capillary-based-centrifugal-microfluidic-device-for-size-controllable

Capillary-based Centrifugal Microfluidic Device for Size-controllable Formation of Monodisperse Microdroplets

Here, we demonstrate a simple method for the rapid production of size-controllable, monodisperse, W/O microdroplets using a capillary-based centrifugal ...

bacterial-cell-culture-at-the-single-cell-level-inside-giant-vesicles

Bacterial Cell Culture at the Single-cell Level Inside Giant Vesicles

We developed a method for culturing bacterial cells at the single-cell level inside giant vesicles (GVs). Bacterial cell culture is important for ...

Tokyo Institute of Technology

National Institute of Advanced Industrial Science and Technology (AIST)

High levels of cholesterol have been proposed as a risk factor for Alzheimer's disease (AD). Polymorphism of genes encoding proteins that regulate cholesterol metabolism have also been associated with the frequency of Alzheimer's development. Some studies have shown that cholesterol-lowering drugs reduce the frequency of AD development. The proposed role of cholesterol in AD has been challenged by several studies. In this review, we provide a brief account of the major pieces of evidence in support of and against the possible role of cholesterol in the development of AD, and the methodologies used. We highlight the interactions between cholesterol and amyloid beta (Abeta) and, with the peptide's precursor protein. Drawing from our teams' recent findings, we speculate on how Abeta peptides may influence the fluidity, stability of the membrane, as well as membrane morphological changes.

Cholesterol, lipids, amyloid Beta, and Alzheimer's.

Amyloid beta (Abeta) has been strongly implicated in inducing neurotoxicity in the pathology of Alzheimer's disease (AD). However, the underlying mechanisms remain unknown. In this study, we examined, in real-time, the spatio-temporal changes in individual model membranes induced by the presence of different Abeta-40 molecular assemblies (species). We used cell-sized lipid vesicles to enable the direct observation of these changes. We found three significantly different membrane-transformation pathways. We characterized the biophysical mechanisms behind these transformations in terms of the change in inner vesicle volume and surface area. Oligomeric Abeta exhibited the highest tendency to cause membrane fluctuation and transformations. Interestingly, mature fibrils, which are often considered inert species, also induced profound membrane changes. Furthermore, we imaged the localization of pre-fibrillar species on membranes. The real-time observation of these morphological transformations, which can be missed in a discretised analysis, may help to unlock the mechanisms of AD's Abeta-induced neuro-degeneration.

Real-time observation of model membrane dynamics induced by Alzheimer's amyloid beta.

Alternating amphiphilic multiblock molecules 1-4, involving fluorescent hydrophobic units, were designed as mimics for multipass transmembrane proteins. Fluorescence spectroscopy of 1-4 in liposomal membranes suggested the face-to-face stacking of the hydrophobic units to give folded structures as well as intermolecular assemblies.

Mimicking multipass transmembrane proteins: synthesis, assembly and folding of alternating amphiphilic multiblock molecules in liposomal membranes.

It is important that we understand the physical, chemical, and biological mechanisms that govern the interaction between nanoparticles (NPs) and heterogeneous cellular surfaces because of the possible cytotoxicity of engineered nanomaterials. In this study, we investigated the lateral localization of nano/microparticles within a biomimetic heterogeneous membrane interface using cell-sized two-phase liposomes. We found that lateral heterogeneity in the membrane mediates the partitioning of nano/microparticles in a size-dependent manner: small particles with a diameter of ≤200 nm were localized in an ordered phase, whereas large particles preferred a fluidic disordered phase. This partitioning behavior was verified by temperature-controlled membrane miscibility transition and laser-trapping of associated particles. In terms of the membrane elastic energy, we present a physical model that explains this localization preference of nano/microparticles. The calculated threshold diameter of particles that separates the particle-partitioning phase was 260 nm, which is in close agreement with our observation (200 nm). These findings may lead to a better understanding of the basic mechanisms that underlie the association of nanomaterials within a cell surface.

Size-dependent partitioning of nano/microparticles mediated by membrane lateral heterogeneity.

A multiblock amphiphilic molecule 1, with a tetrameric alternating sequence of hydrophilic and hydrophobic units, adopts a folded structure in a liposomal membrane like a multipass transmembrane protein, and is able to transport alkali metal cations through the membrane. Hill's analysis and conductance measurements, analyzed by the Hille equation, revealed that the tetrameric assembly of 1 forms a 0.53 nm channel allowing for permeation of cations. Since neither 3, bearing flexible hydrophobic units and forming no stacked structures in the membrane, nor 2, a monomeric version of 1, is able to transport cations, the folded conformation of 1 in the membrane is likely essential for realizing its function. Thus, function and hierarchically formed higher-order structures of 1, is strongly correlated with each other like proteins and other biological macromolecules.

Ion permeation by a folded multiblock amphiphilic oligomer achieved by hierarchical construction of self-assembled nanopores.

