Structure Of Tricalcium Phosphate Research Articles

Cerium-tricalcium phosphate coating for 316L stainless steel in simulated human fluid: Experimental, biological, theoretical, and electrochemical investigations

Tricalcium phosphate (TCP) has many advantages in biomedical applications especially in teeth and bones, and therefore many researches focused on enhancing the properties of this material by different methods. Because of importance of the cerium in repairing the performance of cells in human body, this work aims to substitute the cerium in TCP structure to give better properties. Coating of Ce/TCP on SS 316L was applied by radio frequency (RF) sputtering technique. This coating was characterized by XRD, FESEM/EDS with EDS mapping, AFM, and electrochemical analysis. These techniques confirm the presence of Ce with TCP in deposited layer and the SEM gave more compact layer with higher roughness and lower average diameter. EDS mapping shows the presence of suggested metal ions in the coating. Theoretical study by DFM was done to illustrate the substitution of Ce in the lattice structure and stable sites for accommodation. Electrochemical studies showed that presence of the coating layer improves corrosion resistance with 91% protection efficiency.

Geometrical Structure of Honeycomb TCP to Control Dental Pulp-Derived Cell Differentiation.

Recently, dental pulp has been attracting attention as a promising source of multipotent mesenchymal stem cells (MSCs) for various clinical applications of regeneration fields. To date, we have succeeded in establishing rat dental pulp-derived cells showing the characteristics of odontoblasts under in vitro conditions. We named them Tooth matrix-forming, GFP rat-derived Cells (TGC). However, though TGC form massive dentin-like hard tissues under in vivo conditions, this does not lead to the induction of polar odontoblasts. Focusing on the importance of the geometrical structure of an artificial biomaterial to induce cell differentiation and hard tissue formation, we previously have succeeded in developing a new biomaterial, honeycomb tricalcium phosphate (TCP) scaffold with through-holes of various diameters. In this study, to induce polar odontoblasts, TGC were induced to form odontoblasts using honeycomb TCP that had various hole diameters (75, 300, and 500 μm) as a scaffold. The results showed that honeycomb TCP with 300-μm hole diameters (300TCP) differentiated TGC into polar odontoblasts that were DSP positive. Therefore, our study indicates that 300TCP is an appropriate artificial biomaterial for dentin regeneration.

Effect of titanium and zirconium substitutions for calcium on the formation and structure of tricalcium phosphate and hydroxyapatite

The effect of Ti and Zr substitutions for Ca cations on the formation of tricalcium phosphate and hydroxyapatite has been studied in a wide concentration range: from 0.1 to 20 mol %. Upon the incorporation of Ti and Zr cations into tricalcium phosphate, the major forming phase is β-tricalcium phosphate. On the addition of low substituent concentrations to hydroxyapatite, we observe the formation of a single-phase material with the apatite structure. Increasing the substituent concentration to 10–20 mol % Ti or 20 mol % Zr leads to the formation of tricalcium phosphate. The unit-cell volume of the cation-substituted tricalcium phosphates has been shown to decrease with increasing substituent concentration. In the zirconium-containing hydroxyapatites, the unit-cell volume decreases with increasing zirconium concentration, whereas the titanium-containing hydroxyapatites exhibit an opposite tendency.

Microwave synthesis of functionally graded tricalcium phosphate for osteoconduction

Porosity is an important parameter of biomaterials used to replace bone. Crystalline tricalcium phosphate (TCP) is a common ceramic used to substitute bone in small quantities and coat medical devices. Using microwave combustion synthesis (MCS) to provide volumetric heating of the reactant materials, along with varied urea to calcium phosphate concentration ratios, a porosity structure is synthesized. The microwave power provided 145W and the reactants are exposed for 5min. Results from in-situ IR thermal analysis show heating in two phases: initially (i.e., first 30s) thermal energy is localized along the surface of the sample followed by (i.e., remaining 5min) volumetric heating and MCS. The product material is confirmed to be tricalcium phosphate via FTIR analysis. Scanning electron microscopy (SEM) images show increased porosity with increased urea concentration. By controlling the concentration gradient in the reactant sample, the product material produced a tailored porosity gradient. Moreover, the MCS tricalcium phosphate is demonstrated to be biocompatible and does not affect cell proliferation by crystal violet tests. This study provides a new perspective on volumetric combustion synthesis by using weak microwave energy to facilitate the formation of a tailored TCP structure.

