Cyclodextrin-Containing Tannic Acid-Lipoic Acid Hydrogels for the Loading and Reduction-Responsive Release of Nile...

Hydrophobic molecules are generally difficult to incorporate into aqueous hydrogels because of their poor water solubility. In this study, a cyclodextrin (CD)-containing tannic acid-lipoic acid (TA-LA) hydrogel was developed using lipoic acid-modified β-cyclodextrin (LACD). LACD retained the host-guest recognition ability of the cyclodextrin cavity after lipoic acid modification and was successfully incorporated into the TA-LA hydrogel without interfering with gel formation. Using Nile Red (NR) as a model hydrophobic molecule, the LACD-containing hydrogel showed higher NR encapsulation efficiency and greater cyclodextrin retention than the hydrogel containing unmodified β-cyclodextrin. The LACD-containing hydrogel also exhibited reduction-responsive NR release in the presence of dithiothreitol (DTT). These results show that LACD can be incorporated into the TA-LA hydrogel while retaining the host-guest recognition ability of the cyclodextrin cavity and can be used for reduction-responsive release of NR.