Microdosimetric and radiobiological effects of gold nanoparticles at therapeutic radiation energies

Abstract

Purpose

The purpose of this study was to quantify the microscopic dose distribution surrounding gold nanoparticles (GNPs) irradiated at therapeutic energies and to measure the changes in cell survival in vitro caused by this dose enhancement.

Methods

The dose distributions from secondary electrons surrounding a single gold nanosphere and single gold nanocube of equal volume were both simulated using MCNP6. Dose enhancement factors (DEFs) in the 1 μm³ volume surrounding a GNP were calculated and compared between a nanosphere and nanocube and between 6 and 18 MV energies. This microscopic effect was explored further by experimentally measuring the cell survival of C-33a cervical cancer cells irradiated at 18 MV with varying doses of energy and concentrations of GNPs. Survival of cells receiving no irradiation, a 3 Gy dose, and a 6 Gy dose of 18 MV energy were determined for each concentration of GNPs.

Results

It was observed that the dose from electrons surrounding the gold nanocube surpasses that of a gold nanosphere up to a distance of 1.1 μm by 18.5% for the 18 MV energy spectrum and by 23.1% for the 6 MV spectrum. DEFs ranging from ∼2 to 8 were found, with the maximum DEF resulting from the case of the gold nanocube irradiated at 6 MV energy. Experimentally, for irradiation at 18 MV, incubating cells with 6 nM (0.10% gold by mass) GNPs produces an average 6.7% decrease in cell survival, and incubating cells with 9 nM (0.15% gold by mass) GNPs produces an average 14.6% decrease in cell survival, as compared to cells incubated and irradiated without GNPs.

Conclusion

We have successfully demonstrated the potential radiation dose enhancing effects in vitro and microdosimetrically from gold nanoparticles.

Keywords:

• Gold nanoparticles
• Monte Carlo simulations
• dose enhancement factor
• radiation therapy
• microdosimetry

This article is referred to by:

Article commentary on ‘Microdosimetric and radiobiological effects of gold nanoparticles at therapeutic radiation energies’ [T.M. Gray et al., IJRB 2023, 99(2), 308–317]

Acknowledgments

The authors would like to thank Dr. Kelly Nash at the University of Texas at San Antonio for all of her advice on cell culture and cell survival assays. The authors would also like to thank Alejandro Morales Betancourt for his assistance involving lab equipment for cell culture and cell culture supplies as well as all of his advice on cell culture care. The authors acknowledge the University of Texas at San Antonio Kleberg Advanced Microscopy Center for support during this work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the San Antonio Medical Foundation, San Antonio Life Sciences Institute, and the National Institutes of Health under Grant R25-GM060655-09.

Notes on contributors

Tara M. Gray

Tara M. Gray recently received her Ph.D. in Physics from the University of Texas at San Antonio after receiving her master’s degree in Medical Physics from the University of Toledo. She currently works at the Cleveland Clinic in Cleveland, Ohio as a Resident in Therapeutic Medical Physics.

Shaquan David

Shaquan David is a doctoral candidate in the Department of Physics and Astronomy at the University of Texas at San Antonio.

Nema Bassiri

Nema Bassiri obtained his Ph.D. from the University of Texas Health Science Center at San Antonio. He currently works as a medical physics resident at the University of California, Davis.

Devanshi Yogeshkumar Patel

Devanshi Yogeshkumar Patel is an undergraduate researcher at the University of Texas at San Antonio.

Neil Kirby

Neil Kirby is an associate professor in the Department of Radiation Oncology at the University of Texas Health Science Center at San Antonio.

Kathryn M. Mayer

Kathryn M. Mayer is an associate professor in the Department of Physics and Astronomy at the University of Texas at San Antonio.