Preparation of Spherical Zn-Substituted Tricalcium Phosphate Powder by Ultrasonic Spray-Pyrolysis Technique and Its Characterization

Zinc, an essential trace element, has a stimulatory effect on bone formation. To enhance the osteoconduction of implant materials such as hydroxyapatite and tricalcium phosphate (TCP), zinc was incorporated into them. In this study, we have synthesized spherical zinc-substituted TCP (Zn-TCP) powders using ultrasonic spray-pyrolysis technique, fabricated Zn-TCP ceramics, and characterized their powder properties. Four kinds of Zn-TCPs with various amounts of zinc content were prepared, to examine the influence of zinc addition to the crystal structure of TCP and to compare the different Zn-TCPs with each other. Zn-TCP ceramics were fabricated from the resulting powders under different sintering temperatures. Zn-TCP samples were analyzed and led to the following results: the resulting powders were composed ofα- andβ-TCP phases, whereas the fabricated ceramics mainly consisted ofβ-TCP phase. The determination of zinc content in the resulting powders and fabricated ceramics showed a maximum content of ~12 mol%. The resulting powders consisted of spherical particles with diameters <2 μm. The lattice constants of ceramics did not show a significant change of thea-axis,b-axis, andc-axis. The bulk density of Zn-TCPs showed their maximum at 1100°C, while the bulk density of Zn-TCP(0) was greatest at 1000°C.

Biologic Characteristics of Bone Substituting Tissue Engineering Construction Based on Calcium Phosphate Ceramics, Autologous Mesenchymal Stromal Cells and Fibrin Hydrogel

Biological characteristics of bone substituting tissue engineering construction (TEC) that contained porous calcium phosphate ceramic granulate (CPC) of phase structure ((tricalcium phosphate (TCP)), fibrin hydrogel and autologous multipotent mesenchymal stromal cells (auto-MMSC) induced and non-induced to osteogenic differentiation were studied in vivo. The following characteristics of TEC were determined: ability to transfer within its structure the viable auto-MMSC with preservation of their regeneration potential; ability to osteogenesis only under conditions of orthotopic implantation; ability of induced to osteogenic differentiation auto-MMSC to participate in the reparative processes for not more than within 6 weeks after implantation; negative affect of fibrin hydrogel on the osteoinductive properties of CPC within TCP structure. It was shown that to provide osteogenesis in the implanted TEC not only the viable auto-MMSC but simultaneous presence of osteoinductive and osteoconductive factors was required. No bone formation in a critical bone defect and in ectopic implantation takes place without observance of these conditions.

Biologic Characteristics of Bone Substituting Tissue Engineering Construction Based on Calcium Phosphate Ceramics, Autologous Mesenchymal Stromal Cells and Fibrin Hydrogel

Biological characteristics of bone substituting tissue engineering construction (TEC) that contained porous calcium phosphate ceramic granulate (CPC) of phase structure ((tricalcium phosphate (TCP)), fibrin hydrogel and autologous multipotent mesenchymal stromal cells (auto-MMSC) induced and non-induced to osteogenic differentiation were studied in vivo. The following characteristics of TEC were determined: ability to transfer within its structure the viable auto-MMSC with preservation of their regeneration potential; ability to osteogenesis only under conditions of orthotopic implantation; ability of induced to osteogenic differentiation auto-MMSC to participate in the reparative processes for not more than within 6 weeks after implantation; negative affect of fibrin hydrogel on the osteoinductive properties of CPC within TCP structure. It was shown that to provide osteogenesis in the implanted TEC not only the viable auto-MMSC but simultaneous presence of osteoinductive and osteoconductive factors was required. No bone formation in a critical bone defect and in ectopic implantation takes place without observance of these conditions.

Characterization and <i>In Vitro</i> Evaluation of Silicate-Containing Tricalcium Phosphate Prepared through Wet Chemical Process

Tricalcium phosphate (TCP) ceramics are useful biodegradable bone-repairing materials. Silicate-containing TCP ceramics are expected to be useful as biodegradable bone-repairing materials which promote the bone regeneration because it has been reported that the silicate promotes bone formation. In the present study, silicate-containing TCP ceramics were prepared through a wet chemical process at the starting compositions from 0 to 0.05 in the Si/(P+Si) molar ratio. The prepared silicate-containing TCP ceramics were characterized and evaluated in vitro. The crystal phase of the products was α-TCP, and the tendency that the lattice constants linearly shifted from 0 to 0.05 in the starting Si/(P+Si) molar ratio was observed. It is speculated that the added silicate was incorporated in the crystal structure of TCP. The pellets were prepared by a sintering process, and soaked in a simulated body fluid (SBF) to estimate their bone-bonding ability. The addition of silicate to TCP promoted to hydroxyapatite formation on the TCP ceramics in SBF. This result implies the high possibility that the silicate addition would promote the bone-bonding ability of the TCP ceramics.

