distribution. From this point of view TiO(2) has no harmful effect. More nanotubular intercellular structures are observed in keratinocytes exposed to either type of NP than in untreated cells. This observation may indicate cellular transformation from normal to tumor cells due to NP treatment. Transmission electron microscopy images show NPs in vesicles within the cell cytoplasm, particularly in early and late endosomes and amphisomes. Contrary to insoluble TiO(2), partially soluble ZnO stimulates generation of reactive oxygen species to swamp the cell redox defense system thus initiating the death processes, seen also in cell-cycle distribution and fluorescence imaging. Long-term exposure to NPs has adverse effects on human keratinocytes in vitro, which indicates a potential health risk.
Descriptors		KERATINOCYTES ZINC OXIDE TITANIUM MICROCHEMISTRY TIME FACTORS MICROSCOPY, ELECTRON MITOCHONDRIA CELL DIVISION ENDOSOMES