Effect of dendrimer generation on the assembly and mechanical properties of DNA/phosphorus dendrimer multilayer microcapsules

We report the preparation, characterization and mechanical properties of DNA/phosphorus dendrimer multilayer microcapsules. The shells of these microcapsules are composed by alternating DNA and positively charged dendrimer Gn(NH+Et2Cl-)(m) (n = 1, 2, 3, 4; m = 12, 24, 48, 96). The same multilayers were constructed on planar support to examine their layer- by- layer growth and to determine the multilayer thickness. Surface plasmon resonance spectroscopy (SPR) showed regular linear growth of the multilayer film after the first dendrimer layer. We probe the mechanical properties of these DNA/dendrimer microcapsules by measuring force- deformation curves with the atomic force microscope (AFM). The experiment suggests that they are softer than microcapsules assembled from linear flexible polyelectrolytes (PE) studied before. The stiffness of the capsules increases with the generation of used dendrimer. This reflects the change in the multilayer thickness, but not the changes in structure of surface DNA/dendrimer complexes, which almost likely remains similar for all dendrimer generations.