Silver stains

Silver staining is the use of silver to selectively alter the appearance of a target in microscopy of histological sections; in temperature gradient gel electrophoresis; and in polyacrylamide gels.

Camillo Golgi perfected silver staining for the study of the nervous system. Although the exact chemical mechanism by which this occurs is unknown,Golgi's method stains a limited number of cells at random in their entirety.

Silver staining was introduced by Kerenyi and Gallyas as a sensitive procedure to detect trace amounts of proteins in gels. The technique has been extended to the study of other biological macromolecules that have been separated in a variety of supports.

Classical Coomassie Brilliant Blue staining can usually detect a 50 ng protein band; silver staining increases the sensitivity typically 50 times.

Many variables can influence the colour intensity and every protein has its own staining characteristics; clean glassware, pure reagents and water of highest purity are the key points to successful staining.

Some cells are argentaffin. These reduce silver solution to metallic silver after formalin fixation. Other cells are argyrophilic. These reduce silver solution to metallic silver after being exposed to the stain that contains a reductant, for example hydroquinone or formalin.

Silver nitrate forms insoluble silver phosphate with phosphate ions; this method is known as the Von Kossa Stain. When subjected to a reducing agent, usually hydroquinone, it forms black elementary silver. This is used for study of formation of calcium phosphate particles during bone growth.

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