Behaviour of MG-63 osteoblast-like cells on wood-based biomorphic SiC ceramics coated with bioactive glass

The aim of this study was to test the in vitro cytotoxicity of wood-based biomorphic Silicon Carbide (SiC) ceramics coated with bioactive glass, using MG-63 human osteoblast-like cells, with a view to their application in bone implantology. To better understand the scope of this study, it should be taken into account that biomorphic SiC ceramics have only recently been developed and this innovative product has important properties such as interconnected porosity, high strength and toughness, and easy shaping. In the solvent extraction test, all the extracts had almost no effect on cellular activity even at 100% concentration, and cells incubated in the bioactive glass-coated SiC ceramics extracts showed a proliferation rate similar to that of the Thermanox control. There were no significant differences when the cellular attachment response of the cells on the wood-based biomorphic SiC ceramics, uncoated or coated with bioactive glass, was compared to the one exhibited by reference materials like Ti6Al4V and bulk bioactive glass. This fact looks very promising for biomedical applications.     

熔盐法制备含钴氯磷灰石及其抗氧化性能和细胞相容性研究

生物活性陶瓷骨修复材料虽然具有优异的成骨性能, 但缺乏抗氧化应激的能力, 妨碍骨修复进程。本研究以β相磷酸三钙(β-TCP)粉体为原料, 采用LiCl-KCl熔盐体系, 以六水合氯化钴(CoCl₂·6H₂O)为钴源, 利用熔盐法制备出含钴氯磷灰石(Co-MS-TCP)。通过Co-MS-TCP粉体清除过氧化氢(H₂O₂)分析了含钴氯磷灰石的抗氧化能力; 通过细胞活性、胞内活性氧(ROS)含量变化评价了材料的细胞相容性和细胞水平抗氧化性能。结果表明, 熔盐处理β-TCP粉体能够制备含钴氯磷灰石, 钴含量随CoCl₂·6H₂O加入量增加而增大; H₂O₂清除能力随氯磷灰石中钴含量的增加而增强, 6 h内对H₂O₂的清除率可达90%以上。细胞实验证实, 含钴氯磷灰石具有良好的细胞相容性和抗氧化性能, 1.5 mg·mL^-1加3% Co盐的MS-TCP (3%Co-MS-TCP)即可保证软骨细胞和骨髓间充质干细胞存活率大于85%, 并且3% Co-MS-TCP可有效清除H₂O₂, 使得细胞内ROS含量显著降低。因此, 通过熔盐法制备含钴生物活性陶瓷是实现抗氧化应激的一种有效途径, 这也为开发催化活性高、生物相容好的功能化生物活性陶瓷提供了新的策略。     

Synthesis and characterization of nanostructured CaSiO3 biomaterial

Here we report a successful preparation of nanostructured calcium silicate by wet chemical approach. The synthesized sample was characterized by various physico-chemical methods. Thermal stability was investigated using thermo-gravimetric and differential thermal analysis (TG-DTA). Structural characterization of the sample was carried out by the X-ray diffraction technique (XRD) which confirmed its single phase hexagonal structure. Transmission electron microscopy (TEM) was used to study the nanostructure of the ceramics while homogeneous grain distribution was revealed by scanning electron microscopy studies (SEM). The elemental analysis data obtained from energy dispersive X-ray spectroscopy (EDAX) were in close agreement with the starting composition used for the synthesis. Superhydrophilic nature of CaSiO₃ was investigated at room temperature by sessile drop technique. Effect of porous nanosized CaSiO₃ on early adhesion and proliferation of human bone marrow mesenchymal stem cells (BMMSCs) and cord blood mesenchymal stem (CBMSCs) cells was measured in vitro. MTT cytotoxicity test and cell adhesion test showed that the material had good biocompatibility and promoted cell viability and cell proliferation. It has been stated that the cell viability and proliferation are significantly affected by time and concentration of CaSiO₃. These findings indicate that the CaSiO₃ ceramics has good biocompatibility and that it is promising as a biomaterial.     

