Studies on the Exposure of Gadolinium Containing Nanoparticles with Monochromatic X-rays Drive Advances in Radiation Therapy

Fuyuhiko Tamanoi,Kotaro Matsumoto,Ayumi Shiro,Tan Le Hoang Doan,Hiroyuki Saitoh

doi:10.3390/nano10071341

Abstract

While conventional radiation therapy uses white X-rays that consist of a mixture of X-ray waves with various energy levels, a monochromatic X-ray (monoenergetic X-ray) has a single energy level. Irradiation of high-Z elements such as gold, silver or gadolinium with a synchrotron-generated monochromatic X-rays with the energy at or higher than their K-edge energy causes a photoelectric effect that includes release of the Auger electrons that induce DNA damage—leading to cell killing. Delivery of high-Z elements into cancer cells and tumor mass can be facilitated by the use of nanoparticles. Various types of nanoparticles containing high-Z elements have been developed. A recent addition to this growing list of nanoparticles is mesoporous silica-based nanoparticles (MSNs) containing gadolinium (Gd–MSN). The ability of Gd–MSN to inhibit tumor growth was demonstrated by evaluating effects of irradiating tumor spheroids with a precisely tuned monochromatic X-ray.

Highlights

The nanotechnology that was initiated in 1960s has generated a variety of nanomaterials valuable for biomedical applications such as cancer therapy [1]
A new addition to these nanoparticles is a type of mesoporous silica nanoparticles that are surface attached with gadolinium [9]
It is interesting that the X-ray irradiation had little effect in the absence of gadolinium. These results suggest that the use of a monochromatic X-ray with a defined energy (50.25 keV in this case) in combination with gadolinium-loaded nanoparticles is effective in tumor destruction

Summary

Introduction

The nanotechnology that was initiated in 1960s has generated a variety of nanomaterials valuable for biomedical applications such as cancer therapy [1]. Advantageous properties of nanoparticles such as tumor targeting have important implication for radiation therapy. These nanoparticles have been evaluated in tissue culture models, in animal models and in clinical trials. Various nanoparticles loaded with high-Z elements have been developed over the years [11]. We will focus on gadolinium-loaded nanoparticles, as they provide valuable reagents as a radiation sensitizer, magnetic resonance imaging (MRI) enhancing agents and as a reagent for neutron therapy [12]. We will describe a recent study that utilized gadolinium-loaded mesoporous silica nanoparticles [9] and discuss potential significance of this study. Nanoparticles developed for irradiations other than X-rays will be discussed

Monochromatic X-ray and the Auger Effect

Further Potential of Using Gd–MSN

Irradiation Other than X-Rays and Development of Various Nanomaterials

Summary