Nanoparticle Mediated Heating for Non-invasive Thermal Therapies A

Abstract

Nanomaterials have unique physics and chemistry properties compared with their bulk counterparts and have been widely studied in different fields ranging from energy to biomedicines. This thesis investigates controlled synthesis of gold nanomaterials, the heating and interactions of gold nanomaterials with external electromagnetic and ultrasonic fields, and their potential applications in non-invasive heat-related biomedicines. Gold nanomaterials have been synthesised by the citrate reduction method with the aid of ultrasonification. Through ultrasonification, the size of obtained spherical GNPs can be controlled between 10nm and 15nm, and the prepared nanoplates can be controlled between 50 nm to 150 nm. Purification process has been performed through membrane dialysis, in order to obtain pure nanoparticles for investigating the heating behavior of nanoparticle dispersions under EM/ultrasound field and elucidating the impurity effect. Moreover, the purified gold nanoparticles have been characterized by various means, such as FTIR, atomic absorption spectrometer, zetasizer, SEM, TEM and UV-Vis absorption for the purpose of fully understand the properties of gold nanoparticle in terms of purity, concentration, size, morphology and optical properties. The bulk heating effects of low-concentration GNPs have been investigated by using ultrasonic field, electromagnetic (EM) field, and laser irradiation. The results have shown that significant bulk temperature increase can be achieved for the lowconcentration gold nanoparticle dispersions under ultrasonic field, the EM field at 200 kHz and 400 kHz, and laser irradiation. Comparatively, the purified GNPs did not show significant heating effect under the EM fields of 13.56 MHz and 2.45 GHz. 6 Different mechanisms are thereby discussed to explain the heating effects. While some can be explained by established theories, such as the ultrasonic and laser heating, it is still unclear about the heating effect under low frequency EM field. A few possible reasons could be attributed to the changes of the dielectric properties and the electrophoresis effect. In addition, GNP incorporated microcapsules have been fabricated through the layer-bylayer technology, and laser treatments of the microcapsules embedded with different shapes of gold particles have been studied. The results have shown that matching between the laser wavelength and the absorption band of gold nanoparticles, which can be shifted by controlling the morphology of nanoparticles, is a prerequisite to achieve the maximum heating effect to deform the microcapsules and hence to present the microcapsules for biomedical uses. In vitro (B50 cell) and in vivo (fruit fly) studies of the biocompatibilities of our synthesised GNPs have been exanimated. The results demonstrated that the GNPs have high biocompatibility for B50 cells and fruit flies. GNPs assisted laser treatment of B50 cells has shown faster thermal damage to the cells in contrast to the cells without addition of GNPs. Keywords: nanomaterial, gold nanoparticle, capsules, hyperthermia, ablation, electromagnetic, ultraosound, surface Plasmon resonance, biocompatibility.