Bioactive coatings obtained at room temperature with hydroxyapatite and polysiloxanes

Low temperature Hydroxylapatite (HA) coatings were obtained on metal substrates by depositing HA particles suspended in a ormosil polymer gel made of an equimolar mixture of amino and epoxy substituted silanes. The new coatings were analysed by thermal analysis, infrared and solid state NMR, as well as X-ray diffraction and SEM observations. Results show the HA powder conserves its characteristic physicochemical properties during the coating process. Furthermore, the coatings induce the formation of a biomimetic HA layer when soaked in simulated body fluids. This room temperature process may lead to novel calcium phosphate coatings with better control of crystallinity and porosity and with the possible incorporation of biofunctional organic molecules.