Effects of Sr and Mg dopants on biological and mechanical properties of SiO2–CaO–P2O5 bioactive glass

In the present study, the effects of Sr and Mg were investigated on mechanical and biological properties of 58S bioactive glass (BG). SiO₂-P₂O₅-CaO BG with different contents of Sr and Mg were synthesized via the sol-gel method and immersed in simulated body fluid (SBF) for several days to explore their biocompatibility. Precise analyses of the BG using X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy showed that the Mg-doped BG containing 8 wt % MgO possessed better biocompatibility. It was also found that mechanical properties of the BG could be improved by increasing the amounts of MgO and SrO. Both 5Sr-BG and 8Mg-BG samples did not exhibit any cytotoxicity while showing high alkaline phosphatase activity in comparison with control specimens. However, the Sr-doped BG sample including 5 wt % SrO demonstrated enhanced bioactivity and biocompatibility.     

Studies on novel bioactive glasses and bioactive glass-nano-HAp composites suitable for coating on metallic implants

A series of novel zinc oxide (ZnO) containing bioactive glass compositions in SiO₂-Na₂O-CaO-P₂O₅ system and composite with hydroxyapatite (HAp) nano-particles were developed and applied as coating on Ti-6Al-4V substrates. The bioactive glasses and their composites were also processed to yield dense scaffolds, porous scaffolds and porous bone filler materials. The coating materials and the coatings were characterized and evaluated by different in vitro techniques to establish their superior mechanical properties. The cytotoxicity test of the coating material, porous and dense scaffolds and coated specimens showed non-cytotoxicity, biocompatibility and promising in vitro bioactivity for all tested samples. The dissolution behaviour studies of the bioactive glasses and the composites in simulated body fluid showed promising in vitro release pattern and bioactivity for all tested samples. Addition of nanosized HAp improves mechanical properties of the bioactive glass coating without affecting the in vitro bioactivity.     

Mechanical Properties of Plasma‐Sprayed Mullite‐Reinforced Titania–Bioglass Composite

Bioceramics have been extensively used for various medical applications including hip and knee prostheses, tissue engineering scaffolds, and dental implants. Bioceramics, particularly bioglass, are desired because of their bioactivity but are often limited by their inherent brittleness. To compensate, composites have been formed to obtain unique properties where both bioactivity and mechanical integrity can be achieved. Mullite‐reinforced titania–bioglass (TiO₂–BG) composites were therefore deposited using plasma spraying technique. The microstructure of the coating materials were analyzed for their morphology and microstructure using scanning electron microscopy/energy dispersive spectrometry. Mechanical properties of the coatings were tested using three‐point bend test, indentation test, and pin‐on‐disk wear test to determine their fracture strength, fracture toughness, and wear resistance, respectively. The addition of mullite fibers improved the fracture strength and wear resistance of TiO₂–BG composites while having minimal effect on fracture toughness. After the addition of mullite, failure mode was bimodal, failing intergranularly and by fiber pull‐out. Although mullite fibers have not been particularly used for medical applications, fiber reinforcement has shown efficacy in mechanically reinforcing composites of various medical applications.     

Bioactive glass based scaffolds incorporating gelatin/manganese doped mesoporous bioactive glass nanoparticle coating

We investigated the bioactivity and cytocompatibility of 45S5 bioactive glass (BG) based scaffolds coated with a composite layer formed by gelatin and manganese doped mesoporous bioactive glass nanoparticles (Mn-MBGNs). The scaffolds were prepared using the foam replica method, and they were further coated with Mn-MBGNs/gelatin via dip coating. The synthesized scaffolds were characterized in relation to morphology, porosity, mechanical stability, bioactivity and cell biology behavior using osteoblast-like (MG-63) cells. The scaffolds were highly porous with interconnected porosity, and a suitable pore structure was maintained even after the Mn-MBGNs/gelatin coating. Energy-dispersive X-ray spectroscopy (EDX) confirmed the presence of Mn-MBGNs in the coatings. Moreover, the presence of gelatin was confirmed by Fourier transform infrared spectroscopy (FTIR). The coated scaffolds exhibited in-vitro bioactivity in simulated body fluid comparable to that of uncoated BG scaffolds. Finally, Mn-MBGNs/gelatin coated scaffolds were shown to be non-cytotoxic to MG-63 cells. Hence, the results presented here confirm that the novel Mn containing scaffolds can be considered in the field of biologically active ion releasing scaffolds for bone tissue engineering applications.     

