Please use this identifier to cite or link to this item: http://hdl.handle.net/10266/4463
Title: Structural and bioactive properties of Fe/Mn oxides substituted sodium silicate glasses
Authors: Singh, Satwinder
Supervisor: Singh, Kulvir
Keywords: bioactivity;glass-ceramics;simulated body fluids;hyperthermia;magnetic properties;hydroxyapatite
Issue Date: 2-May-2017
Abstract: Glasses and glass-ceramics containing transition metal (TM) oxides find applications in various fields such as memory devices, smart windows, electronics, biomaterials etc. Specially designed magnetic bioactive glasses/glass-ceramics have great potential in biomedical applications such as magnetic resonance imaging (MRI), drug delivery systems and also magnetic induction hyperthermia treatment of cancer. Bioactive glasses/glass-ceramics have ability to form a hydroxyapatite (HAp) layer on their surface during reaction in physiological environments, which helps to form a chemical bond with the bone. Additionally, the embedded magnetic particles may generate heat under the alternating magnetic field, which may be used for the treatment of malignant cancer cells. In the present work, calcium sodium silicate glasses/glass-ceramics containing MnO2 and Fe2O3 are prepared by the melt and quench technique. The effect of systematic replacement of MnO2 by Fe2O3 on the glass formation, physical parameters and structural properties are studied. Their usefulness for hyperthermia is estimated by investigating their magnetic properties. Bioactivity of the glasses/glass-ceramics was also observed in-vitro using simulated body fluids (SBF). The thesis work is represented in five chapters as follows: Chapter 1 introduces glasses and glass-ceramics as biomaterials after brief discussion on history and evolution of the biomaterials. The interaction of the implants with the body parts is discussed. Different applications of bioactive glasses/glass-ceramics inside the human body are described to emphasize their importance and versatility as biomaterials. The potential and novelty of using glasses and glass-ceramics as thermoseeds for hyperthermia treatment of cancer is also highlighted in this chapter. The chapter ends with description of the procedure followed to study the in-vitro bioactivity of glasses and the mechanism of formation of hydroxyapatite (HAp) layer on their surfaces after soaking in simulated body fluids. Chapter 2 is a review of the literature related to the various properties of glasses and glass-ceramics containing transition metal (TM) oxides. The variable oxidation states of TMs in glasses greatly affect their structural and optical properties. Variable field strength of the TM ions changes in local structure of glasses and glass-ceramics which leads to tailoring of their other properties. Apart from this, magnetic glass-ceramics reported for magnetic induction hyperthermia treatment of cancer are discussed. Magnetic phase in glasses/glass-ceramics sometimes proves to be detrimental for their bioactivity. Various factors affecting bioactivity of glasses and glass-ceramics are given in details to enrich the conceptual foundation of the present work. This chapter completes by providing the motivation for the present work and basis of selecting the present compositions. Chapter 3 encompasses the information on the raw materials used, methods of preparation of the glasses/glass-ceramics and their processing along with the fundamentals of each technique used to characterize these samples. Glasses and glass-ceramics were prepared by melting the mixture of raw chemicals and then quenching it in air between thick copper plates. Density of as-prepared samples was measured by Archimedes principle. The physical parameters such as molar volume, excess volume, oxygen packing density etc. were derived from standard formulas using the measured values of density. The structural properties of the as-prepared glasses were analyzed by the X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). High resolution transmission electron microscopic (HRTEM) images of selected samples were taken along with their selected area electron diffraction (SAED) patterns to check the possibility of nanocrystallization in the glasses. Optical properties of the glasses/glass-ceramics were investigated using UV-visible spectroscopy. Magnetic properties of these samples were studies using vibrating sample magnetometer (VSM). The bioactivity of these glasses/glass-ceramics was checked through in-vitro tests by immersing the samples in simulated body fluid (SBF) for different