Microwave energy-assisted formation of bioactive CaO–MgO–SiO<Subscript>2</Subscript> ternary glass from bio-wastes

Regeneration technique is extensively being sought after as a means of achieving bone repair without adverse immunological response. Silicate-based bioactive glasses containing Mg are gaining increasing attention for their biocompatibility. The current work has been focused on designing a facile and economic route using bio-wastes for synthesizing bioactive glasses in the CaO–MgO–SiO₂ system. Rice husk ash (RHA) obtained from burning rice husk was used as silica source, while Ca was extracted from eggshells for preparing the glass through a modified sol–gel approach. The gel formed was irradiated in microwave before sintering at 950^°C for 3 h. Thereafter, bioactivity test was conducted on the samples in simulated body fluid (SBF) at physiological conditions for a maximum of 14 days. Characterization of samples were performed before and after immersion in SBF to evaluate the composition, morphology and phases present in the glass using energy-dispersive X-ray analysis, scanning electron microscopy and X-ray diffraction. Apatite formation was confirmed using Fourier transform infrared spectroscopy. Results obtained showed the presence of diopside, wollastonite and pseudo-wollastonite as major bioactive phases. Hydroxyapatite formed on the material within 3 days in SBF, indicating good bioactivity.     

Assessment of in vitro bioactivity of SiO2-BaO-ZnO-B2O3-Al2O3 glasses: An optico-analytical approach

Bioactive glasses are an important subclass of biomaterials. The bioactivity of a glass depends on its initial constituents and their respective amounts. In the present investigation, five barium-zinc-borosilicate glass samples have been studied by varying Al₂O₃ mol% to check their bioactivity. The optical and bioactive properties of pristine glasses are compared with glasses soaked in Simulated Body Fluid (SBF) for 10 and 30 days using pH measurement, Ultraviolet–visible-Near Infrared-red (UV–vis–NIR), Fourier Transform Infra-Red (FTIR) spectroscopy, X-ray diffraction and Scanning Electron Microscopy (SEM) techniques. Although calcium is not present as an initial constituent in glass composition, yet bioactivity is observed in some glass samples after dipping them in SBF.     

Polymer/bioactive glass nanocomposites for biomedical applications: A review

Nanoscale bioactive glasses have been gaining attention due to their reported superior osteoconductivity when compared to conventional (micron-sized) bioactive glass materials. The combination of bioactive glass nanoparticles or nanofibers with polymeric systems enables the production of nanocomposites with potential to be used in a series of orthopedic applications, including scaffolds for tissue engineering and regenerative medicine. This review presents the state of art of the preparation of nanoscale bioactive glasses and corresponding composites with biocompatible polymers. The recent developments in the preparation methods of nano-sized bioactive glasses are reviewed, covering sol–gel routes, microemulsion techniques, gas phase synthesis method (flame spray synthesis), laser spinning, and electro-spinning. Then, examples of the preparation and properties of nanocomposites based on such inorganic bionanomaterials are presented, obtained using various polymer matrices, including polyesters such as poly(hydroxybutyrate), poly(lactic acid) and poly(caprolactone), and natural-based polymers such as polysaccharides (starch, chitin, chitosan) or proteins (silk fibroin, collagen). The physico-chemical, mechanical, and biological advantages of incorporating nanoscale bioactive glasses in such biodegradable nanocomposites are discussed and the possibilities to expand the use of these materials in other nanotechnology concepts aimed to be used in different biomedical applications are also highlighted.     

