Bioactive Glass Composites Research Articles

Characterization of the conversion of bone cement and borate bioactive glass composites.

Borate bioactive glass 13-93B3 converts into an osteoconductive hydroxyapatite-like material in a liquid medium. In this study, 13-93B3 was incorporated into a commercial PMMA (poly(methyl methacrylate)) bone cement, and the conversion of the glass into a precipitate in solution was investigated with scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared (spectroscopy)-attenuated total reflection, and micro-Raman spectroscopy. Glass particles of 5, 33, and 100 μm diameter were each mixed with the PMMA cement to create 20, 30, and 40% glass-loaded composites. Precipitate formation was found to be a calcium-deficient apatite partially substituted with magnesium ions that resembles native bone material and would ideally encourage bone growth better than stoichiometric hydroxyapatite. Composites of bone cement and 13-93B3 show promise as a means of encouraging bone attachment to the surface of the bone cement.

Analysis of structure, bioactivity and hardness of titanium incorporated bioactive glass

A series of bioactive glass composition were prepared, and the effects of TiO2 addition on the structure, bioactivity and hardness of the glasses were analyzed. This study consisted of glass characterization, simulated body fluid (SBF) trials, and hardness testing. Three glasses were formulated, where a SiO2-CaO-Na2O-P2O5 bioactive glass was used as control, with the addition of 5 and 10 wt.% TiO2 at the expense of CaO. X-ray diffraction patterns confirmed that an amorphous microstructure was obtained for all three glasses. Differential thermal analysis indicated an increase in the glass transition temperature of the glass series from 660°C to 721°C with the incorporation of TiO2. Hot stage microscopy results exhibited higher sintering and softening temperatures for TiO2 containing glasses. Each glass was then incubated in SBF for 1, 10, and 30 days. Scanning electron microscopy images confirmed that the calcium phosphate particulates were precipitated on control glass after 10 days, however, for TiO2 containing glasses, the deposition layer was only observed after 30 days. The hardness of SBF incubated samples were tested, where TiO2 containing glasses showed significantly higher hardness values at each incubation period, with 0.72 GPa for control and 1.71 GPa for the TiO2 containing glass, after 30 days of incubation.

Poly(lactic-co-glycolic acid)-bioactive glass composites as nanoporous scaffolds for bone tissue engineering: In vitro and in vivo studies.

The aim of the present study was to investigate the feasibility of using composite scaffolds of poly(lactic-co-glycolic acid) (PLGA) and bioactive glass (BG) to repair bone defects. PLGA/BG composite scaffolds were prepared by thermally-induced phase separation. Scanning electron microscopy (SEM) was used to study the morphology, and liquid (absolute ethanol) replacement was used to calculate the porosity of the scaffold. The biocompatibility and degradation of the scaffold were determined using human osteosarcoma cell line MG-63 and animal experiments. SEM showed that the scaffold had a nanofibrous three-dimensional network structure with a fiber diameter of 160–320 nm, a pore size of 1–7 µm, and a porosity of 93.048±0.121%. The scaffold structure was conducive to cell adhesion and proliferation. It promoted cell osteogenesis and could be stably degraded in vivo.

Bioactive composites for bone regeneration

Bone, the organ that separates vertebrates from other living beings, is a complex tissue responsible of mobility, body stability, organ protection, and metabolic activities such as ion storage. Ceramic materials are appropriate candidates to be used in the fabrication of scaffolds for bone healing. Biocompatible ceramic materials may also be created to deliver biologically active substances aimed at maintaining, repairing, restoring, or boosting the function of tissues and organs in the organism. Glass-ceramic materials furnish flexible properties appropriate for some particular applications. Because of the controlled devitrification and the evolution of variable dimensions of crystalline and glassy phases, glass-ceramics considerably overcome the lacunae found in glasses. A wide range of bioactive glass compositions had been developed since the early 1970s to make them appropriate for many clinical applications. Many bioactive ceramic composite materials attach to living bone through an apatite layer, which is developed on their surfaces in the living body. This paper reviews the most used bioactive ceramics for bone tissue regeneration, with specific accentuation on the material characteristics.

