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1
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Enhanced apatite precipitation on a biopolymer-coated bioactive glass

100%
Araújo M., Miola M., Venturello A., Baldi G., Perez J., Verné E.
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vol. 1
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issue 1
EN
In this work, sintered pellets of a silica-based bioactive glass were dip-coated with a biocompatible natural-derived polymer in order to investigate the influence of the organic coating on the glass bioactivity. After the sintering process optimization, uncoated and coated pellets have been characterized by means of scanning electron microscopy with energy dispersive spectroscopy (SEM, EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and pH measurements, after the immersion in a simulated body fluid (SBF). An increased apatite forming ability and a better control of the pH during soaking of the samples in SBF were observed in the presence of the biopolymer. This result opens a new insight on the simple fabrication of highly bioactive hybrid inorganic-organic materials for medical applications.
2
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Synthesis of poly(vinyl alcohol) - hydroxyapatite composites and characterization of their bioactivity

100%
Balgová Z., Palou M., Wasserbauer J., Kozánková J.
Open Chemistry
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2013
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vol. 11
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issue 9
1403-1411
EN
Abstract A series of poly(vinyl alcohol) membranes reinforced with hydroxyapatite in various weight percent - 0%, 10%, 20%, 30%, 40% and 50% were prepared. Hydroxyapatite was prepared by a sol-gel procedure using diammonium hydrogen phosphate and calcium nitrate tetrahydrate as starting materials in an alkaline aqueous environment and then mixed with a solution of poly(vinyl alcohol), which was prepared by dissolving it in water at 85°C. The different mixtures were cast in a mould and evaporated for 7 days at a temperature of 30°C to obtain 1 mm thin membranes. FTIR spectroscopy was used to identify the different functional groups in the composites. The surface morphology was examined using a scanning electron microscope. In vitro bioactivity tests in Simulated Blood Fluid were performed for up to 28 days, especially for the membrane containing 50 wt.% HA. SEM was used to characterise the surface microstructure of biocomposite membranes before and after soaking in SBF. It was observed that the formation of clusters in membranes increases with increasing amount of HA. The clusters are formed due to agglomeration and crystal growth of HA particles during drying of the membranes. The in vitro bioactivity was found to increase with soaking time of biocomposite materials in simulated blood fluid. Graphical abstract [...]
3
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Potential applications of fluorhydroxyapatite as biomaterials in medicine

100%
Vitkovič M., Noaman M., Palou M., Jantová S.
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EN
The present work was undertaken to investigate the bioactivity and cytotoxicity of fluorhydroxyapatite ceramics. The bioactivity was evaluated by in vitro testing in simulated body fluid (SBF), in which ion concentrations are almost identical with inorganic ion concentrations of human blood plasma. Pellets of FA, HA and FHA were immersed in SBF for 48 hours, 1 week and 4 weeks at 36.5°C. Changes of the surface microstructure of the samples were observed by scanning electron microscopy (SEM). 48 hours and one week immersion in SBF did not result in any substantial progress in bioactivity. After 4 weeks in SBF a new biologically active layer was created on the surface of the biomaterials. In addition, the embryonal mouse fibroblast cell line NIH-3T3 was used for a comparative study of basal cytotoxicity of FHA, HA and FA discs. The sensitivity of these cells for tested biomaterials was evaluated on the basis of two cytotoxic end points: cell proliferation and cell morphology. The basal cytotoxicity of FHA, FA and HA discs was measured by a direct contact method. After 24, 48 and 72 hours, the cell growth was evaluated by direct counting of non-affected cells and cells treated by biomaterials. After 72 hours of biomaterials treatment, about 25% inhibition of cell number and unchanged morphology was found. [...]
4
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Influence of textural properties on biomineralization behavior of mesoporous bioactive glasses

88%
Kumar A., Murugavel S.
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vol. 1
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issue 1
EN
A new method of calcination for the sol-gel derived bioactive glass sample has been developed to produce superior textural and bioactive properties. Based on this method, mesoporous 67.4 SiO2-25 Na2O-5 CaO- 2.6 P2O5 (mol.%) bioactive glasses (MBGs) have been synthesized through acid assisted sol-gel technique followed by evaporation induced self-assembly (EISA) process, commonly used for obtaining bioactive glasses. Moreover, the use of microwave irradiation has been compared with that of conventional heat treatment for a particular quaternary composition,which has allowed the homogeneous spatial distribution of heat and to obtain smaller, uniform pore sizes with high surface area. The distinctions between the two methods of calcination have been observed in the structural, morphology and textural characteristics. The superior textural characteristics have allowed the rapid dissolution of MBGs followed by development of nanocrystalline hydroxycarbonate apatite (HCA) layer. In vitro bioactive analyses on both MBGs have revealed a rapid formation HCA layer with distinct behavior on the biomineralization process. The difference in the behavior of biomineralization process is attributed to the kinetics of supersaturation of the biological medium.
5
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Mechanism and kinetics of glass-ceramics formation in the LiO2-SiO2-CaO-P2O5-CaF2 system

88%
Palou M., Kuzielová E., Vitkovič M., Noaman M.
Open Chemistry
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2009
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vol. 7
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issue 2
228-233
EN
Two glasses based on lithium disilicate (LS2), with and without fluorapatite (FA), were synthesised in the Li2O-SiO2-CaO-P2O5-CaF2 system with P2O5: CaO: CaF2 ratios corresponding to fluorapatite. Glass-ceramics have then been prepared by thermal treatment. The mechanism and kinetics of crystallization as functions of grain size and rate of heating were investigated using thermal analysis methods. The smaller particles crystallize preferentially by surface crystallization, which is replaced by volume crystallization at larger particle sizes. Inclusion of FA in the LS2 favours crystallization through the surface mechanism. The onset limit for volume crystallization replacing the surface mechanism is at about 0.3 mm for pure LS2 glass and 0.9 mm for glass containing FA. The calculated activation energies of the glasses (299 ± 1 kJ mol-1 for pure LS2 glass and 288 ± 7 kJ mol−1 for glass containing FA according to Kissinger, or 313 ± 1 kJ mol-1 for pure LS2 glass and 303 ± 8 kJ mol-1 for glass containing FA according to Ozawa) indicate that the tendency of the glasses to crystallize is supported by the FA presence. Bioactivity of all samples has been proved in vitro by the formation of new layers of apatite-like phases after soaking in SBF. [...]
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