Surface roughness as rupture control factor of lipid vesicles

Liposomes or lipid vesicles are self-closed structures formed by one or several concentric lipid bilayers with an aqueous phase inside, which may incorporate almost any molecule, namely proteins, hormones, enzymes, antibiotics, anticancer agents, antifungical agents, gene transfer agents, DNA, and whole viruses. Scientific evidences prove that unprotected liposomes containing drugs are easily released from the endoplasmic reticulum of the cell. To increase the vesicles lifetime and to activate a controlled drug release with an external stimulus, the vesicles immobilization on a surface and the factors which create conditions to the liposome rupture have to be analyzed. A number of studies have identified some of the critical stages of vesicle adsorption (adhesion), fusion, deformation, rupture, and spreading of the lipid bilayer. Nevertheless, the formation mechanisms of well-controlled continuous supported bilayers or adsorption of whole liposomes are still not fully understood. As yet it was demonstrated that a controlled adsorption of vesicles containing a small fraction of charged lipids occurs without rupture and their subsequent embedding in polyelectrolyte multilayer (PEM) films, meaning vesicles may be immobilized in an intact or slightly deformed state, which can act as drug reservoirs. Moreover, depending on the nature of the physicochemical conditions of the vesicle solution and the substrate surface, a flat lipid bilayer can be formed, known as supported lipid bilayers, which can incorporate membrane proteins and keep the native dynamics of the lipid bilayer mimicking a biological membrane. In this study, a layer of 1,2-dipalmitoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (sodium salt) (DPPG) liposomes adsorbed onto PEMs cushions based on poly(ethylenimine) (PEI), poly(sodium 4-styrenesulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) polyelectrolytes was analyzed by atomic force microscopy (AFM) technique in non-contact mode and quartz crystal microbalance (QCM).Sequential heterostructures of Si/PEI(PSS/PAH)4 and Si/PAH, also designated cushions, were prepared onto silicon substrates using the layer-by-layer (LbL) technique with polyelectrolyte solutions of PEI, PSS and PAH of monomeric concentrations of 0.01M. Topographic images of 1×1μm2 area of Si/PAH/DPPG (Figure 1 a), and Si/PEI(PSS/PAH)4/DPPG (Figure 1 b) LbL films were acquired by AFM. The root mean square roughness (RMS) calculated from topographies data are listed in table I. As shown, when a DPPG layer is adsorbed onto Si/PAH the RMS keeps an approximately equal value meaning that the liposome disrupted and spread onto the surface forming a planar lipid bilayer. But when a DPPG layer is adsorbed onto Si/PEI(PSS/PAH)4 the RMS value doubled, indicating that the structural integrity of the liposomes is maintained, even though there has been any deformation during adsorption. The adsorbed amount of the two PEMs and DPPG-liposomes layers was measured using a QCM and is displayed in table I. The DPPG adsorbed amount obtained on the PAH cushion was approximately equal to a planar lipid bilayer, while the adsorption onto PEI(PSS/PAH)4 was higher than the predicted for a planar lipid bilayer. This behavior suggests that the DPPG liposomes on the second PEM remained intact during adsorption. Both confirm the AFM results. Therefore we conclude that the initial roughness of the surface is a primordial factor to determine the adsorption or not of intact vesicles.The authors acknowledge the “Fundação para a Ciência e Tecnologia” (FCT-MEC) by the post-graduate scholarship SFRH/BD/62229/2009 and the “Plurianual” funding.

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Ion channels ofFasciola hepaticaincorporated into planar lipid bilayers

Parasitology ◽

10.1017/s0031182003004232 ◽

2004 ◽

Vol 128 (1) ◽

pp. 83-89 ◽

Cited By ~ 4

Author(s):

J. H. JANG ◽

S. D. KIM ◽

J. B. PARK ◽

S. J. HONG ◽

P. D. RYU

Keyword(s):