time durations. During immersion of the glasses/glass-ceramics, the pH of the SBF and weight of the samples were measured regularly. The glasses/glass-ceramics taken out from the SBF were characterized by XRD, FTIR, VSM, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and microwave plasma atomic emission spectroscopy (MPAES) to access the information on the physiological reactions taken place on their surfaces. Chapter 4 is the interpretation of the results obtained from the various characterization techniques discussed in the previous chapter. In the first part, the results of the parent series of glasses/glass-ceramics are discussed. XRD patterns of the samples show that extreme concentrations of Fe2O3 and MnO2 prevent the glass formation. Only at optimum amount of MnO2 and Fe2O3 (when the ratio MnO2/Fe2O3 is 0.5) x-ray amorphous glass is formed. MnO2 seems to help in the glass-formation, while Fe2O3 played a role of network modifier in the present compositions. In the compositions containing higher amount of Fe2O3 i.e. 10-F and 15-F, nanocrystalline magnetite (Fe3O4) is formed, which indicates the in-situ reduction of some fraction of Fe3+ ions (in initial composition as Fe2O3) to Fe2+ ions. This reduction influenced the properties of the present glasses/glass-ceramics. Density and molar volume of the glasses/glass-ceramics increased with Fe2O3 content in the compositions. On the other hand, optical band gap and Urbach energy decreased with Fe2O3. Higher concentration of MnO2 leads to antiferromagnetism of the as prepared glasses. On the other hand, Higher concentration of Fe2O3 exhibit characteristics of soft ferrimagnetic materials. The saturation magnetization and coercivity of these glasses/glass-ceramics increase with increasing volume fraction of crystallized magnetite. 10-F and 15-F exhibit large hysteresis area, indicating their heat generation tendency under alternating magnetic fields. However, higher iron oxide reduced the dissolution rate of the glass-ceramics in physiological fluids. Moreover, higher MnO2 content induced more disordering on the surface of the samples, which might have increased their surface reactivity. FTIR and SEM images confirm the presence of c-HAp on the surface of the present glasses/glass-ceramics. The exchange reactions between the glasses/glass-ceramics with SBF affected their magnetic parameters. X-ray amorphous glass i.e. 5-F was selected to further investigate the effect of extra wt% TiO2 on the properties of parent glass. The as-quenched samples were found to be completely amorphous as per their XRD patterns. However, HRTEM observations indicate the presence of nanocrystallites embedded in the glass-matrix. TiO2 did not influence physical and optical properties significantly. On the other hand, it enhanced the structural order in the network and improved its mechanical as well as magnetic properties. TiO2 exhibited concentration dependent role as evident from the results. Interestingly, glasses with 2.50 and 3.75 wt% TiO2 exhibited superparamagnetic behavior, which is rarely reported in bioactive glasses of similar compositions. Nanocrystalline phases were grown in the glass-matrix by controlled heat-treatment of the glasses. Heat-treatment changed the magnetic properties of the glass-ceramics remarkably by reversing the trend of saturation magnetization as compared to the as-quenched glasses. Glass-ceramic containing 1.25 wt% TiO2 i.e. T1 exhibit slight increased saturation magnetization after immersion in the SBF, while other glass-ceramics showed lowering of the saturation magnetization after physiological reactions. All the samples exhibit formation of HAp on their surfaces after dipping in SBF solution. Chapter 5 is the summary of the major conclusions drawn from the results discussed in the previous chapter. Deviation from MnO2/Fe2O3 ratio 0.5 gives rise to formation of nanocrystalline phases in the glass-matrix. 10-F and 15-F are expected to be useful for magnetic induction hyperthermia treatment of cancer. TiO2 can be added to the glass compositions for better mechanical, magnetic and bioactive properties without compromising with physical and optical parameters of the glasses. Among the glass-ceramics containing TiO2, T1 may give better performance in physiological environments during hyperthermia treatment of cancer. The future scope of research related to present studies is also given at the end of this chapter.
URI: http://hdl.handle.net/10266/4463
Appears in Collections:Doctoral Theses@SPMS

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