Robocasting of 45S5 bioactive glass scaffolds for bone tissue engineering

Three dimensional scaffolds with controlled pore architecture were prepared from 45S5 Bioglass^® powders by robocasting (direct-writing) using carboxymethyl cellulose (CMC) as the single processing additive. A comprehensive sintering study of the resulting structures was performed within the temperature range 500–1050 °C. Robocast scaffolds with interconnected porosities ranging from 60 to 80% were obtained for a fixed scaffold design. All scaffolds exhibited compressive strengths comparable to that of cancellous bone (2–13 MPa), including those sintered at temperatures below the crystallization temperature of 45S5 bioactive glass. These strength values are substantially higher than any previously reported data for 45S5 Bioglass^® scaffolds and imply that robocasting is the first technique which can be considered suitable for producing vitreous 45S5 scaffolds with a sufficient mechanical integrity for any practical application. Moreover, this process will enable the development of 45S5 Bioglass^® scaffolds with customized external geometry, and optimized pore architecture.     

Fabrication and characterization of ZnO modified bioactive glass nanoparticles

Bioactive glass nanoparticles in the system (SiO₂-CaO-P₂O₅-ZnO) were synthesized following the sol-gel technique. The prepared glass nanoparticles of 1, 3 and 5 wt% of ZnO (coded: GZ1, GZ3 and GZ5, respectively) were characterized by TEM, FTIR, XRF, TGA and DSC. All glass powders had particle sizes less than 100 nm. Textural analysis revealed that for GZ1, GZ3 and GZ5, the average pore diameters, measured by the high-speed gas sorption analyzer, were 15.9, 15.4 and 15.2 nm, respectively, while the average pore diameters measured by the mercury intrusion porosimetry were 47, 50 and 63 nm, respectively. All glass powders were highly porous (75, 76 and 75%) with surface areas of 233, 94 and 118 m²/g for GZ1, GZ3 and GZ5, respectively. All glass powders induced an apatite layer on their surfaces upon immersion in simulated body fluid (SBF) as verified by SEM and TF-XRD.     

Fabrication and characterization of 45S5 bioglass reinforced macroporous calcium silicate bioceramics

Bioactive and degradable macroporous bioceramics play an important role in clinical applications. In the present study, 45S5 bioglass reinforced macroporous calcium silicate ceramics (45BG-reinforced MCSCs) were fabricated. The effect of bioglass additives on compressive strength and open porosity of the samples was investigated, and the bioactivity and degradability of the obtained reinforced samples were also evaluated. The 45S5 bioglass additive was found to be effective to increase the strength of the MCSCs by the liquid-phase sintering mechanism. The optimum amount of bioglass additives was 5 wt.% and the compressive strength of the reinforced samples was approximately 2 times higher as compared to the pure macroporous calcium silicate ceramics (MCSCs). The compressive strength of the reinforced samples with about 50% porosity reached 112.47 MPa, which was similar to those of the cortical bones. After soaking in simulated body fluid (SBF), hydroxycarbonate apatite (HCA) layer was formed on the surface of the 45BG-reinforced MCSCs. Furthermore, the degradation rate of the reinforced samples was just about one-third of those pure MCSCs. Our results indicated that degradable 45BG-reinforced MCSCs possess excellent mechanical strength and bioactivity, and may be used as bioactive and degradable biomaterials for hard tissue prosthetics or bone tissue engineering applications.     

New insights into the crystallization process of sol-gel–derived 45S5 bioactive glass

In this work the influence of thermal treatment conditions on crystallization of a sol-gel-derived 45S5 bioactive glass was evaluated using DSC, XRD, TEM, EDX, and X-ray nanocomputed tomography (nano-CT). Temperature and time of the thermal treatment strongly influence the composition of the crystalline phases. At the onset of the glass transition temperature (600°C), combeite crystallizes as the main phase along with a calcium silicate-phosphate phase, which decomposes into rhenanite from 2 hours of thermal treatment at this temperature. At the crystallization temperature (700°C), combeite remains as the main crystalline phase. Additionally, Na₂Ca₂Si₂O₇ crystalline phase is formed. Our results provide a basic platform for tailoring the crystalline phases by controlling the nucleation and growth of crystalline phases via thermal treatments. Different morphologies (round particles, stacked layers, toothpick-like, and long features) were discerned by TEM as a function of temperature and time of treatment. It is the first time that bioactive glass is investigated by nano-CT at laboratory scale. This novel technique enables the 3D visualization of features in the nanometer range, giving clear information about the volumetric distribution of phases in the sample.     

