The interactions between dendrimers and different types of drugs are nowadays one of the most actively investigated areas of the pharmaceutical sciences. The interactions between dendrimers and drugs can be divided into: internal encapsulation, external electrostatic interaction, and covalent conjugation. In the present study, we investigated the potential of poly(amidoamine) (PAMAM) dendrimers for solubility of four iminodiacetic acid derivatives. We reported that PAMAM dendrimers contribute to significant solubility enhancement of iminodiacetic acid analogues. The nature of the dendrimer-drug complexes was investigated by (1)H NMR and 2D-NOESY spectroscopy. The (1)H NMR analysis proved that the water-soluble supramolecular structure of the complex was formed on the basis of ionic interactions between terminal amine groups of dendrimers and carboxyl groups of drug molecules, as well as internal encapsulation. The 2D-NOESY analysis revealed interactions between the primary amine groups of PAMAM dendrimers and the analogues of iminodiacetic acid. The results of solubility studies together with (1)H NMR and 2D-NOESY experiments suggest that the interactions between PAMAM dendrimers of generation 1-4 and derivatives of iminodiacetic acid are based on electrostatic interactions and internal encapsulation.Electronic supplementary material The online version of this article (doi:10.1007/s10867-012-9277-5) contains supplementary material, which is available to authorized users.
Keywords: Electrostatic interactions; Iminodiacetic acid; MRI contrast agents; PAMAM dendrimers; Solubility studies.