Hollow nanocapsules prepared through stabilization of polymer vesicles formed from head–tail type polycations by introducing cross-linkages

Hollow nanocapsules were prepared through introduction of cross-linkages into polymer vesicles formed from head–tail type polycations composed of polyamidoamine dendron heads and poly(L-lysine) (PLL) tails. The PLL tails were cross-linked by reaction of lysine residues with oligo(ethylene glycol) bearing epoxy groups at both ends. Successful fixing of hollow structures by crosslinking was confirmed by dynamic light scattering (DLS) measurements and transmission electron microscopy observation. The pH-dependent properties of the nanocapsules were evaluated by DLS, ζ-potential, fluorescence and circular dichroism measurements. The increase in the size (i.e. swelling) of the nanocapsules resulted from collapse of the helical conformation of PLL tails in response to decreased pH or addition of urea, indicating that the conformation of PLL tails was a crucial factor in determining the size of the nanocapsules.