Papers by Keyword: Calcium Metaphosphate

Abstract: Calcium metaphosphate (CMP) fine powders were produced by a chemical precipitation method. In order to produce the powders, CMP was prepared by the mixing of two precursors, such as calcium oxide (CaO) and phosphate acid (H3PO4). Sparingly soluble chemicals, the Ca/P ratio of the mixture was set to be 0.50 to produce stoichiometric CMP, were chemical agitated in phosphate acid solution. At least 3 hours of pre-hydrolysis of phosphorus precursor were required to obtain CMP phase. The CMP powders were dried in a drying oven at 60°C for 72 hours and then heat-treated at various temperatures at a ramp of 1°C /min in air for various hours. The obtained powder was analyzed using XRD, XRF, FT-IR, SEM, TG-DTA, Zeta Potential Meter, Specific Surface Area, and Particle Size Analyzer. The results showed that obtained CMP powders have a significantly powder characteristics.

Abstract: OH groups on hydroxyapatite (HA) and calcium metaphosphate (CMP) were evaluated by grafting tetraethyl orthosilicate (TEOS) and 3-aminopropyltriethyloxysilane (3-APTES) which can bond covalently with OH group of ceramic biomaterials. The prepared HA and CMP disks were soaked in pH 2 and 5 of acidic water and ethanol solution respectively, where pH change of each solution was measured during soaking of samples. After grafting TEOS and 3-APTES on HA and CMP disks, samples were ultrasonically cleaned in distilled water and soaked in pH 5 of ethanol solution, and pH measurement was carried out in the same manner. The pH value of HA and CMP in aqueous solution at pH 2 increased with time continuously, resulting from dissolution of HA and CMP by acidic condition on surface. At pH 5 in aqueous solution, it was the same though the pH increase was smaller. In case of ethanol at pH 5 with HA, though pH value went up slightly, the curve became saturated with time, while there was no change in pH with CMP. After grafting TEOS and 3-APTES, pH values were stabilized with few changes, indicating that there was no direct chemical reaction between the acidic media and the surface of samples due to covalently grafted TEOS and 3-APTES layer. In conclusion, it was confirmed that OH group on the surface of HA was crystallographic and chemical one rather than physically adsorbed one by grafting TEOS or 3-APTES and it will serve an effective binding site for calcium and phosphate ions, or minerals.

Abstract: To increase the mechanical properties of PLA used for fracture inner fixation, β-calcium metaphosphate whiskers were prepared by controlled crystallization in the glass. The factors influencing the morphology of the samples, such as component, time and temperature of crystallization were discussed. Results showed that the high quality of β-calcium metaphosphate whiskers can be obtained by crystallization treating for 36 hours and washing for 48 hours at 80°C distilled water. β-calcium metaphosphate whiskers having high aspect ratios of 20-100 with diameters of 1-5μm were achieved at the optimized conditions.

Abstract: As a part of the effort to develop a suitable scaffold for tissue-engineered bone regeneration, we modified calcium metaphosphate (CMP) ceramic with Na20 and evaluated its efficiency as a scaffold. We incorporate 5% Na20 into pure CMP and prepare for an average pore size of 250 or 450 µm average pore sizes. The incorporation of 5% Na2O caused reduced compressive strength and there was no change in biodegradability. The in vitro cellular attachment and proliferation rate, however, were slightly improved. The 5% Na2O-incorporated macroporous CMP ceramic-cell constructs treated with Emdogain induced ectopic bone formation more effectively than those without Emdogain treatment. These results suggest that the incorporation of 5% Na2O into pure CMP is not effective for improving the physical characteristics of pure CMP but it is positive for improving the cellular reaction and osteogenic effect with the addition of Emdogain.

Abstract: Five kinds of gypsums, (1) CaSO4•2H2O (caldium sulfate dihydrate; CSD), (2) CaSO4•1/2H2O (calcium sulfate hemihydrate; CSH), (3) CaSO4 (calcium sulfate anhydrite; CSA), (4) CSH200 (CSH heat-treated at 200°C after self-hardening), and (5) CSH600 (CSH heat-treated at 600°C after self-hardening) were used as candidates for coating materials on calcium metaphosphate (CMP) scaffod to control degradation rate of CMP and to extend degradation limit. The disks of CSD, CSH, CSA, CSH 200, and CSH600 were prepared by self-hardening after mixing with water, where CSH200 and CSH600 were heat-treated at 200°C and 600°C, respectively. In order to control fast resorption rate of gypsum, CMP-CSA composites were prepared with different CSA contents such as 0, 5, 10, 20, 30, 50, and 70 vol% and heat-treated at 900°C for 4 hours. The degradation rates of various gypsums were evaluated in revised simulated body fluid (r-SBF) for 1, 3, 7, and 21 days, respectively. Degradation rate of each specimen was measured in terms of weight loss change with time and degraded surface morphology was examined by SEM. All kinds of gypsums were transformd into CSD after self-hardening with water. Most of gypsums were degraded by 35~60 wt% at 7 days and by 70~99 wt% at 21 days of soaking in SBF. In the group of CMP-CSA composites, the degree of degradation of them was considerably retarded compared to that of five pure gypsums. The surface morphology showed elongated needle-like crystals during the degradation with time.

