In order to effectively exploit the remarkable properties of fine particles to form hybrid nanostructured composites with applications in the biomedical area, one essential step is their surface functionalization. The overall objective of the present work was to use supercritical carbon dioxide (scCO(2)) for the design of the surface of inorganic particles by depositing thin and ultrathin films. Two scCO(2) routes were proposed to modify the surface of micro- (SiO2, 5 mu m) and nanometric (TiO2, 20-30 nm) oxide particles: antisolvent methods for polymers that are non-soluble in CO2 (polymethylmethacrylate), and the use of compressed CO2 as a solvent for modifiers with certain solubility in scCO(2) (octadecylsilane, salicylic acid). In the antisolvent technique, solid particles were dispersed in a solution containing the polymerand mixed with scCO(2); polymer precipitation, induced by the presence of CO2, occurred preferentially onto the available surface offered by the oxide particles. For CO2-soluble modifiers, the molecules were transferred from the compressed phase to the surface of the solid particles by diffusion; reactivity between adequate moieties permitted to form covalently grafted films. Vibrational ATR-FTIR spectroscopy was used to evaluate potential interactions between samples components. The wettability of the produced systems was analyzed by dispersion experiments in water and toluene. (C) 2010 Elsevier B.V. All rights reserved.