Oligodynamic effect

The oligodynamic effect (Greek oligos = few, dynamis = force) was discovered in 1893 by the Swiss KW Nägeli as a toxic effect of metal-ions on living cells, algae, moulds, spores, fungi, virus, prokaryotic and eukaryotic microorganisms, even in relatively low concentrations. This antimicrobial effect is shown by ions of: mercury, silver, copper, iron, lead, zinc, bismuth, gold, aluminium and other metals.

Especially heavy metals show this effect. The exact mechanism of action is still unknown. Data from silver suggest that these ions denature proteins (enzymes) of the target cell or organism by binding to reactive groups resulting in their precipitation and inactivation. Silver inactivates enzymes by reacting with the sulfhydryl groups to form silver sulfides. Silver also reacts with the amino-, carboxyl-, phosphate-, and imidazole-groups and diminish the activities of lactate dehydrogenase and glutathione peroxidase. Bacteria (gram+ and gram-) are in general affected by the oligodynamic effect, but they can develop a heavy-metal resistance, or in the case of silver a silver-resistance. Viruses in general are not very sensitive. The toxic effect is fully developed often only after a long time (many hours).

Applications of the oligodynamic effect
Certain metals, e.g. brass and copper are known to be far more poisonous to bacteria than others, such as stainless steel or aluminum which is why they're now used in mineral sanitizers for swimming pools and spas.

Many infections can spread by doorknobs. Brass doorknobs disinfect themselves in about eight hours, while stainless steel and aluminum knobs never do. Brass doorknobs therefore tend to be more sanitary than stainless or aluminum doorknobs. The effect is important in hospitals, and useful in any building.

Silver is capable of rendering stored drinking water potable for a long period of time (several months). For this reason, water tanks on ships and airplanes are often "silvered".

Silver or silver compounds are used externally in wound and burn treatments.