Thermoresponsive nanogels based on polyelectrolyte complexes between polycations and functionalized hyaluronic acid.

A novel kind of thermoresponsive polyelectrolyte complex-based nanogels (PEC-NGs) was elaborated by mixing hyaluronic acid (HA) functionalized with Jeffamine® M-2005 (M2005, a thermoresponsive amine-terminated polyether) and diethylaminoethyl dextran (DEAE-D) or poly-l-lysine (PLL) in water. The presence of M2005 grafts led to PEC-NGs with larger particle size, lower net surface charge and thermoresponsiveness, namely shrinkage with increasing hydrophobicity at higher temperature. Both M2005 grafts and replacing DEAE-D with PLL as polycation allowed PEC-NGs to have higher stability against salinity and better encapsulation of curcumin, most probably through intraparticle hydrophobic interactions, whereas interparticle hydrophobic interactions may facilitate particle aggregation over time. Curcumin encapsulation can be optimized by applying higher temperature during the complexation. Enzymatic degradability of PEC-NGs was also verified through particle size evolution in the presence of hyaluronidase. These results provide new insights into the physicochemical aspect of such systems as promising nanocarriers for drug delivery.