Na-doped β-tricalcium phosphate: physico-chemical and in vitro biological properties

Synthetic calcium phosphate ceramics as β-tricalcium phosphate (Ca₃(PO₄)₂; β-TCP) are currently successfully used in human bone surgery. The aim of this work was to evaluate the influence of the presence of sodium ion in β-TCP on its mechanical and biological properties. Five Na-doped-β-TCP [Ca_10.5−x/2Na _x (PO₄)₇, 0 ≤ x ≤ 1] microporous pellets were prepared via solid phase synthesis, and their physico-chemical data (lattice compacity, density, porosity, compressive strength, infrared spectra) denote an increase of the mechanical properties and a decrease of the solubility when the sodium content is raised. On the other hand, the in vitro study of MC3T3-E1 cell activity (morphology, MTS assay and ALP activity) shows that the incorporation of sodium does not modify the bioactivity of the β-TCP. These results strongly suggest that Na-doped-β-TCP appear to be good candidates for their use as bone substitutes.     

Surface energy of hydroxyapatite and β-tricalcium phosphate ceramics driving serum protein adsorption and osteoblast adhesion

The main objective of this work was to evaluate the specific role of calcium phosphates surface energy on serum protein adsorption and human osteoblast adhesion, by isolating chemical effects from those caused by topography. Highly dense phosphate ceramics (single-phase hydroxyapatite HA and β-tricalcium phosphates β-TCP) presenting two distinct nano roughnesses were produced. Some samples were gold-sputter coated in order to conveniently mask the surface chemical effects (without modification of the original roughness) and to study the isolated effect of surface topography on cellular behavior. The results indicated that the nano topography of calcium phosphates strongly affected the protein adsorption process, being more important than surface chemistry. The seeding efficacy of osteoblasts was not affected nor by the topography neither by the calcium phosphate chemistries but the β-TCP chemistry negatively influenced cell spreading. We observed that surface hydrophobicity is another way to change protein adsorption on surfaces. The decrease of the polar component of surface energy on gold-coated samples leaded to a decreased albumin and fibronectin adsorption but to an increased cell adhesion. Overall, this work contributes to better understand the role of topography and surface chemistry of calcium phosphates in serum protein adsorption and osteoblast adhesion.     

Synthesis and fabrication of β-tricalcium phosphate (whitlockite) ceramics for potential prosthetic applications

A novel process is described for preparing dense, polycrystalline tricalcium phosphates. Single-phase compositional integrity is achieved by introducing catalytic amounts of sulphate ion and this pore free material has close to theoretical density. Preliminary mechanical properties include a compression strength of 687 MN m^–2 and a tensile strength of 154 MN m^–2. The relationship between processing variables and phase composition, microstructure, strength and translucence is described. The material has promise for bone implant applications.     

Microstructural,physico-chemical and mechanical characterisation of Sansevieria cylindrica fibres – An exploratory investigation

The microstructural, physical, chemical and mechanical properties of Sansevieria cylindrica fibres are described for the first time in this work. A microstructural analysis of S. cylindrica leaves showed the presence of structural fibres and arch fibres. Polarised light microscopy and scanning electron microscopy of these fibres revealed a hierarchical cell structure that consisted of a primary wall, a secondary wall, a fibre lumen and middle lamellae. The cross-sectional area and porosity fraction of the fibre were estimated to be approximately 0.0245 mm² and 37%, respectively. The fibre density and fineness were approximately 0.915 ± 0.005 g/cm³ and 9 Tex, respectively. An X-ray diffraction and Fourier transform infrared analysis of the fibres showed the presence of cellulose I_β with a crystallinity index of 60%. Tensile tests showed that the corrected Young’s modulus was approximately 7 GPa, the tensile strength was 658 MPa, and the total elongation was between 10% and 12%.     

Phase transformation and structural characteristics of zinc-incorporated β-tricalcium phosphate

Biological performance of bioceramics such as calcium phosphate has been proved to be improved by substitution of different ions like Mg, Sr and Si. In this study, different amounts of Zn ions in nitrate form were incorporated into β-tricalcium phosphate in which various molar ratios of Ca:Zn were achieved: 3:0, 2.8:0.2, 2.6:0.4, 2.4:0.6, and 2.2:0.8. The mixtures were heated at different temperatures ranging from 800–1100 °C. The phase composition, amount of each phase and lattice parameters of β-tricalcium phosphate were determined by means of X-ray diffractometry and coupled software. Also, solubility of the heated mixtures was investigated by determining the amount of Ca and Zn released into a simulated body fluid during 120 h. The results revealed that only limited amount of Zn ions could be incorporated into β-tricalcium phosphate lattice and ZnO phase was formed when high content of zinc nitrate was introduced in initial mixture. Both a and c lattice parameters of β-tricalcium phosphate were reduced by adding Zn. The release rate of calcium ions into the simulated body fluid was approximately constant during 120 h while for Zn minor release was observed.     

