In Vivo Evaluation of 3D-Printed Silica-Based Bioactive Glass Scaffolds for Bone Regeneration

Bioactive glasses are often designed as porous implantable templates in which newly-formed bone can grow in three dimensions (3D). This research work aims to investigate the bone regenerative capability of silicate bioactive glass scaffolds produced by robocasting in comparison with powder and granule-like materials (oxide system: 47.5SiO2-10Na2O-10K2O-10MgO-20CaO-2.5P2O5, mol.%). Morphological and compositional analyses performed by scanning electron microscopy (SEM), combined with energy dispersive spectroscopy (EDS) after the bioactivity studies in a simulated body fluid (SBF) confirmed the apatite-forming ability of the scaffolds, which is key to allowing bone-bonding in vivo. The scaffolds exhibited a clear osteogenic effect upon implantation in rabbit femur and underwent gradual resorption followed by ossification. Full resorption in favor of new bone growth was achieved within 6 months. Osseous defect healing was accompanied by the formation of mature bone with abundant osteocytes and bone marrow cells. These in vivo results support the scaffold’s suitability for application in bone tissue engineering and show promise for potential translation to clinical assessment

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 im-plantable 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) (47.5 B, 47.5 SiO2-10 Na2O-10 K2O-10 MgO-20 CaO-2.5 P2O5 mol.%). Cytocompatibility tests were perfor-med 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 ) al-lowed 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 47.5 B powder was observed after only 3 months in favor of newly formed tissue, thus confirming the high osteostimulatory potential of 47.5 B glass

Foam-Replicated Diopside/Fluorapatite/Wollastonite-Based Glass–Ceramic Scaffolds

Implantation of three-dimensional (3D) bioactive glass-derived porous scaffolds is an effective strategy for promoting bone repair and regeneration in large osseous defect sites. The present study intends to expand the potential of a SiO2–P2O5–CaO–MgO–Na2O–CaF2 glass composition, which has already proven to be successful in regenerating bone in both animals and human patients. Specifically, this research work reports the fabrication of macroporous glass–ceramic scaffolds by the foam replica method, using the abovementioned bioactive glass powders as a parent material. The sinter-crystallization of the glass powder was investigated by hot-stage microscopy, differential thermal analysis, and X-ray diffraction. Scanning electron microscopy was used to investigate the pore–strut architecture of the resultant glass–ceramic scaffolds in which diopside, fluorapatite, and wollastonite crystallized during thermal treatment. Immersion studies in simulated body fluids revealed that the scaffolds have bioactive behavior in vitro; the mechanical properties were also potentially suitable to suggest use in load-bearing bone applications

Influence of external compressive stress on the ionic conductivity of melt-quenched lithium silicate (15Li2O-85SiO2) glass

This paper reports measurements of the electrical resistances of bulk and milled amorphous lithium silicate (15Li2O-85SiO2) under uniaxial load at 200 °C. With imposed load up to 700 MPa, the resistance of the melt-quenched glass increases from 1.56 to 1.95 MΩ cm. This change is reversible, namely after releasing the load the initial electrical resistance is recovered. Milled and compacted glass consists of the bulk and particle contacts resistances. Both of them increase when the external compression up to 200 MPa. For the bulk element, when compression is released, the initial resistance is recovered, whereas the resistance changes within the particles contacts are irreversible

Synthesis and in vitro bioactivity assessment of injectable bioglass - organic pastes for bone tissue repair

The aim of this work was to study the bioactivity of systems based on a clinically tested bioactive glass (BG) particulates (mol%:4.33 Na2O 30.30CaO12.99MgO45.45SiO2 2.60 P2O5 4.33 CaF2) andorganiccarriers.The cohesiveness of injectable bonegraft products is of high relevance when filling complex volume tric boned efects.With this motivation behind, BG particulates with mean sizes within 11 14 μm were mixed indifferent proportions with glycerol(G) and polyethyleneglycol(PEG)as organic carriers and the mixtures were fully injectable exhibiting Newtonian flow behavior

Diopside-Ca-Tschermak clinopyroxene based glass-ceramics processed via sintering and crystallization of glass powder compacts

