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Several ECT* researchers, covering specialities like nuclear physics, atomic and molecular physics, or radiation interaction with matter, participated at La Notte dei Ricercatori (European Researchers’ Night), where they could explain, in an accessible language, their research projects to the Trento citizens attending the MUSE.

On Friday September 24^th, the whole Europe celebrated the great importance that science has in our society, by letting the researchers themselves explain their work to the general public at the European Researchers’ Night in many cities all along the continent. The research centres of the Autonomous Province of Trento did not miss this special occasion, and Museo delle Sciencie (MUSE), Fondazione Bruno Kessler (FBK), Università di Trento and Fondazione Edmund Mach joined the SHARPER Night initiative (SHAring Researchers’ Passion for Engaging Responsiveness) to organise La Notte dei Ricercatori in the modern quarter of Le Albere, in Trento.

Read the full news through the Outreach tab.

Nanoparticles can be used to increase the effects of hadrontherapy exactly where they are needed: in the cancer cells. This is so, because they can be coated with organic molecules which selectively target the cancer cells, going into them in much larger proportion than in the healthy cells. Then, when the body is irradiated with an ion beam, the interaction between the beam and the nanoparticles can produce an increase in the number of secondary species (electrons and free radicals) which damage the cell genetic material, increasing the cancer cell-killing ability of the treatment.

Among the materials which are being investigated for these radioenhancing nanoparticles, cerium oxides (ceria) are one of the most promising. It has been tested experimentally that ceria nanoparticles can, on the one hand, radiosensitise cancer cells while, on the other hand, radioprotect healthy cells.

To understand these complex radiosensitisation and radioprotection mechanisms is very challenging, but it is clear that a first step in this direction is to understand how charged particles (particularly electrons, which are abundantly produced by radiation) interact elastically and, mainly, inelastically with cerium oxides.

In our recent publication in the journal Physical Chemistry Chemical Physics, we have investigated from first principles the electronic excitation spectrum of both phases of ceria (CeO2 and Ce2O3), i.e., its Energy-Loss Function (ELF), by means of linear-response time-dependent density functional theory (TDDFT) calculations. For CeO2, material for which there are optical measurements, we found excellent agreement with experiment when local field effects are included in the calculations, while we also predicted the ELF of the more unknown Ce2O3.

These ELFs have been used to obtain the inelastic scattering probabilities of electrons in these materials, which, together with elastic scattering probabilities from the Mott theory, have provided the input for precise Monte Carlo simulations of the electron transport in ceria. These simulations have been used to try to reproduce the reflection electron energy loss spectrum experimentally determined for ceria (REELS, a very well-known electron analysis and spectroscopic technique). We found that the REELS spectrum can be fairly well reproduced by simulations which, moreover, allow interpreting the origin of the different features of the spectrum, which come from different electronic excitations of both CeO2 and Ce2O3. As it was suspected in the experimental work, the ceria material commonly used turns out to be a mix of these two phases of cerium oxide.

We expect that these calculations and simulations will help in the future to understand the physical mechanisms of ceria nanoparticle radiosensitisation in hadrontherapy.

The open access article, which has been showcased on the PCCP back cover, can be downloaded, free of charge, in the following link:

https://pubs.rsc.org/en/content/articlelanding/2021/CP/D1CP01810H

or through the Publications tab.

Image reproduced by permission of the authors from Phys. Chem. Chem. Phys., 2021, 23, 19173, DOI: 10.1039/D1CP01810H

Pablo gave the contributed Special Report talk Excitation and ionisation cross-sections of condensed-phase biomaterials by electrons down to very low energy at ViCPEAC 2021, talking about the recent work Excitation and ionisation cross-sections in condensed-phase biomaterials by electrons down to very low energy: application to liquid water and genetic building blocks, which is available through the Publications tab.

Pablo gave the invited talk Electronic interactions of swift ions and their secondary electrons in biologically relevant materials at ISIAC 2021, talking about recent works which can be found on the Publications tab.

Pablo gave the contributed talk Monte Carlo simulation of cerium oxides REELS based on accurate ab initio electronic excitation spectra at ECASIA 2021, talking about the recent work Electronic excitation spectra of cerium oxides: from ab initio dielectric response functions to Monte Carlo charge transport simulations, which preprint is available in arXiv.

Nanoparticles are objects (typically nearly spherical) formed by hundreds or thousands of atoms, having diameters of a few, tens or hundreds of nanometers, hence their name. They can be made up of different metals or of other materials, like oxides. Nanoparticles are the subject of intensive research since several decades, as they present very peculiar characteristics, both for the fundamental science and for many applications.

