Calcium Phosphate Powders Research Articles

A Study of BMP-2-Loaded Bipotential Electrolytic Complex around a Biphasic Calcium Phosphate-Derived (BCP) Scaffold for Repair of Large Segmental Bone Defect.

A bipotential polyelectrolyte complex with biphasic calcium phosphate (BCP) powder dispersion provides an excellent option for protein adsorption and cell attachment and can facilitate enhanced bone regeneration. Application of the bipotential polyelectrolyte complex embedded in a spongy scaffold for faster healing of large segmental bone defects (LSBD) can be a promising endeavor in tissue engineering application. In the present study, a hollow scaffold suitable for segmental long bone replacement was fabricated by the sponge replica method applying the microwave sintering process. The fabricated scaffold was coated with calcium alginate at the shell surface, and genipin-crosslinked chitosan with biphasic calcium phosphate (BCP) dispersion was loaded at the central hollow core. The chitosan core was subsequently loaded with BMP-2. The electrolytic complex was characterized using SEM, porosity measurement, FTIR spectroscopy and BMP-2 release for 30 days. In vitro studies such as MTT, live/dead, cell proliferation and cell differentiation were performed. The scaffold was implanted into a 12 mm critical size defect of a rabbit radius. The efficacy of this complex is evaluated through an in vivo study, one and two month post implantation. BV/TV ratio for BMP-2 loaded sample was (42±1.76) higher compared with hollow BCP scaffold (32±0.225).

Spark Plasma Sintering of Titanium Alloys for Biomedical Applications

A dense Ti6Al4V with a porous cp2-Ti surface layer was produced by Spark Plasma Sintering, using a Calcium Phosphate powder as space holder. The duplex porosity structure resulting from the space holder (large pores) and the uncompleted densification of the titanium powder (micrometric pores) has a very positive effect on both cell in-growth and cell proliferation.The porous structure decreases the fatigue resistance significantly, even if less than what reported in literature, likely due to the formation of a globular microstructure in the interface region of the substrate, where fatigue crack nucleation occurs. The porous surfaced specimens succeeded the adhesion by pull-off test, the resistance to static and cyclic shear stresses and the Taber abrasion test.

Ceramics based on calcium phosphate powder synthesized from calcium saccharate and ammonium hydrophosphate

A microporous ceramic with a pore size ranging from 1 to 6 μm and a relative density up to 56% was obtained from the calcium phosphate powder synthesized from aqueous solutions of monocalcium saccharate (CaC12H22O11) and ammonium hydrophosphate. The composition of the synthesized nanosized powder is found to include hydroxyapatite and sucrose. The phase composition of the ceramic after calcination in the range from 900 to 1200°C is represented by β-tricalcium phosphate and hydroxyapatite. The resulting ceramic material can be recommended for the manufacture of bone implants.

Insights on the properties of levofloxacin-adsorbed Sr- and Mg-doped calcium phosphate powders.

Several types of biodegradable materials have been investigated for the treatment of osteomyelitis. Calcium phosphate (CaP) ceramics are among the most performing materials due to their resemblance to human hard tissues in terms of mineralogical composition, and proven ability to adsorb and deliver a number of drugs. This research work was intended to study the suitability of modified CaP powders loaded with a fluoroquinolone as drug delivery systems for osteomyelitis treatment. Levofloxacin (LEV) was chosen due to the well-recognized anti-staphylococcal activity and adequate penetration into osteoarticular tissues. Substituted CaP powders (5mol% Sr(2+) or 5mol% Mg(2+)) were synthesised through aqueous precipitation. The obtained powders were characterised by X-ray diffraction, SEM and FTIR analysis. The X-ray diffraction patterns confirmed the presence of HA and β-tricalcium phosphates (β-TCP) phases in doped compositions, especially in the case of Mg-doped system. The fixation of LEV at the surface of the particles occurred only by physisorption. Both the in vitro microbiological susceptibility, against Staphylococcus spp, and biocompatibility of LEV-loaded CaP powders have not been compromised.

