Controlling the binding of hydrophobic drugs with supramolecular assemblies of β-cyclodextrin

Abstract

Supramolecular assemblies generated from self-assembling β-cyclodextrin were evaluated as hydrophobic drug carriers in vitro in aqueous conditions. The native β-cyclodextrin macrocycle was used to develop the novel host-guest assemblies with antitumor drug 2,2′-bibenzimidazole and its new derivate with n-nonyl groups at the nitrogen atoms. The morphology and sizes of these assemblies were characterized by NMR spectroscopy, DLS and TEM techniques. The interaction of the two bibenzimidazole guests with the carrier and their releasing properties under action of exogenous surfactant were investigated by means of UV–vis and fluorescence spectroscopy, DLS and TEM. The study of effect of a cationic surfactant, cetyltrimethylammonium bromide, on the stability of β-cyclodextrin–guest assemblies revealed the higher affinity of β-cyclodextrin for guest with n-nonyl groups and the higher stability of the resulting assemblies compared to those in the case of non-alkylated guest. The non-alkylated guest-rich carrier was disrupted rapidly when mixed with a surfactant trigger. The disruption of β-cyclodextrin–guest assemblies was accompanied by competitive inclusion of surfactant in β-cyclodextrin cavity which resulted in drug release from β-cyclodextrin carrier. The results of this study demonstrate the feasibility and usefulness of a trigger-responsive delivery of hydrophobic drugs using soft β-cyclodextrin assemblies.