Bioactive glasses in the system CaO–B2O3–P2O5: Preparation, structural study and in vitro evaluation (original) (raw)
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Revista de Chimie
This paper shows the experimental results of two compositional phosphocalcic glasses: 50% SiO2 - 45% CaO - 5% P2O5 and 47% SiO2 - 45% CaO - 5% P2O5 - 3% Ag2O obtained through sol-gel method. In order to study their bioactivity, the two compositions were structural analyzed by X-ray diffraction method. In this case the apatite formation was highlighted after 14 days of soaked in simulated body fluid, but also other compounds (CaCO3, AgCl and Ag) resulting from the same process were highlighted. The first glass composition is more bioactive than composition doped with silver. The pores of the hydrated silica network are partially clogged by the AgCl formed, which can reduce the rate of hydroxyapatite formation but this process does not cancel the bioactivity of the doped glass. The functional groups present in the structure of those two glasses before and after soaking (PO43-, CO32- and HO-) were highlighted by the Fourier Transform Infrared Spectroscopy (FTIR). The elemental chemical...
Structure and Stability of High CaO- and P2O5-Containing Silicate and Borosilicate Bioactive Glasses
The Journal of Physical Chemistry B, 2019
The present work elucidates about the structure of bioactive glasses having chemical compositions expressed as (mol %) (50.0-x) SiO 2 x B 2 O 3 9.3 Na 2 O 37 CaO 3.7 P 2 O 5 , where x = 0.0, 12.5, 25 and 37.5, and establishes a correlation between the structure and thermal stability. The structural modifications in the parent boron free glass (B0) with the gradual substitutions of B 2 O 3 for SiO 2 are assessed by Raman and 29 Si, 31 P, 11 B and 23 Na magic angle spinning (MAS)-nuclear magnetic resonance (NMR) spectroscopies. The structural studies reveal the presence of Q 2 Si and Q 3 Si structural units in both silicate and borosilicate glasses. However, Q 4 Si (3B) units additionally form upon incorporating B 2 O 3 in B0 glass. B-containing silicate glasses exhibit both 3 coordinated boron (B III) and 4 coordinated boron (B IV) units. The 31 P MAS-NMR studies reveal that the majority of phosphate species exist as isolated orthophosphate (Q 0 P) units. The incorporation of B 2 O 3 in B0 glass increases the crosslinking between the SiO 4 and BO 4 structural units. However, incorporation of B 2 O 3 lowers the glass thermal stability (ΔT) as shown by differential scanning calorimetry (DSC). Although both silicate and borosilicate glasses exhibit good in vitro apatite forming ability and cell compatibility, the bactericidal action against E.coli bacteria is more evident in borosilicate glass in comparison to silicate base glass. The controlled release of (BO 3) 3 ions from boron modified bioactive glasses improves both the cell proliferation and the antibacterial properties, making them promising for hard tissue engineering applications.
Journal of the American Ceramic Society, 2008
The conversion of bioactive glass to a calcium phosphate material, typically hydroxyapatite (HA), by solution-precipitation reactions in aqueous phosphate solution, has been commonly reported. This paper describes the structural and compositional characteristics of the calcium phosphate material formed during the early-stage conversion (o5 h) of a borosilicate glass (designated H12) in aqueous phosphate solution. Disks of H12 glass were reacted with 0.25M K 2 HPO 4 solution with a starting pH 5 7.0 at 371C. The structure and composition of the product layer were characterized using thin film X-ray diffraction, scanning electron microscopy, and Fourier transform infrared reflectance spectroscopy. For reaction times o5 h, the results indicated the formation of brushite (CaHPO 4 . 2H 2 O) with coarse, plate-like crystals. In comparison, the formation of HA with small needle-like crystals was found at later times. This early-stage formation of brushite has not been reported in previous studies of converting bioactive silicate and borate glasses in aqueous phosphate solution.