The suitability of three new glass compositions for producing diopside-Ca-Tschermak clinopyroxene based glass-ceramics (GCs) was investigated. With respect to the formula of diopside, the first investigated composition resulted from the substitution 0.2(Si4+ + Mg2+) 0.4 Al3+, which leads to a composition of 80 mol.% diopside and 20 mol.% Ca-Tschermak. The substitutions in the second compositions were 0.25(Ca2+ + Si4+) 0.25 (Y3+ + B3+) and 0.2(Si4+ + Mg2+) 0.4Al(3+), and in the third composition 0.2Ba(2+) 0.2Ca(2+) and 0.2(Si4+ + Mg2+) 0.2(B3+ + Al3+). The influence of these substitutions on glass crystallization and the properties of the GCs produced between 850 and 1000 degrees C was experimentally investigated. The experimental results showed that the easily cast glasses, after melting at 1580 'C for 1 h, are prone to surface crystallization. Augite is predominantly crystallized, but Ca- and Ba-alummosilicates can also form, according to the substitutions. The stability of the assemblage of the crystalline phases over a wide temperature range (850-1000 degrees C) and prolonged heat treatment (up to 50h) and the properties of the produced M indicate a high potential of these compositions for several functional applications

Synthesis and in vitro bioactivity assessment of injectable bioglass−organic pastes for bone tissue repair

The aim of this work was to study the bioactivity of systems based on a clinically tested bioactive glass (BG) particulates (mol%: 4.33 Na2O−30.30 CaO−12.99 MgO−45.45 SiO2−2.60 P2O5−4.33 CaF2) and organic carriers. The cohesiveness of injectable bone graft products is of high relevance when filling complex volumetric bone defects. With this motivation behind, BG particulates with mean sizes within 11−14 μm were mixed in different proportions with glycerol (G) and polyethylene glycol (PEG) as organic carriers and the mixtures were fully injectable exhibiting Newtonian flow behaviors. The apatite forming ability was investigated using X-ray diffraction and field emission scanning electron microscopy under secondary electron mode after immersion of samples in simulated body fluid (SBF) for time durations varying between 12 h and 7 days. The results obtained revealed that in spite of the good adhesion of glycerol and PEG carriers to glass particles during preparation stage, they did not hinder the exposure of bioactive glass particulates to the direct contact with SBF solution. The results confirmed the excellent bioactivity in vitro for all compositions expressed by high biomineralization rates with the formation of crystalline hydroxyapatite being identified by XRD after 12 h of immersion in SBF solution

Optimization of La2O3-containing diopside based glass-ceramic sealants for fuel cell applications

We report on the optimization of La2O3-containing diopside based glass-ceramics (GCs) for sealant applications in solid oxide fuel cells (SOFC). Seven glass compositions were prepared by modifying the parent glass composition, Ca0.8Ba0.1MgAl0.1La0.1Si1.9O6. First five glasses were prepared by the addition of different amounts of B2O3 in a systematic manner (i.e. 2, 5, 10, 15, 20 wt.%) to the parent glass composition while the remaining two glasses were derived by substituting SrO for BaO in the glasses containing 2 wt.% and 5 wt.% B2O3. Structural and thermal behavior of the glasses was investigated by infrared spectroscopy (FTIR), density measurements, dilatometry and differential thermal analysis (DTA). Liquid-liquid amorphous phase separation was observed in B2O3-containing glasses. Sintering and crystallization behavior, microstructure, and properties of the GCs were investigated under different heat treatment conditions (800 and 850 degrees C: 1-300 h). The GCs with >5 wt.% B2O3 showed an abnormal thermal expansion behavior above 600 degrees C. The chemical interaction behavior of the glasses with SOFC electrolyte and metallic interconnects, has been investigated in air atmosphere at SOFC operating temperature. Thermal shock resistance and gas-tightness of GC sealants in contact with 8YSZ was evaluated in air and water. The total electrical resistance of a model cell comprising Crofer 22 APU and 8YSZ plates joined by a CC sealant has been examined by the impedance spectroscopy. Good matching of thermal expansion coefficients (CTE) and strong, but not reactive, adhesion to electrolyte and interconnect, in conjunction with a low level of electrical conductivity, indicate that the investigated GCs are suitable candidates for further experimentation as SOFC sealants. (C) 2009 Elsevier B.V. All rights reserved