Mapping Anti-Cancer Drugs using Advanced X-ray Microanalysis

虽然微量热计在生物学上的应用似乎与天文学和天体物理学相去甚远，但它在与环境扫描电子显微镜一起工作时，其同时解析广泛能量范围内的X射线发射线的前所未有的能力已经提供了诱人的线索，表明亚细胞维度的化学信息异常丰富。 到目前为止，我们已经对几个有代表性的生物样本进行了原则证明测量。在0.2keV到10keV的能量范围内，微量热计的光谱分辨率(2.5-6 eV)和相应的信本底比比当代EDS(Si(Li)或Ge)探测器至少提高了60倍。它在低X射线能量下的卓越性能可以使ESEM在低电子能量和较低的电子束电流下运行，从而将沉积在非常小体积的功率降至最低，同时提高X射线图像分辨率和细胞诊断能力。在这种束流条件下，低密度生物样品产生的X射线与高密度固体靶的发射强度相比相对较小。通过采用定制的X射线光学系统来显著增加X射线的收集，我们打算弥补较低的X射线产量。 我们的计划是使用这种新的微量分析工具来全面研究一系列生物样本。反过来，准确、相对的元素丰度测量可能成为常规方法，它们与离子传输、细胞增殖和细胞凋亡的相关性可能导致对细胞行为的强大诊断。在特定细胞位置发现的微量元素生物标记物可能被证明是疾病的可靠哨兵。顺铂等以重元素为基础的化疗药物的X射线光谱图像有助于更好地了解抗癌药物的作用。高光谱分辨率可能使从一组更具生物相关性的元素中选择蛋白质标记成为可能，而不是从高对比度电子显微镜所需的重元素中选择。这将大大简化样品准备，保持细胞完整性，并将图像中的伪影降至最低。我们期待着拥有令人难以置信的丰富的关于细胞行为的新信息，以及它对早期癌症检测的诊断潜力的迹象。

DESCRIPTION (provided by applicant): We have developed a prototype x-ray microanalysis system with unprecedented spatial and spectroscopic resolution. It combines two state-of-the art instruments. One is a cryogenic x-ray microcalorimeter that we built several years ago for x-ray astronomy missions under NASA auspices. The second is a high resolution, environmental scanning electron microscope (ESEM) developed by the FEI Company. Although the microcalorimeter's application to biology may seem far afield from astronomy and astrophysics, its unprecedented power to simultaneously resolve x-ray emission lines over a broad range of energies has already provided tantalizing hints of unusually rich chemical information at sub-cellular dimensions when operating in conjunction with the ESEM. To date, we have conducted proof-of-principle measurements on a few representative biological samples. The increased spectral resolution (2.5 - 6 eV) and consequent signal-to back ground ratio of the microcalorimeter over the energy range of 0.2 keV to 10 keV is at least a 60-fold improvement over present generation EDS (Si(Li) or germanium) detectors. Its superior performance at low x-ray energies could enable ESEM operation at low electron energies and lower electron beam current, thereby minimizing the power deposited into very small volumes while enhancing x-ray image resolution and cellular diagnostics. Under these beam conditions, the x-ray production from low density biological samples is relatively small compared to the emission intensity from dense solid targets. By employing a custom-made, x-ray optic to significantly increase x-ray collection, we intend to compensate for lower x-ray production. Our plan is to use this new microanalytical tool to comprehensively study a range of biological samples. In turn, accurate, relative elemental abundance measurements could become routine and their correlation with ion transport, cell proliferation, and apoptosis could lead to powerful diagnostics of cellular behavior. Trace element biomarkers found at specific cellular locations may prove to be reliable sentinels of disease. Spectroscopic x-ray images of heavy element-based chemotherapy drugs such as cisplatin promise better understanding of the actions of anti-cancer drugs. High spectral resolution may make it possible to choose protein markers from a more biologically relevant set of elements, rather than from the heavy-elements needed to date for high contrast electron microscopy. This would greatly simplify sample preparation, maintain cell integrity and minimize artifacts in the image. We expect to have an incredible wealth of new information about cellular behavior and indications of its diagnostic potential for early cancer detection.