In vivo evaluation of cerium,gallium and vanadium-doped borate-based bioactive glass scaffolds using rat subcutaneous implantation model

The main objective of this study was to evaluate the cerium, gallium and vanadium-containing bioactive borate glass scaffolds for soft tissue applications and determine the potential toxicity of these scaffolds on the adjacent tissues. The effects of the cerium, gallium and vanadium substitution on the soft tissue ingrowth and angiogenesis in porous borate based bioactive glass scaffolds were investigated using rat subcutaneous implantation model. For this purpose, bioactive borate glass powders containing therapeutic ions were prepared by melt-cast method and subsequently scaffolds were fabricated using polymer foam replication technique. The scaffolds were implanted subcutaneously for 4 weeks in Sprague Dawley rats. Bare borate glass scaffolds with the same microstructure were used as the control. Histology was used to evaluate tissue ingrowth and blood vessel formation in the implants. Additionally, the antibacterial activities of cerium, gallium and vanadium containing porous bioactive glass scaffolds were investigated in vitro by a zone inhibition method. Results revealed that addition of cerium ions to the borate glass network caused an increase in blood vessel formation. On the other hand, a decrease was obtained in angiogenesis in gallium and vanadium-containing glasses. All of the scaffolds prepared in the study did not show any antibacterial activity towards Escherichia coli and Staphylococcus aureus.     

Structural behavior and in vitro bioactivity evaluation of hydroxyapatite-like bioactive glass based on the SiO2-CaO-P2O5 system

Silicate bioglass is of great importance in bone engineering because of its excellent bioactivity and osteogenic effects. In this study, hydroxyapatite-like bioactive glass based on the xSiO₂-CaO-P₂O₅ (x = 30, 45, 60 and 90 mol.%, Ca/P = 1.67) system was synthesized by the sol-gel method, and the corresponding structural evolution, apatite-forming ability and cytotoxicity were systematically investigated. The results suggest that both a higher heat treatment temperature and a lower SiO₂ content increase the crystallinity tendency of the bioglass, and the samples become obviously compact as the SiO₂ amount increases from 30 to 90 mol.%. Compared with the samples with higher SiO₂ content, the 30Si sample shows more remarkable internal connected mesoporous structures, with a higher specific surface area up to 129.12 m²/g, exhibiting excellent hydroxyapatite formation in simulated body fluid. Moreover, no obvious inhibitory effect was presented on human periodontal ligament cells (hPDLCs) for any of the silicate glass samples.     

Development of a simplified etch-and-rinse adhesive containing niobiophosphate bioactive glass

PurposeThe aim of this study was to evaluate radiopacity, degree of conversion (DC), Knoop hardness (KHN), ultimate tensile strength (UTS) and microtensile bond strength (µTBS) to dentin of an experimental adhesive containing micro-filler of niobium–phosphate bioactive glass (NPG).Materials and methodsThe NPG glass was produced by fusion of NbO₅, Na₂CO₃, CaO, (NH₄)₂HPO₄ at 1400 °C. After cooling, the glass was ground to a mean particle size<25 µm, and either added (40 wt%) to an experimental adhesive resin mix containing monomers and solvent, or not. The DC of the adhesives was evaluated by Fourier transform infrared spectroscopy. Flat dentin surfaces were obtained from 16 molar teeth, and prepared for use to evaluate µTBS (n=8). An hourglass-shaped matrix (UTS and KHN) or disk-shaped matrix (radiopacity) was filled with adhesive and light-polymerized. The data from each test were analyzed by appropriate statistical methods.ResultsThe presence of glass particles made the adhesive system radiopaque. Addition of bioactive NPG glass particles to the adhesive system prevented decreases in bond strength; reduced the UTS and increased DC and KHN. All groups showed predominance of adhesive failure mode.ConclusionAddition of 40% NPG glass may be an alternative to obtain an adhesive system with adequate mechanical and bond strength to dentin properties.     

