title: Revisiting silicate substituted hydroxyapatite by solid-state NMR.
abstract: Silicon-substituted hydroxyapatite (Si-HAp) has shown promising properties such as high-bone remodeling around implants. So far, the techniques used for the structural characterization of the Si-HAp have given indirect evidence of the presence of silicon inside the structure (by X-ray and neutron diffraction). In this paper, we focus on Si-HAp derivatives obtained by a precipitation method (widely described in the literature). We demonstrate here by solid-state NMR spectroscopy that only a fraction of the silicon atoms are incorporated into the HAp lattice in the form of Q(0) (SiO(4) (4-)) species, for 4.6 wt% Si-HAp. A large amount of silicate units are located outside the HAp structure and correspond to silica-gel units. All results were established through (29)Si MAS, (1)H -->(29)Si CP MAS and T(1)rho((1)H) edited (1)H -->(29)Si CP MAS experiments. This last pulse scheme acted as a powerful editing sequence, leading to unambiguous spectroscopic conclusions, concerning the location of the SiO(4) (4-) moieties.
authors.affiliation: Université Pierre et Marie Curie-Paris6, UMR 7574 CNRS, Laboratoire de Chimie de la Matière Condensée de Paris, Paris, F-75005, France.
authors.forename: G
authors.initials: G
authors.lastname: Gasquères
authors.forename: C
authors.initials: C
authors.lastname: Bonhomme
authors.forename: J
authors.initials: J
authors.lastname: Maquet
authors.forename: F
authors.initials: F
authors.lastname: Babonneau
authors.forename: S
authors.initials: S
authors.lastname: Hayakawa
authors.forename: T
authors.initials: T
authors.lastname: Kanaya
authors.forename: A
authors.initials: A
authors.lastname: Osaka
mesh_terms: D017886:Durapatite / Q000737:chemistry*; D007554:Isotopes; D009682:Magnetic Resonance Spectroscopy / Q000379:methods* / Q000592:standards; D008958:Models, Molecular; D033362:Powder Diffraction; D011522:Protons; D012015:Reference Standards; D017640:Silicates / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry; D013055:Spectrophotometry, Infrared / Q000379:methods
chemical_list: D007554:Isotopes; D011522:Protons; D017640:Silicates; D017886:Durapatite; D012825:Silicon