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The nonequilibrium dynamics of a fluid lipid membrane under external stimuli is an important issue that spans disciplines such as soft matter, biophysical chemistry, and interface science. This study investigated the dynamic response of lipid vesicles with order–disorder phase separation, which mimics a plasma membrane heterogeneity, to shear flow. Lipid vesicles were immobilized in a microfluidic chamber, and shear-induced nonequilibrium patterns on the membrane surface were observed by an optical microscope. We found that phase-separated membranes exhibit a dissipative structure of stripe patterns along the vortex flow on the membrane surface, and the number of stripes increased with the flow rate. At a high flow rate, the membrane exhibited a stripe-to-wave transition, where striped domains often migrated and the replacement of two different phases happened at vortex centers with time. We obtained a dynamic phase diagram of the shear-induced wave pattern by changing the flow rate, membrane components, and temperature. These findings could provide insight into the dissipative structures of lipid membranes out of equilibrium and flow-mediated mechanotransduction of biological membranes.

Liquid-ordered (Lo)-phase domains, a cholesterol-rich area on lipid bilayers, have attracted significant attention recently because of their relevance to lipid rafts, the formation/collapse of which is associated with various kinds of information exchange through the plasma membrane. Here, we demonstrate that the formation/collapse of Lo-phase domains in cell-sized liposomes, that is, giant unilamellar vesicles (GUVs), can be controlled with bioactive plasmonic nanoparticles and light. The nanoparticles were prepared by surface modification of gold nanorods (AuNRs) using a cationized mutant of high-density lipoprotein (HDL), which is a natural cholesterol transporter. Upon the addition of surface-engineered AuNRs to GUVs with the mixed domains of Lo and liquid-disorder (Ld) phases, the Lo domains collapsed and solid-ordered (So)-phase domains were formed. The reverse phase transition was achieved photothermally, with the AuNRs loaded with cholesterol. During these transitions, the AuNRs appeared to be selectively localized on the less fluidic domain (Lo or So) in the phase-mixed GUVs. These results indicate that the phase transitions occur through the membrane binding of the AuNRs followed by spontaneous/photothermal transfer of cholesterol between the AuNRs and GUVs. Our strategy to develop bioactive AuNRs potentially enables spatiotemporal control of the formation/collapse of lipid rafts in living cells.

Alteration of lipid raft organization manifesting as phase separation is important for cellular processes, such as signaling and trafficking. Such behaviors and dynamics of lipid membranes can be affected by external stimuli including both physical and chemical stimuli. In this study, we focused on osmotic-tension-induced phase separation. The effects of osmotic tension on the phase behaviors of vesicles consisting of dioleoylphosphocholine (DOPC)/dipalmitoylphosphocholine (DPPC)/cholesterol (Chol) were quantitatively studied at different temperatures by fluorescence microscopy. We determined the ternary phase diagrams and found that tension leads to a shift in the miscibility temperature. Cholesterol plays a key role in determining the extent of this shift. In addition, we found that osmotic tension can enhance the line tension. The physicochemical mechanism of osmotic-pressure-induced phase separation is discussed.

Nanomedicine relies on the effective internalization of nanoparticles combined with polymeric nanocarriers into living cells. Thus, exploration of internalization is essential for improving the efficacy of nanoparticle-based strategies in clinical practice. Here, we investigated the physicochemical internalization of gold nanoparticles (AuNPs) conjugated with hydrophobic polyampholytes into cell-sized liposomes at a low but nonfrozen temperature. The hydrophobic polyampholytes localized in the disordered phase of the membrane, and internalization of AuNPs was enhanced in the presence of hydrophobic polyampholytes together with incubation at −3 °C as compared to 25 °C. These results contribute toward a mechanistic understanding for developing a model nanomaterials-driven delivery system based on hydrophobic polyampholytes and low temperature.

Here we show that the ability of oxidized carbon particles to penetrate phospholipid bilayer membrane varies with the particle shapes, chemical functionalities on the particle surface, lipid compositions of the membrane and pH conditions. Among the similar surface charged oxidized carbon particles of spherical (oxidized carbon nanosphere, OCS), tubular (oxidized carbon nanotube, OCT), and sheet (oxidized graphene sheet, OGSh) morphologies, OCS possesses the highest levels of adhesion to lipid bilayer membrane and penetration into the cell-sized liposome. OCS preferably binds better to the disordered lipid bilayer membrane (consisting of 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine) as compared to the ordered membrane (consisting of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine and cholesterol). The process of OCS-induced leak on the membrane is pH responsive and most pronounced under an acidic condition. Covalently decorating the OCS’s surface with poly(ethylene oxide) or (2-aminoethyl)trimethylammonium moieties decreases its ability to interact with the membrane. When used as carriers, OCSs can deliver curcumin into nucleus of A549 human lung cancer and human embryonic kidney cells, in contrast, curcumin molecules delivered by OCTs remain in the cytoplasm. OGShs cannot significantly enter cells and cannot induce noticeable cellular uptake of curcumin.

