Abstract
This chapter addresses the nanoscale dynamics involved in the sensitization of biological cells to ionizing radiation. More specifically, it describes the role of low energy electrons (LEE) in radiosensitization by gold nanoparticles and chemotherapeutic agents, as well as potential applications to radiotherapy. The basic mechanisms of action of the LEE generated within nanoscopic volumes by ionizing radiation are described in solid water ice and various forms of DNA. These latter include the subunits (i.e., a base, a sugar or the phosphate group), short single strands (i.e., oligonucleotides) and plasmid and linear DNA. By comparing the results from experiments with the different forms of the DNA molecule and theory, it is possible to determine fundamental mechanisms that are involved in the dissociation of the subunits, base release and the production of single, double-strand breaks and cross-links. Below 15 eV, LEE localize on DNA subunits to form transient negative ions. Such states can damage DNA by dissociating into a stable anion and radical fragment(s), via dissociative electron attachment, or by decaying into dissociative electronically excited states. LEE can also transfer from one DNA subunit to another, particularly from a base to the phosphate group, where they can induce cleavage of the C-O bond (i.e., break a strand). DNA damage and the corresponding nanoscale dynamics are found to be modified in the presence of other cellular constituents. For example, condensing on DNA the most abundant cellular molecule, H2O, induces the formation of a new type of transient anion whose parent is a H2O-DNA complex.
Published Version
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