BCP Ceramics Research Articles

3D printing calcium phosphate ceramics with high osteoinductivity through pore architecture optimization

The osteoinductivity of 3D printed calcium phosphate (CaP) ceramics has a large gap compared with those prepared by conventional foaming methods, and improving the osteoinductivity of 3D printing CaP ceramics is crucial for successful application in bone regeneration. Pore architecture plays a critical role in osteoinductivity. In this study, CaP ceramics with a hexagonal close-packed (HCP) spherical pore structure were successfully fabricated using DLP printing technology. Additionally, octahedral (Octahedral), diamond (Diamond), and helical (Gyroid) structures were constructed with similar porosity and macropore diameter. CaP ceramics with the HCP structure exhibited higher compression strength (8.39 ± 1.82 MPa) and lower permeability (6.41 × 10−11 m2) compared to the Octahedral, Diamond, and Gyroid structures. In vitro cellular responses indicated that the macropore architecture strongly influenced the local growth rate of osteoblast-formed cell tissue; cells grew uniformly and formed circular rings in the HCP group. Furthermore, the HCP group promoted the expression of osteogenic genes and proteins more effectively than the other three groups. The outstanding osteoinductivity of the HCP group was confirmed in canine intramuscular implantation studies, where the new bone area reached up to 8.02 ± 1.94 % after a 10-week implantation. Additionally, the HCP group showed effective bone regeneration in repairing femoral condyle defects. Therefore, our findings suggest that 3D printed CaP bioceramics with an HCP structure promote osteoinductivity and can be considered as candidates for personalized precise treatment of bone defects in clinical applications. Statement of significance1. 3D printing BCP ceramics with high osteoinductivity were constructed through pore architecture optimization.2. BCP ceramics with HCP structure exhibited relatively higher mechanical strength and lower permeability than those with Octahedral, Diamond and Gyroid structures.3. BCP ceramics with HCP structure could promote the osteogenic differentiation of MC3T3-E1, and showed the superior in-vivo osteoinductivity and bone regeneration comparing with the other structures.

Indirect 3D printing CDHA scaffolds with hierarchical porous structure to promote osteoinductivity and bone regeneration

Hierarchical porous structure, which include macropores, minor pores, and micropores in scaffolds, are essential in the multiple biological functions of bone repair and regeneration. In this study, patient-customized calcium-deficient hydroxyapatite (CDHA) scaffolds with three-level hierarchical porous structure were fabricated by indirect 3D printing technology and particulate leaching method. The sacrificial template scaffolds were fabricated using a photo-curing 3D printer, which provided a prerequisite for the integral structure and interconnected macropores of CDHA scaffolds. Additionally, 20 wt% pore former was incorporated into the slurry to enhance the content of smaller pores within the CDHA-2 scaffolds, and then the CDHA-2 scaffolds were sintered to remove the sacrificial template scaffolds and pore former. The obtained CDHA-2 scaffolds exhibited interconnected macropores (300–400 μm), minor pores (∼10–100 μm), and micropores (< 10 μm) distributed throughout the scaffolds, which could promote bone tissue ingrowth, increase surface roughness, and enhance protein adsorption of scaffolds. In vitro studies identified that CDHA-2 scaffolds had nanocrystal grains, high specific surface area, and outstanding protein adsorption capacity, which could provide a microenvironment for cell adhesion, spreading, and proliferation. In addition, the murine intramuscular implantation experiment suggested that CDHA-2 scaffolds exhibited excellent osteoinductivity and were superior to traditional BCP ceramics under conditions without the addition of live cells and exogenous growth factors. The rabbit calvarial defect repair results indicated that CDHA-2 scaffolds could enhance in situ bone regeneration. In conclusion, these findings demonstrated that the hierarchical porous structure of CDHA scaffolds was a pivotal factor in modulating osteoinductivity and bone regeneration, and CDHA-2 scaffolds were potential candidates for bone regeneration.

