Browsing by Author "Georgiev H."

Now showing 1 - 4 of 4
  • No Thumbnail Available
    Item
    Carbonate apatite formation on novel multiphase CaO-SiO2-P2O5- MgO glass-ceramics in TRIS-HCl buffer
    (2016-01-01) Radev L.; Michailova I.; Georgiev H.; Zaimova D.
    The main purpose of the presented article is the preparation of novel glass-ceramics in CaO-SiO2-P2O5-MgO system and evaluation of carbonate apatite formation after soaking in TRIS-HCl buffer solution for 14 days. The investigated samples were prepared via sol-gel method and structure of the obtained samples was studied using XRD, FTIR, SEM, XPS and ICP-AES. XRD of the thermally treated samples showed that the presence of some crystalline phases is depended on the gel composition. FTIR revealed the existence of all characteristic bands for the observed crystalline phases. SEM monitored the presence of particles with different morphology. After soaking in TRIS-HCl solution, FTIR confirmed that carbonate apatite was formed on the soaked surface. The obtained data are in a good agreement with XPS analysis. The change of ions concentrations in TRIS-HCl buffer solution after immersion of the prepared glass-ceramics was recorded by ICP-AES measurements.
  • No Thumbnail Available
    Item
    In vitro bioactivity of glass-ceramic/fibroin composites
    (2017-01-01) Radev L.; Michailova I.; Stateva S.; Zaimova D.; Georgiev H.; Apostolova M.
    Bioactive composite materials were prepared by mixing 20 wt.% of silk fibroin (SF) and 80 wt.% of glassceramics from CaO-SiO2-P2O5-MgO system. In vitro bioactivity of the prepared composites was evaluated in 1.5 simulated body fluid (1.5 SBF) in static conditions. The obtained samples before and after in vitro tests were characterized by X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The changes in 1.5 SBF solutions after soaking the samples were evaluated by inductively coupled plasma atomic emission spectroscopy (ICP-AES). MG63 osteosarcoma cells were used for the biological experiments. The obtained experimental data proved that the synthesized composites exhibit excellent in vitro bioactivity.
  • No Thumbnail Available
    Item
    New Glass-Ceramics in the System Ca2SiO4-Ca3(PO4)2—Phase Composition, Microstructure, and Effect on the Cell Viability
    (2025-08-01) Mihailova I.; Dimitrova P.; Avdeev G.; Ivanova R.; Georgiev H.; Nedkova-Shtipska M.; Teodosieva R.; Radev L.
    The CaO-SiO2-P2O5 system is one of the main systems studied aiming for the synthesis of new bioactive materials for bone regeneration. The interest in materials containing calcium-phosphate-silicate phases is determined by their biocompatibility, biodegradability, bioactivity, and osseointegration. The object of the present study is the synthesis by the sol-gel method of biocompatible glass-ceramics in the Ca2SiO4-Ca3(PO4)2 subsystem with the composition 6Ca2SiO4·Ca3(PO4)2 = Ca15(PO4)2(SiO4)6. The phase-structural evolution of the samples was monitored using X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and surface area analysis. A powder (20–30 µm) glass-ceramic material containing fine crystalline aggregates of dicalcium silicate and plates of silicon-substituted hydroxyapatite was obtained after heat treatment at 700 °C. After heat treatment at 1200 °C, Ca15(PO4)2(SiO4)6, silicocarnotite Ca5(PO4)2(SiO4), and pseudowollastonite CaSiO3 were identified by XRD, and the particle size varied between 20 and 70 µm. The compact glass-ceramic obtained at 1400 °C contained Ca2SiO4-Ca3(PO4)2 solid solutions with an α-Ca2SiO4 structure as a main crystalline phase. SEM showed the specific morphology of the crystalline phases and illustrated the trend of increasing particle size depending on the synthesis temperature. Effects of the glass-ceramic materials on cell viability of HL-60-derived osteoclast-like cells and on the expression of apoptotic and osteoclast-driven marker suggested that all materials at low concentrations, above 1 µg mL−1, are biocompatible, and S-1400 might have a potential application as a scaffold material for bone regeneration.
  • No Thumbnail Available
    Item
    SODA LIME SILICATE GLASSES CONTAINING IRON OXIDE - IN VITRO EVALUATION
    (2024-01-01) Mihailova I.; Harizanova R.; Shtapleva-Dimova N.; Georgiev H.; Nedkova-Shtipska M.
    Three glasses with different iron oxide concentrations (between 5 and 8.1 mol %) were obtained in the CaO - Na2O - SiO2 - Fe2O3 system by using conventional melting-quenching technique. The amorphous nature of the synthesized materials is confirmed by X-ray diffraction analysis, XRD. The physico-chemical and structural characterization of the glasses was performed by measuring their density, refractive indices, as well as by calculating the molar volume, oxygen packing density and recording the infrared spectra by Fourier Transformed Infrared Spectroscopy, FT-IR, respectively. The glasses were evaluated in vitro by examining bone-like apatite formation on their surfaces in a simulated body fluid, SBF. The structural changes in the glasses during the in-vitro test were traced by means of FT-IR and Scanning Electron Microscopy, SEM. The solutions were examined by Inductively Coupled Plasma Optical Emission Spectroscopy, ICP-OES to determine the ion exchange between the glasses and the starting SBF and the corresponding effect on the pH was also recorded.