Biogenic silica–metal phosphate (metal = Ca,Fe or Zn) nanocomposites: fabrication from rice husk and their biomedical applications

In this investigation, we fabricated biogenic silica–metal phosphate nanocomposites (BSMPNs) using rice husk from agricultural waste as a silica source. The morphologies and dimensions of the synthesized nanocomposites were analyzed using transmission electron microscopy (TEM). Fourier-transform infrared spectroscopy results confirmed that metal phosphate crystals were formed with the biogenic silica. The X-ray diffraction patterns of the BSMPNs showed the presence of hexagonal calcium and iron phosphate and orthorhombic zinc phosphate nanoparticles embedded in the matrix of biogenic silica. The TEM images suggested that spherical and irregularly shaped tiny particles with dimensions between 50 and 100 nm were dispersed in the biogenic silica. The in vitro biological properties of the nanocomposites were studied by a cell viability assay and through the analysis of microscopy images. The cytocompatibility studies proved that the material was nontoxic and had excellent biocompatibility with human mesenchymal stem cells. The synthetic route for these nanocomposites is interesting and may be helpful in the fabrication of various novel silica-based composites and in the exploitation of eco-friendly agricultural biomass. Our results revealed that these nanocomposites can be used in bone tissue engineering.     

Evaluation of the efficiency of TiB2 and TiC as protective coatings for SiC monofilament in titanium-based composites

The vigorous interfacial reactions in SiC/Ti-6Al-4V composites at elevated temperatures lead to the deterioration of the mechanical properties of the composites. TiB₂ and TiC were selected as potential protective coatings for SiC fibres in titanium-based composites. These coatings were deposited on to fibres by the chemical vapour deposition technique. Comparisons and evaluations have been made of the effectiveness of these ceramics as protective coatings for SiC fibres by incorporating the coated fibres into a Ti-6Al-4V matrix using the diffusion bonding method. Emphasis has been placed on the chemical compatibility of the candidate coating with SiC and Ti-6Al-4V by examining the interfaces of the fibre/coating/matrix using microscopic methods and chemical analysis. A stoichiometric TiB₂ coating was found to be stable with SiC and has proved an effective barrier to prevent the SiC fibre from reacting with the Ti-6Al-4V. The TiC coating showed no apparent reaction with a titanium-alloy matrix under the conditions studied, but was found to react with the SiC fibre substrate.     

Effect of lecithin content blend with poly (L-lactic acid) on viability and proliferation of mesenchymal stem cells

Lecithin constitutes a natural mixture of phospholipids and neutral lipids and plays critical roles in cellular membrane structure and cellular signaling. In this study, lecithin was blended with poly (L-lactic acid) (PLLA) for modifying the surface of PLLA because it might obtain appropriate hydrophilicity and biocompatibility. The modified PLLA films were manufactured using conventional solvent-casting technique. The hydrophilicity clearly increased with an increase of lecithin content in the polymer blends, as determined by measuring the water contact angle (WCA). The cytocompatibility and any potential cytotoxic effects were studied over 7 days by seeding mesenchymal stem cells (MSCs) on the films of PLLA containing 0–15% lecithin (wt.%), in comparison with tissue culture plates (TCPs). Cell viability and proliferation were assessed using WST-8, lactate dehydrogenase (LDH) and cell morphology was studied by toluidine blue and propidium iodide staining. This results obtained above suggested that 5%lecithin-containing PLLA films could possess the optimal hydrophilicity, higher adhesion and proliferation of MSCs for a prolonged period and did not demonstrate any significant toxic effects to cells. The study showed that the hydrophilicity and biocompatibility of the modified PLLA were markedly improved by directly introducing lecithin into the polymer without the use of multiple synthetic steps. The information obtained should be useful for future research in vascular tissue engineering (VTE).     

