PEGylated DNA Helper Molecule Assisted Polyelectrolyte Complex Micelle Formation

Complexation of negatively charged oligoDNAs with cationic polymers forms complex coacervates with sizes in the range of a few micrometers. To limit the phase separation to nanometer length scales, the oligoDNA strands can be complexed with charged-neutral block copolymers to form polyelectrolyte complex micelles (PCMs). In this contribution, we report a new strategy in which PEGylated DNA helper molecules are utilized to assist nanosized PCM formation between target oligoDNAs and cationic homopolymers. We synthesize PEGylated DNA helper molecules by a solution phase coupling reaction. The helper molecules are then hybridized to the ends of the target oligoDNA to form pseudo block copolymers. Following the complexation with polyethylenimine (PEI), PCMs are formed consisting of an oligoDNA/PEI core and a PEG corona. The PCM sizes formed by using helper molecules of different PEG lengths are determined by a combination of dynamic light scatting, small-angle X-ray scattering, and transmission electron microscopy. The stability of the PCMs against enzyme digestion and different salt concentrations are also investigated.