β-TCP Powder Research Articles

Densification and Mechanical Behavior of β-Tricalcium Phosphate Bioceramics

Nano-size β-tricalcium phosphate powders with average grain size of 80 nm were prepared by the wet chemical precipitation method with calcium nitrate and di-ammonium hydrogen phosphate as calcium and phosphorus precursors, respectively. The precipitation process employed was also found to be suitable for the production of sub-micrometre β-TCP powder in situ. The sinterability of the nano-size powders, and the microstructure, mechanical strength of the prepared β-TCP bioceramics were investigated. Bioceramic sample characterization was achieved by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), and density measurements. Powders compacted and sintered at 800, 900, 1000 and 1100 °C showed an increase in relative density from 70 % to 93 %. The results revealed that the maximum hardness of 240 H was obtained for β-TCP sintered at 1100 °C.

Large scale production of yolk-shell β-tricalcium phosphate powders, and their bioactivities as novel bone substitutes.

This paper proposes the production of yolk-shell structured β-tricalcium phosphate (β-TCP) powders using a spray-drying method, suitable for commercial scale production. Spray-dried precursor powders, consisting of calcium-phosphate salts and each of the various carbon source materials, are combusted in an oxygen atmosphere to obtain a yolk-shell structure. Only dextrin among the carbon source materials investigated shows promise in the production of β-TCP yolk-shell powders. By evaluating their apatite-forming capacity in simulated body fluid, the outstanding bioactivity of β-TCP yolk-shell powders is confirmed: numerous acicular and newly formed hydroxyl carbonate apatite crystals cover the entire β-TCP surface after a single day of soaking. These crystals are observed on both the outer and inner surfaces of the shells, and on the outer surface of the core, which is encouraging for its potential use as a bone grafting material.

Densification and Mechanical Behavior of β-Tricalcium Phosphate Bioceramics

Nano-size β-tricalcium phosphate powders with average grain size of 80 nm were prepared by the wet chemical precipitation method with calcium nitrate and di-ammonium hydrogen phosphate as calcium and phosphorus precursors, respectively. The precipitation process employed was also found to be suitable for the production of sub-micrometre β-TCP powder in situ. The sinterability of the nano-size powders, and the microstructure, mechanical strength of the prepared β-TCP bioceramics were investigated. Bioceramic sample characterization was achieved by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), and density measurements. Powders compacted and sintered at 800, 900, 1000 and 1100 °C showed an increase in relative density from 70 % to 93 %. The results revealed that the maximum hardness of 240 H was obtained for β-TCP sintered at 1100 °C.

Effects of Mn-doping on the structure and biological properties of β-tricalcium phosphate

Doping calcium phosphates with trace elements that exist in bone tissues is beneficial in terms of cell–material interactions and in vivo performance of the bone grafts made thereof. Manganese (Mn) is an essential element for normal growth and metabolism of bone tissues, but studies reporting the effects of Mn-doping calcium phosphates are scarce. The present study investigated the influence of Mn-doping on the structure, morphology and biological properties of β-tricalcium phosphate [β-Ca3(PO4)2] (β-TCP). Mn-doped (MnTCP) powders, with Mn contents varying from 0 to 10mol%, were obtained through an aqueous precipitation method followed by heat treatment at 800°C. The successful incorporation of Mn into β-TCP structure was proved through quantitative X-ray diffraction (XRD) phase analysis coupled with structural Rietveld refinement. Increasing Mn concentrations led to decreasing trends of a- and c-axis lattice parameters, and Mn-doping also significantly affected the morphology of β-TCP powders. In vitro proliferation and differentiation assays of MC3T3-E1 osteoblastic-like cells, grown in the presence of the powders, revealed that the biological benefits of Mn-doped β-TCP are limited to lower Mn incorporation levels and potentially related to their surface microstructure. The Mn1-βTCP composition revealed the best set of bioactivity properties, potentially a good candidate for future applications of β-TCP materials in osteoregeneration.

Use of a gelatin hydrogel membrane containing β-tricalcium phosphate for guided bone regeneration enhances rapid bone formation.

The purpose of this study was to evaluate a thin gelatin hydrogel membrane containing β-tricalcium phosphate (G-TCP) for use in guided bone regeneration, a technique that we developed. G-TCP membranes were fabricated from gelatin and β-TCP powder, freezedried, and cross-linked by heating. The resulting G-TCP membranes were as thin as collagen membranes, with high mechanical integrity. Proliferation and differentiation of rat bone marrow stromal cells (BMSCs) on G-TCP and collagen membranes were examined. On both membranes, BMSCs proliferated well and expressed alkaline phosphatase. However, more bone-like mineralized tissue formed on G-TCP membranes than on collagen membranes at 4 weeks. The effects of G-TCP and collagen membranes on bone regeneration in rat parietal bone defects were histologically examined. Bone bridges with mature uniform bone were observed under G-TCP membranes as early as 2 weeks. These results indicate that G-TCP is a GBR membrane that is comparable or superior to collagen membrane.