Comparative investigation of the biocompatibility of various silicon nitride ceramic qualities in vitro

There is a controversy about the biocompatibility of silicon nitride ceramics contained in the literature, which appears to be related to a factor of the individual chemical composition of different qualities of silicon nitride ceramics and of the different surface properties. This study attempts to investigate the cytotoxicity of different qualities of industrial silicon nitride ceramics applying an L929-cell culture model in a direct contact assay combined with a cell viability assessment. Five different qualities of industrial standard silicon nitride ceramics were chosen for in vitro testing. The chemical composition was determined by EDS analysis. Different biomedically approved aluminium oxide qualities, a titanium alloy, glass and polyvinylchloride (PVC) served as control materials. L929 mice fibroblasts were incubated directly on the materials for 24 h, stained with bisbenzimide and propidium iodine for double fluorochromasia viability testing, and evaluated by inversion-fluorescence microscopy to control cell morphology, viability and cell counts compared to empty well values. Scanning electron microscopy was applied to additionally investigate cell morphology. There was no observation of cytotoxic effects on the silicon nitride ceramic samples; moreover cell morphology remained the same as on aluminium oxide and titanium. Viability testing revealed the presence of avital cells exclusively on PVC, which served as a negative control. Cell counts on all polished surfaces showed significantly higher numbers, whereas some rough surface samples showed significantly lower numbers. We conclude that silicon nitride ceramics show no cytotoxic effects and should be considered for biomedical application owing to its favourable physiochemical properties, especially its superior resistance to mechanical stress, which would be useful for compression loaded conditions. Polished surfaces would appear to promote advanced biocompatibility.     

Designing the fiber volume ratio in SiC fiber-reinforced SiC ceramic composites under Hertzian stress

Finite element method (FEM) analysis and experimental studies are undertaken on the design of the fiber volume ratio in silicon carbide (SiC) fiber-reinforced SiC composites under indentation contact stresses. Boron nitride (BN)/Pyrocarbon (PyC) are selected as the coating materials for the SiC fiber. Various SiC matrix/coating/fiber/coating/matrix structures are modeled by introducing a woven fiber layer in the SiC matrix. Especially, this study attempts to find the optimum fiber volume ratio in SiC fiber-reinforced SiC ceramics under Hertzian stress. The analysis is performed by changing the fiber type, fiber volume ratio, coating material, number of coating layers, and stacking sequence of the coating layers. The variation in the stress for composites in relation to the fiber volume ratio in the contact axial or radial direction is also analyzed. The same structures are fabricated experimentally by a hot process, and the mechanical behaviors regarding the load–displacement are evaluated using the Hertzian indentation method. Various SiC matrix/coating/fiber/coating/matrix structures are fabricated, and mechanical characterization is performed by changing the coating layer, according to the introduction (or omission) of the coating layer, and the number of woven fiber mats. The results show that the damage mode changes from Hertzian stress to flexural stress as the fiber volume ratio increases in composites because of the decreased matrix volume fraction, which intensifies the radial crack damage. The result significantly indicates that the optimum fiber volume ratio in SiC fiber-reinforced SiC ceramics should be designed for inhibiting the flexural stress.     

Defects in ceramic matrix composites and their impact on elastic properties

Defects created during the manufacture of an oxide/oxide and two non-oxide (SiC/SiNC and MI SiC/SiC) ceramic matrix composites (CMCs) were categorized as follows: (1) Intra-yarn defects such as dry fibers, (2) Inter-yarn defects such as those at crossover points, matrix voids, shrinkage cracks and interlaminar separation, and (3) Architectural defects such as layer misalignment. Their impact on elastic properties was analytically investigated using a stiffness averaging approach considering the defects to have volumetric and directional influences. In-plane tensile and shear moduli as well as the through-thickness compressive modulus were experimentally evaluated. Results of analytical model were around 7% on average from the mean value of the experimental data. It was observed that interlaminar separation drastically reduced the through-thickness modulus by about 63% for the SiC/SiNC, 40% for the MI SiC/SiC and around 32% for the oxide/oxide composites. Shrinkage cracks in oxide/oxide composite reduced the in-plane tensile and shear moduli by 14% and 8.8%, respectively.     

