Comprehensive characterization of surface-functionalized poly(amidoamine) dendrimers with acetamide, hydroxyl, and carboxyl groups

Terminal amine groups of poly(amidoamine) (PAMAM) dendrimers can be substituted with different functional groups for various applications. In this study, PAMAM derivatives with acetamide, hydroxyl, and carboxyl termini were synthesized from ethylenediamine (EDA) core generation 4 and 5 primary amine-terminated PAMAM dendrimers. The reaction products were purified with dialysis and subsequently characterized by polyacrylamide gel electrophoresis (PAGE), capillary electrophoresis (CE), size exclusion chromatography (SEC), matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, potentiometric titration, 1H NMR, and 13C NMR. PAGE and CE electropherograms provide data regarding the purity, charge distribution, and electrophoretic mobility of the dendrimers and their derivatives. SEC and MALDI-TOF mass spectrometry detect the average absolute molar mass and the individual mass fractions, respectively. The combination of SEC with potentiometric titration provides quantitative evidence of the degree of the functional group substitution, while NMR techniques (both 1H NMR and 13C NMR) confirmed the changes in dendrimer surface functionalization. This study provides a general example for the comprehensive characterization of surface-functionalized PAMAM dendrimer nanoparticles. The synthesized dendrimer derivatives hold promise for environmental and medical applications.