Question.

Commercially available fixatives are touted variously as "non-crosslinking," "less-crosslinking," "formaldehyde-free," "better for immunohistochemistry," "less toxic," ,etc., etc.

Is there a recent review, or can someone share a list of names of commercially available fixatives (supposedly better for immunohistochemistry) and their vendors?

Answer.

Here are all of the ones that I know about; some of them may be sold under different names by other vendors:

GlyoFix from Shandon Lipshaw uses glyoxal as the active ingredient; produces aldehyde-type fixation patterns.

Histochoice from Amresco; active ingredients essentially undisclosed (aldehydic addition compounds); mode of action unknown.

HistoFix, formerly from Trend Scientific, perhaps still available from Baxter, contains pyrrolid-2-one, a polyol, a urea and a zinc salt; mode of action unknown.

Mirsky's Fixative from National Diagnostics is an aqueous solution of a complex di-aldehyde (possible di-aldehyde starch); mode of action may be aldehyde-like, but very slow.

NoToX from EarthSafe Industries, uses a complex aldehyde (possibly di-aldehyde glucose) in about 70% alcohol with antiseptic and antifungal agents; produces a combination of aldehyde- and alcohol-type fixation patterns.

OmniFix II and OmniFix 2000 from AnCon Genetics is an alcohol-based solution containing glycol and salts; produces alcohol-type fixation patterns.

Prefer from Anatech Ltd., uses glyoxal as the active ingredient; produces aldehyde-type fixation patterns.

SafeFix II from CMS uses glyoxal as the active ingredient; produces aldehyde-type fixation patterns.

STF (Streck Tissue Fixative) from Streck Laboratories contains diazolidinyl urea, 2-bromo-2-nitropropane-1,3 diol, zinc sulfate and a small amount of formaldehyde as active ingredients; mode of action unknown.

There are two fixatives intended for microwave use:

Preserve from Energy Beam Sciences uses glyoxal as the active ingredient; produces aldehyde-type fixation patterns.

MicroFix from Energy Beam Sciences is an alcohol/polyethylene glycol solution. It replaces Merck's KryoFix, which is no longer available; produces alcohol-type fixation patterns.

A rather uncomplimentary comparison of some of these products (Histochoice, KryoFix, Mirsky, NoToX, Omnifix II and STF) has been published (Prento & Lyon, 1997. Commercial formalin substitutes for histopathology.  Biotechnic & Histochemistry, 72:273-282).  Readers should note that none of them were used as directed or intended by the manufacturers (fixation at 4 degrees C), so the results are questionable.  Also, none of the glyoxal-based fixatives (GlyoFix, Prefer, SafeFix II, Preserve) were tested; these seem to be the most favored substitutes in the USA at least, because they most nearly mimic the morphological patterns obtained with formalin without formaldehyde's unfavorable effects on immunoreactivity.

Richard W. Dapson, Ph.D.
Anatech Ltd.
Battle Creek, MI  49015