MRI: Acquisition of a High-Pressure Freezing System for Cryo-Electron Microscopy

技术（原）标题：核磁共振成像：获取高压冷冻电子显微镜的系统；标题：快速冷冻湿材料的高级电子显微镜非技术解释：使用显微镜来观察材料的结构提供了非常重要的信息，帮助科学家和工程师了解如何使新材料具有更好的性能。虽然许多显微镜使用光来形成图像，但电子显微镜可以达到更高的放大倍率，并解析材料结构中的更精细的细节。然而，与光学显微镜不同的是，电子显微镜需要真空（显微镜内的空气必须被除去），这样电子就不会与空气中的气体分子发生碰撞。在研究干燥材料时，真空不是问题，但在研究湿材料时，它是一个大问题，因为水在真空中很快蒸发。这个研究小组正在开发全含水的新材料。这些材料被设计用来帮助人体组织再生，使生物医学植入物更能抵抗感染，并在人体需要的地方和时间输送药物。如果这些新材料被冷冻并保持低温，就可以在电子显微镜下进行研究，因为这样水是固体而不是液体，而且不会蒸发。然而，冷冻必须以一种特殊的方式进行，否则材料就会损坏，就像密封的牛奶瓶冻结后会破裂一样。所以，这个研究项目使用了一种叫做高压冷冻机的新工具，它可以防止液态水在冻结时膨胀。因此，该团队能够研究湿材料，并在细节层面收集有关结构的信息，这是以前没有人做到的。由于这种方法是如此新颖和重要，研究小组正在与电子显微镜制造商合作，以帮助与其他显微镜用户分享这些进展。而且，由于这种冷冻工具也可以用来研究化妆品、食品、植物和昆虫等日常材料，研究团队正在与新泽西州的一所女子学校合作，利用这项新技术帮助数十名年轻女性接触到与科学和工程相关的一些兴奋。技术项目描述：虽然许多水合材料的平均形态通常可以通过散射（中子、x射线、光）来确定，但这些技术无法与电子显微镜收集特定地点、高分辨率、真实空间的图像数据的能力相匹配。然而，扫描（SEM）和透射电子显微镜（TEM）所需的高真空妨碍了对水化标本的直接观察，这种限制只能通过变压显微镜和环境/液体显微镜来部分缓解。长期以来的解决方案是冷冻标本，并在低温条件下在电子显微镜下研究它们。然而，简单地在液冷剂中淬火样品已不再足以解决该研究小组正在解决的成像问题。该团队正在进行六个外部资助的相互关联的项目，重点是聚合物和纳米颗粒自组装，微流体3-D组织模型，组织工程的先进支架，以及用于感染控制的分层表面纳米图案。这些项目都涉及高水化水平的先进材料，这阻碍了使用传统冷冻电镜技术进行高分辨率形态学研究。因此，该项目的目标是利用高压冷冻的新技术来制备高度水合的材料，用于先进的电子显微镜，包括扫描电镜和透射电镜，以及使用切片和视图聚焦离子束（FIB-SEM）显微镜进行三维成像。高压冷冻减轻了传统冷冻过程中由水结晶和溶质分离产生的人工产物。结合这项最先进的技术，使研究团队能够以开创性的图像分辨率水平评估新兴材料和材料系统在其天然水合状态下的详细形态。

Technical (Original) title: MRI: Acquisition of a High-Pressure Freezing System for Cryo-Electron MicroscopyLay Title: Rapid Freezing for Advanced Electron Microscopy of Wet Materials Nontechnical explanation: Using microscopes to see the structure of a material provides very important information that helps scientists and engineers understand how to make new materials with better properties. While many microscopes use light to form images, electron microscopes can reach much higher magnifications and resolve finer detail in a material's structure. However, unlike light microscopes, electron microscopes require a vacuum (the air inside the microscope must be removed )so that the electrons will not collide with gas molecules from the air. Vacuum isn't a problem when studying dry materials, but it is a big problem when studying wet materials, because water quickly evaporates in a vacuum. This research team is developing new materials that all contain water. These materials are being designed to help regrow human tissue, to make biomedical implants more resistant to infection, and to deliver drugs where and when they are needed within the human body. These new materials can be studied in an electron microscope if they are frozen and kept cold, because then the water is solid rather than liquid and it doesn't evaporate. However, the freezing has to be done in a special way, otherwise the material gets damaged just like a sealed bottle of milk will break if it freezes. So, this research project is using a new tool called a high-pressure freezer, which eliminates expansion of the liquid water when it freezes. Consequently, the team is able to study wet materials and gather information about structure at levels of detail that no one has previously achieved. Because this approach is so new and significant, the research team is working with an electron-microscope manufacturer to help share these developments with other microscope users. And, because this freezing tool can also be used to study everyday materials like cosmetics, food, plants, and insects, the research team is partnering with an all-girls school in New Jersey to use this new technology to help dozens of young women get exposed to some of the excitement associated with science and engineering. Technical Project Description: While the average morphology of many hydrated materials can often be determined by scattering (neutron, X-ray, light), these techniques can not match the ability of electron microscopes to collect site-specific, high-resolution, real-space, image data. The high vacuum required for both scanning (SEM) and transmission electron microscopy (TEM), however, precludes the direct observation of hydrated specimens, and this limitation is only partially mitigated by variable-pressure microscopes and environmental/liquid microscope stages. The long-standing solution has been to freeze the specimens and study them in the electron microscope under cryogenic conditions. Simply quenching specimens in a liquid cryogen is, however, no longer adequate for the imaging problems being addressed by this research team. This team is pursuing six externally funded inter-related projects centered on polymer and nanoparticle self-assembly, microfluidic 3-D tissue models, advanced scaffolds for tissue engineering, and hierarchical surface nano-patterning for infection control. These projects all involve advanced materials with high levels of hydration, which inhibits high-resolution morphological studies using conventional cryo-EM techniques. The goal of this project is thus to exploit the new technique of high-pressure freezing to prepare highly hydrated materials for advanced electron microscopy, both SEM and TEM, as well as for 3-D imaging using slice-and-view focused ion beam (FIB-SEM) microscopy. High-pressure freezing mitigates artifacts created by water crystallization and solute segregation during conventional freezing. Incorporating this state-of-the-art technology is enabling the research team to assess the detailed morphology of emerging materials and material systems in their native hydrated state at pioneering levels of image resolution.