Tricalcium Phosphate Scaffolds Research Articles

Bone Regeneration Capability of 3D Printed Ceramic Scaffolds.

In this study, we evaluated the bone regenerative capability of a customizable hydroxyapatite (HA) and tricalcium phosphate (TCP) scaffold using a digital light processing (DLP)-type 3D printing system. Twelve healthy adult male beagle dogs were the study subjects. A total of 48 defects were created, with two defects on each side of the mandible in all the dogs. The defect sites in the negative control group (sixteen defects) were left untreated (the NS group), whereas those in the positive control group (sixteen defects) were filled with a particle-type substitute (the PS group). The defect sites in the experimental groups (sixteen defects) were filled with a 3D printed substitute (the 3DS group). Six dogs each were exterminated after healing periods of 4 and 8 weeks. Radiological and histomorphometrical evaluations were then performed. None of the groups showed any specific problems. In radiological evaluation, there was a significant difference in the amount of new bone formation after 4 weeks (p < 0.05) between the PS and 3DS groups. For both of the evaluations, the difference in the total amount of bone after 8 weeks was statistically significant (p < 0.05). There was no statistically significant difference in new bone between the PS and 3DS groups in both evaluations after 8 weeks (p > 0.05). The proposed HA/TCP scaffold without polymers, obtained using the DLP-type 3D printing system, can be applied for bone regeneration. The 3D printing of a HA/TCP scaffold without polymers can be used for fabricating customized bone grafting substitutes.

Optimization of culture duration of bone marrow cells before transplantation with a β-tricalcium phosphate/recombinant collagen peptide hybrid scaffold.

IntroductionCurrently, various kinds of materials are used for the treatment of bone defects. In general, these materials have a problem of formativeness. The three -dimensional (3D) printing technique has been introduced to fabricate artificial bone with arbitrary shapes, but poor bone replacement is still problematic.Our group has created a β⁻tricalcium phosphate (β⁻TCP) scaffold by applying 3D printing technology. This scaffold has an arbitrary shape and an internal structure suitable for cell loading, growth, and colonization. The scaffold was coated with a recombinant collagen peptide (RCP) to promote bone replacement.As indicated by several studies, cells loaded to scaffolds promote bone regeneration, especially when they are induced osteoblastic differentiation before transplantation. In this study, culture duration for bone marrow cells was optimized before being loaded to this new scaffold material.MethodBone marrow cells isolated from C57BL/6J mice were subjected to osteogenic culture for 4, 7, and 14 days. The differentiation status of the cells was examined by alkaline phosphatase staining, alizarin red staining, and real-time RT-PCR for differentiation markers. In addition, the flow of changes in the abundance of endothelial cells and monocytes was analyzed by flow cytometry according to the culture period of bone marrow cells.Next, cells at days 4, 7, and 14 of culture were placed on a β-TCP/RCP scaffold and implanted subcutaneously into the back of C57BL/6J mice. Grafts were harvested and evaluated histologically 8 weeks later. Finally, Cells cultured for 7 days were also transplanted subperiosteally in the skull of the mouse with scaffolds.ResultAlkaline phosphatase staining was most prominent at 7 days, and alizarin red staining was positive at 14 days. Real-time RT-PCR revealed that Runx2 and Alp peaked at 7 days, while expression of Col1a1 and Bglap was highest at 14 days. Flow cytometry indicated that endothelial cells increased from day 0 to day 7, while monocytes increased continuously from day 0 to day 14. When transplanted into mice, the scaffold with cells cultured for 7 days exhibited the most prominent osteogenesis. The scaffold, which was transplanted subperiosteally in the skull, retained its shape and was replaced with regenerated bone over a large area of the field of view.ConclusionOsteoblasts before full maturation are most efficient for bone regeneration, and the pre-culture period suitable for cells to be loaded onto a β-TCP/RCP hybrid scaffold is approximately 7 days.This β-TCP/RCP hybrid scaffolds will also be useful for bone augmentation.

