Bioactive Glasses with Low Ca/P Ratio and Enhanced Bioactivity.
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ABSTRACT:
SUBMITTER: Araujo M
PROVIDER: S-EPMC5502799 | biostudies-other | 2016 Mar
REPOSITORIES: biostudies-other
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Project description:Considering the increase in patients who suffer from osteoporosis and the bone defects that occur in these patients, bone tissue regeneration is a promising option to solve this problem. To achieve a synergistic effect between the synthesis of a proper structure and bioactive/pharmaceutical activity, ions with a physiological effect can be added to silica structures, such as Ca2+, thanks to its bioactive behavior, and Ga3+ for its antibacterial and anticancer action. In this work, the synthesis of large pore mesoporous silica (LPMS), potential bioactive glasses containing Ca2+ and Ga3+, has been studied. Corresponding structures, in terms of composition, have been synthesized following the Sol-Gel EISA (Evaporation Induced Self-Assembly) process (obtaining Classical Mesoporous Silica, MS). Pore structure characterization of LPMSs and MSs has been performed using N2 adsorption/desorption and Hg-porosimetry, showing the presence of pores for LPMSs in the range of 20-60 and 200-600 nm. Nisin, a polycyclic antibacterial peptide, has been used for load tests. The load and release tests performed highlight a higher loading and releasing, doubled for LPMSs if compared to MSs. To confirm the maintenance of the structure of LPMSs and their mechanical strength and resistance, scanning electron microscopy images were acquired before and after release tests. Ca and Ga release in SBF has been studied through inductively coupled plasma-optical emission spectroscopy (ICP-OES), showing a particularly high release of these ions performed with LPMSs. The bioactive behavior of Ca-containing structures has been confirmed using FT-IR (Fourier-transform infrared spectroscopy), SEM-EDS (Scanning Electron Microscope-Energy Dispersive Spectroscopy), and X-ray powder diffraction (XRDP). In conclusion, LPMSs showed better loading and releasing properties compared with classical MS and better release in terms of active ions. In addition, it has also been demonstrated that LPMSs have bioactive behavior (a well-known characteristic of MSs).
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Project description:SiO₂-CaO-P₂O₅-based mesoporous bioactive glasses (MBGs) were synthesized by spray pyrolysis in this study. Three commonly used non-ionic tri-block copolymers (L121, P123, and F127) with various lengths of hydrophilic chains were applied as structural templates to achieve different pore sizes. A mesoporous structure was observed in each as-prepared specimen, and the results showed that the L121-treated MBG had the largest pore size. The results of bioactivity tests indicated that the growth of hydroxyapatite is related to the pore size of the materials.
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Project description:Photothermal therapy (PTT), an emerging tumor treatment technology, has attracted tremendous interest, but excessive heat will cause damage to surrounding healthy tissues. Therefore, in situ temperature monitoring during PTT is of great importance to determine optimal treatment temperature and repair heat-damaged normal tissues. Here, we report the preparation of multifunctional Nd-Ca-Si silicate glasses and glass/alginate composite hydrogels that not only have photothermal property but also emit fluorescence under 808-nm laser irradiation, and its fluorescence intensity is linearly correlated with in situ temperature. With this feature, optimal PTT temperature for effective tumor treatment with minimal normal tissue damage can be obtained. In addition, because of the bioactive silicate components, the composite hydrogel has bioactivity to repair heat damage caused by PTT. This implantable multifunctional material with unique temperature monitoring, photothermal function, and wound healing bioactivity can be used for localized thermal therapy.
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Project description:The bioactivity of a series of fluoride-containing sodium-free calcium and strontium phosphosilicate glasses has been tested in vitro. Glasses with high fluoride content were partially crystallised to apatite and other fluoride-containing phases. The bioactivity study was carried out in Tris and SBF buffers, and apatite formation was monitored by XRD, FTIR and solid state NMR. Ion release in solutions has been measured using ICP-OES and fluoride-ion selective electrode. The results show that glasses with low amounts of fluoride that were initially amorphous degraded rapidly in Tris buffer and formed apatite as early as 3 h after immersion. The apatite was identified as fluorapatite by 19F MAS-NMR after 6 h of immersion. Glass degradation and apatite formation was significantly slower in SBF solution compared to Tris. On immersion of the partially crystallised glasses, the fraction of apatite increased at 3 h compared to the amount of apatite prior to the treatment. Thus, partial crystallisation of the glasses has not affected bioactivity significantly. Fast dissolution of the amorphous phase was also indicated. There was no difference in kinetics between Tris and SBF studies when the glass was partially crystallised to apatite before immersion. Two different mechanisms of apatite formation for amorphous or partially crystallised glasses are discussed.
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Project description:Between 2000 and 2015, mortality due to Alzheimer’s disease (AD) increased by 123%. No drugs have yet been approved to stop or slow the progression of AD. A delay of five years in the expression of AD would reduce the incidence rate by half. Thus, it is critical to develop novel prevention strategies to delay the onset of this common disease.
As an ancillary study conducted within a precision-based randomized trial (R01CA149633; PI, Dai & Yu]"), the investigators reduced Ca:Mg ratios to 2.3 through 3-month personalized Mg supplementation among those who consumed high Ca:Mg ratio diet, but otherwise in good general health. The investigators test the hypothesis that actively reducing the Ca:Mg ratio among those aged >65 years who consume high Ca:Mg ratio diets improves cognitive function compared to the placebo arm. The investigators further conduct molecular epidemiologic studies to understand the molecular mechanisms.