Fabrication and biological characteristics of β-tricalcium phosphate porous ceramic scaffolds reinforced with calcium phosphate glass

The fabrication process, compressive strength and biocompatibility of porous β-tricalcium phosphate (β-TCP) ceramic scaffolds reinforced with 45P₂O₅–22CaO–25Na₂O–8MgO bioglass (β-TCP/BG) were investigated for their suitability as bone engineering materials. Porous β-TCP/BG scaffolds with macropore sizes of 200–500 μm were prepared by coating porous polyurethane template with β-TCP/BG slurry. The β-TCP/BG scaffolds showed interconnected porous structures and exhibited enhanced mechanical properties to those pure β-TCP scaffolds. In order to assess the effects of chemical composition of this bioglass on the behavior of osteoblasts cultured in vitro, porous scaffolds were immersed in simulated body fluid (SBF) for 2 weeks, and original specimens (without soaked in SBF) seeded with MC3T3-E1 were cultured for the same period. The ability of inducing apatite crystals in simulated body fluid and the attachment of osteoblasts were examined. Results suggest that apatite agglomerates are formed on the surface of the β-TCP/BG scaffolds and its Ca/P molar ratio is ~1.42. Controlling the crystallization from the β-TCP/BG matrix could influence the releasing speed of inorganic ions and further adjust the microenvironment of the solution around the β-TCP/BG, which could improve the interaction between osteoblasts and the scaffolds.     

Repair of goat tibial defects with bone marrow stromal cells and β-tricalcium phosphate

Tissue engineering techniques have been proven effective in bone regeneration and repairing load-bearing bone defects. Previous studies, however, have heretofore been limited to the use of slowdegradable or natural biomaterials as scaffolds. There are, however, no reports on using biodegradable, synthetic beta-tricalcium phosphate (β-TCP) as scaffolds to repair weight-bearing bone defects in large animals. In the present study, highly porous β-TCP scaffolds prepared by the polymeric sponge method were used to repair goat tibial defects. Fifteen goats were randomly assigned to one of three groups, and a 26 mm-long defect at the middle part of the right tibia in each goat was created. In Group A (six goats), a porous β-TCP ceramic cylinder that had been loaded with osteogenically induced autologous bone marrow stromal cells (BMSCs) was implanted in the defect of each animal. In Group B (six goats), the same β-TCP ceramic cylinder without any cells loaded was placed in the defect. In Group C (three goats), the defect was left untreated. In Group A, bony union can be observed by gross view, X-ray and micro-computed tomography (Micro-CT) detection, and histological observation at 32 weeks post-implantation. The implanted β-TCP scaffolds were almost completely replaced by tissue-engineered bone. Bone mineral density in the repaired area of Group A was significantly higher (p < 0.05) than that of Group B, in which scant new bone was formed in each defect and the β-TCP hadn’t been completely resorbed at 32 weeks. Moreover, the tissue-engineered bone of Group A had similar biomechanical properties as that of the normal left tibia in terms of bending strength and Young’s modulus (p > 0.05). In Group C, little or no new bone was formed, and non-union occurred, showing that the 26 mm segmental defect of the goat tibia was critical sized at 32 weeks. Thus, it can be concluded that the mechanical properties of the BMSCs/β-TCP composites could be much improved via tissue engineering approach and β-TCP might be used to repair the weight-bearing segmental defects of goat tibias. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Correlation between properties and microstructure of laser sintered porous β-tricalcium phosphate bone scaffolds