Sintering effects of bioactive glass incorporation in tricalcium phosphate scaffolds

The influence of using bioactive glass as a sintering aid in the production of tricalcium phosphate (TCP) scaffolds was investigated. The scaffolds were fabricated by sponge replication followed by sintering in a range of temperatures from 1150 to 1300 °C. Morphological investigations by SEM and micro-computed tomography showed that the scaffolds exhibited a three-dimensional trabecular architecture mimicking that of cancellous bone, with high porosity (about 80 vol%) and highly-interconnected macropores with mean pore size of 314 μm. Apart from playing a role in improving the mechanical properties of the scaffolds, glass was shown to enhance the stability of β-TCP by increasing the β → α phase transition temperature.

Bone-like structure by modified freeze casting

Freeze casting has emerged as one of the most promising manufacturing methods to fabricate porous scaffolds in recent years. This is due to various reasons which include a wide range of materials which can be used in this process, easiness of the process, etc. One of the major objectives of this work was to fabricate bone-like structure by using a modified freeze casting process. In this work, Hydroxyapatite and Tricalcium phosphate scaffolds with bone-like structure were fabricated by understanding and utilizing the basic physics of freeze casting. Thermal conductivity of the base plate is a crucial factor for obtaining controlled pore and porosity distribution in a porous scaffold. It was found that designing the base plate with variable thermal conductivity has led to the formation of bone-like structure. Porous scaffolds were quantitatively analyzed for pore size and porosity distribution at center and circumference. Porosity at circumference was observed to be approximately dropped by 55%, a similar trend was seen for pore size. Therefore, it was significant evidence that modified freeze casting has capable in fabricating bone-like structures with ease and good control. This will open many new applications of porous scaffolds in biomedical, energy devices, chemical catalyst and many more.

Effects of Cryopreservation on Cell Metabolic Activity and Function of Biofabricated Structures Laden with Osteoblasts.

Biofabrication and maturation of bone constructs is a long-term task that requires a high degree of specialization. This specialization falls onto the hierarchy complexity of the bone tissue that limits the transfer of this technology to the clinic. This work studied the effects of the short-term cryopreservation on biofabricated osteoblast-containing structures, with the final aim to make them steadily available in biobanks. The biological responses studied include the osteoblast post-thawing metabolic activity and the recovery of the osteoblastic function of 3D-bioprinted osteoblastic structures and beta tricalcium phosphate (β-TCP) scaffolds infiltrated with osteoblasts encapsulated in a hydrogel. The obtained structures were cryopreserved at −80 °C for 7 days using dimethyl sulfoxide (DMSO) as cryoprotectant additive. After thawing the structures were cultured up to 14 days. The results revealed fundamental biological aspects for the successful cryopreservation of osteoblast constructs. In summary, immature osteoblasts take longer to recover than mature osteoblasts. The pre-cryopreservation culture period had an important effect on the metabolic activity and function maintain, faster recovering normal values when cryopreserved after longer-term culture (7 days). The use of β-TCP scaffolds further improved the osteoblast survival after cryopreservation, resulting in similar levels of alkaline phosphatase activity in comparison with the non-preserved structures. These results contribute to the understanding of the biology of cryopreserved osteoblast constructs, approaching biofabrication to the clinical practice.

Factors governing the dimensional accuracy and fracture modes under compression of regular and shifted orthogonal scaffolds

Direct ink writing allows controlling the structure of tissue engineering scaffolds. The aim of this work was to study the effects of the in silico pattern design on the dimensional accuracy of tricalcium phosphate scaffolds and of the loading direction on the compressive strength and fracture modes. Regular and shifted scaffolds showed anisotropic shrinkage during drying and isotropic shrinkage during sintering. Shifted layers induced bending stresses when compressed longitudinally, resulting in lower compressive strength. The transverse Young’s modulus and compressive strength were higher than the longitudinal ones for both regular and shifted structures. Strand deflections were more pronounced in shifted structures. Finite element modelling suggested that such deflections considerably increased the effective transverse modulus of the shifted scaffolds, thus increasing the related compressive strength. In conclusion, shifted scaffolds performed similarly to regular ones in the transverse direction but were less mechanically reliable under the longitudinal direction.

