Since a few breakthroughs in the fundamental understanding of the effects of swift heavy ions (SHIs) decelerating in the electronic stopping regime in the matter have been achieved in the last decade, it motivated us to review the state-of-the-art approaches in the modeling of SHI effects. The SHI track kinetics occurs via several well-separated stages and spans many orders of magnitude in time: from attoseconds in ion-impact ionization depositing an extreme amount of energy in a target to femtoseconds of electron transport and hole cascades, to picoseconds of lattice excitation and response, to nanoseconds of atomic relaxation, and even longer times of the final macroscopic reaction. Each stage requires its own approaches for quantitative description. We discuss that understanding the links between the stages makes it possible to describe the entire track kinetics within a hybrid multiscale model without fitting procedures. The review focuses on the underlying physical mechanisms of each process, the dominant effects they produce, and the limitations of the existing approaches, as well as various numerical techniques implementing these models. It provides an overview of the ab initio-based modeling of the evolution of the electronic properties, Monte Carlo simulations of nonequilibrium electronic transport, molecular dynamics modeling of atomic reaction including phase transformations and damage on the surface and in the bulk, kinetic Mote Carlo of atomic defect kinetics, and finite-difference methods of track interaction with chemical solvents describing etching kinetics. We outline the modern methods that couple these approaches into multiscale and combined multidisciplinary models and point to their bottlenecks, strengths, and weaknesses. The analysis is accompanied by examples of important results, improving the understanding of track formation in various materials. Summarizing the most recent advances in the field of the track formation process, the review delivers a comprehensive picture and detailed understanding of the phenomenon. Important future directions of research and model development are also outlined.

To counteract oxidative stress, antioxidants including carotenoids are highly promising, yet their exploitation is drastically limited by the poor bioavailability and fast photodestruction, whereas current delivery systems are far from being efficient. Here we demonstrate that the recently discovered nanometer-sized water-soluble carotenoprotein from Anabaena sp. PCC 7120 (termed AnaCTDH) transiently interacts with liposomes to efficiently extract carotenoids via carotenoid-mediated homodimerization, yielding violet–purple protein samples. We characterize the spectroscopic properties of the obtained pigment–protein complexes and the thermodynamics of liposome–protein carotenoid transfer and demonstrate the delivery of carotenoid echinenone from AnaCTDH into liposomes with an efficiency of up to 70 ± 3%. Most importantly, we show efficient carotenoid delivery to membranes of mammalian cells, which provides protection from reactive oxygen species (ROS). Incubation of neuroblastoma cell line Tet21N in the presence of 1 μM AnaCTDH binding echinenone decreased antimycin A ROS production by 25% (p < 0.05). The described carotenoprotein may be considered as part of modular systems for the targeted antioxidant delivery.

To counteract oxidative stress, antioxidants including carotenoids are highly promising, yet their exploitation is drastically limited by the poor bioavailability and fast photodestruction, whereas current delivery systems are far from being efficient. Here we demonstrate that the recently discovered nanometer-sized water-soluble carotenoprotein from Anabaena (termed CTDH) transiently interacts with liposomes to efficiently extract carotenoids via carotenoid-mediated homodimerization, yielding violet-purple protein samples amenable to lyophilization and long-term storage. We characterize spectroscopic properties of the pigment-protein complexes and thermodynamics of liposome-protein carotenoid transfer and demonstrate the highly efficient delivery of echinenone form CTDH into liposomes. Most importantly, we show carotenoid delivery to membranes of mammalian cells, which provides protection from reactive oxygen species. The described carotenoprotein may be considered as part of modular systems for the targeted antioxidant delivery. Significance statement: Carotenoids are excellent natural antioxidants but their delivery to vulnerable cells is challenging due to their hydrophobic nature and susceptibility to degradation. Thus, systems securing antioxidant stability and facilitating targeted delivery are of great interest for the design of medical agents. In this work, we have demonstrated that soluble cyanobacterial carotenoprotein can deliver echinenone into membranes of liposomes and mammalian cells with almost 70 % efficiency, which alleviates the induced oxidative stress. Our findings warrant the robustness of the protein-based carotenoid delivery for studies of carotenoid activities and effects on cell models.

The results of atomic-level modeling of damage formation along the whole trajectory of swift heavy ions, stopping in the electronic energy loss mode in polyethylene are presented. Theoretical models could significantly improve the understanding of track formation in polymers, but their main disadvantage is an insufficient level of detail. In this paper, this problem is solved by using a multiscale hybrid approach: the Monte–Carlo TREKIS program describes the excitation of an electronic system of a target; the reactive molecular dynamics of the response of an atomic system to an ion-induced perturbation within the framework of the LAMMPS program allows to trace the damage up to the time of complete cooling of the track. Detailed tracing of the coupled electronic and atomic kinetics has shown that the damage maxima are spatially separated by at least 10 μm from the maxima of energy released by the ions. The differences occur due to the dependence of the initial spectra of electrons generated near the ion trajectory on the ion energy. The effects demonstrated should be the same for all polymers and may be critical for the effective operation of devices and detectors containing thin polymer films irradiated with swift heavy ions.