Glass In Simulated Body Fluid Research Articles

The effect of borate on acellular bioactivity of novel mesoporous borosilicate bioactive glasses for tissue engineering

Four novel mesoporous borate-based 13–93 bioactive glass has been synthesized by a modified Stöber method. Thermogravimetric analysis, Inductively coupled plasma atomic emission spectroscopy, Fourier Transform Infrared Spectroscopy, X-Ray diffraction, Brunauer–Emmet–Teller and Barrett–Joyner–Halenda, nuclear magnetic resonance and Scanning Electron Microscope attached with Energy-dispersive X-ray spectroscopy analyses were carried out to investigate the physicochemical properties, in-vitro acellular bioactivity, and the degradation rate of the bioactive glasses in simulated body fluid across a range of times up to 21 days. The characterization data indicates that the bioactive glasses are amorphous and possess mesoporous properties. Likewise, an increase in boron content reduced the surface area and pore volume of the bioactive glass series. The observed decline is attributed to borate units' smaller atomic radius than silicate. The ability to deposit a new apatite layer in the bioactive glasses depends on the borate concentration. As such, an increase in boron content resulted in a decrease in apatite formation. Additionally, the studies showed that bioactive glasses made of borate degraded more quickly than their silicate counterpart. Overall, borate-based 13–93 bioactive glasses were effectively synthesized, and the in-vitro results showed potential usage for these bioactive glasses in tissue engineering situations where it is desirable to control bone growth or delay the onset of bioactivity.

Early-Stage Dissolution Kinetics of Silicate-Based Bioactive Glass under Dynamic Conditions: Critical Evaluation.

This manuscript presents a systematic and detailed study of ion release from 45S5 bioactive glass to develop a methodology to directly monitor dissolved ions in a simulated fluid via inductively coupled plasma optical emission spectrometry (ICP OES). For the kinetic study, two dynamic tests, an inline ICP test and a flow-through test, are performed with the same flow rate, temperature, pH, ionic strength of the solution, and sample surface to leaching solution volume ratio. The flow-through test allows for the measurement of an initial dissolution rate, as well the maximum amount of any species released from the surface of the glass. In addition, the data from the inline ICP test are obtained by immediate and direct monitoring of ions from the first minutes of contact of the glass with aqueous fluids with pH values of 4 and 7.4. The overall dissolution rates of the tested commercial bioactive glass in simulated body fluid (SBF) (pH 7.4) were significantly lower compared to the initial rate acquired. The methodology developed in this study can be applied to monitor the controlled release of ions with additional therapeutic functionalities, where the amount of ions released in the first minutes can be critical for the resulting biological performance.

Calorimetric approach to assess the apatite-forming capacity of bioactive glasses

This paper investigates a new microcalorimetric approach to assess the capacity of bioactive glasses, to form hydroxyapatite during immersion in physiological fluids. Three silicate glasses were selected namely 45S5 (46.1SiO2-2.6P2O5-26.9CaO-24.4Na2O; mol%), F0 (46.1SiO2-2.6P2O5-37.6CaO-6.8Na2O-6.8K2O; mol%), and F3 (44.8SiO2-2.5P2O5-36.5CaO-6.6Na2O-6.6K2O-3.0CaF2; mol%), synthesized by a melt-quench route and studied initially using electron microscopy. The hydroxyapatite formation of samples immersed in simulated body fluid (SBF) was monitored using X-ray diffraction and Infrared spectroscopy. The microcalorimetric investigations were conducted by observing, over seven days, the thermochemical behavior of glasses in SBF at 37°C and by measuring the heat of acidic dissolution of treated and untreated samples in SBF. The results showed that the samples with the higher capacity to form apatites also present the higher heat variation from day-to-day, with 45S5 presenting the highest heat difference recorded in both experiments. These analyses led to the quantification of the calcium phosphate formed for each bioactive glass composition.

Influence of ZrO2 Addition on Structural and Biological Activity of Phosphate Glasses for Bone Regeneration.