Bone healing with oxytocin‐loaded microporous β‐TCP bone substitute in ectopic bone formation model and critical‐sized osseous defect of rat

This study investigated the efficacy of the hypothalamic nonapeptide oxytocin (OT) by direct delivery to local defects using a microporous β-tricalcium phosphate (TCP) as the carrier for the future applications as a method to achieve predictable bone regeneration of large osseous defects requiring sinus bone graft and guided bone regeneration procedures for implant placement. Both the ectopic and new bone formation induced by the OT-loaded microporous β-TCP powder was histomorphometrically compared with unloaded β-TCP in a subcutaneous ectopic bone formation model and calvarial critical-sized defects (CSDs) in 45 rats. The OT-loaded β-TCP clearly enhanced ectopic bone formation compared with the unloaded control group. A High initial OT dose (250μg) significantly increased ectopic bone formation at an early healing time-point compared with a lower OT dose (50μg). The OT-loaded samples displayed greater new bone formation in the rat calvarial CSDs. Extensive new bone formation was achieved in the calvarial CSDs with the higher OT dose. These results suggest that local OT delivery to bone substitute promotes new bone formation via an osteoinductive mode of action.

Characterization of mechanical properties and bioactivity of hydroxyapatite/β-tricalcium phosphate composites

Bioactive ceramics attracts much attention as materials for bone implants, because of their high biocompatibility. For example, hydroxyapatite (HA) has bone-bonding ability through a bone-like apatite layer in body environment and β-tricalcium phosphate (β-TCP) has a high bioresorbability in body environment. In this study, HA/β-TCP composites with different β-TCP content (0, 10, 20, and 30 wt.%) were prepared by wet mixing of HA and β-TCP powders, compaction of the powder mixture and sintering. Bending strength of HA/β-TCP composites was measured before and after soaking in simulated body fluid (SBF). The bioactivity of HA/β-TCP composites was also evaluated by soaking in SBF. To improve mechanical properties of HA/β-TCP composites, effects of additive of SiO2 and MgO were also investigated. It was found that the several mechanical properties and ability of apatite formation decreased with β-TCP content. It was also found that the change in bending strength after soaking depended on its surface reaction in SBF and porosity. Addition of SiO2 did not improve mechanical properties and bioactivity. On the other hand, additive of MgO improved several mechanical properties, but lowered the bioactivity in SBF.

Fabrication and Characterization of Porous Biphasic Calcium Phosphate Scaffolds by Doping TiO<sub>2</sub>

This study aims to improve the strength of porous BCP samples by the addition of titanium dioxide (TiO2), the well known biocompatible and strong ceramic. BCP powder with HA/TCP ratio of 70/30 (BCP7030) obtained by mixing a pure HA and β-TCP powder. TiO2 powder with 2 (BCP_2Ti), 5 (BCP_5Ti) and 10 (BCP_10Ti) %wt were added into the BCP7030 powder, then ball milled in ethanol for 6 hrs. The porous samples were fabricated by the combination of the gel-casting and freeze drying techniques. All samples were sintered at 1100°C for 2 hrs. X-ray diffractometry (XRD) and scanning electron microscopy (SEM) were used to determine crystal structures and morphology of the sintered samples, respectively. Mechanical properties and porosity of samples were measured by using the universal testing machine and Archimedess principle, respectively. XRD results showed that the phases of the undoped sample can be indexed HA and β-TCP with the ratio of 70/30 as the major phases. In BCP_2Ti, CaTiO3 was observed as a minor phase among the crystallization of HA and β-TCP with the proportion of 30:70. Meanwhile, in BCP_5Ti and BCP_10Ti, XRD patterns revealed a completely transformation of HA to β-TCP with minor phases of CaTiO3 and TiO2. The microstructure of sintered samples present highly porous structure which consisted of two-dimensional pore channels along the long axis and the short axis, which replicates the ice and pore orientation in the direction of freezing. Relatively, the porosity of the samples was increased with the amount of TiO2. Surprisingly, an additions of the TiO2 was not rather improved the mechanical strength of porous BCP7030 in this study. This might be a result of a high percentage of porosity (84%).

