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

Abstract

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.

Keywords:

• nanoparticles
• titanium dioxide
• proteins
• adsorption
• cellular uptake

Acknowledgments

The authors would like to thank the University of Bergen, the Grieg Foundation, and the Meltzer Research Fund for financial support. A special thanks to Tore Skodvin for DLS and electrophoretic mobility measurements and to Miguel A. Cauqui for the surface characterization of the particles.

Disclosure

The authors declare that they alone are responsible for the content and writing of this paper. The authors report no conflicts of interest in this work.