Modelling swift charged particles interaction with biologically-relevant materials for a deeper understanding of ion-beam radiation biodamage

An accurate modelling of swift charged particles (ions and their secondary electrons) interaction with biomaterials, and with other relevant targets such as radiosensitisers, is necessary for a better understanding (and possibly improvement) of proton- and hadrontherapy [1, 2]. This modality of radiotherapy, available in Trento since 2014, features a dose distribution and tumour cell killing probability superior to the conventionally used X-rays, due to the characteristic physico-chemical interactions initiated in the medium by the swift ions. The latter span over different space, time and energy scales, making their study challenging [1]: while the propagation of the primary ion beam happens on the macroscopic scale, the main processes behind clustered DNA damage and cell death (electronic excitations, generation and transport of large numbers of secondary electrons and free radicals, etc.) occur on nanometre distances around ion tracks. Thus, a detailed simulation of this chain of processes underlying ion-beam biodamage requires the combination of different computational techniques. Monte Carlo simulations are very effective tools for describing ion and secondary electron transport in condensed matter [3, 4], but their accuracy strongly depends on the quality of the interaction probabilities (cross sections) with which they are fed. The dielectric response theory, together with time- dependent density functional theory, are versatile and reliable methods for calculating the electronic excitation and ionisation cross sections, including the description of the energy and angular distributions of secondary electrons [5, 6], as well as the treatment of very low energy electron transport [7]. At the atomistic level, biomolecular damage can be dealt with by classical and reactive molecular dynamics simulations [8]. The combination of these methodologies becomes especially important for the fundamental study of newly explored treatment modalities heavily relying on nanoscale phenomena, such as the use of nanoparticles as enhancers of hadrontherapy, whose working mechanisms are still not well understood [2]. In the present contribution, the above mentioned methods will be reviewed, with examples of their application to the study of different aspects of the problem. References [1] A. V. Solov’yov (ed.) Nanoscale Insights into Ion-Beam Cancer Therapy (Springer, 2017) [2] S. Lacombe, E. Porcel, E. Scifoni, Cancer Nanotechnology 7 (2016) 8 [3] P. de Vera, I. Abril, R. Garcia-Molina, Radiation Research 180 (2018) 282 [4] M. Dapor, Transport of Energetic Electrons in Solids. Computer Simulation with Applications to Materials Analysis and Characterization, 3rd ed (Springer, 2020) [5] P. de Vera, R. Garcia-Molina, I. Abril, Physical Review Letters 114 (2015) 018101 [6] S. Taioli, P. E. Trevisanutto, P. de Vera, S. Simonucci, I. Abril, R. Garcia-Molina, M. Dapor, Journal of Physical Chemistry Letters 12 (2021) 487 [7] P de Vera I. Abril, R Garcia-Molina, Physical Chemistry Chemical Physics 23 (2021) 5079 [8] P. de Vera, E. Surdutovich, A. V. Solov’yov, Cancer Nanotechnology 10 (2019) 5