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Optimization of magnetic nanoparticles for hyperthermia in viscous environments
Sojková, Tereza ; Fabián,, Martin (oponent) ; Hovorka,, Ondrej (oponent) ; Gröger, Roman (vedoucí práce)
Single-domain superparamagnetic iron oxide nanoparticles play a significant role in magnetic hyperthermia, a promising therapeutic method that can potentially treat any kind of tumor. It is generally known that cancer cells are more sensitive to elevated temperatures than healthy cells. This observation makes the tumors particularly sensitive to localized overheating in the process of magnetic hyperthermia, where superparamagnetic nanoparticles with diameters of 10-50 nm serve as the carriers of heat under applied AC magnetic field with the frequency of hundreds of kHz. The key parameter that determines the efficiency of nanoparticles is the specific absorption rate, which is a complex function of the shape, size, and surface coating of these particles. Moreover, the duration of exposure to AC fields is limited by the tendency of these nanoparticles to aggregation when used in vivo. The aim of this thesis is to develop a synthesis protocol for the preparation of monodisperse iron oxide NPs, which exhibit high values of SAR and good colloidal stability. The nanoparticles were prepared by two types of chemical synthesis: coprecipitation and thermal decomposition. The impact of reaction conditions on the size, shape, and magnetic properties of these nanoparticles was investigated. Thermal decomposition was found to be a better option for the preparation of monodisperse iron oxide nanoparticles, where especially the core-shell nanocubes were examined in more detail. Dynamic light scattering in conjunction with transmission and scanning electron microscopies were used to investigate their size, degree of polydispersity, colloidal stability, and morphology. The phase composition of nanoparticles was characterized by powder X-ray diffraction, Mössbauer spectroscopy, and electron energy loss spectroscopy. X-ray diffraction was used to study phase transformations in core-shell nanoparticles. Their magnetic properties were investigated using vibrating sample magnetometry and using electron holography. Moreover, the best candidates were evaluated for use in magnetic hyperthermia, magnetic particle imaging (MPI), and magnetic resonance imaging to inspect nanoparticles' broader application potential. This work expands the knowledge on size-dependent core-shell iron oxide nanoparticles for high-performance bio-applications. The results for 20 nm nanocubes after full phase transformation show very good heating capabilities for use in magnetic hyperthermia and three times higher MPI signal compared to the commercially used tracer.
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