Nanoarchitectures by hierarchical self-assembly of ursolic acid: entrapment and release of fluorophores including anticancer drug doxorubicin†
Ursolic acid, a naturally occurring 6-6-6-6-6 monohydroxytriterpenic acid, is extractable from the leaves of Plumeria rubra. In continuation of our ongoing efforts on the studies of the self-assembly properties of naturally occurring triterpenoids, herein, we report our detailed investigation on the self-assembly of this ursane type triterpenic acid in different liquids. The molecule self-assembles in most organic as well as aqueous organic liquids yielding nano-architectures such as vesicles, tubes, fibers and flowers affording supramolecular gels in many of the liquids studied. Characterization of the self-assemblies has been carried out using atomic force microscopy, scanning electron microscopy, transmission electron microscopy, optical microscopy, dynamic light scattering, FTIR and X-ray diffraction studies. The self-assemblies have been utilized for the entrapment of fluorophores including an anticancer drug, doxorubicin. Release of the entrapped fluorophores including doxorubicin has been demonstrated at physiological pH as well as lower pH values.