Amyloid beta (Aβ) peptides, produced through endo-proteolytic cleavage of amyloid precursor protein, are thought to be involved in the death of neural cells in Alzheimer's disease (AD). Although the mechanisms are not fully known, it has been suggested that disruption of cellular activity due to Aβ interactions with the cell membrane may be one of the underlying causes. Here in, we have investigated the interaction between Aβ-42 and biomimetic lipid membranes and the resulting perturbations in the lipid vesicles. We have shown that Aβ oligomeric species localized closer to the membrane surface. Localization of the fibrillar species of Aβ-42, although varied, was not as closely associated with the membrane surface. We have demonstrated that the presence of Aβ-42 leads to an increase in membrane surface area, inducing lipid temporal vesicular transformation. Furthermore, we have unequivocally shown that Aβ-peptides mediate membrane fusion. Although membrane fusion induced by Aβ has been hypothesized/proposed, this is the first time it has been visually captured. This fusion may be one of the mechanisms behind the membrane increase in surface area and the resulting vesicular transformation. We have shown that the longer 'amyloidogenic' isoform causes vesicular transformation more readily, and has a higher membrane fusogenic potential than Aβ-40. Although not core to this study, it is hugely interesting to observe the high agreement between membrane dynamics and the reported amyloidogenicity of the peptides and aggregation species opening up the potential role of vesicular dynamics for profiling and biosensing of Aβ-induced neuro-toxicity.

Membrane fusion and vesicular transformation induced by Alzheimer's amyloid beta.

The interaction of amyloid beta (Aβ) peptide with cell membranes has been shown to be influenced by Aβ conformation, membrane physicochemical properties and lipid composition. However, the effect of cholesterol and its oxidized derivatives, oxysterols, on Aβ-induced neurotoxicity to membranes is not fully understood. We employed here model membranes to investigate the localization of Aβ in membranes and the peptide-induced membrane dynamics in the presence of cholesterol and 7-ketocholesterol (7keto) or 25-hydroxycholesterol (25OH). Our results have indicated that oxysterols rendered membranes more sensitive to Aβ, in contrast to role of cholesterol in inhibiting Aβ/membrane interaction. We have demonstrated that two oxysterols had different impacts owing to distinct positions of the additional oxygen group in their structures. 7keto-containing cell-sized liposomes exhibited a high propensity toward association with Aβ, while 25OH systems were more capable of morphological changes in response to the peptide. Furthermore, we have shown that 42-amino acid Aβ (Aβ-42) pre-fibril species had higher association with membranes, and caused membrane fluctuation faster than 40-residue isoform (Aβ-40). These findings suggest the enhancing effect of oxysterols on interaction of Aβ with membranes and contribute to clarify the harmful impact of cholesterol on Aβ-induced neurotoxicity by means of its oxidation.

The effect of oxysterols on the interaction of Alzheimer's amyloid beta with model membranes.

Cell-sized liposomes are a powerful tool for clarifying physicochemical mechanisms that govern molecular interactions. Herein, budding transformation of membrane domains was induced by amyloid beta peptides. The peptides increased the membrane viscosity as demonstrated by the Brownian motion of membrane domains. These results could aid in understanding the physicochemical mechanism of Alzheimer's disease.

Endo- and exocytic budding transformation of slow-diffusing membrane domains induced by Alzheimer's amyloid beta.

Vesicle formation is a fundamental kinetic process related to the vesicle budding and endocytosis in a cell. In the vesicle formation by artificial means, transformation of lamellar lipid aggregates into spherical architectures is a key process and known to be prompted by e.g. heat, infrared irradiation, and alternating electric field induction. Here we report UV-light-driven formation of vesicles from particles consisting of crumpled phospholipid multilayer membranes involving a photoactive amphiphilic compound composed of 1,4-bis(4-phenylethynyl)benzene (BPEB) units. The particles can readily be prepared from a mixture of these components, which is casted on the glass surface followed by addition of water under ultrasonic radiation. Interestingly, upon irradiation with UV light, micrometer-size vesicles were generated from the particles. Neither infrared light irradiation nor heating prompted the vesicle formation. Taking advantage of the benefits of light, we successfully demonstrated micrometer-scale spatiotemporal control of single vesicle formation. It is also revealed that the BPEB units in the amphiphile are essential for this phenomenon.

Micrometer-size vesicle formation triggered by UV light.

Polyphenols are naturally-occurring compounds, reported to be biologically active, and through their interactions with cell membranes. Although association of the polyphenols with the bilayer has been reported, the detailed mechanism of interaction is not yet well elucidated. We report on spatio-temporal real-time membrane dynamics observed in the presence of polyphenols. Two distinct membrane dynamics, corresponding to the two classes of polyphenols used, were observed. Flavonoids (epi-gallocatechin-3-gallate, gallocatechin, theaflavin and theaflavin-3-gallate) caused lipid membrane aggregation and rigidification. As simple structural modification through opening of the aromatic C-ring into an olefin bond, present in trans-stilbenes (resveratrol and picead), completely changed the membrane properties, increasing fluidity and inducing fluctuation. There were differences in the membrane transformations within the same class of polyphenols. Structure-dependent classification of membrane dynamics may contribute to a better understanding of the physicochemical mechanism involved in the bioactivity of polyphenols. In general, an increase in the number of hydrophilic side chains (galloyl, hydroxyl, glucoside, gallate) increased the reactivity of the polyphenols. Most notable was the difference observed through a simple addition of the gallate group. Unraveling the importance of these polyphenols, at a functional group level further opens the key to tailored design of bioactive compounds as potential drug candidates.

