A well-defined coil-comb polycationic brush with "star polymers" as side chains for gene delivery

Novel well-defined coil-comb polycationic brushes were synthesized via atom transfer radical polymerization and used as gene carriers. The side chains of the comb block were composed of star polymers with cyclodextrin as the core and poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) as the arm. The DNA binding capability of the brushes was characterized, and the cytotoxicity and transfection efficiency were investigated in COS-7 and 293T cells. With such super-high grafting density of PDMAEMA, the brushes effectively condensed pDNA into spherical nanoparticles of 100-200 nm in size and exhibited significantly higher transfection capability compared to the single star polymer. In some cases, they also showed comparable or higher transfection efficiency and lower cytotoxicity than PEI25K. The results indicated that these brushes had good promise for the potential gene therapy. Actually, this work also provides a versatile method to prepare polymer brushes with such unique structure and flexible functionality, which has wide applications in the fields of biomedical devices, electronics and catalysts.