An experimental platform for studying the radiation effects of laser accelerated protons on mammalian cells

An experimental platform was designed to study the effects of laser accelerated protons (LAPs) on mammalian cells. The protons, in the MeV energy range, originate from the rear side of a thin 5 µm Ti foil target following the interaction with a high power laser pulse and are accelerated by the target normal sheath mechanism. A tape Ti foil target was developed, allowing a shot repetition rate of up to 5 Hz, which corresponds to the rate of the laser system. A dipole magnet arrangement was used for energy dispersion and to separate the proton burst from electrons and x rays. The absorbed radiation dose at the cell port was measured with CR39 plastic detectors and calibrated imaging plates. An epifluorescence microscope with compact open-beam optics was developed to image live cells and their spatiotemporal properties during and after irradiation. To demonstrate the functionality of all components of the platform, biological proof of concept experiments were carried out using two suspension (Jurkat and Ramos) and two adherent (HeLa and A-549) cell lines. A multitude of biological procedures and analytical techniques were established on-site or in laboratories nearby. For example, we analyzed DNA double-strand break (DSB) induction and repair by detecting the γH2A.X signal by fluorescence microscopy and flow cytometry. The observed dose-dependent increase in DSB induction confirms that DNA damage is induced in cells after exposure to LAPs.