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Nano and Micro Technologies

The Application of Hafnium-Based Nanoparticles in the Delivery of Radiotherapy to Cancer Cells as Assessed by the Dose Enhancement Factor (DEF)

(J-378) The Application of Hafnium-Based Nanoparticles in the Delivery of Radiotherapy to Cancer Cells as Assessed by the Dose Enhancement Factor (DEF)

Friday, October 13, 2023

9:30 AM – 10:30 AM PDT

Location: Exhibit Hall - Row J - Poster # 378

Presenting Author(s)

RK

Rohan Kakaria (he/him/his)

Student Researcher
Pennsylvania State University, Department of Materials Science and Engineering
Mechanicsburg, Pennsylvania, United States

Introduction:: Radiotherapy is a common and effective modality of cancer treatment that acts by damaging DNA in cancerous cells, causing cell death, via delivery of high doses of energy. Nonetheless, radiotherapy can result in harm to surrounding healthy tissue. Hence, there has been an emerging interest in the use of high atomic number (Z) nanoparticles, such as hafnium, to improve accurate delivery of radiation and without compromising healthy cells. The main advantage of high-Z nanoparticles being introduced into tumor cells is the enhancement of therapeutically relevant energy-matter interactions, which leads to the magnification of radiation induced damage in tumor cells. A critical factor in determining this amount of energy absorption is the mass absorption coefficient, which increases as atomic number increases, making hafnium nanoparticles, the subject of the study, very effective agents in radiotherapy. The dose enhancement factor (DEF), the ratio of the deposition in medium with nanoparticles to the deposition without nanoparticles, takes into account the mass absorption coefficient of the nanoparticles, as well as the medium in which the nanoparticles are contained. This allows us to theoretically determine the relative radiation enhancement with respect to the amount of hafnium and incident energy. In efforts to improve radiotherapeutic techniques for targeting purely cancerous tissue, by calculating DEF values, which correlated with increased selectivity in cancerous cell apoptosis, we investigated the efficacy of hafnium-based nanoparticles for radiotherapy in two distinct media — alanine, used for theoretical and experimental purposes, and water, used for biological relevance.

Materials and Methods::

In this study, we performed theoretical DEF calculations by first dividing the mass absorption coefficients of the nanocomposite — hafnium — by the mass absorption coefficients of the respective media — either alanine, a more empirically supported medium, or water, a more biologically relevant medium. Then, this value was multiplied by the ratio of the relative mass proportions of the nanocomposite to the specific medium in the solution mixture, resulting in a numerical value for the dose enhancement factor. The section of the National Institute of Standards and Technology (NIST) database labeled “X-Ray Mass Attenuation Coefficients” was utilized to obtain the specific mass absorption coefficients. In the aforementioned DEF formula included below, the symbols have the following representations: (μen/Q)i,hv indicates the mass absorption coefficient of a material i at a specific energy, ⍴i symbolizes the relative mass proportion of a material i in the solution mixture.

DEF = (enQ)Hf,hv Hf(enQ)Med,hv Med

Results, Conclusions, and Discussions:: The methodology we used demonstrated that, in the alanine solution, the DEF value increased as the hafnium relative mass composition increased for each photon energy level, as shown in Figure 1(a). In the water solution, the DEF also increased as the hafnium relative mass composition increased, as shown in Figure 1(b). However, the numerical DEF values for the corresponding hafnium mass composition and photon energy coordinates were comparatively greater in the alanine medium versus the water medium. Another trend observed, regardless of the medium, an optimally higher DEF value will occur at a lower photon energy. DEF proves to be a useful tool to express energy deposition in our study, specifically that of hafnium, which carries a high atomic number. Hafnium-based nanoparticles in an alanine medium appear to be quite optimal in radiotherapy for cancer therapy due to their high DEF values.

Following this investigation, we have demonstrated that hafnium, which is a high atomic number element, can be utilized in nanoparticles to improve and optimize the delivery of radiotherapy to cancer cells. As found in this study, DEF values are maximized at low photon energy and high hafnium mass composition of the nanoparticles. As such, since high DEF values indicate more effective targeted delivery of radiation to cancer cells, hafnium proves to be a promising element used in nanoparticles to treat cancer cells via radiotherapy.

Acknowledgements (Optional): : We would like to thank the Pennsylvania State University for providing funding and for supporting this research.

References (Optional): :

1. Guidelli, E.J. and Baffa, O. (2014) ‘Influence of photon beam energy on the dose enhancement factor caused by gold and silver nanoparticles: An experimental approach’, Medical Physics, 41(3), p. 032101. doi:10.1118/1.4865809.

2. X-ray mass attenuation coefficients (2022) NIST. Available at: https://www.nist.gov/pml/x-ray-mass-attenuation-coefficients (Accessed: 23 July 2023).