  Hyaluronan (HA) is among the most used biopolymers for viscosupplementation
and cosmetic applications. However, the current injectable HA-based
formulations present relevant limitations: I) unmodified HA is quickly degraded
by endogenous hyaluronidases (HAase), resulting in short lasting properties;
II) cross-linked HA, although shows enhanced stability against HAase, often
contains toxic chemical cross-linkers. As such, herein, we present
biocompatible self-assembled hyaluronan-cholesterol nanohydrogels (HA-CH NHs)
able to bind to HAase and inhibit the enzyme activity in vitro, more
efficiently than currently marketed HA-based cross-linked formulations (e.g.
JonexaTM). HA-CH NHs inhibit HAase through a mixed mechanism, by which NHs bind
to HAase with an affinity constant 7-fold higher than that of HA. Similar NHs,
based on gellan-cholesterol, evidenced no binding to HAase, neither inhibition
of the enzyme activity, suggesting this effect might be due to the specific
binding of HA-CH to the active site of the enzyme. Therefore, HA-CH NHs were
engineered into injectable hybrid HA mixtures or physical hydrogels, able to
halt the enzymatic degradation of HA.