Efficacy of three-dimensionally printed polycaprolactone/beta tricalcium phosphate scaffold on mandibular reconstruction

It has been demonstrated that development of three-dimensional printing technology has supported the researchers and surgeons to apply the bone tissue engineering to the oromandibular reconstruction. In this study, poly caprolactone/beta tricalcium phosphate (PCL/β-TCP) scaffolds were fabricated by multi-head deposition system. The feasibility of the three-dimensionally (3D) -printed PCL/β-TCP scaffolds for mandibular reconstruction was examined on critical-sized defect of canine mandible. The scaffold contained the heterogeneous pore sizes for more effective bone ingrowth and additional wing structures for more stable fixation. They were implanted into the mandibular critical-sized defect of which periosteum was bicortically resected. With eight 1-year-old male beagle dogs, experimental groups were divided into 4 groups (n = 4 defects per group, respectively). (a) no further treatment (control), (b) PCL/β-TCP scaffold alone (PCL/TCP), (c) PCL/β-TCP scaffold with recombinant human bone morphogenetic protein-2 (rhBMP-2) (PCL/TCP/BMP2) and (d) PCL/β-TCP scaffold with autogenous bone particles (PCL/TCP/ABP). In micro-computed tomography, PCL/TCP/BMP2 and PCL/TCP/ ABP groups showed significant higher bone volume in comparison to Control and PCL/TCP groups (P < 0.05). In histomorphometric analysis, a trend towards more bone formation was observed in PCL/TCP/BMP2 and PCL/TCP/ABP groups, but the results lacked statistical significance (P = 0.052). Within the limitations of the present study, 3D-printed PCL/β-TCP scaffolds showed acceptable potential for oromandibular reconstruction.

Research on sintering process of tricalcium phosphate bone tissue engineering scaffold based on three-dimensional printing

Tricalcium phosphate (TCP) is one of the most widely used bioceramics for constructing bone tissue engineering scaffold. The three-dimensional (3D) printed TCP scaffold has precise and controllable pore structure, while with the limitation of insufficient mechanical properties. In this study, we investigated the effect of sintering temperature on the mechanical properties of 3D-printed TCP scaffolds in detail, due to the important role of the sintering process on the mechanical properties of bioceramic scaffolds. The morphology, mass and volume shrinkage, porosity, mechanical properties and degradation property of the scaffold was studied. The results showed that the scaffold sintered at 1 150℃ had the maximum volume shrinkage, the minimum porosity and optimal mechanical strength, with the compressive strength of (6.52 ± 0.84) MPa and the compressive modulus of (100.08 ± 18.6) MPa, which could meet the requirements of human cancellous bone. In addition, the 1 150℃ sintered scaffold degraded most slowly in the acidic environment compared to the scaffolds sintered at the other temperatures, demonstrating its optimal mechanical stability over long-term implantation. The scaffold can support bone mesenchymal stem cells (BMSCs) adherence and rapid proliferation and has good biocompatibility. In summary, this paper optimizes the sintering process of 3D printed TCP scaffold and improves its mechanical properties, which lays a foundation for its application as a load-bearing bone.

Cytotoxic and osteogenic effects of crocin and bicarbonate from calcium phosphates for potential chemopreventative and anti-inflammatory applications in vitro and in vivo.

Delayed healing and nonhealing of bone defects or resected bone sites remains an important clinical concern in the biomedical field. Osteosarcoma is one of the most common types of primary bone cancers. Among calcium phosphates, hydroxyapatite (HA) and tricalcium phosphate (TCP) are the most widely used in various biomedical applications for bone reconstruction and replacement. In this study, crocin, saffron's natural bioactive and anti-inflammatory molecule, and bicarbonate, a neutralizing agent, were directly loaded onto HA disks to evaluate their in vitro release and effect on human osteoblast and osteosarcoma cell lines. This was assessed through release, initial toxicity, drug optimization, final toxicity studies and in vivo anti-inflammatory assessment through H&E indexing. It is hypothesized that the release of crocin, bicarbonate, and the dual release of both agents will decrease osteosarcoma cellular viability with no effect on osteoblast cells. A plateaued release of crocin and bicarbonate was achieved over seven weeks in physiological and acidic environments, where bicarbonate was shown to modulate the release of crocin. Through morphological characterization and MTT assay analysis, bicarbonate showed no toxicity to human fetal osteoblast (hFOB) cells and crocin significantly enhanced osteoblast proliferation. Through drug concentration optimization, all drug loaded samples decreased human osteosarcoma (MG-63) viability by 50% compared to control samples by Day 11, with clear changes in cell spreading and morphology. Moreover, 3D printed TCP scaffolds loaded with crocin and bicarbonate were tested in vivo in order to assess their preliminary effects on inflammation in a rat distal femur model at 4 days. Lower inflammatory cellular recruitment was achieved in the presence of crocin and bicarbonate, compared to the control. These results suggest a pro-apoptotic mechanism against osteosarcoma as well as anti-inflammatory properties of crocin and bicarbonate, elucidating a potential application for osteosarcoma regulation and wound healing for bone tissue regeneration applications.