Characterization,in vitro bioactivity and biological studies of sol-gel synthesized SrO substituted 58S bioactive glass

Bioactive glasses (BGs) are considered as a high potential candidate in bone repair and replacement. In the present study, sol–gel derived BGs based on 60% SiO₂-(36%-x) CaO-4%P₂O₅-x SrO (where x = 0, 5 and 10 mol%) quaternary system were synthesized and characterized. The effect of Sr substitutions on bioactivity, proliferation, alkaline phosphatase activity of osteoblast cell line MC3T3-E1 and antibacterial activity were investigated. Dried gels were stabilized at 700 °C to eliminate the nitrates and prevent the crystallization of bioactive glasses. X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy results confirmed the formation of hydroxycarbonate apatite on the BG surfaces. The 3-(4,5dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and alkaline phosphate activity results showed that 5% SrO increased both differentiation and proliferation of MC3T3-E1 cells, while 10% SrO resulted in a decrease in bioactivity. Live/Dead and DAPI/Actin staining exhibited viable cell and the morphology of actin fibers and nuclei of MC3T3 cells treated with BG-0 and BG-5. The result of antibacterial test showed that strontium substituted 58S BG exhibited antibacterial effect against methicillin-resistant Staphylococcus aureus bacteria. Taken together, results suggest that 58S BG with 5 mol% SrO is a good candidate for bone tissue engineering with maximum cell proliferation and ALP activity, good bioactivity and high antibacterial efficiency.     

The effect of bioactive glass nanoparticles on corrosion barrier performance and bioactivity of zinc oxide coatings electrodeposited on Ti6Al4V substrate

Zinc oxide coatings were electrodeposited on Ti6Al4V substrates from a nitrate bath with and without 1 wt% BG nanoparticles at ?1.2 and ?1.4 V_Ag/AgCl, where the former voltage created a spherical morphology, the latter developed a flower-like one. The spherical morphology was modified through the incorporation of BG nanoparticles, where surface roughness, wettability, and adhesion strength of the coating were enhanced. The coatings with spherical morphology also revealed complete barrier property after immersion in PBS solution. However, fully adverse effects were found for the coatings deposited at ?1.4 V_Ag/AgCl. This indicates that morphology is the most important factor determining the properties of ZnO and ZnO-BG coatings. The highest corrosion barrier performance was achieved for the ZnO-BG composite coating with spherical morphology. Although the composite coating with flower-like morphology did not provide complete barrier property at short immersion times, it earned that at longer times due to the plugging supported by the BG nanoparticles. The bioactivity tests in SBF at long times showed that the formation of Ca-P deposits on the surface of the composite coatings was noticeably improved.     