Fabrication and in vitro characterization of antibacterial magneto-luminescent core-shell bioactive glass nanoparticles

When nanomaterials with antibacterial properties were sent to the infected area, it was predicted that infection and related complications could be prevented. The nanoparticles can be designed to possess magnetic and luminescence (magneto-luminescent) properties to be effectively targeted and localized at the infection foci without dispersing into the body. Simultaneously, the magneto-luminescent characteristic of particles allows visualization and confirmation of localized particles at the desired area. In this regard, there are no studies on the use of antibacterial magneto-luminescent bioactive glass for orthopedic applications and the treatment of orthopedic device-related infections. In this study, antibacterial magneto-luminescent 58S bioactive glasses were synthesized by the modified Stöber using coupled with a layer-by-layer assembly approach to possess core/shell particle morphology. SPION/Bioactive glass nanoparticles had an average size of 50 nm and displayed superparamagnetic behavior. While the saturation magnetization value (σ_s) of the undoped 58S sample was 25.32 emu/g, that of the co-doped sample (2% Eu, 2% Zn) was 21.74 emu/g; this showed that the doping slightly reduced the magnetization value. Europium (Eu) doping of SPION/Bioactive glass nanoparticles induced characteristic red emission originating from Eu emissions belonging to ⁵D₀–⁷F_J (J = 1–4) transitions and the strongest peak was at 612 nm (electric-dipole transition, ⁵D₀–⁷F₂). Color chromaticity coordinates confirmed emission in the red region. XPS spectrum revealed the existence of Eu and Zn dopant elements in 58S bioactive glass. After soaking characteristic peaks at 31.74° and 45.43° belonging to the hexagonal hydroxyapatite phase were detected in the XRD data, confirming the SEM images. 2% Eu doped SPION/Bioactive glass nanoparticles had the highest osteoblast viability up to 7 days in vitro, while doping the samples with 2% zinc did not yield bone cell viability as high as the Eu doped ones. Importantly, Eu doped SPION/Bioactive glass nanoparticles inhibited gram-positive Staphylococcus aureus (S. aureus) and gram-negative Escherichia coli (E. coli) growth up to 48 h in vitro. The results showed that Eu doping of SPION/Bioactive glass nanoparticles increased osteoblast viability and inhibited bacterial growth, while possessing superparamagnetic properties and exhibiting red luminescence.     

Fabrication and characterization of bioactive glass/hydroxyapatite nanocomposite foam by gelcasting method

Bioceramic foams have been applied for drug releasing agents, cell loading, and widely for hard tissue scaffold. The aim of this study was fabrication and characterization of nanostructure bioceramic composite foam (BCF) consisting of hydroxyapatite (HA) and bioactive glass (BG) via gelcasting method for applications in tissue engineering. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analysis techniques were utilized in order to evaluate respectively, phase composition, dimension, morphology, and interconnectivity of pores, and particle size of synthesized HA, BG, and BCF. The results showed that fabrication of the BCF with a particle size in the range 20-42 nm and pore size in the range 100-250 μm was successfully performed. The maximum values of compressive strength and elastic modulus of the BCF were found to be about 1.95 MPa and 204 MPa, respectively, related to a sample sintered at 900 °C for 4 h. The mean values of the true (total) and apparent (interconnected) porosity were calculated in the range 86-91% and 60-71%, respectively. It seems that the measured properties make the BCF a good candidate for tissue engineering applications, preferentially in drug delivery, cell loading, and other nonloading applications.     

Two-step sinter-crystallization of K2O–CaO–P2O5–SiO2 (45S5-K) bioactive glass

Bioactive glasses and glass-ceramics (GCs) effectively regenerate bone tissue, however most GCs show improved mechanical properties. In this work, we developed and tested a rarely studied bioactive glass composition (24.4K₂O-26.9CaO-46.1SiO₂-2.6P₂O₅ mol%, identified as 45S5-K) with different particle sizes and heating rates to obtain a sintered GC that combines good fracture strength, low elastic modulus, and bioactivity. We analyzed the influence of the sintering processing conditions in the elastic modulus, Vickers microhardness, density, and crystal phase formation in the GC. The best GC shows improved properties compared with its parent glass. This glass achieves a good densification degree with a two-step viscous flow sintering approach and the resulting GC shows as high bioactivity as that of the standard 45S5 Bioglass®. Furthermore, the GC elastic modulus (56 GPa) is relatively low, minimizing stress shielding. Therefore, we unveiled the glass sintering behavior with concurrent crystallization of this complex bioactive glass composition and developed a potential GC for bone regeneration.     

