Composite monetite/amorphous calcium phosphate bone cement promotes bone regeneration

Monetite (MC) is a type of calcium phosphate cement (CPC). It has various morphologies, continuous degradation and absorption properties; however, its high porosity will affect its mechanical properties. There is minimal research on MC is immature. Amorphous calcium phosphate (ACP) is widely used and exhibits good biocompatibility; however, it is unstable. In this study, MC was combined with ACP at different weight ratios to form new types of bone cements. The mechanical properties, biocompatibility, and inductive ability for osteogenesis and osteoclasts of different MC/ACP composite bone cements were evaluated. The biocompatibility and effects on osteogenic and osteoclast differentiation of MC/ACP composite bone cements were investigated in vitro using mouse bone marrow mesenchymal stem cells (mBMMSCs) and mouse monocyte/macrophage cell line RAW 264.7. RAW 264.7 cells can differentiate into osteoclasts by osteoclast differentiation. The results indicated that the overall performance of the MC/ACP composite bone cement was better than that of the MC or ACP alone. Compared to the other groups, the biocompatibility of MC75 (75 wt% MC and 25 wt% ACP) was optimal; it was able to induce mBMMSCs osteogenesis to a greater extent. MC75 was the least favorable for the proliferation, migration, and differentiation of osteoclasts. The mechanical properties, setting time and injectability of MC75 meet clinical application requirements. This study demonstrated that MC75 is a promising bone cement for repairing bone defects.     

Mechanical properties and biocompatibility of MgO / Ca3(PO4)2 composite ceramic scaffold with high MgO content based on digital light processing

Magnesium oxide-calcium phosphate (MgO/Ca3(PO4)2) composite ceramic materials are considered a promising class of bioactive materials, expected to be used in artificial bone scaffolds. However, there are few pieces of research on the content of magnesium oxide in composite ceramic scaffolds. To study the effect of magnesium oxide content on the biocompatibility and mechanical properties of magnesium oxide-calcium phosphate composite ceramic scaffolds, six groups of scaffolds with magnesium oxide content of 10 wt%, 20 wt%, 30 wt%, 40 wt%, 100 wt%, and 0 wt% were produced by digital light processing (DLP) printing technology. And scaffolds’ pores size and porosity percentage were 0.6–1 mm and 50%, respectively. The compressive strength of the scaffold increased with the magnesium oxide proportion, and the 40 wt% group was almost twice that of the 0 wt% magnesium oxide group. The 40 wt% and 0 wt% magnesium oxide groups performed better for biocompatibility. Comprehensive analysis of the biocompatibility and mechanical properties of the scaffold confirmed that the 40 wt% magnesium oxide group was the best. The results show that high magnesium oxide content enhanced the mechanical properties and achieved well biocompatibility of the composite scaffolds, broadening the scope of future experimental research.     

Setting behavior,mechanical property and biocompatibility of anti-washout wollastonite/calcium phosphate composite cement

In this study, a calcium phosphate-based composite cement was fabricated by incorporating wollastonite (WS) into calcium phosphate cement (CPC). The setting behavior, microstructure, injectability, porosity, compressive strength, anti-washout property, in vitro degradation, and cell behavior of the WS/CPC composite cement were systematically investigated. The results revealed that the addition of WS promoted the hydration reaction but without affecting the hydration product of CPC. The injectability of the WS/CPC composite cement declined with the incorporation of WS to a certain extent, especially when the content of WS was higher than 20 wt%. By incorporating appropriate amount of WS into CPC, the composite cement obtained feasible setting time, enhanced compressive strength, improved anti-washout performance, and favorable biocompatibility. On the basis of its improved comprehensive application-relevant properties, the WS/CPC composite cement is prospective to be a promising biomaterial for bone defect repairing.     