Development and cytotoxicity evaluation of SiAlONs ceramics

SiAlONs are ceramics with high potential as biomaterials due to their chemical stability, associated with suitable mechanical properties, such as high fracture toughness and fracture resistance. The objective of this work was to investigate the mechanical properties and the cytotoxicity of these ceramic materials. Three different compositions were prepared, using silicon nitride, aluminum nitride and a rare earth oxide mixture as starting powders, yielding Si₃N₄–SiAlON composites or pure SiAlON ceramics, after hot-pressing at 1750 °C, for 30 min. The sintered samples were characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). Furthermore, hardness and fracture toughness were determined using the Vicker's indentation method. The biological compatibility was evaluated by in vitro cytotoxicity tests. Ceramic with elevated hardness, ranging between 17 and 21 GPa, and high fracture toughness of 5 to 6 MPa m^1/2 were obtained. Since a nontoxic behavior was observed in the cytotoxicity tests, it may be assumed that SiAlON-based ceramics are viable materials for clinical applications.     

Biomimetic synthesis of cellular SiC based ceramics from plant precursor

A novel biomimetic approach in designing and fabricating engineering ceramic materials has gained much interest in recent times. Following this approach, synthesis has been made of dense Si-SiC duplex ceramic composites and highly porous SiC ceramics in the image of the morphological features inherent in the caudex stem of a local monocotyledonous plant. The process route involves making of a carbonaceous biopreform and its subsequent reaction with an infiltrating silicon melt to yield the biomorphic Si-SiC ceramic composites with flexural strength and Young’s modulus of 264 MPa and 247 Gpa, respectively and loss in weight of only ∼9% during oxidative heating up to 1200°C in flowing air. The Si-SiC composites were transformed into porous (49 vol.%) SiC ceramics with complete preservation of microcellular anatomy of the parent plant, by depleting residual silicon phase in channel pores through reaction with carbon. SiC based materials so derived can be used in structural applications and in designing high temperature filters and catalyst supports.     

An in vitro study of electrically active hydroxyapatite-barium titanate ceramics using Saos-2 cells

Electrically active ceramics are of interest as bone graft substitute materials. This study investigated the ferroelectric properties of hydroxyapatite-barium titanate (HABT) composites and the behaviour of osteoblast-like cells seeded on their surfaces. A piezoelectric coefficient (d₃₃) of 57.8 pCN⁻¹ was observed in HABT discs prepared for cell culture. The attachment, proliferation, viability, morphology and metabolic activity of cells cultured on unpoled HABT were comparable to those observed on commercially available hydroxyapatite at all time points. No indication of the cytotoxicity of HABT was detected. At one day after seeding, cell attachment was modified on both the positive and negative surfaces of poled HABT. After longer incubations, all parameters observed were comparable on poled and unpoled ceramics. The results indicate that HABT ceramics are biocompatible in the short term in vitro and that further investigation of cell responses to these materials under mechanical load and at longer incubation times is warranted.     

rGO/SiC复合材料的制备与性能研究

碳化硅(SiC)陶瓷具有优异的力学性能, 但是其断裂韧性相对较低。石墨烯的引入有望解决碳化硅陶瓷的断裂韧性较低的问题。本研究采用热压烧结工艺, 制备了具有不同还原-氧化石墨烯(rGO)掺入量的SiC复合材料。经过2050℃保温、40 MPa保压1 h后, 所制备的复合材料均烧结致密。对复合材料中rGO的掺入量、微观结构和力学性能的相互关系进行分析和讨论。加入4wt%的rGO后, 复合材料的三点抗弯强度达到564 MPa, 比热压SiC陶瓷提高了6%; 断裂韧性达到4.02 MPa•m^1/2, 比热压SiC陶瓷提高了54%。加入6wt%的rGO后, 复合材料的三点抗弯强度达到420 MPa, 略低于热压SiC陶瓷, 但其断裂韧性达到4.56 MPa•m^1/2, 比热压SiC陶瓷提高了75%。裂纹扩展微观结果显示, 主要增韧机理有裂纹偏转、裂纹桥连和rGO片的拔出。     