Bone healing with niobium-containing bioactive glass composition in rat femur model: A micro-CT study

ObjectiveThe aim of this study is to investigate bone healing ability of niobium-containing bioactive glasses in rat femur model with quantitative and qualitative measurements through x-ray computed microtomography. MethodsNiobium-containing bioactive powders and scaffolds were produced by sol–gel route (BAGNb). Glasses without niobium addition were produced as well (BAG). Five groups were used: BAGNb powders, BAG powders, BAGNb scaffolds, BAG scaffolds and, as a control group, autogenous bone was used. Materials were implanted in the femur of male rats (Wistar Lineage n=10) and the healing was observed after 15, 30 and 60 days. After the post-operative times, samples were scanned by X-ray microcomputed tomography where morphometric measurements and the mineral density were assessed in image software. ResultsNo postoperative complications were observed after surgery. BAGNb glasses presented higher mineral deposition, which was observed in the relative volume of bone and the mineral density when compared BAG groups. In these parameters, no statistical difference was found between BAGNb and autogenous bone. The BAGNb powders presented a higher amount of mineralized tissue when compared to BAGNb scaffolds. The analysis of trabecular structure showed lower trabecular formation in synthetic materials when compared to autogenous bone. SignificanceNiobium-containing bioactive glasses promoted bone formation comparable to that of the autogenous bone without compromising the quality of the formed bone.

Alginate-bioactive glass containing Zn and Mg composite scaffolds for bone tissue engineering

Past researches on bone regeneration field have shown the positive impacts of the presence of Zinc and Magnesium ions in the bioactive glasses composition. However, there is no dedicated work on the effect of the aforementioned bio-glass on the polymer matrix composites. The key idea of the approach is to improve antibacterial efficacy, biological activity and mechanical properties of the bone composite scaffolds by incorporating bioactive glasses containing Zinc and Magnesium into alginate networks. The prepared scaffolds were characterized by SEM, ATR-FTIR and XRD analysis. Compression strength of obtained highly porous composite scaffolds was remarkably enhanced by the presence of bio-glass particles. The maximum compressive strength (1.7 MPa) was obtained for alginate composite containing 1 g Mg-Zn-BG. In vitro evaluation such as swelling, bio-mineralization, biodegradation were carried out, which indicates that incorporation of bio-glass promotes apatite deposition on composite scaffolds. Cytotoxicity, cell attachment and proliferation and osteogenic differentiation were also evaluated by culturing MG-63 cells on scaffolds. ICP analysis were conducted after 60 days of incubation in PBS solution to verify the ion release capability of the composite scaffolds, particularly Zn and Mg ions, which resulted in significant antibacterial efficacy enhancement of composite scaffolds against E. coli and S. aureus bacteria.

Bioactive glass (45S5)-based 3D scaffolds coated with magnesium and zinc-loaded hydroxyapatite nanoparticles for tissue engineering applications

Bioactive glass (BG)-based scaffolds of 45S5 composition covered with hydroxyapatite nanoparticles loaded with Mg2+, Zn2+ and, both Mg2+ and Zn2+ ions, were developed and tested as materials for tissue engineering applications. The scaffolds were prepared by the foam replica technique and mono- and bi-metal loaded and unloaded hydroxyapatite nanoparticles (HA, Zn-HA, Mg-HA and Mg-Zn-HA) were obtained by an adaptation of the wet chemical deposition method. Coating of BG with these nanoparticles was performed by dip-coating to obtain HA-BG, Zn-HA-BG, Mg-HA-BG and Mg-Zn-HA-BG scaffolds.As predictor of the bone bonding ability of the produced scaffolds, in this study we investigated the formation of an apatite layer on the scaffold surfaces in the presence of simulated body fluid. The cytotoxicity and osteogenic properties of the materials in vitro was evaluated using human osteoblast-like MG-63 cell cultures. The mineralization assay following Kokubo’s protocol indicated that bi-metal loaded Mg-Zn-HA-BG scaffolds exhibited higher/faster bioactivity than mono-metal loaded scaffolds while mineralization of HA-BG, Zn-HA-BG and Mg-HA-BG was similar to that of uncoated scaffolds. Moreover, an increase of proliferation of MG-63 cells after 48 h and 7 days was measured by BrdU assays for Mg-Zn-HA-BG scaffolds. In agreement with these results, SEM images confirmed increased interaction between these scaffolds and cells, in comparison to that observed for mono-metal-loaded HA-coated scaffolds. Altogether, the obtained results suggest that nanocrystalline Mg-Zn-HA coatings enhance the biological performance of standard scaffolds of 45S5 BG composition. Thus these novel ion doped HA coated scaffolds are attractive systems for bone tissue engineering.