The effect of Fe contents on the local structure and crystallization behavior of SiO<Subscript>2</Subscript>–CaO–P<Subscript>2</Subscript>O<Subscript>5</Subscript>–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> glasses

The glass and glass ceramics containing SiO₂–CaO–Fe₂O₃–P₂O₅ were prepared by sol–gel method. The influence of the Fe contents on the crystallization and local structure of the glass and glass ceramics was systematically investigated. The crystal structure of the glass ceramics was identified by XRD characterization. Hematite phase can be precipitated from the glass matrix in all glass ceramics with various Fe contents, and the crystallographic parameters of hematite were determined by XRD Rietveld refinement. The crystallization kinetics of the glasses was investigated in detail. Relative low activation energies were obtained at low Fe contents. The local structure evolution of the glass and glass ceramics has been studied in-depth by means of FTIR and Mössbauer spectroscopy. Fe element is present both as network former and network modifier which significantly influenced the crystallization activation energies of the glasses. The results of this work may be of great significance for the material design and practical applications of bioactive magnetic glass ceramics for hyperthermia.     

Preparation and characterization of Li<Subscript>2</Subscript>O–CaO–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–P<Subscript>2</Subscript>O<Subscript>5</Subscript>–SiO<Subscript>2</Subscript> glasses as bioactive material

The aim of the present investigation was to study the role of Al₂O₃ in the Li₂O–CaO–P₂O₅–SiO₂ bioactive glass for improving the bioactivity and other physico-mechanical properties of glass. A comparative study on structural and physico-mechanical properties and bioactivity of glasses were reported. The structural properties of glasses were investigated by X-ray diffraction, Fourier transform infrared spectrometry, scanning electron microscopy and the bioactivity of the glasses was evaluated by in vitro test in simulated body fluid (SBF). Density, compressive strength, Vickers hardness and ultrasonic wave velocity of glass samples were measured to investigate physical and mechanical properties. Results indicated that partial molar replacement of Li₂O by Al₂O₃ resulted in a significant increase in mechanical properties of glasses. In vitro studies of samples in SBF had shown that the pH of the solution increased after immersion of samples during the initial stage and then after reaching maxima it decreased with the increase in the immersion time. In vitro test in SBF indicated that the addition of Al₂O₃ up to 1.5 mol% resulted in an increase in bioactivity where as further addition of Al₂O₃ caused a decrease in bioactivity of the samples. The biocompatibility of these bioactive glass samples was studied using human osteoblast (MG-63) cell lines. The results obtained suggested that Li₂O–CaO–Al₂O₃–P₂O₅–SiO₂-based bioactive glasses containing alumina would be potential materials for biomedical applications.     

Gamma ray interaction with copper-doped sodium phosphate glasses

Copper-doped sodium phosphate glasses of various compositions and with varying copper contents were prepared. UV-visible and infrared spectroscopic studies were measured before and after successive gamma irradiation. Experimental results indicate that copper ions occupy different local sites depending on the host glass composition and concentration of copper ions. The changes in UV, visible and infrared spectral data, are discussed in relation to the structural evolution caused by the change in composition and states of copper ions. Copper ions have been found to show a shielding behavior toward the effects of progressive gamma irradiation causing a retardation of the growth of the induced defects caused by irradiation.     

Sol–gel-derived manganese-releasing bioactive glass as a therapeutic approach for bone tissue engineering

Sol–gel processing allows the production of bioactive glasses (BG) with flexible compositions and the incorporation of different metallic ions with therapeutic benefits into the glass network. Manganese is among several previously studied therapeutically beneficial ions and has been shown to favour osteogenic differentiation, in addition to playing an important role in cell adhesion. The incorporation of Mn into bioactive glasses for tissue engineering has been previously conducted using the conventional melting route, whereas the sol–gel route has not yet been explored. Sol–gel technology has great versatility, allowing the preparation of BG with various compositions, sizes, morphologies and a large surface area that could provide improved cellular responses and enhanced bioactivity when compared to melt-derived glasses. In this context, this work developed new compositions of sol–gel bioactive glasses (on the SiO₂–P₂O₅–CaO–MnO system) and explored the effects of incorporating MnO on the structure, texture, in vitro bioactivity and cytocompatibility of these materials. Our results show that Mn-containing bioactive glasses present an amorphous character, high surface area and mesoporous structure. The formation of a hydroxycarbonate apatite (HCA) layer after immersion in simulated body fluid (SBF) revealed the high bioactivity of the glasses. Ion release evaluation indicated that the Si, Ca, P and Mn release levels could be adjusted within therapeutic limits, and cytotoxic analysis demonstrated that the ionic products of all samples generated a cell-friendly environment. Therefore, Mn incorporation into the bioactive glass network appears to be a potential strategy to develop superior materials with sustained ion release for tissue engineering.     

