Using calcium silicate to regulate the physicochemical and biological properties when using β-tricalcium phosphate as bone cement

Bone regeneration using Wollastonite/β-TCP scaffolds implants in critical bone defect in rat calvaria

In order to provide favorable conditions for bone regeneration, a lot of biomaterials have been developed and evaluated, worldwide. Composite biomaterials have gained notoriety, as they combine desirable properties of each isolated material. Thus, in this research, bone repair capacity of three developed formulations of ceramic scaffolds were evaluated histomorphometrically, after implantation. Scaffolds were based on wollastonite (W) andβ-tricalcium phosphate (β-TCP) composites in three different ratios (wt.%). ThirtyWistarrats were randomly assigned to three experimental groups: W-20 (20 W/80β-TCP wt.%), W-60 (60 W/40β-TCP wt.%), and W-80 (80 W/20β-TCP wt.%), evaluated by optical microscopy at biological tests after 15 and 45 days of implantation. Throughout the study, the histological results evidenced that the scaffolds remained at the implantation site, were biocompatible and presented osteogenic potential. The percentage of neoformed mineralized tissue was more evident in the W-20 group (51%), at 45 days. The composite of the W-80 group showed more evident biodegradation than the biomaterials of the W-20 and W-60 groups. Thus, it is concluded that the scaffold containing 20 W/80β-TCP (wt.%) promoted more evident bone formation, but all composites evaluated in this study showed notorious bioactivity and promising characteristics for clinical application.

Mechanical assessment and odontogenic behavior of a 3D-printed mesoporous calcium silicate/calcium sulfate/poly-ε-caprolactone composite scaffold

BACKGROUND/PURPOSE

Tissue engineering in dentistry has fundamentally changed the way endodontists assess treatment options. Our previous study found that quercetin-contained mesoporous calcium silicate/calcium sulfate (MSCSQ) could induce hard tissue defect region regeneration. This study focused on whether the MSCSQ scaffold could also be effective in regulating odontogenesis and dentin regeneration.

METHODS

In this study, we fabricated MSCSQ composite scaffolds using the 3D printing technique. The characteristics of the MSCSQ scaffold were examined by scanning electron microscope (SEM), and mechanical properties were also assessed. In addition, we evaluated the cell viability, cell proliferation, odontogenic-related protein expression, and mineralization behavior of human dental pulp stem cells (hDPSCs) cultured on different scaffolds.

RESULTS

We found the precipitation of spherical-apatite on the scaffold surface rapidly in short periods. The in-vitro results for cell behavior revealed that hDPSCs with an MSCSQ scaffold were significantly higher in cell viability as followed time points. In addition, the specific makers of odontogenesis, such as DSPP and DMP-1 proteins, were induced obviously after culturing the hDPSCs on the MSCSQ scaffold.

CONCLUSION

Our results demonstrated that MSCSQ scaffolds could enhance physicochemical and biological behaviors compared to mesoporous calcium silicate/calcium sulfate (MSCS) scaffolds. In addition, MSCSQ scaffolds also enhanced odontogenic and immuno-suppressive properties compared to MSCS scaffolds. These results indicated that MSCSQ scaffolds could be considered a potential bioscaffold for clinical applications and dentin regeneration.

Biocompatibility of a HA/β-TCP/C Scaffold as a Pulp-Capping Agent for Vital Pulp Treatment: An In Vivo Study in Rat Molars

Bioceramic materials possess desirable biological properties, highlighting their non-reactivity and osteoconductivity. Their use has been extended in vital pulp treatment. The purpose of this study was to evaluate and compare the effects of beta-tricalcium phosphate (β-TCP), hydroxyapatite (HA), and collagen (C) scaffold with mineral trioxide aggregate (MTA) on the vital pulp of rat molars. Thirty-two molars of Sprague–Dawley rats underwent direct pulp capping with β-TCP/HA/C (n = 16) and MTA (n = 16). After 30 days, the following parameters were evaluated in the tested samples: the degree of pulp inflammation and pulp vitality, the presence of reparative dentin, the homogeneity of the odontoblastic layer, and the presence of pulp fibrosis. No statistically significant differences were observed between HA/β-TCP/C and MTA in terms of the degree of inflammation (p = 0.124). Significant differences were found in reparative dentin formation between the treatment groups (p = 0.0005). Dentin bridge formation was observed in the MTA-treated group. The local action of HA/β-TCP/C is similar to that of MTA when used as an agent for pulp vital treatment in terms of absence of inflammation and maintenance of pulp vitality, although there are significant differences between both materials regarding the formation of dentin bridges.

Biphasic ceramic biomaterials with tunable spatiotemporal evolution for highly efficient alveolar bone repair

Alveolar bone defects, which are characterized by a relatively narrow space and location adjacent to the cementum, require promising substitute biomaterials for their regeneration. In this study, we introduced novel yolk-shell biphasic bio-ceramic granules with/without a customized porous shell and evaluated their biological effect together with structural transformation. Firstly, a self-made coaxial bilayer capillary system was applied for the fabrication of granules. Secondly, thorough morphological and physicochemical characterizations were performed in vitro. Subsequently, the granules were implanted into critical-size alveolar bone defects (10 × 4 × 3 mm) in New Zealand white rabbits, with Bio-Oss® as the positive control. Finally, at 2, 4, 8, and 16 weeks postoperatively, the alveolar bone specimens were harvested and assessed via radiological and histological examination. Our results showed that the yolk-shell biphasic bio-ceramic granules, especially those with porous shells, exhibited a tunable ion release performance, improved biodegradation behavior and satisfactory osteogenesis compared with the homogeneously hybrid and Bio-Oss® granules both in vitro and in vivo. This study provides the first evidence that novel yolk-shell bio-ceramic granules, on account of their adjustable porous microstructure, have great potential in alveolar bone repair.

