Supramolecular Hydrogels from In Situ Host-Guest Inclusion between Chemically Modified Cellulose Nanocrystals and Cyclodextrin

When grafted beta-cyclodextrin is used as targeting sites, Pluronic polymers have been introduced on the surface of cellulose nanocrystals by means of inclusion interaction between beta-cyclodextrin and hydrophobic segment of the polymer. Because of the steric stabilization effect, surface poly(ethylene glycol) chains facilitate the dispersion and compatibility of nanocrystals, which also enhance the loading levels of nanocrystals in the hydrogel system. Meanwhile, uncovered poly(ethylene glycol) segments render the participating inclusion of alpha-cyclodextrin for the architecture of in situ hydrogels. Surface grafting and inclusion reactions were proved by solid C-13 NMR and FTIR. Grafting efficiency of beta-cyclodextrin and inclusion efficiency of Pluronic on the surface of nanocrystals were confirmed by UV spectroscopy and elemental analysis. A significant enhancement of the structural and thermal stability of in situ hydrogels with high loading levels of modified nanocrystals (>5.77 wt %) was observed by rheological analysis. Further study reveals the performance and behavior of hydrogels under a different pH environment. Finally, in situ hydrogels were used as drug carrier for in vitro release of doxorubicin and exhibit the behavior of prolonged drug release with special release kinetics.