Abstract

A porous β-tricalcium phosphate (β-TCP) bioceramic scaffold was successfully prepared with our homemade selective laser sintering system. Microstructure observation by a scanning electron microscope showed that the grains grew from 0.21 to 1.32 μm with the decrease of laser scanning speed from 250 to 50 mm min^?1. The mechanical properties increased mainly due to the improved apparent density when the laser scanning speed decreased to 150 mm min^?1. When the scanning speed was further decreased, the grain size became larger and the mechanical properties severely decreased. The highest Vickers hardness and fracture toughness of the scaffold were 3.59 GPa and 1.16 MPa m^1/2, respectively, when laser power was 11 W, spot size was 1 mm in diameter, layer thickness was 0.1–0.2 mm and laser scanning speed was 150 mm min^?1. The biocompatibility of these scaffolds was assessed in vitro with MG63 osteoblast-like cells and human bone marrow mesenchymal stem cells. The results showed that all the prepared scaffolds are suitable for cell attachment and differentiation. Moreover, the smaller the grain size, the better the cell biocompatibility. The porous scaffold with a grain size of 0.71 μm was immersed in a simulated body fluid for different days to assess the bioactivity. The surface of the scaffold was covered by a bone-like apatite layer, which indicated that the β-TCP scaffold possesses good bioactivity. These discoveries demonstrated the evolution rule between grain microstructure and the properties that give a useful reference for the fabrication of β-TCP bone scaffolds.     

Fatigue behaviour of in situ TiB reinforced β-titanium alloy composite

In the present study, the effect of in situ TiB reinforcements on the fatigue behaviour of β-type Ti-35Nb-5.7Ta-7.2Zr (TNTZ) alloy has been investigated. It has been found that TiB reinforcements have no substantial influence on the yield strength and the fatigue strength of TNTZ alloy. Moreover, the presence of ω precipitates in the β matrix shows higher fatigue limit than the presence of α precipitates.     

Characterization and distribution of mechanically competent mineralized tissue in micropores of β-tricalcium phosphate bone substitutes

1. Download high-res image (357KB)
2. Download full-size image

     

Evaluation of the surface physical properties of β-tricalcium phosphate/silicone rubber, a prospective soft-tissue implant material

Silicone rubber (SR) is one of the most commonly used and effective implant materials for soft-tissue augmentation, but it has been implicated in many adverse reactions. To overcome this drawback, a novel composite β-tricalcium phosphate/silicone rubber (β-TCP/SR) was prepared by compounding a SR matrix with β-TCP. The surface physical properties of β-TCP/SR were evaluated. AFM images showed that β-TCP/SR exhibited greater surface roughness than SR. The XRD and XPS analyses revealed that the addition of β-TCP changed the surface microstructure and charge distribution. FTIR analysis showed that the interaction between β-TCP and SR was weak, which may be due to the tetrahedral structure of PO₄³⁻. These results suggest that the addition of β-TCP in a SR matrix can change the surface microstructure and may improve cytocompatibility, consistent with results from a previous study.     

Subacute systemic toxicity assessment of β-tricalcium phosphate/carboxymethyl-chitin composite implanted in rat femur

The efficacy of a composite of β-tricalcium phosphate particles and carboxymethyl-chitin (β-TCP/CM-chitin) for bone repair has already been established in animal experiments. In the present study, subacute systemic toxicity was evaluated to further assess the biological safety of the implanted composite. β-TCP/CM-chitin (approximately 4 mg/kg and 7 mg/kg in male and female rats, respectively) was implanted for 28 days into penetrating defects (2 mm diameter) made artificially in the shaft of the right femur of rats. Sham operation groups with the defect only were prepared as controls. Haematology, blood chemistry, urinalysis, and the histopathology of 44 organs and tissues were investigated. Body weight measurements and clinical observations were performed daily throughout the study. No subacute systemic toxicity possibly caused by the implantation of β-TCP/CM-chitin was detected. These findings indicate that β-TCP/CM-chitin composite is a highly biocompatible bone substitute, at least with an implantation dosage of < 4–7 mg/kg.     

Design and production of sintered β-tricalcium phosphate 3D scaffolds for bone tissue regeneration

The characteristics of sintered β-tricalcium phosphate (β-TCP) scaffolds produced by 3D printing were studied by means of X-ray diffraction, Scanning Electron Microscopy, Fourier transform infrared spectroscopy, uniaxial compression tests and cytotoxicity tests, using human osteoblast cells.The results reported include details of the β-TCP scaffolds' porosity, density, phase stability, mechanical behavior and cytotoxic profile. Collectively, these properties are fundamental for the future application of these scaffolds as bone substitutes for individualized therapy.     