Cytocompatibility evaluation in cell-culture systems of chemically crosslinked chitosan/PVA hydrogels

In the present study we report the preparation, characterization and cytocompatibility of novel polymeric systems based on blends of chitosan and poly(vinyl alcohol) (PVA) and chemically crosslinked by glutaraldehyde for biomedical applications. The structure of the hydrogels was characterized through Fourier Transform Infrared spectroscopy (FTIR) and their swelling behavior was investigated as preliminary in vitro test. Bioactivity, cytotoxicity and cell viability were assessed via MTT assay with 2 cell cultures and cell spreading-adhesion analysis. Moreover, the cell viability and potential biocompatibility were assessed by the secretion of nitric oxide by activated macrophages with gamma interferon (IFN-γ) cytokine and lipopolysaccharide (LPS). It was found that by increasing the chitosan to PVA ratio the swelling behavior was significantly altered. In addition, all tested hydrogels have clearly presented adequate cell viability, non-toxicity and suitable properties which can be tailored for prospective use in tissue engineering.     

新型基片材料——C/SiC复合材料

阐述了目前常用的3大类基片材料,即塑料基、金属基和陶瓷基材料,比较了3类材料的性能,得出了陶瓷基材料是综合性能较好的基片材料的结论,并比较了目前陶瓷基片材料中的Al2O3、AlN、BeO、SiC的性能,认为SiC作为基片材料具有良好的发展前景;针对单相SiC陶瓷固有脆性导致难以大尺寸成型的问题,提出了使用C/SiC复合材料制备基片材料的可能性,并综述了C/SiC复合材料的制备工艺,比较了3种工艺(PIP、CVI、LSI)所制备的材料的性能,认为液相渗硅(LSI)C/SiC复合材料制备大尺寸封装基片材料是未来最具前景的发展方向。     

The preparation and mechanical properties of carbon–carbon/lithium–aluminum–silicate composite joints

Silica carbide modified carbon cloth laminated C–C composites have been successfully joined to lithium–aluminum–silicate (LAS) glass–ceramics using magnesium–aluminum–silicate (MAS) glass–ceramics as interlayer by vacuum hot-press technique. The microstructure, mechanical properties and fracture mechanism of C–C/LAS composite joints were investigated. SiC coating modified the wettability between C–C composites and LAS glass–ceramics. Three continuous and homogenous interfaces (i.e. C–C/SiC, SiC/MAS and MAS/LAS) were formed by element interdiffusions and chemical reactions, which lead to a smooth transition from C–C composites to LAS glass–ceramics. The C–C/LAS joints have superior flexural property with a quasi-ductile behavior. The average flexural strength of C–C/LAS joints can be up to 140.26 MPa and 160.02 MPa at 25 °C and 800 °C, respectively. The average shear strength of C–C/LAS joints achieves 21.01 MPa and the joints are apt to fracture along the SiC/MAS interface. The high retention of mechanical properties at 800 °C makes the joints to be potentially used in a broad temperature range as structural components.     

Zirconia toughened alumina ceramic foams for potential bone graft applications: fabrication,bioactivation, and cellular responses

Zirconia toughened alumina (ZTA) has been regarded as the next generation orthopedic graft material due to its excellent mechanical properties and biocompatibility. Porous ZTA ceramics with good interconnectivity can potentially be used as bone grafts for load-bearing applications. In this work, three-dimensional (3D) interconnected porous ZTA ceramics were fabricated using a direct foaming method with egg white protein as binder and foaming agent. The results showed that the porous ZTA ceramics possessed a bimodal pore size distribution. Their mechanical properties were comparable to those of cancellous bone. Due to the bio-inertness of alumina and zirconia ceramics, surface bioactivation of the ZTA foams was carried out in order to improve their bioactivity. A simple NaOH soaking method was employed to change the surface chemistry of ZTA through hydroxylation. Treated samples were tested by conducting osteoblast-like cell culture in vitro. Improvement on cells response was observed and the strength of porous ZTA has not been deteriorated after the NaOH treatment. The porous 'bioactivated' ZTA ceramics produced here could be potentially used as non-degradable bone grafts for load-bearing applications.     

