Photopolymerized 2-hydroxyethylmethacrylate as a mounting medium preserving immunocytochemical reaction and nuclear counterstain.

Immunocytochemical or cytoenzymological techniques often make use of coupling reactions between a substituted naphtol and a diazonium salt. A positive reaction results in an azo dye precipitate. Unfortunately, this precipitate is easily soluble in alcohols and organic solvents. Thus, usual mounting media are not usable and permanent preparations cannot be obtained. A stable mounting medium such as Apathy's syrup can be used, but nuclear counterstaining disappears in a few days. We tested the hydrophilic monomer 2-hydroxyethylmethacrylate, containing various photopolymerizing agents, as a permanent mounting medium. 2-2 Dimethoxy 2-phenyl acetophenone proved to be the most useful photopolymerizer. The cytocentrifugation slides must be dried before mounting to avoid recrystallization artifacts. The azo dye precipitate and nuclear counterstaining can be preserved perfectly long-term. The cost of these media is very low.