Formalin substitutes have been developed to fix tissue while avoiding the antigen masking effects of formalin. They can be aqueous-based and/or alcohol-based preparations. Due to the nature of these water or alcohol-based substitutes, penetration of the specimen is slower than when formalin is used. Thus, fixation times need to be increased, and tissue samples must be trimmed as small as possible to adequately fix the tissue. Some advantages to using these substitutes are that little, or no antigen retrieval is necessary, they are less toxic (but still toxic), and they come pre-mixed and ready to use.
Caution must be used when using a formalin substitute. The additives in the fixative may contribute to false-positive or false-negative IHC staining results. Again, it is important to check the product insert sheet for the antibody you are using for recommended fixatives.
