Biological Consequences of Nanoscale Energy Deposition: Focusing on the Role of Low-Energy Electrons

• Applicants: Professor Dr. Frank Bier; Professor Dr. Heinz Sturm
• Subject Area: Medical Physics, Biomedical Technology
• Term: from 2014 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 245767821

There is great interest and progress to be made in understanding the reactions in irradiated aqueous systems. This concerns primarily radiotherapy, but also such diverse areas as remediation of nuclear wastes ornanoparticle synthesis. In the classical model of radiation chemistry radiolysis of water produces OH radical which subsequently damages the genome. Several recent developments fundamentally challenge this pictureand assign large part of lethal DNA lesions to reactions with low-energy electrons, which are abundant upon the impact of high-energy radiation. However, the experimental evidence here is predominantly based on "dry"DNA samples irradiated under vacuum conditions. We propose electron irradiation of DNA in aqueous solution through a SiO2 membrane. The DNA isimmobilized to only 40 nm thick membrane and its damage in water is analyzed by confocal fluorescence and real-time PCR methods. Our Monte Carlo simulations show that the spatial position of the radiation inducedionizing events in water can be positioned in the vicinity or at a desired distance from the immobilized DNA simply by varying the energy of electrons (1-5 keV) impacting onto the membrane. Both electrons and radicalsare generated by the radiolysis of water. However, the dynamics and reaction radius of the low-energy electrons and OH radicals are dramatically different. Thus, by changing the electron impact energy it is possible to tune into and out of the "electron damage" mode, and thus to obtain fundamental information on the primary chemical events following energy deposition. To corroborate these experiments we will also be looking for the sequence dependence of the damage which we have previously established with "dry" DNA samples for low-energy electrons. Since the method can be used universally with different types of radiations, it has the potential to provide for a better general understanding of the radiosensitivity of nano-scalebio-systems and to lead to development of new dose concepts.

• DFG Programme: Research Grants