Fabrication and characterization of dental mirror product using polylactic acid biocomposites

Polylactic acid biocomposites were prepared by mixing castor oil and talc by melt blending using twin-screw extruder. The amount of talc and castor oil was fixed at 20 and 1?wt%, respectively. The biocomposites were analyzed using Fourier transform infrared spectroscopy, impact strength, bioactivity, cytotoxicity, and soil burial tests. Using biocomposites, mouth mirror product was fabricated for oral dental application using injection molding machine. The impact strength of biocomposites increases by 56% than neat polylactic acid. Bioactivity and cytotoxicity tests of the biocomposites prove that they have no toxicity and the product can be used for oral dental application.     

Fabrication and properties of degradable poly(amino acid)/nano hydroxyapatite bioactive composite

Poly(amino acid)/nano hydroxyapatite (PAA/n-HA) bioactive composite was prepared by in situ melting polymerization. The composition, structure and morphology as well as glass transition temperature (T_g), dynamic mechanical properties of the PAA/n-HA composite were characterized by infrared spectrometer, X-ray diffractometer, X-ray photoelectron spectroscopy, scanning electron microscope, differential scanning calorimeter, and dynamic mechanical analyzer. The results indicated that the n-HA particles were uniformly distributed into PAA matrix and some interactions were found at the interface between PAA and n-HA, and the crystallinity of PAA in the composite decreased with the increase of n-HA content. The T_g and storage modulus of the composite increased with increasing n-HA content, demonstrating that the n-HA content had obvious effects on the crystallization kinetic parameters and thermo properties of the PAA/n-HA composite. In addition, the n-HA amount had evident effects on the degradation of the PAA/n-HA composite in phosphate buffered saline (PBS), and the weight loss ratio of the composite decreased with the increase with n-HA content. The pH value of the medium was stable around 7.40 after the composite immersion into PBS for 8 weeks. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

树枝状介孔生物活性玻璃的制备及其表征

摘要：以十六烷基三甲基溴化铵（CTAB）为模板剂，三乙醇胺（TEA）作为催化剂，正硅酸乙酯（TEOS）为硅源，四水硝酸钙（CaNT）为钙源，磷酸三乙酯（TEP）为磷源，采用溶胶-凝胶法在不同温度下（40 ℃、60 ℃、80 ℃）制备树枝状介孔生物活性玻璃RMBG1、RNBG2、RNBG3，最后采用高温煅烧的方法除去模板。通过场发射扫描电镜(FESEM)、透射电子显微镜(TEM)、全自动快速比表面积与空隙度分析仪（BET）、纳米粒度分析仪(ZS)表征在不同反应温度下树枝状生物活性玻璃的形貌、结构、粒径和稳定性。结果表明：在60 ℃时所制备的树枝状介孔生物活性玻璃RMBG2粒径均一、分散性好、比表面积大，具有三维开放的树枝状孔道的独特结构优势。X射线电子能谱定性分析表明RMBG2中含有Si、Ca、P三种元素，等离子体光谱仪（ICP）表明RMBG2各元素对应的摩尔比大致为Si：Ca：P=84：14：2。RMBG2的比表面积高达821.161 m2g-1,孔径为孔体积为3.184 m3.g-1,可作为高效的药物载体。     

Fabrication, characterization and bioactivity evaluation of calcium pyrophosphate/polymeric biocomposites

The design of the biocomposites offers the opportunity to create grafting materials with excellent bioactivity, resorbability and improved mechanical properties. In this study, we are concerned with the preparation of calcium pyrophosphate (CPP) and its composites with polymeric matrix to enhance these properties. The fabricated biocomposites were characterized by X-ray diffraction (XRD), Fourier transformer infrared spectra (FT-IR), thermogravimetric (TGA) analyses and scanning electron microscope with X-ray elemental analysis (SEM-EDAX). The characterization results confirmed homogeneity, interaction and integration between the CPP filler and polymeric matrix. The mechanical properties of biocomposites had enhanced values compared to the original copolymer matrices and were comparable to those of cancellous bone. In vitro test results via calcium and phosphorous ions measurements, showed that the biocomposites had enhanced ability to accelerate the mineralization of calcium phosphate layer on their surfaces. FT-IR and SEM-EDAX post-immersion confirmed that the CPP/polymeric composites containing chitosan or chitosan–gelatin matrix had ability to induce a bone-like apatite layer onto their surfaces. Finally, a novel CPP/polymeric biocomposites have good bioactivity and suitable mechanical properties; therefore, they could be used in bone grafting and tissue engineering applications in future.     