Structure-dependent interactions of polyphenols with a biomimetic membrane system.

We report an easy-to-use generation method of biologically compatible monodisperse water-in-oil microdroplets using a glass-capillary-based microfluidic device in a tabletop mini-centrifuge. This device does not require complicated microfabrication; furthermore, only a small sample volume is required in experiments. Therefore, we believe that this method will assist biochemical and cell-biological experiments.

Generation of monodisperse cell-sized microdroplets using a centrifuge-based axisymmetric co-flowing microfluidic device.

We report a centrifugal microfluidic method, droplet-shooting and size-filtration (DSSF), for the production of cell-sized liposomes with controlled lipid compositions. This involves the generation of large and small droplets from the tip of a glass capillary and the selective transfer of small droplets through an oil-water interface, thus resulting in the generation of cell-sized liposomes. We demonstrate control of the microdomain formation as well as the formation of asymmetric lipid bilayer liposomes of uniform size by the control of lipid composition. The DSSF method involves simple microfluidics and is easy to use. In addition, only a small volume (0.5-2 μL) of sample solution is required for the formation of hundreds of cell-sized liposomes. We believe that this method can be applied to generate cell-sized liposomes for a wide variety of uses, such as the construction of artificial cell-like systems.

Droplet-Shooting and Size-Filtration (DSSF) Method for Synthesis of Cell-Sized Liposomes with Controlled Lipid Compositions.

We used a cell-sized model system, giant liposomes, to investigate the interaction between lipid membranes and surfactants, and the membrane transformation during the solubilization process was captured in real time. We found that there are four distinct dynamics in surfactant-induced membrane deformation: an episodic increase in the membrane area prior to pore-forming associated shrinkage (Dynamics A), fission into many small liposomes (Dynamics B), the formation of multilamellar vesicles and peeling (Dynamics C), and bursting (Dynamics D). Classification of the diversity of membrane dynamics may contribute to a better understanding of the physicochemical mechanism of membrane solubilization induced by various surfactants.

ArticleTotal : 2	Year
Publication title Cited by 9	2016
Publication title Cited by 1	2019

Article	Year
Cholesterol, lipids, amyloid Beta, and Alzheimer's. Current Alzheimer research\| PubMed ID: 19715550	2010
Real-time observation of model membrane dynamics induced by Alzheimer's amyloid beta. Biophysical chemistry\| PubMed ID: 20060637	2010
Mimicking multipass transmembrane proteins: synthesis, assembly and folding of alternating amphiphilic multiblock molecules in liposomal membranes. Chemical communications (Cambridge, England)\| PubMed ID: 20848036	2011
Size-dependent partitioning of nano/microparticles mediated by membrane lateral heterogeneity. Journal of the American Chemical Society\| PubMed ID: 22873713	2012
Ion permeation by a folded multiblock amphiphilic oligomer achieved by hierarchical construction of self-assembled nanopores. Journal of the American Chemical Society\| PubMed ID: 23145887	2012
Membrane fusion and vesicular transformation induced by Alzheimer's amyloid beta. Biochimica et biophysica acta\| PubMed ID: 23357358	2013
The effect of oxysterols on the interaction of Alzheimer's amyloid beta with model membranes. Biochimica et biophysica acta\| PubMed ID: 23800382	2013
Endo- and exocytic budding transformation of slow-diffusing membrane domains induced by Alzheimer's amyloid beta. Physical chemistry chemical physics : PCCP\| PubMed ID: 24676499	2014
Micrometer-size vesicle formation triggered by UV light. Langmuir : the ACS journal of surfaces and colloids\| PubMed ID: 24898450	2014
Structure-dependent interactions of polyphenols with a biomimetic membrane system. Biochimica et biophysica acta\| PubMed ID: 25016053	2014
Generation of monodisperse cell-sized microdroplets using a centrifuge-based axisymmetric co-flowing microfluidic device. Journal of bioscience and bioengineering\| PubMed ID: 25454697	2015
Droplet-Shooting and Size-Filtration (DSSF) Method for Synthesis of Cell-Sized Liposomes with Controlled Lipid Compositions. Chembiochem : a European journal of chemical biology\| PubMed ID: 26212462	2015
Physicochemical Profiling of Surfactant-Induced Membrane Dynamics in a Cell-Sized Liposome. The journal of physical chemistry letters\| PubMed ID: 26285862	2012

Masamune Morita

Biography

JoVE Journal Publications

Other Publications