Cryogenic electron microscopy for native state analysis of nanoparticles in liquids

为特定应用而设计的纳米颗粒系统的成功取决于对界面化学的控制（例如胶体稳定性、总体尺寸等）。为了真正理解这一点，我们需要探索和理解纳米颗粒与它们所分布的环境之间的相互作用。该项目将重点发展表征分散在液体中的纳米颗粒的方法。电子显微镜是纳米颗粒分析的理想工具，具有研究纳米颗粒尺寸和结构所需的空间分辨率，以及相关的分析工具，能量色散x射线（EDX）和电子能量损失（EEL）光谱，可以提供单颗粒水平上的成分和键合信息。然而，限制是电子显微镜所需的真空水平，因此需要干燥的样品。该项目将利用生物样品制备方法，将分散在液体中的纳米颗粒冷冻，然后在低温下在电子显微镜下进行分析，分析能力用于探测不同纳米颗粒之间的相互作用，以及纳米颗粒与悬浮在其中的液体介质成分之间的相互作用。本项目将研究两种低温电子显微镜；（扫描）透射电子显微镜（(S)TEM）和聚焦离子束扫描电子显微镜（FIB-SEM），并建立了应用于冷冻样品的技术的局限性。对纳米颗粒的严格描述将使人们能够理解它们的影响和预测它们的行为。两个具有生物医学应用的纳米粒子系统将被用作模型系统；对于具有代表性的分析，这种表征必须在生物相关的液体介质中进行，并且在单个纳米颗粒的尺度上进行。该项目的结果将是了解悬浮在液体中的两种模型纳米粒子系统的结构和分散，并开发和评估这种纳米级分析方法，然后可以应用于进一步的重要系统。

The success of a nanoparticle system designed for a specific application is contingent on controlling the interfacial chemistry (e.g. colloidal stability, overall size, etc). To truly understand this, we require approaches to probe and understand the interactions between nanoparticles and the environments they are dispersed in.This project will focus on developing methods to characterise nanoparticles dispersed in liquids. Electron microscopy is ideally suited to the analysis of nanoparticles, with the required spatial resolution to investigate the size and structure of nanoparticles, and the associated analytical tools, energy dispersive X-ray (EDX) and electron energy loss (EEL) spectroscopies, which provide composition and bonding information at the single particle level. The limitation, however, is the vacuum level required in an electron microscope therefore necessitates dry samples. This project will utilise a biological sample preparation approach where nanoparticles dispersed in a liquid are frozen and then analysed in an electron microscope at cryogenic temperatures, with the analytical capabilities used to probe the interactions between different nanoparticles, and between the nanoparticles and components of the liquid media they are suspended in.Two types of cryogenic (cryo-) electron microscopy will be investigated in this project; (scanning) transmission electron microscopy ((S)TEM) and focused ion beam scanning electron microscopy (FIB-SEM), with the limits of the techniques applied to frozen samples established. Rigorous characterisation of nanoparticles will enable understanding of their impact and prediction of behaviour. Two nanoparticle systems with biomedical applications will be used as model systems; for representative analysis this characterisation must be conducted in biologically relevant liquid media, and at the scale of the individual nanoparticle. The outcome of the project will be understanding the structure and dispersion of two model nanoparticle system when suspended in liquids, and the development and assessment of this nanoscale analytical approach, which can then be applied to further systems of importance.