Macroporous Calcium Research Articles

Hydroxyapatite-loaded macroporous calcium alginate hydrogels: Preparation, characterization, and in vitro evaluation.

Hydrogels from natural polysaccharides are of great interest for tissue engineering. This study aims (1) to prepare hydroxyapatite-loaded macroporous calcium alginate hydrogels by novel one-step technique using internal gelation in water-frozen solutions; (2) to evaluate their physicochemical properties; (3) to estimate their ability to support cell growth and proliferation in vitro. The structure of the hydrogel samples in a swollen state was studied by confocal laser scanning microscopy and was shown to represent a system of interconnected macropores with sizes of tens micron. The swelling behavior of the hydrogels, their mechanical properties (Young's moduli) in function of a hydroxyapatite content (5-30 mass%) were studied. All hydrogel samples loaded with hydroxyapatite were found to support growth and proliferation of mouse fibroblasts (L929) at long-term cultivation for 7 days. The obtained macroporous composite Ca-Alg-HA hydrogels could be promising for tissue engineering.

Mechanical Properties of Graded Macroporous Calcium Phosphate Ceramics of Tailored Architecture

Mechanical Properties of Graded Macroporous Calcium Phosphate Ceramics of Tailored Architecture

Fabrication of Radio-Opaque and Macroporous Injectable Calcium Phosphate Cement.

The aim of this work was the development of injectable radio-opaque and macroporous calcium phosphate cement (CPC) to be used as a bone substitute for the treatment of pathologic vertebral fractures. A CPC was first rendered radio-opaque by the incorporation of zirconium dioxide (ZrO2). In order to create macroporosity, poly lactic-co-glycolic acid (PLGA) microspheres around 100 μm were homogeneously incorporated into the CPC as observed by scanning electron microscopy. Physicochemical analyses by X-ray diffraction and Fourier transform infrared spectroscopy confirmed the brushite phase of the cement. The mechanical properties of the CPC/PLGA cement containing 30% PLGA (wt/wt) were characterized by a compressive strength of 2 MPa and a Young's modulus of 1 GPa. The CPC/PLGA exhibited initial and final setting times of 7 and 12 min, respectively. Although the incorporation of PLGA microspheres increased the force necessary to inject the cement and decreased the percentage of injected mass as a function of time, the CPC/PLGA appeared fully injectable at 4 min. Moreover, in comparison with CPC, CPC/PLGA showed a full degradation in 6 weeks (with 100% mass loss), and this was associated with an acidification of the medium containing the CPC/PLGA sample (pH of 3.5 after 6 weeks). A cell viability test validated CPC/PLGA biocompatibility, and in vivo analyses using a bone defect assay in the caudal vertebrae of Wistar rats showed the good opacity of the CPC through the tail and a significant increased degradation of the CPC/PLGA cement a month after implantation. In conclusion, this injectable CPC scaffold appears to be an interesting material for bone substitution.

Treatment of Critical Size Femoral Bone Defects with Biomimetic Hybrid Scaffolds of 3D Plotted Calcium Phosphate Cement and Mineralized Collagen Matrix.

To treat critical-size bone defects, composite materials and tissue-engineered bone grafts play important roles in bone repair materials. The purpose of this study was to investigate the bone regenerative potential of hybrid scaffolds consisting of macroporous calcium phosphate cement (CPC) and microporous mineralized collagen matrix (MCM). Hybrid scaffolds were synthetized by 3D plotting CPC and then filling with MCM (MCM-CPC group) and implanted into a 5 mm critical size femoral defect in rats. Defects left empty (control group) as well as defects treated with scaffolds made of CPC only (CPC group) and MCM only (MCM group) served as controls. Eight weeks after surgery, micro-computed tomography scans and histological analysis were performed to analyze the newly formed bone, the degree of defect healing and the activity of osteoclasts. Mechanical stability was tested by 3-point-bending of the explanted femora. Compared with the other groups, more newly formed bone was found within MCM-CPC scaffolds. The new bone tissue had a clamp-like structure which was fully connected to the hybrid scaffolds and thereby enhanced the biomechanical strength. Together, the biomimetic hybrid MCM-CPC scaffolds enhanced bone defect healing by improved osseointegration and their differentiated degradation provides spatial effects in the process of critical-bone defect healing.

