Radiotherapy used in cancer treatment is a promising treatment method, albeit rather indiscriminate. Indeed, it affects neighbouring healthy tissues and tumours alike. Researchers have thus been exploring the possibilities of using various radio-sensitizers; these nanoscale entities focus the destructive effects of radiotherapy more specifically on tumour cells. In a study published in EPJ D, physicists have now shown that the production of low-energy electrons by radio-sensitizers made of carbon nanostructures hinges on a key physical mechanism referred to as plasmons - collective excitations of so-called valence electrons; a phenomenon already documented in rare metal sensitizers. This reseach was conducted by Alexey Verkhovtsev, affiliated with the MBN Research Center in Frankfurt, Germany and A.F. Ioffe Physical-Technical Institute in St Petersburg, Russia and an international team.
Nanoparticle radio-sensitizers are nanoscale compounds, typically composed of rare metals such as coated gold, platinum, or gadolinium. Alternatives sensitizers could be made of carbon-based nanostructures, such as fullerenes or nanotubes, provided they are biocompatible and non-toxic. Previous studies have revealed that gold and platinum nanoparticles produce a large number of electrons via the plasmon excitation mechanism. In the case of a carbon nanoparticle, this phenomenon yields electrons with higher energy than pure metals, thus inducing greater biological damage.
In this study, the authors analysed the spectra of secondary electrons emitted from a carbon nanoparticle composed of fullerite, a crystalline form of C60 fullerene, irradiated by an ion beam consisting of fast protons. They quantified the electron yield in a broad kinetic energy range, using several different theoretical and numerical approaches. They found that a medium with an embedded carbon nanoparticle results in a number of low-energy electrons several times higher than that emitted by pure water. This may lead to the development of novel types of sensitizers composed of metallic and carbon-based parts.
Reference: Alexey Verkhovtsev, Sally McKinnon, Pablo de Vera, Eugene Surdutovich, Susanna Guatelli, Andrei V. Korol, Anatoly Rosenfeld, and Andrey V. Solov'yov (2015), Comparative analysis of the secondary electron yield from carbon nanoparticles and pure water medium, Eur. Phys. J. D 69: 116, DOI: 10.1140/epjd/e2015-50908-y