Nanomaterial for Hyperthermia Applications

Abstract

Cancer hyperthermia is a procedure that involves heating tumor tissues to high temperatures with the intent of killing the tumor cells. Hyperthermia is a well-established method and has had success in treating both advanced and recurrent cancers. The process can be implemented by a variety of heating methods, such as microwave, radiofrequency (RF), laser, and ultrasound. The current goal of hyperthermia is to use nanomaterials as carriers of therapeutic compounds to deliver heat at a specific target area to absorb the energy from the waves and convert it to heat without damaging the surrounding normal tissue. However, a generalized standard for determining optimal nanomaterials combined with these sources of heat needs more study in the research laboratory before implementing clinically. It is important to identify which nanomaterials, size, and shape meet the requirements of hyperthermia applications. Non-toxic and biocompatible materials, high light-to-heat efficiency, strong absorption cross section, and surface functionalities are necessary for nanomaterials]. Fortunately, there are many strong candidates which meet these requirements, including gold nanoparticles (AuNPs) and carbon nanotubes (CNTs). In this dissertation, I first studied the light-to-heat efficiency, known as photothermal conversion efficiency, of AuNPs with different morphologies such as spheres, spheres surface-functionalized with IR 808 dye, rods, and urchins. The photothermal conversion efficiency was determined experimentally by using a continuous wave (CW) near-infrared (NIR) light operating at 808 nm. I found that gold nanomaterials that absorbed in the NIR range heated the most efficiently and that surface modifying with an IR 808 dye tuned the absorbance and increased the photothermal conversion efficiency by a factor of 4 when compared to the bare counterpart. I also applied this same methodology to understand the hyperthermia capabilities and photothermal conversion efficiency of semiconducting single-walled carbon nanotubes (s-SWCNTs). In regard to CNTs, chirality played a role in this efficiency. Lastly, the NIR setup was used to determine the optical absorption cross section of various gold nanomaterials (GNMs) both experimentally and theoretically. The obtained optical absorption cross section of nanosphere and nanorods was in a good agreement with theoretical results obtained by Mie theory. This dissertation also proposes a numerical method based on heat transfer theory to predict temperature elevations generated by complex shapes of AuNPs such as nanorods and conjugated nanorods with IR (infrared) dyes. Then, we experimentally increase the temperature elevations by optically heating the solution with 808 nm NIR light with four different power densities. More importantly, the proposed method and experimental results are in good agreements. Finally, we designed an experimental set up to heat AuNPs using RF waves at different frequencies with the hope that hyperthermia can be applied with a safe, non-invasive procedure throughout the whole body. For this, different sizes of spherical AuNPs including 5, 10, 20, and 30 nm were studied. Varying frequencies, concentrations, and applied powers were investigated, and we found that all of these parameters significantly affect the heating of AuNPs. In general, 13.65 MHz coupled with higher concentrations of gold and high electric fields exhibited the most heating for all particle sizes.