A thermoresponsive amphiphilic dendron — Synthesis, characterization, and self-assembled micelles for controlled drug release

A new third-generation thermoresponsive amphiphilic dendron consisting of a hydrophobic poly(benzyl ether) dendritic core and hydrophilic oligo(ethylene glycol) peripheries was synthesized by an efficient convergent approach. Its structure was confirmed by 1H NMR, 13C NMR, IR, GPC, MALDI-TOF MS, and elemental analysis. Turbidity and dynamic light scattering (DLS) measurements demonstrated that the dendron showed a reversible temperature-dependent phase-transition behavior in aqueous solution and its lower critical solution temperature (LCST) was lower than that of the corresponding second-generation dendron, indicating the dependence of LCSTs on the generation of dendrons. Fluorescent spectroscopy and TEM studies revealed that the dendron would self-assemble into nanospherical micelles with a very low critical micelle concentration (CMC) in water. The core-shell structure of the micelles was proved by 1H NMR analyses of the micelles in D2O. The drug-loading capacity of the dendron micelles is about 29 wt % for podophyllotoxin (POD) used as a model drug, and in vitro release tests showed a desired thermoresponsive drug-release behavior. These results indicate that the dendron is promising as stimuli-responsive material for biomedical applications.