Fabrication and characterization of polymethylmethacrylate/polysulphone/β-tricalcium phosphate composite for orthopaedic applications

Polymethylmethacrylate (PMMA) and polysulphone (PSu) are biocompatible polymers and are used widely for biomedical applications. In this study, a blend membrane of PMMA/PSu was fabricated using methylene bisacrylamide (MBA) as the blending agent and its properties were studied. Subsequently, a composite membrane consisting of β-tricalcium phosphate (β-TCP) filler dispersed in a polymer matrix of PMMA/PSu was fabricated and evaluated for application as an orthopaedic prosthetic material. Fourier Transform Infrared Spectroscopy spectra of the blend confirmed the interaction of PMMA and PSu with the blending agent MBA. The X-ray diffraction analysis showed that PMMA/PSu membranes exhibited a higher degree of crystallinity when compared with that of the individual polymers. The thermal properties of the samples studied by thermogravimetric analysis showed an increase in the thermal stability of the PMMA/PSu when compared with individual PMMA and PSu membranes. The morphology of the composite samples analysed through SEM showed that the fillers were widely distributed and agglomerated at certain places. The tensile strength of the PMMA/PSu/β-TCP was found to be inferior to that of PMMA/β-TCP although much superior to that of PSu/β-TCP composite membranes. Hardness testing performed using durometer hardness tester (Shore D) showed that the PMMA/PSu/β-TCP samples exhibited higher hardness than the composites having individual PMMA and PSu matrices. Analysis of the optical properties of the polymer membranes suggested good blend formation between PMMA and PSu. The in vitro bioactivity study suggested that the density of the calcium phosphate layer formed on the surface of PMMA/PSu/β-TCP was much higher than that of composites made of either PMMA or PSu matrix. The results of the study showed that the blended composite membranes exhibited favourable properties for biomedical applications such as for orthopaedic prostheses.     

Synthesis of ceramics by sol–gel method in molybdenum,silicon and carbon containing systems. Thermogravimetric studies

The results of investigations on synthesis of ceramics in nanometric systems containing molybdenum compounds, silicon compounds and active carbon have been presented. As precursors ammonium molybdatetetrahydrate ((NH₄)₆Mo₇O₂₄ 4H₂O) and tetraethyl orthosilicate (Si(OC₂H₅)₄) were used. The samples for analysis were obtained by sol–gel method. The course of the process was investigated by thermogravimetric method. The gaseous products were analysed by mass spectrometry. X’ray diffraction (XRD) method was used for identification of solid phases, and morphology of the samples was studied by scanning electron microscopy (SEM). The process proceeded in the following way. At temperature t ⩽ 673 K (NH₄)₆Mo₇O₂₄ 4H₂O decomposes into MoO₃. Then at temperature range of 1046 ⩽ t ⩽ 1065 K MoO₃ is reduced into MoO₂ (or also into Mo). Synthesis of Mo₂C proceeds at temperature in the order of 1273 K. Before the carbothermal reduction of SiO₂ and synthesis of compounds containing molybdenum and silicon we have the Mo₂C–SiO₂-active carbon mixtures. In one stage, at temperature of 1523 K in argon, the synthesis of SiC and the synthesis of compounds containing molybdenum and silicon takes place. In the wide range of initial compositions of the mixtures Mo_4.8Si₃C_0.6 was obtained as the main phase.     

Lovastatin release from polycaprolactone coated β-tricalcium phosphate: Effects of pH,concentration and drug–polymer interactions

The approach of local drug delivery from polymeric coating is currently getting significant attention for both soft and hard tissue engineering applications for sustained and controlled release. The chemistry of the polymer and the drug, and their interactions influence the release kinetics to a great extent. Here, we examine lovastatin release behaviour from polycaprolactone (PCL) coating on β-tricalcium phosphate (β-TCP). Lovastatin was incorporated into biodegradable water insoluble PCL coating. A burst and uncontrolled lovastatin release was observed from bare β-TCP, whereas controlled and sustained release was observed from PCL coating. A higher lovastatin release was observed pH 7.4 as compared to pH 5.0. Effect of PCL concentration on lovastatin release was opposite at pH 7.4 and 5.0. At pH 5.0 lovastatin release was decreased with increasing PCL concentration, whereas release was increased with increasing PCL concentration at pH 7.4. High Ca^2 + ion concentration due to high solubility of β-TCP and degradation of PCL coating were observed at pH 5.0 compared to no detectable Ca^2 + ion release and visible degradation of PCL coating at pH 7.4. The hydrophilic–hydrophobic and hydrophobic–hydrophobic interactions between lovastatin and PCL were found to be the key factors controlling the diffusion dominated release kinetics of lovastatin from PCL coating over dissolution and degradation processes. Understanding the lovastatin release chemistry from PCL will be beneficial for designing drug delivery devices from polymeric coating or scaffolds.     