Thermally induced crystallization and phase evolution in powders derived from amorphous calcium phosphate precipitates with a Ca/P ratio of 1:1

Calcium phosphate powders of calcium pyrophosphate α1-CPP (the metastable phase of the high-temperature polymorph α-CPP) and the polymorph β-CPP (stable in this range), of α1-CPP, β-CPP, α1-TCP (metastable polymorph of the high-temperature phase α-tricalcium phosphate) and β-tricalcium phosphate β-TCP were prepared by heating amorphous calcium phosphate (ACP) precipitates with the nominal Ca/P ratio of 1:1 by nitrate synthesis. α1-CPP/β-CPP resulted from a crystallization at 530–640°C and subsequent heating to 980°C of unwashed and lyophilized ACP. α1-CPP/β-CPP/α1-TCP/β-TCP was formed by crystallization at 620–720°C, followed by heating of six-time washed and lyophilized ACP precipitates from an ultra-short synthesis. The activation energy for the crystallization of ACP to α1-CPP was determined with 165kJmol−1. The reason for the occurrence of the TCP phases (Ca/P ratio=1.5) from ACP (Ca/P ratio=1) is discussed. The powders are prospective biomaterials for bone substitution because they combine effective bioactive phases with the metastable polymorphs α1-CPP and α1-TCP.

Is there a relationship between solubility and resorbability of different calcium phosphate phases in vitro?

BackgroundDoes chemistry govern biology or it is the other way around - that is a broad connotation of the question that this study attempted to answer. MethodComparison was made between the solubility and osteoclastic resorbability of four fundamentally different monophasic calcium phosphate (CP) powders with monodisperse particle size distributions: alkaline hydroxyapatite (HAP), acidic monetite (DCP), β-calcium pyrophosphate (CPP), and amorphous CP (ACP). Results With the exception of CPP, the difference in solubility between different CP phases became neither mitigated nor reversed, but augmented in the resorptive osteoclastic milieu. Thus, DCP, a phase with the highest solubility, was also resorbed more intensely than any other CP phase, whereas HAP, a phase with the lowest solubility, was resorbed least. CPP becomes retained inside the cells for the longest period of time, indicating hindered digestion of only this particular type of CP. Osteoclastogenesis was mildly hindered in the presence of HAP, ACP and DCP, but not in the presence of CPP. The most viable CP powder with respect to the mitochondrial succinic dehydrogenase activity was the one present in natural biological bone tissues: HAP. ConclusionChemistry in this case does have a direct effect on biology. Biology neither overrides nor reverses the chemical propensities of inorganics with which it interacts, but rather augments and takes a direct advantage of them. SignificanceThese findings set the fundamental basis for designing the chemical makeup of CP and other biosoluble components of tissue engineering constructs for their most optimal resorption and tissue regeneration response.

Multi-loaded ceramic beads/matrix scaffolds obtained by combining ionotropic and freeze gelation for sustained and tuneable vancomycin release

For a targeted release against bacteria-associated bone diseases (osteomyelitis) ceramic beads with a high drug loading capacity, loaded with vancomycin as model antibiotic, are synthesized as drug carrier and successfully incorporated in an open porous hydroxyapatite matrix scaffold via freeze gelation to prevent bead migration at the implantation site and to extend drug release. We demonstrate that the quantity of loaded drug by the hydroxyapatite and β-tricalcium phosphate beads, produced by ionotropic gelation, as well as drug release can be tuned and controlled by the selected calcium phosphate powder, sintering temperature, and high initial vancomycin concentrations (100mg/ml) used for loading. Bead pore volume up to 68mm3/g, with sufficiently large open pores (pore size of up to 650nm with open porosity of 72%) and high surface area (91m2/g) account likewise for a maximum drug loading of 236mg/g beads or 26mg/sample. Multi-drug loading of the beads/matrix composite can further increase the maximum loadable amount of vancomycin to 37mg/sample and prolong release and antibacterial activity on Bacillus subtilis up to 5days. The results confirmed that our approach to incorporate ceramic beads as drug carrier for highly increased drug load in freeze-gelated matrix scaffolds is feasible and may lead to a sustained drug release and antibacterial activity.

