Biocompatibility of core@shell particles: cytotoxicity and genotoxicity in human osteosarcoma cells of colloidal silica spheres coated with crystalline or amorphous zirconia.

The cytotoxicity and genotoxicity of novel colloidal silica spheres coated with crystalline or amorphous zirconia (SiO2@ZrO2(cryst) or SiO2@ZrO2(am)) have been studied in a human osteosarcoma cell line (MG-63), after 24 h exposure. SiO2@ZrO2(cryst) and SiO2@ZrO2(am) had mean diameters of 782±19 and 891±34 nm, respectively. SiO2@ZrO2(cryst) exposure reduced cell viability, with an increase in reactive oxygen species (ROS) and a decrease of the GSH/GSSG ratio. The comet and micronucleus (MN) assays detected DNA damage at 5 and 25 μg/mL, respectively. SiO2@ZrO2(am) induced genotoxic action only at 10 and 50 μg/mL (comet and MN assays), along with a decrease of the GSH/GSSG ratio at 50 μg/mL. Both particles were found inside the cells, forming vesicles; however, none of them entered the nucleus. Our findings show that crystallization of the shell of the amorphous ZrO2 increases both cytotoxicity and genotoxicity.