Synthesis and characterization of variable-architecture thermosensitive polymers for complexation with DNA

Area of Science:

• Polymer Chemistry
• Biomaterials Science
• Nanotechnology

Background:

• Development of responsive polymers for controlled drug/nucleic acid delivery.
• Understanding polymer-DNA interactions is crucial for gene therapy and biomaterial applications.
• Lower Critical Solution Temperature (LCST) polymers offer tunable properties based on temperature.

Purpose of the Study:

• To synthesize and characterize novel polycations with LCST behavior by grafting copolymers onto branched poly(ethyleneimine).
• To investigate the structural changes and DNA complexation behavior of these polymers in response to temperature variations.
• To explore the microstructural changes in polymer-DNA complexes using advanced imaging techniques.

Main Methods:

• Synthesis of N-isopropylacrylamide-based copolymers grafted to poly(ethyleneimine).
• Spectroscopic techniques (UV-Vis, fluorescence) and light scattering for phase transition analysis.
• Ethidium bromide displacement assays for DNA interaction studies.
• Atomic Force Microscopy (AFM) for microstructural analysis of polymer-DNA complexes.

Main Results:

• Synthesized polycations exhibited tunable LCST behavior.
• Temperature-induced structural changes in polymers were mirrored in their DNA complexes.
• AFM revealed microstructural heterogeneities in complexes not detectable by light scattering.
• Variable-temperature AFM showed non-uniform compaction of individual complexes above LCST.

Conclusions:

• Responsive polymer-DNA complex structures are highly dependent on polymer architecture, solvent, and stoichiometry.
• LCST-mediated changes can accentuate sample heterogeneities in polymer-DNA condensates.
• These findings have implications for understanding cellular uptake and nucleic acid transport mechanisms.