Factors affecting the 13.56-MHz radio-frequency-mediated heating of gold nanoparticles

Towards a System for Tracking Drug Delivery Using Frequency Excited Gold Nanoparticles

“…The results demonstrate that it is possible to excite 5 nm AuNPs at 13.56 MHz and image them with EIT. It is known that 13.56 MHz could excite AuNPs at a depth of tens of centimeters which would permit tracking of AuNPs, even when they have penetrated deep inside the body thereby making them ideal for use as contrast agents to improve sensitivity of imaging inside the body or in drug delivery to various organs [10]. Their use, in conjunction with EIT measurements, proved the concept that the rate of change of conductivity in the presence of excited gold nanoparticles could be used as a diagnostic tool.…”

“…The RF absorption of AuNPs at 13.56 MHz depends on several factors including AuNP size, charge of the ligand shell, aggregation state, and presence of electrolytes [9]. According to McCoy et al [10] the generated heat from <2.5 nm oxidized AuNPs is through interactions of the spin magnetic moment with the oscillating magnetic field from a RF device. Sassaroli et al [10] in another study described how the electrophoretic motion of charged AuNPs acted upon by a time-dependent electric field can be a key factor for the increased RF absorption observed in dilute solutions of AuNPs.…”

“…According to McCoy et al [10] the generated heat from <2.5 nm oxidized AuNPs is through interactions of the spin magnetic moment with the oscillating magnetic field from a RF device. Sassaroli et al [10] in another study described how the electrophoretic motion of charged AuNPs acted upon by a time-dependent electric field can be a key factor for the increased RF absorption observed in dilute solutions of AuNPs. Although two heating models have emerged, neither the electrophoretic mechanism nor the magnetic mechanism has been comprehensively evaluated, including the possibility that both could be operating in some scenarios [7,10,11].…”

“…Since RF can penetrate more easily inside tissues than optical radiation, the ability to produce deep localized heating through the interaction of RF and AuNPs could have a significant impact in localized drug delivery and cancer treatment [14]. According to [10], deeper penetration of RF radiation into biological tissue (20–200 cm) is accomplished by the use of MHz frequencies, while scattering and attenuation of near-infrared (NIR) facilitates hyperthermia for the treatment of tumors that reside <10 cm under the skin [10]. Another study by Kanwar et al [15] emphasizes that thermal therapy with NIR energy is limited to the treatment of superficial tumors of less than 1–2 cm deep due to the significant attenuation of NIR light by biological tissues.…”

Electrophoretic Mechanism of Au25(SR)18 Heating in Radiofrequency Fields

“…Notably, the permittivity (and conductivity) of the solution, which are influenced by solvent structuring and ionic strength, have large effects on the ‘background heating’ rates of samples of nanoparticles in RF. 22–24…”