Porous β-TCP Scaffolds Research Articles

ZnO-doped β-TCP ceramic-based scaffold promotes osteogenic and antibacterial activity

β-Tricalcium phosphate (β-TCP) scaffolds, which are synthetic bone graft materials, have been explored as a potential solution in the healing of bone deformities due to their acceptable degradation rate and ability to support bone growth. However, these scaffolds have limitations such as poor mechanical properties, to stimulate bone growth, which increases the risk of infection after implantation. To overcome these issues, a new type of biomedical scaffold was developed that incorporated zinc oxide (ZnO) particles into β-TCP using wet chemical techniques. The scaffolds were created using sintering to produce porous β-TCP scaffolds with good connectivity. The addition of zinc oxide as a dopant significantly improved the biophysical properties of the scaffolds, with higher concentrations of zinc oxide, leading to better cell adhesion and proliferation. The scaffolds placed in simulated body fluid demonstrated exceptional ability to promote bone growth and regeneration by developing a bone-like apatite layer on their surfaces. The mechanical and physical properties of the scaffolds were effectively assessed using X-ray diffraction and scanning electron microscopy analyses. To validate the efficacy of the specimen in preventing microbial growth and promoting bone growth, a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test and gene expression investigation were conducted. Zinc oxide-doped β-TCP scaffolds are envisaged to show enormous potential for use in future bone-healing applications.

Branched Channels in Porous β-Tricalcium Phosphate Scaffold Promote Vascularization.

Rapid and efficient vascularization is still considerably challenging for a porous β-tricalcium phosphate (β-TCP) scaffold to achieve. To overcome this challenge, branched channels were created in the porous β-TCP scaffold by using 3D printing and a template-casting method to facilitate the instant flow of blood supply. Human bone mesenchymal stem cells (hBMSCs) and human umbilical vein endothelial cells (HUVECs) were seeded in the channeled porous scaffolds and characterized through a double-stranded DNA (dsDNA) assay, alkaline phosphatase (ALP) assay, and cell migration. Channeled porous β-TCP scaffolds were then implanted in the subcutaneous pockets of mice. Histological staining and immunohistochemical staining on vascularization and bone-related markers were carried out on the embedded paraffin sections. Results from in vitro experiments showed that branched channels significantly promoted HUVECs' infiltration, migration, proliferation, and angiogenesis, and also promoted the proliferation and osteogenesis differentiation of hBMSCs. In vivo implantation results showed that, in the early stage after implantation, cells significantly migrated into branched channeled scaffolds. More matured blood vessels formed in the branched channeled scaffolds compared to that in nonchanneled and straight channeled scaffolds. Beside promoting vascularization, the branched channels also stimulated the infiltration of bone-related cells into the scaffolds. These results suggested that the geometric design of branched channels in the porous β-TCP scaffold promoted rapid vascularization and potentially stimulated bone cells recruitment.

Studying the combined effect of layer thickness and solid loading percentage for improving the compressive strength of 3D printed β-TCP scaffold by LCD technique

Customized 3D printed bio-ceramic scaffolds with complex shapes can be fabricated by Liquid Crystal Display (LCD) technology. In this study we investigated the combined effect of the solid loading percentage of the β-Tricalcium phosphate (β-TCP) bio-ceramic powder and the 3D printing layer thickness on the compressive strength of the 3D printed bio-ceramic scaffolds using LCD technique. Three different high solid loadings (40, 60 and 80 vol%) of β-TCP were mixed with resin in the presence of Oleic acid prior to the 3D printing. The β-TCP:resin slurry was used to fabricate scaffolds by using three different layer thicknesses (50 μm, 100 μm and 150 μm). The 3D printed green scaffolds were thermally debinded at 530 °C for 8 h and sintered at 1000 °C for 6 h based on the TGA and DSC thermal analysis of the β-TCP-resin slurry. The x-ray diffraction (XRD) and the Fourier transform infrared (FTIR) spectroscopy analysis confirmed that the β-TCP structure is preserved after scaffold fabrication. The Scanning Electron Microscopy (SEM) analysis showed the surface morphology of the scaffolds with internal pores, micro porosity, and localized delamination. The main finding of the results suggests that decreasing the layer thickness and the solid loading will enhance the compressive strength of the scaffold. Maximum compressive strength attained was (0.19 ± 0.01 MPa) for scaffolds with 40 % solid loadings, layer thickness of 50 μm and porosity 83.49 %. These results demonstrate the potential of using the low-cost LCD 3D printing in fabricating a customized porous β-TCP scaffolds for bone tissue engineering.