Zirconium doped calcium phosphate-based bioglasses are the most prominent bioactive materials for bone and dental repair and regeneration implants. In the present study, a 8ZnO–22Na2O–(24 − x)CaO–46P2O5–xZrO2 (0.1 ≤ x ≤ 0.7, all are in mol%) bioglass system was synthesized by the conventional melt-quenching process at 1100 °C. The glass-forming ability and thermal stability of the glasses were determined by measuring the glass transition temperature (Tg), crystallization temperature (Tc), and melting temperature (Tm), using differential thermal analysis (DTA). The biological activity of the prepared samples was identified by analyzing X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy-energy dispersive spectra (SEM-EDS), before and after immersion in simulated body fluid (SBF) for various intervals of 0, 1 and 5 days, along with the magnitude of pH and the degradation of glasses also evaluated. The obtained results revealed that the glass-forming ability and thermal stability of glasses increased with the increase in zirconia mol%. The XRD, FTIR, and SEM-EDS data confirmed a thin hydroxyapatite (HAp) layer over the sample surface after incubation in SBF for 1 and 5 days. Furthermore, the development of layer found to be increased with the increase of incubation time. The degradation of the glasses in SBF increased with incubation time and decreased gradually with the increase content of ZrO2 mol% in the host glass matrix. A sudden rise in initial pH values of residual SBF for 1 day owing to ion leaching and increase of Ca2+ and PO43− ions and then decreased. These findings confirmed the suitability of choosing material for bone-related applications.

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

AbstractThe 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.

Corrosion study of biodegradable magnesium based 1393 bioactive glass in simulated body fluid

Abstract The present work deals with study of corrosion behavior of Magnesium based biodegradable alloy added with 1393 bioactive glass in simulated body fluid, which can be used as an orthopedic implant or bone fixation. Various efforts had been done for development of magnesium based alloy but the main problem observed was high corrosion rate. Our work consists of developing a Magnesium based alloy with addition of Zinc, Aluminum and Calcium along with 15% 1393 bio-active glass. The alloying elements have their own advantages associated with them. Further the alloy has been studied for the corrosion behavior after 1 days, 3days, 5 days, 7 days and 14 days. Samples have been tested for their corrosion behavior in simulated body fluid and their corrosion rate has been observed by weight loss method and electro potentio-dynamic tests. Atomic Absorption Spectrophotometry (AAS) of the samples has been done in order to get more precise results. Young's Modulus of the alloy has been found to be in the range of 33.80 GPa–46.72 GPa, which is near to the human bone. Also the surface morphology and phase analysis of the samples has been done by Scanning Electron Microscopy and X-Ray Diffraction Technique. Initial corrosion rate of the sample is fast but after 7 days the decrease in corrosion behavior has been observed. SEM images of the samples have confirmed the formation of hydroxyapatite layer and the X-Ray Diffraction of corrosion products have shown the formation of complexes of Magnesium on the surface.

Comprehensive in vitro and in vivo studies of novel melt-derived Nb-substituted 45S5 bioglass reveal its enhanced bioactive properties for bone healing

The present work presents and discusses the results of a comprehensive study on the bioactive properties of Nb-substituted silicate glass derived from 45S5 bioglass. In vitro and in vivo experiments were performed. We undertook three different types of in vitro analyses: (i) investigation of the kinetics of chemical reactivity and the bioactivity of Nb-substituted glass in simulated body fluid (SBF) by 31P MASNMR spectroscopy, (ii) determination of ionic leaching profiles in buffered solution by inductively coupled plasma optical emission spectrometry (ICP-OES), and (iii) assessment of the compatibility and osteogenic differentiation of human embryonic stem cells (hESCs) treated with dissolution products of different compositions of Nb-substituted glass. The results revealed that Nb-substituted glass is not toxic to hESCs. Moreover, adding up to 1.3 mol% of Nb2O5 to 45S5 bioglass significantly enhanced its osteogenic capacity. For the in vivo experiments, trial glass rods were implanted into circular defects in rat tibia in order to evaluate their biocompatibility and bioactivity. Results showed all Nb-containing glass was biocompatible and that the addition of 1.3 mol% of Nb2O5, replacing phosphorous, increases the osteostimulation of bioglass. Therefore, these results support the assertion that Nb-substituted glass is suitable for biomedical applications.

