I'm thinking about tincture of iodine, potassium iodide (Lugol's), and povidone-iodine (PVP-I) specifically, which, as is my understanding, work by solubilizing elemental iodine in an aqueous solution. These solutions slowly release free iodine, and it is ultimately the free iodine that does the biochemical damage that kills microorganisms.
But how, specifically, does free iodine cause this damage? The Wikipedia page on povidone-iodine says that free iodine:
kills eukaryotic or prokaryotic cells through iodination of lipids and oxidation of cytoplasmic and membrane compounds.
Slow release of iodine from the PVP-I complex in solution minimizes iodine toxicity towards mammalian cells.
I understand that elemental iodine strips electrons from all kinds of stuff because it is such a strong oxidizing agent, being so close to neutral valency, and obviously that's bad for important macromolecules, but I guess I'm looking for a bit more detail on how it works (or doesn't work) in other respects, with answers to questions such as:
- Why does iodination of lipids cause the lipid membrane to fail?
- Why does "slow release" make a difference for mammalian cells - are eukaryotic cells somehow better able to handle the damage caused by low concentrations of free iodine than prokaryotic cells?
- What makes bacterial spores and protozoan parasites such as Giardia resistant to iodine's antiseptic properties?
Sorry that that's more than one question. But if anyone is able to elaborate on any of these concepts, I'd greatly appreciate it!