57 research outputs found
Polylactic acid-phosphate glass composite foams as scaffolds for tissue engineering
Phosphate glass (PG) of the composition 0.46(CaO)-0.04(Na(2)O)- 0.5(P(2)O(5)) was used as filler in poly-L-lactic acid (PLA) foams developed as degradable scaffolds for bone tissue engineering. The effect of PG on PLA was assessed both in bulk and porous composite foams. Composites with various PG content (0, 5, 10, and 20 wt %) were melt-extruded, and either compression-molded or foamed through supercritical CO(2). Dynamic mechanical analysis on the bulk composites showed that incorporating 20 wt % PG resulted in a significant increase in storage modulus. Aging studies in deionized water in terms of weight loss, pH change, and ion release inferred that the degradation was due to PG dissolution, and dependent on the amount of glass in the composites. Foaming was only possible for composites containing 5 and 10 wt % PG, as an increase in PG increased the foam densities; however, the level of porosity was maintained above 75%. PLA-T(g) in the foams was higher than those obtained for the bulk. Compressive moduli showed no significant reinforcement with glass incorporation in either expansion direction, indicating no anisotropy. Biocompatibility showed that proliferation of human fetal bone cells was more rapid for PLA compared to PLA-PG foams. However, the proliferation rate of PLA-PG foams were similar to those obtained for foams of PLA with either hydroxyapatite or beta-tricalcium phosphate
Lichenological exploration of Algeria: historical overview and annotated bibliography, 1799-2013
yesDespite more than two centuries of almost uninterrupted surveys and studies of Algerian lichenology, the history and lichen diversity of Algeria are still poorly understood. During the preparation of a forthcoming checklist of Algerian lichens it was considered necessary to provide the present historical overview of lichenological exploration of the country from 1799 to 2013, supported by a reasonably comprehensive annotated bibliography of 171 titles
Viscerocutaneous form of loxoscelism and erythrocyte glucose-6-phosphate deficiency
In a period of time of five years, all patients who exhibited viscerocutaneous form of loxoscelism were investigated for erythrocyte glucose-6-phosphate deficiency, and in two patients out of seven it was found this deficiency. This finding suggests that this genetical enzyme deficiency could account for the hemolysis after Loxosceles bite, at least in some of the cases
Dissolution and bioactivity of a sol-gel derived borate glass in six different solution media
Sol-gel derived bioactive borate glasses (SGBGs) rapidly convert to hydroxycarbonated apatite (HCA) in simulated body fluid (SBF), in vitro. While previous studies have examined the influence of processing and composition on bioactivity, the effect of the in vitro dissolution media has not been well examined for these glasses. In this study, the mineral conversion of a SGBG substituted 45S5 Bioglass® formulation (“B46”, (46.1)B2O3-(26.9)CaO-(24.4)Na2O-(2.6)P2O5, mol%), was examined in six different dissolution media: SBF, tris(hydroxymethyl)aminomethane (TRIS, pH 7.4) buffer, Dulbecco’s phosphate buffered saline (PBS, 1X), Dulbecco’s Modified Eagle Medium (DMEM, 1X), 0.9% Saline (SAL), and deionized water (DIW) at 1.5 mg/mL for 10 min, 2h, and 1d. All media underwent a rapid increase in pH as a result of glass dissolution and ion release. B46 in SBF, TRIS, and PBS converted to HCA while B46 in DMEM, SAL, and DIW converted to calcite according to attenuated total reflectance-Fourier-transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The ratio of B46 to SBF was also examined at 3, 6, 12, and 24 mg/mL for 1d. These results help elucidate the dissolution and mineral conversion of borate glasses and help provide insights into optimizing pre-conditioning treatments for both in vitro and in vivo analyses
Highly Bioactive Sol-Gel-Derived Borate Glasses
Attributable to their low chemical
durability, borate-based glasses
have been demonstrated to convert rapidly to hydroxy-carbonated apatite
(HCA), the inorganic component of bone. However, the effect of sol-gel
processing on the bioactivity of borate-based glasses has not been
investigated. In this study, the gel and glass forming abilities of
six different borate-based glass formulations with borate content
ranging from 36 to 61 mol % and based on a previously studied four
component melt-derived glass system [(46.1)ÂB<sub>2</sub>O<sub>3</sub>–(26.9)ÂCaO–(24.4)ÂNa<sub>2</sub>O–(2.6)ÂP<sub>2</sub>O<sub>5</sub>; mol %] were investigated. Compared to melt-quench,
sol-gel processing fabricated nanoporous glass particles with at least
2 orders of magnitude greater values for specific surface areas and
total pore volumes, which translated to dramatically higher aqueous
interaction and ion release rates. Surprisingly, when immersed in
simulated body fluid, HCA conversion was achieved in as little as
3 h for sol-gel derived borate based glasses, demonstrating a 25-fold
increase in mineralization rate when compared to melt derived equivalents.
The ability of the sol-gel derived borate-based glasses to rapidly
convert to bone-like HCA holds promise in numerous potential tissue
engineering applications, including the repair and augmentation of
mineralized tissues
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