Fundamentally, they are objects which are not bulk materials, but neither individual atoms, and thus they present very interesting and unexpected properties, as for example “magic numbers”: nanoparticles made up of specific numbers of atoms are much more stable than others (even being different by just one atom), which reflects the interplay of fundamental interactions arising from geometry or the closure of electronic shells.

From the applied point of view, nanoparticles are being used for numerous technological developments, from catalysis in chemistry, components of nanoelectronic devices or as enhancers for cancer radiotherapy. Of course, many of these applications require the deposition of the nanoparticles on a surface, and this apparently simple, but really complex process, can affect the properties and function of the nanoparticle. Therefore, the deposition process has to be well understood.

With my former MSc student Yannick Fortouna (https://www.bioremia.eu/.../our.../esr-1-yannick-fortouna) and our colleagues at MBN Research Center (Frankfurt, Germany), we did a computational study of the deposition of sodium nanoparticles on magnesium oxide substrates by means of molecular dynamics simulations. This simulation technique allows obtaining a lot of information which otherwise could be difficult to get from experiments, such as the change in nanoparticle shape and structure as a function of landing velocity, the heating of the nanoparticle upon collision and the heat exchange with the substrate, etc. All these aspects have been studied in the work which was just published yesterday in the journal Theoretical Chemistry Accounts, and that you can access, if you are interested, through the following link:

https://rdcu.be/cmkKR

or through the Publications tab.

The image shows some examples of simulated trajectories of the nanoparticle deposition, in which different regimes can be observed as the energy is increased, such as soft landing without melting (b-c), harder landing with impact-induced melting and droplet formation followed by recrystallization (d-e), and multifragmentation of the nanoparticle due to a very energetic impact (f). Image taken from the mentioned work, first published in Theoretical Chemistry Accounts, volume 140, page 84, 2021, by Springer Nature.

Last Tuesday, April 27th, during a visit to Alicante, Pablo had the opportunity to give a talk to (and chat with) the Physics and Chemistry students of the 2nd grade of “Bachillerato” (preparatory courses to access the university studies) of the Severo Ochoa highschool in Elche, who will soon have to take important decisions about their university studies.

They talked about NanoEnHanCeMent, but also about how science works and how a research career is accessed (and developed).

Thank you all for your attention, and thank you very much for the opportunity to their excelent teacher, Ángel Ávila Freire.

In January, I introduced you our recent work in which we analysed, by means of ab initio and Monte Carlo simulations, the clustered DNA damage on the nanoscale produced by carbon ion irradiation, of relevance in hadrontherapy.

Despite the importance of that work (published in the prestigious Journal of Physical Chemistry Letters, and available through the Publications tab), in which a very precise description of the electronic excitation spectrum of liquid water was obtained by time-dependent DFT, and then used to evaluate the relative role of physical mechanism on complex biodamage, current Monte Carlo simulations in this field present some limitations. These limitations are related to the fact that most simulations need to approximate the DNA properties as if it was water, since the probabilities for electron interaction with DNA itself are not well known.

Today, I bring you our recent publication in the journal Physical Chemistry Chemical Physics addressing this important problem, which has been highlighted in the “2021 PCCP Hot Articles” list, as well as in the journal’s outer back cover (in the image). The “2021 PCCP Hot Articles” list gathers all the articles which are considered of special relevance by the journal’s editors and referees.

In the new article, we present a theoretical model which allows obtaining the interaction probabilities for electrons, in a wide energy range, with the molecular components of DNA (and other important biomaterials) in the condensed phase. The results of the model compare very well with a large collection of experimental data, confirming its predictive capabilities.

The new model will allow performing more realistic and accurate Monte Carlo simulations of DNA damage, which is essential for reaching a deeper understanding of the physical and chemical mechanisms underlying radiotherapy, needed to develop more effective treatments.

You can access the full open access publication, free of charge, in the following link:

https://doi.org/10.1039/D0CP04951D

or through the Publications tab.

Image reproduced by permission of the authors from Phys. Chem. Chem. Phys., 2021, 23, 5079, DOI: 10.1039/ D0CP04951D

