Nav: Home

Slow electrons to combat cancer

August 22, 2019

Ion beams are often used today in cancer treatment: this involves electrically charged atoms being fired at the tumour to destroy cancer cells. Although, it's not actually the ions themselves that cause the decisive damage. When ions penetrate through solid material, they can share part of their energy with many individual electrons, which then continue to move at relatively low speed - and it is precisely these electrons that then destroy the DNA of the cancer cells.

This mechanism is complex and not yet fully understood. Researchers at TU Wien have now been able to demonstrate that a previously little-observed effect actually plays a pivotal role in this context: owing to a process called interatomic Coulombic decay, an ion can pass on additional energy to surrounding atoms. This frees a huge number of electrons, with precisely the right amount of energy to cause optimal damage to the DNA of the cancer cells. In order to understand and further improve the particular effectiveness of ion therapy, this mechanism absolutely has to be taken into account. The results were recently published in the specialist publication Journal of Physical Chemistry Letters.

One fast particle - or lots of slow ones

When a charged particle penetrates a material at great speed - such as human tissue - it leaves a giant atomic mess in its wake: "This can trigger a whole cascade of effects," says Janine Schwestka, lead author of the recent publication, who is currently working on her dissertation in the team led by Prof. Friedrich Aumayr and Dr Richard Wilhelm. When the ion moves through other atoms, these and other particles can become ionised, fast electrons fly around and then collide with other particles. Ultimately, a fast, charged ion can trigger a particle shower of hundreds of electrons each with much lower energy.

In everyday life, we are used to fast objects having more dramatic effects than slower ones - a football kicked with full force causes much more damage in a china shop than one that is gently rolled in. At an atomic level, however, this does not apply: "The likelihood of a slow electron destroying a DNA strand is much greater. Conversely, an extremely fast electron normally just flies right past the DNA molecule without leaving a trace," explains Janine Schwestka.

From one electron shell to another

The team from TU Wien recently took a closer look at an extremely special effect - namely, interatomic Coulombic decay. "The ion's electrons can assume different states. Depending on how much energy they have, they can be located in one of the inner shells, close to the nucleus, or in an outer shell," says Janine Schwestka. Not all possible electron spaces are occupied. If an electron shell in the medium energy range is free, an electron can then cross over to there from a shell with higher energy. This releases energy, which can then be passed to the material via interatomic Coulombic decay: "The ion transfers this energy to several atoms in the direct vicinity at the same time. One electron is detached from each of these atoms but because the energy is divided among several atoms we are talking about lots of really slow electrons," explains Schwestka.

Xenon and graphene

With the help of an ingenious experimental setup, it has now been possible to prove the efficacy of this process. Multiply charged xenon ions are shot at a graphene layer. Electrons from the outer xenon shells switch to a position in another shell with less energy, causing electrons to be detached from numerous carbon atoms in the graphene layer, which are then recorded by a detector, so as to measure their energy. "In fact, in this way, we were able to show that interatomic Coulombic decay plays a vital role in generating a large number of free electrons in the material," says Prof. Friedrich Aumayr.

In order to correctly describe the interaction of ion beams with solid materials or organic tissues, this effect absolutely must be taken into account. This is important, on one hand, for optimising ion beam therapies for treating cancer, but also for other important areas, such as protecting the health of space station crews, where you are exposed to constant particle bombardment from cosmic radiation.
-end-
Original publication

J. Schwestka et al., Charge-Exchange-Driven Low-Energy Electron Splash Induced by Heavy Ion Impact on Condensed Matter, J. Phys. Chem. Lett. 10 (2019) 4805 https://doi.org/10.1021/acs.jpclett.9b01774

Contact

Janine Schwestka
Institute of Applied Physics
TU Wien
Wiedner Hauptstraße 8-10, 1040 Vienna, Austria
T +43 (0)1 58801 13435
janine.schwestka@tuwien.ac.at

Vienna University of Technology

Related Science Articles:

75 science societies urge the education department to base Title IX sexual harassment regulations on evidence and science
The American Educational Research Association (AERA) and the American Association for the Advancement of Science (AAAS) today led 75 scientific societies in submitting comments on the US Department of Education's proposed changes to Title IX regulations.
Science/Science Careers' survey ranks top biotech, biopharma, and pharma employers
The Science and Science Careers' 2018 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.
Science in the palm of your hand: How citizen science transforms passive learners
Citizen science projects can engage even children who previously were not interested in science.
Applied science may yield more translational research publications than basic science
While translational research can happen at any stage of the research process, a recent investigation of behavioral and social science research awards granted by the NIH between 2008 and 2014 revealed that applied science yielded a higher volume of translational research publications than basic science, according to a study published May 9, 2018 in the open-access journal PLOS ONE by Xueying Han from the Science and Technology Policy Institute, USA, and colleagues.
Prominent academics, including Salk's Thomas Albright, call for more science in forensic science
Six scientists who recently served on the National Commission on Forensic Science are calling on the scientific community at large to advocate for increased research and financial support of forensic science as well as the introduction of empirical testing requirements to ensure the validity of outcomes.
World Science Forum 2017 Jordan issues Science for Peace Declaration
On behalf of the coordinating organizations responsible for delivering the World Science Forum Jordan, the concluding Science for Peace Declaration issued at the Dead Sea represents a global call for action to science and society to build a future that promises greater equality, security and opportunity for all, and in which science plays an increasingly prominent role as an enabler of fair and sustainable development.
PETA science group promotes animal-free science at society of toxicology conference
The PETA International Science Consortium Ltd. is presenting two posters on animal-free methods for testing inhalation toxicity at the 56th annual Society of Toxicology (SOT) meeting March 12 to 16, 2017, in Baltimore, Maryland.
Citizen Science in the Digital Age: Rhetoric, Science and Public Engagement
James Wynn's timely investigation highlights scientific studies grounded in publicly gathered data and probes the rhetoric these studies employ.
Science/Science Careers' survey ranks top biotech, pharma, and biopharma employers
The Science and Science Careers' 2016 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.
Three natural science professors win TJ Park Science Fellowship
Professor Jung-Min Kee (Department of Chemistry, UNIST), Professor Kyudong Choi (Department of Mathematical Sciences, UNIST), and Professor Kwanpyo Kim (Department of Physics, UNIST) are the recipients of the Cheong-Am (TJ Park) Science Fellowship of the year 2016.
More Science News and Science Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

In & Out Of Love
We think of love as a mysterious, unknowable force. Something that happens to us. But what if we could control it? This hour, TED speakers on whether we can decide to fall in — and out of — love. Guests include writer Mandy Len Catron, biological anthropologist Helen Fisher, musician Dessa, One Love CEO Katie Hood, and psychologist Guy Winch.
Now Playing: Science for the People

#543 Give a Nerd a Gift
Yup, you guessed it... it's Science for the People's annual holiday episode that helps you figure out what sciency books and gifts to get that special nerd on your list. Or maybe you're looking to build up your reading list for the holiday break and a geeky Christmas sweater to wear to an upcoming party. Returning are pop-science power-readers John Dupuis and Joanne Manaster to dish on the best science books they read this past year. And Rachelle Saunders and Bethany Brookshire squee in delight over some truly delightful science-themed non-book objects for those whose bookshelves are already full. Since...
Now Playing: Radiolab

An Announcement from Radiolab