Effect of Bone Morphogenic Protein-2-Loaded Mesoporous Strontium Substitution Calcium Silicate/Recycled Fish Gelatin 3D Cell-Laden Scaffold for Bone Tissue Engineering

Bone has a complex hierarchical structure with the capability of self-regeneration. In the case of critical-sized defects, the regeneration capabilities of normal bones are severely impaired, thus causing non-union healing of bones. Therefore, bone tissue engineering has since emerged to solve problems relating to critical-sized bone defects. Amongst the many biomaterials available on the market, calcium silicate-based (CS) cements have garnered huge interest due to their versatility and good bioactivity. In the recent decade, scientists have attempted to modify or functionalize CS cement in order to enhance the bioactivity of CS. Reports have been made that the addition of mesoporous nanoparticles onto scaffolds could enhance the bone regenerative capabilities of scaffolds. For this study, the main objective was to reuse gelatin from fish wastes and use it to combine with bone morphogenetic protein (BMP)-2 and Sr-doped CS scaffolds to create a novel BMP-2-loaded, hydrogel-based mesoporous SrCS scaffold (FGSrB) and to evaluate for its composition and mechanical strength. From this study, it was shown that such a novel scaffold could be fabricated without affecting the structural properties of FGSr. In addition, it was proven that FGSrB could be used for drug delivery to allow stable localized drug release. Such modifications were found to enhance cellular proliferation, thus leading to enhanced secretion of alkaline phosphatase and calcium. The above results showed that such a modification could be used as a potential alternative for future bone tissue engineering research.

Development of mussel-inspired 3D-printed poly (lactic acid) scaffold grafted with bone morphogenetic protein-2 for stimulating osteogenesis

3D printing is a versatile technique widely applied in tissue engineering due to its ability to manufacture large quantities of scaffolds or constructs with various desired architectures. In this study, we demonstrated that poly (lactic acid) (PLA) scaffolds fabricated via fused deposition not only retained the original interconnected microporous architectures, the scaffolds also exhibited lower lactic acid dissolution as compared to the freeze-PLA scaffold. The 3D-printed scaffolds were then grafted with human bone morphogenetic protein-2 (BMP-2) via the actions of polydopamine (PDA) coatings. The loading and release rate of BMP-2 were monitored for a period of 35 days. Cellular behaviors and osteogenic activities of co-cultured human mesenchymal stem cells (hMSCs) were assessed to determine for efficacies of scaffolds. In addition, we demonstrated that our fabricated scaffolds were homogenously coated with PDA and well grafted with BMP-2 (219.1 ± 20.4 ng) when treated with 250 ng/mL of BMP-2 and 741.4 ± 127.3 ng when treated with 1000 ng/mL of BMP-2. This grafting enables BMP-2 to be released in a sustained profile. From the osteogenic assay, it was shown that the ALP activity and osteocalcin of hMSCs cultured on BMP-2/PDA/PLA were significantly higher when compared with PLA and PDA/PLA scaffolds. The methodology of PDA coating employed in this study can be used as a simple model to immobilize multiple growth factors onto different 3D-printed scaffold substrates. Therefore, there is potential for generation of scaffolds with different unique modifications with different capabilities in regulating physiochemical and biological properties for future applications in bone tissue engineering.

Substitutions of strontium in bioactive calcium silicate bone cements stimulate osteogenic differentiation in human mesenchymal stem cells

Calcium silicate cements have been considered as alternative bone substitutes owing to its extraordinary bioactivity and osteogenicity. Unfortunately, the major disadvantage of the cements was the slow degradation rate which may limit the efficiency of bone regeneration. In this study, we proposed a facile method to synthesize degradable calcium silicate cements by incorporating strontium into the cements through solid-state sintering. The effects of Sr incorporation on physicochemical and biological properties of the cements were evaluated. Although, our findings revealed that the incorporation of strontium retarded the hardening reaction of the cements, the setting time of different cements (11-19 min) were in the acceptable range for clinical use. The presence of Sr in the CS cements would hampered the precipitation of calcium phosphate products on the surface after immersion in SBF, however, a layer of precipitated calcium phosphate products can be formed on the surface of the Sr-CS cement within 1 day immersion in SBF. More importantly, the degradation rate of the cements increased with increasing content of strontium, consequentially raised the levels of released strontium and silicon ions. The elevated dissolving products may contribute to the enhancement of the cytocompatibility, alkaline phosphatase activity, osteocalcin secretion, and mineralization of human Wharton's jelly mesenchymal stem cells. Together, it is concluded that the strontium-incorporated calcium silicate cement might be a promising bone substitute that could accelerate the regeneration of irregularly shaped bone defects.

Poly (Methyl Methacrylate)/Biphasic Calcium Phosphate/Nano Graphene Bone Cement for Orthopedic Application

Background:

The aim of this study was to make a bioactive bone cement based on poly (methyl methacrylate) (PMMA) with suitable mechanical properties.

