Healthy bone has many physiological microcracks, which may be involved in the release of bone matrix-derived factors and act to accelerate bone-remodeling process. In this study, the mouse parietal bone fragments (5x5x1mm3) were demineralized by acidic electrolyzed water (AEW: pH2.7) or distilled water (DW: pH5.2) at 120W and 38KHz for 20 min. Each bone was implanted into subcutaneous tissue of 10 week-old male nude mouse, and explanted at 4 and 6 weeks. AEW-bone showed clear enlargement and union of cracks on SEM. AEW-bone revealed active bone induction over wide areas at 6 weeks, while DW-bone induced new bone in limited area. We concluded that the AEW-bone had better performance in bone induction than the DW-bone. Our micro-damage technique combined with AEW and the ultrasonic irradiation will contribute to improve surface area and 3D structure of the dense bone and promote bone formation in the initial stage for bone remodeling.
We have previously developed a chelate-setting calcium-phosphate cement (CPC) consisting of hydroxyapatite (HAp) powders surface-modified with inositol hexaphosphate (IP6). In the present study, mechanically ball-milled α-tricalcium phosphate (α-TCP) powders were added into the IP6-HAp cement in order to enhance its anti-washout capability and mechanical properties. After optimization of the ball-milling conditions, the cement specimens mixed with various amounts of the prepared α-TCP powders were fabricated. Examinations of their mechanical properties revealed significant increase of compressive strength (CS) with the addition of the α-TCP powders. Further, it was demonstrated that the specimens of the IP6-HAp powders / the α-TCP powders mixing ratios of 20/80 and 30/70 [g/g] exhibited comparatively high anti-washout capability. In conclusion, these cements are promising chelate-setting CPCs with enhanced anti-washout capability and mechanical properties.
Preparation conditions of millimeter-scale fibrous octacalcium phosphate (Ca8H2(PO4)6・5H2O: OCP) particles by homogeneous precipitation method were examined, using Ca(NO3)2, (NH4)2HPO4, urea ((NH2)2CO; precipitant) and conc. HNO3 (precipitation inhibitor). The starting solution (200 cm3) with 0.0266 mol・dm-3 Ca(NO3)2 and 0.0200 mol・dm-3 (NH4)2HPO4, i.e., the stoichiometric Ca/P ratio of OCP (=1.33), was heated under reflux at 80°C for 24 h in order to encourage the precipitation, due to the hydrolysis of urea to dissociate ammonia; however, the reaction products were not only OCP but also CaHPO4. The increase in Ca/P ratio and diluted concentrations of starting calcium phosphate solution made the formation of longer fibrous OCP particles possible, i.e., approximately 1000 μm of mean long-axis length due to the heating of 0.0500 mol・dm-3 Ca(NO3)2 and 0.0300 mol・dm-3 (NH4)2HPO4 solution (Ca/P ratio=1.67) under reflux and approximately 1200 μm due to the heating of 0.0500 mol・dm-3 Ca(NO3)2 and 0.0250 mol・dm-3 (NH4)2HPO4 solution (Ca/P ratio=2.00)), both using 0.20 mol・dm-3 urea.
Phosphorylation of β-arbutin has been achieved using inorganic cyclo-triphosphate (P3m) in aqueous solution. The optimum condition for the phosphorylation of β-arbutin with P3m is β-arbutin : P3m = 0.1 mol/L : 0.5 mol/L, pH 11 and 40°C. 4-Triphospho-β-arbutin was synthesized with the yield of 90%. The reaction mechanism of β-arbutin with P3m was discussed. We have successfully introduced the triphosphate group in one molecule. Phosphorylated β-arbutin is expected that the permeability of β-arbutin into the skin will be increased by introducing a phosphate group.
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