多种重离子辐照对硼硅酸盐玻璃机械性能的影响

研究辐照导致硼硅酸盐玻璃机械性能的影响, 对高放废物的长期安全处置具有重要的意义。本工作采用0.3 MeV的P离子、4 MeV的Kr离子、5 MeV的Xe离子以及8 MeV的Au离子分别辐照硼硅酸盐玻璃, 利用纳米压痕技术表征了辐照前后样品的硬度和模量。结果表明: 硼硅酸盐玻璃的硬度和模量在一定范围内会随着辐照剂量的增大而减小, 辐照达到0.1 dpa时硬度和模量变化趋于饱和, 此时硬度下降了35%, 模量下降了18%; 而且不同种类的离子辐照对硼硅酸盐玻璃的硬度和模量造成的变化趋势基本相同。使用掠入射X射线衍射仪对样品晶态结构进行了分析, 发现辐照后硼硅酸盐玻璃仍保持非晶状态。利用Raman光谱对辐照后样品的微观结构的变化进行了表征, 发现辐照会导致玻璃网络结构发生改变, 玻璃的聚合度下降, 无序度增加。本工作还证明了离子辐照导致玻璃机械性能变化的主要因素是离子在样品中的核能量沉积导致玻璃结构的改变。     

The effect of Sr concentration on bioactivity and biocompatibility of sol–gel derived glasses based on CaO–SrO–SiO2–P2O5 quaternary system

In the present study, sol–gel derived glasses based on CaO–SrO–SiO₂–P₂O₅ system were prepared and the effect of Sr concentration on in vitro bioactivity and cellular properties of the glasses were investigated. SrO was substituted for CaO in the glass formula up to 10 mol% and in vitro bioactivity of the samples was evaluated by soaking them in simulated body fluid followed by structural characterization using XRD, FTIR and SEM techniques. The effects of various glass compositions on proliferation and differentiation of osteoblastic cells were also evaluated. The results showed that the substitution of Sr for Ca in the glass composition retarded formation of apatite layer onto the glass surfaces. Morphologies of the apatite layers were also different in which abundance of the crystals decreased with increasing Sr concentration. The bioactive glasses did not exert cytotoxic effect on the cells, however the proliferation and alkaline phosphatase activity of the cells on the samples containing low doses of Sr were higher than those of control and the samples with high dose of Sr. Glass specimen with 5 mol% of Sr exhibited appropriate bioactivity with optimal cell proliferation and ALP activity.     

Gamma-ray shielding properties of zinc oxide soda lime silica glasses

In the present work, the gamma ray shielding properties of zinc oxide soda lime silica, (ZnO)_x(SLS)_1?x glasses with 0 ≥ x ≥ 50 wt% have been investigated. By using WinXCom computer software, the mass attenuation coefficient (µ/ρ) and half value layer (HVL) for total photon interaction in the energy range of 1 keV–100 GeV were calculated. Furthermore and by Geometric Progression method exposure buildup factor values were calculated for incident photon energy 0.015–15 MeV up to penetration depths of 40 mfp (mean free path). The addition of zinc oxide (ZnO) into soda lime silica (SLS) glass resulted in an increase the mass attenuation coefficient and decreases both the half value layer and exposure buildup factor. The obtained results of the selected glass series have been compared, in terms of mass attenuation coefficient, half value layer and exposure buildup factor with some common shielding materials. The shielding effectiveness of the selected glasses is found comparable to that of common ones; which indicates that the SLS glasses with suitable ZnO content may be developed as gamma ray shielding materials.     