Methods:

PMMA has been modified by fabricating a composite consisting of biphasic calcium phosphate (BCP) 68 wt%, PMMA 31 wt% and graphene (Gr) 1 wt% (PMMA/BCP/Gr), 32 wt% of PMMA, and 68 wt% of BCP (PMMA/BCP) and pure PMMA by milling, mixing with monomer liquid, and casting. The modified cements were evaluated regarding mechanical properties, bioactivity, degradation rate, and biocompatibility.

Results:

The scanning electron microscopy (SEM) images of hydroxyapatite (HA) formed on samples surface after 28 days of immersion in simulated body fluid (SBF) demonstrated that bioactivity was obtained due to the addition of BCP, and the degradation rate of the cement was enhanced as well. Investigations of mechanical properties revealed that BCP increased the elastic modulus of PMMA more than 1.5 times, but predictably decreased elongation. The addition of 1 wt% Gr increased elongation and yield strength from 16.39% ± 1.02% and 61.67 ± 1.52 Mpa for PMMA/BCP to 35.18% ± 2.42% and 78.40 ± 2.06 Mpa for PMMA/BCP/Gr, respectively. MG63 cells survival and proliferation improved from 127.55% ± 7.03% for PMMA to 201.41% ± 10.7% for PMMA/BCP/Gr on Day 4 of culture.

Conclusion:

According to the obtained results of mechanical and biological tests, it seems that new PMMA/BCP/Gr bone cement has a potentiality for usage in orthopedic applications.

Effects of a New Bioceramic Material on Human Apical Papilla Cells

BACKGROUND

The development of materials with bioregenerative properties is critically important for vital pulp therapies and regenerative endodontic procedures. The aim of this study was to evaluate the cytocompatibility and cytotoxicity of a new endodontic biomaterial, PulpGuard, in comparison with two other biomaterials widely used in endodontic procedures, ProRoot Mineral Trioxide Aggregate (MTA) and Biodentine.

METHODS

Apical papilla cells (APCs) were isolated from third molars with incomplete rhizogenesis from patients with orthodontic indication for dental extraction. Cultured APCs were incubated for 24, 48, or 72 h with different dilutions of eluates prepared from the three materials. Cellular viability, mobility, and proliferation were assessed in vitro using the Alamar Blue assay and a wound-healing test. The cells were also cultured in direct contact with the surface of each material. These were then analyzed via Scanning Electron Microscopy (SEM), and the surface chemical composition was determined by Energy-Dispersive Spectroscopy (EDS).

RESULTS

Cells incubated in the presence of eluates extracted from ProRoot MTA and PulpGuard presented rates of viability comparable to those of control cells; in contrast, undiluted Biodentine eluates induced a significant reduction of cellular viability. The wound-healing assay revealed that eluates from ProRoot MTA and PulpGuard allowed for unhindered cellular migration and proliferation. Cellular adhesion was observed on the surface of all materials tested. Consistent with their disclosed composition, EDS analysis found high relative abundance of calcium in Biodentine and ProRoot MTA and high abundance of silicon in PulpGuard. Significant amounts of zinc and calcium were also present in PulpGuard discs. Concerning solubility, Biodentine and ProRoot MTA presented mild weight loss after eluate extraction, while PulpGuard discs showed significant water uptake.

CONCLUSIONS

PulpGuard displayed a good in vitro cytocompatibility profile and did not significantly affect the proliferation and migration rates of APCs. Cells cultured in the presence of PulpGuard eluates displayed a similar profile to those cultured with eluates from the widely used endodontic cement ProRoot MTA.

Enhancing the biological activity of vaterite-containing β-dicalcium silicate cement by silane coupling agent for biomaterials

Vaterite-containing β-dicalcium silicate powder (A-V-C₂S) was successfully grafting modified by 3-aminopropyltriethoxysilane (APTES) through reflux agitation. The purpose of this work is to fix the amino groups on the vaterite-containing β-dicalcium silicate (V-C₂S) powder's surface, which makes the powder's surface with positive charge, and further enhanced the combination with those negatively charged bioactive molecules or drugs to improve the performance of biomaterials. XRD and FT-IR analysis indicated that N-H groups were successfully grafted onto the surface of the V-C₂S sample on the basis of vaterite existence through the process of first grafting then carbonation. Moreover, the best grafting modification that refluxing at 70 °C for 12 h was determined through the quantitative analysis of N-H groups on V-C₂S powder's surface. The A-V-C₂S sample showed a better apatite formation ability after it was soaked in stimulated body fluid (SBF), indicating that good apatite mineralization. Moreover, the A-V-C₂S sample with weak alkali in implanting position could stimulate the attachment, proliferation and improve the activity of MC3T3-E1 cells. Experimental results demonstrated that, A-V-C₂S was expected to be a new biomaterial as bone repairing substitute.

Silicocarnotite Synthesis and Bioactivity in Artificial Saliva Medium

The aim of this study is the synthesis and investigation of bioactive response of acrystalline silicophosphate.A monophasic silicocarnotite was elaborated by solid state reaction from a mixture of beta-tricaliciumphosphate and dicalcium silicate based on mussel shells according to the diagram of system Ca3(PO4)2–Ca2SiO4, at 65 % and 35% respectively , these starting materials are heated up to 1450 °C to obtain a monophasic silicocaronitite. The obtained result probed that the main crystalline phase which was detected and recognized in the heated sample at 1400 and 1450 °C was a well-crystallized silicocarnotite. The test of bioactivity of silicocarnotite in artificial saliva causes the appearance of a reaction layer on the materials surface after 4 hours soaking and growth up during 30 days.This layer is constituted of a biphasic mixture of Si–Ca–P–H material, silicated hydroxyapatite and hydroxyapatite phase are the mainly developing ones with increasing soaking time.The analysis and characterization of the precipitated appearing on the material surface has confirmed experimentally the in vitro bioactivity of silicocarnotite monophasic material.

