The thermodynamics of cationic polymers binding to DNA were analyzed using isothermal titration calorimetry (ITC). Cationic macromolecules examined in this study included imidazolium-containing homopolymers and adenine-containing polyelectrolytes. Each polymer was titrated into a solution of DNA and the heats associated with the formation of polymer-DNA complexes (polyplexes) were measured. From these measurements, the enthalpy, entropy, free energy, stoichiometry, and equilibrium constant of binding were calculated using an appropriate binding model. The results indicate that while all of the polymers investigated form polyplexes spontaneously, the thermodynamics associated with binding vary significantly for the different functional groups. For example, the imidazolium-containing polymer complexation appears to be entropically driven with counter-ion release upon binding. However, when an adenine comonomer is incorporated into the polymer backbone, a much greater enthalpic contribution is observed. This result is likely due to the combination of the electrostatic forces and the hydrogen bonding interactions between adenine and DNA.

Isothermal titration calorimetry: Unlocking the thermodynamics of polycation-DNA complexation

245th National Meeting (2013)

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