Improvement of Bone Formation in Rats with Calvarial Defects by Modulating the Pore Size of Tricalcium Phosphate Scaffolds

The use of multi-porous scaffolds for bone tissue engineering has been shown to improve osteogenesis. Although the exact mechanisms by which these scaffolds promote new bone formation have not yet been recognized well, related hypotheses can be found in many previous studies. The aim of this study was to examine the influence of the modulation of the pore size of beta- TCP ceramics on osteogenic differentiation in rats with calvarial defects. Treatments with macro- and meso-sized particles of NaCl, which was used as a porogen, were carried out during scaffold manufacturing, and the pore sizes of the beta-TCP scaffolds were measured by SEM. New bone formation was evaluated by Micro-CT, H&E staining, and immuno-histochemical analysis at week 4 after the operation. It was observed that the multi porosity of beta-TCP ceramics was controlled by treating the scaffolds with NaCl particles of two sizes (500–800 μm and 10–50 μm) during the firing process. Histological and immunohistochemical analysis of type 1 collagen and osteocalcin protein expression showed that the new bone formation and mineralization in case of the multi-porous beta-TCP ceramics comprising macro-and meso-sized pores were significantly higher than those in case of single porous macro- or meso-sized scaffolds. In conclusion, the distribution and size of the pores, as well as the surface structure of the scaffolds, may play an important role for osteogenic differentiation in vivo.

Regulation of Osteogenic Markers at Late Stage of Osteoblast Differentiation in Silicon and Zinc Doped Porous TCP.

Calcium phosphates (CaPs) are one of the most widely used synthetic materials for bone grafting applications in the orthopedic industry. Recent trends in synthetic bone graft applications have shifted towards the incorporation of metal trace elements that extend the performance of CaPs to have osteoinductive properties. The objective of this study is to investigate the effects of silicon (Si) and zinc (Zn) dopants in highly porous tricalcium phosphate (TCP) scaffolds on late-stage osteoblast cell differentiation markers. In this study, an oil emulsion method is utilized to fabricate highly porous SiO2 doped β-TCP (Si-TCP) and ZnO doped β-TCP (Zn-TCP) scaffolds through the incorporation of 0.5 wt.% SiO2 and 0.25 wt.% ZnO, respectively, to the β-TCP scaffold. Reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) is utilized to analyze the mRNA expression of osteoprotegerin (OPG), receptor activator of nuclear kappa beta ligand (RANKL), bone morphogenetic protein 2 (BMP2), and runt-related transcription factor 2 (Runx2) at the later stage of osteoblast differentiation, day 21 and day 28. Results show that the addition of Si and Zn to the β-TCP structure inhibited the β to α-TCP phase transformation and enhance the density without affecting the dissolution properties. Normal BMP-2 and Runx2 transcriptions are observed in both Si-TCP and Zn-TCP scaffolds at the initial time point, as demonstrated by RT-qPCR. Moreover, the addition of both Si and Zn positively regulate the osteoprotegerin: receptor activator of nuclear factor k-β ligand (OPG:RANKL) ratio at 21-days for Si-TCP and Zn-TCP scaffolds. These results demonstrate the effects of Si and Zn doped porous β-TCP scaffolds on the upregulation of osteoblast marker gene expression including OPG, RANKL, BMP-2, and Runx2, indicating the role of trace elements on the effective regulation of late-stage osteoblast cell differentiation markers.