[Efficacy of inactivated autologous porous bone flap and BAM bone-induced artificial bone for repairing skull defect in rats]

OBJECTIVE

To study the effect of BAM bone grafting combined with inactivated autologous porous bone flap in repairing skull defect in rats.

METHODS

Seventy-two Wistar rats with skull defect were randomly divided into control group, inactivated autologous bone flap group (AB group), BAM bone-induced artificial bone material group (BAM group), and inactivated autologous bone flap with BAM bone-induced artificial bone group (BAM+AB group). The bone healing was evaluated with micro-CT and the new bone formation was assessed with histological staining at 1, 2, and 3 months after modeling.

RESULTS

Inactivated porous bone flap combined with BAM bone-induced artificial bone effectively induced vascular and fibrous tissue regeneration and osteogenesis in the cranial defects. With the inactivated porous bone flap as the scaffold, BAM bone-induced artificial bone obviously promoted the restoration of the skull appearance in the rats with cranial defects.

CONCLUSION

Inactivated autologous bone flap group and BAM bone-induced artificial bone material can promote skull healing and restoration of the original skull appearance, and can be used for reconstruction of the local anatomy of the skull surface.

β-Dicalcium Silicate Cement Modified with β-Tricalcium Phosphate: In Vitro Bioactivity and Mechanical Strength

Calcium-silicate cement mainly based on dicalcium-silicate (C2S) was synthesized by the mean of solid state reaction. Beta-C3P was added to C2S to obtain C2S-C3P. Zinc oxide and bismuth oxide was incorporated to prepare radioc cement. In this work, the bioactivity and the mechanical strength of the synthesized cement were investigated. The in vitro test was carried out by immersion of cement pastilles in the artificial saliva in different periods from 4 hours to 30 days. Whereas the mechanical strength of some samples was operated at 28 and 72 days. The specimens are characterized by X-ray diffraction , Infrared spectroscopy and scanning electron microscopy. The finding results indicated that hydroxyapatite may appear after 24 hours of soaking; it was also shown that the presence of C3P with a small amount of the cement can enhance the bioactivity and develop more resistance strength of cement. Moreover, the addition of zinc oxide and bismuth oxide increase the radiopacity of the cement. However, the mechanical strength enhances with the incorporation of the zinc oxide while decrease with bismuth oxide. It was concluded then that there is possibility of combining addition of C3P (10%) and an agent radiopacifiers ZnO/Bi2O3(15%) with small amounts on C2S to obtain a cement with excellent bioactivity, good mechanical strength and significante radiopacity that makes this material a great candidate as a biomaterial for biomedical use.

Novel vaterite-containing tricalcium silicate bone cement by surface functionalization using 3-aminopropyltriethoxysilane: setting behavior, in vitro bioactivity and cytocompatibility

A novel vaterite-containing tricalcium silicate (V-C₃S) was grafted by 3-aminopropyltriethoxysilane (APTES), and the amino groups have been successfully fixed on the vaterite-containing tricalcium silicate powder's surface (after grafting the amino group, V-C₃S was named A-V-C₃S). The setting behavior, mechanical properties, porosity, weight loss and anti-washout properties of the tricalcium silicate (C₃S), V-C₃S and A-V-C₃S bone cement were systematically investigated. The in vitro induction of hydroxyapatite (HAp) formation of C₃S, V-C₃S and A-V-C₃S bone cement was confirmed by x-ray diffraction, Fourier-transform infrared spectroscopy and scanning electron microscopy. The cell viability, cell proliferation and cell attachment were investigated to assess the effects of bone cement on MC3T3-E1 cells. Results showed that the setting time of A-V-C₃S bone cement can meet the requirements of a clinical test, with improved anti-washout properties and an appropriate degradation rate. The pH value of the soaking solution was obviously decreased by surface modification. Besides, the morphology and fluorescence photograph results revealed that the A-V-C₃S bone cement showed an enhanced biocompatibility effect on the proliferation and attachment of MC3T3-E1 cells. The A-V-C₃S bone cement was expected to be a potential bone-substitute material.

3D printed scaffolds of calcium silicate-doped β-TCP synergize with co-cultured endothelial and stromal cells to promote vascularization and bone formation

Synthetic bone scaffolds have potential application in repairing large bone defects, however, inefficient vascularization after implantation remains the major issue of graft failure. Herein, porous β-tricalcium phosphate (β-TCP) scaffolds with calcium silicate (CS) were 3D printed, and pre-seeded with co-cultured human umbilical cord vein endothelial cells (HUVECs) and human bone marrow stromal cells (hBMSCs) to construct tissue engineering scaffolds with accelerated vascularization and better bone formation. Results showed that in vitro β-TCP scaffolds doped with 5% CS (5%CS/β-TCP) were biocompatible, and stimulated angiogenesis and osteogenesis. The results also showed that 5%CS/β-TCP scaffolds not only stimulated co-cultured cells angiogenesis on Matrigel, but also stimulated co-cultured cells to form microcapillary-like structures on scaffolds, and promoted migration of BMSCs by stimulating co-cultured cells to secrete PDGF-BB and CXCL12 into the surrounding environment. Moreover, 5%CS/β-TCP scaffolds enhanced vascularization and osteoinduction in comparison with β-TCP, and synergized with co-cultured cells to further increase early vessel formation, which was accompanied by earlier and better ectopic bone formation when implanted subcutaneously in nude mice. Thus, our findings suggest that porous 5%CS/β-TCP scaffolds seeded with co-cultured cells provide new strategy for accelerating tissue engineering scaffolds vascularization and osteogenesis, and show potential as treatment for large bone defects.

