Abstract
•Our studies of apatite–etidronic acid hybrid compounds highlight the influence of apatitic surface in grafting process.•We showed that the apatitic surface possesses two different functional groups CaOH and POH acting as the active sites.•Synthesizing CaHAp-(ETD) composites offers a relevant tool as possible application as biomaterials to repair bone tissues.
The surface of prepared calcium hydroxyapatite CaHAp has been modified by grafting the etidronic acid (ETD). For that purpose, CaHAp powders have been suspended in an aqueous etidronate solution with different concentrations. The obtained composites CaHAp-(ETD) were characterized by TEM and AFM techniques to determinate morphological properties and were also characterized by XRD, IR, NMR and chemical and thermal analysis to determinate their physico-chemical properties and essentially the nature of the interaction between the inorganic support and the grafted organic ETD. After reaction with ETD, XRD powder analysis shows that the apatitic structure remains unchanged with slight affectation of its crystallinity. The presence of etidronate fragment bounded to hydroxyapatite was confirmed by IR and solid-state NMR spectroscopy. TEM and AFM techniques indicate that the presence of etidronate changes the morphology of the particles. Basing on the obtained results, a reactional mechanism was proposed to explain the formation of covalent CaOPorg bonds on the hydroxyapatite surface between the superficial hydroxyl groups (CaOH) of the apatite and phosphonate group (POH) of etidronate.