The technique that was used to produce the Moderna vaccine is the same
that was used producing the Pfizer/BioNTech vaccine. A piece of
messenger RNA (mRNA) encoding the spike protein of the SARS-CoV-2 virus
is inserted into a fat globule made of nanoparticles. Nanoparticles come
in many shapes and forms and are made among others from fats, proteins,
polymers, metals, silica and carbon. The term "nano" refers to
the size of the particles and says nothing about the material used. For
use in medicine, nanoparticles are available that are made of polymers,
proteins and fats.
In the specific case of Pfizer/BioNTech's and Moderna's mRNA vaccines,
the nanoparticle is a fat globule that serves as packaging of the mRNA.
This allows the mRNA to pass the barrier of the cell membrane of the
body's own cells. In this way, the mRNA is delivered to the cell where
it can do its job. The nanoparticle is composed of fatty acids -
phospholipids - which organize themselves in the form of a sphere so
that the nanoparticles are soluble in water. These phospholipids form
the outer layer demonstrated in the illustration below. Another fatty
acid with a positive charge binds and protects the mRNA and these are
visible as light blue spheres in the illustration. A third component of
the fat globule is cholesterol, which stabilizes the fat globule. A
final component of these nanoparticles is the polyethylene glycol (PEG),
which extends the half-life of the fat globule, making it less likely
to disintegrate (3). Animal studies have actually shown that these
nanoparticles have another important function as "packaging materials":
they cause different types of immune system cells to travel to the
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