Hydrothermally crystallized Sr-containing bioactive glass film and its cytocompatibility

Sr-containing bioactive glass film with the Sr/(Ca+Sr) atomic ratio of 20% was sol-gel coated on titanium substrate, followed by hydrothermal treatment in a mixed phosphate solution (8 mM CaHPO₄ and 2 mM SrHPO₄) and other media at 120 or 140 °C. X-ray diffraction (XRD) analysis confirms amorphous nature of the gel powder calcined at 610 °C, but small peaks of Ca_1.8Sr_0.2SiO₄ or Ca_1.5Sr_0.5SiO₄ are also present. The absorption bands of Si-O-Si, PO₄ and OH groups and a weak absorption band of NO₃ groups appear in FT-IR spectrum of the calcined gel powder. Hydroxyapatite (HA) is detected for the hydrothermally treated sample by XRD and Raman analyses. Sr-containing HA nanocrystallites are formed on the film through a dissolution and precipitation mechanism in the hydrothermal treatment. The appearant bonding strength is 21±1 MPa for the both samples. In the test with MC3T3-E1 cells, the two coated samples exhibit larger viability, higher ALP levels and better cell morphology than the polished sample.     

Mechanical properties,bioactivity and cell behavior of barium-containing calcium-phospho-alumino-borosilicate glass

In this study, the effect of replacing CaO by BaO on mechanical properties, bioactivity, and cell adhesion of SiO₂–B₂O₃–Al₂O₃–P₂O₅–CaO–Na₂O based glass was investigated. Mechanical characterization, depth-sensing nano-indentation, and surface micro-indentation techniques were employed to determine the fracture toughness (K_IC). The surface was photographed after micro-indentation effect using scanning electron microscopy. In vitro responses of the compounds of tris-buffered SBF solution were studied from different points of view: (i) morphology and elemental surface analysis using field emission electron microscopy equipped with energy dispersive spectroscopy; (ii) change in bonds using Raman spectroscopy; and (iii) ICP method for detecting the change in ion chemistry of SBF solution. The cell adhesion behavior was qualitatively evaluated by examining the morphology and attachment of mouse fibroblastic cells to the surface of the glasses. The results demonstrated that with the replacement of barium oxide, the hardness of the base glass increased, while the level of fracture toughness was maintained. In addition, in vitro bioactivity of barium oxide-containing glass was reduced compared to the base glass. However, structural dissolution and formation of calcium phosphate layers on their surfaces were also confirmed. The results showed that BaO-incorporated glasses had adequate cell propagation and proliferation, hence enjoying appropriate biocompatibility for use in coating applications.     

Electrophoretic deposition of bioactive glass nanopowders on magnesium based alloy for biomedical applications

To slow down the initial biodegradation rate of magnesium (Mg) alloy, crystalline nano-sized bioactive glass coating was used to deposit on micro-arc oxidized AZ91 samples via electrophoretic deposition (EPD). Zeta potential and conductivity of the bioactive glass suspension were characterized at various pH values to identify the most stable dispersion conditions. The bone-bonding properties of bioactive glass coated samples were evaluated in terms of apatite-forming ability during the immersion in simulated body fluid (SBF) solution. Results revealed that the ability to form a bioactive glass coating via EPD was influenced by the degree of its crystalline phase composition. Moreover, the potentiodynamic polarization tests recorded significant drops in corrosion current density and corrosion rate of the coated samples which implies a good level of corrosion protective behavior. These preliminary results show that this process will enable the development of Mg implants in the later stage of bone healing.     

