Cellular membranes serve as a permeability barrier that large

water-soluble charged nanoparticles (macro-ions) are unable to

penetrate by simple diffusion. Intra-and extracellular transport of

such macro-ions is still possible by a dynamic membrane shape

transformation that involves a change of membrane curvature

(encapsulation) (Ha¨gerstrand et al., 1999). For example, clathrin-

mediated endocytosis controls the curvature of the coated transport

vesicles. Membrane vesiculation can also be induced by self-

assembly of membrane-adhering choleratoxin molecules (Schara

et al., 2009).