Bioactivity and biodegradability of high temperature sintered 58S ceramics

Bioactive glasses are often considered in bone tissue engineering applications where mechanical strength is essential. As such, bioactive glass scaffolds are often sintered to improve mechanical strength. However, sintering can lead to crystallization, which reduces bioactivity and biodegradability. It has generally been considered that amorphous biomaterials exhibit better bioactivity. However, the in-vitro bioactivity and biodegradability of the sintered 58S made from initial amorphous powder and partially crystalline powder with the same chemical compositions (60SiO₂-36CaO-4P₂O₅ (mol%)) have not been compared before.In this study, 58S bioactive glass (fully amorphous) and glass-ceramic (partially crystallized) powders were synthesized using the sol-gel process, followed by heat-treating at 600 °C for 3 h (calcination). The powders were mixed with carboxymethyl cellulose solution as a binder, shaped in a cylindrical mold, dried, and then sintered at 1100 °C for 5 h. The in-vitro bioactivity and biodegradability of the sintered samples were assessed in simulated body fluid (SBF) for times up to 28 days. The specimens were investigated before and after immersion in SBF using X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR). The In-vitro bioactivity and biodegradability rate of the sintered 58S produced from the glass ceramic powder were higher than that from fully amorphous powder. This study shows that the initial structure after calcination is important and affects the subsequent crystallization during sintering. Therefore, crystallinity and formation of hydroxyapatite after calcination are important controlling mechanisms that can increase the bioactivity and biodegradability rate of sintered 58S.     

Fabrication and characterization of bioactive glass (45S5)/titania biocomposites

Bioactive glass (BG) (45S5) has been used successfully as bone-filling material in orthopedic and dental surgery but its lean mechanical strength limits its applications in load-bearing positions. Approaches to strengthen these materials decreased their bioactivity. In order to realize the optimal matching between mechanical and bioactivity properties, bioactive glass (45S5) was reinforced by introducing titania (TiO₂) in anatase form and treated at 1000 °C to form new bioactive glass/titania biocomposites. The prepared biocomposites were assessed by XRD, FT-IR, mechanical properties and SEM. The results verified that the increase of titania percentage to BG powder enhanced gradually the mechanical data of the prepared biocomposites. SEM and FT-IRRS confirmed the presence of a rich bone-like apatite layer post-immersion on the composite surface. It has been found that the new BG/titania biocomposite materials especially those containing high content of titania have high bioactivity properties and compressive strength values comparable to cortical bone. Therefore, these biocomposite materials are promising for medical applications such as bone substitutes especially in load-bearing sites.     

Microstructural,mechanical properties and strengthening mechanism of DLP produced β-tricalcium phosphate scaffolds by incorporation of MgO/ZnO/58S bioglass

The inherent brittleness of bioceramics restricts their applications in load-bearing implant, although they possess good biocompatibility and bioactivity. ZnO, MgO and 58S bioglass (BG) were incorporated as additives to further improve the mechanical properties and biocompatibility of β-TCP and ZnO/MgO/BG-β-TCP composite scaffolds were manufactured via digital light processing (DLP). The composite with the best comprehensive performance was selected for degradation behavior and biocompatibility evaluation. The effects of different proportions of ZnO/MgO/BG on mechanical strength were analyzed and ZnO0·5/MgO1/BG2-β-TCP (ZMBT) samples exhibited superior mechanical strength. The improvement by 272% and 99% respectively was achieved in fracture toughness and compressive strength with the optimal recipe. The enhancement effect is realized through phase transition, alterative sliding actions and transgranular fracture to effectively prevent the load transfer combining the functions of bioglass and metal oxide. ZMBT scaffolds exhibited a more desirable pH environment and an enhanced ability of apatite-mineralization formation, meanwhile Si⁴⁺, Mg²⁺ and Zn²⁺ were gradually released from scaffolds. Furthermore, in vitro evaluation indicated that ZMBT scaffolds presented not only excellent cell attachment, proliferation, alkaline phosphatase (ALP) activity, but they up-regulated osteogenic gene (ALP, OCN, Runx2). These results suggest that the addition of ZnO/MgO/BG to DLP-printed β-TCP scaffolds offer a smart strategy to fabricate porous scaffolds with conspicuously better biological and physicochemical properties including compressive strength, bioactivity, osteogenesis and osteogenesis-related gene expression. Metal-oxide and BG synergistically enhanced the mechanical and biological properties which make the ZMBT scaffolds a strong candidate for bone repair applications.     

