Study of the interactions of PAMAM G3-NH2 and G3-OH dendrimers with 5-fluorouracil in aqueous solutions

The results of spectroscopic measurements (increase in solubility, equilibrium dialysis, (1)H NMR titration) and calorimetric measurements (isothermal titration ITC) indicate spontaneous (ΔG<0) bonding of 5-fluorouracil by both cationic PAMAM G3-NH2 dendrimer and hydroxyl PAMAM G3-OH dendrimer in aqueous solutions. PAMAM G3-NH2 dendrimer bonds about n= 25±8 drug molecules. Some of them n1= 5±1 are bonded by terminal amine groups with equilibrium constant K1= 3890±930, while the remaining ones n2= 24 ±3 are bonded by amide groups with equilibrium constant K2= 110±30. Hydroxyl PAMAM G3-OH dendrimer bonds n=6.0±1.6 molecules of 5-fluorouracil through tertiary amine groups with equilibrium constant K= 65±10. The parameters of bonding 5-fluorouracil by PAMAM G3-NH2 and G3-OH dendrimer were compared with those of bonding this drug by the macromolecules of PAMAM of generations G4-NH2, G5-NH2 and G5-OH.