.....Well, the latest MJOLNIR VI armors do include biofoam injectors in its design and those cover the body head to toe, so....whatever it does, the UNSC is confident enough to use it for their greatest soldiers in any possible wound so they don't have to use medkits.....because apparently despite all the other bells and whistles the Spartan enhancement process does to you, a regeneration factor is apparently too implausible for this universe....

oh hey the wiki has this picture of its warning label of a sort:
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Poly-ethyl-tri-phosphate, nitrous oxide accelerant.

to break that down:
-polyethylene is the most the common used plastic today
-a polyphosphate is a kind of salt formed from tetrahedral phosphate units linked sharing oxygen atoms, and in biology they are involved in energy storage, protein synthesis, lipid synthesis and carbohydrate metabolism
-nitrous oxide is laughing gas and has uses in dentistry and surgery for its pain-reducing effects and is on the world health' organizations one of the most safest and effective medicines

so this is a mix of nitrous oxide, plastic and some triphosphate being used as a foam to treat Romeo's wounds here. these guys went so far as to design THIS!? find a bunch of a bunch of chemicals that had plausible medical use then combine them to come up with a long fictional name, to make this weird foam-polymer-thing? that is some thorough worldbuilding if they're going as far as to make this label thing.