Phase and structural transformations during sintering of uncalcinated hydrolyzed and carbonated amorphous calcium phosphates

An uncalcinated carbonated amorphous calcium phosphate (CACP) compact during heating lost its absorbed and structural waters as well as volatile gases from residual by-products up to 600 °C and crystallized into a partially carbonated nanocrystalline calcium-deficient hydroxyapatite (CDHA) within 600–750 °C. The CDHA transformed into a mixture of stoichiometric HA and β-TCP (BCP) at 900 °C. These transformations in case of the preliminary uncalcinated CACP resulted in an increased density of the compact from 1.0 g cm−3 to 2.97 g cm−3, i.e., by a factor of about three. Such a high “green” density gave a ceramics of 95 % density (37/63 β-TCP/HA) for the BCP compact heated to 1000 °C practically with no holding time. This finding seems to be promising for the preparation of BCP ceramics with improved quality.

Regulating the multifactor during wet chemical synthesis to obtain calcium phosphate powders with controllable phase purity for bone repair

Calcium phosphate ceramics are widely used as bone repair materials owing to their excellent biocompatibility, bone conductivity, bone induction, and degradability. Although there are many methods for synthesizing calcium phosphate and controlling its phase composition, it is necessary to explore effective preparation methods by understanding the formation of calcium phosphate and its influencing factors. In this study, calcium phosphate powders with controllable phase compositions were synthesized using a wet chemical precipitation method by adjusting the process parameters (aging time, bipolar solution, initial Ca-P molar ratio, capping agent concentration, and system concentration). Subsequently, a certain biphasic proportion of (biphasic calcium phosphate, BCP) products was prepared, and pure (β-tricalcium phosphate, β-TCP) can be obtained according to the customer's requirements. BCP ceramics with desired phase compositions were obtained by pressing and sintering different calcium-deficient powders. Specifically, β-TCP powder with a purity of 99.83 wt% was obtained when the aging time, bipolar solution, initial Ca-P molar ratio, capping agent concentration, and system concentration were 0 h, 50% ethanol, 1, 0.27 M, and 0.0135 M, respectively. The BCP synthesized in this study shows great application potential in the field of bone tissue repair materials.

Dopamine/DOPAC-assisted immobilization of bone morphogenetic protein-2 loaded Heparin/PEI nanogels onto three-dimentional printed calcium phosphate ceramics for enhanced osteoinductivity and osteogenicity.

Nowadays, the three-dimensional (3D) printed calcium phosphate (CaP) ceramics have well-designed geometric structure, but suffer from relative weak osteoinductivity. Surface modification by incorporating bone morphogenetic protein-2 (BMP2) onto scaffolds is considered as an efficient approach to improve their bioactivity. However, high dose and uncontrolled burst release of BMP2 may cause undesired side effect. In the present study, porous BCP ceramics with inverse face-centred cube structure prepared by digital light processing (DLP)-based 3D printing technique were used as the substrates. BMP2 proteins were loaded in the self-assembled Heparin/PEI nanogels (NP/BMP2), and then immobilized onto BCP substrates through the intermediate mussel-derived bioactive dopamine and dihydroxyphenylacetic acid (DA/DOPAC) coating layers to construct functional BCP/layer/NP/BMP2 scaffolds. Our results showed that Heparin/PEI nanogel was a potent delivery system for BMP2, and BCP/layer/NP/BMP2 scaffolds exhibited the high loading capacity, controlled release rate, and sustained local delivery of BMP2. In vitro cell experiments with bone marrow stromal cells (BMSCs) found that BCP/layer/NP/BMP2 could promote cell proliferation, facilitate cell spreading, accelerate cell migration, up-regulate expression of osteogenic genes, and improve synthesis of osteoblast-related proteins. Moreover, the murine intramuscular implantation model suggested that BCP/layer/NP/BMP2 had a superior osteoinductive capacity, and the rat femoral condyle defect repair model showed that BCP/layer/NP/BMP2 could enhance in situ bone repair and regeneration. These findings demonstrate that the incorporation of BMP2 loaded Heparin/PEI nanogels to 3D printed scaffolds holds great promise in fabricating bone graft with a superior biological performance for orthopedic application.

Enhanced ectopic bone formation by strontium-substituted calcium phosphate ceramics through regulation of osteoclastogenesis and osteoblastogenesis.

