Fundamental Studies of the Effects of Auger Electrons Emitted in Different Subcellular Compartments of Human Cells

人类细胞不同亚细胞区室发射的俄歇电子效应的基础研究

• 批准号: RGPIN-2020-04496
• 负责人: Reilly, Raymond
• 金额: $ 3.64万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=739994
• 关键词: Fundamental; Studies; Effects; Auger; Electrons

Auger electrons (AEs) are very low energy electrons (<25 keV) emitted by radionuclides (e.g. 99mTc, 111In, 67Ga) that decay by electron capture (EC). These radionuclides are used in nuclear medicine for SPECT since they also emit ?-photons. In addition, AEs are being studied for precise irradiation of cancerous cells because they have a subcellular range (nm to µm) and high linear energy transfer (LET=1-23 keV/µm) that inflicts lethal damage on sensitive cell compartments. It was assumed that AE emission in close proximity to the nucleus was required to kill cells, by inflicting DNA double-strand breaks (DSBs), but it was recently reported that AEs also kill cells by causing oxidative damage to the cell membrane. This raises the intriguing question about whether or not there are other targets for AE damage. This is an unexplored area. We propose a program of research to study the effects of AEs emitted at the cell membrane, in the cytoplasm, mitochondria, nuclear envelope or nucleus of cancerous and normal cells. These fundamental studies have important health physics implications for AE-emitting radionuclides used in nuclear medicine, and will also inform on the design of AE-emitting radiotherapeutic agents in the future. We will engineer novel "nano-shuttle" delivery vehicles to route 111In, 67Ga or 99mTc to the selected subcellular compartments. The nano-shuttles will consist of gold nanoparticles (AuNPs) modified with peptides that target cell surface avß3 integrins, and with homing peptides that route the internalized AuNPs to subcellular compartments. The AuNPs will be fluorescently-labeled to visualize their subcellular distribution and will be labeled with polymers that complex 111In, 67Ga or 99mTc. The amount of radioactivity deposited in subcellular compartments will be measured by cell fractionation and used to estimate the absorbed doses. Doses will be calculated by Monte Carlo N-Particle (MCNP6) modeling, and then correlated with the radiobiological effects of AE emission in the subcellular compartments. The radiobiological effects of AE emission will be studied by determining the clonogenic survival of the cells. The mechanism of cell death will be examined by probing the cells for cell membrane damage, disruption of mitochondrial membrane potential, micronucleus formation due to nuclear envelope damage and DNA DSBs by immunofluorescence for ?-H2AX. Our long-term aim is to develop the tools for studying the effects of short-range radiations in cells, and to understand the radiobiological and dosimetric properties of radiations in human cells. The proposed research program will provide an outstanding trans-disciplinary HQP training environment for 3 new graduate students (two PhD and one MSc) with different expertise who will work collaboratively as a team to develop and characterize the nano-shuttles, study the radiobiological effects of AEs emitted in the different subcellular compartments, and model the cellular dosimetry.

俄歇电子（AE）是由放射性核素（例如99 mTc、111 In、67 Ga）发射的通过电子捕获（EC）衰变的非常低能量的电子（<25 keV）。这些放射性核素在核医学中用于SPECT，因为它们也发射？光子此外，正在研究AE对癌细胞的精确照射，因为它们具有亚细胞范围（nm至µm）和高线性能量转移（LET=1-23 keV/µm），可对敏感细胞区室造成致命损伤。据推测，需要在细胞核附近发射AE，通过造成DNA双链断裂（DSB）来杀死细胞，但最近报道AE也通过对细胞膜造成氧化损伤来杀死细胞。这就提出了一个有趣的问题，即是否存在AE损伤的其他目标。这是一个未开发的领域。我们提出了一个研究计划，以研究在癌细胞和正常细胞的细胞膜，细胞质，线粒体，核膜或细胞核中发射的AE的影响。这些基础研究对核医学中使用的AE发射放射性核素具有重要的健康物理意义，并且还将为将来AE发射放射性物质的设计提供信息。我们将设计新型的“纳米穿梭”运载工具，将111 In，67 Ga或99 mTc运送到选定的亚细胞区室。纳米梭将由用靶向细胞表面α v β 3整联蛋白的肽和用将内化的AuNP路由到亚细胞区室的归巢肽修饰的金纳米颗粒（AuNP）组成。AuNP将被荧光标记以可视化它们的亚细胞分布，并且将用络合111 In、67 Ga或99 mTc的聚合物标记。将通过细胞分级法测量沉积在亚细胞区室中的放射性量，并用于估计吸收剂量。将通过蒙特卡罗N粒子（MCNP 6）建模计算剂量，然后将其与亚细胞区室中AE发射的放射生物学效应相关联。AE发射的放射生物学效应将通过测定细胞的克隆存活率进行研究。通过检测细胞膜损伤、线粒体膜电位破坏、核膜损伤引起的微核形成以及通过免疫荧光检测？- H2AX。我们的长期目标是开发研究短程辐射对细胞影响的工具，并了解辐射对人体细胞的放射生物学和剂量学特性。拟议的研究计划将提供一个优秀的跨学科的HQP培训环境，为3个新的研究生（两个博士和一个硕士）具有不同的专业知识，谁将作为一个团队合作开发和表征的纳米航天飞机，研究在不同的亚细胞室发射的AE的放射生物学效应，并模拟细胞剂量学。