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Project description:Adding fluoride into bioactive glasses leads to fluorapatite formation and a decrease in glass transition temperature. Recently, chloride has been introduced into glasses as an alternative to fluoride. The presence of the large chloride ion lowers glass crystallisation tendency and increases glass molar volume, which effectively facilitates glass degradation and bone-bonding apatite-like layer formation. However, there is no information regarding the effect of mixing fluoride and chloride on the glass structure and properties. This study aims to synthesize mixed fluoride and chloride containing bioactive glasses; investigate the structural role of fluoride and chloride and their effects on glass properties. The chloride content measurements reveal that 77-90% of chloride was retained in these Q2 type glasses. Glass transition temperature reduced markedly with an increase in CaX2 (X = F + Cl) content, while the glass molar volume increased. 29Si MAS-NMR results show that the incorporation of mixed fluoride and chloride did not cause significant change in the polymerization of the silicate network and no detectable concentration of Si-F/Cl bands were present. This agrees with 19F NMR spectra showing that F existed as F-Ca(n) species.
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Project description:Mesoporous bioactive glasses (MBGs) are promising materials for regenerative medicine, due to their favorable properties including bioactivity and degradability. These key properties, but also their surface area, pore structure and pore volume are strongly dependent on synthesis parameters and glass stoichiometry. However, to date no systematic study on MBG properties covering a broad range of possible compositions exists. Here, 24 MBG compositions in the SiO2-CaO-P2O5 system were synthesized by varying SiO2 (60-90 mol %), CaO and P2O5 content (both 0 to 40 mol-%), while other synthesis parameters were kept constant. Mesopore characteristics, degradability and bioactivity were analysed. The results showed that, within the tested range of compositions, mesopore formation required a molar SiO2 content above 60% but was independent of CaO and P2O5 content. While mesopore size did not depend on glass stoichiometry, mesopore arrangement was influenced by the SiO2 content. Specific surface area and pore volume were slightly altered by the SiO2 content. All materials were degradable; however, degradation as well as bioactivity, i.e. the ability to form a CaP mineral on the surface, depended on stoichiometry. Major differences were found in early surface reactions in simulated body fluid: where some MBGs induced direct hydroxyapatite crystallization, high release of calcium in others resulted in calcite formation. In summary, degradation and bioactivity, both key parameters of MBGs, can be controlled by glass stoichiometry over a broad range while leaving the unique structural parameters of MBGs relatively unaffected. This allows targeted selection of material compositions for specific regenerative medicine applications.
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Project description:In order to identify new bioactive glasses (BGs) with optimal antioxidant properties, we carried out an evaluation of a series of cerium-doped BGs [Ce-BGs─H, K, and mesoporous bioactive glasses (MBGs)] loaded with different biomolecules, namely, gallic acid, polyphenols (POLY), and anthocyanins. Quantification of loading at variable times highlighted POLY on MBGs as the system with the highest loading. The ability to dismutate hydrogen peroxide (catalase-like activity) of the BGs evaluated is strongly correlated with cerium doping, while it is marginally decreased compared to the parent BG upon loading with biomolecules. Conversely, unloaded Ce-BGs show only a marginal ability to dismutate the superoxide anion (SOD)-like activity, while upon loading with biomolecules, POLY in particular, the SOD-like activity is greatly enhanced for these materials. Doping with cerium and loading with biomolecules give complementary antioxidant properties to the BGs investigated; combined with the persistent bioactivity, this makes these materials prime candidates for upcoming studies on biological systems.
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Project description:In this study, a bio-based acrylate resin derived from soybean oil was used in combination with a reactive diluent, isobornyl acrylate, to synthetize a composite scaffold reinforced with bioactive glass particles. The formulation contained acrylated epoxidized soybean oil (AESO), isobornyl acrylate (IBOA), a photo-initiator (Irgacure 819) and a bioactive glass particle. The resin showed high reactivity towards radical photopolymerisation, and the presence of the bioactive glass did not significantly affect the photocuring process. The 3D-printed samples showed different properties from the mould-polymerised samples. The glass transition temperature Tg showed an increase of 3D samples with increasing bioactive glass content, attributed to the layer-by-layer curing process that resulted in improved interaction between the bioactive glass and the polymer matrix. Scanning electron microscope analysis revealed an optimal distribution on bioactive glass within the samples. Compression tests indicated that the 3D-printed sample exhibited higher modulus compared to mould-synthetized samples, proving the enhanced mechanical behaviour of 3D-printed scaffolds. The cytocompatibility and biocompatibility of the samples were evaluated using human bone marrow mesenchymal stem cells (bMSCs). The metabolic activity and attachment of cells on the samples' surfaces were analysed, and the results demonstrated higher metabolic activity and increased cell attachment on the surfaces containing higher bioactive glass content. The viability of the cells was further confirmed through live/dead staining and reseeding experiments. Overall, this study presents a novel approach for fabricating bioactive glass reinforced scaffolds using 3D printing technology, offering potential applications in tissue engineering.
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Project description:In glass materials, Poisson's ratio (?) has been proposed to be correlated with a variety of features, including atomic packing density (Cg), liquid fragility (m), and network connectivity. To further investigate these correlations in oxide glasses, here, we study cesium borate and cesium silicate glasses with varying modifier/former ratio given the difference in network former coordination and because cesium results in relatively high ? compared to the smaller alkali modifiers. Within the binary glass series, we find positive correlations between ? on one hand and m and Cg on the other hand. The network former is found to greatly influence the correlation between ? and the number of bridging oxygens (nBO), with a negative correlation for silicate glasses and positive correlation for borate glasses. An analysis based on topological constraint theory shows that this difference cannot be explained by the effect of superstructural units on the network connectivity in lithium borate glasses. Considering a wider range of oxide glasses from the literature, we find that ? generally decreases with increasing network connectivity, but with notable exceptions for heavy alkali borate glasses and calcium alumino tectosilicate glasses.
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