Stereolithography 3D printed calcium pyrophosphate macroporous ceramics for bone grafting

Macroporous calcium pyrophosphate ceramics with a pore size of 900 μm and a pore fraction of up to 65% demonstrating compressive strength of 5 ± 1 MPa were formed by DLP stereolithography 3D printing. Mixed sodium-calcium pyrophosphate CaNa2P2O7 was used as an eutectic additive in liquid phase sintering of the ceramics at 600–800 °C. Initial powder charge was selected from a mixture of Ca10(PO4)6(OH)2, Ca(H2PO4)2·H2O and NaH2PO4. The pH of the aqueous solution contacting with the manufactured pyrophosphate ceramics in the range (6–7.2) turns out to be acceptable for further biomedical tests as a bone grafting material.

Biomimetic versus sintered macroporous calcium phosphate scaffolds enhanced bone regeneration and human mesenchymal stromal cell engraftment in calvarial defects

In contrast to sintered calcium phosphates (CaPs) commonly employed as scaffolds to deliver mesenchymal stromal cells (MSCs) targeting bone repair, low temperature setting conditions of calcium deficient hydroxyapatite (CDHA) yield biomimetic topology with high specific surface area. In this study, the healing capacity of CDHA administering MSCs to bone defects is evaluated for the first time and compared with sintered beta-tricalcium phosphate (β-TCP) constructs sharing the same interconnected macroporosity. Xeno-free expanded human bone marrow MSCs attached to the surface of the hydrophobic β-TCP constructs, while infiltrating the pores of the hydrophilic CDHA. Implantation of MSCs on CaPs for 8 weeks in calvaria defects of nude mice exhibited complete healing, with bone formation aligned along the periphery of β-TCP, and conversely distributed within the pores of CDHA. Human monocyte-osteoclast differentiation was inhibited in vitro by direct culture on CDHA compared to β-TCP biomaterials and indirectly by administration of MSC-conditioned media generated on CDHA, while MSCs increased osteoclastogenesis in both CaPs in vivo. MSC engraftment was significantly higher in CDHA constructs, and also correlated positively with bone in-growth in scaffolds. These findings demonstrate that biomimetic CDHA are favorable carriers for MSC therapies and should be explored further towards clinical bone regeneration strategies. Statement of significanceDelivery of mesenchymal stromal cells (MSCs) on calcium phosphate (CaP) biomaterials enhances reconstruction of bone defects. Traditional CaPs are produced at high temperature, but calcium deficient hydroxyapatite (CDHA) prepared at room temperature yields a surface structure more similar to native bone mineral. The objective of this study was to compare the capacity of biomimetic CDHA scaffolds with sintered β-TCP scaffolds for bone repair mediated by MSCs for the first time. In vitro, greater cell infiltration occurred in CDHA scaffolds and following 8 weeks in vivo, MSC engraftment was higher in CDHA compared to β-TCP, as was bone in-growth. These findings demonstrate the impact of material features such as surface structure, and highlight that CDHA should be explored towards clinical bone regeneration strategies.

