Spectroscopic and calorimetric studies on the interaction between PAMAM G4-OH and 5-fluorouracil in aqueous solutions

The results of spectroscopic measurements (an increase in solubility, equilibrium dialysis, H-1 NMR titration) and calorimetric measurements (isothermal titration ITC) indicate spontaneous (Delta G<0) binding of 5-fluorouracil molecules by PAMAM G4-OH dendrimer with terminal hydroxyl groups in an aqueous solution. PAMAM G4-OH dendrimer bonds about n = 8 +/- 1 molecules of the drug with an equilibrium constant of K = 70 +/- 10. The process of saturating the dendrimer active sites by the drug molecules is exothermal (Delta H<0) and is accompanied by an advantageous change in entropy (Delta S>0). The parameters of binding 5-fluorouracil by PAMAM G4-OH dendrimer were compared with those of binding this drug by the macromolecules of PAMAM G3-OH and G5-OH. (C) 2016 Elsevier B.V. All rights reserved.