Porous Biphasic Calcium Phosphate Ceramics Research Articles

Triply periodic minimal surfaces structured biphasic calcium phosphate bio-scaffolds with controllable porous struts from digital light processing of Pickering emulsion

Hierarchically porous biphasic calcium phosphate (BCP) ceramics with triply periodic minimal surface structure and porous framework have been fabricated by digital light processing (DLP) using dual-phase Pickering emulsion as the paste. The pristine hydroxyapatite and β-tricalcium phosphate particles were separately modified by dispersant firstly to obtain photosensitive Pickering emulsion with suitable rheological properties and stability for DLP printing. The porous structure has been well regulated by dispersant content, and ethylene glycol content. The resulting BCP ceramics exhibited a hierarchical pore structure consisting of interconnected micropores ranging from 1.13 μm to 8.98 μm and model-designed pores of nearly 500 μm, demonstrating excellent compressive strength of 4.83 MPa at a porosity of 60 %. In vitro biological experiments revealed that rat bone marrow mesenchymal stem cells exhibited good proliferation and adhesion ability on the BCP bio-scaffolds, thereby enhancing their application potential in bone regenerative medicine.

Effects of void defects on the mechanical properties of biphasic calcium phosphate nanoparticles: A molecular dynamics investigation

Porous biphasic calcium phosphate (BCP) ceramics are widely used in bone tissue engineering, and the mechanical properties of BCP implants must be reliable. However, the effects of pore structure (e.g., shape and size) on the mechanical properties are not well understood. In this study, we used molecular dynamics simulations to investigate the influence of pore shape and size on the mechanical behavior of BCP nanoparticles. BCP void models with cylindrical and cuboid pores ranging from 2 to 16 nm in diameter were constructed, and the elastic moduli were calculated. In addition, uniaxial tensile and compressive tests were performed on the models. We found that the pore size had a more significant impact on the mechanical properties of BCP than pore shape. Further, the elastic moduli decreased nonlinearly with increasing pore size. In addition, the tensile and compressive strength also decreased with the increase in pore size, but the ductility improved. Furthermore, deformation and fracture were more likely to occur near the pores and at the phase interfaces as a result of high atomic local strain in the calcium-deficient hydroxyapatite area. The results of this work reveal the effects of pore parameters on the mechanical properties of porous BCP at the nanometer level, which may aid the design of improved porous and multiphase CaP-based biomaterials for bone regeneration.

Fabrication and preliminary evaluation of the osteogenic potential for micro-/nano-structured porous BCP ceramics

Nanoscale interface of biomaterials exhibits superiorities in promoting tissue repair and healing. Bioceramics are one of the most commonly used biomaterials for biological purposes such as tissue engineering. The fabrication of nanoscale ceramics with smart topography is essential for modulating cells in contact with such surface. In this research, a gas foaming method was employed to fabricate porous biphasic calcium phosphate (BCP) ceramics as substrates with a controllable component of hydroxyapatite/beta tricalcium phosphate (HA/β-TCP). Hydrothermal reaction was then introduced to modify the surface morphology of the substrates to obtain a nanoscale topography at different pH values and ionic microenvironments. Three kinds of ceramics (BCP; BCP with a nanoneedle-like surface, BNN; BCP covered with a hollow nanorod-like surface, BHN) were prepared with different surface morphologies and roughness, degradation properties and the phase composition during the hydrothermal process. All of them possessed an interconnected pore structure of macropores and micropores. Importantly, the nano-scale surface structure increased the total pore volumes as well as the micropore volumes, thus enhanced the specific surface area (SSA) and subsequent biological performance. Their biological behavior has also been assessed through a series of pivotal events, i.e. protein adsorption, cell attachment, proliferation, and osteogenic differentiation. Consequently, we found the nano-crystallization of the hollow nanorod-like structured and nanoneedle-like structured ceramic surface enhance the adsorption of both total serum proteins and BSA in vitro compared to the original BCP ceramics with micro-sized grains, as well as exhibit a more persistent release of BSA. Additionally, all the three ceramics have displayed excellent biocompatibilities for MSCs, and the morphology of ceramics played a decisive role in cells spreading and morphology, in which BNN showed the strongest effect to facilitate MSCs differentiation towards osteogenesis.