BioMed Research International, 2013
In this study eight different phosphate-based glass compositions were prepared by melt-quenching: four in the (P 2 O 5 ) 45 -(CaO) 16 -(Na 2 O) 15− -(MgO) 24 -(B 2 O 3 ) system and four in the system (P 2 O 5 ) 50 -(CaO) 16 -(Na 2 O) 10− -(MgO) 24 -(B 2 O 3 ) , where = 0, 1, 5 and 10 mol%. The effect of B 2 O 3 addition on the thermal properties, density, molar volume, dissolution rates, and cytocompatibility were studied for both glass systems. Addition of B 2 O 3 increased the glass transition ( g ), crystallisation ( c ), melting ( m ), Liquidus ( L ) and dilatometric softening ( d ) temperature and molar volume ( m ). The thermal expansion coefficient ( ) and density ( ) were seen to decrease. An assessment of the thermal stability of the glasses was made in terms of their processing window (crystallisation onset, c,ons minus glass transition temperature, g ), and an increase in the processing window was observed with increasing B 2 O 3 content. Degradation studies of the glasses revealed that the rates decreased with increasing B 2 O 3 content and a decrease in degradation rates was also observed as the P 2 O 5 content reduced from 50 to 45 mol%. MG63 osteoblast-like cells cultured in direct contact with the glass samples for 14 days revealed comparative data to the positive control for the cell metabolic activity, proliferation, ALP activity, and morphology for glasses containing up to 5 mol% of B 2 O 3 .
Journal of Materials Science-materials in Medicine, 2011
New compositions of bioactive glasses are proposed in the CaO–MgO–SiO2–Na2O–P2O5–CaF2 system. Mineralization tests with immersion of the investigated glasses in simulated body fluid (SBF) at 37°C showed that the glasses favour the surface formation of hydroxyapatite (HA) from the early stages of the experiments. In the case of daily renewable SBF, monetite (CaHPO4) formation competed with the formation of HA. The influence of structural features of the glasses on their mineralization (bioactivity) performance is discussed. Preliminary in vitro experiments with osteoblasts’ cell-cultures showed that the glasses are biocompatible and there is no evidence of toxicity. Sintering and devitrification studies of glass powder compacts were also performed. Glass-ceramics with attractive properties were obtained after heat treatment of the glasses at relatively low temperatures (up to 850°C).
Bioactive calcium phosphate-based glasses and ceramics and their biomedical applications: A review
Journal of tissue engineering
An overview of the formation of calcium phosphate under in vitro environment on the surface of a range of bioactive materials (e.g. from silicate, borate, and phosphate glasses, glass-ceramics, bioceramics to metals) based on recent literature is presented in this review. The mechanism of bone-like calcium phosphate (i.e. hydroxyapatite) formation and the test protocols that are either already in use or currently being investigated for the evaluation of the bioactivity of biomaterials are discussed. This review also highlights the effect of chemical composition and surface charge of materials, types of medium (e.g. simulated body fluid, phosphate-buffered saline and cell culture medium) and test parameters on their bioactivity performance. Finally, a brief summary of the biomedical applications of these newly formed calcium phosphate (either in the form of amorphous or apatite) is presented.
Journal of Materials Science-materials in Medicine, 2010
The conversion of glass to a hydroxyapatite (HA) material in an aqueous phosphate solution is used as an indication of the bioactive potential of the glass, as well as a low temperature route for preparing biologically useful materials. In this work, the effect of varying concentrations of pyrophosphate ions in the phosphate solution on the conversion of a calcium–lithium–borate glass to HA was investigated. Particles of the glass (150–355 μm) were immersed for up to 28 days in 0.25 M K2HPO4 solution containing 0–0.1 M K4P2O7. The kinetics of degradation of the glass particles and their conversion to HA were monitored by measuring the weight loss of the particles and the ionic concentration of the solution. The structure and composition of the conversion products were analyzed using X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. For K4P2O7 concentrations of up to 0.01 M, the glass particles converted to HA, but the time for complete conversion increased from 2 days (no K4P2O7) to 10 days (0.01 M K4P2O7). When the K4P2O7 concentration was increased to 0.1 M, the product consisted of an amorphous calcium phosphate material, which eventually crystallized to a pyrophosphate product (predominantly K2CaP2O7 and Ca2P2O7). The consequences of the results for the formation of HA materials and devices by the glass conversion route are discussed.
