Thomas, L.; (2010) Nanoparticle synthesis for magnetic hyperthermia. Doctoral thesis , UCL (University College London).

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Abstract

This work reports on an investigation into the synthesis, control, and stabilisation of iron oxide nanoparticles for biomedical applications using magnetic hyperthermia. A new understanding of the factors effecting nanoparticle growth in a coprecipitation methodology has been determined. This thesis challenges the highly cited Ostwald Ripening as the primary mechanism for nanoparticulate growth, and instead argues that in certain conditions, such as increasing reaction temperature, a coalescence mechanism could be favoured by the system. Whereas in a system with a slower rate of addition of the reducing agent, Ostwald ripening is the favoured mechanism. The iron oxide nanoparticles made in the study were stabilised and functionalised for the purpose of stability in physiological environments using either carboxylic acid or phosphonate functionalised ligands. It was shown that phosphonate ligands form a stronger attachment to the nanoparticle surface and promote increased stability in aqueous solutions, however, this affected the magnetic properties of the particles and made them less efficient heaters when exposed to an alternating magnetic fields. Tiopronin coated iron oxide nanoparticles were a far superior heater, being over four times more effective than the best commercially available product. Due to its strong response, experiments into the antimicrobial properties of tiopronin coated iron oxide nanoparticles were undertaken, specifically on Staphylococcus aureus, to our knowledge this is the first time magnetic hyperthermia has been used for such an application. At concentrations of 50 mg/ml the sample was capable of complete bacterial kills following exposure to the in-house magnetic hyperthermia MACH system. Aging and oxidation over a period of a month did decrease the performance of the particles to kill bacteria using MACH heating, however they were still shown to be effective in killing Staphylococcus aureus.

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