A Simple Approach for an Eggshell-Based 3D-Printed Osteoinductive Multiphasic Calcium Phosphate Scaffold

Natural origin bioceramics are widely used for bone grafts. In the present study, an eggshell-derived bioceramic scaffold is fabricated by 3D printing as a potential bone-graft analogue. The eggshell, a biological waste material, was mixed with a specific ratio of phosphoric acid and chitosan to form a precursor toward the fabrication of an osteoinductive multiphasic calcium phosphate scaffold via a coagulation-assisted extrusion and sintering for a multiscalar hierarchical porous structure with improved mechanical properties. Physicochemical characterization of the formed scaffolds was carried out for phase analysis, surface morphology, and mechanical properties. A similar scaffold was prepared using a chemically synthesized calcium phosphate powder that was compared with the natural origin one. The higher surface area associated with the interconnected porosity along with multiple phases of the natural origin scaffold facilitated higher cell adhesion and proliferation compared to the chemically synthesized one. Further, the natural origin scaffold displayed relatively higher cell differentiation activity, as is evident by protein and gene expression studies. On subcutaneous implantation for 30 days, promising vascular tissue in-growth was observed, circumventing a major foreign body response. Collagen-rich vascular extracellular matrix deposition and osteocalcin secretion indicated bonelike tissue formation. Finally, the eggshell-derived multiphasic calcium phosphate scaffold displayed improvement in the mechanical properties with higher porosity and osteoinductivity compared to the chemically derived apatite and unveiled a new paradigm for utilization of biological wastes in bone-graft application.

EFFECT OF SEVERAL CALCINATION TEMPERATURE ON DIFFERENT CONCENTRATION ZINC SUBSTITUTED CALCIUM PHOSPHATE CERAMICS

Zinc substituted calcium phosphate ceramics powders were produced from precipitation method using calcium nitrate, zinc nitrate and ammonium dihydrogen phosphate solutions. Several zinc ions concentrations (5, 10, and 15 mole %) were substituted into calcium phosphate ceramics with the (Ca+Zn)/P initial ratio were set to 1.67. Calcium phosphate powders were then calcined at 600, 700, 800, 900, and 1000°C to observe its effect on the material phase behavior. By increasing the calcination temperature, XRD peaks changed from broad to narrower shape indicating that the powders are highly crystalline. Hydroxyapatite (HA) partly transformed to another phase which is tricalcium phosphate (β-TCP) at 700°C confirming the formation of biphasic calcium phosphate ceramics. FESEM observations clearly exhibit that the particles are in nanosized scale which explains why as zinc concentration increases, the particles tend to be agglomerated.

Brushite-based calcium phosphate cement with multichannel hydroxyapatite granule loading for improved bone regeneration.

In this work, we report brushite-based calcium phosphate cement (CPC) system to enhance the in vivo biodegradation and tissue in-growth by incorporation of micro-channeled hydroxyapatite (HAp) granule and silicon and sodium addition in calcium phosphate precursor powder. Sodium- and silicon-rich calcium phosphate powder with predominantly tri calcium phosphate (TCP) phase was synthesized by an inexpensive wet chemical route to react with mono calcium phosphate monohydrate (MCPM) for making the CPC. TCP nanopowder also served as a packing filler and moderator of the reaction kinetics of the setting mechanism. Strong sintered cylindrical HAp granules were prepared by fibrous monolithic (FM) process, which is 800 µm in diameter and have seven micro-channels. Acid sodium pyrophosphate and sodium citrate solution was used as the liquid component which acted as a homogenizer and setting time retarder. The granules accelerated the degradation of the brushite cement matrix as well as improved the bone tissue in-growth by permitting an easy access to the interior of the CPC through the micro-channels. The addition of micro-channeled granule in the CPC introduced porosity without sacrificing much of its compressive strength. In vivo investigation by creating a critical size defect in the femur head of a rabbit model for 1 and 2 months showed excellent bone in-growth through the micro-channels. The granules enhanced the implant degradation behavior and bone regeneration in the implanted area was significantly improved after two months of implantation.

Thermal Analysis on Dehydroxylation of Sol-Gel Derived Zinc Doped Calcium Phosphate Powders

The dehydroxylation of Zn free and 4 mol% Zn CaP powder was investigated using thermogravimetric analysis over the range of room temperature to 1200 °C. The kinetic result of dehydroxylation of Zn free and 4 mol% Zn CaP was calculated by means of the Ozawa–Flynn–Wall method. The XRD result indicated that the amount of Zn incorporated in HA lattice influences the phase stability of HA as it decreases with an increase in Zn concentration. According to calculated activation energy and conversion degree, the kinetics of HA dehydroxylation was identified, which included four successive conversion stages kinetically controlled by different rate-controlling processes. The dehydroxylation analysis of TG/DTG data show that Zn incorporation in HA lattice influences the phase stability of HA.