Fabrication and performance of calcium phosphate cement/small intestinal submucosa composite bionic bone scaffolds with different microstructures

The microstructure of the tissue has a very important determining effect on its performance. Herein, two calcium phosphate cement (CPC)/small intestinal submucosa(SIS) composites bionic bone scaffolds with different microstructures were fabricated by rolling or/ and assembling method. The microstructure, 3D morphology, the crystal phase and mechanical properties of the scaffolds were investigated by micro CT, XRD, FIIR, SEM and electronic universal testing machines respectively. The results showed that the pore size of all scaffolds are in the range of 100–400?µm, which are beneficial to cells growth, migration, and tissue vascularization. Their porosity and the specific surface area were 14.53?±?0.76%, 8.74?±?1.38?m²/m³ and 32?±?0.58%, 26.75?±?2.69?m²/m³ separately. The high porosity and the large specific surface area can provide a larger space and contact area for cells adhesion and proliferation. Meanwhile, compressive strength of the scaffolds soaked were 10?MPa and 27?MPa, about 1.2 folds and 3.2 folds of the original scaffolds, respectively. The results are derived from different microstructures of the scaffolds and chemical bonds between SIS and new phases (hydroxyapatite), and the scaffolds performance steadily increased at near the physiological conditions. Finally, biocompatibility of the scaffolds was evaluated by CCK8, bionic microstructure scaffolds are no cytotoxicity and their biocompatibility is favorable. Based on the microstructure, compressive strength and cytotoxicity of the scaffolds, bionic Harvarsin microstructure CPC/SIS composite scaffold is expected to turn into a scaffold with the excellent properties of real bone.     

Microarchitectural and mechanical characterization of chitosan/hydroxyapatite/demineralized bone matrix composite scaffold

Porous degradable scaffolds are used extensively in bone tissue engineering. As well as material type, the architectural and mechanical characterizations of scaffolds are important to facilitate cell and tissue growth. Matrices composed of hydroxyapatite (HA), chitosan (CS) and demineralized bone matrix (DBM) may create an appropriate environment for the regeneration of bones. In this study, CS/HA/DBM scaffolds with sufficient structural integrity and high interconnected porosity were produced using different combinations of CS, HA and DBM. Both mechanical and biological properties of porous scaffolds were determined by local microarchitecture whose parameters were quantified based on micro computed tomography (Micro-CT) analysis. Within porosity range of 48–65%, the ranges of average compressive modulus and ultimate strength of the scaffolds were 3 ± 1–6 ± 1 kPa and 11 ± 2–24 ± 2 kPa, respectively. With the increase of HA concentration at the equal weight of DBM, the average trabecular thickness and trabecular separation increased and bone surface/volume ratio decreased, resulting in higher volume fraction and lower total porosity. In vitro, MC3T3-E1 preosteoblast cells were used to investigate cell attachment, spreading and proliferation on the scaffolds via hematoxyline and eosin (HE), scanning electron microscopy (SEM) and MTS assay. The results showed that MC3T3-E1 cells adhered to the surface of composite scaffolds, cell number increased with culture time. Cell viability increased with the HA particles decreased, changed little with the DBM increased. Consideration of the microarchitectural and mechanical characterization and biocompatibility of the scaffolds, 3:3:1.5 and 3:5:1.5 groups were believed to be the best in our study.     

Fabrication,characterization and cellular biocompatibility of porous biphasic calcium phosphate bioceramic scaffolds with different pore sizes

Facile wet-chemical methods are applied to synthesize hydroxyapatite and β-tricalcium phosphate nanoparticles, respectively. Porous biphasic calcium phosphate (BCP) bioceramic scaffolds are then fabricated using as-prepared HA and β-tricalcium phosphate nanoparticle powders. The macro pore diameter of BCP bioceramic scaffolds can be controlled by adjusting the amount of surfactants. The average diameter of the macro pores in BCP bioceramic scaffolds increases from 100 to 600 µm with the decrease amount of sodium dodecyl sulfate from 0.8 to 0.5 g, respectively. The BCP bioceramic scaffolds gradually degrade and the calcium-phosphate compounds fully deposit when soaking in simulated body fluid solution. Moreover, The BCP bioceramic scaffolds have outstanding biocompatibility to promote the cellular growth and proliferation of human dental pulp stem cells (hDPSCs). The hDPSCs also demonstrate favorable cellular adhering capacity on the pore surface of scaffolds, especially on the scaffolds with 100–200 µm pore diameter. The porous BCP bioceramic scaffold with inter-connected pore structure, outstanding in vitro cellular biocompatibility, favorable cell viability and adhesion ability will be a promising biomaterial for bone or dentin tissue regeneration.     