Preparation of porous bioceramics using reverse thermo-responsive hydrogels in combination with rhBMP-2 carriers: In vitro and in vivo evaluation

Porous biphasic calcium phosphates (BCP) were fabricated using reverse thermo-responsive hydrogels with hydroxyapatite (HAp) and β-tricalcium (β-TCP) powder and planetary centrifugal mixer. This hydrogel mixture slurry will shrink and compress the HAp powder during the sintering process. The porous bioceramics are expected to have good mechanical properties after sintering at 1200°C. Reverse thermo-responsive hydrogels of poly[(N-isopropylacrylamide)-co-(methacrylic acid)] p(NiPAAm–MAA) were synthesized by free-radical cross-linking copolymerization, and their chemical properties were evaluated by nuclear magnetic resonance spectroscopy, infrared spectroscopy, and electrospray-ionization mass spectrometry. The lower critical solution temperature (LCST) of the hydrogel was determined using turbidity measurements. A thermogravimetric analysis was used to examine the thermal properties. The porous bioceramic properties were analyzed by X-ray diffraction, scanning electron microscopy, bulk density, compressive strength testing and cytotoxicity. The compressive strength and average porosity of the porous bioceramics were examined at approximately 6.8MPa and 66% under 10wt% p(NiPAAm–MAA)=99:1 condition. The ratio of HAp/β-TCP can adjust two different compositional behaviors during the 1200°C sintering process without resulting in cell toxicity. The (rhBMP-2)-HAp-PLGA carriers were fabricated as in our previous study of the double emulsion and drop-coating technique. Results of animal study included histological micrographs of the 1-mm defect in the femurs, with the rhBMP-2 carrier group, the bioceramic spacer group and the bioceramic spacer with rhBMP-2 carriers group showing better callus formation around the femur defect site than the control group. The optimal dual effects of the bone growth factors from osteoconductive bioceramics and osteoinductive rhBMP-2 carriers produced better bone formation.

A comparative study of proliferation and osteogenic differentiation of rat adipose-derived stem cells in β-tricalcium phosphate (β-TCP), forsterite (Mg2SiO4) and clinoenstatite (MgSiO3)

In this study, the effects of forsterite and clinoenstatite powder extracts on the proliferation and osteogenic differentiation of rat adipose-derived stem cells (ASCs) were investigated and compared with the β-tricalcium phosphate (β-TCP) powder extracts. Methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay and live-dead staining were performed to evaluate the viability and proliferation of rat ASCs. Osteogenic differentiation of rat ASCs were assayed by alkaline phosphatase (ALP) staining and ALP activity test. The expression of osteogenic marker genes (alkaline phosphatase (ALP), runt related transcription factor 2 (Runx2), collagen type Iα1 (Col1α1), secreted phosphoprotein1 (Spp1, osteopontin), integrin binding sialoprotein (Ibsp), bone gla protein (Bglap)) were detected by real-time polymerase chain reaction (PCR). The MTT assay and the live-dead staining showed that all the three ceramics possessed good cytocompatibility with rat ASCs. Furthermore, forsterite and clinoenstatite promoted the proliferation of rat ASCs compared with β-TCP. The results of the ALP activity test and the real-time PCR demonstrated that forsterite and clinoenstatite promoted the osteogenic differentiation of rat ASCs. These results suggested that forsterite and clinoenstatite are bioactive ceramics that may be used for preparation of bone tissue engineering (BTE) scaffolds. forsterite, clinoenstatite, adipose-derived stem cells, osteogenesis, bone, bone tissue engineering

Preparation and Mechanical Properties of PLGA/β-TCP Composites

Poly(lactide-co-glycolide)/β-Tricalcium Phosphate (PLGA/β-TCP) composites were successfully prepared via solution dispersion method. Laser particle size analyzer (LPSA), X-ray diffraction (XRD) and SEM were used to characterize β-TCP powder. The mechanical properties of composites were carried out by the three-point-bending test, and the morphologies of cross-section of composites were observed using SEM. The results indicate that both the bending strength and modulus of composites increased with β-TCP amount of up to 10 wt%, then decreased gradually, indicating the change of fracture mode with the variation of β-TCP content. PLGA/β-TCP would be an ideal and promising biomaterial for internal fixation devices.

