Famiani, Simone; (2020) Synthesis and Characterisation of Ironbased Nanoparticles for Magnetic Hyperthermia. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Magnetic nanoparticles (MNP) have been recently gaining much attention thanks to their application as cancer-killing agents through heat delivery in magnetic hyperthermia treatment. Although MNP are considered very promising, there is still the need to investigate different magnetic materials and nanoparticles size to improve the performances of MNP in magnetic hyperthermia. Therefore, it is important to expand the knowledge on the chemistry of the formation of Fe-based MNP. In this work, different Fe-based, MNPs were synthesised and their efficiency in magnetic hyperthermia was also evaluated. The NPs were fully characterised to confirm the final phase and composition and the characterisation techniques used are described in Chapter 2. Chapter 3 describes the synthesis and characterisation of metallic Fe NPs. As this material is sensitive towards oxidation, to overcome this limitation, Fe NPs of different size were synthesised using a novel approach that allowed a greater size control, and the study of oxidative processes that depends on the size of the synthesised NPs. In this chapter an easy and optimal ligand transfer of the synthesised NPs in water was investigated and different strategies were employed, including polymer encapsulation, silica coating and ligand exchange with a dopaminefunctionalised polymer. The latter resulted in the best performances and it was used for the transfer in water of Fe NPs of different size. The ≈20 nm Fe NPs, can maintain a metallic core even after ligand exchange for 2 months, with high magnetic heating efficiency, whereas smaller Fe NPs (≈15 nm) oxidised completely. In Chapter 4, the synthesis of Fe2C NPs was investigated. This alloy possesses the magnetic and metallic feature of metallic Fe with an increased stability towards oxidation thanks to the C atoms in the crystal structure. After optimising the synthesis, the material was fully characterised to ensure the uniformity of the final phase. The NPs were then transferred in water using the strategy optimised in Chapter 3 and the enhanced chemical stability of the Fe2C NPs towards oxidation was shown by the fact that the Fe2C phase was fully retained even in ≈ 14 nm NPs. The NPs are also tested as magnetic hyperthermia agents. In Chapter 5 Fe3O4 NPs are studied. In this case, novel plate-like Fe3O4 NPs were synthesised, as anisotropic shaped NPs are known to possess enhanced performances in magnetic hyperthermia. It was shown that the main agent affecting the final shape of NPs during the reaction was the chloride contained in the molecule hexadecyl ammonium chloride (HDA-Cl). The synthesis of plates-like NPs was optimised and different size of nanoplates were obtained by using different ligand with the best performing being sodium oleate. Plates NPs of different size were then tested for magnetic hyperthermia. In Chapter 6 the results from the previous chapters were summarised and the magnetic hyperthermia performances of different NPs were discussed and compared, including also commercially available magnetic NPs for biomedical applications.

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