Influence of strontium on structure, bioactivity and corrosion behaviour of B2O3–SiO2–Na2O–CaO glasses-investigation by spectroscopic methods

Strontium mixed borate based bioactive glasses of the composition (55–x)B2O3–5SiO2–20CaO–20Na2O: xSrO (with x = 2,4,6,8 and 10 mol%) were synthesized using conventional melt quenching technique. Structural variations in the glasses due to addition of SrO were assessed from FTIR and optical absorption spectroscopy methods. Degradation and bioactivity studies of the glasses were performed by immersing the glasses in simulated body fluid (SBF). Degradation studies of these glasses measured as function of immersion time were analyzed in terms of structural modifications taken place due to strontium mixing. The formation of hydroxy apatite (HA) layer on the surface of glasses, treated in SBF solution was examined by XRD, FTIR, optical absorption and scanning electron microscopy studies. The observed bone like apatite formation on glass surface demonstrated the potentiality of the chosen glass for integration with bone. Quantitative analysis of results of the studies on the bioactive behavior of the titled glass indicated that the mixing of SrO to the optimum levels improved its bioactivity.

The effect of serum proteins on apatite growth for 45S5 Bioglass and common sol-gel derived glass in SBF

Abstract The inhibitive effects of serum proteins on apatite growth was compared between melt-derived 45S5 Bioglass® and sol-gel derived bioactive glass of the 70S30C (70 mol% SiO2, 30 mol% CaO). By using techniques of XRD, TEM and Raman spectroscopy, the transformation of amorphous calcium phosphate to crystalline apatite, and the resulting size and aspect ratio of the crystals, in simulated body fluid (SBF), was seen to decrease in the presence of serum. XRD showed more rapid HA formation on Bioglass particles, compared to that forming on 70S30C particles, however TEM showed similar size and frequency of the needle-like crystals. Phosphate reduction in SBF was similar for Bioglass and 70S30C. Calcium carbonate formation was more likely on the phosphate-free sol-gel glass than on Bioglass.

In vitro degradation studies on bioactive calcium fluoroborophosphate glasses mixed with some modifier oxides-influence of therapeutically active vanadium ions

The main objective of the study is to investigate the influence of therapeutically active vanadium ions on the in vitro bio-active properties of calcium oxy fluoro borophosphate glasses mixed with different modifier oxides viz., BaO, SrO, ZnO and MgO. The investigations mainly include the degradation studies of the chosen glasses in simulated body fluid (SBF) for a prolonged period (about 800 h). The rate of degradation was estimated by measuring the weight loss of the samples and by measuring the pH of the residual SBF solution at regular intervals of immersion time. During the immersion of the samples in SBF solution, a thin layer of crystalline hydroxy apatite layer (HAp) is observed to develop on the surface of the glass samples. The comparison of the results of XRD, SEM, EDS and IR spectral studies of pre and post immersed samples confirmed the formation of HAp layer embedded with calcium vanadate crystal phases. From the XRD studies it is understood that the magnitude of HAp layer developed on the surface of the samples is the highest for BaO modifier mixed glasses. The optical absorption as well as EPR spectral studies of pre and post immersed samples confirmed that vanadium ions existed in different oxidation states, mainly in V4+ and V5+ states, in the bulk glass samples. The ratio of the concentration of these two ions is predicted to be different for different modifier oxides mixed glasses and such variation is predicted to play a vital role in the variations of the magnitude of HAp layer formed on the surface of the samples. The bioactivity of the samples is estimated from the qualitative information on the magnitude of HAp layer formed on the surface of the samples and also the degradability of the samples in SBF solution which is estimated by measuring weight loss as well as pH of the residual SBF. The overall analysis of the results of in vitro bioactivity studies (degradability studies together with spectroscopic studies) revealed that among various glasses mixed with different modifier oxides, the glass mixed with BaO is found to be the superior bioactive material. Such glasses may be useful in improving the osteogenic activity in the human body if used as bone implants since it contains HAp layer embedded with calcium vanadate crystal phases. However quantitative in vitro cell culture studies are required to establish this.