Load-bearing PTMC-beta tri-calcium phosphate and dexamethasone biphasic composite microsphere scaffolds for bone tissue engineering

In bone tissue engineering, beta-tricalcium phosphate acts as a building block for biomaterials to increases the mechanical properties of biomaterials. Building on our previous scaffold based on PTMC microspheres, we investigated the characteristics of microsphere scaffolds loaded with inorganic particles and the release profile of biphasic drug-loaded microsphere scaffolds. In this investigation, a three-dimensional PTMC/TCP-DEX microsphere scaffold with total porosity of about 50% and pore sizes ranging from 120 to 180 μm was prepared through employing solvent combined with a thermal technique. The addition of β-TCP reduces PTMC microsphere creep and also dramatically improves the mechanical properties of the scaffold (compressive modulus of 18 MPa). Moreover, the PTMC/TCP-DEX scaffold exhibited average porosity (approximately 100 μm) and high water absorption (60%), which are advantageous for release of drug and bioactive substance.

Rabbit palatum-derived mesenchymal progenitor cells tri-lineage differentiation on 2D substrates and 3D printed constructs.

Hard palate, developed by embryo neural crest stem cells, is a tissue with strong regenerative abilities. It is considered an abundant source of progenitor cells, forming various mesenchymal tissues. Rabbits are more suitable models than murine animals for regenerative preclinical study of the head and neck, owing to their larger size. However, there are no reports of the existence or characteristics of neural crest stem cells in the hard palate of rabbits. In this study, we demonstrate for the first time the presence of nestin-, Sox2-, and p75-positive neural crest stem cells obtained from the hard palate of rabbits and the properties of these cells. Flow cytometry analysis revealed that CD29, CD44, and CD81 were positive; and CD11b, CD34, and CD90 were negative on the ex vivo expanded palatal progenitor cells. Finally, we differentiated them into cells of mesenchymal lineages (bone, cartilage, and fat) in vitro, and in three-dimensional fabricated polycaprolactone and polycaprolactone-tricalcium phosphate scaffolds. Taken together, our data showed the existence of rabbit palatum-derived mesenchymal progenitor cells, and successful fabrication of progenitor cell-loaded biodegradable scaffold using three-dimensional printing. This study will open avenues for new tissue engineering strategies for cell therapy using three-dimensional printing with scaffolds for reconstruction of head and neck defects.

Application of high resolution DLP stereolithography for fabrication of tricalcium phosphate scaffolds for bone regeneration

Bone regeneration requires porous and mechanically stable scaffolds to support tissue integration and angiogenesis, which is essential for bone tissue regeneration. With the advent of additive manufacturing processes, production of complex porous architectures has become feasible. However, a balance has to be sorted between the porous architecture and mechanical stability, which facilitates bone regeneration for load bearing applications. The current study evaluates the use of high resolution digital light processing (DLP) -based additive manufacturing to produce complex but mechanical stable scaffolds based on β-tricalcium phosphate (β-TCP) for bone regeneration. Four different geometries: a rectilinear Grid, a hexagonal Kagome, a Schwarz primitive, and a hollow Schwarz architecture are designed with 400 μm pores and 75 or 50 vol% porosity. However, after initial screening for design stability and mechanical properties, only the rectilinear Grid structure, and the hexagonal Kagome structure are found to be reproducible and showed higher mechanical properties. Micro computed tomography (μ-CT) analysis shows <2 vol% error in porosity and <6% relative deviation of average pore sizes for the Grid structures. At 50 vol% porosity, this architecture also has the highest compressive strength of 44.7 MPa (Weibull modulus is 5.28), while bulk specimens reach 235 ± 37 MPa. To evaluate suitability of 3D scaffolds produced by DLP methods for bone regeneration, scaffolds were cultured with murine preosteoblastic MC3T3-E1 cells. Short term study showed cell growth over 14 d, with more than two-fold increase of alkaline phosphatase (ALP) activity compared to cells on 2D tissue culture plastic. Collagen deposition was increased by a factor of 1.5–2 when compared to the 2D controls. This confirms retention of biocompatible and osteo-inductive properties of β-TCP following the DLP process. This study has implications for designing of the high resolution porous scaffolds for bone regenerative applications and contributes to understanding of DLP based additive manufacturing process for medical applications.

Regional gene therapy with 3D printed scaffolds to heal critical sized bone defects in a rat model.