Synthesis,structural, thermal and optical properties of TeO2–Bi2O3–GeO2–Li2O glasses

In this study, synthesis and characterization of novel quaternary tellurite glass system TeO₂–Bi₂O₃–GeO₂–Li₂O is presented. The compositions include TeO₂ and GeO₂ as glass formers while different proportion of Bi₂O₃ and Li₂O act as network modifiers. Differential thermal analysis, X-ray diffraction, scanning electron microscopy energy dispersive X-ray spectroscopy, laser ablation inductively coupled plasma mass spectrometry, UV–Vis and Raman spectroscopy are applied to study the structural, thermal and optical properties of the studied glasses. Obtained glasses possess a relatively low glass transition temperature (around 300 °C) if compared to other tellurite glasses, show good thermal transparency in the visible and near infra-red (from 2.4 to 0.4 μm) and can double the frequency of laser light from its original wavelength of 1064 nm to its second-harmonic at 532 nm (i.e. second harmonic generation).     

Second Harmonic Generation induced by optical poling in new TeO2-Tl2O-ZnO glasses

New tellurite glasses with a large glass forming domain were elaborated within the TeO₂-Tl₂O-ZnO ternary system. The evolution of the glass transition (T_g) and onset crystallization (T₀) temperatures for such tellurite glasses was studied, in particular, as a function of the Tl₂O addition. A decrease of both T_g and T₀ temperatures was observed; the former being more affected. Structural modifications induced by the addition of the modifiers were studied by Raman spectroscopy. For a fixed ZnO concentration, the increase in the Tl₂O content leads to a destruction of the glass framework, characterized by the transformation of TeO₄ disphenoids into isolated TeO₃²⁻ trigonal pyramid-like ortho-groups. For a fixed Tl₂O concentration, the ZnO addition induces similar effects on the glass structure. The optical transmission of the ((80 − x)TeO₂-xTl₂O-20ZnO) (x = 10, 20 and 30 mol%) glasses was measured in the 300-2000 nm range. Their good transparency was evidenced and a clear reduction of the optical band-gap was noticed with the increase in the Tl₂O content. Finally, Second Harmonic Generation was unambiguously detected for each glass composition. The second order non-linearity amplitude is found to be increasing as a function of the Tl₂O concentration, in the tested range.     

Effect of nanocrystallization on the electrical conductivity enhancement and Mössbauer hyperfine parameters of iron based glasses

Selected glasses of Fe₂O₃-PbO₂-Bi₂O₃ system have been transformed into nanomaterials by annealing at temperature close to crystallization temperature (T_c) for 1 h. The effects of the annealing of the present samples on its structural and electrical properties were studied by Mössbauer spectroscopy, transmission electron micrograph (TEM), differential scanning calorimeter (DSC) and dc conductivity (σ). Mössbauer spectroscopy was used in order to determine the states of iron and its hyperfine structure. The effect of nanocrystalization on the Mössbauer hyperfine parameters did not exhibit significant modifications in present glasses. However, in case of glass ceramic nanocrystals show a distinct decrease in the quadrupole splitting (Δ) is observed, reflecting an evident decrease in the distortion of structural units like FeO₄ units. In general, the Mössbauer parameters of the nano-crystalline phase exhibit tendency to increase with PbO₂ content. TEM of as-quenched glasses confirm the homogeneous and essentially featureless morphology. TEM of the corresponding glass ceramic nanocrystals indicates nanocrystals embedded in the glassy matrix with average particle size of about 32 nm. The crystallization temperature (T_c) was observed to decrease with PbO₂ content. The glass ceramic nanocrystals obtained by annealing at T_c exhibit improvement of electrical conductivity up to four orders of magnitude than the starting glasses. This considerable improvement of electrical conductivity after nanocrystallization is attributed to formation of defective, well-conducting phases “easy conduction paths” along the glass-crystallites interfaces.     