Design and processing of ZnO doped tricalcium phosphate based materials: Influence of β/α polymorph phase assemblage on microstructural evolution

Tricalcium phosphate (TCP) based biomaterials are excellent candidates in hard tissue engineering due to their similarity to the natural bone composition and outstanding properties. The presence of additives such as (Mg2+, Zn 2+, F−, CO32− and/or SiO4−) in solid solution in the structure of TCP, affects the stability of its different polymorphs and therefore the properties of TCP based biomaterials. It is known that the incorporation of zinc in TCP in the non-toxic level stimulates bone growth and its mineralization, hence its interest. Nevertheless its effect on phase assemblage and microstructure evolution has not been clearly established. The main purpose of this study was to synthesize TCP and zinc doped monophasic/biphasic α/β-TCP dense biomaterials, by solid-state sintering process, with different ZnO contents and controlled phase proportions and microstructure on the final material. The effect of ZnO content and sintering temperature on phase assemblage, densification and microstructural evolution has been investigated.

Human osteoblasts adhesion and proliferation on magnesium-substituted tricalcium phosphate dense tablets

Tricalcium phosphate (TCP) is recognized as a promising bone replacement material due to its high bioactivity and resorbable properties. To mimic biological apatites, incorporation of magnesium (Mg) in TCP was proposed. Mg-substituted TCP (beta-TCMP) and beta-TCP dense tablets were obtained by pressing and sintering at 1,000 degrees C Mg-substituted calcium deficient apatite (Mg-CDA) and commercial TCP, respectively. The materials were characterized using X-ray diffraction, infrared spectroscopy and electron microscopy. Human osteoblast cells (SaOs2) were seeded onto the sintered tablets for 4 h, 24 h and 7 days. Results showed that Mg-CDA was completely transformed into beta-TCMP. Moreover, beta-TCMP stimulated adhesion and proliferation of human osteoblast cells. Consequently, the magnesium incorporation on calcium deficient apatites followed by sintering at 1,000 degrees C seems to be a useful path to obtain biocompatible and non cytotoxic dense tablets with TCP structure with potential application on bone engineering.

Effect of preparation conditions on the pore structure of tricalcium phosphate and on the kinetics of its reaction with the lead ion in solution

The kinetics of the reaction of differently prepared tricalcium phosphate samples with the lead ion are considered. As distinct from mesoporous samples, samples with a mixed pore structure dominated by large and medium-sized pores are highly reactive toward the lead ion.

訂正

訂正

訂正

訂正

Changes in Composition and Structure of Tricalcium Phosphate under Different pH Conditions

α-Ca3(PO4)2 粉末-H2O系分散液を種々のpHに調製し, これをそのままあるいは反応中のpHを一定保持しながら, 80℃で主に2時間の加温処理を行った. 得られた固相分の結晶相とpH条件との関係を明らかにし, 更にアパタイト生成物に関しては, 反応pH条件とCa/P比, 構成イオン種, 加熱変化及び粒子形態などとの関連を検討した.反応中のpHを一定に保持してもしなくても, pHが約4.6以上であればアパタイト単一相になり, これ以下pH 4.3までは短冊状結晶のアパタイトとオクタカルシウムホスフェートとの混合相になり, pH 4.2-3.0では角板状のCaHPO4を主体としていた. アパタイト単一相の場合の結晶は, 保持pH値を変えることによって板状あるいは花片状及び柱状のおのおのの形態に成長した. pHを一定保持しない場合にはすべて花片状であった. 反応中のpHが高いほど, アパタイトへの転化は遅くなるけれども, アパタイトのCa/P比は増大しやすくなった. 高Ca/P比のアパタイトになるほど, 含水量やHPO42-含量の減少と, OH-含量及び結晶性の増大が認められた. アパタイトの含水状態, 含有HPO42-の脱水縮合温度はオクタカルシウムホスフェートのそれらと類似していた。