Metallothioneins and Silver
Silver has no known natural biological role and has a range of toxicity depending on the form of the metal and the organism involved (Wiley and Brooks 1992). Colloidal silver, which is toxic to microbes, has been used over many centuries as an antiseptic and disinfectant in wound dressings (Klasen 2000a, b). Even though elemental silver is not particularly toxic to humans, silver ions are highly toxic and are thought to be carcinogenic. No studies were found to report cancer in humans after exposure to silver or silver compounds, although subcutaneous imbedding of silver foil induced fibrosarcomas in rats (Oppenheimer et al. 1956).
Metallothioneins (MTs) bind metals in the monovalent group 11 triad (copper, silver, and gold) and in the divalent group 12 triad (zinc, cadmium, and mercury) both in vitro and in vivo (Schmitz et al. 1980; Sutherland and Stillman 2011). One of the proposed roles for MT is in toxic metal detoxification