Histological Assessment of Injectable Macro-porous Calcium Phosphate Cement (CPC) Versus Autogenous Bone Graft on Healing of Osseous Defect (Experimental Animal Study)

Objective: The aim of this study is to evaluate histologically the healing potential of injectable macro-porous Calcium Phosphate Cement and autogenous bone. (Normal bone healing) on surgically induced bone defect on femur bone of rabbit. Materials and Methods: Twelve adult white male New Zealand rabbits were selected for this study. Rabbits were divided into two groups and the two groups according to a two evaluation periods divided into 2 subgroups. Rabbits were anesthetized with intramuscular anethesia, and two osseous defects had been created in the distal aspect of the femur bone.one of this defects injected by a grafting material (SI-HPMC CPC) and the other left empty as control (normal healing).Animal were sacrificed after two sacrifice dates and the femur bone excised for histological and statistical evaluation.esults: Rabbits from each group were sacrificed after 2 and 4 weeks. The femur bone containing the induced defect was dissected. Each femur bone was excised using hard tissue microtome. Each slice was then fixed in 10% neutral buffered formalin. The formalin-fixed bone samples were decalcified in 15% buffered formic acid solution and processed for routine histological examination using hematoxylin and eosin stain under light microscope.. Conclusion: According to our results in the present study, we can consider Si-HPMC CPC a viable alternative to the autogenous bone in the healing of osseous bone defects . In the present study, the new and simple method to prepare macroporous CPCs using Si-HPMC a foaming agent in connected syringe , result

Macroporous Calcium Phosphate Matrices Prepared Using the Technology of Self-Setting Cements

Macroporous Calcium Phosphate Matrices Prepared Using the Technology of Self-Setting Cements

Relationship between the Porous Structure Hierarchy and the Physical and Mechanical Properties of Calcium Phosphate Drug Carriers

A relationship between the structural-morphological and physical-mechanical properties of macro-porous calcium phosphate (CaP) coatings on the surface of titanium implants is studied. The produced CaP coatings can be used as carriers for target drug delivery in biomedical applications. The regularities of the formation of bulk (thickness of 15–130 μm) and rough (Ra = 1.7–8.5 μm) CaP coatings deposited by the micro-arc oxidation (MAO) method are studied. The coatings have a hierarchical porous structure and a uniform distribution of the structural elements (spheres and pores) over the surface. Correlations between the value of the applied voltage and structural-morphological and physical-mechanical characteristics of the CaP coatings have been established. The value of the coating adhesion strength has been determined with tensile tests. Both cohesive and mixed adhesive-cohesive pull-off of the MAO coating from the substrate have been identified.

Colloidal forming of macroporous calcium pyrophosphate bioceramics in 3D-printed molds

A technique for colloidal forming of Ca2P2O7 macroporous bioceramics, based on low-pressure injection molding (LPIM) of a glycerol-water slip containing Ca2P2O7 and Ca(Н2PO4)2 into a plastic mold fabricated via FDM 3D-printing, was proposed. Chemical reaction between the solid phases of the water containing slip - Ca2P2O7 and Ca(Н2PO4)2, resulting in brushite (CaHPO4·2H2O) formation, led to consolidation of the casting and preserved its complex architecture in the course of mold burning-out. Macroporous ceramics of Kelvin structure (70% macropores with the sizes from 2 up to 4 mm), based on a pre-defined composition with 10 wt% Ca(PO3)2 and sintered in liquid-phase regime, demonstrated a compressive strength of 1.4 ± 0.1 MPa at a density of 22 ± 2%. In vitro tests on bioactivity in SBF solution, as well as on resorption of the ceramics in model solution of citric acid, were carried out.

Digital Light Processing of Freeze-cast Ceramic Layers for Macroporous Calcium Phosphate Scaffolds with Tailored Microporous Frameworks.

