Thread by @nagiblab, Hospitals are running out of #masks ... forcing our healthcare heroes to [...]

Hospitals are running out of #masks ... forcing our healthcare heroes to put their lives at risk by reusing them ... the FDA just approved a safer way to do this for the #COVID19 emergency only ... How? Why?

a chemistry explainer

Hospitals are running out of #masks ... forcing our healthcare heroes to put their lives at risk by reusing them ... the FDA just approved a safer way to do this for the #COVID19 emergency only ... How? Why?a chemistry explainer

First off, we’re not talking those flat surgical masks like at the dentist office (that block bodily fluids), but rather fitted #N95 respirators - that actually *filter* small airborne particles.
https://www.cdc.gov/niosh/npptl/pdfs/UnderstandDifferenceInfographic-508.pdf

The filter technology relies on polypropylene polymer (the same hard plastic used in Tupperware) that is tangled in a mesh of nanofibers - 10x thinner than human hairs.

Viruses are so big (

are made up of genes, wrapped in proteins, covered in fat ... see great explainer by @jenheemstra) that they're trapped in these mesh nets ... along w/ bacteria (100x larger) & other pathogens (1000x) ... from both sides of mask https://twitter.com/jenheemstra/status/1244043656740458499

https://twitter.com/jenheemstra/status/1244043656740458499

Soap is ordinarily a great way to break up the protective outer lipid coating of a

... obliterating it!
(s/o @PalliThordarson)
... but just like hair gets frizzy after a bath, N95 nanofibers can also deform when wet - losing their filtering ability. https://twitter.com/PalliThordarson/status/1236549305189597189

https://twitter.com/PalliThordarson/status/1236549305189597189

How about dry cleaning? Despite the name, this also uses liquid solvents (organic molecules vs H2O) to wash away dirt (organic matter) b/c ‘like-dissolves-like’ ... unfortunately, fragile polypropylene masks won’t hold up here either.

: @compoundchem
https://cen.acs.org/content/dam/cen/95/45/09545-sci2.pdf

How about dry cleaning? Despite the name, this also uses liquid solvents (organic molecules vs H2O) to wash away dirt (organic matter) b/c ‘like-dissolves-like’ ... unfortunately, fragile polypropylene masks won’t hold up here either. : @compoundchem https://cen.acs.org/content/dam/cen/95/45/09545-sci2.pdf

>What else is there???
>Hydrogen peroxide! (aka H2O2)
Yes, that same liquid you use on cuts (but no longer recommended by Mayo Clinic: https://www.mayoclinic.org/first-aid/first-aid-cuts/basics/art-20056711) ... but a 10x stronger version.

Cuts and scrapes: First aid

How to administer first aid for a cut or scrape.

https://www.mayoclinic.org/first-aid/first-aid-cuts/basics/art-20056711

As you see with that instant fizzing (from release of O2 & H2O), hydrogen peroxide is reactive!

Side note: Why Does Hydrogen Peroxide Fizz On Cuts? https://www.livescience.com/33061-why-does-hydrogen-peroxide-fizz-on-cuts.html

Why Does Hydrogen Peroxide Fizz On Cuts?

https://www.livescience.com/33061-why-does-hydrogen-peroxide-fizz-on-cuts.html

Hydrogen peroxide (H2O2) is a mild oxidant (unless you convert it to piranha acid, which chews up everything!)
... it very quickly reacts with proteins (~1 million times/sec) by several mechanisms ...
Key reminder:

are *covered* in proteins.

Hydrogen peroxide (H2O2) is a mild oxidant (unless you convert it to piranha acid, which chews up everything!)... it very quickly reacts with proteins (~1 million times/sec) by several mechanisms ... Key reminder: are *covered* in proteins.

So just dip in peroxide? Not quite ... this 35% H2O2 solution in H2O still has too much water. Some hospitals use more concentrated plasma peroxide to sterilize surgical instruments, but this is likely too harsh for repeat use on masks.

Another idea is to vaporize hydrogen peroxide (VHP) ... allowing gaseous H2O2 to seep into every nook and microscopic cranny. This strategy was researched by a nonprofit lab in Columbus, Ohio 5 yrs ago & it’s now temporarily approved for this emergency https://www.theverge.com/2020/3/29/21198715/fda-approves-battelles-decontaminate-n95-face-masks-coronavirus

FDA approves Battelle’s process to decontaminate N95 face masks

The coronavirus outbreak has led to a severe shortage of the face masks

https://www.theverge.com/2020/3/29/21198715/fda-approves-battelles-decontaminate-n95-face-masks-coronavirus

Anticipating a crisis where masks might need to be reused, @US_FDA contracted @Battelle in 2015 to develop the best "recipe" for decontamination by H2O2 (VHP) including length of time, concentration, & number of washes before N95 loses filtering ability https://www.battelle.org/newsroom/press-releases/press-releases-detail/battelle-ccds-critical-care-decontamination-system-being-deployed-to-meet-urgent-need-for-personal-protective-equipment-for-nation-s-healthcare-workforce

Battelle CCDS Critical Care Decontamination System™ Being Deployed to Meet Urgent Need for Personal...

Battelle announced today that it has begun rapid manufacturing of a system to decontaminate N95 respirator masks and other medical protective equipment. Each Battelle CCDS Critical Care Decontamina...

https://www.battelle.org/newsroom/press-releases/press-releases-detail/battelle-ccds-critical-care-decontamination-system-being-deployed-to-meet-urgent-need-for-personal-protective-equipment-for-nation-s-healthcare-workforce

Here is their working system in action ...
It decontaminates harmful biological contaminants using the chemistry of vapor peroxide (H2O2) so well that it only has a 1 in 1,000,000 chance of leaving behind a non-sterile unit https://twitter.com/Battelle/status/1245064345500999681

https://twitter.com/Battelle/status/1245064345500999681

Great! Problem solved? Sorta ...
Mobile units are already being setup in OH & NYC. But there are serious barriers to widespread DIY use in every hospital across US ...
Concentrated peroxide is corrosive, oxidizing, & residue can be toxic.

Proper engineering of the chambers can address safety concerns related to storing/handling concentrated peroxide & ensuring < 1 ppm @CDCgov thresholds of peroxide left on mask

Temperature regulation is also key ... since peroxides generate free radicals if heated too high (~150*C). These hydroxyl radicals can pluck the hydrogen atoms right off the polypropylene masks!

Fortunately, the system @Battelle developed 5 yrs ago to address these potential issues with using peroxide to clean masks is now @US_FDA approved ... and it’s already being put to use

Of course, science is about always improving ...
which is why scientists have united to continue building on this technology & others ( #n95decon) to ensure our healthcare heroes remain safe ... even if masks *must* be reused
Read more about this team: https://www.n95decon.org

N95DECON - A scientific consortium for data-driven study of N95 FFR decontamination

https://www.n95decon.org

Thanks for reading. Be safe!

And check out these amazing infographics by @compoundchem:

Coronavirus tests:
https://twitter.com/compoundchem/status/1240909978896138241

Destroy coronavirus: https://twitter.com/compoundchem/status/1245251697724862470