Self-assembled pH-responsive supramolecular hydrogel for hydrophobic drug delivery

In this study, a novel supramolecular hydrogel system, abbreviated as AGC₁₆/NTS, prepared by molecular self-assembly of cationic gemini surfactant 1,3-bis(N,N-dimethyl-N-cetylammonium)-2-propylacrylatedibromide (AGC₁₆) and anionic aromatic compound trisodium 1,3,6-naphthalenetrisulfonate (NTS), was used to encapsulate hydrophobic model drug curcumin (Cur), constructing a pH-responsive drug delivery system. Cur was effectively encapsulated into the hydrophobic domains of AGC₁₆/NTS through hydrophobic interaction, which was confirmed by ¹H NMR measurement. The effects of Cur on the mechanical strength, phase transition behaviour and morphology of AGC₁₆/NTS were characterized by rheology and cryogenic scanning electron microscopy (cryo-SEM) methods. The pH-responsive release of Cur from AGC₁₆/NTS was obtained and the release amount of Cur ascended with pH value decreasing from 7.4 to 3.0. The hydrodynamic sizes of the released Cur-aggregates determined by dynamic light scattering (DLS) were used to analyse the release process of Cur at different pH. The cell viability assay and cell imaging experiment demonstrated that Cur-loaded hydrogel has much higher cytotoxicity and better cell uptake compared to free Cur. Overall, the AGC₁₆/NTS hydrogel is a prospective material for use in encapsulation and controlled-release of hydrophobic drug molecules.