The objective of the present study is to demonstrate the versatility of the digital light processing (DLP) technique particularly when using a freeze-cast ceramic layer as the feedstock, which can manufacture porous calcium phosphate (CaP) scaffolds with arbitrarily designed macroporous structures with tailored microporous frameworks specially designed for bone scaffold applications. For this goal, we employed camphene-camphor as the freezing vehicle and porogen for the preparation of photocurable CaP suspensions containing diurethane dimethacrylate (UDMA) monomers. After freeze-casting, the CaP suspensions could be solidified at controlled temperatures (~33–38 °C) and then be photopolymerized by DLP. All produced CaP scaffolds fairly resembled the designed macroporous structures (the gyroid structure with two interpenetrating macropore networks). In addition, numerous micropores were created in the CaP filaments, while the microporosity increased with increasing the camphene-camphor amount from 40 vol % to 60 vol %. As a consequence, compressive strength and modulus of hierarchically porous CaP scaffolds decreased due to an increase in overall porosity. However, reasonable mechanical properties could be obtained at high porosities owing to the CaP frameworks constructed in a periodic manner. In addition, excellent water penetration capability, biocompatibility, and apatite-forming ability were obtained, which were attributed to the microporous CaP frameworks with good pore interconnectivity and large surface area.

Comparative evaluation of the osteogenic capacity of human mesenchymal stem cells from bone marrow and umbilical cord tissue.

Mesenchymal stem cells (MSCs) have been extensively investigated in the field of regenerative medicine. Human bone MSCs (BMSCs) have become a common type of seed cell for bone tissue engineering. However, the viability and cell number of BMSCs are negatively correlated with donor age, and as the extraction process is painful, this method has not been widely used. As human umbilical cord MSCs (UCMSCs) may be harvested inexpensively and inexhaustibly, the present study evaluated and compared the regenerative potential of UCMSCs and BMSCs to determine whether UCMSCs may be used as a novel cell type for bone regeneration. In the present study, the proliferation and osteogenic capacity of BMSCs and UCMSCs was compared in vitro. BMSCs and UCMSCs were respectively combined with biofunctionalized macroporous calcium phosphate cement, and their bone regenerative potentials were determined by investigating their capacity for ectopic bone formation in a nude mouse model as well as their efficacy in a rat model of tibia bone defect. The extent of bone regeneration was examined by X-ray, histological and immunohistochemical analyses. The results revealed that UCMSCs exhibited a good osteogenic differentiation potential, similarly to that of BMSCs, and that UCMSCs were able to contribute to the regeneration of bone and blood vessels. Furthermore, no significant differences were identified between BMSCs and UCMSCs in terms of their bone regenerative effect.

High-performance and low-cost macroporous calcium oxide based materials for thermochemical energy storage in concentrated solar power plants

High energy density, cycling stability, low cost and scalability are the main features required for thermochemical energy storage systems to achieve a feasible integration in Concentrating Solar Power plants (CSP). While no system has been found to fully satisfy all these requirements, the reversible CaO/CaCO3 carbonation reaction (CaL) is one of the most promising since CaO natural precursors are affordable and earth-abundant. However, CaO particles progressively deactivate due to sintering-induced morphological changes during repeated carbonation and calcinations cycles. In this work, we have prepared acicular calcium and magnesium acetate precursors using a simple, cost-effective and easily scalable technique that requires just the natural minerals and acetic acid, thereby avoiding expensive reactants and environmentally unfriendly solvents. Upon thermal decomposition, these precursors yield a stable porous structure comprised of well dispersed MgO nanoparticles coating the CaO/CaCO3 grains that is resistant to pore-plugging and sintering while at the same time exhibits high long term effective conversion. Process simulations show that the employment of these materials could significantly improve the overall CSP-CaL efficiency at the industrial level.

Removal of sulfide from aqueous solutions using novel alginate–iron oxide magnetic hydrogel composites

