title: Biocompatibility of magnesium phosphate minerals and their stability under physiological conditions.
abstract: Magnesium phosphates such as newberyite (MgHPO(4)·3H(2)O) are formed in vivo and are known to be biodegradable and nontoxic after implantation. Indeed, magnesium apatites have been shown to support osteoblast differentiation and function, and bone formation can occur around metallic magnesium implants. However, very little is known regarding the precipitation and stability of magnesium phosphates in physiological environments. In order to address this, the aqueous formation of magnesium phosphate as a function of pH, temperature and ion concentration is reported. Physicochemical characterization of the precipitates was carried out; additionally, biocompatibility and gene expression of osteoblast differentiation markers for bone formation via an in vitro cell culture assay were determined. Precipitation conditions for newberyite, tribasic magnesium phosphate pentahydrate, holtedahlite, bobierrite and cattiite were determined. Under physiological conditions of pH, temperature and magnesium phosphate concentration, no precipitates were formed. However, at concentrations 10-100 times higher than physiological, magnesium phosphate precipitates of cattiite and newberyite were formed. These two minerals demonstrated biocompatibility with osteoblast cultures and induced osteoblast adhesion and differentiation. The pattern of expression of OCN and CollA1 genes in the presence of newberyite crystals was comparable to that of calcium phosphate bioceramics. In our experiments, we have shown that certain magnesium phosphate phases such as newberyite and cattiite are able to promote in vivo osteogenic activity in a similar way to calcium phosphates such as hydroxyapatite and brushite. This confirms the great potential of magnesium phosphate ceramics in the development of new biomaterials for bone regeneration.
authors.affiliation: Faculty of Dentistry, McGill University, Montreal, Canada. faleh.tamimimarino@mcgill.ca
authors.forename: Faleh
authors.initials: F
authors.lastname: Tamimi
authors.forename: Damien
authors.initials: D
authors.lastname: Le Nihouannen
authors.forename: David C
authors.initials: DC
authors.lastname: Bassett
authors.forename: Suzette
authors.initials: S
authors.lastname: Ibasco
authors.forename: Uwe
authors.initials: U
authors.lastname: Gbureck
authors.forename: Jonathan
authors.initials: J
authors.lastname: Knowles
authors.forename: Adrian
authors.initials: A
authors.lastname: Wright
authors.forename: Andrew
authors.initials: A
authors.lastname: Flynn
authors.forename: Svetlana V
authors.initials: SV
authors.lastname: Komarova
authors.forename: Jake E
authors.initials: JE
authors.lastname: Barralet
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D001672:Biocompatible Materials; D017931:DNA Primers; D006863:Hydrogen-Ion Concentration; D017616:Magnesium Compounds; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008855:Microscopy, Electron, Scanning; D009994:Osmolar Concentration; D010710:Phosphates; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D001672:Biocompatible Materials; D017931:DNA Primers; D017616:Magnesium Compounds; D010710:Phosphates; C030781:magnesium phosphate