Radiofrequency heating pathways for gold nanoparticles

Abstract

This feature article reviews the thermal dissipation of nanoscopic gold under radiofrequency (RF) irradiation. It also presents previously unpublished data addressing obscure aspects of this phenomenon. While applications in biology motivated initial investigation of RF heating of gold nanoparticles, recent controversy concerning whether thermal effects can be attributed to nanoscopic gold highlight the need to understand the involved mechanism or mechanisms of heating. Both the nature of the particle and the nature of the RF field influence heating. Aspects of nanoparticle chemistry and physics, including the hydrodynamic diameter of the particle, the oxidation state and related magnetism of the core, and the chemical nature of the ligand shell may all strongly influence to what extent a nanoparticle heats in an RF field. Aspects of RF include: power, frequency and antenna designs that emphasize relative strength of magnetic or electric fields, and also influence the extent to which a gold nanoparticle heats in RF. These nanoparticle and RF properties are analysed in the context of three heating mechanisms proposed to explain gold nanoparticle heating in an RF field. This article also makes a critical analysis of the existing literature in the context of the nanoparticle preparations, RF structure, and suggested mechanisms in previously reported experiments.

On the physical limitations for radio frequency absorption in gold nanoparticle suspensions

“…A number of publications have proposed that biological tissue can be heated quickly and selectively by the use of gold nanoparticles (GNPs) that are subjected to a strong time-harmonic electromagnetic field, e.g., at 13.56 MHz or in the microwave regime, where the band is chosen due to regulations, see e.g., [1][2][3][4][5][6]. The aim is to develop a method with the potential to treat cancer.…”

Parameter studies on optimal absorption and electrophoretic resonances in lossy media

“…It has recently been shown in [4] that (2), and hence also (1) are locally concave functions in the complex parameter ε 1 and which are maximized by the conjugate match…”

“…In particular, gold nanoparticles (GNPs) can be coated with ligands that target specific cancer cells as well as providing a net electronic charge of the GNPs. One hypothesis is then that the charged GNPs will facilitate an electrophoretic current that can destroy the cancer under electromagnetic radiation [1,4,5]. However, it is also important to observe the complexity of the clinical application with many possible physical and biophysical phenomena to consider, as well as the fact that several authors have questioned whether metal nanoparticles can be heated in radio frequency at all, see e.g., [1,3].…”

“…One hypothesis is then that the charged GNPs will facilitate an electrophoretic current that can destroy the cancer under electromagnetic radiation [1,4,5]. However, it is also important to observe the complexity of the clinical application with many possible physical and biophysical phenomena to consider, as well as the fact that several authors have questioned whether metal nanoparticles can be heated in radio frequency at all, see e.g., [1,3]. We have recently performed a study on the physical limitations for radio frequency absorption in a spherical suspension where the main theoretical result is the derivation of an optimal conjugate match with respect to the surrounding medium [4].…”

Gold nanorod–based poly(lactic-co-glycolic acid) with manganese dioxide core–shell structured multifunctional nanoplatform for cancer theranostic applications

“…13 Recently, Collins et al reported that gold nanoparticles (NPs) can be used for RF-induced hyperthermia. 14 Rejinold et al summarized many nanomaterials (including gold nanomaterials), which can be used for RF hyperthermia in vitro. 15 However, the present study found that AuNRs with different aspect ratios (ARs) have different heating efficiencies induced by RF; therefore, in this study, AuNRs with a suitable AR were selected for RF-induced hyperthermia in vitro and in vivo.…”