Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Oho, Tsukuba, Ibaraki, Japan.
J Radiat Res. 2010;51(1):21-6. doi: 10.1269/jrr.09035.
When energetic carbon ion beam (GeV range) goes through the matter, inelastic processes such as electronic ionization, molecular and nuclear fragmentation occur. For carbontherapy (hadrontherapy) purpose, it is of interest to compare the number of DNA breaks -single SSB or double DSB- for a given dose at the entrance channel and at the Bragg peak to look for a possible differential effect in the number of DNA breaks induced at these two locations. Samples of free plasmids DNA and complexes of plasmids DNA added with molecules containing platinum have been placed at different locations of an experimental setup simulating penetration depths of the ion beam in water and irradiated by carbon ions 290 MeV/amu. The DNA breaks have been quantified by subsequent electrophoresis on agarose gels. To disentangle the respective role of the direct and indirect effect, a free radical scavenger of hydroxyl radicals HO degree-dimethylsulfoxide DMSO- has been added in some of the experiments. In the range of Linear Energy Transfer-LET 13 - 110 keV/microm-, the number of the DSB was found to be constant versus the LET for a given dose. Contrary, the number of the SSB decreases at the Bragg peak compared to the entrance channel. In the presence of platinum, the number of single and double breaks was considerably enhanced, and follows a similar behaviour than in the free-DNA experiments. Quantitative results on DNA damages do not show significant enhancement due to the nuclear or to the molecular fragmentation in the present experiments.
当高能碳离子束（GeV 范围）穿过物质时，会发生电子电离、分子和核碎裂等非弹性过程。对于碳治疗（粒子疗法）的目的，比较给定剂量在入口通道和布拉格峰处引起的 DNA 断裂数量（单链断裂或双链断裂）以寻找这两个位置诱导的 DNA 断裂数量的可能差异效应很有意义。已将游离质粒 DNA 样品和添加含有铂分子的质粒 DNA 复合物放置在模拟水中离子束穿透深度的实验装置的不同位置，并通过 290 MeV/amu 的碳离子进行辐照。通过随后在琼脂糖凝胶上进行电泳来定量 DNA 断裂。为了区分直接和间接效应的各自作用，在一些实验中添加了羟基自由基的自由基清除剂二甲基亚砜（DMSO）。在线性能量转移-LET 13-110 keV/μm 的范围内，对于给定剂量，DSB 的数量与 LET 成正比保持不变。相反，与入口通道相比，在布拉格峰处的 SSB 数量减少。在存在铂的情况下，单链和双链断裂的数量大大增加，并且与游离 DNA 实验的行为相似。由于本实验中的核或分子碎裂，定量的 DNA 损伤结果并未显示出明显的增强。