Effect of sintering temperature rise from 870 to 920°C on physicomechanical and biological quality of nano-hydroxyapatite: An explorative multi-phase experimental in vitro/vivo study

Hydroxyapatite (HA) is a proper scaffold for bone repair, however, it is not of excellent mechanical properties. Most previous studies on the effect of temperature increases were in vitro and had assessed merely improvements of HA's physicomechanical quality. This in vitro/vivo study investigated the effect of temperature increases from 870 to 920°C on physicomechanical and biological quality of Nano-HA. Forty experimentally produced HA disks sintered at 870 to 920°C were prepared (n=20×2). Disks were subjected to Vickers microindentation test (1 disk from each group divided into 4 quarters), Fourier transform infrared spectroscopy (1 disk), X-ray diffraction (XRD) [1 disk together with non-sintered HA], field emission scanning electron microscopy (FSEM, 1 disk from each group together with non-sintered HA), cell seeding and SEM assessment (2 disks), MTT assay over 4 different time periods (16 quadrants of 4 disks from each group), 6 one-thirds of 2 disks from each group for immunocytochemical (ICC) assay, and 8 disks from each group [as well as non-sintered HA] for the animal study (implantation in 4 sockets in 8 rabbits [32 specimens], histomorphometry, and computerized tomography) over two time periods. Quantitative data were analyzed statistically (α=0.05). Vickers microhardness increased from 63.7±11.9 in the 870 group to 153.4±104.7 in the 920 group (P=0.057). XRD indicated more regular crystal patterns in sintered groups compared to non-sintered nanoHA. FSEM showed larger crystals in the 920 group compared to 870 and non-sintered nanoHA. Expression of osteocalcin, osteonectin, and RUNX2 genes were more visible in ICC samples of the 920HA group. In MTT, cell numbers increased in all groups significantly (P=0.000), with no between-group differences (P>0.3). In rabbit experiments, the extent of 'newly formed bone' increased significantly over time (two-way ANOVA, P=0.000), reaching 39.5%, 46.4%, and 77.5% in the groups non-sintered HA, 870, and 920, respectively. The 920°C-sintered nanoHA induced the highest bone formation (P=0.000). Increasing the temperature of nanoHA sintering from 870 to 920°C can improve its physicomechanical properties and bone formation potential.

Laser Sintered Magnesium-Calcium Silicate/Poly-ε-Caprolactone Scaffold for Bone Tissue Engineering

In this study, we manufacture and analyze bioactive magnesium-calcium silicate/poly-ε-caprolactone (Mg-CS/PCL) 3D scaffolds for bone tissue engineering. Mg-CS powder was incorporated into PCL, and we fabricated the 3D scaffolds using laser sintering technology. These scaffolds had high porosity and interconnected-design macropores and structures. As compared to pure PCL scaffolds without an Mg-CS powder, the hydrophilic properties and degradation rate are also improved. For scaffolds with more than 20% Mg-CS content, the specimens become completely covered by a dense bone-like apatite layer after soaking in simulated body fluid for 1 day. In vitro analyses were directed using human mesenchymal stem cells (hMSCs) on all scaffolds that were shown to be biocompatible and supported cell adhesion and proliferation. Increased focal adhesion kinase and promoted cell adhesion behavior were observed after an increase in Mg-CS content. In addition, the results indicate that the Mg-CS quantity in the composite is higher than 10%, and the quantity of cells and osteogenesis-related protein of hMSCs is stimulated by the Si ions released from the Mg-CS/PCL scaffolds when compared to PCL scaffolds. Our results proved that 3D Mg-CS/PCL scaffolds with such a specific ionic release and good degradability possessed the ability to promote osteogenetic differentiation of hMSCs, indicating that they might be promising biomaterials with potential for next-generation bone tissue engineering scaffolds.

Fabrication and characterization of polycaprolactone and tricalcium phosphate composites for tissue engineering applications

Background/purpose

β-Tricalcium phosphate (β-TCP) is an osteoconductive material which has been used for clinical purposes for several years, as is polycaprolactone (PCL), which has already been approved for a number of medical and drug delivery devices. In this study we have incorporated various concentrations of β-TCP into PCL with the aim of developing an injectable, mechanically strong, and biodegradable material which can be used for medical purposes without organic solvents.

Materials and methods

This study assesses the physical and chemical properties of this material, evaluates the in vitro bioactivity of the PCL/β-TCP composites, and analyzes cell proliferation and osteogenic differentiation when using human bone marrow mesenchymal stem cells (hBMSCs).

Results

The results show that weight losses of approximately 5.3%, 12.1%, 18.6%, and 25.2%, were observed for the TCP0, TCP10, TCP30, and TCP50 composites after immersion in simulated body fluid for 12 weeks, respectively, indicating significant differences (P < 0.05). In addition, PCL/β-TCP composites tend to have lower contact angles (47 ± 1.5° and 58 ± 1.7° for TCP50 and TCP30, respectively) than pure PCL (85 ± 1.3°), which are generally more hydrophilic. After 7 days, a significant (22% and 34%, respectively) increase (P < 0.05) in alkaline phosphatase level was measured for TCP30 and TCP50 in comparison with the pure PCL.