A comparison of lithium-substituted phosphate and borate bioactive glasses for mineralised tissue repair

ObjectivesWnt/β-catenin signalling plays important roles in regeneration, particularly in hard tissues such as bone and teeth, and can be regulated by small molecule antagonists of glycogen synthase kinase 3 (GSK3); however, small molecules can be difficult to deliver clinically. Lithium (Li) is also a GSK3 antagonist and can be incorporated into bioactive glasses (BG), which can be used clinically in dental and bone repair applications and tuned to quickly release their constituent ions. MethodsHere, we created phosphate (P)- and borate (B)-based BG that also contained Li (LiPBG and LiBBG) and examined their ion release kinetics and the toxicity of their dissolution ions on mouse 17IA4 dental pulp cells. ResultsWe found that although LiPBG and LiBBG can both quickly release Li at concentrations known to regulate Wnt/β-catenin signalling, the P and B ions they concomitantly release are highly toxic to cells. Only when relatively low concentrations of LiPBG and LiBBG were placed in cell culture medium were their dissolution products non-toxic. However, at these concentrations, LiPBG and LiBBG’s ability to regulate Wnt/β-catenin signalling was limited. SignificanceThese data suggest that identifying a BG composition that can both quickly deliver high concentrations of Li and is non-toxic remains a challenge.

An Investigation on Effective Atomic Numbers and Mass Attenuation Coefficients of Some Bioactive Glasses

A bioactive material is known as a natural or man-made material that prompts a specific biological response from the body such as bonding to tissue. They have numerous applications in the repair and reconstruction of diseased and damaged tissue, and tissue and hard tissue (bone) re-engineering. In this study, we have evaluated the same gamma-ray shielding parameters such as mass attenuation coefficient (μ/ρ), effective atomic number (Z eff ), half value layer (HVL), mean free path (MFP) for selected bioactive glasses. The shielding effectiveness of the selected glasses is found comparable each other. Effective atomic number (Z eff ) is convenient parameters used to characterize the radiation response of a multi-element material in the technical and industrial applications, radiation shielding design, absorbed dose. Thus, it is very significant to choose accurate method to determine this parameter unambiguously. In the present study, effective atomic number of different type of material has been calculated by using calculation method for total photon interaction in the energy region of 1 keV to 100 GeV. The results obtained from this study show that effective atomic number depends strongly on the chemical composition of the interaction material in the lower as well as higher energy region, but in the intermediate energy region, the chemical composition dependence becomes very weak. This result can be interpreted that an increase in P 2 O 5 content in the composition of bioactive glasses results as an in increase of bioactivity of that particular materials. Therefore, this study underlines the finding that bioactive glasses would be potential biomaterials for biomedical applications.

Using Bioactive Glasses in the Management of Burns.

