Taylor dispersion analysis as a tool for size measurement of PAMAM dendrimers: the effect of generation, functionality and pH

Abstract

Taylor Dispersion Analysis (TDA) is explored to measure the hydrodynamic sizes of full and half generation PAMAM dendrimers up to generation 4.5 in various buffer solutions. A method was used to minimize the interaction between the capillary and cationic dendrimers. The effects of generation, surface functionality, pH and ionic strength on the hydrodynamic radii of PAMAM dendrimers were investigated. Our results show that TDA can accurately measure the sizes of PAMAM dendrimers with a relatively low standard deviation especially for half generations. It was found that the ionisation of functional groups at various pH values led to a conformational change due to electrostatic repulsion or back-folding of the branches. Furthermore, adding salt to a half-generation dendrimer (G4.5) can lead to a profound size change that is dependent on ionic strength. A 17% increase in the size of the G4.5 dendrimer was observed in a 1 M NaCl solution compared to that in a 0.1 M solution. Compared to dynamic light scattering, TDA is more reliable and tolerant to large particles in the solutions. The findings of this study indicate that TDA could serve as a viable alternative technique for assessing dendrimer size and conformation, as well as studying their binding behavior.