Conclusion

PCL/TCP is biocompatible with hBMSCs. It not only promotes proliferation of hBMSCs but also helps to differentiate reparative hard tissue. We suggest 50% (weight) PCL-containing β-TCP biocomposites as the best choice for hard tissue repair applications.

Efficacy of the biomaterials 3wt%-nanostrontium-hydroxyapatite-enhanced calcium phosphate cement (nanoSr-CPC) and nanoSr-CPC-incorporated simvastatin-loaded poly(lactic-co-glycolic-acid) microspheres in osteogenesis improvement: An explorative multi-phase experimental in vitro/vivo study

AIMS

The purpose of this multi-phase explorative in vivo animal/surgical and in vitro multi-test experimental study was to (1) create a 3wt%-nanostrontium hydroxyapatite-enhanced calcium phosphate cement (Sr-HA/CPC) for increasing bone formation and (2) creating a simvastatin-loaded poly(lactic-co-glycolic acid) (SIM-loaded PLGA) microspheres plus CPC composite (SIM-loaded PLGA+nanostrontium-CPC). The third goal was the extensive assessment of multiple in vitro and in vivo characteristics of the above experimental explorative products in vitro and in vivo (animal and surgical studies).

METHODS AND RESULTS PERTAINING TO SR-HA/CPC

Physical and chemical properties of the prepared Sr-HA/CPC were evaluated. MTT assay and alkaline phosphatase activities, and radiological and histological examinations of Sr-HA/CPC, CPC and negative control were compared. X-ray diffraction (XRD) indicated that crystallinity of the prepared cement increased by increasing the powder-to-liquid ratio. Incorporation of Sr-HA into CPC increased MTT assay (biocompatibility) and ALP activity (P<0.05). Histomorphometry showed greater bone formation after 4weeks, after implantation of Sr-HA/CPC in 10 rats compared to implantations of CPC or empty defects in the same rats (n=30, ANOVA P<0.05). METHODS AND RESULTS PERTAINING TO SIM-LOADED PLGA MICROSPHERES+NANOSTRONTIUM-CPC COMPOSITE: After SEM assessment, the produced composite of microspheres and enhanced CPC were implanted for 8weeks in 10 rabbits, along with positive and negative controls, enhanced CPC, and enhanced CPC plus SIM (n=50). In the control group, only a small amount of bone had been regenerated (localized at the boundary of the defect); whereas, other groups showed new bone formation within and around the materials. A significant difference was found in the osteogenesis induced by the groups sham control (16.96±1.01), bone materials (32.28±4.03), nanostrontium-CPC (24.84±2.6), nanostrontium-CPC-simvastatin (40.12±3.29), and SIM-loaded PLGA+nanostrontium-CPC (44.8±6.45) (ANOVA P<0.001). All the pairwise comparisons were significant (Tukey P<0.01), except that of nanostrontium-CPC-simvastatin and SIM-loaded PLGA+nanostrontium-CPC. This confirmed the efficacy of the SIM-loaded PLGA+nanostrontium-CPC composite, and its superiority over all materials except SIM-containing nanostrontium-CPC.

Substantial enhancement of corrosion resistance and bioactivity of magnesium by incorporating calcium silicate particles

We discovered that calcium silicate is an effective reinforcement phase to improve the corrosion resistance, mechanical strength and biological performance of Mg or Mg-based alloys to overcome their major drawbacks for orthopedic implant applications.

Macrophage-mediated osteogenesis activation in co-culture with osteoblast on calcium silicate cement

The use of calcium silicate (CS) cement holds great promise for bone substitute biomaterials. However, the effects of CS on osteoblast and macrophage cells are not fully understood. This study examines cell proliferation and differentiation of mono- or co-cultured MC3T3-E1 and Raw 264.7 cells on CS cement. Very few studies to date have looked at the effects of osteoblast and macrophages on biomaterial-regulated osteogenesis. In this study the proliferation and differentiation of MC3T3-E1, Raw 264.7 and co-cultured MC3T3-E1/Raw 264.7 on CS cements have been analyzed using a PrestoBlue kit and ELISA. In addition, the effect of macrophages on CS-coordinated osteogenesis of MC3T3-E1 has been investigated. Results show that MC3T3-E1, Raw 264.7 and co-cultured MC3T3-E1/Raw 264.7 adhere to and proliferate well on the CS cement. In a co-culture, the CS cements inhibit receptor activator of nuclear factor kappa B ligand expression of both genes and proteins in Raw 264.7 cells when compared to those grown in mono-cultured system. Ca deposition of MC3T3-E1 in the co-culture is higher than that of cells in a mono-culture. Bone morphogenetic protein 2 (BMP2) is also significantly up-regulated by the CS cement stimulation, indicating that macrophages may participate in the CS stimulated osteogenesis. Interestingly, when macrophage are cultured with BMP2 receptor-blocking MC3T3-E1 on the CS cements, the osteogenesis differentiation of the cells is significantly inhibited, indicating the important role of macrophages in biomaterial-induced osteogenesis via BMP2 receptors. It is assumed that it is an increase in the secretion of the BMP2 from the Raw 264.7 cell that is primarily involved in the promotion of the osteogenesis of the MC3T3-E1. These results provide valuable insights into both the mechanism of CS-stimulated osteogenesis, and strategies to optimize the evaluation system for the in vitro osteogenesis capacity of bone substitute biomaterials.

