Comb-Dendritic Block Copolymers as Tree-Shaped Macromolecular Amphiphiles for Nanoparticle Self-Assembly

An amphiphilic comb-dendritic block copolymer was designed and synthesized based on poly (γ- n -dodecyl- l -glutamate) as a hydrophobic comb block and a hydrophilic polyester dendron block modified with poly(ethylene glycol); the high persistence length of the rodlike helical polypeptide backbone within the comb block resulted in a “tree-like” architecture for this comb-dendritic block copolymer. In aqueous solution, the macromolecules self-assemble into spherical micelles with the hydrophobic comb blocks forming the inner core and the hydrophilic dendritic blocks forming the exterior shell. The cone-shaped morphology and the alkyl pendant groups enhance the stability of the micelles, resulting in unusually low critical micelle concentrations of approximately 10 - 8 M. The particle size of these micelles was pH dependent due to the presence of the high-density carboxylic acid groups at the surfaces of micelles. The drug loading capacity of the polymeric micelles is about 30 wt % for the hydrophobic bactericide, triclosan, used as a model drug. In addition, the nanoscale clustering of the peripheral acid groups are potential substrates for subsequent functionalization with biospecific ligands to improve biologically relevant affinity enhancement in targeting drug delivery applications.