In vitro and in vivo assessment of nanostructured porous biphasic calcium phosphate ceramics for promoting osteogenesis in an osteoporotic environment.

Treatment of bone defects in osteoporotic patients with bone substitutes is difficult, due to insufficient osseointegration. The development of appropriate biomaterials to solve the problem requires the assessment of the material performance in an osteoporotic environment, which is rarely investigated. Herein, nanostructured biphasic calcium phosphate (nBCP) ceramics were prepared via the incorporation of hydroxyapatite nanoparticles (HANPs) into porous biphasic CaP (BCP) substrates, leading to an increase of over 500% in the specific surface area. Primary osteoblasts harvested from osteoporotic rats were cultured on the nBCP ceramics, and it was found that the osteoblast functions, including proliferation, alkaline phosphatase activity, osteocalcin secretion and expression of osteogenic genes, were significantly enhanced compared with osteoblasts grown on non-nanostructured BCP ceramics. To further assess the osteoinduction ability, the ceramics were implanted in the femur of osteoporotic rats. Compared to the rats implanted with non-nanostructured BCP ceramics, a higher amount of mechanically matured bone was newly formed in the rats with nBCP ceramics after 6 weeks of implantation. Such enhanced osteoinduction ability of the nBCP ceramics may be due to the incorporated HANPs, as well as the nanostructured topography induced by the HANPs. These results indicate good in vitro and in vivo osteoinductivity of the nBCP ceramics in an osteoporotic environment and offer potential benefits for treating bone defects in osteoporotic patients.

Preparation and biological effects of apatite nanosheet-constructed porous ceramics.

The design and processing of bioceramics into specific architectures (especially with micro-/nanoscale specific architectures) to improve their biological performances or extend their applications are always the cutting-edge research of bioceramics. Herein, we designed a kind of apatite nanosheet-constructed porous ceramics (AN-PCs), which were fabricated by foam moulding, high heat sintering, and then water soaking the α-tricalcium phosphate (hydroxyapatite - contained porous biphasic calcium phosphate ceramics). Experiments demonstrated that such stereo-nanotopographies had excellent cytocompatibility, and could regulate mesenchymal stem cells (MSCs) to differentiate into osteogenic lineages. And an in vivo ectopic-implant showed that the AN-PCs possessed osteoinductivity. Thus, the AN-PCs reported herein show improved biological performances to repair hard tissues.

Tailoring the pore structure and property of porous biphasic calcium phosphate ceramics by NaCl additive

This study investigated the effects of NaCl additive on the phase composition, pore structure and mechanical property of porous biphasic calcium phosphate (BCP) ceramics, which were prepared by freeze-casting. The results indicated that the addition of NaCl promoted transformation of β-tricalcium phosphate to hydroxyapatite in the BCP ceramics; the OH group in HA phase of BCP ceramic was partially replaced by chloride ion. As the mass fraction of NaCl in the slurry increased from 0 to 3%, the porosity of obtained porous BCP ceramics decreased from 77.76% to 60.22%; the average width of dendritic pores increased from 74.37µm to 111.27µm; the compressive strength achieved threefold increase. As the amount of NaCl additive reached 4.5%, the porosity, pore width, and compressive strength of the porous BCP ceramics were comparable with those modified by 3% NaCl. NaCl is regarded as an effective additive to tailor the pore structure and property of freeze-cast porous ceramics.

Comparative study on in vivo response of porous calcium carbonate composite ceramic and biphasic calcium phosphate ceramic

In a previous study, robust calcium carbonate composite ceramics (CC/PG) were prepared by using phosphate-based glass (PG) as an additive, which showed good cell response. In the present study the in vivo response of porous CC/PG was compared to that of porous biphasic calcium phosphate ceramics (BCP), using a rabbit femoral critical-size grafting model. The materials degradation and bone formation processes were evaluated by general observation, X-ray radiography, micro-computed tomography, and histological examination. The results demonstrated excellent biocompatibility and osteoconductivity, and progressive degradation of CC/PG and BCP. Although the in vitro degradation rate of CC/PG was distinctly faster than that of BCP, at 4week post-implantation, the bone generation and material degradation of CC/PG were less than those of BCP. Nevertheless, at postoperative week 8, the increment of bone formation and material degradation of CC/PG was pronouncedly larger than that of BCP. These results show that CC/PG is a potential resorbable bone graft aside from the traditional synthetic ones.

