General description

Osmium tetroxide (OsO4) also referred to as osmium, is a heavy tetrahedral, symmetrical molecule. It is both a dye and a non-coagulant fixative agent in electron microscopy primarily used for the examination of biological tissue components in the histopathology laboratory. Specimens are postfixed with osmium tetroxide to ensure the preservation of the lipids.

Application

Osmium tetroxide solution has been used as a fixative in electron microscopy.

Biochem/physiol Actions

Osmium tetroxide is also referred to as osmium and is mainly used as a secondary fixative of tissues. The molecule reacts with lipid moieties and is responsible for the oxidation of unsaturated bonds of fatty acids. This reaction adds density and contrast to biological samples. In normal tissues, presence of osmium results in intense black staining which can be viewed by normal eye. In addition, it can be used as a mordant (a molecule which combines with stain or dye at later stages) in electron microscopy, thereby enhancing lead staining.