Protection from particulate matter (PM10 and PM2.5) and microorganisms using MOFs (metal–organic frameworks) and nanoparticles used in filtration has been a major challenge.
Ice-binding proteins (IBPs) produced by psychrophilic
organisms
to adapt for the survival of psychrophiles in subzero conditions have
received illustrious interest as a cryopreservation agent required
for cells and tissues to completely recover after freezing/thawing.
Depressing water-freezing point and avoiding ice-crystal growth affect
their activities which are closely related to the presence of ice
crystal well-matched binding moiety. The interaction of IBPs with
ice and water is critical in enhancing their freeze avoidance against
cell or tissue damage. Metal–organic frameworks (MOFs) with
a controllable lattice at the molecular level and a size at the nanometer
scale can offer periodically ordered ice-binding sites by modifying
organic linkers and controlling microcurvature at the ice surface.
Herein, zirconium (Zr)-based MOF-801 nanoparticles (NPs) with good
biocompatibility were used as a cryoprotectant that is well dispersed
and colloidal-stable in an aqueous solution. The MOF NP size was precisely
controlled, and 10, 35, 100, and 250 nm NPs were prepared. The specific
IBPs-mimicking pendants (valine and threonine) were simply introduced
into the MOF NP-surface through the acrylate-based functionalization
to endow with hydrophilic and hydrophobic dualities. When small-sized
MOF-801 NPs were attached to ice, they confined ice growth in high
curvature between the adsorption sites because of the decreased radius
of the convex area of the growth region, leading to highly enhanced
ice recrystallization inhibition (IRI). Surface-functionalized MOF
NPs could increase the number of anchored clathrate water molecules
with hydrophilic/hydrophobic balance of the ice-binding moiety, effectively
inhibiting ice growth. The MOF-801 NPs were biocompatible with various
cell lines regardless of concentration or NP surface-functionalization,
whereas the smaller-sized surface-functionalized NPs showed a good
cell recovery rate after freezing/thawing by induction of IRI. This
study provides a strategy for the fabrication of low-cost, high-volume
antifreeze nanoagents that can extend useful applications to organ
transplantation, cord blood storage, and vaccines/drugs.
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