Magnetic hydrogel composite beads were prepared by impregnating iron oxide nanoparticles (NP) into macroporous calcium alginate gel (Alg) and used as an adsorbent (Alg/iron oxide-NP) for the removal of sulfide from aqueous solutions. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), X-ray diffraction (XRD) and Fourier transform infra-red (FTIR) spectroscopic analyses were performed to characterize the iron oxide nanoparticles and the Alg/iron oxide-NP for exploring the mechanism involved in sulfide removal. The experimental results showed that adsorption of sulfide on Alg/iron oxide-NP beads reached equilibrium within 3 h. At pH 7.5 and 25 °C, Alg/iron oxide-NP was capable of reducing sulfide concentration from 64.3 to 1.1 mg/L, thus achieving more than 98% removal. The removal of sulfide decreased with the increase in solution ionic strength. The equilibrium isotherm studies obeyed Langmuir model better than Freundlich model. The maximum uptake capacity was found to be 136.9 mg/g. Pseudo-second-order model described the kinetics of sulfide adsorption having rate constant 0.004 g mg−1 min−1. The proposed mechanism and the experimental data evidenced that chemical interaction was involved in adsorption wherein elemental sulfur and sulfates were produced as byproducts. The adsorbent was regenerated with calcium chloride solution. In five adsorption–desorption cycles, the adsorbent lost less than 5% of its removal efficiency. The magnetic property of the iron oxide nanoparticles enabled easy and rapid separation of the adsorbent from the solution via magnetic field. The synthesized magnetic composite had comparable if not superior adsorption capacity in comparison with carbon-based adsorbents.

Engineering human bone grafts with new macroporous calcium phosphate cement scaffolds.

Bone engineering opens the possibility to grow large amounts of tissue products by combining patient-specific cells with compliant biomaterials. Decellularized tissue matrices represent suitable biomaterials, but availability, long processing time, excessive cost, and concerns on pathogen transmission have led to the development of biomimetic synthetic alternatives. We recently fabricated calcium phosphate cement (CPC) scaffolds with variable macroporosity using a facile synthesis method with minimal manufacturing steps and demonstrated long-term biocompatibility in vitro. However, there is no knowledge on the potential use of these scaffolds for bone engineering and whether the porosity of the scaffolds affects osteogenic differentiation and tissue formation in vitro. In this study, we explored the bone engineering potential of CPC scaffolds with two different macroporosities using human mesenchymal progenitors derived from induced pluripotent stem cells (iPSC-MP) or isolated from bone marrow (BMSC). Biomimetic decellularized bone scaffolds were used as reference material in all experiments. The results demonstrate that, irrespective of their macroporosity, the CPC scaffolds tested in this study support attachment, viability, and growth of iPSC-MP and BMSC cells similarly to decellularized bone. Importantly, the tested materials sustained differentiation of the cells as evidenced by increased expression of osteogenic markers and formation of a mineralized tissue. In conclusion, the results of this study suggest that the CPC scaffolds fabricated using our method are suitable to engineer bone grafts from different cell sources and could lead to the development of safe and more affordable tissue grafts for reconstructive dentistry and orthopaedics and in vitro models for basic and applied research.

Bone regeneration in minipigs via calcium phosphate cement scaffold delivering autologous bone marrow mesenchymal stem cells and platelet-rich plasma.

Macroporous calcium phosphate cement (CPC) with stem cell seeding is promising for bone regeneration. The objective of this study was to investigate the effects of co-delivering autologous bone marrow mesenchymal stem cells (BMSCs) and autologous platelet-rich plasma (PRP) in CPC scaffold for bone regeneration in minipigs for the first time. Twelve female adult Tibet minipigs (12-18months old) were used. A cylindrical defect with 10mm height and 8mm diameter was prepared at the femoral condyle. Two bone defects were created in each minipig, one at each side of the femoral condyle. Three constructs were tested: (1) CPC scaffold (CPC control); (2) CPC seeded with BMSCs (CPC-BMSC); (3) CPC seeded with BMSCs and PRP (CPC-BMSC-PRP). Two time points were tested: 6 and 12weeks (n=4). Good integration of implant with surrounding tissues was observed in all groups. At 12weeks, the CPC-BMSC-PRP group had significantly less residual CPC remaining in the defect than the CPC-BMSC group and the CPC control (p<0.05). The residual CPC volume for the CPC-BMSC-PRP group was half that of the CPC control. New bone formation for CPC-BMSC-PRP was more than two-fold that of the CPC control (p<0.05). CPC-BMSC-PRP had new blood vessel density that was nearly two-fold that of the CPC control (p<0.05). In conclusion, CPC scaffold with autologous BMSC-PRP doubled the new bone regeneration and blood vessel density in minipigs compared with the CPC control. In the present study, the new macroporous CPC system with co-delivered BMSC-PRP has been shown to promote scaffold resorption and bone regeneration in large defects. Copyright © 2017 John Wiley & Sons, Ltd.

