Interaction of Spherical Silica Nanoparticleswith Neuronal Cells: Size-DependentToxicity and Perturbation of Calcium Homeostasis

The effects of Stöber silica nanoparticles on neuronal survival, proliferation, and on the underlying perturbations in calcium homeostasis are investigated on the welldifferentiated neuronal cell line GT1-7. The responses to nanoparticles 50 and 200 nm in diameter are compared. The 50-nm silica affects neuronal survival/proliferation in a dose-dependent way, by stimulating apoptotic processes. In contrast, 200-nm silica does not show any toxic effects even at relatively high concentrations (292 μ g mL − 1 ). To identify the mechanisms underlying these effects, the changes in intracellular calcium concentration elicited by acute and chronic administration of the two silica nanoparticles are analyzed. The 50-nm silica nanoparticles at toxic concentrations generate huge and long-lasting increases in intracellular calcium, whereas 200-nm silica only induces transient signals of much lower amplitude. These fi ndings provide the fi rst evidence that silica nanoparticles can induce toxic effects on neuronal cells in a size-dependent way, and that these effects are related to the degree of perturbation of calcium homeostasis.