Modelling the mechanical properties of microporous and macroporous biphasic calcium phosphate bioceramics

Macroporous biphasic calcium phosphate bioceramics, for use as bone substitutes, have been fabricated by cold isostatic pressing and conventional sintering, using naphtalen particles as a porogen to produce macropores. The resulting ceramics, composite materials made of hydroxyapatite and β-tricalcium phosphate (TCP) containing 45% macropores and with various microporosities, have been submitted to compression and three-point bending tests, toughness tests by single-edge-notched-bending (SENB), and spherical indentation tests. By combining two approaches at two different scales, one for closed porosity and one for open porosity, a model is established to describe mechanical properties as a function of the amount and morphology of porosity. The model assumes a quasi-continuous matrix containing macropores, the matrix being itself microporous, and considers that fracture always initiates on a macropore. The preliminary mechanical tests performed on the sintered ceramics tend to validate the modelling approach.     

Fabrication of a zirconia/calcium silicate composite scaffold based on digital light processing

Zirconia (ZrO₂) and calcium silicate (CS) are widely used in bone repair. Zirconia has excellent mechanical properties, while calcium silicate has exceptional biological activity. A porous ZrO₂/CS composite ceramic scaffold was formed by digital light processing (DLP) technology in this study. The microstructure analysis demonstrated that CS was embedded between ZrO₂ particles. Mechanical tests showed that interconnected CS particles could improve mechanical properties, while discrete CS particles led to a decrease in that. Cell experiments showed that adding CS to ZrO₂ had a positive effect on cell proliferation and differentiation. In vitro degradation test showed that the weight loss of scaffolds in four weeks increased form ?0.63%–1.42% with the increase of CS content. Moreover, the degradation of scaffold promoted the deposition of apatite, which was beneficial to the integration of the scaffold with living bone. In conclusion, the ZrO₂/CS composite scaffold had better biocompatibility compared with the ZrO₂ scaffold, which showed a potential solution for 3D printing bone repair scaffolds.     

Porous Biphasic Calcium Phosphate Granules from Oyster Shell Promote the Differentiation of Induced Pluripotent Stem Cells

Oyster shells are rich in calcium, and thus, the potential use of waste shells is in the production of calcium phosphate (CaP) minerals for osteopathic biomedical applications, such as scaffolds for bone regeneration. Implanted scaffolds should stimulate the differentiation of induced pluripotent stem cells (iPSCs) into osteoblasts. In this study, oyster shells were used to produce nano-grade hydroxyapatite (HA) powder by the liquid-phase precipitation. Then, biphasic CaP (BCP) bioceramics with two different phase ratios were obtained by the foaming of HA nanopowders and sintering by two different two-stage heat treatment processes. The different sintering conditions yielded differences in structure and morphology of the BCPs, as determined by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) surface area analysis. We then set out to determine which of these materials were most biocompatible, by co-culturing with iPSCs and examining the gene expression in molecular pathways involved in self-renewal and differentiation of iPSCs. We found that sintering for a shorter time at higher temperatures gave higher expression levels of markers for proliferation and (early) differentiation of the osteoblast. The differences in biocompatibility may be related to a more hierarchical pore structure (micropores within macropores) obtained with briefer, high-temperature sintering.     

Study on the improvement of compressive strength and fracture toughness of calcium phosphate cement

Calcium phosphate cement (CPC) has superior properties, such as excellent bioactivity, biocompatibility, osteoconductivity and degradability, since its hydration product is hydroxyapatite (HA). As a novel cement material, CPC also shows injectable and self-setting properties. However, the compressive strength (CS) and fracture toughness of most CPCs are far lower than that of human weight-bearing bones, which largely limit their applications in the repairment of weight-bearing bones. To improve the CS and fracture toughness of CPC, several methods, including in-situ reinforcement by Ca4(PO4)2O (TTCP) ceramic particles, suitable nanofibers are introduced in this study. The maximal CS of CPC prepared with TTCP (average particle size of 22.3 ± 0.4 μm) reached to 98.4 MPa, which is close to the strength of human long bones. The enhanced CS of CPC was attributed to the in-situ reinforcing effect of residual TTCP particles. Tendon collagen slices and HA nanofibers were used to improve the fracture toughness of CPC. The flexural strength (FS) and the work of facture (WOF) of CPC were slightly increased by adding HA nanofibers but was significantly increased by the addition of tendon collagen slices. With 1.000 wt% tendon collagen slices, the FS and WOF of CPC were increased by 61.3% and 22.6 times, respectively.     

