Table 1.

Advantages and disadvantages of different types of fixation.

Fixatives	Advantages	Disadvantages
Glutaraldehyde (GA)	- Irreversible fixation of proteins. - Slow penetration through the cell wall. - Some preservation of antigenicity.	- Fixation artifacts: volume changes, denatured components lead to texture changes, transformation of protein gels into reticulated structures, spatial changes due to cross-linking of proteins. - Changes in molecular bonds, i.e. creation of new bonds between macromolecules can lead to reactive site misinterpretation during labeling.
Paraformaldehyde (PFA)	- Fast penetration through the cell wall. - Preserves antigenicity better than GA.	- Causes fixation artifacts: volume change, denatured components lead to texture changes, transformation of protein gels into a reticulated structures, spatial changes due to cross-linking of proteins.
Potassium permanganate	- Fixation by oxidation of proteins and lipids. - Fast penetration through the cell wall. - Provides membrane contrast.	- Loss of fine ultrastructure. - Loss of antigenicity.
Vitrification methods (HPF, plunge-freezing, propane jet, clamp)	- Instantaneous fixation at near native state. - Well-preserved morphology and antigenicity.	- Low of contrast. - Physical damage from ice crystal nucleation. - Often requires experience and training. - It can only be applied to process a small-size samples.
Osmium tetroxide	- Rapid and irreversible fixation of proteins and lipids. - Provides pronounced membrane contrast.	- Loss of antigenicity. - Transformation of membrane phospholipids into thick unbroken lines. - Highly toxic.