In this study, we investigated the physicochemical and biological properties of naked and coated titania nanoparticles. The aim of this study was to verify the effect of the biopolymer coatings (hyaluronic acid and its biphosphonated derivative) and the role of protein adsorption from a cell culture medium on the citotoxicity of nanoparticles. Infrared spectroscopy (FT-IR) was used to investigate the interactions between the nanoparticles and the polysaccharides. The zeta potentials and the average hydrodynamic diameters of naked and coated nanoparticles dispersed in deionized water, medium with and without fetal bovine serum, were measured by means of dynamic light scattering (DLS). FT-IR and DLS measurements indicate that serum proteins are adsorbed on the NPs' surface. The biological tests show that naked and coated TiO2 NPs do not induce an acute toxic effect on fibroblast cell cultures. This result shows that protein adsorption on NPs is an important factor in explaining the effect of NPs on cellular behavior.