Preparation of high strength lamellar porous calcium silicate ceramics by directional freeze casting

In this study, porous calcium silicate (CS) ceramics with oriented arrangement of lamellar macropore structure were prepared by directional freeze casting method. The lamellar macropores were connected by the micropores on the pore wall, which had good pore interconnectivity. The effects of solid loading of the slurry, freezing temperature, sintering additive content, and sintering temperature on the microstructures and compressive strength of the synthesized porous materials were investigated systematically. The results showed that with the increase of solid loading (≤20 vol%) and sintering additive content, the sizes of lamellar pores and pore walls increased gradually, the open porosity decreased and the compressive strength increased. The sintering temperature had little effect on the pore size of the ceramics, but increasing the sintering temperature (≤1050 °C) promoted the densification of the pore wall, reduced the porosity, and improved the strength. The decrease of freezing temperature had little effect on porosity, but it reduced the size of lamellar pore and pore wall, so as to improve the strength. Finally, porous CS ceramics with lamellar macropores of about 300–600 μm and 2–10 μm micropores on the pore wall were obtained. The porous CS ceramics had high pore interconnectivity, an open porosity of 66.25% and a compressive strength of 5.47 MPa, which was expected to be used in bone tissue engineering.     

DLP 3D printing porous β-tricalcium phosphate scaffold by the use of acrylate/ceramic composite slurry

Digital light processing (DLP) 3D printing has been utilized to fabricate controlled porous β-tricalcium phosphate (β-TCP) scaffolds, which promote cell adhesion and angiogenesis during bone regeneration. However, the current limitation of DLP 3D printing for the fabrication of β-TCP scaffold is how to prepare a low viscosity ceramic slurry and remove the toxicity of residual non-polymerized slurry. The present study has developed a low viscosity ceramic slurry system by mixing β-TCP with photosensitive acrylate resin, and the viscosity of slurry is about 3 Pa s and the solid content of β-TCP can be as high as 60 wt%. After optimizing the ratio of slurry, printing, degreasing and sintering processes, the maximum compressive strength of the DLP printed scaffolds reaches up to 9.89 MPa, while the porosity keeps ca. 40%. According to the proliferation of cells, it confirms the preserved biocompatibility of DLP-fabricated β-TCP scaffolds. These porous scaffolds made by DLP 3D printing technology is of great significance for bone regeneration, and will also help to expand the application of DLP technology in biomedical field.     

Fabrication and characterization of honeycomb β-tricalcium phosphate scaffolds through an extrusion technique

In this study, for the first time honeycomb β-tricalcium phosphate (β-TCP) scaffolds were fabricated through an extrusion technique. The physicochemical properties and cell behaviors of the honeycomb β-TCP scaffolds were investigated. The results showed that scaffolds were characterized by ordered channel-like macropores and unidirectional interconnection. The pore structure and mechanical strength could be tailored by changing the parameters of extrusion molds. The pore size of scaffolds was in the range of 400–800 µm approximately, while their compressive strength parallel to the pore direction and porosity ranged from 14 to 20 MPa and 60–70%, respectively. The in vitro cell behavior demonstrated that cells could well attach on the surfaces and grow into the inner channel-like pores of thescaffolds; the scaffolds with higher porosity showed better cell proliferation but poorer cell differentiation. The honeycomb scaffolds fabricated by extrusion technique are potential candidate for bone tissue engineering.     

