Study of absorption of radio frequency field by gold nanoparticles and nanoclusters in biological medium

ABSTRACT

Gold nanoparticles (AuNPs) and gold nanoclusters (AuNCs) are gaining interest in medical diagnosis and therapy as they are bio-compatible and are easy to functionalize. Their interaction with radiofrequency (RF) field for hyperthermia treatment is ambiguous and needs further investigation. A systematic study of the absorption of capacitive RF field by AuNPs and AuNCs dispersed in phosphate-buffered saline (PBS) is reported here in tissue mimicking phantom. The stability of AuNPs and AuNCs dispersed in PBS was confirmed for a range of pH and temperature expected during RF hyperthermia treatment. Colloidal gold solutions with AuNPs (10 nm) and AuNCs (2 nm), and control, i.e. PBS without nanogold, were loaded individually in 3 ml wells in a tissue phantom. Phantom heating was carried out using 27 MHz short-wave diathermy equipment at 200 and 400 W for control and colloidal gold solutions. Experiments were conducted for colloidal gold at varying gold concentrations (10–100 µg/ml). Temperature rise measured in the phantom wells did not show dependence on the concentration and size of the AuNPs. Furthermore, temperature rise recorded in the control was comparable with the measurements recorded in both nanogold suspensions (2, 10 nm). Dielectric property measurements of control and colloidal gold showed <3% difference in electrical conductivity between the control and colloidal gold for both nanoparticle sizes. From the measurements, it is concluded that AuNPs and AuNCs do not enhance the absorption of RF-capacitive field and power absorption observed in the biological medium is due to the ions present in the medium.

KEYWORDS:

• Capacitive heating
• colloidal gold
• diathermy
• hyperthermia
• nanoclusters
• nanoparticles
• radiofrequency
• thermal therapy

Acknowledgments

The authors thank Mr. Vikram Melapudi, GE India Technology Center Pvt. Ltd., for dielectric property measurement, and Prof. A. Gopalakrishnan, Prof. Suresh Rayala, Prof. Edamana Prasad and National Centre for Catalysis Research (NCCR) at the Indian Institute of Technology Madras for providing access for AuNPs and AuNCs preparation and characterization.

Disclosure Statement

The authors report no conflicts of interest.

Additional information

Funding

This work was sponsored  by  Indian Institute of Technology Madras under the grant number, EDD0008422RMFXKAVT.