The management of burn injuries is considered an unmet clinical need and, to date, no fully satisfactory solution exists to this problem. This mini-review aims to explore the potential of bioactive glasses (BGs) for burn care due to the therapeutic effects of their ionic dissolution products. BGs have been studied for more than 40 years and boast a long successful history in the substitution of damaged tissues, especially bone. Considering their exceptional versatility and attractive characteristics, these synthetic materials have also recently been proposed in the treatment of soft tissue-related disorders such as skin wounds. Specifically, improving fibroblast proliferation, inducing angiogenesis, and eliciting antibacterial activity (with the additional advantage of avoiding administration of antibiotics) are all considered as key added values carried by BGs in the treatment of burn injuries. However, some issues deserve careful consideration while proceeding with the research, including the selection of suitable BG compositions, appropriate forms of application (e.g., BG fibers, ointments or composite patches), as well as the procedures for reliable in vivo testing.

Creep, recovery, and stress relaxation behavior of nanostructured bioactive calcium phosphate glass-POSS/polymer composites for bone implants studied under simulated physiological conditions.

The creep and recovery and the stress relaxation behaviors of poly(butylene adipate-co-terephthalate) (PBAT) and polyhydroxyalkanoates (PHA) binary blends incorporating 30 wt % of a mixture of trisilanolisobutyl polyhedral oligomeric silsesquioxanes (POSS) and calcium phosphate glass (CaP-g) were investigated under simulated physiological and human body temperature conditions. The synergistic effect of PHA and CaP-g/POSS filler remarkably improved the creep behavior of the PBAT matrix and decreased its residual strain, consequently enhancing its elastic recovery. A considerable increase of the relaxation modulus of the hybrid materials was also observed upon incorporation of PHA and CaP-g/POSS. The relaxation modulus of the neat PBAT sample increased from ~60 MPa to ~1600 MPa after addition of 30 wt % CaP-g/POSS and 70 wt % PHA. However, after exposure of the composites to the simulated human body conditions for 14 days, a drop of dynamic mechanical properties of the studied material systems was observed along with formation of a desirable calcium phosphate phase on the material surface. The long-term (i.e., up to 7 × 105 s) viscoelastic behavior of the studied materials was successfully predicted using the time-temperature superposition principle and the obtained creep strain and the relaxation modulus master curves were satisfactorily fitted to the Findley power law equation and the generalized Maxwell model, respectively. This study demonstrates a facile method for tailoring CaP-g/POSS bioactive glasses composition for bone-like apatite formation on biopolymer surfaces. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2419-2432, 2019.

Cu-Releasing Bioactive Glass Coatings and Their in Vitro Properties.

Bioactive glasses are well-known materials suitable for bone-related applications thanks to their biocompatibility and osteoconductivity. In order to improve their in vivo performance, the modification of the glass composition by adding ions with specific biological functions is required. As copper (Cu) possesses antibacterial properties, in this study, 5 wt % of CuO has been added to the 45S5 bioactive glass composition. The investigation of the effect of the Cu-containing bioactive glass on cellular behavior has revealed that the presence of Cu induces an early differentiation of human mesenchymal stem cells through osteoblast phenotype, promotes the expression of anti-inflammatory interleukin, and reduces proinflammatory interleukin expression. With the aim to produce coatings with antibacterial properties, the Cu-containing bioactive glass was used as the target material for the pulsed laser deposition (PLD) of bioactive thin films. PLD experiments were carried out at different substrate temperatures to study the effect on the film's characteristics. All of the films are compact, crack-free, and characterized by a rough morphology and good wettability. The in vitro bioactivity was demonstrated by the apatite growth on the coating surface, after soaking in simulated body fluid, revealed by Raman spectroscopy and scanning electron microscopy-energy dispersive X-ray analyses. The antibacterial study proved that the material showed more effective activity against three Gram-negative bacteria ( Pseudomonas aeruginosa, Escherichia coli, Salmonella enterica) rather than against Gram-positive bacteria ( Staphylococcus aureus).

