P2O5 Mol Research Articles

Growth and Regeneration of Osteochondral Cells in Bioactive Niche: A Promising Approach for Osteochondral Tissue Repair.

Functional repair of osteochondral defects caused due to osteoarthritis still remains the greatest challenge in orthopedic therapy. A prospective clinical strategy would be exploring osteochondral tissue engineering possibilities that promote simultaneous regeneration of the articular cartilage layer as well as the underlying subchondral bone. Incorporating the appropriate cues onto the scaffolds for the regeneration of the two contrasting tissues is therefore a demanding function. In the present study, a polymer-ceramic composite scaffolding material consisting of ternary bioactive glass (67.12 SiO2/28.5 CaO/4.38 P2O5 mol %) incorporated into a semi interpenetrating polymer network of hydrophilic-hydrophobic polymer (poly(vinyl alcohol)-polycaprolactone) matrix is prepared and physicochemically characterized. In vitro bioactivity, bone-bonding ability, and biocompatibility evaluation were performed in comparison with the pristine scaffold. The degree of chondrogenic and osteogenic potential of mesenchymal stem cells in both the scaffolds was evaluated by gene expression studies. Although both the scaffolds favored the differentiation to both cell lineages in their respective medium, a higher expression of bone specific genes found with the composite scaffold suggested that this composite scaffold would serve better for osteal layer and henceforth to promote the integration of the osteochondral construct at the defect site.

Biological Evaluation of a New Sodium-Potassium Silico-Phosphate Glass for Bone Regeneration: In Vitro and In Vivo Studies.

In vitro and in vivo studies are fundamental steps in the characterization of new implantable materials to preliminarily assess their biological response. The present study reports the in vitro and in vivo characterizations of a novel experimental silicate bioactive glass (BG) (47.5B, 47.5SiO2-10Na2O-10K2O-10MgO-20CaO-2.5P2O5 mol.%). Cytocompatibility tests were performed using human mature osteoblasts (U2OS), human mesenchymal stem cells (hMSCs) and human endothelial cells (EA.hy926). The release of the early osteogenic alkaline phosphatase (ALP) marker suggested strong pro-osteogenic properties, as the amount was comparable between hMSCs cultivated onto BG surface and cells cultivated onto polystyrene control. Similarly, real-time PCR revealed that the osteogenic collagen I gene was overexpressed in cells cultivated onto BG surface without biochemical induction. Acute toxicity tests for the determination of the median lethal dose (LD50) allowed classifying the analyzed material as a slightly toxic substance with LD50 = 4522 ± 248 mg/kg. A statistically significant difference in bone formation was observed in vivo through comparing the control (untreated) group and the experimental one, proving a clear osteogenic effect induced by the implantation at the defect site. Complete resorption of 47.5B powder was observed after only 3 months in favor of newly formed tissue, thus confirming the high osteostimulatory potential of 47.5B glass.

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.

Acid catalysed synthesis of bioactive glass by evaporation induced self assembly method

Bioactive glass (BG) with uniform spherical morphology was prepared by EISA (Evaporation Induced Self Assembly) process using non-ionic Pluronic F127 as structure directing agent and phosphoric acid as a source of P2O5 and compared with conventional precursor triethyl phosphate (TEP). EISA method proceeds through ionic interaction mechanism by protonation of surfactant and silicic species. H3PO4 provides H+ and PO43− ions in reaction medium which play critical role in reaction mechanism. Hydrogen ions increase the protonation of H2O and surfactant, while PO43− ions act as bridging molecule between different cations, ensuring incorporation of phosphorus in BG network. TEP participates by proton acceptance mechanism, creating competitive environment. Thus H3PO4 facilitates the formation of BG in presence of non-ionic surfactant Pluronic F127. The prepared glasses were characterized by FTIR, SEM-EDX, TGA-DSC and BET surface analyzer. Uniform spherical morphology, improved dispersity, relatively large surface area and better cells focal attachment were observed for BG-H3PO4, prepared by using H3PO4. SiO2–CaO–P2O5 mol% composition of BG-H3PO4 was (66:24:10) close to the theoretical value (65:25:10), while for BG-TEP the actual ratio was (77:20.5:2.5). The surface reactivity, studied by soaking in simulated body fluid, showed rapid growth of hydroxyapatite with Ca/P ratio 1.67 on BG-H3PO4. The proliferation of MC3T3 cells on BG-H3PO4 was remarkably improved as compared to conventional BG. Thus BG-H3PO4 can be considered for biomedical applications in future especially for drug loading and composite application where homogeneous and uniform structure are of utmost importance.