Fabrication of bioactive glass scaffolds by stereolithography: Influence of particle size and surfactant concentration

For decades, bioactive glass (BAG) has been utilized as a competent bone substitute owing to its intrinsic properties, such as outstanding biocompatibility and bioresorbability. Stereolithography (SL) is an additive manufacturing technology used to produce highly accurate three-dimensional BAG-based bone substitutes. However, the preparation of BAG-based SL resin is always a challenge, especially because of the inevitable sedimentation of BAG particles. In this study, BAG particles with different sizes were prepared by dry grinding (BAG_dry, greater particle size) and wet grinding (BAG_wet, finer particle size). Then, BAG_dry or BAG_wet SL resins with various amounts of surfactant were analyzed. The sedimentation rate for BAG powder increased with increasing particle size but decreased with increasing amounts of surfactant added to the resin. BAG_wet SL resins had a longer shelf life, so printing could still be finished after 14 days, whereas BAG_dry SL resins were no longer useable after 5 days. However, the BAG particle size did not affect the printing accuracy or scaffold strength. According to our results, BAG-based SL resin fabricated with BAG_wet (particle size <1.6 μm) and 5 wt% surfactant exhibited better resistance to sedimentation.     

Bioactive assessment of bioactive glass nanostructures synthesized using synthetic and natural silica resources

The sol-gel route of synthesizing bioactive glasses of composition 45S5 has shown higher compatibility than the melt casting method. In bioactive glass synthesis, a major silica source is derived from the synthetic tetraethyl orthosilicate precursor. This work demonstrates the sol–gel-derived bioactive glass prepared from rice husk and TEOS as silica sources. In this study, the effect of crystallization with respect to the silica source in bioactive glass composition was investigated to gain further understanding on the processes involved in the fabrication of bioglass. The in vitro biodegradation and apatite formation of the bioactive glass in simulated body fluid was investigated by spectroscopic and morphological studies. Both the bioactive glasses show a change in morphology toward nanostructured apatite formation after in vitro immersion studies. Further, the hemocompatibility of bioactive glass prepared using rice husk is similar to bioactive glass prepared from organic silica sources. This promises the possibility of synthesizing low cost and biocompatible bioactive glass 45S5 system for tissue engineering applications.     

HPLC analysis of eluted monomers released from dental composites containing bioactive glass

Objectives: The aim of the present study is to evaluate the released residual monomers from composite resins that contain different proportions of bioactive glass (BAG). Methods: Experimental resin composites were prepared by a resin matrix (50% BisGMA and 50% TEGDMA) and inorganic filler with BAG (5, 10 and 30%). Each resin composite was placed in the tooth cavity (n = 5). After polymerisation, samples were immediately immersed in 75% ethanol and 25% deionised water (6 ml) at 37 °C. Residual monomers (Bis-GMA, TEGDMA, HEMA and UDMA) that were eluted from the composites for 10 m, 1 h, 1 d, 7 d and 30 d were analysed by high-performance liquid chromatography (HPLC). The data were analysed with one-way ANOVA and Tukey HSD at a p < 0.05 significance level. Results: Among the time periods, the fastest released residual monomer was observed in the 10 m elution. The highest amount of released residual monomer from all groups (except the control group) was TEGDMA, whereas this was HEMA for the control group. The amounts of residual monomers eluted from BAG30 were significantly higher than other groups (p < 0.05). Conclusions: The release of the monomer increases in accordance with the increased BAG addition to the composite resins.     

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.     

Synthesis, characterization and microbiological response of silver doped bioactive glass nanoparticles

Glass nanoparticles containing 1, 3, 5, and 10 wt% of Ag₂O (coded; GAg1%, GAg3%, GAg5%, and GAg10%, respectively) were synthesized through a quick alkali mediated sol-gel method and were characterized by TEM, XRF, FT-IR, XRD, TGA, and DSC. Thermal analysis showed that all organic and inorganic by-products were completely decomposed before 700 °C and, hence, all glass samples were stabilized at this temperature. XRD confirmed the amorphous nature of all glasses after stabilization. TEM micrographs showed that the average particle sizes of all samples were less than 100 nm in diameter and the XRF showed that the compositions of the obtained glasses were almost consistent with the designed ones. The samples GAg1%, GAg3%, GAg5%, and GAg10%, showed average pore diameters of 19.85, 18.22, 13.32, and 19.62 nm and specific surface areas of 73.18, 100.38, 192.6, and 55.7 m²/g, respectively. In addition, their porosity% was 76.53, 83.20, 77.97, and 79.61%, respectively. The FT-IR spectra of all glasses showed bands located in the range of 1000-1200, 725-800, and 450-480 cm⁻¹ that correspond to the Si-O-Si asymmetric stretching vibration, the Si-O-Si symmetric stretching vibration, and the Si-O-Si bending mode, respectively. Finally, all samples had an anti-bacterial effect against different types of bacteria and the extraction of silver ions from them followed a diffusion-controlled mechanism, which could demonstrate their ability to treat bone infection.     

