Calcium phosphate hydroxyapatite (HA) is widely used as bone substitute. Its chemical composition is close to the mineral part of bone which induces osteoconductive ceramics. Silicated hydroxyapatites (SiHA) are being studied. The incorporation of silicon in the hydroxyapatite structure would increase the bioactivity of the implant. However, these substitutes are not osteoinductive. They do not have the ability to induce bone formation which limits their use in reparative surgery. In order to obtain osteoinductive ceramics, it is possible to functionalize their surface by biologically active molecules via organosilanes. The present work studies the influence of silicon incorporation in the hydroxyapatite structure and the functionality (i.e. number of hydrolysable groups) of amino-ethoxy-silanes on the grafting mode and the quantity of molecules at the substrates surface. HA and SiHA silanised ceramics have been produced and characterized by means of X-ray photoelectron spectroscopy and thermogravimetric analysis coupled with mass spectrometry. The results confirmed the covalent grafting whatever the nature of the substrate and the functionality of the organosilane might be. The grafted amount increases with the functionality of organosilane. Moreover, the presence of silicon within the substrate promotes the number of ethoxyl chains involved in the heterocondensation reaction and decreases the grafted amount of organosilanes. The organosilanes are not homogeneously distributed on the surface but without formation of a layer covering the entire surface.
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