Nanotechnology is a highly promising molecular technology which may present a variety of hazards for environmental and human health. In this study, we investigated about the cytotoxicity and the mechanisms of action of $LUDOX^{(R)}$ silica nanoparticles (commercial colloidal silica nanoparticles in aqueous phase) with three different types (different size, stabilizers, and coating materials) in human neuronal cell line. Various dosages were treated for different incubation times and measured cell viability with MTT assay. Our results show that alumina coated smaller $LUDOX^{(R)}$ CL (13.3 nm) is less toxic than $LUDOX^{(R)}$ AS-20 (16.9 nm) and AM (15.3 nm) in neuronal cells. We measured the production of intracellular reactive oxygen species (ROS) to investigate the mechanism of cell death induced by $LUDOX^{(R)}$ nanoparticles. Treatment of 48 h of silica AS-20 and AM induced the production of ROS with a dose-dependent relationship. This treatment also did induce DNA-double strand breaks. Cells exposed to alumina coated silica nanoparticle showed a less sensitive response than those exposed to uncoated silica. Nevertheless, the parameters tested were rather limited in terms of gaining a full understanding of the oxidative stress and cellular response due to exposure to silica nanoparticles. Further studies on the mechanism to more clearly elucidate the silica induced neuronal cell death, as well as on the relationship between the physico-chemical properties of nanoparticles and their cytotoxicity are warranted to gain an understanding of the phenomenon of different sensitivities of various silica nanoparticles.