Porous biphasic calcium phosphate ceramics coated with nano-hydroxyapatite and seeded with mesenchymal stem cells for reconstruction of radius segmental defects in rabbits.

The osteoconduction of porous biphasic calcium phosphate (BCP) ceramics has been widely reported. In a previous study, we demonstrated that applying a nano-hydroxyapatite (nHA) coating enhances the osteoinductive potential of BCP ceramics, making these scaffolds more suitable for bone tissue engineering applications. The aim of the present study was to determine the effects of reconstructing radius defects in rabbits using nHA-coated BCP ceramics seeded with mesenchymal stem cells (MSCs) and to compare the bone regeneration induced by different scaffolds. Radius defects were created in 20 New Zealand rabbits, which were divided into four groups by treatment: porous BCP ceramics (Group A), nHA-coated porous BCP ceramics (Group B), porous BCP ceramics seeded with rabbit MSCs (Group C), and nHA-coated porous BCP ceramics seeded with rabbit MSCs (Group D). After in vitro incubation, the cell/scaffold complexes were implanted into the defects. Twelve weeks after implantation, the specimens were examined macroscopically and histologically. Both the nHA coating and seeding with MSCs enhanced the formation of new bone tissue in the BCP ceramics, though the osteoinductive potential of the scaffolds with MSCs was greater than that of the nHA-coated scaffolds. Notably, the combination of nHA coating and MSCs significantly improved the bone regeneration capability of the BCP ceramics. Thus, MSCs seeded into porous BCP ceramics coated with nHA may be an effective bone substitute to reconstruct bone defects in the clinic.

Effect of nano-hydroxyapatite coating on the osteoinductivity of porous biphasic calcium phosphate ceramics

BackgroundPorous biphasic calcium phosphate (BCP) ceramics exhibit good biocompatibility and bone conduction but are not inherently osteoinductive. To overcome this disadvantage, we coated conventional porous BCP ceramics with nano-hydroxyapatite (nHA). nHA was chosen as a coating material due to its high osteoinductive potential.MethodsWe used a hydrothermal deposition method to coat conventional porous BCP ceramics with nHA and assessed the effects of the coating on the physical and mechanical properties of the underlying BCP. Next, its effects on mesenchymal stem cell (MSC) attachment, proliferation, viability, and osteogenic differentiation were investigated.ResultsnHA formed a deposited layer on the BCP surface, and synthesized nHA had a rod-like shape with lengths ranging from ~50–200 nm and diameters from ~15–30 mm. The nHA coating did not significantly affect the density, porosity, flexural strength, or compressive strength of the underlying BCP (P > 0.1). Scanning electron microscopy showed MSC attachment to the scaffolds, with a healthy morphology and anchorage to nHA crystals via cytoplasmic processes. The densities of MSCs attached on BCP and nHA-coated BCP scaffolds were 62 ± 26 cells/mm2 and 63 ± 27 cells/mm2 (P > 0.1), respectively, after 1 day and 415 ± 62 cells/mm2 and 541 ± 35 cells/mm2 (P < 0.05) respectively, after 14 days. According to an MTT assay, MSC viability was higher on nHA-coated BCP scaffolds than on BCP scaffolds (P < 0.05). In addition, MSCs on nHA-coated BCP scaffolds produced more alkaline phosphatase, collagen type I, and osteocalcin than MSCs on BCP scaffolds (P < 0.05).ConclusionsOur results demonstrate that BCP scaffolds coated with nHA were more conducive for MSC adhesion, proliferation, and osteogenic differentiation than conventional, uncoated BCP scaffolds, indicating that nHA coating can enhance the osteoinductive potential of BCP ceramics, making this material more suitable for applications in bone tissue engineering.

