title: Role of carboxylate chelating agents on the chemical, structural and textural properties of hydroxyapatite.
abstract: Organically-modified hydroxyapatite materials were synthesized through the addition of oxalic, succinic, adipic and citric acids to a calcium hydroxide solution before neutralization by ammonium dihydrogenphosphate. All carboxylic acids have a significant influence on apatite crystallinity and nanoparticle size, as indicated by XRD and TEM. Chemical and thermogravimetric analyses as well as FTIR and {(1)H}-(13)C CP MAS NMR spectroscopies indicate that the additives are present in the final material. (1)H, {(1)H}-(31)P HPDec MAS, CP MAS and 2D {(1)H}-(31)P CP-HETCOR MAS NMR experiments suggest that carboxylic acids are localized on the apatite nanocrystallite surface, resulting in the formation of a disordered outer layer. Nitrogen sorption measurements indicate minor modifications of the specific surface area of the resulting mesoporous materials upon carboxylic acid addition but more significant variations in the average dimensions of the pores as well as in the chemical nature of the pore surface. Although these evolutions are mainly in good agreement with the ligand affinity for calcium ions in solution, an unexpected difference was observed between succinic and adipic acid, that may be attributed to steric constraints resulting from the interfacial nature of the calcium-ligand interactions. These data should provide useful guidelines to identify novel efficient additives to control apatite growth.
authors.affiliation: Laboratoire de Chimie Physique Générale, Département de Chimie, Faculté des Sciences, BP 1014, Rabat, Marocco.
authors.forename: Karima
authors.initials: K
authors.lastname: Achelhi
authors.forename: Sylvie
authors.initials: S
authors.lastname: Masse
authors.forename: Guillaume
authors.initials: G
authors.lastname: Laurent
authors.forename: Ahmed
authors.initials: A
authors.lastname: Saoiabi
authors.forename: Abdelaziz
authors.initials: A
authors.lastname: Laghzizil
authors.forename: Thibaud
authors.initials: T
authors.lastname: Coradin
mesh_terms: D001672:Biocompatible Materials / Q000138:chemical synthesis* / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry; D002126:Calcium Hydroxide / Q000737:chemistry; D002264:Carboxylic Acids / Q000737:chemistry*; D002413:Cations, Divalent / Q000737:chemistry; D002614:Chelating Agents / Q000737:chemistry*; D017886:Durapatite / Q000138:chemical synthesis* / Q000737:chemistry*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry; D009584:Nitrogen / Q000737:chemistry; D010316:Particle Size; D010710:Phosphates / Q000737:chemistry; D016062:Porosity; D012996:Solutions / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013818:Thermogravimetry; D014961:X-Ray Diffraction
chemical_list: D001672:Biocompatible Materials; D002264:Carboxylic Acids; D002413:Cations, Divalent; D002614:Chelating Agents; D008024:Ligands; D010710:Phosphates; D012996:Solutions; C024788:ammonium phosphate; D017886:Durapatite; D009584:Nitrogen; D002126:Calcium Hydroxide; D002118:Calcium