Synthesis and characterization of spray pyrolyzed mesoporous bioactive glass

Mesoporous bioactive glasses (MBGs) have recently been applied as important bone implant materials due to their high reactive surface areas and superior bioactivities. Various processes have been developed to fabricate MBGs. Among them, the sol–gel process is one of most popular. However, sol–gel has the drawbacks of discontinuous processing and long processing time, making it unsuitable for mass production. This study demonstrates a successful synthesis of MBGs using a spray pyrolysis (SP) method to overcome these problems. The bioactivities of the SP synthesized MBGs are correlated with the main SP processing parameter of calcination temperatures and their structures. Comparisons of the surface areas and bioactivities for the MBG particles prepared from the sol–gel and the SP process are included. Finally, the MBG formation mechanism using SP is proposed.     

Fabrication and characterization of biodegradable poly(lactic acid)/layered silicate nanocomposites

In this study biocompatible/biodegradable poly(lactic acid) (PLA)/layered silicate nanocomposites (PLSNs) were successfully prepared by the intercalation of PLA polymer into organically modified layered silicate through the solution mixing process. Both X‐ray diffraction data and transmission electron microscopy images of PLSNs indicate most of the swellable silicate layers were disorderedly intercalated into the PLA matrix. Mechanical properties of the 0.1 wt% silicate‐containing fabricated nanocomposites performed by dynamic mechanical analysis have significant improvements in the storage modulus when compared to that of neat PLA matrix. Adding more layered silicates into PLA matrix induced a decrease in the mechanical properties of PLSNs, probably due to the presence of a large dimension of porosity in the fabricated nanocomposites. POLYM. ENG. SCI., 45:1615–1621, 2005. © 2005 Society of Plastics Engineers     

Fabrication and characterization of biodegradable poly(propylene carbonate)/wood flour composites

Wood flour reinforced poly(propylene carbonate) (PPC) composites were prepared by melt blending followed by compression molding. The effects of reinforcement on the morphology, static and dynamic mechanical properties, and thermal properties of PPC/wood flour composites were investigated. In terms of mechanical properties, wood flour had the significant effect of improving tensile strength and stiffness. Scanning electron microscopic examination revealed good dispersion of wood flour (especially at lower content) in the PPC matrix. Moreover, experimental results indicated that the wood flour addition led to an obvious improvement in the thermal stability of the composites. This paper demonstrates that the incorporation of low‐cost and biodegradable wood flour into PPC provides a practical way to produce completely biodegradable and cost‐competitive composites with good mechanical properties. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 782–787, 2006     

Preparation and characterization of spray-dried granulated bioactive glass micron spheres

Owing to its superior bioactivity, biocompatibility, and biodegradability, bioactive glass (BG) has been attracting significant attention within biomedical science fields. However, BG powders with variable particle sizes are required targeting different applications, such as dermal fillers. Thus, in this study, granulated BG powders were prepared via the spray drying and granulation method. Size-controlled BG micron sphere with diameters of up to tens of microns can be mass-produced and their phase information, particle morphology, and specific surface area were characterized via X-ray diffraction, scanning electron microscopy, and nitrogen adsorption/desorption isotherm, respectively. In addition, the in vitro bioactivity was evaluated following Kokubo's protocol, and the formation of a hydroxyapatite (HA) layer after immersion into the simulated body fluid was confirmed via energy-dispersive and Fourier transform infrared spectroscopy. The cytotoxicity was examined using a 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay. Finally, the resulting morphologies and corresponding properties are shown, and the related mechanisms are discussed.     

Fabrication, characterization and photocatalytic activity of Gd-doped titania nanoparticles with mesostructure

Gd³⁺-doped mesoporous TiO₂ (m-TiO₂) nanoparticles were synthesized via hydrothermal process by using cetyltrimethylammonium bromide (CTAB) as surfactant-directing agent and pore-forming agent. The resulting products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), diffuse reflection spectra (DRS), and linear sweep voltammetry (LSV) etc. Experimental results indicate that different Gd³⁺-doping levels make great impact on the photocatalytic activity of the obtained m-TiO₂ nanoparticles and the 3.5 at.% Gd³⁺-doped m-TiO₂ nanoparticles calcined at 300 °C exhibit the optimal photoactivity on the degradation of Rhodamine B (RB), which is as nearly two times as that of the commercial photocatalyst P25. The mesoporosity, anatase wall as well as the cooperativity of ‘lattice Gd³⁺’ and ‘free Gd³⁺’ in the m-TiO₂ nanoparticles can be used to explain the observed high photoactivity of the doped m-TiO₂ nanoparticles.     