Enhanced repair of a critical-sized segmental bone defect in rabbit femur by surface microstructured porous titanium

Repair of load-bearing bone defects remains a challenge in the field of orthopaedic surgery. In the current study, a surface microstructured porous titanium (STPT) successively treated with H2O2/TaCl5 solution and simulated body fluid was used to repair the critical-sized segmental bone defects in rabbit femur, and non-treated porous titanium (NTPT) and porous biphasic calcium phosphate ceramics (PBCP) were used as control, respectively. A 15mm long implant was positioned in the femoral defect and stabilized by a plate and screws fixation. After implantation into the body for 1, 3 and 6months, X-ray observation confirmed that porous titanium groups (NTPT and STPT) provided better mechanical support than PBCP group at the early stage. However, there was no obvious difference in the formed bony callus between PBCP and STPT groups in the later stage, and they both showed better shape of bony callus than NTPT group. Micro-CT and histomorphometric analysis for the samples of 6-month implantation demonstrated that more new bone formed in the inner pores of PBCP and STPT groups than that in NTPT group. Moreover, the biomechanical tests revealed that STPT group could bear larger compressive load than NTPT and PBCP groups, almost reaching the level of the normal rabbit femur. STPT exhibited the enhanced repairing effect on the critical-sized segmental bone defect in rabbit femur, meaning that it could be an ideal material for the repair of large bone defect in load-bearing site.

Use of Glycerol as a Cryoprotectant in Vacuum‐Assisted Foaming of Ceramic Suspension Technique for Improving Compressive Strength of Porous Biphasic Calcium Phosphate Ceramics

This article reports the utility of glycerol as a cryoprotectant for improving the compressive strength of highly porous biphasic calcium phosphate (BCP) ceramics, comprised of hydroxyapatite and β‐tricalcium phosphate, produced using vacuum‐assisted foaming of a ceramic suspension technique. All the samples produced with various glycerol contents (0, 9, 17, and 23 wt% in relation to the water content) showed a highly porous structure with a uniform pore distribution. However, the addition of glycerol effectively suppressed the formation of microchannels in the BCP walls, accordingly leading to a considerable increase in compressive strength from 0.72 ± 0.11 to 2.36 ± 0.41 MPa with increasing glycerol content from 0 to 23 wt%.

Effect of nanostructure on osteoinduction of porous biphasic calcium phosphate ceramics

In order to evaluate the effect of the nanostructure of calcium phosphate ceramics on osteoinductive potential, porous biphasic calcium phosphate (BCP) ceramics with a nano- or submicron structure were prepared via microwave sintering and compared to conventional BCP ceramics. The selective protein adsorption of bovine serum albumin and lysozyme (LSZ) and the osteogenic differentiation of human mesenchymal stem cells in vitro was investigated. Porous BCP nanoceramics showed higher ability to adsorb proteins, especially low molecular weight protein of LSZ, than conventional BCP ceramics, and the BCP nanoceramics promoted bone sialoprotein expression more than conventional BCP did. Further in vivo study to investigate ectopic bone formation and bone repair efficiency proved the highly osteoinductive potential of nanostructured BCP ceramics. The results suggest that nanostructured BCP ceramics have the potential to become a new generation of bioceramics for bone tissue engineering grafts.

Highly Porous Biphasic Calcium Phosphate (BCP) Ceramics with Large Interconnected Pores by Freezing Vigorously Foamed BCP Suspensions under Reduced Pressure

This article proposes a new way of producing highly porous biphasic calcium phosphate (BCP) ceramics with large interconnected pores by freezing a vigorously foamed BCP suspension under reduced pressure, which allows the air bubbles incorporated into the BCP suspension to expand extensively. All the fabricated samples produced with various degrees of expansion of the BCP suspension (0, 150, 200, and 250 vol%) showed a highly uniform porous structure with their unique microporous BCP walls. The sizes of the pores and interconnections between the pores increased remarkably from 74 ± 21 μm to 295 ± 93 μm and 22 ± 8 μm to 123 ± 60 μm, respectively, with increasing degree of expansion from 0 to 250 vol%. However, the compressive strength decreased from 1.2 ± 0.29 MPa to 0.4 ± 0.07 MPa with increasing degree of expansion from 150 to 250 vol%.

