Multimodal Shape Transformation of Dual-Responsive DNA Block Copolymers.

ABSTRACT

Herein, we report the self-assembly and multimodal shape transformation of dual-responsive DNA di- and triblock copolymers. Dual-responsive DNA diblock copolymer was synthesized by coupling a thermoresponsive polymer, poly(N-isopropylacrylamide (PNIPAM), and an oligonucleotide. DNA-b-PNIPAM possesses thermoresponsive properties of PNIPAM as well as molecular recognition properties of DNA. Thus, they undergo reversible temperature-triggered transition at lower critical solution temperature (LCST) between molecular DNA and polymer micelles with high density DNA corona. The hybridization of DNA-b-PNIPAM and DNA-modified nanoparticles generates functional nanoparticles showing unique temperature-dependent aggregation and disaggregation behaviors due to the dual-responsive nature of DNA-b-PNIPAM. DNA triblock copolymers of DNA-b-PNIPAM-b-PMA were synthesized by introducing a hydrophobic block, poly(methyl acrylate) (PMA), to DNA/PNIPAM block copolymers, which form spherical micelles at room temperature. They are capable of nanoscale shape transformation through the combination of thermal trigger and DNA binding. DNA-b-PNIPAM-b-PMA micelles undergo sphere-to-cylinder shape changes above LCST due to the conformational change of PNIPAM. The shape change is reversible, and fast cylinder-to-sphere transition occurs when the temperature is lowered below LCST. The low temperature spherical morphology can also be accessed while keeping the temperature above LCST by introducing complementary DNA strands with single stranded overhang regions. These results demonstrate the multidimensional shape changing capability of DNA-b-PNIPAM-b-PMA enabled by the dual-responsive property.