Fabrication and characterization of poly(vinyl alcohol)/graphene oxide nanofibrous biocomposite scaffolds

Nanofibrous biocomposite scaffolds of poly(vinyl alcohol) (PVA) and graphene oxide (GO) were prepared by using electrospinning method. The microstructure, crystallinity, and morphology of the scaffolds were characterized through X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The mechanical properties were investigated by tensile testing. Moreover, Mouse Osteoblastic Cells (MC3T3‐E1) attachment and proliferation on the nanofibrous scaffolds were investigated by MTT [3‐(4,5‐dimeth‐ylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide] assay, SEM observation and fluorescence staining. XRD and FTIR results verify the presence of GO in the scaffolds. SEM images show the three‐dimensional porous fibrous morphology, and the average diameter of the composite fibers decreases with increasing the content of GO. The mechanical properties of the scaffolds are altered by changing the content of GO as well. The tensile strength and elasticity modulus increase when the content of GO is lower than 1 wt %, but decrease when GO is up to 3 and 5 wt %. MC3T3‐E1 cells attach and grow on the surfaces of the scaffolds, and the adding of GO do not affect the cells' viability. Also, MC3T3‐E1 cells are likely to spread on the PVA/GO composite scaffolds. Above all, these unique features of the PVA/GO nanofibrous scaffolds prepared by electrospinning would open up a wide variety of future applications in bone tissue engineering and drug delivery systems. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Fabrication and characterization of bioactive zirconia-based nanocrystalline glass-ceramics for dental abutment

Zirconia-based ceramics are becoming a popular biomaterial in dental implantology due to their natural silver-white color, excellent mechanical properties, and good biocompatibility. However, zirconia-based ceramics are biologically inert, which limits their ability to integrate with the surrounding human tissues. To solve this problem, the bioactive elements of calcium (Ca) and phosphorus (P) were doped in high-strength ZrO₂–SiO₂ nanocrystalline glass-ceramics (NCGCs) to overcome the biological inertness of ZrO₂-based ceramics. XRD results showed that tetragonal zirconia (t-ZrO₂) and monoclinic zirconia (m-ZrO₂) were the only two crystalline phases after spark plasma sintering. Ca and P dopants acted as destabilizer of t-ZrO₂, enhancing its transformability to m-ZrO₂ during sintering. The amount of t-ZrO₂ exerted significant effects on the average flexural strength of the NCGCs. The NCGC with 45 mol% ZrO₂ were composed of 64.5 vol% t-ZrO₂ and 35.5 vol% m-ZrO₂ after sintering at 1230 °C. And, the average flexural strength and Vickers hardness of the NCGC was 615 MPa and 1049 HV, respectively. In comparison, the NCGC with 65 mol% ZrO₂ were composed of 12.6 vol% t-ZrO₂ and 87.4 vol% m-ZrO₂ after sintering at 1150 °C. The average flexural strength and Vickers hardness of the NCGC was 293 MPa and 839 HV, respectively. Interestingly, the NCGCs exhibited a plastic deformation behavior during flexural strength test, which was different from traditional brittle ceramics. The ion release results demonstrated that Ca²⁺ and Si⁴⁺ ions kept on releasing from the surface of the material. The formation of hydroxyapatite in the in-vitro apatite formation test indicated that the NCGCs had good biological activity. The doped ZrO₂-based NCGCs combined moderate strength and good bioactivity. Hence, the NCGCs show promising potential to be used in sub-gingival regions, such as dental abutments.     

Fabrication and characterization of bioactive calcium silicate microspheres for drug delivery

The calcium silicate (CaSiO₃, CS) microspheres with diameter of 75–100 μm were fabricated by a spray-drying method. A new bone-like apatite layer fully covered the surface of the fabricated CS microspheres after soaking in simulated body fluid (SBF), suggesting the excellent activity of the material in inducing apatite deposition. The ionic extracts of CS microspheres promoted the proliferation of human osteoblast-like cells (MC3T3-E1). In addition, the porous structures of the CS microspheres resulted in favorable drug loading and sustained release property. Our study indicates that the fabricated multifunctional CS microspheres are a promising drug delivery system as an injectable bioactive filling material for bone-regeneration.