The effect of blood protein adsorption on cellular uptake of anatase TiO2 nanoparticles

Protein adsorption onto nanoparticles (NPs) in biological fluids has emerged as an important factor when testing biological responses to NPs, as this may influence both uptake and subsequent toxicity. The aim of the present study was to quantify the adsorption of proteins onto TiO2 NPs and to test the influence on cellular uptake. The surface composition of the particles was characterized by thermal analysis and by X-ray photoelectron spectroscopy. The adsorption of three blood proteins, ie, human serum albumin (HSA), γ-globulins (Glbs), and fibrinogen (Fib), onto three types of anatase NPs of different sizes was quantified for each protein. The concentration of the adsorbed protein was measured by ultraviolet-visible spectrophotometry using the Bradford method. The degree of cellular uptake was quantified by inductivity coupled plasma mass spectroscopy, and visualized by an ultra-high resolution imaging system. The proteins were adsorbed onto all of the anatase NPs. The quantity adsorbed increased with time and was higher for the smaller particles. Fib and Glbs showed the highest affinity to TiO2 NPs, while the lowest was seen for HSA. The adsorption of proteins affected the surface charge and the hydrodynamic diameter of the NPs in cell culture medium. The degree of particle uptake was highest in protein-free medium and in the presence HSA, followed by culture medium supplemented with Glbs, and lowest in the presence of Fib. The results indicate that the uptake of anatase NPs by fibroblasts is influenced by the identity of the adsorbed protein

Contact-dependent transfer of TiO₂ nanoparticles between mammalian cells

<p>Cellular organelles have been shown to shuttle between cells in co-culture. We hereby show that titanium dioxide (TiO₂) nanoparticles (NPs) can be transferred in such a manner, between cells in direct contact, along with endosomes and lysosomes. A co-culture system was employed for this purpose and the NP transfer was observed in mammalian cells including normal rat kidney (NRK) and HeLa cells. We found that the small GTPase Arf6 facilitates the intercellular transfer of smaller NPs and agglomerates. Spherical, anatase nano-TiO₂ with sizes of 5 (Ti5) and 40 nm (Ti40) were used in this study. Humans are increasingly exposed to TiO₂ NPs from external sources such as constituents of foods, cosmetics, and pharmaceuticals, or from internal sources represented by Ti-based implants, which release NPs upon abrasion. Exposure to 5 mg/l of Ti5 and Ti40 for 24 h did not affect cellular viability but modified their ability to communicate with surrounding cells. Altogether, our results have important implications for the design of nanomedicines, drug delivery and toxicity.</p