Dissolution behaviour of a polyphosphate glass in simulated body fluid

In this work, the dissolution behavior of a polyphosphate glass, with the composition 45P2O5?3SiO2?25K2O?15CaO?10MgO?ZnO?MnO (mol %), in simulated body fluid (SBF) at a temperature of 37 ?C for different times was studied. Two powder sizes of the glass (granulation: 0.1?0.3 and 0.3?0.65 mm) and the bulk glass were investigated. The dissolution experiments were conducted under stationary conditions. Changes in the normalized mass release, normalized concentration of ions, pH values, and surface morphology were determined as a function of the dissolution time. The initial rates of glass powder dissolution and leaching of ions, as well as the diffusion coefficient of cations and the releasing rate of ions, during the hydrolysis process of glass were determined. It was shown that the investigated phosphate glass dissolves in SBF incongruently, with neither precipitation nor the formation of newly potentially toxic compounds, in a dissolution period 720 h.

Bioactive Glasses with Low Ca/P Ratio and Enhanced Bioactivity.

Three new silica-based glass formulations with low molar Ca/P ratio (2–3) have been synthesized. The thermal properties, the crystalline phases induced by thermal treatments and the sintering ability of each glass formulation have been investigated by simultaneous differential scanning calorimetry-thermogravimetric analysis (DSC-TG), X-ray diffraction (XRD) and hot stage microscopy (HSM). The glasses exhibited a good sintering behavior, with two samples achieving shrinkage of 85%–95% prior to crystallization. The bioactivity of the glasses in simulated body fluid (SBF) has been investigated by performing XRD and Fourier transform infrared spectroscopy (FTIR) on the samples prior and after immersion. The glasses with lower MgO contents were able to form a fully crystallized apatite layer after three days of immersion in simulated body fluid (SBF), while for the glass exhibiting a higher MgO content in its composition, the crystallization of the Ca–P layer was achieved after seven days. The conjugation of these properties opens new insights on the synthesis of highly bioactive and mechanically strong prosthetic materials.

Effect of MgO on bioactivity, hardness, structural and optical properties of SiO2–K2O–CaO–MgO glasses

Glass composition 55SiO2–10K2O–(35−x)CaO–xMgO is synthesized by a melt quench technique. The as quenched and simulated body fluid (SBF) soaked glasses are investigated for their bioactive, optical and structural properties. These properties are discussed in the light of the role of MgO. The hardness increases with content of MgO instead of CaO. No remarkable change in the XRD pattern has been observed in unsoaked and soaked glasses in SBF for 28 days. The pH values initially increases rapidly and later stage of soaking it changes slowly. The soaked glasses exhibit some new FTIR bands as compared to virgin glasses. The optical band gap of the soaked samples is higher and Urbach energy lower with respect to pristine glass powder. The ion released into the SBF solution and consequent pH rise are maximum for glass sample containing minimum amount of Mg. The higher MgO containing glasses show low dissolution rate of Mg2+, K+ and Ca2+ cations. Among all the glasses G2 show highest bioactivity.