Effect of buffer layer on solution deposited ZnO films

ZnO films were prepared by solution deposition method on various substrates: bare glass, TiO₂-buffer-coated glass, ITO glass and ZnO-buffer-coated glass. PEG addition was used to further investigate the effect of the patterned ZnO buffer on the morphology of the films. The structural morphology was investigated by using X-ray diffraction, scanning electron microscopy, field emission scanning electron microscopy analysis methods. The nature of the substrate was found to have effect on the morphology and crystal structure of the resultant films. All the films deposited on various substrates were c-oriented and the highest intensity of (002) diffraction peak appeared in the samples deposited on ZnO buffer. Addition of PEG to the buffer precursor affected the size distribution of ZnO grains on buffer layer, resulting in composite films with nano- and microcrystals which dispersed in each other. The homogeneous nucleation and heterogeneous nucleation on the two sides of the substrates were discussed based on the film morphology.     

Influence of strontium for calcium substitution on the glass–ceramic network and biomimetic behavior in the ternary system SiO<Subscript>2</Subscript>–CaO–MgO

Strontium (Sr) enhances bone formation both in vitro and in vivo, while it reduces bone resorption. Thus, Sr incorporation in bioactive glass–ceramic scaffolds for bone tissue regeneration could further enhance osteogenesis. The aim of this work was the synthesis, characterization and investigation of the apatite-forming ability in inorganic environment of two sol–gel-derived bioactive Sr-containing glass–ceramic materials with 5 and 10% of SrO. The thermal properties of the synthesized materials were studied using differential thermal analysis (TG–DTA). The apatite-forming ability test was conducted in SBF for various immersion times for both thermally treated and untreated samples. The characterization of the samples before and after immersion in SBF was performed with Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD) and scanning electron microscopy with associated energy-dispersive spectroscopy. FTIR spectra revealed that all synthesized glass–ceramic materials presented the characteristic bands of silicate glasses, while XRD identified various crystalline phases, mostly calcium silicates. Strontium is present in the form of strontium silicate in both as-received and thermally treated specimens, and Sr-diopside in the thermally treated specimens. The apatite-forming ability of the glass–ceramic materials was confirmed by the formation of a hydroxyapatite layer after 3 and 5 days of immersion in SBF on the surface of the untreated and thermally treated samples, respectively. The apatite layer, also, became thicker as the immersion time increased.     

Effect of the molecular weight of poly(ethylene glycol) on the plasticization of green sheets composed of ultrafine BaTiO3 particles and poly(vinyl butyral)

The effect of the molecular weight (MW) of poly(ethylene glycol) (PEG) on the plasticization of poly(vinyl butyral) (PVB) binder in green BaTiO₃ sheets prepared with PEG with MW values of 400 and 1530 was investigated. The MW of PEG had a profound effect on the rheological properties of the suspension as well as the physical properties of the green sheet. The suspension viscosity decreased with decreasing MW of PEG for shear rates above 4 s⁻¹. PEG 400 gave rise to a higher degree of plasticization of the green sheet than PEG 1530. This was due to the reduction in hydrogen bonding between the vinyl alcohol units in the PVB binder in the green BaTiO₃ sheet, as identified by FT-IR spectroscopy. As the MW of the PEG decreased, the green BaTiO₃ sheets exhibited a lower glass transition temperature, and a noticeably more ductile behavior. These results indicate that the green sheets became more flexible due to a higher plasticizing effect. However, laminated green BaTiO₃ sheets prepared with PEG 1530 showed delamination defects that were observed at a cut surface, which arose because of the low plasticization. This suggests that PEG 1530 has limited utilization as a plasticizer for the BaTiO₃/PVB binder system.     