Cell response of calcium phosphate based ceramics, a bone substitute material

The aim of this study was to characterize calcium phosphate ceramics with different Ca/P ratios and evaluate cell response of these materials for use as a bone substitute. Bioceramics consisting of mixtures of hydroxyapatite (HAp) and β-tricalcium phosphate (β-TCP) powders in different proportions were pressed and sintered. The physical and chemical properties of these bioceramics were then characterized. Characterization of the biological properties of these materials was based on analysis of cell response using cultured fibroblasts. The number of cells attached to the samples was counted from SEM images of samples exposed to cell culture solution for different periods. These data were compared by analysis of variance (ANOVA) complemented by the Tukey's test. The TCP sample had higher surface roughness and lower density. The adherence and growth of FMM1 cells on samples from all groups was studied. Even though the different calcium based ceramics exhibited properties which made them suitable as bone substitutes, those with higher levels of β-TCP revealed improved cell growth on their surfaces. These observations indicated two-phase calcium phosphate based materials with a β-TCP surface layer to be a promising bone substitute.

The surface microporosity of ceramic biomaterials influences the resorption capacity of osteoclasts

This study investigated the influence of the surface microporosity of beta-tri-calcium phosphate (β-TCP) ceramics on the resorption capacity of osteoclasts. This was achieved by first compacting commercially available β-TCP powder into disks that were sintered at various temperatures, thereby yielding different surface microporosities. Scanning electron microscopy (SEM) and subsequent image processing verified different degrees of surface microporosity on the disks. Rabbit osteoclasts in a bone marrow derived cell suspension were then seeded onto these disks and incubated for 48 h. Tartrate resistant acid phosphatase (TRAP) staining confirmed the presence of osteoclasts on all disks. Actin ring staining that detected actively resorbing OCs showed an inverse linear correlation between the number of actively resorbing osteoclasts (percentage of total OCs on the surfaces) with surface microporosity. These findings should be taken into consideration for the design and/or production of new β-TCP bone graft substitutes.

Effect of pH control of mixture solution on the fabrication of the highly pure β-tricalcium phosphate powders synthesized by liquid–solid mixture precipitation method

The β-tricalcium phosphate (β-TCP; Ca3(PO4)2) powders with high purity could be attained through mixing and precipitating (NH4)2HPO4 with solution state and Ca(NO3)2·4H2O with solid state and controlling the pH of mixture solution in a range from 7.0 to 8.5 within a short time. The FT-IR results showed that the peak of calcium pyrophosphate (Ca2P2O7) excluding the peaks associated with β-TCP appeared at a pH ranging from 5.0 to 7.0 but did not appear at a pH ranging from 7.0 to 8.5. It is considered that the phase purity of β-TCP powders could be significantly improved through liquid–solid mixture precipitation and pH control of mixture solution. The XRD and SEM results showed that the phase purity and the particle size of precipitated β-TCP powders were above 99% and ranged from 200nm to 600nm, respectively.

Biodegradable β-tricalcium phosphate cement with anti-washout property based on chelate-setting mechanism of inositol phosphate

Novel biodegradable β-tricalcium phosphate (β-TCP) cements with anti-washout properties were created on the basis of chelate-setting mechanism of inositol phosphate (IP6) using β-TCP powders. The β-TCP powders were ball-milled using ZrO₂ beads for 0-6 h in the IP6 solutions with concentrations from 0 to 10,000 ppm. The chelate-setting β-TCP cement with anti-washout property was successfully fabricated by mixing the β-TCP powder ball-milled in 3,000 ppm IP6 solution for 3 h and 2.5 mass% Na₂HPO₄ solution, and compressive strength of the cement was 13.4 ± 0.8 MPa. An in vivo study revealed that the above cement was directly in contact with host and newly formed bones without fibrous tissue layers, and was resorbed by osteoclast-like cells on the surface of the cement. The chelate-setting β-TCP cement with anti-washout property is promising for application as a novel injectable artificial bone with both biodegradability and osteoconductivity.

Mechanical properties' improvement of a tricalcium phosphate scaffold with poly-l-lactic acid in selective laser sintering

To improve the mechanical properties of a scaffold fabricated via selective laser sintering (SLS), a small amount (0.5–3 wt%) of poly-l-lactic acid (PLLA) is added to the β-tricalcium phosphate (β-TCP) powder. The fracture toughness of the scaffold prepared with the mixture powder containing 1 wt% PLLA increases by 18.18% and the compressive strength increases by 4.45% compared to the scaffold prepared from the β-TCP powder. The strengthening and toughening is related to the enhancement of β-TCP sintering characteristics via introducing a transient liquid phase in SLS. Moreover, the microcracks caused by the volume expansion due to the β–α phase transformation of TCP are reduced because of the PLLA inhibition function on the phase transformation. However, PLLA additive above 1 wt% would lead to a PLLA residue which will decrease the mechanical properties. The experimental results show that PLLA is an effective sintering aid to improve the mechanical properties of a TCP scaffold.