Enhancing In Vitro Bioactivity of Melt‐Derived 45S5 Bioglass® by Comminution in a Stirred Media Mill

45S5 Bioglass^® (45S5 BG) is a frequently applied Type A bioactive material, capable of forming an inherent bond to bone and soft tissue. Currently, applied melt‐derived bioactive glass powders (BG) exhibit particle sizes between a few to several hundred micrometers. Recent studies on nanometer‐sized bioactive glasses (nBGs), produced by bottom‐up methods like sol–gel processing or flame spray pyrolysis, have indicated their great potential for several biomedical applications. In this study, the feasibility of top‐down processing starting from bulk 45S5 BG by wet comminution in a stirred media mill was investigated. The products were assessed by in vitro hydroxycarbonate apatite (HCAp) formation in simulated body fluid, which is a marker for bioactive behavior. The study reveals the paramount influence of the used solvent for a successful top‐down processing: In comparison with the as‐received material bioactivity is lost for powders processed in water, preserved for comminution in ethanol and increased for powders processed using the alcohols n‐butanol, n‐pentanol, and n‐hexanol. It was also found that only for the latter solvents, the chemical composition of the glass is maintained during comminution. Flake‐like, slightly porous particles with specific surface areas of ~25–30 m²/g are obtained. Thus, the presented comminution approach offers a convenient technique to process 45S5 BG with enhanced bioactivity.     

A comparative electrochemical study of LiMn2O4 spinel thin-film and porous laminate

Novel Electrostatic Spray Deposition (ESD) technique was used to fabricate LiMn₂O₄ spinel thin-films. Cyclic voltammograms of both the ESD and porous laminate films show the double peaks in the 4.0 V range characteristic of the LiMn₂O₄ spinel materials. The porous laminates exhibit two semicircles in the impedance spectra while the ESD films show only one single semicircle. The diffusion time constant in the laminate films was typically one order of magnitude larger than that in the ESD thin-films. The apparent lithium-ion chemical diffusion coefficient in LiMn₂O₄ was found to be of the order of 10⁻⁹ cm²/s for both the porous laminate film and the ESD films despite the difference in the diffusion time constants.     

生物活性玻璃多孔材料的制备及性能研究

采用溶胶-凝胶法制备生物活性玻璃58S及77S;通过熔融法制备生物活性玻璃45S5,分别向上述3种生物活性玻璃粉体以及它们的混合物中添加一定比例的造孔剂,通过一定的烧结工艺制成具有不同组成的生物活性多孔材料,利用体外实验方法结合DTA,SEM及FTIR等材料显微结构及性能研究手段分析比较了各种多孔材料的显微结构、表面形貌、抗折强度及生物活性.研究表明:58S和45S5混合制备的多孔材料是一种具有良好生物活性和生物矿化特性的生物材料,可用于制备骨缺损填充材料和骨组织工程支架.     

Comparative study of the corrosion resistance of thermally sprayed ceramic coatings and their bulk ceramic counterparts

A comparative study of the corrosion properties of thermally sprayed ceramic coatings (Al₂O₃, Al₂O₃–TiO₂ with different ratios, mullite, and ZrSiO₄) and their sintered bulk ceramic counterparts was performed. The coatings were deposited on corrosion-resistant steel substrates using atmospheric plasma spraying (APS) and high velocity oxy-fuel (HVOF) spraying processes. The corrosion properties were investigated in 1 N solutions of NaOH and H₂SO₄ at 85 °C, respectively. The coating microstructures and phase compositions, as well as the corrosive environment were shown to have a strong effect on the corrosion resistance of the coatings. Al₂O₃–coatings were more sensitive to these factors than Al₂O₃–TiO₂ coatings were.The corrosion resistance of the bulk ceramics was superior to that of the thermally sprayed coatings. This is mainly because the coatings exhibited specific microstructure and contained amorphous and/or metastable phases not appearing in the bulk ceramics.     

