Complexation behavior of DNA block copolymer with ionic liquid

Abstract

Bioconjugate block copolymers that incorporate both synthetic polymers and nucleotides have been extensively investigated, capitalizing on the distinctive attributes of DNA while preserving the mechanical and chemical properties inherent in synthetic polymers. The anticipation is that DNA block copolymers will give rise to diverse self-assembling nanostructures, including spherical micelles, cylindrical micelles, bicontinuous structures, vesicles, and large compound micelles (LCM) when dissolved in solutions. This thesis delves into the examination of the complexation behavior exhibited by DNA block copolymers with various ionic liquids and synthetic polymers. In Chapter 3, the study involved the synthesis of dsDNA-b-PEG diblock copolymer through a coupling reaction, followed by their complexation with two distinct ionic liquids at various ratios. The interaction between the ionic liquids and the DNA block copolymer was assessed using a fluorescence binding assay. The structural configurations of the complexes were examined using transmission electron microscopy and dynamic light scattering. The observed complexation behavior was found to be influenced by the hybridization state of the DNA, with variations in the DNA and covalently bonded PEG resulting in complex particle-like spherical structures. A mechanism elucidating this complexation behavior was presented in the study. In Chapter 4, we synthesized various types of ssDNA-b-PEG diblock copolymers, employing the same analytical techniques. The findings affirmed that the ionic liquid played a role in dissociating the aggregated polymer chains of the ssDNA diblock copolymers. Despite the occurrence of binding between the ionic liquid and ssDNA, no highly complexed structure was observed. Even though the ratio of ionic liquid increased, the ssDNA block copolymers was stabilized to unimer state. In Chapter 5, we synthesized ssDNA-b-PNIPAM diblock copolymers. The PNIPAM polymer was synthesized using reversible addition-fragmentation chain-transfer polymerization (RAFT), and the resulting block copolymer was purified by gel electrophoresis. Similar to the methodology outlined in Chapter 3, we examined the binding of ionic liquid with the DNA block copolymer using a fluorescence binding assay. To assess thermoresponsive behavior, dynamic light scattering was employed, confirming the potential formation of complex structures and investigated the mechanism with ssDNA. Furthermore, the temperature-dependent trends observed in the complex solution highlighted the distinctive behavior of ssDNA-b-PNIPAM.