Enhanced permeability of Rhodamine B into bilayers comprised of amphiphilic random block copolymers by incorporation of ionic segments in the hydrophobic chains

Abstract

The permeability of Rhodamine B (Rh) into bilayers comprised of amphiphilic block copolymers was explored using ionic segments incorporated in the hydrophobic chains. The amphiphilic block copolymer consisting of a hydrophilic poly(methacrylic acid) block and a hydrophobic poly(methyl methacrylate-random-methacrylic acid) block containing 0.2 mol% units of the 3-sulfopropyl methacrylate potassium salt (SpMA) produced giant vesicles by photopolymerizationinduced self-assembly in an aqueous methanol solution. The spherical vesicles were transformed into films as the SpMA ratio increased. The SpMA units incorporated in the hydrophobic chains enhanced the Rh permeability into the bilayer, whereas the vesicles without SpMA units captured no Rh molecules. However, the Rh was released from the hydrophobic phases in the isolation process of the bilayers by repeated sedimentation-redispersion. The permeability enhancement was attributed to the pore formation in the bilayers by the capture and release of the Rh by the SpMA units in the hydrophobic phases.

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

“…The resulting diblock copolymers are listed in Table 1. The monomer conversions and the molar ratio of the unit in the P(MMA-r-MAA-r-SpMA) block were determined by 1 H NMR [18]. The copolymers contained the MMA units of 0.84~0.85 in the hydrophobic P(MMA-r-MAA-r-SpMA) block.…”

“…The precipitates were isolated by decantation and dried in air to subject to FE-SEM. For a control experiment, the vesicles (Dn = 1.70 µm, Dw/Dn = 1.56) consisting of PMAA 216 -b-P(MMA 0.829 -r-MAA 0.171 ) 318 [18] were subjected to the soaking.…”

“…Giant vesicles consisting of an amphiphilic poly (methacrylic acid)-block-poly (methyl methacrylate-randommethacrylic acid) diblock copolymer, PMAA-b-P(MMA-r-MAA), are an artificial model of the biomembrane for cells and organelles based on the similarities in their structure [15], stimuli-responsive behavior [16,17], and membrane permeability [18]. Various morphologies have been found for the diblock copolymer depending on the block length [19,20], types of the monomer units [21][22][23], insertion of the segment copolymer [24], and conditions of the vesicle preparation [25] by the polymerization-induced selfassembly using the nitroxide-mediated photo controlled/living radical polymerization (photo NMP) technique [26].…”

“…The morphologies include spherical vesicles [15], the elliptical [25], worm-like [19,20,27], cup-like [27], key-shaped [19], villus-like [28], and anastomosed tubular networks continuing with a fenestrated sheet [17]. Furthermore, the vesicles supporting the ionic monomer units of the 3-sulfopropyl methacrylate potassium salt (SpMA) on the hydrophobic block enhanced the permeability of the vesicles for ionic compounds, such as Rhodamine B, based on the electrostatic interaction in the hydrophobic phase [18]. This paper describes the morphology changes in the vesicles consisting of PMAA-b-P(MMA-r-MAA-r-SpMA) using poly (allylamine hydrochloride) (PAH) as an artificial model of caveolin-1.…”

Morphological stability of worm-like vesicles consisting of amphiphilic diblock copolymer against external stress

“…[24] These morphologies were determined by the block length and molar ratio of the monomer unit in the diblock copolymer. The copolymer also provided new models relating to the membrane permeability, [25] budding separation during endocytosis, [26] and sterol intercalation. [27] It is important to investigate the morphological stability of the vesicles against the external stress in order to elucidate the biomembranes of the bacteria and organelles from a morphological aspect.…”