Preparation of Biological Samples
- Embedding in EPON resin: this technique is broadly applied in cell biological research and diagnostic pathology. The sample is fixed, dehydrated and stained with heavy metals (lead, uranium and osmium). After that, the sample is embedded in plastic resin to enable cutting into thin sections using a diamond knife in the ultramicrotome that then may be observed in a TEM.
- Negative Staining: can be used to obtain images of small particles in suspension such as viruses, protein complexes etc.
- Immuno-gold labeling: can be used to detect proteins in tissues or cells. Ultrathin sections can be decorated with gold particles that specifically pinpoint the localization of antibody and thus a protein of interest.
- High-pressure freezing: High pressure cooling is an alternative method which consists of flash-cooling biological crystals without the addition of cryoprotectant at around 200 MPa of (helium) pressure. At this pressure, the aqueous solvent is directly transformed into high density amorphous (HDA) ice, and the harmful consequences associated with water crystallization are avoided.
- Freeze substitution: in this technique, water frozen within cells is replaced by organic solvents at subzero temperatures.
- Freezing / Plunging for Cryo TEM: plunge freezing maintains the sample in the most native state.
- Cryogenic-Focused Ion Beam (cryo-FIB): Use accelerated ions to thin samples that would otherwise be too thick for cryo-TEM, This allows visualizing cellular ultra structures in near-native frozen hydrated states.
- Focused Ion Beam (FIB) "Slice and View" (S&V): Allows 3D imaging of entire cells, providing comprehensive structural insights.
- Preparation of biological samples for scanning electron microscopy (SEM): This allows visualizing surface images of biological specimens.