Prussian blue-integrated porous β-TCP scaffolds for photothermal anti-tumor and NO-augmented osteogenesis

Prussian blue-integrated porous β-TCP scaffolds for photothermal anti-tumor and NO-augmented osteogenesis

Reconstructing avascular necrotic femoral head through a bioactive β-TCP system: From design to application

A variety of techniques have been used for treating avascular necrosis of the femoral head (ANFH), but have frequently failed. In this study, we proposed a β-TCP system for the treatment of ANFH by boosting revascularization and bone regeneration. The angio-conductive properties and concurrent osteogenesis of the highly interconnected porous β-TCP scaffold were revealed and quantified through an in vivo model that simulated the ischemic environment of ANFH. Mechanical test and finite element analysis showed that the mechanical loss caused by tissue necrosis and surgery was immediately partially compensated after implantation, and the strength of the operated femoral head was adaptively increased and eventually returned to normal bone, along with continuous material degradation and bone regeneration. For translational application, we further conducted a multi-center open-label clinical trial to assess the efficacy of the β-TCP system in treating ANFH. Two hundred fourteen patients with 246 hips were enrolled for evaluation, and 82.1% of the operated hips survived at a 42.79-month median follow-up. The imaging results, hip function, and pain scores were dramatically improved compared to preoperative levels. ARCO stage Ⅱ disease outperformed stage Ⅲ in terms of clinical effectiveness. Thus, bio-adaptive reconstruction using the β-TCP system is a promising hip-preserving strategy for the treatment of ANFH.

A comprehensive review of the effects of porosity and macro- and micropore formations in porous β-TCP scaffolds on cell responses

A comprehensive review of the effects of porosity and macro- and micropore formations in porous β-TCP scaffolds on cell responses

Efficacy of soluble lansoprazole-impregnated beta-tricalcium phosphate for bone regeneration

The proton pump inhibitor lansoprazole has been previously identified to upregulate the expression and transcriptional activity of runt-related transcription factor 2 (Runx2) that promotes lineage commitment and differentiation of osteoprogenitor cells. We could not elicit the expected efficacy of insoluble lansoprazole in enhancing osteogenesis when combined with beta-tricalcium phosphate (β-TCP) bone substitutes. This study aimed to evaluate the effects of soluble lansoprazole on in vitro osteoblastogenesis and new bone formation in vivo. Commercially available human mesenchymal stem cells or patient-derived bone marrow-derived stromal cells were treated with 20 µM of soluble lansoprazole at the beginning of osteogenic induction. Soluble lansoprazole-impregnated β-TCP materials were embedded in the cortical bone defect model of rabbits. Rabbits were sacrificed four weeks postoperatively and undecalcified bone specimens were prepared for evaluation of intra-material new bone formation. Only a 1-day treatment with soluble lansoprazole facilitated osteoblastic differentiation and matrix calcium deposition when added to undifferentiated human mesenchymal stromal cells at the beginning of the osteogenic differentiation. Soluble lansoprazole dose-dependently accelerated intra-material new bone formation when being impregnated with porous β-TCP artificial bones. Local use of soluble lansoprazole can be applicable for fracture and bone defect repair when combined with porous β-TCP scaffolds.

