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

技术（原）标题：MRI：获得用于低温电子显微镜的高压冷冻系统标题：用于湿材料的高级电子显微镜的快速冷冻非技术性解释：使用显微镜观察材料的结构提供了非常重要的信息，有助于科学家和工程师了解如何制造具有更好性能的新材料。 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数，并在材料结构中解析更精细的细节。 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去除），这样电子就不会与空气中的气体分子碰撞。 真空在研究干材料时不是问题，但在研究湿材料时却是一个大问题，因为水在真空中会迅速蒸发。 这个研究小组正在开发新的材料，都含有水。 这些材料被设计用于帮助人体组织再生，使生物医学植入物更能抵抗感染，并在人体内需要的地方和时间提供药物。这些新材料可以在电子显微镜下研究，如果它们被冷冻并保持低温，因为水是固体而不是液体，它不会蒸发。 然而，冷冻必须以一种特殊的方式进行，否则材料会被损坏，就像一瓶密封的牛奶在冷冻时会破裂一样。 因此，这个研究项目使用了一种叫做高压冷冻机的新工具，它可以消除液态水在冻结时的膨胀。 因此，该团队能够研究湿材料，并收集有关结构的信息，其详细程度是以前没有人达到的。 由于这种方法是如此新颖和重要，研究团队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发展。 而且，由于这种冷冻工具也可以用于研究化妆品，食品，植物和昆虫等日常材料，研究小组正在与新泽西的一所女子学校合作，使用这种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位置，高分辨率，真实空间图像数据的能力相匹配。 扫描（SEM）和透射电子显微镜（TEM）所需的高真空，但是，排除了直接观察的水合试样，这种限制只能部分减轻变压显微镜和环境/液体显微镜阶段。 长期以来的解决方案是冷冻样品，并在低温条件下在电子显微镜中研究它们。 然而，简单地在液体冷冻剂中淬火标本已经不足以解决这个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，微流体三维组织模型，先进的组织工程支架，以及用于感染控制的分层表面纳米图案化。 这些项目都涉及具有高水平水合作用的先进材料，这抑制了使用传统冷冻EM技术的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用于先进电子显微镜（SEM和TEM）以及使用切片和视图聚焦离子束（FIB-SEM）显微镜的3-D成像的高度水合材料。 高压冷冻减轻了在常规冷冻期间由水结晶和溶质分离产生的伪影。 这种最先进的技术使研究团队能够以开创性的图像分辨率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.