Enhanced antimicrobial properties of bioactive glass using strontium and silver oxide nanocomposites

ABSTRACTBioactive glass has a wide range of biomedical applications. It has attracted immense interest due to its unique ability to bond with a bone through ion exchange in simulated body fluid (SBF) when implanted inside the body. This study concerns sol-gel synthesis of a new bioactive glass composition: 55SiO2-40CaO-(5-x) SrO-xAg2O doped with different mol% of silver as an antibacterial agent, i.e. 0%, 2% and 4% AgSr(0), AgSr(2) & AgSr(3), respectively. This method is a widely used in the preparation of glass ceramics because of its low-temperature. The effect of introducing strontium in addition to silver as an antimicrobial agent into the bioglass matrix was studied. Structural studies were conducted using various techniques including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM) and High-resolution transmission electron microscopy (HR-TEM). Bioactivity was investigated by in-vitro synthesis involving immersion of the samples in SBF for different time intervals. The XRD, FTIR and FE-SEM results confirmed the formation of a hydroxylapatite layer on the surface of the finally prepared bioglass materials. An antimicrobial study revealed that the prepared bioactive glass showed a significant effect on two bacteria E. coli and S. aureus.

Synthesis and physico-chemical characterization of fluoride (F)- and silver (Ag)-substituted sol-gel mesoporous bioactive glasses

Abstract Synthesis and use of novel compositions of bioactive glasses (BGs) for hard tissue engineering are of important significance in the biomedical field. In this study, we successfully synthesized a series of 58S-based BGs containing fluoride (F−) and silver (Ag+) ions through a sol-gel method for possible use in bone/dental regeneration and antibacterial strategies. Characterizations of samples were performed by using thermal analyses (thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC)), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), textural analysis (N2 adsorption-desorption), and morphological observations by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The obtained data revealed that the fabricated BGs are in a glassy state before incubation in the Kokubo’s simulated body fluid (SBF), and an apatite-like layer is formed on their surface after 7 days of immersion in SBF. The size of the glass particles was in the nano-range (about 100 nm or below), and their pore size was in the mesoporous range (15-25 nm). These early results suggest that the F- and Ag-doped glasses show promise as multifunctional bioactive materials for bone/dental tissue engineering.

Comparative antibacterial study between bioactive glasses and vancomycin hydrochloride against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa

Background This work targets the comparison of the antibacterial activity of different bioactive glasses as particles and those coating the surface of 316 l stainless steel sheet, with that of vancomycin hydrochloride antibiotic, to determine the best efficiency of the aforementioned materials for medical and surgical purposes. Materials and methods Different bioactive glass composites (borate, B, S, and B5), composed of different ratios of oxides, such as SiO2, Na2O, CaO, B2O3, P2O5, and MgO, were prepared. The antimicrobial activity of different synthesized glasses as well as vancomycin hydrochloride antibiotic was carried out against various Gram-negative and Gram-positive pathogens. The different bioactive glasses (0.05 g) were placed each in wells (1 cm in diameter) of pathogen-seeded nutrient agar, as particles or coated on 316 l stainless steel 1.0×1.5 cm sheets for agar diffusion method. The antibacterial test of vancomycin hydrochloride in different concentrations (25, 50, 75, and 100 mg/ml in distilled H2O) was carried out. The pathogen cell viability in presence and absence of glass composite was investigated using electron microscopy and cell count method. Nutrient broth (50 ml) was inoculated with Staphylococcus aureus along with 0.05 g of borate particles, incubated at 37°C and 150 rpm for 6 h. Then, the samples were examined under electron microscope, and the final pH was measured. A volume of 0.1 ml of each sample was further inoculated on solid nutrient agar, incubated at 37°C for 24 h, and then colony count was carried out. Results and discussion The borate bioactive glass was effective either as particles or coated on 316 l stainless steel. The other types of bioactive glasses coating the stainless steel produced a better antibacterial activity than the particles. The transmission electron microscope, showed the damaged bacterial cells of S. aureus after incubation with borate bioactive glass. The colony count of S. aureus after bioglass treatment was 18×102, whereas in the control sample was 25×106; the final pH was 10.4.

Bioactive Glasses and Glass-Ceramics for Healthcare Applications in Bone Regeneration and Tissue Engineering.