Establishment and biological effect evaluation of prevascularized porous β-tricalcium phosphate tissue engineered bone

To evaluate the biological effect on vascularization during bone repair of prevascularized porous β-tricalcium phosphate (β-TCP) tissue engineered bone (hereinafter referred to as prevascularized tissue engineered bone), which was established by co-culture of endothelial progenitor cells (EPCs) and bone marrow mesenchymal stem cells (BMSCs) based on tissue engineering technology. EPCs and BMSCs were isolated from iliac bone marrow of New Zealand white rabbits by density gradient centrifugation and differential adhesion method. The cells were identified by immunophenotypic detection, BMSCs-induced differentiation, and EPCs phagocytosis. After identification, the third-generation cells were selected for subsequent experiments. First, in vitro tubule formation in EPCs/BMSCs direct contact co-culture (EPCs/BMSCs group) was detected by Matrigel tubule formation assay and single EPCs (EPCs group) as control. Then, the prevascularized tissue engineered bone were established by co-culture of EPCs/BMSCs in porous β-TCP scaffolds for 7 days (EPCs/BMSCs group), taking EPCs in porous β-TCP scaffolds as a control (EPCs group). Scanning electron microscopy and laser scanning confocal microscopy were used to observe the adhesion, proliferation, and tube formation of cells. Femoral condyle defect models of 12 New Zealand white rabbits were used for implantation of prevascularized tissue engineered bone as the experimental group ( n=6) and porous β-TCP scaffold as the control group ( n=6). The process of vascularization of β-TCP scaffolds were observed. The numbers, diameter, and area fraction of neovascularization were quantitatively evaluated by Microfill perfusion, Micro-CT scanning, and vascular imaging under fluorescence at 4 and 8 weeks. The isolated cells were BMSCs and EPCs through identification. EPCs/BMSCs co-culture gradually formed tubular structure. The number of tubules and branches, and the total length of tubules formed in the EPCs/BMSCs group were significantly more than those in the EPCs group on Matrigel ( P<0.05) after 6 hours. After implanting and culturing in porous β-TCP scaffold for 7 days, EPCs formed cell membrane structure and attached to the material in EPCs group, and the cells attached more tightly, cell layers were thicker, the number of cells and the formation of tubular structures were significantly more in the EPCs/BMSCs group than in the EPCs group. At 4 weeks after implantation, neovascularization was observed in both groups. At 8 weeks, remodeling of neovascularization occurred in both groups. The number, diameter, and area fraction of neovascularization in the experimental group were higher than those in the control group ( P<0.05), except for area fraction at 4 weeks after implantation ( P>0.05). The prevascularized tissue engineered bone based on direct contact co-culture of BMSCs and EPCs can significantly promote the early vascularization process during bone defects repair.

Recent methods in fabricating porous β-tricalcium phosphate scaffolds: A mini review

This review aimed to focus on recent methods of fabricating porous beta-tricalcium phosphate (β-TCP) as a scaffold for clinical applications. These reviews summarized that the selection of methods for fabricating porous β-TCP scaffolds was greatly influenced by the cost, pores architecture, and microstructures of the fabricated scaffolds. The findings from reviewed papers show that highly porous β-TCP scaffolds with appropriate pore size, porosity and cost have been fabricated by various methods such as gel casting and foam replication method. However, some methods, such as gelatine-freeze casting and extrusion technique, were highly influenced the mechanical properties of porous β-TCP scaffolds with non-uniform pore sizes. Furthermore, additive manufacturing methods such as 3-D printing techniques could potentially achieve highly porous β-TCP scaffolds with appropriate pore size, porosity, and mechanical properties. As a result, it is expected that the information stated and tabulated in this mini-review will provide bioceramic researchers with new insights into recent methods for fabricating porous β-TCP scaffolds.