Preparation of the fast setting and degrading Ca-Si-Mg cement with both odontogenesis and angiogenesis differentiation of human periodontal ligament cells

Develop a fast setting and controllable degrading magnesium-calcium silicate cement (Mg-CS) by sol-gel, and establish a mechanism using Mg ions to stimulate human periodontal ligament cells (hPDLs) are two purposes of this study. We have used the diametral tensile strength measurement to obtain the mechanical strength and stability of Mg-CS cement; in addition, the cement degradation properties is realized by measuring the releasing amount of Si and Mg ions in the simulated body fluid. The other cell characteristics of hPDLs, such as proliferation, differentiation and mineralization were examined while hPDLs were cultured on specimen surfaces. This study found out the degradation rate of Mg-CS cements depends on the Mg content in CS. Regarding in vitro bioactivity; the CS cements were covered with abundant clusters of apatite spherulites after immersion of 24h, while less apatite spherulites were formatted on the Mg-rich cement surfaces. In addition, the authors also explored the effects of Mg ions on the odontogenesis and angiogenesis differentiation of hPDLs in comparison with CS cement. The proliferation, alkaline phosphatase, odontogenesis-related genes (DSPP and DMP-1), and angiogenesis-related protein (vWF and ang-1) secretion of hPDLs were significantly stimulated when the Mg content of the specimen was increased. The results in this study suggest that Mg-CS materials with this modified composition could stimulate hPDLs behavior and can be good bioceramics for bone substitutes and hard tissue regeneration applications as they stimulate odontogenesis/angiogenesis.

Influence of needle-like morphology on the bioactivity of nanocrystalline wollastonite--an in vitro study

In the past 2 decades, wollastonite has been studied thoroughly for its application as a bone implant material due to its biocompatibility, high mechanical strength, and excellent bioactivity when compared to calcium phosphates bioceramics. Wollastonite was prepared through the low-temperature sol-gel combustion method using urea as the fuel, nitrate ions and nitric acid as the oxidizer. Calcium nitrate and tetraethyl orthosilicate were taken as the source of calcium and silica. The synthesized wollastonite were characterized by Fourier transform infrared spectroscopy for the identification of characteristic functional group and powder X-ray diffraction for the phase identification. Employing urea as a fuel resulted in needle-like morphology of the particles, which was confirmed by scanning electron microscopy and transmission electron microscopy. It was observed that the needle-like morphology enhances the mechanical properties such as elasticity and compressive strength and also increases the surface area of the material, which could help in a rapid deposition of hydroxyapatite layer. These properties of wollastonite warrant its application as a new artificial bone material in the field of hard tissue engineering.

Osteogenesis of human adipose-derived stem cells on poly(dopamine)-coated electrospun poly(lactic acid) fiber mats

Electrospinning is a versatile technique to generate large quantities of micro- or nano-fibers from a wide variety of shapes and sizes of polymer. The aim of this study is to develop functionalized electrospun nano-fibers and use a mussel-inspired surface coating to regulate adhesion, proliferation and differentiation of human adipose-derived stem cells (hADSCs). We prepared poly(lactic acid) (PLA) fibers coated with polydopamine (PDA). The morphology, chemical composition, and surface properties of PDA/PLA were characterized by SEM and XPS. PDA/PLA modulated hADSCs' responses in several ways. Firstly, adhesion and proliferation of hADSCs cultured on PDA/PLA were significantly enhanced relative to those on PLA. Increased focal adhesion kinase (FAK) and collagen I levels and enhanced cell attachment and cell cycle progression were observed upon an increase in PDA content. In addition, the ALP activity and osteocalcin of hADSCs cultured on PDA/PLA were significantly higher than seen in those cultured on a pure PLA mat. Moreover, hADSCs cultured on PDA/PLA showed up-regulation of the ang-1 and vWF proteins associated with angiogenesis differentiation. Our results demonstrate that the bio-inspired coating synthetic degradable PLA polymer can be used as a simple technique to render the surfaces of synthetic biodegradable fibers, thus enabling them to direct the specific responses of hADSCs.

Human Dental Pulp Cells Responses to Apatite Precipitation from Dicalcium Silicates

Unraveling the mechanisms behind the processes of cell attachment and the enhanced proliferation that occurs as a response to the presence of calcium silicate-based materials needs to be better understood so as to expand the applications of silicate-based materials. Ions in the environment may influence apatite precipitation and affect silicate ion release from silicate-based materials. Thus, the involvement of apatite precipitate in the regulation of cell behavior of human dental pulp cells (hDPCs) is also investigated in the present study, along with an investigation of the specific role of cell morphology and osteocalcin protein expression cultured on calcium silicate (CS) with different Dulbecco's modified Eagle's medium (DMEM). The microstructure and component of CS cement immersion in DMEM and P-free DMEM are analyzed. In addition, when hDPCs are cultured on CS with two DMEMs, we evaluate fibronectin (FN) and collagen type I (COL) secretion during the cell attachment stage. The facilitation of cell adhesion on CS has been confirmed and observed both by scanning with an electron microscope and using immunofluorescence imaging. The results indicate that CS is completely covered by an apatite layer with tiny spherical shapes on the surface in the DMEM, but not in the P-free DMEM. Compared to the P-free DMEM, the lower Ca ion in the DMEM may be attributed to the formation of the apatite on the surfaces of specimens as a result of consumption of the Ca ion from the DMEM. Similarly, the lower Si ion in the CS-soaked DMEM is attributed to the shielding effect of the apatite layer. The P-free DMEM group releases more Si ion increased COL and FN secretion, which promotes cell attachment more effectively than DMEM. This study provides new and important clues regarding the major effects of Si-induced cell behavior as well as the precipitated apatite-inhibited hDPC behavior on these materials.

