Abstract : The development of bone tissue regeneration calls for biomaterials able to release biologically active substances in a controlled manner afterimplantation. In this context, mesoporous calcium phosphates are of major interest. In this work, hydroxyapatite powders with an interconnected nanoporosity were prepared. Their ability to incorporate and to release proteins was tested with the use of cytochrome C. Adsorption isotherm in solution was obtained by titration of the supernatant by UV absorption and showed a fast adsorption capacity, while the desorption experiments showed a prolonged release capability of thebiomaterial. To determine the spatial distribution of the proteins at the biointerface of the porous ceramic, an original methodology was developed. Highly sensitive Particles Induced X-ray Emission coupled to Rutherford Backscattering Spectroscopy (PIXE-RBS) was used to obtain quantitative chemical mappings of hydroxyapatite powders at the micrometer scale. Iron naturally presents in cytochrome C was used as their marker. Quantitative chemical maps of Ca, P and Fe show concentrations gradients of proteins from the centre to the periphery of the materials. In the tested hydroxyapatite, the proteins incorporation start at 10 μm from the powder surface and the majority of proteins is located in the centre. Thanks to this method we are able to determine quantitatively the proteins distribution in the bioceramics. In our case, the behaviour of proteins at the biointerface give very good outlooks for the controlled release of specific protein in the body for future experiments.