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Spinelni superparamagnetni nanodelci in njihova uporaba v magnetni hipertermiji
ID Bužan Bobnar, Andreja (Author), ID Arčon, Denis (Mentor) More about this mentor... This link opens in a new window

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Abstract
Magnetna hipertermija predstavlja pomembno metodo zdravljenja v medicini, saj omogoča učinkovitejše in predvsem ciljano zdravljenje rakavih obolenj. Uporaba superparamagnetnih nanodelcev zaradi njihove majhnosti ter možnosti aktiviranja površine predstavlja še posebej pomembno smer raziskav magnetne hipertermije. Princip delovanja temelji na pregrevanju tkiva zaradi magnetnih izgub, ki so posledica Néelove in Brownove relaksacije. Učinkovitost pregrevanja določimo s specifično stopnjo absorpcije, ki predstavlja grelno moč nanodelca na enoto mase. Za uspešno zdravljenje rakavih obolenj želimo razviti magnetne nanodelce s čim večjo specifično stopnjo absorpcije pri čim nižjem polju, saj je na tak način koncentracija magnetnih nanodelcev, potrebna za doseganje željenega dviga temperature, minimalna. V magistrskem delu sem analizirala dva tipa vzorcev magnetnih nanodelcev, kobalt-feritne nanodelce, s splošno formulo $({\rm Co}_x{\rm Fe}_{1-x})[{\rm Fe}_2]{\rm O}_4,$ kjer $x$ predstavlja delež kobalta in magnetitne nanodelce ${\rm Fe}_3{\rm O}_4$. Vzorci so superparamagnetni in imajo spinelno strukturo. Mikroskopske meritve so pokazale, da so nanodelci sferične oblike, povprečne velikosti nanodelcev pa se gibljejo okrog 15 nm. Temperatura blokiranja je za vse vzorce nižja od sobne temperature in v primeru kobalt-feritnih vzorcev variira med 152 K in 285 K, za magnetitne vzorce pa je nekoliko nižja (okrog 35 K). Magnetizacijske krivulje pri sobni temperaturi ne kažejo histereze. Pri modeliranju se je izkazalo, da sta za modeliranje izmerjene krivulje potrebna dva Langevinova prispevka, kar je v skladu z lupinsko strukturo nanodelcev. Izmerjena specifična stopnja absorpcije kobalt-feritnih vzorcev je $\sim$2 W/g, magnetitnih pa $\sim$1 W/g. Izmerjene vrednosti so nekoliko nižje kot vrednosti navedene v literaturi. Z meritvami sem pokazala, da so vzorci superparmagnetni in da na njihove magnetne lastnosti bistveno vpliva prisotnost kobaltovih ionov. S prisotnostjo kobalta se temperatura blokiranja in specifična stopnja absorpcije povečata, kar pripisujem povečanju magnetne anizotropije nanodelcev. Povezava z deležem kobalta je zapletena, saj na magnetne lastnosti in magnetno hipertermijo vpliva spinelna struktura in mesto, ki ga kobaltovi ioni zasedajo v kristalni mreži.

Language:Slovenian
Keywords:magnetna hipertermija, superparamagnetizem, nanodelci, specifična stopnja absorpcije
Work type:Master's thesis/paper
Typology:2.09 - Master's Thesis
Organization:FMF - Faculty of Mathematics and Physics
Year:2020
PID:20.500.12556/RUL-124086 This link opens in a new window
COBISS.SI-ID:45776899 This link opens in a new window
Publication date in RUL:25.12.2020
Views:1375
Downloads:116
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Secondary language

Language:English
Title:Spinelni superparamagnetni nanodelci in njihova uporaba v magnetni hipertermiji
Abstract:
Magnetic hyperthermia is an important method for efficient cancer treatment. Magnetic hyperthermia with nanoparticles enables localised heating of the treated tissue, which makes this method attractive for a clinical use. The method is based on heat generated by magnetic losses due to the Néel and Brown relaxation. The heating efficiency is defined by Specific Absorption Rate (SAR), which is defined as the heating power generated per unit mass of the nanoparticles. For successful treatment we need to synthesize magnetic nanoparticles with the highest SAR at the given magnetic field. In this way, the concentration of nanoparticles needed for a sufficient local increase in temperature, is minimal. In this research I analyse two different types of magnetic nanoparticles, cobalt-ferrite nanoparticles with a general chemical formula $({\rm Co}_x{\rm Fe}_{1-x})[{\rm Fe}_2]{\rm O}_4,$ where $x$ stands for cobalt fraction, and magnetite nanoparticles ${\rm Fe}_3{\rm O}_4.$ Nanoparticles are spherical with an average diameter of 15 nm, as seen from the microscopic measurements. Blocking temperature is below room temperature for all samples and varies between 152 K and 285 K for cobalt-ferrite nanoparticles, while it is lower for magnetite nanoparticles (around 35 K). Magnetization measurements exhibit no hysteresis at room temperature, and are modelled with two superparamagnetic contributions. This suggests a core-shell structure of nanoparticles. Measured SAR for cobalt-ferrite nanoparticles is $\sim$2 W/g, and $\sim$1 W/g for magnetite nanoparticles. Measurements show that the samples are indeed superparamagnetic and that the influence of cobalt ions has significant impact on their magnetic properties. The presence of cobalt atoms in the structure increases SAR, most likely due to an increase in magnetic anisotropy. Further studies on the role of cobalt position in the spinel structure are needed to fully understand SAR of such nanoparticles.

Keywords:magnetic hyperthermia, superparamagnetism, nanoparticles, specific absorption rate

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