Synthesis,characterization and evaluation of bioactivity and antibacterial activity of quinary glass system (SiO2–CaO–P2O5–MgO–ZnO): In vitro study

Bioactive glasses in the systems SiO₂–CaO–P₂O₅–MgO (BGZn0) and SiO₂–CaO–P₂O₅–MgO–ZnO (BGZn5), were prepared by sol–gel method and then characterized. Surface reactivity was studied in simulated body fluid (SBF) to determine the effect of zinc (Zn) addition as a trace element. The effect of Zn addition to the glass matrix on the formation of apatite layer on the glass surface was investigated through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT–IR) and scanning electron microscopy (SEM). Also, inductively coupled plasma–optical emission spectroscopy (ICP–sOES) was used to determine the concentrations of released ions in SBF solution after different time intervals in SBF solution. The antibacterial activity of Zn containing glass against Pseudomonas aeruginosa was measured by the halo zone test. The presence of Zn in glass composition improved chemical durability, slowed down the formation rate of Ca–P layer and decreased the size of crystalline apatite particles. Zn containing glass exhibited an excellent antibacterial activity against P. aeruginosa which could demonstrate its ability to treat bone infection.     

Preparation and Characterization of Eu<Superscript>3+</Superscript>-Doped Transparent Oxyfluoride Glasses

A process has been proposed for the preparation of oxyfluoride glasses based on the SiO₂–B₂O₃–Bi₂O₃–ZnO–CaF₂ system at various ratios of batch components, and transparent glasses have been obtained at a temperature below 1000°C. According to X-ray diffraction data, all of the glasses are X-ray amorphous. The surface morphology of the glasses has been examined and their glass transition temperatures have been determined. Their local structure has been studied by IR spectroscopy and it has been shown that, independent of composition, the glasses contain complex polyborate anions formed by [BO₃] and [BO₄] groups. Bismuth is incorporated into the glass network to form Bi–O–Si bonds and [BiO₆] network-formers.     

激活基因的玻璃

三十年前发现，生物玻璃能与骨形成骨键结合。这种特殊的材料已经有超过15年的临床应用，并在数以千计的成功病例。研究表明，骨的键合及骨再生和修复（骨形成作用）涉及玻璃表面的离子快速交换反应、生物活性表面反应层的成核和生长、由可溶硅和钙组成的临界浓度的离子溶解产物的释放。生物活性玻璃的分子生物学机理研究表明，它的生物活性响应看起来是由基因控制的。具有骨促进作用的A类生物活性玻璃通过直接对那些调节诱发细胞周期开始和进程的基因的直接控制，从而加强了其骨形成和促进作用。不能够形成新骨的细胞从细胞总体中被消除，这一特征是当成骨细胞在生物惰性材料或者B类生物活性材料培养时所没有的。骨前细胞细胞周期的基因调控生物学结果是成骨细胞的快速繁殖和分裂，这也导致了骨的迅速再生。对生物活性玻璃基因基础的理解，可以为设计新一代活化基因的玻璃材料，以及新一代活化基因的组织工程用生物降解支架提供重要的依据。如果我们能用玻璃激活基因，可以肯定，有一天我们就能用玻璃来控制基因。     

基于PEG修饰的ZnO量子点光学特性研究

采用溶胶-凝胶法制备了ZnO量子点, 并采用有机高分子试剂PEG(聚乙二醇, M_w=2000)对其表面进行修饰。借助X射线衍射分析、傅立叶红外光谱、光致发光谱和透射显微镜等测试方法, 研究了PEG表面修饰对ZnO量子点结构和光学性能的影响规律。研究表明, 混合加入的PEG聚合物能够成功地包覆在ZnO量子点表面, 但没有改变量子点的晶体结构, 经PEG表面修饰后的ZnO量子点尺寸变小, 稳定性增强, 分散更均匀。同时经PEG修饰的ZnO量子点在400~500 nm波长区域缺陷态发射峰明显减弱, 表明采用PEG来改善ZnO量子点表面缺陷结构具有良好效果。