Although computer simulation and cell culture experiments have shown that elongated spherical particles can be taken up into cells more efficiently than spherical particles, experimental investigation on effects of these different shapes over the particle–membrane association has never been reported. Therefore, whether the higher cellular uptake of an elongated spherical particles is a result of a better particle–membrane association as suggested by some calculation works or a consequence of its influence on other cellular trans-membrane components involved in particle translocation process, cannot be concluded. Here, we study the effect of particle shape on the particle–membrane interaction by monitoring the association between particles of various shapes and lipid bilayer membrane of artificial cell-sized liposomes. Among the three shaped lanthanide-doped NaYF4particles, all with high shape purity and uniformity, similar crystal phase, and surface chemistry, the elongated spherical particle shows the highest level of membrane association, followed by the spherical particle with a similar radius, and the hexagonal prism-shaped particle, respectively. The free energy of membrane curvature calculated based on a membrane indentation induced by a particle association indicates that among the three particle shapes, the elongated spherical particle give the most stable membrane curvature. The elongated spherical particles show the highest cellular uptake into cytosol of human melanoma (A-375) and human liver carcinoma (HepG2) cells when observed through a confocal laser scanning fluorescence microscope. Quantitative study using flow cytometry also gives the same result. The elongated spherical particles also possess the highest cytotoxicity in A-375 and normal skin (WI-38) cell lines, comparing to the other two shaped particles.

We studied the evolution of oil-in-oil (O/O) and water-in-oil (W/O) phospholipid-coated micro-droplets at an oil/water interface. We found that, in both cases, micro-droplets spontaneously transferred from the oil phase to the water phase. O/O micro-droplets transformed into oil-in-water micro-droplets, while W/O micro-droplets led to the formation of liposomes.

A 59-year-old female with depressive tendencies was admitted suffering from hematemesis and abdominal pain, two hours after ingestion of an unknown amount of toilet bowl cleaner (hydrochloric acid, pH 1.0). A barium study 24 days after ingestion revealed rigid narrowing and granulation of the entire stomach. The esophagus and duodenum were normal. The radiographic results were similar to those obtained for linitis plastica carcinoma of the stomach, but biopsy specimens of the stomach revealed no cancer cells. A total gastrectomy was performed about two months after ingestion to relieve the persistent feeling of nausea. Specimens revealed a rigid and thickening lining and a denuded mucosal surface of the stomach. The cut surface of the specimen showed a remarkable fibrous thickening of the submucosal layer. Microscopic examination failed to reveal a normal mucosal layer except in a narrow area of the fornix, and remarkable fibrosis of the submucosal lining was noted. No cancer cells were found. Corrosive gastritis has a linitis plastica appearance with a predilection for the antrum. Radiological examination revealed the very rare manifestion of a rigid narrowing of the whole stomach mimicking linitis plastica type cancer.

It is important to study the effects of lipid oxidation on biological membranes and how this affects physiological functions and causes disease. We investigated the vesicular dynamics of a biomimetic membrane system consisting of an unsaturated phospholipid, 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), and cholesterol (Chol) under oxidative stress. We found that lipid vesicles with a DOPC:Chol ratio of 50:50 are more susceptible to oxidative stress than homogeneous DOPC lipid vesicles.

The optical reflectance of cubic boron nitride (c-BN) was measured for sintered and microcrystalline samples at room temperature in the photon energy range 5-25 eV. Kramers-Kronig analysis was performed to determine the real ?1and imaginary ?2parts of the dielectric function. The spectrum of ?2for sintered c-BN shows peaks at 9.05 eV and 11.7 eV and shoulders at 10 eV, 13.2 eV and 16.7 eV. This spectrum was compared with the one theoretically obtained by Tsay et al.and assignment of the structure was made. The ?2for microcrystalline c-BN has a broad structure with a peak at 11.7 eV.