The objective of the present study was to assess the ability of transduced rat bone marrow cells (RBMCs) that overexpress BMP-2 loaded on a three-dimensionally (3D) printed scaffold to heal a critical sized rat femoral defect. Tricalcium phosphate (TCP) scaffolds were 3D printed to fit a critical sized rat femoral defect. The RBMCs were transduced with a lentiviral (LV) vector expressing BMP-2 or GFP. The rats were randomized into the following treatment groups: (1) RBMC/LV-BMP-2 + TCP, (2) RBMC/LV-GFP + TCP, (3) nontransduced RBMCs + TCP, (4) TCP scaffold alone. The animals were euthanized at 12 weeks and evaluated with plain radiographs, microcomputed tomography (micro-CT), histology, histomorphometry, and biomechanically. Each LV-BMP-2 + TCP treated specimen demonstrated complete healing of the femoral defect on plain radiographs and micro-CT. No femurs healed in the control groups. Micro-CT demonstrated that LV-BMP-2 + TCP treated femoral defects formed 197% more bone volume compared to control groups (p < 0.05). Histologic analysis demonstrated bone formation across the TCP scaffold, uniting the femoral defect on both ends in the LV-BMP-2 + TCP treated specimens. Biomechanical assessment demonstrated similar stiffness (p = 0.863), but lower total energy to failure, peak torque, and peak displacement (p < 0.001) of the femurs treated with LV-BMP-2 + TCP when compared to the contralateral control femur. Regional gene therapy induced overexpression of BMP-2 via transduced RBMCs combined with an osteoconductive 3D printed TCP scaffold can heal a critically sized femoral defect in an animal model. The combination of regional gene therapy and 3D printed osteoconductive scaffolds has significant clinical potential to enhance bone regeneration.

Vitamin D3 Release from Traditionally and Additively Manufactured Tricalcium Phosphate Bone Tissue Engineering Scaffolds.

Bone is a randomized, complex porous network which researchers have tried to mimic within bone tissue engineering scaffolds. The objective of this study was to understand the effects of random and controlled scaffold porosity on the release kinetics of vitamin D3 to determine if a designed porous structure was comparable in effectiveness on osteoblast proliferation to the randomized essence of natural bone. In this study, porous tricalcium phosphate (TCP) scaffolds were prepared by fugitive material removal method using naphthalene and 3D printing to model random and controlled porosity, respectively. Scaffold comparison was made based on open pore volume percentage of which naphthalene scaffolds had 45.8 ± 1.5% and 3D printed scaffolds had 48.9 ± 2.5%, Comparative analysis of traditional bioceramic processing to additive manufacturing is limited especially regarding drug release kinetics. Results showed the naphthalene scaffold surface area was only 0.3% that of 3D printed scaffolds due to the lower open pore interconnectivity. This increase in surface area produced higher release of drug and osteoblast proliferation in 3D printed scaffolds comparatively. By 11days, osteoblast proliferation was enhanced by 64% from scaffolds manufactured using 3D printing compared to traditional processing. Understanding the effects of processing methods of TCP scaffolds on the release kinetics of vitamin D3 and the system effects on cells can aid in low load bearing applications for bone tissue engineering.

Enhancement of mechanical properties of 3D-plotted tricalcium phosphate scaffolds by rapid sintering

This work explores the rapid sintering of 3D-plotted tricalcium phosphate (TCP) scaffolds with the aim of getting the on-demand scaffold fabrication closer towards the clinical practice. The sintering trajectories of TCP scaffolds at 1100 and 1200 °C show that 10 min of reactive sintering together with a fast heating rate (100 °C min-1) result in a superior densification without significant grain growth, increasing the compressive strength 1.5–2.5 times. Furthermore, hardness and elastic modulus increase 8 times as compared to conventional sintering. The mechanical performance is not compromised by the formation of alpha-TCP at 1200 °C, since it originates by chemical reaction instead of a phase transformation mechanism, avoiding cracking due to crystalline lattice expansion.

