Synthesis and Characterization of Magnetic Iron Oxide Nanoparticles
Buch in deiner Nähe kaufen
Beschreibung
The huge scientific and technological interests in fabrication of magnetic nanoparticles with defined size and shape distributions and high magnetic performance for applications such as homogeneous magnetic bioassays, magnetic particle imaging, targeted drug delivery, etc. are the major motivations of this study [1, 2]. Synthesis of functional magnetic biomarkers begins with the dimensionally and magnetically controlled synthesis of particles. Fabrication of uniformly sized and shaped nanoparticles has attracted a lot of attention in the last few years and yet is a great challenge. The ability to tailor size and morphology of nanoparticles gives the opportunity of exploring magnetism at the nanoscale, allowing to gain a deeper understanding of magnetic phenomenon originating from finite-size effects, such as superparamagnetism. Undoubtedly, superparamagnetism is one of the most intriguing properties of magnetic nanoparticles, appearing below a critical size threshold. The next topic is the characterization of nanoparticles. A broad range of physical properties being structural, compositional and magnetic have to be examined. Correlating different properties and aspects of nanoparticles is one of the biggest challenges. Considering magnetic nanoparticles as nano-biomaterials, it is vital to investigate their physicochemical aspects, including surface chemistry and inertness, toxicological effects and stability and interaction in biological media. Owing to the interdisciplinary nature of this research topic, a close collaboration between materials scientists, physicists, chemists and biologists is the key to overcome difficulties and deepen our knowledge.
The aim of this thesis is to (a) establish a robust and reproducible synthesis protocol for the fabrication of large single-core iron oxide nanoparticles with a narrow size distribution, (b) contribute to a deeper understanding of homogeneous nucleation and growth mechanisms in order to engineer customized particles particularly suitable for homogeneous magnetic detection of biomolecules, (c) correlate crystallographic, compositional and magnetic properties to particle core size, (d) design a phase transfer strategy to efficiently pull hydrophobic nanoparticles into aqueous media and prepare stable aqueous colloidal nanoparticle suspensions, (e) characterize their physical and chemical properties, assess their toxic impact on cells and understand particle cell interaction mechanisms and (f) eventually measure and analyze the particle performance as biomarkers for magnetic detection schemes based on the particle manipulation in dynamic magnetic fields.
The thesis is organized as follows:
In chapter 1, the principles of magnetism and nanomagnetism are reviewed briefly. Superparamagnetism as the most promising dimension dependent effect in single domain magnetic nanoparticles is discussed. The features appearing at the nanoscale, where surface to volume ratio rises significantly and consequently surface dominated effects become strong, are addressed. In chapter 2, the crystal structure of iron oxide phases is described. The most commonly used synthesis methods of iron oxide nanoparticles including chemical precipitation, hydrothermal, microemulsion and thermal decomposition are discussed. The synthesis methods are compared with regard to the resulting particle size distribution and their advantages and drawbacks are addressed. Finally, the theory of homogeneous nucleation and growth mechanisms in colloidal syntheses are reviewed and the synthetic strategies which have been so far proposed for realization of theoretical concepts in a real particle synthesis experiment are thoroughly discussed. In chapter 3, the principles of characterization methods which have been used in this thesis to analyze particle size and morphology distributions, crystallography, phase composition, electronic structure, surface chemistry, capping density of capped molecules, long term stability, static and dynamic magnetic properties and magnetic response to dynamic magnetic fields are explained. The assays employed to examine the in vitro cytotoxic and intrusive effects of particles are described. Chapter 4 contains all the experimental parts. The design of experiment methodology applied to optimize the most effective synthesis parameters is described. The synthesis procedure of poly(ethylene glycol) derivative compounds, particle phase transfer into aqueous fluids and further functionalization with Herceptin antibodies are discussed. The preparation method and experimental conditions of toxicity assays are provided. In chapter 5, the results of structural, magnetic, hydrodynamic analyses on the particles synthesized via the design of experiment are present and discussed. The particle nucleation and growth mechanisms are thoroughly discussed and a empirical growth model is given. In collaboration with Institute of Physical Chemistry, University of Hamburg, Institute of Condensed Matter Physics, TU Braunschweig and Physikalisch-Technische Bundesanstalt, Braunschweig and Berlin, the particle size dependence structural, compositional and magnetic properties of the synthesized iron oxide nanoparticles were unravelled. Besides the effect of ageing at ambient conditions on particle composition and magnetization is addressed. The physicochemical properties of particles stabilized in water with poly(ethylene glycol) derivative ligands are presented. The results of particle toxicity and cellular uptake assessments, carried out in a collaboration with Helmholtz Center for Infection Research, Braunschweig, are presented in this chapter. The measurement results of particle response to dynamic magnetic fields after PEGylation, functionalization with Herceptin antibodies and labeling with tumor specific HER2 antibodies are presented and discussed.
Autor*in
Aidin Lak