To explore how strontium influences osteoclastogenesis and osteoblastogenesis during material-induced ectopic bone formation, porous strontium-substituted biphasic calcium phosphate (Sr-BCP) and BCP ceramics with equivalent pore structures and comparable grain size and porosity were prepared. In vitro results showed that compared with BCP, Sr-BCP inhibited the osteoclastic differentiation of osteoclast precursors by delaying cell fusion, down-regulating the expression of osteoclast marker genes, and reducing the activity of osteoclast specific proteins, possibly due to the activated ERK signaling pathway but the suppressed p38, JNK and AKT signaling pathways. Meanwhile, Sr-BCP promoted the osteogenic differentiation of mesenchymal stem cells (MSCs) by up-regulating the osteogenic gene expression. Sr-BCP also mediated the expression of important osteoblast-osteoclast coupling factors, as evidenced by the increased Opg/Rankl ratio in mMSCs, and the reduced Rank expression and enhanced EphrinB2 expression in osteoclast precursors. Similar results were observed in an in vivo study based on a murine intramuscular implantation model. The sign of ectopic bone formation was only seen in Sr-BCP at 8 weeks. Compared to BCP, Sr-BCP obviously hindered the formation of TRAP- and CTSK-positive multinucleated osteoclast-like cells during the early implantation time up to 6 weeks, which is consistent with the in vivo PCR results. This suggested that Sr-BCP could clearly accelerate the ectopic bone formation by promoting osteogenesis but suppressing osteoclastogenesis, which might be closely related to the expression of osteoblast-osteoclast coupling factors regulated by Sr2+. These findings may help in the design and fabrication of smart bone substitutes with the desired potential for bone regeneration through modulating both osteoclastic resorption and osteoblastic synthesis.

Cell-mediated injectable blend hydrogel-BCP ceramic scaffold for in situ condylar osteochondral repair

The existing approaches for healing mandibular condylar osteochondral defects, which are prevalent in temporomandibular joint disorders (TMD), are sparse and not reparative. To address this, regenerative medicine in situ has transpired as a potential therapeutic solution as it can effectively regenerate composite tissues. Herein, injectable self-crosslinking thiolated hyaluronic acid (HA-SH)/type I collagen (Col I) blend hydrogel and BCP ceramics combined with rabbit bone mesenchymal stem cells (rBMSCs)/chondrocytes were used to fabricate a new bi-layer scaffold to simulate specific structure of rabbit condylar osteochondral defects. The in vitro results demonstrated that the blend hydrogel scaffold provided suitable microenvironment for simultaneously realizing proliferation and chondrogenic specific matrix secretion of both rBMSCs and chondrocytes, while BCP ceramics facilitated rBMSCs proliferation and osteogenic differentiation. The in vivo results confirmed that compared with cell-free implant, the rBMSCs/chondrocytes-loaded bi-layer scaffold could effectively promote the regeneration of both fibrocartilage and subchondral bone, suggesting that the bi-layer scaffold presented a promising option for cell-mediated mandibular condylar cartilage regeneration.

The role of micro-vibration parameters in inflammatory responses of macrophages cultured on biphasic calcium phosphate ceramics and the resultant influence on osteogenic differentiation of mesenchymal stem cells.

Although in vitro studies have shown that biomaterials and mechanical stimuli can mediate inflammatory responses or regulate osteogenesis of MSCs, the underlying behaviour of the inflammatory response of macrophages on biomaterials mediated by mechanical stimuli, which regulates osteogenesis, is relatively unknown. Thus, it is imperative to explore the role of bionic mechanical stimulation in the biomaterial-mediated inflammatory response of macrophages. In this study, we used osteoinductive biphasic calcium phosphate (BCP) ceramics as the model biomaterial and chose micro-vibration stimulation (MVs) with three variable parameters (frequency, magnitude, and time). Based on orthogonal experiments, nine combinations of MVs parameters were generated, and their effects on the BCP-mediated macrophage inflammatory response were investigated. MVs significantly affected the gene expression and cytokine secretion of macrophages grown on BCP ceramics and further influenced the behaviour of bone marrow mesenchymal stem cells (BMMSCs) in a paracrine manner. Moreover, frequency seemed to be the most dominant factor (compared with magnitude and time) in regulating the inflammatory response of macrophages. The optimal combination of MVs parameters (frequency 10 Hz, magnitude 0.45 g, and time 60 min) could induce a healing-associated M2 phenotype, as evidenced by the downregulated pro-inflammatory gene (Il-1β, and Tnf-α) expression, the upregulated anti-inflammatory gene (Il10) expression, and the inhibited pro-inflammatory cytokine (Il-1β and Tnf-α) secretion of macrophages grown on BCP ceramics, and its conditioned medium (CM) could further promote osteogenic differentiation of BMMSCs. These findings provide valuable insights into the mechanical stimulus-mediated macrophage inflammatory response and osteogenesis in the presence of osteoinductive BCP ceramics and allow accurate evaluation of the biological performance of biomaterials in vitro, in order to optimize bone substitute materials to achieve the desired clinical performance.

