Disulfide-Functionalized Unimolecular Micelles as Selective Redox-Responsive Nanocarriers.

Redox-sensitive hyperbranched dendritic-linear polymers (HBDLPs) were prepared and stabilized individually as unimolecular micelles with diameters in the range 25-40 nm. The high molecular weight (500-950 kDa), core-shell amphiphilic structures were synthesized through a combination of self-condensing vinyl copolymerization (SCVCP) and atom transfer radical polymerization (ATRP). Cleavable disulfide bonds were introduced, either in the backbone, or in pendant groups, of the hyperbranched core of the HBDLPs. By triggered reductive degradation, the HBDLPs showed up to a 7-fold decrease in molecular weight, and the extent of degradation was tuned by the amount of incorporated disulfides. The HBDLP with pendant disulfide-linked functionalities in the hyperbranched core was readily postfunctionalized with a hydrophobic dye, as a mimic for a drug. An instant release of the dye was observed as a response to a reductive environment similar to the one present intracellularly. The proposed strategy shows a facile route to highly stable unimolecular micelles, which attractively exhibit redox-responsive degradation and cargo release properties.