The effects of tubular structure on biomaterial aided bone regeneration in distraction osteogenesis

Long duration of bone consolidation in distraction osteogenesis (DO) has been regarded as a major disadvantage. Porous bone substitutes have been long used in aiding bone formation. However the effects of geometric tubular structure of the porous scaffolds on bone formation in DO remains unknown. This study investigated the effects of porous scaffolds with three different geometric structures on bone regeneration in a rabbit DO model. β-tricalcium phosphate (β-TCP) was fabricated into no tubular, single tubular, or multi-tubular structure constructs. The microstructure of the three types of β-TCP constructs was determined by scanning electron microscope (SEM). Unilateral tibial osteotomy was made at the midshaft with 1 cm tibial shaft removed, fixed with an external lengthener in adulkt New Zealand white rabbits. After acute tibial shortening of 0.5 cm, the remaining 0.5 cm defect was implanted with β-TCP constructs with no tubular, single tubular, or multi-tubular structure. Five days after surgery, the tibia was lengthened at 0.5 mm/12 h for 5 days. After further 28 days of consolidation, the animals were terminated. Bilateral tibial specimens were collected for X-ray, micro-computed tomography examination, four-point bending mechanical test and histological analysis. SEM results showed that pore sizes and pore interconnectivity in all three types of β-TCP constructs were identical. 38 days after surgery (4 weeks after lengthening), the new bone formation and mechanical properties were significantly enhanced in the groups implanted with multi-tubular and single tubular constructs, comparing to the group implanted with no tubular constructs. Furthermore, the group implanted with multi-tubular constructs had significantly better mechanical properties comparing to the group implanted with single tubular constructs. Histological results confirmed that group implanted with multi-tubular constructs had the most advanced bone formation and remodelling in the defect gap. The current study confirmed that β-TCP constructs with multi-tubular structure was the best choice as scaffold aid for bone regeneration in DO, indicating a novel fabrication approach of multi-tubular constructs for rapid bone formation together with DO procedure. Porous β-TCP scaffold with a multi-tubular structure used in combination with DO procedure can significantly shorten the bone consolidation duration. The tubular shaped porous β-TCP scaffold may be used to fill bone defect and to aid bone formation, consolidaiton and remodelling in DO.

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.

Engineering Porous β-Tricalcium Phosphate (β-TCP) Scaffolds with Multiple Channels to Promote Cell Migration, Proliferation, and Angiogenesis.

Inadequate oxygen and nutrient diffusion in a porous scaffold often resulted in insufficient formation of branched vasculatures, which hindered bone regeneration. In this study, interconnected porous β-tricalcium phosphate (β-TCP) scaffolds with different geometric designs of channels were fabricated and compared to discover the functionality of structure on facilitating nutrient diffusion for angiogenesis. In vitro fluid transportation and degradation of the scaffolds were performed. Cell infiltration, migration, and proliferation of human umbilical vein endothelial cells (HUVECs) on the scaffolds were carried out under both static and dynamic culture conditions. A computational simulation model and a series of immunofluorescent staining were implemented to understand the mechanism of cell behavior in response to different types of scaffolds. Results showed that geometry with multiple channels significantly accelerated the release of Ca2+ and increased the fluid diffusion efficiency. Moreover, multiple channels promoted HUVECs' infiltration and migration in vitro. The ex vivo implantation results showed that the channels promoted cells from the rats' calvarial bone explants to infiltrate into the implanted scaffold. Multiple channels also stimulated HUVECs' proliferation prominently at both static and dynamic culturing conditions. The expression of both cell migration-related protein α5 and angiogenesis-related protein CD31 on multiple-channeled scaffolds was upregulated compared to that on the other two types of scaffolds, implying that multiple channels reinforced cell migration and angiogenesis. All the findings suggested that the geometric design of multiple channels in the porous β-TCP scaffold has promising potential to promote cell infiltration, migration, and further vascularization when implanted in vivo.

Preclinical Studies of the Biosafety and Efficacy of Human Bone Marrow Mesenchymal Stem Cells Pre-Seeded into β-TCP Scaffolds after Transplantation.

