Interaction between PAMAM-NH2 G4 dendrimer and paracetamol in aqueous solution

Interactions between PAMAM-NH2 G4 dendrimer and paracetamol in aqueous solutions were examined by UV spectroscopy, equilibrium dialysis, H-1 NMR spectroscopy and calorimetric techniques. The results of equilibrium dialysis show that PAMAM-NH2 G4 dendrimer can combine 18 paracetamol molecules with equilibrium constant K = 280 +/- 40. Using the method of calorimetric titration (ITC), it has been found that the paracetamol addition to dendrimer is an exothermic process. Based on the model of two active sites in a dendrimer molecule, the results of equilibrium dialyses were described and it was calculated that a molecule of dendrimer has about three sites strongly combining paracetamol (K-1 = 2100 +/- 670) and about 15 sites that weakly combine the drug (K-2 = 130 +/- 30). The measurements of paracetamol solubility in aqueous solutions of PAMAM-NH2 G4 dendrimer confirm the paracetamol addition to this dendrimer. (C) 2013 Elsevier B.V. All rights reserved.