The discovery of bioactive glasses (BGs) in the late 1960s by Larry Hench et al. was driven by the need for implant materials with an ability to bond to living tissues, which were intended to replace inert metal and plastic implants that were not well tolerated by the body. Among a number of tested compositions, the one that later became designated by the well-known trademark of 45S5 Bioglass® excelled in its ability to bond to bone and soft tissues. Bonding to living tissues was mediated through the formation of an interfacial bone-like hydroxyapatite layer when the bioglass was put in contact with biological fluids in vivo. This feature represented a remarkable milestone, and has inspired many other investigations aiming at further exploring the in vitro and in vivo performances of this and other related BG compositions. This paradigmatic example of a target-oriented research is certainly one of the most valuable contributions that one can learn from Larry Hench. Such a goal-oriented approach needs to be continuously stimulated, aiming at finding out better performing materials to overcome the limitations of the existing ones, including the 45S5 Bioglass®. Its well-known that its main limitations include: (i) the high pH environment that is created by its high sodium content could turn it cytotoxic; (ii) and the poor sintering ability makes the fabrication of porous three-dimensional (3D) scaffolds difficult. All of these relevant features strongly depend on a number of interrelated factors that need to be well compromised. The selected chemical composition strongly determines the glass structure, the biocompatibility, the degradation rate, and the ease of processing (scaffolds fabrication and sintering). This manuscript presents a first general appraisal of the scientific output in the interrelated areas of bioactive glasses and glass-ceramics, scaffolds, implant coatings, and tissue engineering. Then, it gives an overview of the critical issues that need to be considered when developing bioactive glasses for healthcare applications. The aim is to provide knowledge-based tools towards guiding young researchers in the design of new bioactive glass compositions, taking into account the desired functional properties.

Fabrication, in vitro and in vivo studies of bilayer composite membrane for periodontal guided tissue regeneration.

Development of a guided occlusive biodegradable membrane with controlled morphology in order to restrict the ingrowth of epithelial cells is still a challenge in dental tissue engineering. A bilayer membrane with a non-porous upper layer (polyurethane) and porous lower layer (polycaprolactone and bioactive glass composite) with thermoelastic properties to sustain surgery treatment was developed by lyophilization. Morphology, porosity, and layers attachment were controlled by using the multi-solvent system. In vitro and in vivo biocompatibility, cell attachment, and cell proliferation were analyzed by immunohistochemistry and histology. The cell proliferation rate and cell attachment results showed good biocompatibility of both surfaces, though cell metabolic activity was better on the polycaprolactone-bioactive glass surface. Furthermore, the cells were viable, adhered, and proliferated well on the lower porous bioactive surface, while non-porous polyurethane surface demonstrated low cell attachment, which was deliberately designed and a pre-requisite for guided tissue regeneration/guided bone regeneration membranes. In addition, in vivo studies performed in a rat model for six weeks revealed good compatibility of membranes. Histological analysis (staining with hematoxylin and eosin) indicated no signs of inflammation or accumulation of host immune cells. These results suggested that the fabricated biocompatible bilayer membrane has the potential for use in periodontal tissue regeneration.

A Chemical Approach to Optimizing Bioactive Glass Dental Composites

The chemical microenvironment surrounding dental composites plays a crucial role in controlling the bacteria grown on these specialized surfaces. In this study, we report a scanning electrochemical microscopy (SECM)–based analytic technique to design and optimize metal ion-releasing bioactive glass (BAG) composites, which showed a significant reduction in biofilm growth. SECM allows positioning of the probe without touching the substrate while mapping the chemical parameters in 3-dimensional space above the substrate. Using SECM and a solid-state H+ and Ca2+ ion-selective microprobe, we determined that the local Ca2+ concentration released by different composites was 10 to 224 µM for a BAG particle size of <5 to 150 µm in the presence of artificial saliva at pH 4.5. The local pH was constant above the composites in the same saliva solution. The released amount of Ca2+ was determined to be maximal for particles <38 µm and a BAG volume fraction of 0.32. This optimized BAG-resin composite also showed significant inhibition of biofilm growth (24 ± 5 µm) in comparison with resin-only composites (53 ± 6 µm) after Streptococcus mutans bacteria were grown for 3 d in a basal medium mucin solution. Biofilm morphology and its subsequent volume, as determined by the SECM imaging technique, was (0.59 ± 0.38) × 107 µm3 for BAG-resin composites and (1.29 ± 0.53) × 107 µm3 for resin-only composites. This study thus lays the foundation for a new analytic technique for designing dental composites that are based on the chemical microenvironment created by biomaterials to which bacteria have been exposed.