Background: Cell-Based Therapies (CBT) constitute a valid procedure for increasing the quantity and quality of bone in areas with an inadequate bone volume. However, safety and efficacy should be investigated prior to clinical application. The objective of this study was to evaluate the biodistribution, safety and osteogenic capacity of bone marrow-derived human mesenchymal stem cells (hBMMSCs) pre-seeded into β-tricalcium phosphate (TCP) and implanted into NOD/SCID mice at subcutaneous and intramuscular sites. Methods: hBMMSCs were isolated, characterized and then cultured in vitro on a porous β-TCP scaffold. Cell viability and attachment were analyzed and then hBMMSCs seeded constructs were surgically placed at subcutaneous and intramuscular dorsal sites into NOD/SCID mice. Acute and subchronic toxicity, cell biodistribution and efficacy were investigated. Results: There were no deaths or adverse events in treated mice during the 48-hour observation period, and no toxic response was observed in mice. In the 12-week subchronic toxicity study, no mortalities, abnormal behavioral symptoms or clinical signs were observed in the saline control mice or the hBMMSCs/β-TCP groups. Finally, our results showed the bone-forming capacity of hBMMSCs/β-TCP since immunohistochemical expression of human osteocalcin was detected from week 7. Conclusions: These results show that transplantation of hBMMSCs/β-TCP in NOD/SCID mice are safe and effective, and might be applied to human bone diseases in future clinical trials.

Gel casting of β-TCP scaffolds: Effects of foaming time and polymer coating

Three-dimensional interconnected porous structure and ideal mechanical strength are essential for biological scaffold for bone tissue engineering application. However, ceramic scaffold is very brittle and exhibit low strength. The main aim of this study is to investigate the effect of foaming time on the microstructure and mechanical properties of porous beta tricalcium phosphate (β-TCP) scaffold. The effect of polymer coating on the β-TCP scaffold was also investigated. Porous β-TCP scaffolds were fabricated using the gel casting method by varying the foaming time (60s and 90s) followed by sintering at 1100°C. Porous β-TCP scaffold was coated with polymer coating by using dipping method. Results indicate that increased foaming time results in higher porosity and lower compression strength. It is observed that polymer coating improved around 116% compressive strength in comparison to that of uncoated scaffold. Fourier transform infrared (FTIR) confirm the presence of gelatin on scaffold walls. Based on the morphology observed by scanning electron microscope (SEM), it is found that the scaffold fabricated by gel casting method showed open pores characteristic.

Effect of Freezing Temperature on The Pore Formation of Beta Tricalcium Phosphate Scaffold

Beta-tricalcium phosphate (β-TCP) has been widely used for biomedical application due to its excellent mechanical strength, good tissue compatibility and outstanding chemical stability. There are several methods to fabricate porous scaffolds including solvent casting, phase separation, rapid prototyping and electrospinning methods. In the present study, β-TCP scaffolds were fabricated using freeze drying method. β-TCP slurry was frozen and freeze dried for 24 hours followed by sintering process to form β-TCP scaffolds. The porous β-TCP scaffold were fabricated at different percentages of β-TCP powder used (10 wt. %, 20 wt. % and 30 wt. %) and froze at different freezing temperature (-10°C, -20°C, -40°C and -80°C) in order to study the effect of these parameters on the pore formation of the scaffolds. Scanning electron microscopy (SEM) analysis for 30 wt. % β-TCP scaffold frozen at -10°C revealed acceptable pore size distribution with majority pore size within the range of 102.65 µm to 372.90 µm. Furthermore, this scaffold also possessed highest compressive strength of 0.31 MPa.

Techniques for fabrication and construction of three-dimensional bioceramic scaffolds: Effect on pores size, porosity and compressive strength

Three dimensional bioceramic scaffolds can be produced by several fabrication methods. Selecting the appropriate fabrication method requires a detailed investigation to produce scaffold with required properties. The present study aims to compare five different fabrication methods which are replication methods, combination of sacrificial template and direct foaming, freeze casting, gelate-freeze casting and salt leaching. Here, the discussion centers on comparison of these five fabrication methods, their respective advantages and disadvantages and parameters involve in the fabrication methods. Morphology and mechanical properties of the β-tricalcium phosphate (β-TCP) scaffold produced from these methods were compared and discussed. Highly porous β-TCP scaffolds with porosity of more than 50% and pore size of at least 100 µm have been fabricated using these methods. The compressive strength of the fabricated scaffolds is in the range of 0.05–2.0 MPa. It is observed that the properties of β-TCP scaffolds are influenced by the raw materials required by each of the processing, solid concentration and processing parameter. In conclusion, the gelate-freeze casting fabrication method with cellular structure shows the higher compressive strength and comparable pore size and porosity compared to other fabrication methods.

