Effect of magnesium ion incorporation on the thermal stability, dissolution behavior and bioactivity in bioglass-derived glasses

There is a strong discrepancy in the literature regarding the effect of magnesium on bioactive glasses. Hence the present study is focused on the physical and chemical behavior of the "golden standard" 45S5 glass and magnesium-containing bioactive glasses developed here to evaluate their reactivity and in vitro bioactivity. The aimof this study was to analyze the influence of CaO replacement by MgO, especially its effect on the rate of formation of the apatite-like layer at the glass surface, the reaction kinetics between the glasses and simulated body fluid (SBF-K9) and on the glass stability against devitrification during heating. Five melt-derived bioactive glasses of the system 24.3Na2O-26.9(xCaO-(1-x)MgO)-46.3SiO2-2.5P2O5 (x=1; 0.875; 0.75; 0.625 and 0.5) were synthesized with CaO progressively replaced by MgO.Their thermal stability on heating was characterized by DSC analysis. Their degradation and ability to form an apatite-like layer were evaluated through in vitro tests by immersion in SBF-K9; FTIR, ion selective electrode analysis and by solid state nuclear magnetic resonance (NMR) spectroscopy. Our results indicate that magnesium plays an important role in the stability of this glass family, defined as the difference between the glass transition temperature Tg and crystallization temperature Tx. The lower Tg observed in the MgO-rich glasses and insignificantly changed solubilities, as well as the 29Si NMR results suggest that in this glass system MgO does not act as a network intermediate or former oxide, but as network modifier, aswe expected. Dissolution kinetics, FTIR, and solid state 31P and 1HMAS-NMR consistently indicate that partial replacement of CaO by MgO in the bioglass does not influence the rate at which the initial amorphous calciumphosphate (ACP) layer is precipitated when the glass is exposed to SBF. In contrast it greatly reduces the rate of conversion of this precursor phase to the crystalline hydroxycarbonate apatite (HCA)-layer.CNPqFAPESP (13/07793-6

Bioactive magnetic glass-ceramics for cancer treatment

After five decades of research on bioactive glasses and glass-ceramics, these materials became of considerable interest due to their revolutionary potential for numerous health applications, including cancer treatment. One advantage of glass-ceramics compared with other materials – such as metallic alloys and polymers – is their capability of being highly bioactive and, if desired, containing magnetic phases. Hyperthermia (HT) is an alternative for treating cancer; the strategy is to increase the temperature of the tumor using an external magnetic field that increases the temperature of an implanted magnetic material, which works as an internal heat source. This local increase of temperature, ideally to ~43°C, could kill cancer cells in situ without damaging the healthy surrounding tissue. To achieve such goal, a material that presents a balance between proper magnetic properties and bioactivity is necessary for the safe applicability and successful performance of the HT treatment. Certainly, achieving this ideal balance is the main challenge. In this article we review the state-of-the-art on glass-ceramics intended for HT, and explore the current difficulties in their use for cancer treatment, starting with basic concepts and moving onto recent developments and challenges

Smart Bone Graft Composite for Cancer Therapy Using Magnetic Hyperthermia

Magnetic hyperthermia (MHT) is a therapy that uses the heat generated by a magnetic material for cancer treatment. Magnetite nanoparticles are the most used materials in MHT. However, magnetite has a high Curie temperature (Tc~580 °C), and its use may generate local superheating. To overcome this problem, strontium-doped lanthanum manganite could replace magnetite because it shows a Tc near the ideal range (42–45 °C). In this study, we developed a smart composite formed by an F18 bioactive glass matrix with different amounts of Lanthanum-Strontium Manganite (LSM) powder (5, 10, 20, and 30 wt.% LSM). The effect of LSM addition was analyzed in terms of sinterability, magnetic properties, heating ability under a magnetic field, and in vitro bioactivity. The saturation magnetization (Ms) and remanent magnetization (Mr) increased by the LSM content, the confinement of LSM particles within the bioactive glass matrix also caused an increase in Tc. Calorimetry evaluation revealed a temperature increase from 5 °C (composition LSM5) to 15 °C (LSM30). The specific absorption rates were also calculated. Bioactivity measurements demonstrated HCA formation on the surface of all the composites in up to 15 days. The best material reached 40 °C, demonstrating the proof of concept sought in this research. Therefore, these composites have great potential for bone cancer therapy and should be further explored

Biosilicate®–gelatine bone scaffolds by the foam replica technique: development and characterization

The development of bioactive glass-ceramic materials has been a topic of great interest aiming at enhancing the mechanical strength of traditional bioactive scaffolds. In the present study, we test and demonstrate the use of Biosilicate® glass-ceramic powder to fabricate bone scaffolds by the foam replica method. Scaffolds possessing the main requirements for use in bone tissue engineering (95% porosity, 200–500 μm pore size) were successfully produced. Gelatine coating was investigated as a simple approach to increase the mechanical competence of the scaffolds. The gelatine coating did not affect the interconnectivity of the pores and did not significantly affect the bioactivity of the Biosilicate® scaffold. The gelatine coating significantly improved the compressive strength (i.e. 0.80 ± 0.05 MPa of coated versus 0.06 ± 0.01 MPa of uncoated scaffolds) of the Biosilicate® scaffold. The combination of Biosilicate® glass-ceramic and gelatine is attractive for producing novel scaffolds for bone tissue engineering