Effect of sulfur addition and nanocrystallization on the transport properties of lithium–vanadium–phosphate glasses

The glasses defined by the formula 37.5Li2O–25V2O5–37.5P2O5 mol% containing different sulfur (0, 10, 50 and 100 mol%) content were studied before and after nanocrystallization. X-ray diffraction and transmission electron micrograph of the heat treated samples indicated nanocrystals embedded in the glass matrix. The average crystallite size was found between 18 and 37 nm. Sulfur (S) behaved as a reducing agent for redox reaction during preparation of glass and affected the conductivity, i.e., the V4+–V5+ or V3+–V4+ion pairs increased with increasing S content and led to increasing conductivity of glasses. After creation of the nanocrystalline phase, S-free glass–ceramic nanocomposite exhibited improvement in electrical conductivity around three orders of magnitude than initial glass. This great improvement of electrical conductivity is related to increase in a concentration of V4+–V5+or V3+–V4+ ion pairs and also, forming of defective and well-conducting regions along the crystallite/glass interfaces. The decrease in electrical conductivity in the 50S glass–ceramic nanocomposite, which possessed the highest crystallite size, could be related to the increase of grain boundaries scattering because of the increasing crystallite size. The conduction was attributed to non-adiabatic small polaron hopping and mostly determined by hopping carrier mobility.

Effect of sulfur addition on the electrochemical performance of lithium‑vanadium-phosphate glasses as electrodes for energy storage devices

Glasses of the composition 37.5Li2O-25V2O5-37.5P2O5 mol% containing different sulfur (0, 10, 50, 100mol%) content were successfully synthesized and investigated as electrodes for electrochemical devices. Both galvanostatic charge/discharge (GCD) and cyclic voltammetry (CV) were performed to study of electrochemical properties. The results showed that glasses containing sulfur (S) exhibited a high performance, such as specific capacitance, energy density and power density, compared with the S-free glass. These properties increased with increasing of S content. The outstanding electrochemical performance of the glasses containing S can be attributed to the partial substitution of oxygen (O) atoms by S atoms. Since the radius of S ion is higher than O ion, this substitution can significantly enlarge the size of Li-ion transfer pathway. Besides, S ion has better polarization ability than O ion, thus weakens the interaction between Li ions and glass network. Therefore, the addition of S into oxide glasses may be an effective way to improve the performance of electrochemical devices electrodes.

Grain size effects on dynamics of Li-ions in Li3V2(PO4)3 glass-ceramic nanocomposites

Li3V2(PO4)3 glass-ceramic nanocomposites, based on 37.5Li2O-25V2O5-37.5P2O5 mol% glass, were successfully prepared via heat treatment (HT) process. The structure and morphology were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD patterns exhibit the formation of Li3V2(PO4)3 NASICON type with monoclinic structure. The grain sizes were found to be in the range 32–56 nm. The effect of grain size on the dynamics of Li+ ions in these glass-ceramic nanocomposites has been studied in the frequency range of 20 Hz–1 MHz and in the temperature range of 333–373 K and analyzed by using both the conductivity and modulus formalisms. The frequency exponent obtained from the power law decreases with the increase of temperature, suggesting a weaker correlation among the Li+ ions. Scaling of the conductivity spectra has also been performed in order to obtain insight into the relaxation mechanisms. The imaginary modulus spectra are broader than the Debye peak-width, but are asymmetric and distorted toward the high frequency region of the maxima. The electric modulus data have been fitted to the non-exponential Kohlrausch–Williams–Watts (KWW) function and the value of the stretched exponent β is fairly low, suggesting a higher ionic conductivity in the glass and its glass-ceramic nanocomposites. The advantages of these glass-ceramic nanocomposites as cathode materials in Li-ion batteries are shortened diffusion paths for Li+ ions/electrons and higher surface area of contact between cathode and electrolyte.

Electrochemical performance of novel Li3V2(PO4)3 glass-ceramic nanocomposites as electrodes for energy storage devices

The novel Li3V2(PO4)3 glass-ceramic nanocomposites were synthesized and investigated as electrodes for energy storage devices. They were fabricated by heat treatment (HT) of 37.5Li2O–25V2O5–37.5P2O5 mol% glass at 450 °C for different times in the air. XRD, SEM, and electrochemical methods were used to study the effect of HT time on the nanostructure and electrochemical performance for Li3V2(PO4)3 glass-ceramic nanocomposites electrodes. XRD patterns showed forming Li3V2(PO4)3 NASICON type with monoclinic structure. The crystalline sizes were found to be in the range of 32–56 nm. SEM morphologies exhibited non-uniform grains and changed with variation of HT time. The electrochemical performance of Li3V2(PO4)3 glass-ceramic nanocomposites was investigated by using galvanostatic charge/discharge methods, cyclic voltammetry, and electrochemical impedance spectroscopy in 1 M H2SO4 aqueous electrolyte. The glass-ceramic nanocomposites annealed for 4 h, which had a lower crystalline size, exhibited the best electrochemical performance with a specific capacity of 116.4 F g−1 at 0.5 A g−1. Small crystalline size supported the lithium ion mobility in the electrode by decreasing the ion diffusion pathway. Therefore, the Li3V2(PO4)3 glass-ceramic nanocomposites can be promising candidates for large-scale industrial applications in high-performance energy storage devices.

