Iron oxide nanocubes for magnetic hyperthermia

Identifier:  TDX:2562

Handle: https://hdl.handle.net/20.500.11797/TDX2562

Authors:  Niculaes, Dina

Abstract:
Three main projects were conducted during my thesis that was focused on the study of nanosystems based on iron oxide nanocubes (IONCs) for magnetic hyperthermia (MH). The novel use of MH set-up for the mild oxidization of Fe1-xO/Fe3-δO4 core-shell nanocubes to single Fe3O4 phase was demonstrated. As specific absorption rate (SAR) values of wüstite/magnetite core-shell nanocubes were lower compared to magnetite IONCs of similar cube edge length, the FeO core was oxidized by MH stimulation. After several MH treatments, the SAR values increased twice, while colloidal stability, size distribution and shape remained unaffected. The magnetically stimulated IONCs showed higher saturation magnetization, reflecting structural and compositional changes, as confirmed by electron microscopy and superconductive quantum interference device studies. The mild MH treatment also opened up the possibility of attaching biologically relevant molecules to the surface of nanocubes and preserving their activity while improving the IONCs heat performance. The SAR values of core-shell IONCs were also enhanced by clustering the nanocubes in chain like structures. Initially, the controlled clustering of the IONCs during their water transfer was developed, enabling the formation of clusters with mean hydrodynamic sizes between 30 and 100 nm. The hyperthermia response of individual nanocubes vs. soft colloidal nanoclusters of different sizes was evaluated. The so called “dimers” and “trimers”—2D structures formed with two and three IONCs—showed higher SAR values. Drug loading on two nanosystems designed for heat-triggered chemotherapeutic drug release was achieved. Both systems were based on magnetite IONCs coated with thermo-responsive polymers loaded with doxorubicin. The goal was to have stable nanocarriers at body temperature that would release the cargo exclusively upon the application of an alternating magnetic field (AMF). Once individually thermo-responsive polymer coated IONCs with high SAR values were obtained, the heat-triggered doxorubicin release under AMF—at biologically relevant field conditions—was qualitatively, but not quantitatively proven.