Electron Microscopy

The Electron Microscopy Service offers access to transmission electron microscopy (TEM), Cryo-TEM and Electron Tomography, high resolution scanning electron microscopy (SEM) and environmental SEM. A special emphasis has been made on high-end sample preparation techniques through cryo-inmobilization. All the equipments have been configured to provide its best on biological and nanomedicine applications.

TEM, SEM and sample preparation facilities and services are offered to provide structural characterizations at the micro and nano scales. Biological and medical applications are the main objective of these equipments but are not limited to them. Any other scientific and engineering field can take advantage of them due to its versatility for public and private research, quality control, failure analysis, etc.

Transmission Electron Microscopy (TEM)

    Conventional TEM provides structural information of samples prepared until electron transparency in the sub-nanometer range. Bacteria, virus, yeasts, cells, tissues are among the samples that, after a proper sample preparation, can be characterized using TEM. Moreover, this is a very versatile technique that allows the characterization of samples from many other scientific areas.

  • FEI Tecnai G2 20 TWIN Transmission Electron Microscope

Cryo-TEM

    Cryo-TEM is the technique of choice for the visualization of biological suspensions and any other sub-micron particles in solution. Cryo-immobilization is performed through plunge freezing and samples are transferred to the cryo-holder and to the microscope at temperatures close to liquid nitrogen. Visualization with Low Dose mode allows minimizing beam damage on the sample and re-crystallization risk.

  • Cryo-TEM on FEI Tecnai G2 20 TWIN Transmission Electron Microscope

Electron Tomography (ET)

    ET is nowadays the technique that provides a higher resolution for 3D structural characterization in both life sciences and materials science (1,2). A set of 2D images at different tilting angles (typically from -70° to +70°) is acquired and used for volume reconstruction. The standard workflow consists of: tilt series acquisition at/on/in the TEM and post-processing at a workstation including tilt series alignment, volume reconstruction and volume visualization.

  • Electron Tomography Package
  • [1]J. Frank, Three-Dimensional Electron Microscopy of Macromolecular Assemblies, Oxford University Press, USA, 2006).

    [2] P.A. Midgley, and R. E. Dunin-Borkowski, Nature Materials 8 (2009) 271.

Scanning Electron Microscopy (SEM)

    SEM comprises a set of techniques related to the interaction of an electron beam that raster the surface of the sample with it. Secondary electron, backscattered electrons, X rays, Auger electrons among others are generated and provides information about surface topopgraphy, composition and other properties of the sample characterized. A Field Emission Gun (FEG) source will allow resolutions below 2 nm.

  • FEI Quanta 250 FEG Scanning Electron Microscope

Environmental SEM (ESEM)

    Environmental SEM allows the observation of samples in a vacuum-free atmosphere. Water vapor is insufflated inside the chamber during the pumping process (trough purge cycles) what will allow to work at chamber pressures as high as 2600 Pa. The combination of this mode with a peltier stage allow us to work at 100% humidity in the chamber what will facilitate the visualization of fully hydrated samples and perform dynamic experiments through pressure changes, including hydration - dehydration sequences.

  • ESEM mode in FEI Quanta 250 FEG

Applications

    Applications in medicine and biology of electron microscopy can be divided in 4 areas:


    Cellular characterization: cell structures and ultrastructures visualization and its relationship to function are the most important contributions of EM to cell biology. This includes not only standard visualization of embedded and stained sections but also localization of proteins inside cells trough immunolabelling with a resolution around 10 nm. For this high resolution analysis a sample preparation that do not disturb ultrastructure is mandatory been high pressure freezing the cryo-immobilization technique preferred for this kind of characterizations. Moreover, electron tomography is uniquely suited to obtained 3D reconstructions of cells and its internal structures and thus, to improved the information provided by standard 2D analysis.

  • http://www.uni-mainz.de/FB/Medizin/Anatomie/workshop/EM/EMAtlas.html

  • "Electron tomography reveals unbranched networks of actin filaments in lamellipodia", Edit Urban1,3, Sonja Jacob1,3, Maria Nemethova1, Guenter P. Resch1,2 & J. Victor Small, Nature Cell Biology 12, 429 - 435 (2010)

    "VIS2FIX: A High-Speed Fixation Method for Immuno-Electron Microscopy" Matthia A. Karreman, Elly G. van Donselaar, Hans C. Gerritsen, C. Theo Verrips and Arie J. Verkleij, Traffic 2011; 12: 806–814


    Tissues characterization: electron microscopy has a role in the characterization of interactions between cells and with other components inside tissues. Moreover, high resolution superficial characterizations of bones, teeth, skin, etc, are made by SEM.

    Other biological systems: leafs, flowers, insects, microorganisms are among the structures that can be topographically characterized using SEM. For these systems as for others with a high hydration state, ESEM has become an important tool due to its ability for surfaces visualization even in a 100% humidity environment, reducing sample preparation and permitting dynamical analysis through hydration-dehydration cycles. Dynamics experiments are useful in food industry, water-oil emulsions characterization, pharmaceutical quality control,…

    Biomaterials characterization: electron microscopy plays a double role on biomaterials characterization. On one hand provides structural and compositional information of the materials engineered to be used inside biological systems, favoring its development. On the other hand, allow us to visualize their interactions. Functionalized polymeric and metallic nanoparticles for drugs delivery, dental implants, bone plates and cements, artificial tissues are among the biomaterials that can benefit from information provided by EM.

    Macromolecular complexes characterization: structural biology can benefit from electron microscopy to determine 3D structures of macromolecular complexes. Negative staining was issued in the past but has been the development of cryo-electron microscopy in combination with Single Particle analysis what has made EM a very valuable tool for 3D determinations.