Apatite formation on melt-derived bioactive glass powder based on SiO2-CaO-Na2O-P2O5 system

The higher melting temperature and longer soaking time during conventional glass melting route promoted the search for alternative in developing new bioactive glass (BG) composition with improved in fabrication temperature and melting time. The current project involved fabrication of new BG compositions based on SiO₂-CaO-Na₂O-P₂O₅ system via melt derived route. It was confirmed that all bioactive glass composition can be melted at temperature lower than 1400 °C. Formation of Si-O-Si (tetrahedral) functional group highlighted that silicate based glass was established as detected by Fourier transform infrared spectroscope (FTIR). BG bioactivity was performed by incubating the BG powder in Tris-buffer solution (pH 8) for 7, 14 and 21 days. In vitro test confirmed the apatite formation on the bioactive glass surface upon soaking in Tris-buffer solution with characteristic of carbonate group (C-O) and P-O band noticed from FTIR and present of crystalline peak observed in X-ray diffraction (XRD). Morphology of apatite formation on BG surface was observed using scanning electron microscope (SEM).     

Induction plasma spheroidization of ZrB2-SiC powders for plasma-spray coating

To improve the microstructure and properties of ZrB₂-SiC (ZrB₂-30?vol%SiC, Z7S3) coatings, a facile synthesis route involving induction plasma spheroidization (IPS) has been proposed, and the morphologies, particle size distributions, and phase compositions of the feedstock powders were analysed by scanning electron microscopy and focused ion beam techniques. The obtained results showed that the surfaces of the produced powders contained eutectic-like and granular zones. Owing to the existence of a temperature gradient, the internal microstructure of the IPS-treated powder exhibited a three-layered structure consisting of a ′surface shell′, a ′transition layer′, and a ′porous core′. Additionally, the properties of the IPS-treated samples were compared with those of the spray-dried (SD) powders. The former exhibited good plastic deformation properties, and their single splats contained flattened structures, while the single splats of the SD powder melted only partially retaining some of their original characteristics.     

Fabrication of fibrous poly (ɛ-caprolactone) nano-fibers containing cerium doped-bioglasses nanoparticles encapsulated collagen

Novel nanosized designed ceramic powders, cerium (Ce) doped bioglass (BG) with various doped Ce content, were synthesized by sol–gel method in order to be employed in the development of PCL fibrous scaffold for bone tissue engineering applications. Characterization techniques such as X-ray diffraction analysis, transmission electron microscopy, Fourier transform infrared spectroscopy, and energy-dispersive X-ray spectroscopy were employed to evaluate the developed Ce doped BG powders. The results confirmed successful doping of Ce inside BG structure. 0, 1, 3, and 10 wt% Ce doped 58S BG were successfully encapsulated in the collagen microspheres by water-in-oil emulsion method and the average particle size and hydrodynamic diameter of microspheres were determined using scanning electron microscopy and dynamic light scattering analysis, respectively. Next, 0, 1, 3, and 10 wt% Ce doped 58S BG encapsulated collagen microspheres were loaded inside the Poly(ɛ-caprolactone) fibrous scaffold and their in vitro bioactivity and biocompatibility properties were evaluated. The results of soaking samples in the simulated body fluid showed that all Ce doped 58S BG encapsulated collagen microspheres loaded PCL fibrous scaffold have acceptable bioactivity and apatite formation ability over time. The biocompatibility evaluation of developed scaffolds showed high viability and proliferation of MG63 cells cultured on the surface of 3% Ce doped 58S BG encapsulated collagen microsphere loaded in the PCL fibrous scaffold and its high potential ability for bone tissue engineering applications. These results potentially open new aspects for scaffolds aimed at the regeneration of bone defects.     

