Spoiler alert – we think its copper!
While many people are aware of Silver as an antimicrobial, fewer people seem to be aware that both copper and gold are as well! All three are elemental metals that share something called “the Oligodynamic” effect, which is the biocidal effect of metals. These metals release ions which covalently bond to proteins and disrupts the ability of cells to function or replicate.
In addition to the Oligodynamic effect, Copper has another mechanism of action against microbes. In certain forms, including the one that Cupron uses in its active additives, it releases an electron (creating a reactive oxygen species) which can be highly destructive to viruses, fungi, and bacteria. You can read more about how copper kills here.
Furthermore, Copper is the only metal with antimicrobial properties that is also an essential micronutrient for humans (and all other living things). It is essential for things like cell respiration, neurotransmitter synthesis, and the cross linking of collagen and elastin in the skin. This means that while in high concentrations it can be toxic, it is generally less problematic in the environment than other metals. The toxicity of Silver is 65X that of copper according to the EPA.
Lastly, and perhaps most importantly, copper is more effective under a broader set of conditions and is even enhanced by conditions that reduce the efficacy of silver. While silver performs well under hot and humid conditions, its efficacy drops along with the ambient temperature. Copper on the other hand maintains its efficacy across a range of temperature and humidities.
Here’s a table summarizing the key differences, with references.
| Feature | Copper | Silver | |
| 1 | EPA Public Health Claims | Multiple[i] | None |
| 2 | Efficacy | Broad spectrum (Bacteria, Viruses & Fungi & Fungal Spores) | Less effective against Viruses; Fungi & Fungal spores[ii] |
| 3 | Mode of action | Metal ion | Metal ion[iii] |
| Reactive Oxygen Species | |||
| 4 | Role in Human body | Essential micronutrient | None |
| Improves skin elasticity | |||
| Enhances wound healing[iv] | |||
| 5 | Durability | High, due to low solubility | Depends on type of treatment but not as durable |
| 6 | Sweaty Environment | Enhances efficacy[v] | Diminishes efficacy |
| 7 | Temperature | Maintains Efficacy | Low temperature reduces efficacy |
| 8 | Humid Environment | Maintains Efficacy[vi] | Low humidity reduces efficacy |
[i] http://npirspublic.ceris.purdue.edu/ppis/
[ii] https://pubmed.ncbi.nlm.nih.gov/27015373/
[iii] https://www.nature.com/articles/nrmicro3028
[iv] https://www.ncbi.nlm.nih.gov/books/NBK225407/
[v] https://www.nature.com/articles/s41598-019-56009-6
[vi] https://pubmed.ncbi.nlm.nih.gov/19413757/