Macroporous Calcium Phosphate/Chitosan Composites Prepared via Unidirectional Ice Segregation and Subsequent Freeze-Drying.

Calcium phosphate chitosan-based composites have gained much interest in recent years for biomedical purposes. In this paper, three-dimensional calcium phosphate chitosan-based composites with different mineral contents were produced using a green method called ice segregation induced self-assembly (ISISA). In this methodology, ice crystals were used as a template to produce porous structures from an aqueous solution of chitosan (CS) and hydroxyapatite (Hap) also containing acetic acid (pH = 4.5). For better characterization of the nature of the inorganic matter entrapped within the resulting composite, we performed either oxygen plasma or calcination processes to remove the organic matter. The nature of the phosphate salts was studied by XRD and NMR studies. Amorphous calcium phosphate (ACP) was identified as the mineral phase in the composites submitted to oxygen plasma, whereas crystalline Hap was obtained after calcination. SEM microscopy revealed the formation of porous structures (porosity around 80–85%) in the original composites, as well as in the inorganic matrices obtained after calcination, with porous channels of up to 50 µm in diameter in the former case and of up to 20 µm in the latter. The biocompatibility of the composites was assessed using two different cell lines: C2C12GFP premyoblastic cells and MC3T3 preosteoblastic cells.

Sol-gel and SPS combined synthesis of highly porous wollastonite ceramic materials with immobilized Au-NPs

Abstract Here we present a prospective method of sol-gel synthesis of highly porous wollastonite ceramic powders with controlled macroporous structure (mean pore size ~160 nm) and immobilized gold nanoparticles (particle size is less than 50 nm). The method's distinction is based on using the colloidal template (micelles of core-shell polymer latex) both as a poreforming agent and as nanoreactors for nanoparticle synthesis in the system wollastonite/Au-NPs. We revealed the impact of template thermal removal on the morphology of nanostructured wollastonite. We also optimized thermal treatment to obtain defect-free macroporous calcium silicates. Template functionalization by size stabilized gold nanoparticles with their following immobilization into the porous volume of synthesized wollastonite has been described. Besides, an original nonstandard method of combined sol-gel (template) synthesis and spark plasma sintering (SPS) is suggested to obtain the wollastonite ceramic compounds with bimodal pore size distribution (100–500 nm and not less than 1 µm), high mechanical strength (compressive strength limit ~120 MPa) and containing immobilized Au-NPs. Peculiarities of biporous silicate framework formation has been studied using two types of poreforming agents (templates) of various origin, shape and size, introduced during different stages of sol-gel and SPS processes. These templates are organoelemental polymer latex of “core-shell” type and nonorganic carbon filler. Developed approaches are innovative and provide to make new materials with unique characteristics and functional properties as bone-like structure, mechanical stability, antibacterial and anti-inflammatory effects and etc. The materials meet all the biomaterials requirements and are in high demand by modern medicine.

Sorption of phosphates on macroporous synthetic calcium silicates

The sorption of phosphate ions on macroporous synthetic calcium silicates has been studied and it has been evaluated whether the latter are suitable to serve as sorbents of geochemical barriers preventing phosphorus losses from agricultural soils.

Bioinspired fabrication of macroporous calcium carbonate crystals mediated by thermoresponsive copolymers

Scheme showing the growth mechanism of the CaCO3 crystals at 50 °C.