A new system for laser-UVA-microirradiation of living cells.

Local nuclear irradiation of living cells has been used to gain insight into the dynamic changes that cell nuclei undergo in response to DNA damage. In particular, the effects of DNA double-strand breaks (DSBs), a major threat to the genomic integrity of cells, have been studied by local nuclear irradiation with ionizing radiation. This method has the disadvantage that it requires expensive equipment to generate a sufficiently high density of focused or collimated ionizing radiation. After appropriate sensitization of the cellular DNA, nuclear microirradiation with UVA can also produce DSBs. In this communication we present a semi-automatic system for laser-UVA-microirradiation based on a commercial laser scanning microscope. The system allows the convenient selection and precise irradiation of living cells, and could provide the basis for a more widespread availability of microirradiation facilities for DNA-repair research.