posted on 2021-05-04, 15:06authored byPanagiotis
G. Georgiou, Huba L. Marton, Alexander N. Baker, Thomas R. Congdon, Thomas F. Whale, Matthew I. Gibson
Ice binding proteins
modulate ice nucleation/growth and have huge
(bio)technological potential. There are few synthetic materials that
reproduce their function, and rational design is challenging due to
the outstanding questions about the mechanisms of ice binding, including
whether ice binding is essential to reproduce all their macroscopic
properties. Here we report that nanoparticles obtained by polymerization-induced
self-assembly (PISA) inhibit ice recrystallization (IRI) despite their
constituent polymers having no apparent activity. Poly(ethylene glycol),
poly(dimethylacrylamide), and poly(vinylpyrrolidone) coronas
were all IRI-active when assembled into nanoparticles. Different core-forming
blocks were also screened, revealing the core chemistry had no effect.
These observations show ice binding domains are not essential for
macroscopic IRI activity and suggest that the size, and crowding,
of polymers may increase the IRI activity of “non-active”
polymers. It was also discovered that poly(vinylpyrrolidone)
particles had ice crystal shaping activity, indicating this polymer
can engage ice crystal surfaces, even though on its own it does not
show any appreciable ice recrystallization inhibition. Larger (vesicle)
nanoparticles are shown to have higher ice recrystallization inhibition
activity compared to smaller (sphere) particles, whereas ice nucleation
activity was not found for any material. This shows that assembly
into larger structures can increase IRI activity and that increasing
the “size” of an IRI does not always lead to ice nucleation.
This nanoparticle approach offers a platform toward ice-controlling
soft materials and insight into how IRI activity scales with molecular
size of additives.