Abstract
Calcium hydrogen phosphate dihydrate is a precursor material of hydroxylapatite; the mineral phase of calcified tissues, and is a biomaterial that is known to show high biocompatibility and resorbability in-vivo. It exhibits anisotropic growth and dissolution behaviors, and quite recently, its conversion kinetics into hydroxylapatite has been reported to alter on coatings with distinct crystal alignments. These imply that biological behaviors of polycrystalline calcium hydrogen phosphate dihydrate are affected by crystal alignment. Meanwhile, an intense magnetic field is a useful tool to induce crystal alignment in various nonmagnetic substances. In this study, the possibility to control crystal alignment of polycrystalline calcium hydrogen phosphate dihydrate using a magnetic field has been investigated. Calcium hydrogen phosphate dihydrate powder having plate-like morphology was synthesized and then its deflocculated suspension was consolidated under a magnetic field of up to 3 T. X-ray diffraction measurements showed that the intensity ratio of (121) against (020) increased on the surface perpendicular to the magnetic field with intensifying the magnetic field strength. Under a 3 T magnetic field, high alignment against (121) plane has been observed which is unfamiliar for calcium hydrogen phosphate dihydrate. The results indicate that a magnetic field successfully induced crystal alignment in polycrystalline calcium hydrogen phosphate dihydrate.
Highlights
Calcium hydrogen phosphate dihydrate (CHPD; CaHPO4·2H2O), commonly known as the mineral brushite, is a type of calcium phosphate that exhibits higher nucleation rate and lower stability under physiological conditions compared to other calcium phosphate phases (Giocondi et al, 2010; Tamimi et al, 2012)
Calcium hydrogen phosphate dihydrate powder having plate-like morphology was synthesized and its deflocculated suspension was consolidated under a magnetic field of up to 3 T
These results indicate that the b-axis of CHPD tends to move away from the magnetic field direction and that crystal alignment against (121), which we believe is unfamiliar for CHPD, was successfully induced by applying the magnetic field
Summary
Calcium hydrogen phosphate dihydrate (CHPD; CaHPO4·2H2O), commonly known as the mineral brushite, is a type of calcium phosphate that exhibits higher nucleation rate and lower stability under physiological conditions compared to other calcium phosphate phases (Giocondi et al, 2010; Tamimi et al, 2012). Various properties of CHPD have been reported to be dependent on its crystallographic orientation (anisotropy), most likely due to its anisotropic crystal structure. Both growth and dissolution rates of CHPD were reported to be slowest on the [101]Ia step (Giocondi et al, 2010 ). Conversion kinetics of CHPD into hydroxylapatite has been recently reported to alter on CHPD coatings with distinct crystal alignment (Prasad & Kamath, 2013). These results imply that crystal alignment affects biological properties of polycrystalline CHPD
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