Osteoinduction by Ca-P biomaterials implanted into the muscles of mice

The osteoinduction of porous biphasic calcium phosphate ceramics (BCP) has been widely reported and documented, but little research has been performed on rodent animals, e.g., mice. In this study, we report osteoinduction in a mouse model. Thirty mice were divided into two groups. BCP materials (Sample A) and control ceramics (Sample B) were implanted into the leg muscle, respectively. Five mice in each group were killed at 15, 30, and 45 d after surgery. Sample A and Sample B were harvested and used for hematoxylin and eosin (HE) staining, immunohistochemistry (IHC) staining, and Alizarin Red S staining to check bone formation in the biomaterials. Histological analysis showed that no bone tissue was formed 15 d after implantation (0/5) in either of the two groups. Newly-formed bone tissues were observed in Sample A at 30 d (5/5) and 45 d (5/5) after implantation; the average amounts of newly-formed bone tissues were approximately 5.2% and 8.6%, respectively. However, we did not see any bone tissue in Sample B until 45 d after implantation. Bone-related molecular makers such as bone morphogenesis protein-2 (BMP-2), collagen type I, and osteopontin were detected by IHC staining in Sample A 30 d after implantation. In addition, the newly-formed bone was also confirmed by Alizarin Red S staining. Because this is the report of osteoinduction in the rodent animal on which all the biotechnologies were available, our results may contribute to further mechanism research.

A new technological procedure using sucrose as porogen compound to manufacture porous biphasic calcium phosphate ceramics of appropriate micro- and macrostructure

In the domain of implantable materials, the porosity and pore size distribution of a material in contact with bone is decisive for bone ingrowth and thus the control of the porosity is of great interest. The use of a new porogen agent, i.e. sucrose is proposed to create a porosity in biphasic calcium phosphate blocks. The technological procedure is as follows: sucrose and mineral powder are mixed, then compressed by isostatic compression and sintering finally eliminates sucrose. Blocks obtained were compared to a manufactured product: Triosite® (Zimmer, Etupes, France) which porosity is created through a naphthalene sublimation process.Results have shown that the incorporation of sucrose allows the preparation of porous blocks with controlled porosity varying from 40 to 80% and with macro-, meso- and microporosity characteristics depending on the percentage of sucrose added as well as on the granulometry of both sucrose and mineral powder.

Fabrication and cellular biocompatibility of porous carbonated biphasic calcium phosphate ceramics with a nanostructure

Microwave heating was applied to fabricate interconnective porous structured bodies by foaming as-synthesized calcium-deficient hydroxyapatite (Ca-deficient HA) precipitate containing H 2O 2. The porous bodies were sintered by a microwave process with activated carbon as the embedding material to prepare nano- and submicron-structured ceramics. By comparison, conventional sintering was used to produce microstructured ceramics. The precursor particles and bulk ceramics were characterized by transmission electron microscopy (TEM), dynamic light scattering, scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FTIR) and mechanical testing. TEM micrographs and assessment of the size distribution showed that the needle-like precursor particles are on the nanoscale. SEM observation indicated that the ceramics formed by microwave sintering presented a structure of interconnective pores, with average grain sizes of ∼86 and ∼167 nm. XRD patterns and FTIR spectra confirmed the presence of carbonated biphasic calcium phosphate (BCP), and the mechanical tests showed that the ceramics formed by microwave sintering had a compressive strength comparable to that obtained by conventional methods. Rat osteoblasts were cultured on the three kinds of BCP ceramics to evaluate their biocompatibility. Compared with the microscale group formed by conventional sintering, MTT assay and ALP assay showed that nanophase scaffolds promoted cell proliferation and differentiation respectively, and SEM observation showed that the nanoscale group clearly promoted cell adhesion. The results from this study suggest that porous carbonated biphasic calcium phosphate ceramics with a nanostructure promote osteoblast adhesion, proliferation and differentiation. In conclusion, porous carbonated BCP ceramics with a nanostructure are simple and quick to prepare using microwaves and compared with those produced by conventional sintering, may be better bone graft materials.