Evaluation of synthetic ceramics as compression resistant matrix to promote osteogenesis of autologous blood coagulum containing recombinant human bone morphogenetic protein 6 in rabbit posterolateral lumbar fusion model.

Posterolateral lumbar fusion (PLF) is a commonly performed surgical procedure for the treatment of pathological conditions of the lumbosacral spine. In the present study, we evaluated an autologous bone graft substitute (ABGS) containing rhBMP6 in autologous blood coagulum (ABC) and synthetic ceramics used as compression resistant matrix (CRM) in the rabbit PLF model. In the pilot PLF rabbit experiment, we tested four different CRMs (BCP 500-1700 μm, BCP 1700-2500 μm and two different TCP in the form of slabs) which were selected based on achieving uniform ABC distribution. Next, ABGS implants composed of 2.5 mL ABC with 0.5 g ceramic particles (TCP or BCP (TCP/HA 80/20) of particle size 500-1700 μm) and 125 μg rhBMP6 (added to blood or lyophilized on ceramics) were placed bilaterally between transverse processes of the lumbar vertebrae (L5-L6) following exposition and decortication in 12 New Zealand White Rabbits observed for 7 weeks following surgery. Spinal fusion outcome was analysed by μCT, palpatory segmental mobility testing and selected specimens were either tested biomechanically (three-point bending test) and/or processed histologically. The total fusion success rate was 90.9% by both μCT analyses and by palpatory segmental mobility testing. The volume of newly formed bone between experimental groups with TCP or BCP ceramics and the different method of rhBMP6 application was comparable. The newly formed bone and ceramic particles integrated with the transverse processes on histological sections resulting in superior biomechanical properties. The results were retrospectively found superior to allograft devitalized mineralized bone as a CRM as reported previously in rabbit PLF. Overall, this novel ABGS containing rhBMP6, ABC and the specific 500-1700 μm synthetic ceramic particles supported new bone formation for the first time and successfully promoted posterolateral lumbar fusion in rabbits.

Positive role of calcium phosphate ceramics regulated inflammation in the osteogenic differentiation of mesenchymal stem cells.

Recently, researches have confirmed the crucial role of inflammatory response in Ca-P ceramic-induced osteogenesis, however, the underlying mechanism has not yet been fully understood. In this study, BCP and β-TCP ceramics were used as material models to investigate the effect of physicochemical properties on inflammatory response in vitro. The results showed that BCP and β-TCP could support macrophages attachment, proliferation, and spreading favorably, as well as promote gene expressions of inflammatory related cytokines (IL-1, IL-6, MCP-1, and TNF-α) and growth factors (TGF-β, FGF, PDGF, VEGF, IGF, and EGF). BCP showed a facilitating function on the gene expressions earlier than β-TCP. Further coculture experiments performed in vitro demonstrated that the CMs containing various increased cytokines for macrophages pre-culture could significantly promote MSCs osteogenic differentiation, which was confirmed by the gene expressions of osteogenic specific markers and the intracellular OCN product accumulation under the stimulation of BCP and β-TCP ceramics. Further evidence was found from the formation of mineralized nodules in BCM and TCM. In addition, this study showed a concise relationship between Ca-P ceramic induced inflammation and its osteoinductivity that the increased cytokines and growth factors from macrophages could promote MSCs osteogenic differentiation.

