High pressure freezing is the most significant sample preparation method for morphological and immunocytochemical high resolution studies for electron microscopy.
High pressure freezing has made it possible to observe aqueous biological and industrial samples near to native state.
The 2100 bar of high pressure applied to the sample during high pressure freezing using the Leica EM HPM100 suppresses ice crystal formation and growth, while cryo-immobilization immediately after pressurization prevents structural damage to the sample.
High pressure frozen samples can be completely vitrified up to a thickness of 200 µm, a 10 to 40-fold increase in the depth of amorphous ice.
Once frozen, samples can be placed into the cryo chamber of an ultramicrotome for frozen hydrated sectioning. In combination with freeze substitution, high pressure freezing is an excellent alternative to chemical fixation for immunoelectron microscopy as the antigenicity and ultrastructure are both well preserved. The 6 mm carrier opens up new perspectives for correlative microscopy, as it allows a true pre-selection of a region of interest within large areas and the EM investigation of the same sample without the drawback of artefacts caused by chemical fixation.