Original Paper

Radiation and Environmental Biophysics

, Volume 42, Issue 4, pp 237-245

Microirradiation of cells with energetic heavy ions

  • A. HauptnerAffiliated withPhysics Department E12, Technische Universität München
  • , S. DietzelAffiliated withDepartment Biologie II, Ludwigs-Maximilians-Universität München
  • , G. A. DrexlerAffiliated withStrahlenbiologisches Institut, Ludwigs-Maximilians-Universität MünchenInstitut für Molekulare Strahlenbiologie, GSF-Forschungszentrum
  • , P. ReichartAffiliated withPhysics Department E12, Technische Universität München
  • , R. KrückenAffiliated withPhysics Department E12, Technische Universität München
  • , T. CremerAffiliated withDepartment Biologie II, Ludwigs-Maximilians-Universität München
  • , A. A. FriedlAffiliated withStrahlenbiologisches Institut, Ludwigs-Maximilians-Universität MünchenInstitut für Molekulare Strahlenbiologie, GSF-Forschungszentrum
  • , G. DollingerAffiliated withPhysics Department E12, Technische Universität München Email author 

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Abstract

The ion microprobe SNAKE at the Munich 14 MV tandem accelerator achieves beam focussing by a superconducting quadrupole doublet and can make use of a broad range of ions and ion energies, from 20 MeV protons to 200 MeV gold ions. Because of these properties, SNAKE is particularly attractive for biological microbeam experiments. Here we describe the adaptation of SNAKE for microirradiation of cell samples. This includes enlarging of the focal distance in order to adjust the focal plane to the specimen stage of a microscope, construction of a beam exit window in a flexible nozzle and of a suitable cell containment, as well as development of procedures for on-line focussing of the beam, preparation of single ions and scanning by electrostatic deflection of the beam. When irradiating with single 100 MeV 16O ions, the adapted set-up permits an irradiation accuracy of 0.91 µm (full width at half maximum) in the x-direction and 1.60 µm in the y-direction, as demonstrated by retrospective track etching of polycarbonate foils. Accumulation of the repair protein Rad51, as detected by immunofluorescence, was used as a biological track detector after irradiation of HeLa cells with geometric patterns of counted ions. Observed patterns of fluorescence foci agreed reasonably well with irradiation patterns, indicating successful adaptation of SNAKE. In spite of single ion irradiation, we frequently observed split fluorescence foci which might be explained by small-scale chromatin movements.