The implication of the notch signaling pathway in biphasic calcium phosphate ceramic-induced ectopic bone formation: A preliminary experiment.

Calcium phosphate (BCP) ceramic is a promising material in bone regeneration because it was proved biocompatible, osteoconductive, osteoinductive, and effective. Although it manifests favorable characteristics in critical-sized bone defects repair, the mechanism of its osteoinduction is still unclear. In the present study, we studied the mechanism of ectopic bone formation, with interest in the Notch signaling pathway. BCP ceramics with or without Notch signaling inhibitor RO4929097 were cocultured with bone marrow-derived stem cells in vitro. The expression of osteogenesis (OPN/Col/Runx2) and Notch signaling pathway-related genes (Hes1/Jagged/Notch1) were increased in the BCP group compared with the control group without BCP but significantly decreased after adding RO4929097. Furthermore, a higher level of alkaline phosphatase activity was observed in the BCP group compared with RO4929097 and control group separately. For further confirmation, the intramuscularly ectopic implantation models of Beagle dogs were used. Quantitative real-time polymerase chain reaction showed a similar trend with the in vitro experiment. Histological and histomorphometric analysis indicated that bone formation was delayed by RO4929097. These findings illustrated that the Notch signaling pathway plays a pivotal role in bone formation induced by BCP; Notch signaling pathway may positively influence ectopic bone formation by promoting BMSCs to differentiate toward osteoblasts.

A Col I and BCP ceramic bi-layer scaffold implant promotes regeneration in osteochondral defects.

Osteochondral defects occur in the superficial cartilage region, intermediate calcified cartilage, and subchondral bone. Due to the limited regenerative capacity and complex zonal structure, it is critically difficult to develop strategies for osteochondral defect repair that could meet clinical requirements. In this study, type I collagen (Col I) and BCP ceramics were used to fabricate a new bi-layer scaffold for regeneration in osteochondral defects. The in vitro studies showed that the bi-layer scaffold provided special functions for cell migration, proliferation and secretion due to the layered scaffold structure. The in vivo results demonstrated that the bi-layered scaffold could effectively promote the regeneration of both the cartilage and the subchondral bone, and the newly formed cartilage layer, with a similar structure and thickness to the natural cartilaginous layer, could seamlessly integrate with the surrounding natural cartilage and regenerate an interface layer to mimic the native osteochondral structure.

Processing and Properties of Biphasic Calcium Phosphates Bioceramics Derived from Biowaste Materials

Properties of biphasic calcium phosphates bioceramics derived from biowaste materials were investigated. The hydroxyapatite (HA) powder was synthesized from bovine bone via thermal treatment while β-tricalcium phosphate (β-TCP) powder was synthesized from mussel shells via solid state solution. Pure HA and β-TCP were successful obtained. The HA and β-TCP were mixed together and sintered at 1100 - 1350°C. The effects of the sintering temperature and the ratio of HA/ β-TCP on the properties of the studied samples were investigated. The sintering temperature at 1250°C presented the maximum value of density and hardness. X-ray analysis of BCP ceramics sintered at 1250°C presented multiple phases of calcium phosphate. Average grain sizes of the studied samples decreased as the ratio of HA increased.

A serum protein adsorption profile on BCP ceramics and influence of the elevated adsorption of adhesive proteins on the behaviour of MSCs.

Protein adsorption plays a key role in bone repair and regeneration by affecting cell behavior. In this study, a biphasic calcium phosphate (BCP) ceramic, with excellent osteoinductivity, was chosen to investigate its serum protein adsorption profile using isobaric tags for relative and absolute quantification (iTRAQ) proteomics technology. 281 differentially adsorbed serum proteins and the involved biological processes were confirmed by the combination of Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. The differentially adsorbed adhesive proteins in the extracellular matrix (ECM)-receptor interaction pathway were further selected to investigate their roles in the behavior of mesenchymal stem cells (MSCs). Pre-coating and blockage experiments revealed that both adsorbed vitronectin (VN) and laminin (LN) could promote the attachment, proliferation and osteogenic differentiation of MSCs on the BCP ceramic by interacting with different integrin subunits. It is revealed that the up-regulated expressions of integrin α2, αv and β3, β5 could contribute to VN-mediated MSC functions, and the elevated gene expressions of α6 and β1, β4 could be related to the LN-participated process. The above results proved that the preferential protein adsorption on a biomaterial should be vital for modulating MSC functions in the course of material-mediated osteoinductivity.