Effect of S53P4 bioactive glass content on structural and in-vitro behavior of hydroxyapatite/bioactive glass mixtures prepared by mechanical milling

This work presents silicon-substituted hydroxyapatite preparation through planetary ball milling using biogenic hydroxyapatite and different wt% of S53P4 bioactive glass (5, 10, 15, and 20 wt%) sources for the first time. The prepared mixtures showed a BHAp lattice contraction with SiO₄^4? incorporation; rich- and poor-Si phases were subsequently identified. Furthermore, two types of interaction among the functional groups in the S53P4 and BHAp mixtures are proposed. First, the 95-5 (wt.%) sample displayed a BHAp lattice with SiO₄^4?, CO₃^2?, and OH^? ions substitution. In samples with S53P4 BG content higher than 95-5, the lattice substitution was related to SiO₄^4?, PO₄^3?, and CO₃^2? ions, and a dehydroxylation process occurred in the BHAp. Finally, the bioactive behavior of the samples was studied by immersion in Hank's solution for 7, 14, and 28 days. The results showed that the mixtures formed a bone-like apatite layer with a dune-like morphology that increased in size and quantity with increasing S53P4 content in the mixtures.     

Synergistically reinforcement of a self-setting calcium phosphate cement with bioactive glass fibers

Calcium phosphate cements (CPCs) are highly promising for clinical uses due to their in situ-setting ability, excellent osteoconductivity and bone-replacement capability. However, the low strength limits their uses to non-load-bearing applications. In the present research, first, bioactive glass fibers (BGFs) in the ternary SiO₂-CaO-P₂O₅ system were prepared, and then the fiber composites with compositions based on CPC and BGFs were prepared and characterized. Then, the effect of structure and amount of BGF incorporation into the CPC system, and the effect of mechanical compaction on the fiber-modified system were investigated. The results showed that the compressive strength of the set cements without any BGFs was 0.635 MPa which was optimally increased to 3.69 MPa by applying 15% BGF and then decreased by further addition of it. In addition, both the work-of-fracture and elastic modulus of the cement were considerably increased after applying the fibers in the cement composition. Also, the setting time slightly decreased by applying the fibers. In summary, processing parameters were tailored to achieve optimum mechanical properties and strength. The prepared composite may be useful in surgical sites that are not freely accessible by open surgery or when using minimally invasive techniques.     

3D printing of polycaprolactone/bioactive glass composite scaffolds for in situ bone repair

3D printing technology can fabricate customized scaffolds based on patient-derived medical images, so it has attracted much attention in the field of developing bone repair scaffolds. Polycaprolactone (PCL) is a suitable polymer for preparing bone repair scaffolds because of its good biocompatibility, thermal stability, excellent mechanical properties and degradable properties. However, PCL is a bioinert material and cannot induce new bone formation at the defect site. In this study, the bioactive material 58s bioactive glass was mixed into PCL to form PCL/bioactive glass composite material. The results of contact angle showed that the hydrophilicity of the scaffold was significantly enhanced with the increase of bioactive glass content. In vitro experiment results showed that, with the increase of bioactive glass content, cell adhesion and proliferation were enhanced, the expression levels of Runx2 and Collagen I(COL-I) were upregulated. The experimental results of in vivo radial defect repair in rats also showed that the effect of bone repair was improved with the increase of bioactive glass content. In conclusion, PCL customized bone repair scaffold containing 20% bioactive glass has widely potential used in the field of clinical bone repair.     

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.     

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.     