Abstract: Degradation characteristics of calcium metaphosphate (CMP) ceramics substituted by 5, 10, 15, 20 mol% of NaPO3 and KPO3, respectively, was evaluated in revised simulated body fluid (R-SBF) by measuring the weight change, flexural strength, crystalline phases, and surface morphology with immersion period. The weight loss of CMP substituted by KPO3 was significantly higher than that of CMP substituted by NaPO3. The weight loss in the KCa(PO3)3–CMP samples was due to the dissolution of KCa(PO3)3 phase. The flexural strength of NaCa(PO3)3–CMP samples increased, however, that of KCa(PO3)3–CMP samples decreased significantly due to the dissolution of KCa(PO3) phase with immersion period. The dissolution of KCa(PO3)3 phase formed a pore structure in KCa(PO3)3–CMP samples.

Abstract: A novel process was developed to fabricate polymer/ceramic composites for bone tissue engineering. The mixture of polylactic acid (PLA), calcium metaphosphate (CMP), and NaCl were compressed and subsequently heated. After dissolving the NaCl salts, porous biodegradable polymer/ceramic composite scaffolds were formed. The characteristics of the scaffolds were compared to those of scaffolds fabricated using a conventional solvent casting method, in terms of pore structure, pore size distribution, and mechanical properties. The scaffolds were seeded by osteoblasts and cultured in vitro or implanted into nude mice subcutaneously for up to 5 weeks. Cells were better grown to form tissue-like structures on CMP/PLA composites fabricated by the Press-and-Baking method. In addition, the alkaline phosphatase activity of and calcium deposition in the scaffolds explanted from mice were enhanced significantly for the scaffolds by Press-and-Baking compared to them by solvent casting. Taken together, these results suggest that CMP promote cell differentiation and proliferation via direct interaction with cells in the CMP/PLA composites. This novel PLA/CMP composite will be applicable for bone tissue engineering to support and cell differentiation and growth.

Abstract: As a part of the efforts to develop a suitable scaffold optimizing bone regeneration that has similar physical properties to bone, we modified calcium metaphosphate (CMP) ceramics with K2O and evaluated their efficiency as a scaffold for tissue engineered bone tissue regeneration. Macroporous CMP ceramics modified by incorporation of 5% K2O to improve biodegradability were prepared to have 250 and 450 µm average pore sizes, respectively. The modified CMP ceramics were cultured with mouse primary calvarial osteoblastic cells in osteogenic media for 2 weeks and these cell-CMP ceramic constructs with or without Emdogain treatment were implanted in the SCID mice subcutaneous pouches. After 1, 2, and 3 weeks, the degree of ectopic bone formation was evaluated. The modified macroporous CMP ceramic-cell constructs treated with Emdogain induced ectopic bone formation, whereas the modified CMP ceramic-cell constructs without Emdogain treatment induced no ectopic bone formation. This result suggests that the Emdogain treatment on cell-scaffold constructs for tissue engineered bone regeneration may be effective for osteogenic activation of attached cells.

Abstract: Porous calcium metaphosphate granules for bone fillers were prepared by starch consolidation with baking powder and surfactant. Paste for foaming was prepared by the mixing of calcium metaphosphate powder and water with the various amount of starch (10~20㎛ size), where solid contents 30%, 45%, 60% of the paste. In order to obtain the optimum micro/macro porous structure, the appropriate contents of baking powder and surfactant at a fixed content of starch were examined. In order to examine the content of baking powder on pore morphology, the baking powder was added 60, 180, and 300 wt% of the paste at fixed content of starch. And then, in order to investigate the effect of surfactant on porous structure, surfactant was added 0.035, 0.1, and 0.16 wt% of paste weight at fixed content of starch and baking powder. Foaming was conducted using microwave method, and foamed samples were sintered at 900 °C. The sintered porous blocks with starch only showed uneven and closed macro pores without any micro pores. However, the sintered porous blocks with starch, baking powder, and surfactant showed homogeneous micro and macro porous structures ranging 20~60, and 300~1000 ㎛ in pore size, respectively. The porosity was increased with the increase of surfactant up to about 70 %.