Water-soluble dendritic unimolecular micelles: their potential as drug delivery agents.

To explore the potential of dendritic unimolecular micelles in drug delivery systems, dendritic unimolecular micelles with a hydrophobic core surrounded by a hydrophilic shell were prepared by coupling dendritic hypercores with poly(ethylene glycol) [PEG] mesylate. The monomer selected to build the dendritic cores was 4, 4-bis(4'-hydroxyphenyl) pentanol as this large monomer unit provides flexibility to the dendritic structure while contributing to the "container" capacity of the overall structure. Four generations of dendritic hypercores with six, 12, 24, and 48 phenolic end groups were prepared. Subsequent coupling reactions with PEG mesylate afforded four generations of dendritic unimolecular micelles. The micelles were characterized by Matrix Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS), 1H-NMR and Gel Permeation Chromatography (GPC). The "container" property of micelles was demonstrated by solubilizing pyrene in aqueous solution. Entrapment of the model drug indomethacin in the dendritic micelles was achieved at 11 wt.% loading level, and preliminary in vitro release tests showed that sustained release characteristics were achieved.