Preliminary Exploration Of Several Testing Techniques On DNA And Cell Damage Induced By Radiations

Proton and heavy ions have been applied in cancer radiation therapy field, and people have accepted this method increasingly. Under this background, the research on the biological effects and mechanisms of mammalian cell irradiated by high linear energy transfer (LET) ions has become more and more important.This research investigate the biological effects of plasmid DNA and several cells after irradiation by methods of agarose gel electrophoresis along with advanced gel imaging system, colony forming ability experiment along with other traditional cell biology techniques and gene chip as a modern molecular biotechnology. The experimental results of this research can be expected to offer valuable basic data for cancer therapy by heavy ions and protons radiation method, Boron Neutron Capture Therapy (BNCT) as well as the dangerous assessment and protection of human in space or nuclear radiation environment, etc. The experimental procedure and elementary results are as follows:The pUC19 plasmid DNA with or without free radical scavengers in aqueous solution is irradiated by 60Co-γrays, the results are analyzed by gel electrophoresis and Alpha Innotech digital imaging system .The results indicate that free radicals produced byγrays radiation are an important factor for the induction of DNA single strand breaks (SSB) and DNA double strand breaks (DSB). Mannitol, Vitamin C and tea polyphenols are all good scavengers, and mannitol is more effective than Vitamin C under the same condition. Compared with heavy ions, the capacity of scavengers is more remarkable on free radicals induced byγrays, which is more important to evaluate the effect of free radicals in heavy ion radiation.U251 glioma cell and HepG2 liver cancer cell are irradiated by 60Co-γrays andαparticles emitted from 238Puαsource respectively. The results indicate that U251 cell is more sensitive to ionizing radiation than HepG2 cell, andαparticles irradiation inhibit the cell proliferation more effectively thanγrays irradiation. It means thatαparticles have a higher relative biological effectiveness (RBE) thanγrays.L02 normal liver cell is irradiated by 5Gy 80MeV/u 12C6+ ions in radiation terminal of Heavy Ion Research Facility at Lanzhou (HIRFL). 22k human genome oligonucleotide microarray was used to explore the transcriptional profiles of the cells at 6h and 24h post-irradiation. In the 6h post-irradiation cells, the microarrays displayed 37 differentially expressed genes, including 18 up-regulated genes and 19 down-regulated genes. In the 24h post-irradiation cells, the microarrays displayed 269 differentially expressed genes, including 67 up-regulated gene and 202 down-regulated genes. Most of these changed genes were associated with signal transduction,cell cycle control,DNA repair and apoptosis. These observations provided the information of radiation-induced genes for elucidating molecular mechanisms of the diverse biological effects generated by heavy ion irradiation.During the experiment mentioned above, several testing techniques on DNA and cell damage have been learnt and the adaptability,advantages and disadvantages of these methods are evaluated.