Calcium phosphate altered the cytokine secretion of macrophages and influenced the homing of mesenchymal stem cells.

Immune cells such as macrophages play an important role in tissue regeneration. In this study, an in vivo mouse intramuscular implantation model was applied to demonstrate the gradual infiltration of macrophages, followed by homing of mesenchymal stem cells (MSCs) during the early phase of biphasic calcium phosphate (BCP)-induced ectopic bone formation. Then, a novel real-time cell analysis (RTCA) system was used to continuously monitor cell migration in vitro, suggesting the positive roles of BCP-mediated macrophage secretion in MSC recruitment. A Proteome Profiler cytokine array was also applied to investigate the BCP-stimulated secretion pattern of macrophages by simultaneously screening 111 cytokines, indicating that Raw 264.7 macrophages released a pronounced amount of chemokines (CCL2, 3, 4, 5 and CXCL2, 10, 16) and non-chemokine molecules (OPN, VEGF, CD14, Cystatin C and PAI-1), which are involved in cell homing and bone regeneration. Among them, osteoinductive BCP ceramics significantly promoted the secretion of CCL2, 3, 4 and Cystatin C in macrophages, which was consistent with the up-regulated expression of chemokine genes (Ccl2, 3, 4). Considering their previously-reported chemotactic functions, the effects of CCL2/MCP-1 and CCL3/MIP-1α on MSC recruitment were further evaluated by the RTCA system. It was found that exogenous CCL2/MCP-1 and CCL3/MIP-1α dramatically accelerated MSC migration, while their neutralizing antibodies reduced MSC motility. Moreover, BCP-mediated macrophage secretion up-regulated the gene expression of chemokine receptors (Ccr1 and Ccr2) in MSCs, but the blockage of CCR1 and CCR2 exerted inhibitory effects on MSC chemotaxis. RTCA results showed that compared to CCL3/CCR1, the CCL2/CCR2 axis might exert a predominant chemotactic effect for MSC recruitment. These findings indicated that osteoinductive BCP ceramics might regulate macrophage secretion via an ERK signaling pathway, and the increased release of chemokines in macrophages would accelerate MSC homing to facilitate bone formation. These findings might deepen our understanding of biomaterial-mediated immune response and help to design orthopedic implants with desired immunomodulatory abilities to recruit host stem cells endogenously for bone regeneration.

Effects of both Sr and Mg substitution on compositions of biphasic calcium phosphate derived from hydrothermal method

AbstractBiphasic calcium phosphate (BCP) ceramics have received much attention in the field of biomaterials. Regulation of phase compositions ofBCPis extremely important for improving their bioactivity. In this study, the effects of Sr‐ and Mg‐addition on the phase composition and morphology ofBCPceramics, prepared by a conventional hydrothermal way, were investigated deeply. The results indicated that the addition of Sr and Mg both facilitated the generation of β‐tricalcium phosphate (β‐TCP), and the relationships between the addition and the relative content of β‐TCPunder differentpH8.5 and 10.5 were similar. The relative content of β‐TCPphase increased linearly with the Sr addition. Meantime, the relative content of β‐TCPchanged quadratically with the Mg addition and reached its peak when the Mg addition was up to 30%. Besides, the fraction of β‐TCPphase of samples synthesized atpH8.5 was higher than that of samples synthesized atpH10.5 when the substitution was same. The morphology did not change significantly in Sr‐substituted samples while an enhancement in density was observed with Mg addition in Mg‐substituted samples. These results and findings provide more comprehensive knowledge about controlling the phase compositions ofBCPby changing the initial substitution of Mg and Sr.

Roles of calcium phosphate-mediated integrin expression and MAPK signaling pathways in the osteoblastic differentiation of mesenchymal stem cells.

