(742i) Binding and Kinetics of Coumarin Amphiphiles with Composite Lipid Bilayer

In this work, we thermodynamically characterize the interaction of novel amphiphilic coumarin molecules with liposomes. The binding and organization of these polar molecules to the negatively charged bilayer is characterized by thermo-analytic techniques such as Isothermal Titration Calorimetry and Differential Scanning Calorimetry. The interaction between coumarin amphiphiles and lipid bilayer results in changes in the physicochemical properties of the bilayer. In this work, the mechanism of binding between coumarin amphiphiles and a composite bilayer composed of charged lipids has been investigated. We have compared the values of dissociation constant (K_d), Gibbs Free Energy (ΔG), partition coefficient (P_m), and no. of binding sites (n) from each of the techniques to determine if the binding affinity is enthalpy or entropy driven. We have concluded that the induced amphiphilicity in the coumarin molecule has resulted in an improved binding with the lipid bilayer. These results conform to the preliminary biological in-vitro activity. These fluorescent amphiphilic molecules have their proposed application in cancer photodynamic therapy.