Silver proteinate (brand name: Protargol) is used in electron microscopy with periodic acid and thiocarbohydrazide or thiosemicarbohydrazide as a positive stain for carbohydrates such as glycogen. It can also be used for light microscopy to stain nerve tissue. It is normally available as 8% silver in combination with albumin.[1]
Staining ciliates with silver proteinate can reveal the infraciliature, an important character for identification of ciliates. Hundreds of ciliate species have been discovered using Protargol staining.[2]
Because of its bactericidal properties it was used to treat gonorrhea before the discovery of antibiotics. The inventor of the first silver protein formulation was Arthur Eichengrün, a German chemist working for Bayer. It was introduced for therapeutic use in 1897.[3] [4]