Osteoinduction of calcium phosphate (CaP) ceramics has been widely confirmed and accepted, but the underlying mechanism has not been fully elucidated. This study investigates the early biomolecular events that contributed to the transduction of extracellular material cues outside in, when MSCs were cultured in osteoinductive biphasic calcium phosphate (BCP) ceramics, and explores their roles in BCP-induced osteogenesis. The results demonstrated that BCP ceramics had a strong adsorption affinity for serum proteins, which might favor cell adhesion and mediate the expression of the cell surface receptor - integrin. qRT-PCR analysis found that BCP ceramics significantly up-regulated integrin α2 and α3 genes under both in vitro and in vivo conditions. As integrins clustered together into focal contacts (cell adhesion sites), immunofluorescence staining showed that compared to glass surfaces, cells seeded in BCP ceramics formed a relatively short focal contact and exhibited a smaller cell size. Moreover, western blotting analysis indicated that BCP ceramics could activate down-stream MAPK signaling pathways, whereas blockage of either ERK or P38 signals could dramatically attenuate BCP-induced osteogenesis. These findings suggested that BCP ceramics might mediate cell adhesion through trans-membrane proteins - integrins - to realize the transduction of "outside-in signaling", and subsequently trigger the intracellular MAPK signaling cascade to induce the osteogenic differentiation of MSCs. They offered a promising principle for designing and fabricating tissue-inducing biomaterials to provide appropriate cues for target cells.

DNA-templated Fabrication of Biphasic Calcium Phosphate Ceramics with a Bimodal Pore Structure for Tissue Engineering

Abstract Biphasic calcium phosphate (BCP) ceramics with well-controlled pores were fabricated by sintering mixtures of synthetic hydroxyapatite (HAp) and deoxyribonucleic acid (DNA). BCP ceramics with macro- and micropores revealed excellent cell proliferation as a result of suitable surface topography and phase composition.

The pyrolytic synthesis of calcium phosphate compounds from carbonized fowl droppings

Abstract We succeeded in producing biomimetic calcium phosphate compounds, β-tricalcium phosphate (β-TCP: Ca 3 [PO 4 ] 2 ) or biphasic calcium phosphate of two-phase ceramics (BCP) with hydroxyapatite (HAp: Ca 10 [PO 4 ] 6 [OH] 2 ) and β-TCP, from carbonized fowl droppings via one-pot hydrothermal reactions. It occurred to us to use the residue, mineral traces and organic compounds in fowl droppings obtained by carbonization as control reagents for the synthesis reaction. Through this selective generation of the single-phase Mg-doped β-TCP, a stratified formation that resembled a natural nacreous layer was achieved. Further, we were able to produce only HAp/32.4% β-TCP possessing comparatively high mechanical strength in two-phase BCP ceramics by using incinerated fowl droppings prepared from carbonized fowl droppings sintered in air at 800 °C. In the adsorption of ammonia gas, biomimetic calcium phosphate compounds synthesized from fowl droppings have comparable loading capacities to activated carbon.

Sintering and Properties of Dense Manganese-Doped Calcium Phosphate Bioceramics Prepared Using Sol-Gel Derived Nanopowders

Dense manganese-doped biphasic calcium phosphate (Mn-BCP) ceramics were fabricated via uniaxial pressing using the sol-gel derived powders. The compacted discs were sintered in ambient atmosphere with temperatures ranging from 800°C to 1400°C. Manganese (Mn) level was varied in the range of 0.6, 1.9, 4.3, and 11.9 mol%, and its effect on physical and mechanical properties of the dense samples were investigated. All dense samples have been proved to show HA and β-TCP phases only. Mn doping has shifted the onset of the sintering temperature of the BCP, leading to the improved densification of BCP ceramics. The relative density also increased with sintering temperature. Considerable grain growth has been observed for Mn-doped BCP samples when compared to the undoped BCP. Furthermore, 11.9 mol% Mn-doped BCP dense samples showed the maximum hardness of 6.66 GPa compared to 2.89 GPa for the undoped BCP. The incorporation of Mn was also found to be beneficial in enhancing the fracture toughness of BCP throughout the temperature range employed. This study has shown that Mn doping was effective in improving the sintering properties of BCP without affecting the phase stability.