Incorporation of graphene oxide and calcium phosphate in the PCL/PHBV core-shell nanofibers as bone tissue scaffold

Bone tissue scaffolds should have both desired mechanical stability and cell activities including biocompatibility, cell differentiation, and maturation. Also, suitable mineralization is another key factor for these materials. Hence, in current work, in order to achieve a scaffold with desired mechanical and bioactivity properties, core-shell nanofibers based on the polycaprolactone and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with different concentration of graphene oxide (GO) (0.5, 1, and 1.5 wt%) and calcium phosphate (CP) (1 and 3 wt%) were prepared to utilize as bone scaffold. Microstructure of nanofibers observed by field emission scanning electron microscope (FE-SEM) and results exhibited that the most of nanofibers had 270–500 nm diameter. Attenuated total reflectance Fourier transform infrared spectroscopy and energy dispersive X-ray evaluations verified appearance of GO and CP into the electrospun scaffolds (ES). Transmission electron microscopy analysis endorsed core-shell structure of nanofibers. X-ray diffraction study moreover determination of semicrystalline structure, verified presence of GO and CaPO₄ into the nanofibers. Water contact angle demonstrates that, ES2 and ES3 situated in suitable domain of hydrophilicity. Tensile analysis determined that, ES2, ES3, and ES4 had the highest mechanical properties for use as bone scaffold. Cell viability assessment confirmed biocompatibility of scaffold during 7 days. Alkaline phosphatase and alizarin red staining exhibited maturating and differentiating of osteocytes after 21 days seeding on the scaffolds.     

Formation of organic-inorganic composite materials based on cellulose <Emphasis Type="Italic">Acetobacter xylinum</Emphasis> and calcium phosphates for medical applications

The formation of composites based on the cellulose Acetobacter xylinum and calcium phosphates has been investigated using X-ray diffraction, electron diffraction, electron microscopy, energy-dispersive analysis, and differential scanning calorimetry. It has been demonstrated that the planar morphology of calcium phosphate nanoparticles capable of interacting with nanofibrils of the cellulose matrix is an important factor providing interfacial contacts in the formation of organic-inorganic composite materials. It has been established that magnesium-containing calcium phosphates represent two-phase systems consisting of calcium magnesium phosphate Ca_2.6Mg_0.4(PO₄)₂ (whitlockite) and hydroxyapatite Ca₅(PO₄)₃(OH). The biocompatibility of the composite materials based on two-phase calcium phosphate systems and the temperature range of their stability (∼20–250°C) determined by the thermal stability of the organic component have been investigated.     

Biocompatibility and strengthening of porous hydroxyapatite scaffolds using poly(l-lactic acid) coating

Hydroxyapatite (HA) is a well-known biocompatible bone substitute. Porous HA is more resorbable and osteoconductive compared with non-porous HA, and has been studied both experimentally and clinically. However, the mechanical strength of porous HA scaffolds is known to be weak. In this study, we developed a porous HA scaffold coated with a synthetic biodegradable polymer, poly(l-lactic acid) (PLLA), to strengthen the scaffold. PLLA-coated HA pellets were used to investigate the in vitro proliferation and alkaline phosphatase (ALP) activity of osteoblasts. PLLA-coated porous HA scaffolds were observed using scanning electron microscopy to investigate surface characteristics, porosity, and mechanical strength. PLLA coating concentration varied from 2 to 10 wt%. Osteoblast proliferation was higher in HA samples coated with PLLA compared with non-coated. ALP activity was highest on 8 wt% PLLA-coating after 3 days and on 4 wt% and 6 wt% PLLA after 9 and 12 days. Porous HA scaffolds with higher concentrations of PLLA were found to have a smoother, flatter surface. This enhanced proliferation and attachment of osteoblasts onto the porous HA scaffold. PLLA solution at a concentration of 10 wt% decreased scaffold porosity to half that of HA scaffolds with no PLLA coating. Scaffold mechanical strength was increased two-fold with a PLLA concentration of 2 wt%. Based on in vitro experimentation, it can be concluded that PLLA-coating on porous HA scaffolds enhances both the biocompatibility and the mechanical strength.     