Dissolution properties of different compositions of biphasic calcium phosphate bimodal porous ceramics following immersion in simulated body fluid solution

Biphasic calcium phosphate (BCP) bimodal porous ceramics were prepared from a mixture of fine powders of hydroxyapatite (HAp) and beta-tricalcium phosphate (β-TCP) with varying HAp/β-TCP ratios. Two types of HAp powders and one type of β-TCP powder were used to produce porous BCP bioceramics with HAp/β-TCP weight ratios of 20/80, 40/60, and 80/20. Dissolution tests were performed to compare the dissolution properties of BCP-based bioceramics with different structural properties. Porous ceramic samples of approximately 0.5 g were individually soaked in 30 ml of simulated body fluid (SBF) solution at 36.5 °C for 1, 3, 7 and 10 days, respectively. The calcium content of the SBF solution was analyzed by ICP. The porous bodies were filtered, dried, and characterized using SEM, XRD, and FT-IR. The results indicate that the sample structural properties seem to have a greater effect than the storage environment on the dissolution properties.

Processing and properties of biphasic calcium phosphates bioceramics obtained by pressureless sintering and hot isostatic pressing

Abstract Calcium phosphate powders were obtained from coprecipitation method using diammonium phosphate and calcium nitrate solutions. The adjustment of experimental parameters and Ca/P initial ratio allowed synthesizing stoichiometric HA and β-TCP powders and four biphasic calcium phosphates (BCP) with compositions equal to 20/80, 40/60, 60/40, 80/20, of HA and TCP respective in mass. Two sintering techniques, pressureless sintering and hot isostatic pressing (HIP) were performed to compare the sinterability of the stoichiometric and biphasic compounds. By pressureless sintering, densities higher than 98% were obtained. Results illustrate the negative impact of hydroxyapatite on the densification of BCP but its benefit effect on grain growth inhibition. After HIP treatment, transparent ceramics were obtained. The mechanical behavior of these fully densified compounds was examined in order to determine the role of the chemical composition on mechanical properties.

10511 MgO添加HA/β-TCP複合材料の作製と力学的及び構造特性評価(OS2-3【バイオエンジニアリング(3)】)

Bioactive ceramics attracts attentions as materials of the bone implant, because of their high biocompatibility. For example, hydroxyapatite (HA) has bone-bonding ability, and β-tricalcium phosphate (P-TCP) has a high bioresorbability in body environment. In this study, HA/β-TCP composites with different content of β-TCP (0,10,20,30wt%) were prepared by wet mixing of HA and β-TCP powder, compaction of the powders and sintering. Pressureless sintering and spark plasma sintering were employed in this study. To improve sinterability of HA/β-TCP composites, the effect of additive of MgO was investigated. It was found that MgO improved sinterability of only P-TCP. Spark plasma sintering improved sinterability compared to pressureless sintering. As a result of X-ray powder diffraction measurement, it was found that MgO inhibited the change of β-TCP structure in case of pressureless sintering, but not in case of spark plasma sintering.

Strong bioresorbable Ca phosphate-PLA nanocomposites with uniform phase distribution by attrition milling and high pressure consolidation

Highly dense bioresorbable Ca-deficient HA–PLA (CDHA–PLA) and β-TCP–PLA nanocomposite materials with high (up to 80vol%) contents of the calcium phosphate (CaP) phase and homogeneous phase distribution were prepared via attrition milling followed by high pressure consolidation at ambient temperature. The microstructure and mechanical properties of the materials obtained were studied as a function of milling time and PLA amount. Attrition milling resulted in disintegration of β-TCP powder agglomerates down to 50–150nm, disintegration of CDHA agglomerates and refinement of 15×150nm2 CDHA nanoparticles to a size of 8×20nm2, and in a uniform distribution of the polymer component. Very high compressive strengths up to 400MPa and high bending strengths up to 70MPa were obtained. For both β-TCP and CDHA-based nanocomposites, the strength characteristics increased with milling time and decreased with increasing PLA content. For CDHA-based nanocomposites, attrition milling resulted in decrease of ductility while for β-TCP-40vol% PLA the ductility increased. The observed behavior may be a result of formation of homogeneous, relatively thick (tens of nanometers), ductile PLA layers in β-TCP—PLA nanocomposites, but very thin (several nanometers) PLA layers in attrition milled CDHA–PLA nanocomposites. Degradation of compressive and bending strength in aqueous solutions was observed for all the studied CaP–PLA nanocomposites.