A Guide for Using Transmission Electron Microscopy for Studying the Radiosensitizing Effects of Gold Nanoparticles In Vitro.

Ioanna Tremi,Sofia Georgitsopoulou,Vasilios Georgakilas,Vassilis G Gorgoulis,Nefeli Lagopati,Alexandros G Georgakilas,Sophia Havaki

doi:10.3390/nano11040859

Abstract

The combined effects of ionizing radiation (IR) with high-z metallic nanoparticles (NPs) such as gold has developed a growing interest over the recent years. It is currently accepted that radiosensitization is not only attributed to physical effects but also to underlying chemical and biological mechanisms’ contributions. Low- and high-linear energy transfer (LET) IRs produce DNA damage of different structural types. The combination of IR with gold nanoparticles may increase the clustering of energy deposition events in the vicinity of the NPs due to the production mainly of photoelectrons and Auger electrons. Biological lesions of such origin for example on DNA are more difficult to be repaired compared to isolated lesions and can augment IR’s detrimental effects as shown by numerous studies. Transmission electron microscopy (TEM) offers a unique opportunity to study the complexity of these effects on a very detailed cellular level, in terms of structure, including nanoparticle uptake and damage. Cellular uptake and nanoparticle distribution inside the cell are crucial in order to contribute to an optimal dose enhancement effect. TEM is mostly used to observe the cellular localization of nanoparticles. However, it can also provide valuable insights on the NPs’ radiosensitization pathways, by studying the biochemical mechanisms through immunogold-labelling of antigenic sites at ultrastructural level under high resolution and magnification. Here, our goal is to describe the possibilities, methodologies and proper use of TEM in the interest of studying NPs-based radiosensitization mechanisms.

Highlights

ionizing radiation (IR) is widely used both for therapeutic and for diagnostic purposes.Despite the advantages in cancer treatment exposure to IR is often associated with adverse health effects [1]
We aim to introduce Transmission electron microscopy (TEM) as an efficient way to study the biochemical effects of gold nanoparticles after ionizing radiation in vitro, by summarizing the most important experimental procedures accompanying TEM, along with their protocols
Cells were grown in Dulbecco’s modified MEM (DMEM) medium supplemented with 10% fetal bovine serum (FBS), 1% L-glutamine and antibiotics

Summary

Introduction

Despite the advantages in cancer treatment exposure to IR is often associated with adverse health effects [1]. This is due to the fact that radiation damage cancer tissue and healthy tissue. The idea of using radiosensitizers to enhance radiation effect in tumor therapy, while. Nanomaterials 2021, 11, 859 minimizing the damage to the normal tissue, has gained a lot of attention [2,3]. Metal nanoparticles (NPs) such as gold (high atomic number Z = 79) can increase radiosensitivity by increasing local energy deposition by using differential absorption coefficient of high atomic number material, compared to the soft tissue [4]. In this paper we used colloidal solutions of two types of gold nanoparticles (GNPs), citrate-capped GNPs and PEG-capped

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Conclusion