Comparative in vivo study of six hydroxyapatite‐based bone graft substitutes

Improvement of synthetic bone graft substitutes as suitable alternatives to a patient's own bone graft remains a challenge in biomaterials research. Our goal was to answer the question of whether improved osteoinductivity of a material would also translate to better bone-healing orthotopically. Three porous biphasic calcium phosphate (BCP) ceramics (BCPA, BCPB, and BCPC), consisting of hydroxyapatite and beta-tricalcium phosphate, a porous biphasic calcium phosphate ceramic reinforced with a bioresorbable polylactic acid to improve its mechanical properties (BCPC+), a pure hydroxyapatite ceramic (HA), and a carbonated apatite ceramic (CA) were implanted intramuscularly and orthotopically by using a transverse process model in 11 goats for 12 weeks. BCPA and BCPB had similar chemical composition but differed in their microstructure. BCPB was not osteoinductive at all, but BCPA induced ectopic bone formation in 9 of 11 animals. Orthotopically, BCPA performed better than BCPB in both the amount and rate of bone formation. BCPC, similar to BCPA structurally and physicochemically, showed comparable results ectopically and orthotopically. Addition of resorbable polymer to BCPC made the material less osteoinductive (4 of 11 animals) and delayed bone formation orthotopically. Neither HA nor CA were osteoinductive, and their orthotopic performance was inferior to the osteoinductive ceramics. The results of the present study showed that material-derived osteoinduction significantly enhanced bone healing orthotopically, and that this material property appeared more sensitive for predicting orthotopic performance than physicochemical and structural characteristics.

Preparation and characterization of biphasic calcium phosphate ceramics of desired composition

A modified processing route for fabricating dense and porous biphasic calcium phosphate (BCP) ceramics of desired and reproducible phase composition (hydroxyapatite (HA)/beta-tricalcium phosphate (beta-TCP) ratio) has been developed. The principal idea of the route was combining a precipitation and a solid phase methods. First, a nonstoichiometric (slightly carbonated calcium-deficient) HA (CdHA) precipitate was synthesized by mixing a calcium carbonate (CaCO(3)) water suspension with an orthophosphoric acid (H(3)PO(4)) solution in abundance (related to the amount resulting in a stoichiometric HA) under definite conditions, and a powder of the precipitate was prepared and calcinated in air (860 degrees C, 1.5 h). In the second stage, a BCP ceramics of the composition determined by the calcium-deficiency in a calcinated powder (the acid abundance in a mixture) was processed by sintering powder compacts with or without a porosizer under appropriate conditions (1,200 degrees C, 2h). A calibrating dependence of the HA/beta-TCP ratio in the ceramics on the acid abundance has been plotted which enabled a controlled preparation of BCP ceramics. A correlation based on unresolved bands in nu(4)-PO (4) (3-) domain in IR-spectra of nanostructured BCP materials was found. Using the correlation, the process of CdHA --> beta-TCP transformation could be easily monitored. The density and microhardness of the BCP ceramics neglectly depended on the composition, however, the compressive strength did: the lower the HA/beta-TCP ratio, the higher the strength in the dense materials.

Bimodal Porous Bi-Phasic Calcium Phosphate Ceramics and Its Dissolution in SBF Solution

Biphasic calcium phosphate (BCP) ceramics, a mixture of hydroxyapatite (HAp) and beta-tricalcium phosphate (β-TCP), of varying HAp/β-TCP ratios were prepared from fine powders. Porous BCP ceramic materials with HAp/β-TCP weight rations of 20/80, 40/60, and 80/20 were prepared. In this study, the bioactivity is reduced at a larger HAp content rate, which is likely related to the high driving pore for the formation of a new phase, and the reaction rate was proportional to the β-TCP. The porous BCP ceramics having a bigger porosity rate can easily under up dissolution. The powder having a larger β-TCP content rate can easily generate a new phase. The dissolution results confirmed that the biodegradation of calcium phosphate ceramics could be controlled by simply adjusting the amount of HAp or β-TCP in the ceramics and porosity rate.

Fabrication of Porous Structure of BCP Sintered Bodies Using Microwave Assisted Synthesized HAp Nano Powder

Using microwave synthesized HAp nano powder and polymethyl methacrylate (PMMA) as a pore-forming agent, the porous biphasic calcium phosphate (BCP) ceramics were fabricated depending on the sintering temperature. The synthesized HAp powders was about 70-90 nm in diameter. In the porous sintered bodies, the pores having 150-180 μm were homogeneously dispersed in the BCP matrix. Some amounts of pores interconnected due the necking of PMMA powders which will increase the osteoconductivity and ingrowth of bone-tissues while using as a bone substrate. As the sintering temperature increased, the relative density increased and showed the maximum value of 79.6%. From the SBF experiment, the maximum resorption of Ca2+ ion was observed in the sample sintered at 1000°C.