To gain an understanding of the toxicity of antimicrobial polymers to human cells, their hemolytic action was investigated using human red blood cells (RBCs). We examined the hemolysis induced by cationic amphiphilic methacrylate random copolymers, which have amino ethyl sidechains as cationic units and either butyl or methyl methacrylate as hydrophobic units. The polymer with 30 mol% butyl sidechains (B30) displayed higher hemolytic toxicity than the polymer with 59 mol% methyl sidechains (M59). B30 also induced faster release of hemoglobin from RBCs than M59. A new theoretical model is proposed based on two consecutive steps to form active polymer species on the RBC membranes, which are associated to RBC lysis. This model takes the all-or-none release of hemoglobin by the rupture of RBCs into account, providing new insight into the polymer-induced hemolysis regarding how individual or collective cells respond to the polymers.Hemolysis induced by antimicrobial methacrylate random copolymers was studied based on the new theoretical model of the all-or-none release of hemoglobin. This model provides insight into the polymer-induced hemolysis regarding how individual or collective cells response to the polymers.

The function and mode of action of curcumin in modulating the formation of lipid raft domains were investigated by microscopic observation using model membranes. Curcumin induces fusion of lipid raft domains at extremely low concentrations through the alteration of the boundary between the ordered and disordered phases.

Semipermeable organic–inorganic hybrid vesicles coated with a siloxane surface were spontaneously formed by simple dispersion of an organoalkoxysilane lipid in water. The hybrid vesicles allow the permeation of hydrophilic small molecules across the membrane without an introduction of a pore-forming protein.

We investigated the interaction of branched polyethyleneimine (PEI) with anionic vesicles formed with 1,2-dioleoyl-sn-glycero-3-phospho-l-serine (DOPS) by spectroscopic measurements and microscopic observations. PEI induced the fusion of the vesicles only over a specific concentration range, which was found to be below the transition of vesicular zeta-potential from negative to positive value. Above the concentration window of membrane fusion, charge inversion of DOPS vesicles due to the further adsorption of PEI onto the surface of vesicle, inhibited the membrane fusion events. The PEI with low molecular weight induced the membrane fusion in a wider range of concentration than high molecular weight PEIs. Our results suggest that the mechanism of PEI interaction with the lipids depends on the molecular weight and stoichiometry of the polycation to negatively charged lipids.Graphical abstractHighlights► Polyethyleneimine (PEI) induced concentration dependent fusion of vesicles. ► Membrane fusion was inhibited by charge inversion of vesicle caused by PEI. ► Action manner of PEI varies depending on the polycation to lipid stoichiometry.

Well-defined hybrid nanodiscs were produced by employing bicelle formation of a binary lipid mixture in water. The resulting nanoparticles have a lipid bilayer coated with ceramic layers, which are formed by the sol–gel reaction among the alkoxysilyl headgroups of the hybrid lipid. The hybrid bicelles displayed significant morphological stability against dry environments and surfactant addition, in stark contrast to conventional phospholipid bicelles.

Well-defined hybrid nanodiscs were produced by employing bicelle formation of a binary lipid mixture in water. The resulting nanoparticles have a lipid bilayer coated with ceramic layers, which are formed by the sol–gel reaction among the alkoxysilyl headgroups of the hybrid lipid. The hybrid bicelles displayed significant morphological stability against dry environments and surfactant addition, in stark contrast to conventional phospholipid bicelles.

Semipermeable organic–inorganic hybrid vesicles coated with a siloxane surface were spontaneously formed by simple dispersion of an organoalkoxysilane lipid in water. The hybrid vesicles allow the permeation of hydrophilic small molecules across the membrane without an introduction of a pore-forming protein.

The function and mode of action of curcumin in modulating the formation of lipid raft domains were investigated by microscopic observation using model membranes. Curcumin induces fusion of lipid raft domains at extremely low concentrations through the alteration of the boundary between the ordered and disordered phases.