Poly(Dopamine)-Assisted Immobilization of Xu Duan on 3D Printed Poly(Lactic Acid) Scaffolds to Up-Regulate Osteogenic and Angiogenic Markers of Bone Marrow Stem Cells

Three-dimensional printing is a versatile technique to generate large quantities of a wide variety of shapes and sizes of polymer. The aim of this study is to develop functionalized 3D printed poly(lactic acid) (PLA) scaffolds and use a mussel-inspired surface coating and Xu Duan (XD) immobilization to regulate cell adhesion, proliferation and differentiation of human bone-marrow mesenchymal stem cells (hBMSCs). We prepared PLA scaffolds and coated with polydopamine (PDA). The chemical composition and surface properties of PLA/PDA/XD were characterized by XPS. PLA/PDA/XD controlled hBMSCs' responses in several ways. Firstly, adhesion and proliferation of hBMSCs cultured on PLA/PDA/XD were significantly enhanced relative to those on PLA. In addition, the focal adhesion kinase (FAK) expression of cells was increased and promoted cell attachment depended on the XD content. In osteogenesis assay, the osteogenesis markers of hBMSCs cultured on PLA/PDA/XD were significantly higher than seen in those cultured on a pure PLA/PDA scaffolds. Moreover, hBMSCs cultured on PLA/PDA/XD showed up-regulation of the ang-1 and vWF proteins associated with angiogenic differentiation. Our results demonstrate that the bio-inspired coating synthetic PLA polymer can be used as a simple technique to render the surfaces of synthetic scaffolds active, thus enabling them to direct the specific responses of hBMSCs.

Poly(dopamine) coating of 3D printed poly(lactic acid) scaffolds for bone tissue engineering

3D printing is a versatile technique to generate large quantities of a wide variety of shapes and sizes of polymer. The aim of this study is to develop functionalized 3D printed poly(lactic acid) (PLA) scaffolds and use a mussel-inspired surface coating to regulate cell adhesion, proliferation and differentiation of human adipose-derived stem cells (hADSCs). We prepared PLA 3D scaffolds coated with polydopamine (PDA). The chemical composition and surface properties of PDA/PLA were characterized by XPS. PDA/PLA modulated hADSCs' responses in several ways. Firstly, adhesion and proliferation, and cell cycle of hADSCs cultured on PDA/PLA were significantly enhanced relative to those on PLA. In addition, the collagen I secreted from cells was increased and promoted cell attachment and cell cycle progression were depended on the PDA content. In osteogenesis assay, the ALP activity and osteocalcin of hADSCs cultured on PDA/PLA were significantly higher than seen in those cultured on pure PLA scaffolds. Moreover, hADSCs cultured on PDA/PLA showed up-regulation of the ang-1 and vWF proteins associated with angiogenic differentiation. Our results demonstrate that the bio-inspired coating synthetic PLA polymer can be used as a simple technique to render the surfaces of synthetic scaffolds active, thus enabling them to direct the specific responses of hADSCs.

The synergistic effects of Chinese herb and injectable calcium silicate/β-tricalcium phosphate composite on an osteogenic accelerator in vitro

This study investigates the physicochemical and biological effects of traditional Chinese medicines on the β-tricalcium phosphate (β-TCP)/calcium silicate (CS) composites of bone cells using human dental pulp cell. CS is an osteoconductive and bioactive material. For this research we have combined β-TCP and CS and check its effectiveness, a series of β-TCP/CS composites with different ratios of Xu Duan (XD) were prepared to make new bioactive and biodegradable biocomposites for bone repair. XD has been used in Traditional Chinese Medicine for hundreds of years as an antiosteoporosis, tonic and antiaging agent for the therapy of low back pain, traumatic hematoma, threatened abortion and bone fractures. Formation of bone-like apatite, the diametral tensile strength, and weight loss of composites were considered before and after immersion in simulated body fluid (SBF). In addition, we also examined the effects of XD released from β-TCP/CS composites and in vitro human dental pulp cell (hDPCs) and studied its behavior. The results show the XD-contained paste did not give any demixing when the weight ratio of XD increased to 5-10 % due to the filter-pressing effect during extrusion through the syringe. After immersion in SBF, the microstructure image showed a dense bone-like apatite layer covered on the β-TCP/CS/XD composites. In vitro cell experiments shows that the XD-rich composites promote human dental pulp cells (hDPCs) proliferation and differentiation. However, when the XD quantity in the composite is more than 5 %, the amount of cells and osteogenesis protein of hDPCs were stimulated by XD released from β-TCP/CS composites. The combination of XD in degradation of β-TCP and osteogenesis of CS gives strong reason to believe that these calcium-based composite cements may prove to be promising bone repair materials.

Stimulatory effects of the fast setting and suitable degrading Ca–Si–Mg cement on both cementogenesis and angiogenesis differentiation of human periodontal ligament cells

The purpose of this study is to develop a fast setting and suitable degrading Mg–calcium silicate cement (Mg–CS) and a mechanism using Mg ions to stimulate human periodontal ligament cells (hPDLCs).