Sol Gel Synthesis and In Vitro Evaluation of Apatite Forming Ability of Silica-Based Composite Glass in SBF

In this study, xerogel glass based on SiO-CaO-PO4 was synthesized by a low temperature acid catalysed sol-gel route. The in vitro evaluation of apatite forming ability for the glass was conducted in simulated body fluid (SBF) solution as the glasses were immersed for duration of 1, 7, 24 hours and 7 days. The XRD analysis showed that the glass formed semi-crystalline structure when sintered at 1000oC and consisted of Ca2O7P2 and Ca2O4Si phases. Image captured using FESEM showed the apatite-like structures were eventually formed on the glass top surface in small numbers after the glass immersed in SBF for only an hour. The numbers of the apatite structures were continuously grown with the increase period of immersion time. The apatite structure mostly covered on top of the glass surface after 24 hours of immersion and continuously growth into bone-like apatite structure when immersed for 7 days in the SBF. The apatite layer formed on the surface of the glass was confirmed as crystalline structure of hydroxyl-carbonate-apatite (HCA) as revealed by the complimentary results of EDS, XRD and FTIR analysis.

Processing and characterization of novel borophosphate glasses and fibers for medical applications

In this paper, we investigate the effect of P2O5 substitution by B2O3 in the (50−x)P2O5·20CaO·20SrO·10Na2O·x B2O3 glass system (x from 0 to 5mol%) on the thermal and structural properties and also on the glass reactivity in simulated body fluid. The goal is to develop new glass candidates for biomedical glass fibers. The addition of B2O3 at the expense of P2O5 increases the refractive index of the glass and also the thermal stability of the glass indicating that these glasses are promising glasses for fiber drawing. Thus, within such glass composition, the core of a core–clad fiber has a larger concentration of B2O3 than the clad of the fiber to enable the light to propagate inside the core. All the investigated glasses form a calcium phosphate layer at their surface when immersed in simulated body fluid. It was found that small addition of B2O3 (1.25mol%) leads to a decrease in the initial dissolution rate and a delayed layer formation. However, with increasing B2O3 content, the chemical durability decreased slightly but was higher than for the B-free glass. In addition, formation of the calcium phosphate layer was further delayed. This suggests that small contents of B2O3 led to formation of P–O–B bonds and only few BO4 units, increasing the chemical durability. At higher B2O3 contents, the amount of BO4 units increases which makes the glass network slightly more prone to be hydrolyzed. Thus, formation of BO4 units induced by the addition of B2O3 at the expense of P2O5 reduces the reactivity of the glass in SBF. Borophosphate fibers were successfully drawn from preform. As expected from the bioresponse of the bulk glasses in simulated body fluid, the reduction in the intensity of the light transmitted is less and slower in a borophosphate fiber than in a phosphate fiber upon immersion.

Improvement of bio-corrosion resistance for Ti42Zr40Si15Ta3 metallic glasses in simulated body fluid by annealing within supercooled liquid region.

The effects of the nanocrystalline phases on the bio-corrosion behavior of highly bio-friendly Ti42Zr40Si15Ta3 metallic glasses in simulated body fluid were investigated, and the findings are compared with our previous observations from the Zr53Cu30Ni9Al8 metallic glasses. The Ti42Zr40Si15Ta3 metallic glasses were annealed at temperatures above the glass transition temperature, Tg, with different time periods to result in different degrees of α-Ti nano-phases in the amorphous matrix. The nanocrystallized Ti42Zr40Si15Ta3 metallic glasses containing corrosion resistant α-Ti phases exhibited more promising bio-corrosion resistance, due to the superior pitting resistance. This is distinctly different from the previous case of the Zr53Cu30Ni9Al8 metallic glasses with the reactive Zr2Cu phases inducing serious galvanic corrosion and lower bio-corrosion resistance. Thus, whether the fully amorphous or partially crystallized metallic glass would exhibit better bio-corrosion resistance, the answer would depend on the crystallized phase nature.

Structure, dielectric and bioactivity of P2O5–CaO–Na2O–B2O3 bioactive glass

Bioactive phosphate glasses have been widely investigated for bone repair. Phosphate glass system of 47P2O5–30.5CaO–(22.5−x)Na2O–xB2O3 has been prepared by melt quenching technique. From the Raman analysis, it is confirmed that phosphate network form metaphosphate structure. Bioactivity of the glass is studied by immersing the prepared glass in simulated body fluid (SBF). All the glasses exhibited bioactivity after soaking in SBF. Addition of B2O3 to the glass by replacing the Na2O produces considerable effect on the dielectric and bioactivity of the glass. Ion dynamics are also analyzed through imaginary modulus and imaginary dielectric permittivity.

