Studying the effects of silica nanoparticles on cells

A. M. MEBERT; D. MAYSINGER; M. F. DESIMONE; P. EVELSON

Workshop; Workshop Redox mechanisms in pathophysiology; 2018

Silica is widely believed to be an important material for biomedical and drug deliveryapplications. Using synthetic techniques, silica nanoparticles (SiNPs) can be produced withspecific physical and chemical properties and with precise size control. They are currentlybeing used in cosmetics, foods, paints, and in other industrial applications. Human exposure tonanosilica can occur unintentionally in daily life and in industrial settings. With the aim ofstudying its interaction with the human body, different kinds of surface-grafted (bare -OH,amino -NH 2 and thiol -SH) SiNPs were synthesized by a typical Stöber method. This methodwas selected because of its simplicity and known chemistry. For this work, non-porousmonodisperse silica nanoparticles around 50 nm in size were synthesized. To evaluate thecytotoxicity of these NPs, MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide) assays were performed, from which we estimated the viable cell count. Thetetrazolium reduction to formazan by the cells? active metabolism is measured and ispresumed to be directly proportional to the number of viable cells. To support this assumption,a live cell count was performed by Hoechst staining in lung (A549) cells. Fluorescentrhodamine-labeled silica nanoparticles were synthesized to determine nanoparticleinternalization after cell exposure. Cores loaded with rhodamine B were synthesized andcapped with an extra silica layer, to prevent leakage. The shells were later modified withamino groups or thiol groups to obtain the three particle charge types. Size, dispersity andsurface were studied by scattering electron microscopy (SEM); the hydrodynamic diameterswere determined by field flow fraction and dynamic light scattering (FFF/DLS); the surface-grafting was verified by fourier-transform infrared spectroscopy (FT-IR). Results show noevidence of cytotoxicity at the tested concentration and time, up to 30 ppm by the 72 hourmark. Using rhodamine-labeled SiNPs, it was determined that NPs grafted with positivelycharged groups achieved internalization more easily.