The antioxidant properties of Ce-containing bioactive glass nanoparticles explained by Molecular Dynamics simulations

AbstractMolecular dynamics simulations of two glass nanoparticles with composition 25Na2O·25CaO 50SiO2 mol% (Ce-K NP) and 46.1SiO2·24.4Na2O·26.9CaO· 2.6P2O5 mol.% (Ce-BG NP) doped with 3.6 mol% of CeO2 have been carried out in order to explain the enhanced antioxidant properties of the former glass with respect to the latter.The present models show that the different catalase mimetic activity of the two NPs is related to the Ce3+/Ce4+ ratio exposed at their surface. In fact, this ratio is about 3.5 and 13 in the bulk and at the surface of the Ce-BG NP, and 1.0 and 2.1 in the bulk and at the surface of the Ce-K NPs, respectively. Since both oxidation states are necessary for the catalysis of the dismutation reaction of hydrogen peroxides, NPs with a very high Ce3+/Ce4+ ratio possess poorer antioxidant properties.Moreover, our simulations reveal that the already low silicate connectivity found in the bulk glasses examined here is further reduced on the nanoparticle surface, whereas the Na+/Ca2+ ratio rapidly increases. Sodium, calcium and cerium sites in proximity of the surface are found to be under-coordinated, prone to quickly react with water present in physiological environments, thus accelerating the glass biodegradation

Influence of Synthesis Parameters on the Structure, Pore Morphology and Bioactivity of a New Mesoporous Glass

The main objective of the present work was to investigate the effect of surfactant type and synthesis temperature on the structure, porosity and the bioactivity of 92S6 (92% SiO2, 6% CaO, and 2% P2O5 mol %) mesoporous sol-gel glasses. The aim was to provide a basis for controlling the bioactive behavior of the different 92S6 samples used for tissue regeneration and for biomedical engineering in order to obtain sufficient performances by controlling the porosity of the glass. In this paper, a series of mesoporous bioactive glasses were synthesized using three different surfactants (C10H20BrN, C19H42BrN, C22H48BrN) at different aging temperatures (20°C, 40°C and 60°C). The surfactant was removed by calcination, which was carried out by increasing the temperature to 650°C for 6 h. A comparison among these synthesized glasses was conducted and the research emphasis was placed on the synthesis temperature and the surfactant type dependence on the textural properties and particularly porosity that were ultimately responsible for glass bioactivity.

Nucleation and crystallization kinetics of rapidly quenched lithium pyrophosphate glass

66.7Li2O–33.3P2O5 mol% glass prepared by twin-roller rapid quenching has been chosen to investigate the nucleation and crystallization kinetics using differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and high temperature X-ray diffraction (XRD) as the experimental tools. Such studies assume importance in designing materials for solid state ionic devices. The glass exhibits a nucleation rate of 3.1 × 1018 m− 3 s− 1 at a typical temperature of 583 K and crystal growth rate of 2.1 × 10− 2 nm s− 1 at 643 K. Non-isothermal DSC studies reveal that the glass undergoes bulk crystallization with an activation energy of 114 kJ mol− 1. The crystallized phase is identified as lithium pyrophosphate (Li4P2O7). Crystallization kinetic studies reveal that Li4P2O7 crystallizes three dimensionally with increasing number of nuclei. Interestingly, lithium metaphosphate (LiPO3) appears as a secondary phase in the glass matrix, however, the final glass ceramic product obtained after prolonged heat treatment of the glass is single phase Li4P2O7. The secondary phase also grows three dimensionally with an activation energy of 365 kJ mol− 1, but with constant number of nuclei in contrast to Li4P2O7. The high nucleation and growth rate with lower activation energy for crystallization of Li4P2O7 underscore that the glass is extremely prone to nucleation and crystallization.

