Spectroscopic, electrochemical and calorimetric studies on the interactions of poly(propyleneimine) G4 dendrimer with 5-fluorouracil in aqueous solutions

Results of zeta potential measurements and of spectroscopic (increased solubility, equilibrium dialysis, H-1 NMR titration) and calorimetric measurements (isothermal ITC titration) indicate that fourth generation poly(propyleneimine) dendrimer (PPI G4) spontaneously binds (Delta G < 0) 5-fluorouracil (FU) molecules in aqueous environments. The poly(propyleneimine) G4 dendrimer binds approximately n = 42 +/- 3 drug molecules with an equilibrium constant of K = 220 +/- 30. The process of saturation of dendrimer active centres with drug molecules is exothermic (Delta H < 0) and accompanied by increased ordering of reagents (Delta S < 0). Results of equilibrium dialysis indicate that poly(propyleneimine) G4 dendrimer has two sets of active centres comprising: n(1) = 5 +/- 1 sites with higher binding constant towards 5-fluorouracil and n(2) = 39 +/- 3 sites with lower binding constant towards this particular drug. The obtained results of a study on binding of 5-fluorouracil by the poly(propyleneimine) G4 dendrimer were compared with results for binding of this drug by poly (amidoamine) (PAMAM) G4 dendrimer macromolecules with the same number of surface, primary amine groups. (C) 2020 Elsevier B.V. All rights reserved.