Three-dimensional TCP scaffolds enriched with Erythropoietin for stimulation of vascularization and bone formation

In our work, we conducted studies to evaluate the reconstruction of an artificially created critical radial defect in rats with the use of tri-calcium phosphate scaffold enriched with erythropoietin (ЕРО). A model of the bone defect on the radius forearm in rats of a critical size has been developed. This model allows to conduct the study without the use of osteosynthesis. EPO is a well-known hormone which regulates formation of the red blood cells (2, 3). ЕРО increases the expression of VEGF and promotes angiogenesis (3, 4). Therefore, EPO may have a great potential for use as a growth factor for angiogenesis and play its particular role in the bone tissue regeneration. There are no published studies that describe interactions between EPO and biomaterials for development of the bone tissue. Thus, the purpose of this study was to evaluate the interaction between EPO and tri-calcium phosphate scaffold (TCP) with a well-studied biocompatibility and the given porosity, as well as to determine whether EPO in the enriched TCP will promote the bone regeneration. The X-ray analysis was performed in 10 days, 28 days and 3 months after the surgery. The histological analysis was performed in 28 days and 3 months after the surgery. The results have demonstrated that the complex of TCP scaffold with erythropoietin is a promising growth factor for stimulating the development of the bone tissue, since the TCP scaffold enriched with erythropoietin is very easy to obtain in a non-invasive and simple procedure, as well as the complex promotes interaction with the surrounding tissues and induces the bone regeneration.

Dual therapeutic cobalt-incorporated bioceramics accelerate bone tissue regeneration

Bone grafting on defects caused by trauma or tumor stimulates bone regeneration, a complex process requiring highly orchestrated cell–signal interactions. Bone vascular growth is coupled with osteogenesis, but less is known about the interplay between angiogenesis and osteogenesis. Understanding this relationship is relevant to improved bone regeneration. Here, tricalcium phosphate (TCP) scaffolds doped with varying concentration of cobalt (Co-TCP) were designed to investigate the dosage effect of vascularization on bone formation. The surface structure, phase composition, mechanical features, and chemical composition were investigated. Co doping improved the mechanical properties of TCP. Co-TCP, particularly 2% and 5% Co-TCP, boosted cell viability of bone marrow stromal cells (BMSCs). The 2% Co-TCP promoted alkaline phosphatase activity, matrix mineralization, and expression of osteogenic genes in BMSCs in vitro. However, excessive Co doping decreased TCP-induced osteogenesis. Meanwhile, Co-TCP dose-dependently favored the growth and migration of human umbilical vein endothelial cells (HUVECs), and the expression of vascular endothelial growth factor (VEGF). The 2% Co-TCP significantly shrank the defect area in rat alveolar bone compared with TCP. Smaller bone volume and more abundant blood vessels were observed for 5% Co-TCP compared with 2% Co-TCP. The CD31 immunostaining in the 5% Co-TCP group was more intense than the other two groups, indicating of the increment of endothelium cells. Besides, 5% Co-TCP led to mild inflammatory response in bone defect area. Overall, TCP doped appropriately with Co has positive effect on osteogenesis, while excessive Co suppressed osteoblast differentiation and bone formation. These data indicate that vascularization within a proper range promotes osteogenesis, which may be a design consideration for bone grafts.

Load-bearing biodegradable polycaprolactone-poly (lactic-co-glycolic acid)- beta tri-calcium phosphate scaffolds for bone tissue regeneration.

A biodegradable scaffold with tissue ingrowth and load-bearing capabilities is required to accelerate the healing of bone defects. However, it is difficult to maintain the mechanical properties as well as biodegradability and porosity (necessary for bone ingrowth) at the same time. Therefore, in the present study, polycaprolactone (PCL) and poly(lactic-co-glycolic acid) (PLGA5050) were mixed in varying ratio and incorporated with 20 wt.% βTCP. The mixture was shaped under pressure into originally non-porous cylindrical constructs. It is envisioned that the fabricated constructs will develop porosity with the time-dependent biodegradation of the polymer blend. The mechanical properties will be sustained since the decrease in mechanical properties associated with the dissolution of the PLGA and the formation of the porous structure will be compensated with the new bone formation and ingrowth. To prove the hypothesis, we have systematically studied the effects of samples composition on the time-dependent dissolution behavior, pore formation, and mechanical properties of the engineered samples, in vitro. The highest initial (of as-prepared samples) values of the yield strength (0.021±0.002 GPa) and the Young's modulus (0.829±0.096 GPa) were exhibited by the samples containing 75 wt.% of PLGA. Increase of the PLGA concentration from 25 wt.% to 75 wt.% increased the rate of biodegradation by a factor of 3 upon 2 weeks in phosphate buffered saline (1× PBS). The overall porosity and the pore sizes increased with the dissolution time indicating that the formation of in-situ pores can indeed enable the migration of cells followed by vascularization and bone growth.