Effects of PCL, PEG and PLGA polymers on curcumin release from calcium phosphate matrix for in vitro and in vivo bone regeneration

Calcium phosphate materials are widely used as bone-like scaffolds or coating for metallic hip and knee implants due to their excellent biocompatibility, compositional similarity to natural bone and controllable bioresorbability. Local delivery of drugs or osteogenic factors from scaffolds and implants are required over a desired period of time for an effectual treatment of various musculoskeletal disorders. Curcumin, an antioxidant and anti-inflammatory molecule, enhances osteoblastic activity in addition to its anti-osteoclastic activity. However, due to its poor solubility and high intestinal liver metabolism, it showed limited oral efficacy in various preclinical and clinical studies. To enhance its bioavailability and to provide higher release, we have used poly (ε-caprolactone) (PCL), poly ethylene glycol (PEG) and poly lactide co glycolide (PLGA) as the polymeric system to enable continuous release of curcumin from the hydroxyapatite matrix for 22 days. Additionally, curcumin was incorporated in plasma sprayed hydroxyapatite coated Ti6Al4V substrate to study in vitro cell material interaction using human fetal osteoblast (hFOB) cells for load bearing implants. MTT cell viability assay and morphological characterization by FESEM showed highest cell viability with samples coated with curcumin-PCL-PEG. Finally, 3D printed interconnected macro porous β-TCP scaffolds were prepared and curcumin-PCL-PEG was loaded to assess the effects of curcumin on in vivo bone regeneration. The presence of curcumin in TCP results in enhanced bone formation after 6 weeks. Complete mineralized bone formation increased from 29.6% to 44.9% in curcumin-coated scaffolds compared to pure TCP. Results show that local release of curcumin can be designed for both load bearing or non-load bearing implants with the aid of polymers, which can be considered an excellent candidate for wound healing and tissue regeneration applications in bone tissue engineering.

Enhanced bone formation in the vicinity of porous β-TCP scaffolds exhibiting slow release of collagen-derived tripeptides.

It has been experimentally proven that orally ingested collagen-derived tripeptides (Ctp) are quickly absorbed in the body and effectively promote the regeneration of connective tissues including bone and skin. Ctp are capable to activate osteoblasts and fibroblasts, which eventually promotes tissue regeneration. Based on these findings, a hypothesis was formulated in this study that direct delivery of Ctp to bone defect would also facilitate tissue regeneration as well as oral administration. To test the hypothesis, we prepared a bone augmentation material with the ability to slowly release Ctp, and investigated its in vivo bone regeneration efficacy. The implant material was porous β-tricalcium phosphate (β-TCP) scaffold which was coated with a co-precipitated layer of bone-like hydroxyapatite and Ctp. The β-TCP was impregnated with approximately 0.8%(w/w) Ctp. Then, the Ctp-modified β-TCP was implanted into bone defects of Wistar rats to evaluate in vivo efficacy of Ctp directly delivered from the material to the bone defects. The control was pristine porous β-TCP. In vitro tests showed that Ctp were steadily released from the co-precipitated layer for approximately two weeks. The Ctp-modified scaffolds significantly promoted new bone formation in vivo in their vicinity as compared with pristine β-TCP scaffolds; 6 weeks after the implantation, Ctp-modified scaffolds promoted twice as much bone formation as the control implants. Consequently, we achieved the slow and steady release of Ctp, and found that direct delivery of Ctp from implant materials was effective for bone regeneration as well as oral administration. A β-TCP scaffold capable of slowly releasing bone-enhancing substances significantly promoted bone formation.

