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But wasn't there an issue before of prion contamination with surgical instruments used in ophtalmic surgery. I am sure those would have been autoclaved and rep

But wasn't there an issue before of prion contamination with surgical instruments used in ophtalmic surgery. I am sure those would have been autoclaved and reprocessed at some ridiculous pH value, no?

throwaway0a5e 5y ago
>I am sure those would have been autoclaved and reprocessed at some ridiculous pH value, no? Probably not until they had reason to do so. "Hot acidic environment" is hell when it comes to corrosion and the engineering incentive for medical stuff is only to be as corrosion resistant as you need because there are other design considerations and the most corrosion resistant stainless steels are not the bet fit for building a super precise needle you're gonna poke around in someone's eye so you wind up wanting to pick a middle ground alloy. Picking a middle ground alloy puts a hard limit on what you can do to clean your instruments before you degrade them in unacceptably short order. I don't know how things have changed since. My medical manufacturing experience is out of date and limited.
persedes 5y ago
yeah I wouldn't count on prions being as easily denatured as other proteins. E.g. mad cow disease spread because prions are not killed by simply cooking / boiling it.
- resoluteteeth 5y ago
  Is there some specific reason to think that prions are harder to denature than other proteins? It seems like mad cow disease could also spread simply because meat is not normally cooked to ensure that 100% of the proteins in it are denatured.
  - nebopolis 5y ago
    Prions are essentially already denatured/unfolded. They are a more stable state of a normal protein that has biological function, and they interact with the "correctly" folded proteins to cause them to denature into additional prions. Often denaturing a prion means actually breaking apart the protein into fragments or amino acids, because it is already at the most stable/denatured state. This is also why they are so persistent in nature and so hard to remove from surfaces. Apparently gas plasma sterilization is a promising possibility. (this seems like an ok overview of the challenges: https://pubmed.ncbi.nlm.nih.gov/21271212/ https://pubmed.ncbi.nlm.nih.gov/21271212/). Current procedures include things like autoclaving in 121C sodium hydroxide for 30 minutes. Definitely not something that fully cooking will inactivate.
    - persedes 5y ago
      In addition prions seem to contain disulfide bonds, which tend to make proteins even more stable. (RNAse for example has them and is notoriously hard to get rid off unless you treat it with essentially H2S). I haven't found a source for that, but according to my bio teacher mad cow disease started, because they decided to lower the temperature to pretreat animal waste (such as bones and brain matter...) which then ended up in what cows get fed with. Wikipedia mentioned nowadays they simply leave out the bones and brain from the food.

throwaway0a5e 5y ago

>I am sure those would have been autoclaved and reprocessed at some ridiculous pH value, no? Probably not until they had reason to do so. "Hot acidic environment" is hell when it comes to corrosion and the engineering incentive for medical stuff is only to be as corrosion resistant as you need because there are other design considerations and the most corrosion resistant stainless steels are not the bet fit for building a super precise needle you're gonna poke around in someone's eye so you wind up wanting to pick a middle ground alloy. Picking a middle ground alloy puts a hard limit on what you can do to clean your instruments before you degrade them in unacceptably short order. I don't know how things have changed since. My medical manufacturing experience is out of date and limited.

persedes 5y ago

yeah I wouldn't count on prions being as easily denatured as other proteins. E.g. mad cow disease spread because prions are not killed by simply cooking / boiling it.

resoluteteeth 5y ago
Is there some specific reason to think that prions are harder to denature than other proteins? It seems like mad cow disease could also spread simply because meat is not normally cooked to ensure that 100% of the proteins in it are denatured.
- nebopolis 5y ago
  Prions are essentially already denatured/unfolded. They are a more stable state of a normal protein that has biological function, and they interact with the "correctly" folded proteins to cause them to denature into additional prions. Often denaturing a prion means actually breaking apart the protein into fragments or amino acids, because it is already at the most stable/denatured state. This is also why they are so persistent in nature and so hard to remove from surfaces. Apparently gas plasma sterilization is a promising possibility. (this seems like an ok overview of the challenges: https://pubmed.ncbi.nlm.nih.gov/21271212/ https://pubmed.ncbi.nlm.nih.gov/21271212/). Current procedures include things like autoclaving in 121C sodium hydroxide for 30 minutes. Definitely not something that fully cooking will inactivate.
  - persedes 5y ago
    In addition prions seem to contain disulfide bonds, which tend to make proteins even more stable. (RNAse for example has them and is notoriously hard to get rid off unless you treat it with essentially H2S). I haven't found a source for that, but according to my bio teacher mad cow disease started, because they decided to lower the temperature to pretreat animal waste (such as bones and brain matter...) which then ended up in what cows get fed with. Wikipedia mentioned nowadays they simply leave out the bones and brain from the food.