Reinforcement with reduced graphene oxide of bioactive glass scaffolds fabricated by robocasting

45S5 bioactive glass composite scaffolds reinforced with reduced graphene oxide (rGO) were fabricated for the first time by robocasting (direct-writing) technique. Composite scaffolds with 0–3 vol.% content of rGO platelets were printed, and then consolidated by pressureless sintering at 550 or 1000 °C in Ar atmosphere. It was found that the addition of rGO platelets up to 1.5 vol.% content enhanced the mechanical performance of the 45S5 bioactive glass scaffolds in terms of strength and toughness. Best performance was obtained for 1 vol.% rGO, which yielded an enhancement of the fracture toughness of ∼850 and 380% for sintering temperatures of 550 and 1000 °C, respectively, while the compressive strength increased by ∼290 and 75%. rGO addition thus emerges as a promising approach for the fabrication of novel bioglass scaffolds with improved mechanical performance without deterioration of their bioactivity, which may then find use in load-bearing bone tissue engineering applications.     

Electrochemical study of the in vitro degradation of plasma-sprayed hydroxyapatite/bioactive glass composite coatings after heat treatment

Hydroxyapatite (HA)-coated implants plasma-sprayed on metallic substrates have been widely used in load-bearing applications. In the present work, the in vitro behaviors of bioactive glass-containing HA coatings with post-deposition heat treatment in a simulated body fluid has been performed by means of electrochemical techniques. Annealing of the coatings in air at 650 °C led to recrystallization of amorphous calcium phosphate and effectively increased the conversion of non-apatite phases into apatite. The heat treatment also resulted in a reduction of layer defects associated with plasma-sprayed coatings without adversely affecting bond strength of the coatings. Moreover, the heat-treated coatings significantly increased the corrosion potential and polarization resistance value by approximately two times as compared to untreated samples. Improved corrosion resistance could be attributed to reduction of layer defects and enhancement of coating crystallinity.     

In vitro dissolution of bioactive glass S53P4 microspheres

Static and dynamic in vitro dissolution studies showed large differences for various size-fractions of non-porous, flame-sprayed commercial microspheres (45–500 µm) of bioactive glass S53P4. The smaller the spheres, the more their composition deviated from the nominal glass. The dissolution studies were carried out in simulated body fluid and tris(hydroxymethyl) aminomethane buffer for seven days. The ion concentrations in solutions were analyzed using inductively coupled plasma optical emission spectrometry, and the pH was measured as a function of time. Also, changes in the sphere size distribution and mass losses were determined. The calcium phosphate and the silica-rich layers at the sphere surfaces were investigated using scanning electron microscopy after several immersion times. The smallest (45–90 µm) spheres appeared almost inert. In contrast, typical silica-rich and calcium phosphate layers were identified at the largest spheres after three days of static and dynamic dissolutions. During the past years, bioactive glass microspheres have been added to paste-like injectable bone grafting materials, putties to enhance their molding properties. The obtained results provide a better understanding of the dissolution patterns of bioactive glass microspheres.     

WS2/bioactive glass composites: Fabrication,structural, mechanical and radiation attenuation properties

Ionizing radiation interaction might occur during diagnostic imaging and radiotherapy procedures. It has been reported that gamma-ray radiation can damage the living cells through the energy transfer. Therefore, investigation the ionization radiation attenuation properties of biomaterials have a crucial importance. In the current study, tungsten disulphide (WS₂) nanopowder-containing borate-based bioactive glass composites were prepared. Their physical, structural, mechanical and ionization radiation attenuation properties were investigated in detail. Monte Carlo simulations and radiation attenuation properties were studied through MCNPX and Phy-X/PSD. Results showed that sintering performed at 575 °C for 1 h in air atmosphere caused formation of some tungsten trioxide in the structure. Addition of WS₂ nanopowders increased the bulk density and improved the mechanical properties of the prepared bioactive glass composites. Simulation studies revealed the influence of WS₂ content on reduction the build-up factors and enhancement of the photon attenuation ability for all the considered photon energies.