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.

and that:

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!

  • $\begingroup$ Welcome to Biology.SE! This seems like an interesting series of questions, but please take the tour and then go through the help pages starting with How to Ask questions effectively on this site and edit your question accordingly. ——— In particular, please separate your questions — each post should be focused on one question. This helps you get answers to all of your questions and makes those answers more accessible to searching by other users. (You can provide links to the related questions in your text.) Thanks! 😊 $\endgroup$ – tyersome Jan 13 '20 at 20:13
  • $\begingroup$ The most recent review I could find on this subject was from 1999 — maybe you can use that as a starting point to find out more ... $\endgroup$ – tyersome Jan 13 '20 at 20:18

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