Fabrication and Sintering Behavior of Zinc-Doped Biphasic Calcium Phosphate Bioceramics

Dense bioceramics with improved mechanical properties have been prepared using sol–gel derived zinc doped biphasic calcium phosphate (BCP) powders. Zinc concentration was varied in the range of 0,1, 2, 4, 5, 10, and 15 mol%. The compaction of the powders followed by sintering provided the dense ceramics. The effects of zinc concentration doped and sintering temperature on phase stability and mechanical characteristics were examined. The presence of Zn changed the phase of dense BCP, leading to improved mechanical properties. Zn free BCP attained the highest density of only 92.6% after 1400°C sintering, equally achieved by 4 mol% Zn-doped BCP at a lower temperature of 1200°C. It is presumed that the steady increase in the compact density up to 4 mol% zinc incorporation was contributed by progressive consolidation in the BCP structure, but the density dropped again from 5 mol% until 15 mol% due to low density β-tricalcium phosphate phase formation. This study showed that Zn doping was effective in producing high strength dense BCP with 3.40 GPa hardness and 1.43 MPa · m1/2 fracture toughness.

Editorial on the original article entitled "3D printing of composite calcium phosphate and collagen scaffolds for bone regeneration" published in the Biomaterials on February 14, 2014.

The paper entitled "3D printing of composite calcium phosphate and collagen scaffolds for bone regeneration" published in the Biomaterials recently illuminated the way to make particular scaffolds with calcium phosphate (CaP) powder, phosphoric acid, type I collagen and Tween 80 in low temperature. After the optimal concentration of each component was determined, the scaffolds were evaluated in a critically sized murine femoral defect model and exhibited good material properties. We made some related introduction of materials applied in 3D printing for bone tissue engineering based on this article to demonstrate the current progress in this field of study.

Synthesis and characterization of Ag-containing calcium phosphates with various Ca/P ratios.

Ag-containing calcium phosphate (CaP) powders were synthesized by a precipitation method using aqueous solutions of calcium nitrate, silver nitrate, and ammonium phosphate. The powders were sintered at temperatures ranging from 1173 to 1473 K. The charged atomic ratios of (Ca+Ag)/P and Ag/(Ca+Ag) in solution were varied from 1.33 to 1.67 and from 0 to 0.30, respectively. The Ag content in the as-precipitated CaP powders increased with the charged Ag/(Ca+Ag) atomic ratio in solution and was lower than the charged Ag/(Ca+Ag) value. The as-precipitated CaP powders consisted of hydroxyapatite (HA) as the main phase. Ag nanoparticles were observed on the as-precipitated HA particles under all conditions of Ag addition. After the sintering, HA, β-TCP (tricalcium phosphate), α-TCP, and β-CPP (calcium pyrophosphate) were mainly detected as CaPs on the basis of the Ca/P atomic ratio of the as-precipitated powders. The addition of Ag stabilized the β-TCP phase, and the distribution of Ag in β-TCP was homogeneous. A metallic Ag phase coexisted with HA. The solubility of Ag in HA was estimated to be 0.0019-0.0061 (Ag/(Ca+Ag)) atomic ratio, which was lower than that in β-TCP (higher than 0.0536) and higher than that of β-CPP (below the detection limit of analyses).

Flame‐made Calcium Phosphate/Carbonate Nanopowders for Nutrition

Background: Nanostructured calcium phosphate (CaP) and carbonate (CaCO3) powders may be well absorbed in humans because of their high specific surface area (SSA). The material properties of these p...

Biologic potential of calcium phosphate biopowders produced via decomposition combustion synthesis

The aim of this research was to evaluate the biologic potential of calcium phosphate (CaP) biopowders produced with a novel reaction synthesis system. Decomposition combustion synthesis (DCS) is a modified combustion synthesis method capable of producing CaP powders for use in bone tissue engineering applications. During DCS, the stoichiometric ratio of reactant salt to fuel was adjusted to alter product chemistry and morphology. In vitro testing methods were utilized to determine the effects of controlling product composition on cytotoxicity, proliferation, biocompatibility and biomineralization. In vitro, human fetal osteoblasts (ATCC, CRL-11372) cultured with CaP powder displayed a flattened morphology, and uniformly encompassed the CaP particulates. Matrix vesicles containing calcium and phosphorous budded from the osteoblast cells. CaP powders produced via DCS are a source of biologically active, synthetic, bone graft substitute materials.

Development of nanosilica bonded monetite cement from egg shells.