Effect of testosterone incorporation on cell proliferation and differentiation for polymer–bioceramic composites

In the current study, we characterized the polycaprolactone (PCL), poly(lactic acid-co-glycolic acid) (PLGA), and biphasic calcium phosphate (BCP) composites coated with testosterone propionate (T) using Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (XRD). Osteoblastic cells were seeded with PCL/BCP, PCL/BCP/T, PLGA/PCL/BCP and PLGA/PCL/BCP/T scaffolds, and cell viability, proliferation, differentiation and adhesion were analyzed. The results of physic-chemical experiments showed no displacements or suppression of bands in the FTIR spectra of scaffolds. The XRD patterns of the scaffolds showed an amorphous profile. The osteoblastic cells viability and proliferation increased in the presence of composites with testosterone over 72?h, and were significantly greater when PLGA/PCL/BCP/T scaffold was tested against PCL/BCP/T. Furthermore alkaline phosphatase production was significantly greater in the same group. In conclusion, the PLGA/PCL/BCP scaffold with testosterone could be a promising option for bone tissue applications due to its biocompatibility and its stimulatory effect on cell proliferation.     

Ti诱导反应熔体无压浸渗法制备(W,Ti)C/Fe复合材料

研究了一种Ti诱导反应熔体无压浸渗制备复合材料的方法: 通过凝胶注模成型工艺, 以蔗糖为造孔剂制备了多孔Ti-WC陶瓷骨架预制体, 真空状态下, 在1370℃以Fe-Cr-C合金熔体无压浸渗该预制体, 经过原位反应制备了(W,Ti)C/Fe复合材料。利用SEM-EDS、 XRD对复合材料的组织结构、 元素组成及相组成进行了测试和分析。采用旋转圆盘式摩擦试验机以SiC砂浆为磨料研究了(W,Ti)C/Fe复合材料的耐磨性。结果表明: 在浸渗过程中骨架中的Ti元素的溶解析出与C元素的原位反应促进了浸渗过程的进行, 在1370℃保温1 h, 金属液即渗透整个多孔骨架, 并且在浸渗过程中仍然维持着骨架的形状, 浸渗过程中Ti-C-WC原位反应生成具有芯-壳结构的中间富Ti、 边缘富W的(W,Ti)C增强相。摩擦磨损实验结果表明, (W,Ti)C/Fe复合材料具有优异的抗磨粒磨损性能, 其耐磨性优于工业用耐磨铸铁。     

FABRICATION OF SiCp-AI COMPOSITE MATERIALS

Liquid phase fabrication methods for aluminum matrix composites reinforced with SiC whiskers, or SiC particles have been investigated and the mechanical properties of fabricated composites have been evaluated. Three kinds of liquid phase fabrication methods; hot extrusion, hot pressing and pressure infiltration, were studied. Commercial SiC whiskers and SiC powders of alpha type and beta type were used as the reinforcements for an aluminum matrix. Among the fabrication methods investigated, the best results were achieved by the pressure infiltration. The mechanical properties and the wear resistance of the fabricated composites were measured. The SiC whisker reinforced aluminum matrix composites have high strength, so that they can be used as high specific strength materials. The SiC particulate reinforced aluminum matrix composites are not strong as the SiC whisker reinforced composites. However, the SiC particulate reinforced aluminum matrix composites have a good potential for use as wear resistant material. The hardening effect of beta type particles on the aluminum matrix was larger than that of alpha type particles.