Novel fluoride and strontium-containing bioactive glasses for dental varnishes-design and bioactivity in Tris buffer solution

ObjectiveThe objective of this study was to establish the overall remineralizing potential of bioactive glasses which were specifically designed to be incorporated in dental varnishes. This study evaluates the in vitro ability of bioactive glasses (BAGs) to release ions including: fluoride, calcium, strontium and phosphate and to form apatite when immersed in Tris buffer solution, and also investigates the effect of increasing strontium substitution for calcium on remineralization potential. Materials and methodsA melt-derived bioactive glass series was formulated (SiO2–Na2O–CaO–P2O5-CaF2) with progressive (0–100%) replacement of calcium (Ca) with strontium (Sr) and prepared. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were utilised before and after immersion for specific time periods (0, 3, 6, 24, 72, 168 h) in 50 ml Tris buffer solution at 37 °C. A fluoride-ISE was used to measure the concentration of fluoride, whilst inductively coupled plasma–optical emission spectroscopy (ICP-OES) was used to measure the concentration of phosphorus, calcium and strontium in the solutions. ResultsThe FTIR and XRD data indicated the amorphous nature of all unreacted bioactive glasses, except for the high Sr-substituted glasses, which crystallised to fluorapatite. Degradation of all the glass powders resulted in fluoride, phosphate and calcium/strontium ion release. All the glasses formed apatite on immersion. Ion release enhanced significantly in the three compositions with 50% SrO substituted for CaO, while calcium ion release was greater for low SrO substitutions. ConclusionIon release data obtained for the new compositions of novel bioactive glasses to be incorporated into varnishes have promise in the prevent and/or treatment of white spot lesions through the release of fluoride, phosphate and calcium/strontium.

Dosage and composition of bioactive glasses differentially regulate angiogenic and osteogenic response of human MSCs.

Vascularization of the fracture site and cell-mediated deposition of the mineralized matrix are crucial determinants for successful bone regeneration after injury. Ceramic biomaterials such as bioactive glasses (BAGs) that release bioactive ions have shown promising results in bone defect regeneration. However, it remains unclear how the dosage and composition of bioactive ions influence the angiogenic and osteogenic behavior of primary human mesenchymal stromal cells (MSCs). Here, we show that exposure to ionic dissolution products from 1393 and 45S5 BAGs can evoke distinct angiogenic and osteogenic responses from primary MSCs in a dose- and composition-dependent manner. Significantly higher concentrations of the pro-angiogenic factors VEGF, HGF, PIGF, angiopoietin, and angiogenin were detected in conditioned media (CM) from MSCs exposed to 45S5, but not 1393, BAGs. Application of this CM to human umbilical vein endothelial cells (HUVECs) resulted in robust 2D tube formation in vitro. Osteogenic differentiation of MSCs was assessed by gene expression analysis and mineralization assays. Low concentrations (0.1% w/v) of 1393 BAGs significantly enhanced the gene expression of RUNX2 and ALP and induced an earlier onset of matrix mineralization compared to all other groups. We further tested whether simultaneous exposure to both BAGs would improve both angiogenic secretion and osteogenic differentiation of MSCs, and did not find evidence to support this hypothesis. Our results provide evidence of BAG composition-dependent enhancement of primary human MSCs' regenerative function, besides also underlining the importance of an in vitro evaluation of the dose-response relationship to translate BAG based approaches into safe and effective clinical therapies. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2827-2837, 2018., 2018.