This work represents further effort from our group in developing monetite based calcium phosphate cements (CPC). These cements start with a calcium phosphate powder (MW-CPC) that is manufactured using microwave irradiation. Due to the robustness of the cement production process, we report that the starting materials can be derived from egg shells, a waste product from the poultry industry. The CPC were prepared with MW-CPC and aqueous setting solution. Results showed that the CPC hardened after mixing powdered cement with water for about 12.5±1 min. The compressive strength after 24h of incubation was approximately 8.45±1.29 MPa. In addition, adding colloidal nanosilica to CPC can accelerate the cement hardening (10±1 min) process by about 2.5 min and improve compressive strength (20.16±4.39 MPa), which is more than double the original strength. The interaction between nanosilica and CPC was monitored using an environmental scanning electron microscope (ESEM). While hardening, nanosilica can bond to the CPC crystal network for stabilization. The physical and biological studies performed on both cements suggest that they can potentially be used in orthopedics.

The role of shell/core saturation level on the accuracy and mechanical characteristics of porous calcium phosphate models produced by 3Dprinting

Purpose– This paper aims to study the influence of the binder saturation level on the accuracy and on the mechanical properties of three-dimensional (3D)-printed scaffolds for bone tissue engineering.Design/methodology/approach– To study the influence of the liquid binder volume on the models accuracy, two quality test plates with different macropore sizes were designed and produced. For the mechanical and physical characterisation, cylindrical specimens were used. The models were printed using a calcium phosphate powder, which was characterised in terms of composition, particle size and morphology, by X-ray diffraction (XRD), laser diffraction and Scanning electron microscopy (SEM) analysis. The sample’s physical characterisation was made using the Archimedes method (porosity), SEM, micro-computer tomography (CT) and digital scan techniques, while the mechanical characterisation was performed by means of uniaxial compressive tests. Strength distribution was analysed using a statistical Weibull approach, and the dependence of the compressive strength on the porosity was discussed.Findings– The saturation level is determinant for the structural characteristics, accuracy and strength the models produced by three-dimensional printing (3DP). Samples printed with the highest saturation showed higher compressive strengths (24 MPa), which are over the human trabecular bone. The models printed with lower saturations presented the highest accuracy and pore interconnectivity.Originality/value– This study allowed to acquire important knowledge concerning the effects of shell/core saturation on the overall performance of the 3DP. With this information it is possible to devise scaffolds with the required properties for bone scaffold engineering.

Physical Properties of Calcium Phosphate-Alumina Bio ceramics as Dental Implants

In order to perform new dental implant, we carried out investigations on α-alumina and calcium phosphate based composites. α-Alumina nano-powder were synthesized using reverse micelle method while calcium phosphate nano-powders with different molar ratio starting from 1.8 to 1.1 were synthesized by precipitation method, using calcium nitrate (Ca(NO3)2.4H2O) and ammonium hydrogen orthophosphate (NH4H2PO4) as precursor materials as source for calcium (Ca²+) and phosphate ((PO4)3-) ions respectively. Samples of respectively 5, 10 and 20% weight of Calcium phosphate powder were mixed with alumina, consolidated and sintered at 1400°C for 4 hours. The synthesized composites, in form of pellets were characterized for bulk density, apparent porosity, hardness and flexural strength properties.

Elaboration biphasic calcium phosphate nanostructured powders

Nanostructured calcium phosphate and biphasic calcium phosphates have been studied and stand out as biomaterials for bone regeneration. This is due to the fact that thesebiomaterials present bioactivity and morphological, chemical and crystallographic similarities to the bone apatite. The aim of the present work has been the synthesis and characterization of two calcium phosphates with Ca/P=1.5 e 1.67 as molar ratio. These were synthesized through the chemical wet process. After synthesis, the hydrated calcium phosphate powders were subsequently calcined at temperatures of 900°C/2h providing b-calcium phosphate (b-TCP) and hydroxyapatite (HA) powders. These powders were used to elaborate the biphasic powders in the wt.% ratios HA/b-TCP as follows: 80/20, 20/80, 70/30 and 30/70. The method used for the elaboration of the b-tricalcium phosphate nanostructured powder, hydroxyapatite and biphasic compositions was the attrition milling. The nanostructured powders obtained were characterized by the scanning electron microscopy technique, X-ray diffractometry. Infrared spectroscopy and Specific surface using BET model.