An investigation into the use of CALNN capped gold nanoparticles for improving microwave heating

The use of microwaves for both therapeutic and diagnostic applications has become an accepted alternative in the clinics. For diagnostics, gold (Au) nanoparticles have been used for imaging tumour vasculature and also served as potential diagnostic markers for cancer. [1] In high-frequency therapeutic applications, two different treatments exist; hyperthermia and ablation. [2] In hyperthermia, the tumour tissue is heated to supra-physiological temperatures, making it more susceptible to traditional treatment methods such as chemotherapy and radiotherapy. This type of treatment could be administered externally. However, there still remains a challenge to focus the heating to particular areas which need to be treated, while avoiding unwanted hotspots. To date, numerous methods have been used to focus the heat from different antennas. A novel technique which is being investigated is the use of nanoparticles to improve focusing and thus achieve better localised heating effect. A previous study by Cardinal et al. [3] showed that at RF-frequencies, remarkable improvements resulted from using Au nanoparticles. In this work, the use of CALNN peptide capped Au nanoparticles for the focusing of microwaves at 2.45 GHz is investigated. The CALNN capped Au nanoparticles were prepared as described elsewhere. [4] Au nanoparticles were added to tissue mimicking solutions (such as muscle, liver or fat) to compare their dielectric properties with the those of the control (without Au nanoparticles). The frequency range investigated was from 400 MHz to 20 GHz. During this study, various concentrations, particle sizes and shapes of Au nanoparticles were considered. The study also investigated the heating rates of the pseudo-biological tissue samples and how these varied with the addition of the nanoparticles. The outcome of this study will determine the viability of using CALNN capped Au nanoparticles to assist in the focusing of microwave radiation during microwave hyperthermia.