title: Surface characteristics of nanocrystalline apatites: effect of mg surface enrichment on morphology, surface hydration species, and cationic environments.
abstract: The incorporation of foreign ions, such as Mg2+, exhibiting a biological activity for bone regeneration is presently considered as a promising route for increasing the bioactivity of bone-engineering scaffolds. In this work, the morphology, structure, and surface hydration of biomimetic nanocrystalline apatites were investigated before and after surface exchange with such Mg2+ ions, by combining chemical alterations (ion exchange, H2O-D2O exchanges) and physical examinations (Fourier transform infrared spectroscopy (FTIR) and high-resolution transmission electron microscopy (HRTEM)). HRTEM data suggested that the Mg2+/Ca2+ exchange process did not affect the morphology and surface topology of the apatite nanocrystals significantly, while a new phase, likely a hydrated calcium and/or magnesium phosphate, was formed in small amount for high Mg concentrations. Near-infrared (NIR) and medium-infrared (MIR) spectroscopies indicated that the samples enriched with Mg2+ were found to retain more water at their surface than the Mg-free sample, both at the level of H2O coordinated to cations and adsorbed in the form of multilayers. Additionally, the H-bonding network in defective subsurface layers was also noticeably modified, indicating that the Mg2+/Ca2+ exchange involved was not limited to the surface. This work is intended to widen the present knowledge on Mg-enriched calcium phosphate-based bioactive materials intended for bone repair applications.
authors.affiliation: Dipartimento di Chimica IFM e NIS Center of Excellence, Universita degli studi di Torino, V. Giuria 7, 10125 Torino, Italy. luca.bertinetti@unito.it
authors.forename: Luca
authors.initials: L
authors.lastname: Bertinetti
authors.forename: Christophe
authors.initials: C
authors.lastname: Drouet
authors.forename: Christele
authors.initials: C
authors.lastname: Combes
authors.forename: Christian
authors.initials: C
authors.lastname: Rey
authors.forename: Anna
authors.initials: A
authors.lastname: Tampieri
authors.forename: Salvatore
authors.initials: S
authors.lastname: Coluccia
authors.forename: Gianmario
authors.initials: G
authors.lastname: Martra
mesh_terms: D001031:Apatites / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry*; D002413:Cations, Divalent / Q000737:chemistry; D006860:Hydrogen Bonding; D008274:Magnesium / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
chemical_list: D001031:Apatites; D002413:Cations, Divalent; D014867:Water; D008274:Magnesium; D002118:Calcium