Oxidized silicon nanoparticles for radiosensitization of cancer and tissue cells

[Display omitted] •Uncapped (SiNPs) and aminosilanized Si nanoparticles (NH2-SiNPs) were synthesized.•SiNPs and NH2-SiNPs were internalized in tumor (MCF-7) and tissue (3T3) cells.•The SiNPs agglomerated in the cytosol, membranes and nucleus of MCF-7 and 3T3 cells.•The NH2-SiNPs provoked oxidative stress in mitochondrial membranes of MCF-7 cells.•The NH2-SiNPs were show to function as radiosensitizer for X-rays in tumor cells. The applicability of ultrasmall uncapped and aminosilanized oxidized silicon nanoparticles (SiNPs and NH2-SiNPs) as radiosensitizer was studied by internalizing these nanoparticles into human breast cancer (MCF-7) and mouse fibroblast cells (3T3) that were exposed to X-rays at a single dose of 3Gy. While SiNPs did not increase the production of reactive oxygen species (ROS) in X-ray treated cells, the NH2-SiNPs significantly enhanced the ROS formation. This is due to the amino functionality as providing positive surface charges in aqueous environment. The NH2-SiNPs were observed to penetrate into the mitochondrial membrane, wherein these nanoparticles provoked oxidative stress. The NH2-SiNPs induced mitochondrial ROS production was confirmed by the determination of an increased malondialdehyde level as representing a gauge for the extent of membrane lipid peroxidation. X-ray exposure of NH2-SiNPs incubated MCF-7 and 3T3 cells increased the ROS concentration for 180%, and 120%, respectively. Complementary cytotoxicity studies demonstrate that these silicon nanoparticles are more cytotoxic for MCF-7 than for 3T3 cells.