Structural characterisation and antibacterial activity of PP/TiO2 nanocomposites prepared by an in situ sol–gel method

Polypropylene/titanium dioxide (PP/TiO₂) nanocomposites can be prepared using a novel method based on the hydrolysis–condensation reactions (sol–gel method) of titanium alkoxide inorganic precursors that have been premixed with polypropylene under molten conditions. The resultant nanocomposites were characterised by transmission electronic microscopy (TEM), X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). These techniques showed the formation of the titanium oxi-hydroxide chemical structure (Ti_xO_y(OH)_z) with a diameter of approximately 10 nm in the polymer matrix. Furthermore, a condensation degree of around 17% was determined using XPS analysis. The antibacterial activity was tested according to the JIS Z 2801:2000 standard with Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in the absence of light. Correlations between the microstructure and the chemical composition of PP/TiO₂ nanocomposites and the antibacterial properties of these nanocomposites were discussed. The structure of titanium oxi-hydroxide derivative particles (Ti_xO_y(OH)_z) within the polypropylene matrix has been shown to impact strongly on the antibacterial properties in comparison with the results obtained with a dispersion of anatase titanium dioxide into the PP.     

Nano-hydroxyapatite/β-tricalcium phosphate ceramics scaffolds loaded with cationic liposomal ceftazidime: preparation, release characteristics in vitro and inhibition to Staphylococcus aureus biofilms

In the current study, nano-hydroxyapatite/β-tricalcium phosphate (HA/β-TCP) ceramics scaffolds loaded with cationic liposomal ceftazidime (CLCs) prepared by modified reverse phase evaporation method, the investigations of their release characteristics were performed by the dissolution tests, in vitro anti-biofilm activity of the scaffolds was studied by the determination of bacterial susceptibility with ELISA. The mean particle size, zeta potential, pH and entrapment efficiency of the CLCs studied were 161.5?±?5.37?nm, 60.60?±?5.24 mV, 6.90?±?0.07 and 16.57?±?0.13%, respectively. Electron microscopic images of the samples indicated that the liposomes were well preserved in the scaffolds and that it was the CLCs rather than free ceftazidime releasing from the scaffolds. The minimal inhibitory concentrations (MICs) to Staphylococcus aureus of free ceftazidime and its liposomal formulation were 6.00 μg/mL and the release behaviors of both CLCs and free ceftazidime from scaffolds were based on the dissolution/diffusion processes, Fick's law. These results demonstrated that CLCs could inhibit remarkably the formation of S. aureus biofilm more effectively than free ceftazidime (P?相似文献   

Preparation, characterization and mechanical performance of dense β-TCP ceramics with/without magnesium substitution

Beta-tricalcium phosphate (beta-TCP) powder was prepared by a two-step process: wet precipitation of apatitic tricalcium phosphate [Ca(9)(HPO(4))(PO(4))(5)(OH)] (beta-TCP 'precursor') and calcination of the precursor at 800 degrees C for 3 h to produce beta-TCP. Magnesium-substituted tricalcium phosphate (beta-TCMP) was produced by adding Mg(NO(3))(2) . 6H(2)O into Ca(NO(3))(2) solution as Mg(2+) source before the precipitation step. The transition temperature from beta-TCP to alpha-TCP increases with the increase of Mg(2+) content in beta-TCMP. beta-TCMP with 3 mol.% Mg(2+) has beta-TCP to alpha-TCP transition temperature above 1,300 degrees C. Dense beta-TCMP (3 mol.% Mg(2+)) ceramics ( approximately 99.4% relative density) were produced by pressing the green bodies at 100 MPa and further sintering at 1,250 degrees C for 2 h. The average compressive strength of dense beta-TCP ceramics sintered at 1,100 degrees C is approximately 540 MPa, while that of beta-TCMP (3 mol.% Mg(2+)) ceramics is approximately 430 MPa.