Adsorption of fibronectin on hydroxyapatite functionalized with alendronate

The purpose of this work is to evaluate how the surface modification of apatites with alendronate may affect the adsorption of proteins relevant for bone regeneration. Two different apatites were synthesized for the study. Both of the powders were obtained by co-precipitation, assisted either by mechanical or by ultrasonic stirring. Hydroxyapatite-alendronate hybrid compounds were obtained by reactive milling and the protein adsorption experiments were done by mixing 10 mg of the hydroxyapatites and hybrids powders with 1.5 mL of a 0.1 mg/mL fibronectin solution. After 24h of digestion and separation of the solid from the liquid, the protein remaining in the liquid was measured by UV/VIS Spectrometry. The formation of the hybrids has been confirmed by the shift of significant Raman bands assigned to vP-O(H) anddP-OH bands that indicates changes in the P-O bond of the alendronate due to different modes of coordination to the Ca²⁺ ion of the apatite. Hybrids materials adsorb less fibronectin than their corresponding hydroxyapatite precursors.