Unique heating curves generated by radiofrequency electric-field interactions with semi-aqueous solutions

Abstract

Aqueous and nanoparticle-based solutions have been reported to heat when exposed to an alternating radiofrequency (RF) electric-field. Although the theoretical models have been developed to accurately model such a behavior given the solution composition as well as the geometrical constraints of the sample holder, these models have not been investigated across a wide-range of solutions where the dielectric properties differ, especially with regard to the real permittivity. In this work, we investigate the RF heating properties of non-aqueous solutions composed of ethanol, propylene glycol, and glycine betaine with and without varying amounts of NaCl and LiCl. This allowed us to modulate the real permittivity across the range 25-132, as well as the imaginary permittivity across the range 37-177. Our results are in excellent agreement with the previously developed theoretical models. We have shown that different materials generate unique RF heating curves that differ from the standard aqueous heating curves. The theoretical model previously described is robust and accounts for the RF heating behavior of materials with a variety of dielectric properties, which may provide applications in non-invasive RF cancer hyperthermia. Published by AIP Publishing.[http://dx.doi.org/10.1063/1.4973218] It has been shown that saline solutions under exposure to radiofrequency (RF) electric fields display peak heating behavior at a certain concentration, 1,2 and this behavior has been generalized to include any aqueous system, regardless of the content or identity, including buffer solutions, blood, and nanoparticle suspensions.3 These studies however, are limited to aqueous systems and until now the theoretical models used to explain this behavior have not been validated for other materials. To fully characterize RF heating, materials representing a wider range of dielectric properties must be studied. Such an understanding may have direct applications in non-invasive RF cancer hyperthermia therapy. [4][5][6][7][8][9] Although most tissues in the human body are made up primarily of water and other tissues, such as fat and bone, have drastically different dielectric properties and are expected to behave differently. Overheating of the subcutaneous fat layer, for example, is a major limiting factor in hyperthermia cancer therapy (especially at 13.56 MHz) and must be overcome if this technology is to be safely implemented in the clinic. 10In this study we probe the dielectric and heating properties of materials with reduced water content and variable conductivity. Experimental RF heating curves similar to those of aqueous solutions are generated for each material, and these are used to confirm the generalization of the theoretical heating model to a wider range of systems. The dielectric properties, such as permittivity, of a material describe its response to electromagnetic (EM) fields. For time-varying alternating electric fields, the permittivity becomes a complex parameter given by the equationwhere e r , e 0 r , e 00 r are the co...

Development of Photoactive Sweet-C 60 for Pancreatic Cancer Stellate Cell Therapy

“…We have previously shown that C 60 derivatives can be used as convenient scaffolds for anticancer therapeutic drug delivery [11], and that such agents preferentially localize in both the intracellular nuclear pore complex [12] and tumor vasculature [13]. Other applications investigated in our labs include the use of C 60 derivatives to enhance noninvasive radiofrequency cancer therapy [14][15][16] and to serve as efficacious MRI contrast agents [17][18][19].…”