Influence of SrO substitution for CaO on the properties of bioactive glass S53P4

Commercial melt-quenched bioactive glasses consist of the oxides of silicon, phosphorus, calcium and sodium. Doping of the glasses with oxides of some other elements is known to affect their capability to support hydroxyapatite formation and thus bone tissue healing but also to modify their high temperature processing parameters. In the present study, the influence of gradual substitution of SrO for CaO on the properties of the bioactive glass S53P4 was studied. Thermal analysis and hot stage microscopy were utilized to measure the thermal properties of the glasses. The in vitro bioactivity and solubility was measured by immersing the glasses in simulated body fluid for 6h to 1week. The formation of silica rich and hydroxyapatite layers was assessed from FTIR spectra analysis and SEM images of the glass surface. Increasing substitution of SrO for CaO decreased all characteristic temperatures and led to a slightly stronger glass network. The initial glass dissolution rate increased with SrO content. Hydroxyapatite layer was formed on all glasses but on the SrO containing glasses the layer was thinner and contained also strontium. The results suggest that substituting SrO for CaO in S53P4 glass retards the bioactivity. However, substitution greater than 10mol% allow for precipitation of a strontium substituted hydroxyapatite layer.

87Sr Solid-State NMR as a Structurally Sensitive Tool for the Investigation of Materials: Antiosteoporotic Pharmaceuticals and Bioactive Glasses

Strontium is an element of fundamental importance in biomedical science. Indeed, it has been demonstrated that Sr(2+) ions can promote bone growth and inhibit bone resorption. Thus, the oral administration of Sr-containing medications has been used clinically to prevent osteoporosis, and Sr-containing biomaterials have been developed for implant and tissue engineering applications. The bioavailability of strontium metal cations in the body and their kinetics of release from materials will depend on their local environment. It is thus crucial to be able to characterize, in detail, strontium environments in disordered phases such as bioactive glasses, to understand their structure and rationalize their properties. In this paper, we demonstrate that (87)Sr NMR spectroscopy can serve as a valuable tool of investigation. First, the implementation of high-sensitivity (87)Sr solid-state NMR experiments is presented using (87)Sr-labeled strontium malonate (with DFS (double field sweep), QCPMG (quadrupolar Carr-Purcell-Meiboom-Gill), and WURST (wideband, uniform rate, and smooth truncation) excitation). Then, it is shown that GIPAW DFT (gauge including projector augmented wave density functional theory) calculations can accurately compute (87)Sr NMR parameters. Last and most importantly, (87)Sr NMR is used for the study of a (Ca,Sr)-silicate bioactive glass of limited Sr content (only ~9 wt %). The spectrum is interpreted using structural models of the glass, which are generated through molecular dynamics (MD) simulations and relaxed by DFT, before performing GIPAW calculations of (87)Sr NMR parameters. Finally, changes in the (87)Sr NMR spectrum after immersion of the glass in simulated body fluid (SBF) are reported and discussed.

Surface reactions of bioactive glasses in buffered solutions

Abstract In vitro bioactivity of glasses is usually measured in buffered solutions whereby a formation of a hydroxyapatite layer on the surface is taken as an indication of the bioactivity. In this work we compare the layer formation on three glasses in simulated body fluid, Tris buffer solution, sodium phosphate buffered saline and osteoblast medium. Two of the glasses are known bioactive glasses, 45S5 (45 wt.% SiO 2 ) and S53P4 (53 wt.% SiO 2 ), while the third is an experimental composition with a higher silica content (68 wt.% SiO 2 ). Plates of the glasses were immersed in the solutions at 37 °C for different times up to two weeks. The results showed clear differences between the layer developments on the three glasses in the different solutions. The results indicated that the relative order of the reactivity depended on the solution. Thus, results gained in different solutions for different glasses cannot be directly compared.