Morphology Transformation of Giant Vesicles by a Polyelectrolyte for an Artificial Model of a Membrane Protein for Endocytosis

The morphology transformation of giant vesicles consisting of amphiphilic poly(methacrylic acid)- block-poly(methyl methacrylate-random-methacrylic acid-random-3-sulfopropyl methacrylate potassium salt), PMAA-b-P(MMA-r-MAA-r-SpMA), was investigated using poly(allylamine hydrochloride) (PAH) as an artificial model of a membrane protein for endocytosis. The polymerization-induced self-assembly of the PMAA-b-P(MMA-r-MAA-r-SpMA) using the nitroxide-mediated photo-controlled/living radical polymerization technique produced spherical vesicles in the absence of PAH, while it provided a fused sheet in its presence at a 1.0 molar ratio of the allylamine hydrochloride unit (AH) to the SpMA unit. It was suggested that the PAH connected the SpMA units by an electrostatic interaction. The fused sheet changed into combined vesicles as the AH/SpMA ratio increased, and at AH/SpMA = 10.0, the morphology was transformed into spherical vesicles much smaller than the original vesicles. The morphology transformation by soaking the original spherical vesicles in a PAH solution demonstrated that the PAH caused the division of the vesicles into much smaller spherical vesicles