Journal of Materials Science, 2017
B 2 O 3 /SiO 2 substitution in 55S4.3 bioactive glasses with 5 mol% of SrO has been synthesized and characterized to understand their structure and bioactivity as a function of composition by combining experimental and computer simulation techniques. Raman spectrometry, X-ray diffraction (XRD) and Fourier transform infrared spectrometry (FTIR) were utilized to characterize the structural changes induced by boron content and to identify the formation of hydroxyapatite (HAp). In vitro bioactivity tests were performed in simulated body fluid with a fixed glass mass to solution volume ratio and a particle size range. Needle-like HAp was found to form on the surface of the 55S4.3 with SrO sample from scanning electron microscopy and confirmed from XRD and FTIR. In addition to the experimental efforts, these glasses were also simulated using classical molecular dynamics simulations with partial charge potentials and recently developed parameters for boron oxide to understand their short-and mediumrange structures. The glasses from simulations were analyzed in terms of the local structure around the glass network formers, especially the boron coordination number, and found to agree well with theoretical models. The mediumrange structural information such as Q n distribution and network connectivity was also obtained and used to understand the compositional dependence of property and bioactivity. The results show that additional boron oxide increased the network connectivity of the 55S4.3 glass and inhibited or delayed the formation of HAp in vitro.
Bioactivity evolution of calcium-free borophosphate glass with addition of titanium dioxide
Journal of Non-Crystalline Solids, 2015
The addition of titanium dioxide in the bioactive phosphate glass composition is intended to control the rate of dissolution, but nevertheless, the TiO 2 presence may affect the glass bioactivity. Therefore, in this study the bioactivity response of the calcium-free borophosphate glasses by varying the titania content was evaluated. The glass system belonging to the compositional range (100 − x)[10B 2 O 3 ·30Na 2 O⋅60P 2 O 5 ]·xTiO 2 , with 0 ≤ x ≤ 12 mol%, was obtained by the conventional melt quenching method and the structural changes were assessed by performing X-ray diffraction, Raman and Fourier Transform Infrared measurements. The Raman and Fourier Transform Infrared spectra show the presence of Ti\O\P bonds once the titania was added to the glass composition. This result indicates that structural rearrangements take place in the main phosphate network due to the replacing of P\O\P by Ti\O\P bonds. Regarding in vitro assessment of bioactivity, the results obtained by analysing the information derived from X-ray diffraction, Fourier Transform Infrared, Scanning Electron Microscopy and Energy Dispersive X-ray spectroscopy point out that the increase of titanium dioxide content has as consequence the occurrence of a more pronounced apatite layer. However, in the case of the samples with the highest TiO 2 content, the crystallization of apatite layer does not occur in the first 14 days. The solubility test data indicated a clear decrease of glass solubility for titania amounts of 8 and 12 mol%.
Journal of Materials Science: Materials in Medicine, 2013
Bioactive glasses and glass-ceramics of the SiO 2 -CaO-P 2 O 5 system were synthesised by means of a solgel method using different phosphorus precursors according to their respective rates of hydrolysis-triethylphosphate (OP(OC 2 H 5 ) 3 ), phosphoric acid (H 3 PO 4 ) and a solution prepared by dissolving phosphorus oxide (P 2 O 5 ) in ethanol. The resulting materials were characterised by differential scanning calorimetry and thermogravimetry, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy and by in vitro bioactivity tests in acellular simulated body fluid. The different precursors significantly affected the main steps of the synthesis, beginning with the time required for gel formation. The most striking influence of these precursors was observed during the thermal treatments at 700-1,200°C that were used to convert the gels into glasses and glass-ceramics. The samples exhibited very different mineralisation behaviours; especially those prepared using the phosphoric acid, which had a reduced onset temperature of crystallisation and an increased resistance to devitrification. However, all resulting materials were bioactive. The in vitro bioactivity of these materials was strongly affected by the heat treatment temperature. In general, their bioactivity decreased with increasing treatment temperature. For crystallised samples obtained above 900°C, the bioactivity was favoured by the presence of two crystalline phases: wollastonite (CaSiO 3 ) and tricalcium phosphate (a-Ca 3 (PO 4 ) 2 ).