Engineering biomimetic periosteum with \u03b2-TCP scaffolds to promote bone formation in calvarial defects of rats

BackgroundThere is a critical need for the management of large bone defects. The purpose of this study was to engineer a biomimetic periosteum and to combine this with a macroporous β-tricalcium phosphate (β-TCP) scaffold for bone tissue regeneration.MethodsRat bone marrow-derived mesenchymal stem cells (rBMSCs) were harvested and cultured in different culture media to form undifferentiated rBMSC sheets (undifferentiated medium (UM)) and osteogenic cell sheets (osteogenic medium (OM)). Simultaneously, rBMSCs were differentiated to induced endothelial-like cells (iECs), and the iECs were further cultured on a UM to form a vascularized cell sheet. At the same time, flow cytometry was used to detect the conversion rates of rBMSCs to iECs. The pre-vascularized cell sheet (iECs/UM) and the osteogenic cell sheet (OM) were stacked together to form a biomimetic periosteum with two distinct layers, which mimicked the fibrous layer and cambium layer of native periosteum. The biomimetic periostea were wrapped onto porous β-TCP scaffolds (BP/β-TCP) and implanted in the calvarial bone defects of rats. As controls, autologous periostea with β-TCP (AP/β-TCP) and β-TCP alone were implanted in the calvarial defects of rats, with a no implantation group as another control. At 2, 4, and 8 weeks post-surgery, implants were retrieved and X-ray, microcomputed tomography (micro-CT), histology, and immunohistochemistry staining analyses were performed.ResultsFlow cytometry results showed that rBMSCs were partially differentiated into iECs with a 35.1% conversion rate in terms of CD31. There were still 20.97% rBMSCs expressing CD90. Scanning electron microscopy (SEM) results indicated that cells from the wrapped cell sheet on the β-TCP scaffold apparently migrated into the pores of the β-TCP scaffold. The histology and immunohistochemistry staining results from in vivo implantation indicated that the BP/β-TCP and AP/β-TCP groups promoted the formation of blood vessels and new bone tissues in the bone defects more than the other two control groups. In addition, micro-CT showed that more new bone tissue formed in the BP/β-TCP and AP/β-TCP groups than the other groups.ConclusionsInducing rBMSCs to iECs could be a good strategy to obtain an endothelial cell source for prevascularization. Our findings indicate that the biomimetic periosteum with porous β-TCP scaffold has a similar ability to promote osteogenesis and angiogenesis in vivo compared to the autologous periosteum. This function could result from the double layers of biomimetic periosteum. The prevascularized cell sheet served a mimetic fibrous layer and the osteogenic cell sheet served a cambium layer of native periosteum. The biomimetic periosteum with a porous ceramic scaffold provides a new promising method for bone healing.

Poly(trimethylene carbonate)-based composite materials for reconstruction of critical-sized cranial bone defects in sheep

PurposeThe use of ceramic materials in repair of bone defects is limited to non-load-bearing sites. We tested poly(trimethylene carbonate) (PTMC) combined with β-tricalcium phosphate or biphasic calcium phosphate particles for reconstruction of cranial defects. Materials and methodsPTMC-calcium phosphate composite matrices were implanted in cranial defects in sheep for 3 and 9 months. Micro-computed tomography quantification and histological observation were performed for analysis. ResultsNo differences were found in new bone formation among the defects left unfilled, filled with PTMC scaffolds, or filled with either kind of PTMC-calcium phosphate composite scaffolds. Porous β-TCP scaffolds as control led to a larger amount of newly formed bone in the defects than all other materials. Histology revealed abundant new bone formation in the defects filled with porous β-TCP scaffolds. New bone formation was limited in defects filled with PTMC scaffolds or different PTMC-calcium phosphate matrices. PTMC matrices were degraded uneventfully. New bone formation within the defects followed an orderly pattern. ConclusionsPTMC did not interfere with bone regeneration in sheep cranial defects and is suitable as a polymer matrix for incorporating calcium phosphate particles. Increasing the content of calcium phosphate particles in the composite matrices may enhance the beneficial effects of the particles on new bone formation.