Hadrontherapy is a cutting-edge modality of radiotherapy in which energetic ion beams (protons, as used in the Trento protontherapy centre, as well as carbon ions) are employed to kill cancer cells while sparing surrounding healthy areas. The depth-dose curve of ions in tissue presents a sharp peak towards the end of their trajectories (the Bragg peak), which allows the precise deposition of energy in the tumour. Ion beams also kill cells more effectively than photons do for the same delivered dose. These characteristics arise from a concatenation of physico-chemical events happening on different space, time and energy scales, comprising the propagation of the ion beam in the body, the excitation and ionisation of the biological materials, the transport of secondary electrons and free radicals in the micro- and nanoscale, and the damage these can produce to the sensitive DNA molecules. To gain a deeper understanding of these basic mechanisms, computational models have been developed over the years in which different techniques are used to address each specific problem: Monte Carlo simulations for describing radiation transport, dielectric response theory and time-dependent density functional theory for treating electronic excitations, or molecular dynamics for simulating radiation effects at the molecular level. A review of these models and their usefulness in the context of hadrontherapy will be given in this seminar.

https://www.ectstar.eu/seminars/computational-science-to-uncover-the-physical-and-chemical-processes-underlying-hadrontherapy/

Last month, the prestigious Journal of Physical Chemistry Letters published online our recent contribution to the fundamental understanding of carbon-ion beam radiotherapy.

Pablo de Vera tells you all about the main details of the published research in the following short video produced by the American Chemical Society, that you can watch in the applet on the left or in the following link:

https://youtu.be/7kG7fc-1MTw

In summary, complete and highly-accurate simulations have been performed of the physical processes underlying DNA damage during carbon-ion beam radiotherapy, combining first principles calculations (using time-dependent density functional theory) and Monte Carlo radiation transport simulations.

As a result, the relative role of different physical mechanisms (namely, ionizations, electronic excitations and dissociative electron attachment) on DNA complex damage on the nanoscale has been determined. Experimentally, only ionizations can be easily measured, and calculations are able to reproduce such measurements. Additionally, simulations help to understand how much extra biodamage is actually produced by other mechanisms different from ionization during carbon irradiation.

You can also access the full open access publication, free of charge, in the following link:

https://pubs.acs.org/doi/abs/10.1021/acs.jpclett.0c03250

Apart from radiotherapy, the use of radiation beams has many other useful applications. For example, accelerated electron beams are commonly used for imaging micro- and nanostructures by electron microscopy, but not only. Did you know that electron beams can also be used to fabricate nanostructures?

One of these cutting edge techniques is called Focused Electron Beam Induced Deposition (FEBID), in which a nanometric electron beam irradiates organometallic precursor molecules deposited on a substrate, in order to break them, liberate their metal atoms and create metallic nanostructures featuring unique electronic, magnetic, superconducting, mechanical or optical properties. One of the key steps for the fabrication is to be able to control, and if possible predict, the size, microstructure and atomic composition of the nanostructures as a function of the electron beam characteristics.

This is the topic of the published paper, reporting a collaboration between ECT* (Trento, Italy), MBN Research Center (Frankfurt, Germany), and the Universities of Oldenburg (Germany), Murcia (Spain) and Alicante (Spain). The paper recently published in the journal Scientific Reports describes the use of a novel multiscale simulation methodology which couples Monte Carlo calculations for radiation transport (with the code SEED) with irradiation‑driven molecular dynamics (with the code MBN Explorer) for simulating irradiation-driven chemistry with atomistic resolution. The method has been shown to be able to predict with high accuracy the structure and composition of the nanostructures created by electron irradiation of W(CO)6 precursor molecules on top of a silicon dioxide substrate.

If you are interested, you can download the paper for free here:

https://www.nature.com/articles/s41598-020-77120-z

Also, this work was recently explained in the meeting by the Condensed Matter Divisions of the Spanish Royal Physical Society and of the European Physical Society, CMD2020GEFES. You can see the presentation with more details in the following link (from minute 17:22):

https://youtu.be/se_epIuHJWQ?list=PLWIVj90xdDE-0js8Ui1Z__uPk3Vt4BYy6&t=1042

On November 1^st, Pablo de Vera arrived to Trento to start his Marie Curie Individual Fellowship project, NanoEnHanCeMent, to be developed at the European Centre for Theoretical Studies in Nuclear Physics and Related Areas (ECT*), part of the Fondazione Bruno Kessler.

The University of Murcia (partner of this project, and former institution where Pablo de Vera was doing his research and teaching) has promoted this new project by putting it in the very front page of its official website (as per yesterday, November 5th 2020). In the next link you can find the press release the University of Murcia has spread, and which has made its way to some regional media as well:

https://www.um.es/fr/web/ucc/-/la-umu-investiga-los-efectos-de-nanoparticulas-metalicas-en-la-terapia-del-cancer-mediante-haces-de-ion-1?inheritRedirect=true&redirect=%2Fweb%2Fucc%2Fnoticias%2Fum

This news may serve as an introduction to this new project, of which you will know more details soon. Meanwhile, basic information can be looked up in the following link:

https://cordis.europa.eu/project/id/840752