DFT Modeling of 45S5 and 77S Soda-Lime Phospho-Silicate Glass Surfaces: Clues on Different Bioactivity Mechanism

The reactivity of bioglasses, which is related to the dissolution of cations and orthosilicate groups in the physiological fluid, strongly depends on the key structural features present at the glass surfaces. On the basis of the composition and the synthetic routes employed to make the glass, surfaces with very different characteristics and thus presenting different mechanisms of dissolution can be observed. In this paper, the surface structures of two very different bioglass compositions, namely 45S5 (46.1 SiO2, 24.4 Na2O, 26.9 CaO, and 2.6 P2O5 mol %) and 77S (80.0 SiO2, 16.0 CaO, and 4.0 P2O5 mol %), have been investigated by means of periodic DFT calculations based on a PBE functional and localized Gaussian basis set as encoded in the CRYSTAL code. Our calculations show that the two glass surfaces differ by the relative amount of key structural sites such as NBOs, exposed ions, orthosilicate units, and small rings. We have demonstrated how the number of these sites affects the surface stability and reactivity (bioactivity).

Mesoporous bioactive glass coatings on stainless steel for enhanced cell activity, cytoskeletal organization and AsMg immobilization

Mesoporous bioactive glass (MBG) coatings with SiO2:CaO:P2O5 mol ratio of 100:0:0, 80:15:5 and 70:25:5 and a tunable pore size and pore structure were prepared on a stainless steel plate by spin-coating sol solutions containing a triblock copolymer and the inorganic precursors. The calcium content in the MBG coatings affected the mesoporous structure. With the increase in calcium content, the crystallinity of the MBG coatings increased and thus the Brunauer–Emmett–Teller (BET) surface area and pore volume decreased. The MBG coatings were evaluated on the basis of protein adsorption, cell attachment, cell proliferation, cell differentiation, cytoskeletal organization and L-ascorbic acid phosphate magnesium salt n-hydrate (AsMg) immobilization for their potential in improving implant-bone integration. The results showed that the osteoblast MC3T3-E1 cells were stimulated by the mesoporous structure and chemical composition of the MBG coatings, with enhanced cell attachment, proliferation, differentiation and better developed cytoskeleton. Moreover, AsMg was successfully immobilized on the MBG coatings by using an AsMg-containing supersaturated calcium phosphate solution. The AsMg immobilized on the MBG coatings was not denatured and showed high activity enhancing the fibroblast NIH3T3 proliferation in vitro. An appropriate range of pore size and a preferred alignment of the mesochannels of the MBG coatings on stainless steel are promising to improve the implant-bone integration.

B3LYP Simulation of the Full Vibrational Spectrum of 45S5 Bioactive Silicate Glass Compared tov-Silica

The IR spectrum of the Bioglass 45S5 (of composition 46.1 SiO2, 24.4 Na2O, 26.9 CaO, and 2.6 P2O5 mol %) has been simulated by means of periodic ab initio B3LYP calculations. The initial glass structure unit cell envisaging 78 atoms was generated through a melt quench process by means of classical molecular dynamics simulations. The molecular mechanics optimized unit cell has then been fully reoptimized (both unit-cell parameters and internal coordinates) at B3LYP level in a periodic approach using Gaussian basis sets of double-ζ quality by means of the CRYSTAL06 code. Although long-range structural properties cannot be modeled by using this ab initio approach because of the intrinsic amorphous nature of the glass, the quantum mechanical simulation proved to be extremely effective in predicting and analyzing the vibrational features of this biomaterial. The effect of modifiers Na and Ca cations on the network dynamics has been assessed by comparing the 45S5 vibrational spectrum with that of amorphous v-SiO2, both simulated at the B3LYP level. A detailed assignment of each spectral peak to the corresponding vibrational mode of the two glasses has been addressed and the role of cation modifiers on the vibrational features has been analyzed in greater details. This may be useful to support further IR and Raman investigations of the bulk structure of these materials.

Effect of Other Oxides on Solubility and Bioactivity in Calcium Phosphate Glasses

The development of phosphate glasses for use in orthopaedic implants has attracted much interest because their chemical and physical properties make them suitable for use as bone-bonding materials. We prepared various compositions of CaO-P2O5-MO or CaO-P2O5-M2O (M: K, Li, Na, Mg, Zn) glasses to measure ion release, solubility and bioactivity. The compositions with (Ca,M)/P molar ratio 0.6 were fixed P2O5 mol% content at 45.45 mol%, and varying MO or M2O mol% at 10, 20 and 30 mol%. Ca2+ ion release properties were investigated in 0.1M potassium acetate with pH 6 at 37oC by immersing 50 mg of powder into 100 ml of acidic buffer solution. The highest and lowest extent of released Ca2+ ion was observed for composition with 10 mol% of K2O and 30 mol% of MgO, respectively. The weight loss in distilled water at 37oC was measured. Solubility increased with decreasing CaO content, but decreased with increasing MgO content. Bioactivity in the simulated body fluid at 37oC was measured.