Electromagnetic heating effect of aggregated gold nanoparticle colloids

Abstract

Gold nanoparticles (GNPs) have been recently investigated intensively for potential hyperthermia treatment of malignant cancer cells in combination with radiofrequency (RF) electromagnetic (EM) fields/waves. However, many controversial results have been reported on whether GNPs can be heated by EM fields. It has been suggested that aggregated GNPs may be heated significantly by a RF field, which however has not been examined experimentally. This work proposes a novel electric treatment of mono-dispersed particles to create aggregated GNPs, and conducts an investigation of their bulk heating behavior under a 655 nm laser and a 13.56 MHz RF electric field. It is revealed that the heating rates of aggregated colloids are significantly higher than those of mono-dispersed GNPs for the 655 nm laser, whereas at 13.56 MHz, the heating effects are barely noticeable for both aggregated and mono-dispersed colloids. Various possible reasons are discussed and the negligible electric field enhancement is believed to be responsible at 13.56 MHz.

Radiofrequency heating of nanomaterials for cancer treatment: Progress, controversies, and future development

“…Liu et al suggested the possible modification of field distribution due to the change of boundary condition and dielectric properties. 86 Experimentally, Liu et al showed that the measured results could be explained by Hanson's model. 28,86 In addition, the sample holder could also modify boundary condition that attenuated the field strength.…”

“…86 Experimentally, Liu et al showed that the measured results could be explained by Hanson's model. 28,86 In addition, the sample holder could also modify boundary condition that attenuated the field strength. 81 Considering that the presence of ions modifies both the conductivity and the dielectric properties, the contribution of ionic heating has to be carefully treated.…”

Laser heating of metallic nanoparticles for photothermal ablation applications

“…However, for any point in the medium (z=1, 2, 3), the absorption increases to a peak point and then decreases with the attenuation factor. By using Equation (11), it can be predicted that the peak point takes place at α = 1/z. This observation quantified the optimal size of the tumor that a specific laser and nanoparticles can be applied.…”

“…Consequently, side effects can also be suppressed. The research into nanomaterial-mediated hyperthermia has covered many energy sources, such as radiofrequency (RF) wave, 11,13 infrared (IR) laser, 14,15 and visible light laser. 16,17 Normally, the area of cancerous tissue shall be kept over 42 • C for a certain period so as to produce lethal effect to cancer cells.…”

“…In recent years, the research work involving nanoparticles in cancer treatment has been actively conducted in a wide range of areas, such as drug-delivery, 3,4 imaging contrast agents 5,6 and hyperthermia agents. [7][8][9][10][11][12] These methods are designed to enhance the specificity, in the meantime without introducing negative side effects.…”