Effect of polyethylene glycol modification of TiO ₂ nanoparticles on cytotoxicity and gene expressions in human cell lines

Nanoparticles (NPs) are tiny materials used in a wide range of industrial and medical applications. Titanium dioxide (TiO ₂) is a type of nanoparticle that is widely used in paints, pigments, and cosmetics; however, little is known about the impact of TiO ₂ on human health and the environment. Therefore, considerable research has focused on characterizing the potential toxicity of nanoparticles such as TiO ₂ and on understanding the mechanism of TiO ₂ NP-induced nanotoxicity through the evaluation of biomarkers. Uncoated TiO ₂ NPs tend to aggregate in aqueous media, and these aggregates decrease cell viability and induce expression of stress-related genes, such as those encoding interleukin-6 (IL-6) and heat shock protein 70B' (HSP70B'), indicating that TiO ₂ NPs induce inflammatory and heat shock responses. In order to reduce their toxicity, we conjugated TiO ₂ NPs with polyethylene glycol (PEG) to eliminate aggregation. Our findings indicate that modifying TiO ₂ NPs with PEG reduces their cytotoxicity and reduces the induction of stress-related genes. Our results also suggest that TiO ₂ NP-induced effects on cytotoxicity and gene expression vary depending upon the cell type and surface modification.