Synthetic and natural layered silicates toxicity testing

The highly attractive properties of layered silicates has resulted in continuous expansion of these materials in a wide range of applications. However, their potential toxicological effects on human health are not fully investigated. The health concerns, regarding layered silicates, are associated with their: (i) nanoscale size, (ii) high aspect ratio resulted from their platelet geometry (thickness of about 1 nm and length and/or width of up to several microns) and (iii) chemical composition.The aim of the study was to investigate the potential hazard of a two types of layered silicates nanomaterials: synthetic layered silicate (SLS) and natural layered silicate (NLS) through in vitro toxicological studies, using mouse monocyte macrophage cell line (J774A.1) and human primary macrophages, following 24 h exposure. Different end points such as cytotoxicity, secretion of cytokines and impact of SLS and NLS particles on cell morphology was examined. This study demonstrated that both types of layered induce dose-dependent cytotoxic effect and secretion of pro-inflammatory cytokine, but the degree of induction was varying depending on the type of layered silicate. Moreover, the light microscopic, SEM and TEM examination revealed that treatment of macrophages with layered silicates caused the formation of vacuoles. These results demonstrate potential hazard on human health of SLS and NLS.