An Injectable Enzymatically Crosslinked and Mechanically Tunable Silk Fibroin/Chondroitin Sulfate Chondro-Inductive Hydrogel

An injectable hybrid hydrogel is synthesized, comprising silk fibroin (SF) and chondroitin sulfate (CS) through di-tyrosine formation bond of SF chains. CS and SF are reported with excellent biocompatibility as tissue engineering scaffolds. Nonetheless, the rapid degradation rate of pure CS scaffolds presents a challenge to effectively recreate articular cartilage. As CS is one of the cartilage extracellular matrix (ECM) components, it has the potential to enhance the biological activity of SF-based hydrogel in terms of cartilage repair. Therefore, altering the CS concentrations (i.e., 0 wt%, 0.25 wt%, 0.5 wt%, 1 wt%, and 2 wt%), which are interpenetrated between SF β-sheets and chains, can potentially adjust the physical, chemical, and mechanical features of these hybrid hydrogels. The formation of β-sheets by 30 days of immersion in de-ionized (DI) water can improve the compression strength of the SF/CS hybrid hydrogels in comparison with the same SF/CS hybrid hydrogels in the dried state. Biological investigation and observation depicts proper cell attachment, proliferation and cell viability for C28/I2 cells. Gene expression of sex-determining region YBox 9 (SOX9), Collagen II α1, and Aggrecan (AGG) exhibits positive C3H10T1/2 growth and expression of cartilage-specific genes in the 0.25 wt% and 0.5 wt% SF/CS hydrogels.     

Bioprinted 3D calcium phosphate scaffolds with gentamicin releasing capability

We investigated the suitability of 3D printed calcium phosphate scaffolds as drug carriers. The 3D powder printing process utilized α-tricalcium phosphate (α-TCP) as a solid phase and deionized water with 2.5% disodium hydrogen phosphate as a setting accelerator. The antibiotic gentamicin sulfate was incorporated by mixing it into α-TCP powder before printing. Two different concentrations of gentamicin (3?wt%, 7?wt%) were used to study the correlation between drug release kinetics and gentamicin content in the scaffolds. The scaffolds were hardened at 100% humidity. The synthesized scaffolds were characterized in terms of morphology, composition, mechanical strength, in vitro bioactivity and drug release kinetics. X-ray diffraction (XRD) analysis revealed that the α-TCP converted into calcium deficient hydroxyapatite (CDHA) during the printing process. Scanning electron microscopy (SEM) showed the typical needle-like structure of CDHA. Gentamicin release was investigated for a period of two weeks with an initial burst release. The produced scaffolds formed calcium enriched apatite crystals on their surface after three days of incubation in simulated body fluid.     

Porous alumina scaffolds chemically modified by calcium phosphate minerals and their application in bone grafts

The chemical modification of porous ceramic scaffold surfaces with calcium phosphate surges as an alternative to improve the bioactivity to be used as bone grafts. The biomimetic method has been commonly used to modify surfaces of Ti alloys but surges as alternative to modify ceramic biomaterials. Herein, we modified the surface of Al₂O₃ scaffolds with calcium phosphate minerals and strontium using the biomimetic method. The scaffolds were chemically treated using H₃PO₄ solution and then immersed in simulated body fluid 5× solution for 14 days. For the incorporation of strontium, they were immersed in an aqueous solution of 100 ppm analytical-grade Sr(NO₃)₂ under magnetic stirring. The samples were characterized by scanning electron microscopy, X-ray microtomography, X-ray diffraction, near-infrared spectroscopy, inductively coupled plasma emission spectroscopy, and energy-dispersive X-ray spectroscopy. The biocompatibility and ability to differentiate osteoblasts in vitro were evaluated using human cells. The incorporation of strontium into the phosphate structure was verified. Scaffolds were obtained with high porosity, three-dimensional structures, and the preferential adhesion and maturation of osteoblastic cells, which are essential to promote bone regeneration in vivo.     

Physical and physicochemical evaluation of calcium phosphate cement made using human derived blood plasma

Abstract

In the present work, calcium phosphate cement was made by mixing a solid phase and blood plasma as liquid phase. The basic properties of the cement (called BPC) were compared with those of conventional calcium phosphate cement (c-CPC) where distilled water was used as liquid. BPC had better consistency and injectability than c-CPC but longer setting time. In both cements, the reactants were converted into apatite phase after immersing in simulated body fluid but the phase formed in BPC had lower crystallinity than the phase formed in c-CPC. The set BPC was stronger than c-CPC, having a compressive strength (CS) of about 2–6 MPa after 24 h incubation at 37°C. The CS reduced during soaking at early stage but was relatively improved at the end of soaking period (day 7). In contrast, an increase in CS was observed in c-CPC during soaking period.