Microstructures of La2Ce2O7 coatings produced by plasma spray-physical vapor deposition

La₂Ce₂O₇ (LC) coatings were produced by plasma spray-physical vapor deposition (PS-PVD). To achieve the quasi-columnar microstructure, three spray parameters with different net power, spray distance, and carrier gas flow rate were applied. The relationships between the spray parameters and the microstructures were investigated. It was found that the coatings’ microstructure is more sensitive to the net power and carrier gas flow rate rather than the spray distance. The corresponding phase and chemical compositions of coatings were studied by X-ray diffraction (XRD) and energy dispersive spectrometer (EDS), respectively. The results indicate that the lattice parameters of LC phases have positive correlations with average atomic La/Ce ratios of the coatings. The regional characteristics of the optimized coating were investigated by transmission electron microscope (TEM). Super-lattice diffraction patterns of TEM revealed that the coating is pyrochlore phase. “Particle-interruption” mechanisms in the quasi-columnar coating were proposed and discussed.     

In vitro characterisation of plasma-sprayed apatite/wollastonite glass–ceramic biocoatings on titanium alloys

Some ceramics have the ability to form direct bonds with surrounding tissues when implanted in the body. Among bioactive ceramics, the apatite/wollastonite (A/W) glass–ceramic, containing apatite and wollastonite crystals in the glassy matrix, has been largely studied because of good bioactivity and used in some fields of medicine, especially in orthopaedics and dentistry. However, medical applications of bioceramics are limited to non-load bearing applications because of their poor mechanical properties. In this study, A/W powders, obtained from industrial and high grade quality raw materials, were thermally sprayed by APS (atmospheric plasma spraying) on Ti–6Al–4V substrates, in order to combine the good bioactivity of the bioceramic and the good mechanical strength of the titanium alloy base material. The microstructure and the resulting properties were evaluated depending on processing parameters and post-processing thermal treatments. The morphology and the microstructure of the coatings were observed by SEM and the phase composition was examined by X-ray diffraction. The bioactivity of the coatings was evaluated by soaking the samples in a simulated body fluid (SBF) for 1, 2 and 5 weeks. The bioactive behaviour was then correlated with the thermal treatments and the presence of impurities (in particular Al₂O₃) in the coatings.     

Characterization of bioactive glass-coated carbon nanotubes prepared by solgel process

Due to its excellent bioactivity, bioactive glass (BG) is suitable for use as bone graft substitutes in biomedical applications. In this study, carbon nanotubes (CNT-COOH) served as templates for depositing bioactive glass based on 60SiO₂–36CaO–4P₂O₅ wt.% were synthesized via the solgel process. The BG and BG/CNT-COOH composites were treated at 300, 500, 700, and 900°C; their properties were also examined by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. The experimental results showed that BG/CNT-COOH composites treated at 500 and 700°C were amorphous and contained silicate nanocrystals. By altering precursor concentration, bioactive glass of various thicknesses was successfully solgel coated on CNT-COOH. Immersion of the BG/CNT-COOH composites in simulated body fluid solution and MG-63 cell culture assessment showed the 500°C treated BG/CNT-COOH exhibits excellent bioactivity.     

Deposition of hydroxyapatite coatings by axial plasma spraying: Influence of feedstock characteristics on coating microstructure,phase content and mechanical properties

Axial plasma spray is one of the thermal spray techniques to deposit multifunctional advanced coatings. The present work explores the use of this process to deposit thin, continuous, and adherent Ca₅ (PO₄)₃OH (hydroxyapatite, HAp) coatings and characterize its microstructure, phases, hardness and adhesion strength. Three different suspension-deposited HAp coatings were investigated and compared with powder-deposited HAp coating on a Ti6Al4V substrate. The effect of mean solute particle size and solid-loading in the suspension has been explored on the evolution of microstructure, phase content and mechanical properties of axial suspension plasma sprayed (ASPS) coatings. Phase-characterization has shown retention of hydroxyapatite phase and coating crystallinity in the deposited coatings, whereas the adhesion strength of the HAp coating decreased from ～40 MPa to ～13 MPa when bioglass was added to the feedstock material. The lower solid load content and lower mean solute particle size in the suspension were found to be beneficial in achieving porous, rougher, and well-adhering coatings. This work concludes that ASPS can potentially deposit thin HAp coatings (< 50 μm) with high adhesion strength.