Ion Channels ◽

Lipid Bilayer ◽

Lipid Bilayers ◽

Fasciola Hepatica ◽

State Probability ◽

Planar Lipid Bilayer ◽

Single Channels ◽

Permeable Channel ◽

Important Target ◽

Large Conductance Channel

Ion channels are important target sites of anthelmintics, but little is known about those inFasciola hepatica. In this work, we applied a planar lipid bilayer technique to characterize the properties of single ion channels inF. hepatica. Under a 200/40 mMKCl gradient, a large conductance channel of 251 pS was observed in 18% of the membranes studied. The channel was selective to K+over Cl−with a permeability ratio of K+to Cl−(PK/PCl) of 4·9. Open state probability (Po) of the channel was less than 0·5 and dependent on voltage (−60~+40 mV) and Ca2+(~100 μM). The other two types of single channels observed in 11 and 5% of membranes, respectively, were a K+-permeable channel of 80 pS (PK/PCl=4·6) and a Cl−-permeable channel of 64 pS (PK/PCl=0·058). Open state probability of both channels showed little voltage dependence. The results indicate that distinct single channels of 60~251 pS are present in relative abundance and, in addition, that the planar lipid bilayer technique can be a useful tool for the study of single ion channels inF. hepatica.

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DNA-Encircled Lipid Bilayers

10.1101/285957 ◽

2018 ◽

Author(s):

Katarina Iric ◽

Madhumalar Subramanian ◽

Jana Oertel ◽

Nayan P. Agarwal ◽

Michael Matthies ◽

...

Keyword(s):

Membrane Proteins ◽

Lipid Bilayer ◽

Lipid Bilayers ◽

Protein Interactions ◽

Protein Function ◽

Dna Nanotechnology ◽

Lipid Vesicles ◽

Associated Proteins

ABSTRACTLipid bilayers and lipid-associated proteins play a crucial role in biology. As in vivo studies and manipulation are inherently difficult, several membrane-mimetic systems have been developed to enable investigation of lipidic phases, lipid-protein interactions, membrane protein function and membrane structure in vitro. Controlling the size and shape, or site-specific functionalization is, however, difficult to achieve with established membrane mimetics based on membrane scaffolding proteins, polymers or peptides. In this work, we describe a route to leverage the unique programmability of DNA nanotechnology and create DNA-encircled bilayers (DEBs), which are made of multiple copies of an alkylated oligonucleotide hybridized to a single-stranded minicircle. To stabilize the hydrophobic rim of the lipid bilayer, and to prevent formation of lipid vesicles, we introduced up to 2 alkyl chains per helical that point to the inside of the toroidal DNA ring and interact with the hydrophobic side chains of the encapsulated lipid bilayer. The DEB approach described herein provides unprecedented control of size, and allows the orthogonal functionalizations and arrangement of engineered membrane nanoparticles and will become a valuable tool for biophysical investigation of lipid phases and lipid-associated proteins and complexes including structure determination of membrane proteins and pharmacological screenings of membrane proteins.

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Substrate-induced electrostatic potential varies composition of supported lipid bilayer containing anionic lipid

Japanese Journal of Applied Physics ◽

10.35848/1347-4065/ac3fcc ◽

2021 ◽

Author(s):

Ryugo TERO ◽

Natsumi Kobayashi

Keyword(s):

Lipid Bilayer ◽

Lipid Bilayers ◽

Electrostatic Potential ◽

Lipid Composition ◽

Neutral Lipids ◽

Substrate Surface ◽

Solid Substrate ◽

Model Systems ◽

Artificial System ◽

Anionic Lipid

Abstract Supported lipid bilayers (SLBs) are artificial lipid bilayers at solid-liquid interfaces applied as cell membrane model systems. An advantage of the artificial system is that the lipid composition can be controlled arbitrarily. On the other hand, the SLB formation process and its efficiency are affected by the properties of the solid substrate surface. In this study, we investigated the effect of the electrostatic interaction between the negatively charged SiO2/Si substrate surface and the lipid bilayer membrane on the composition of binary SLBs comprising anionic and neutral lipids. The phase transition temperature and the area fraction of lipid domains of SLB were evaluated by fluorescence microscopy and the fluorescence recovery after photobleaching. The neutral lipid was preferably included in SLB, but the anionic lipid ratio increased with Ca2+ concentration during the SLB formation. The lipid composition in SLB can be controlled by modulating the substrate-induced electrostatic potential.

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Thermodynamic Modeling of Solvent-Assisted Lipid Bilayer Formation Process

Micromachines ◽

10.3390/mi13010134 ◽

2022 ◽

Vol 13 (1) ◽

pp. 134

Author(s):

Hongmei Xu ◽

Hyunhyuk Tae ◽

Nam-Joon Cho ◽

Changjin Huang ◽

K. Jimmy Hsia

Keyword(s):

Lipid Bilayer ◽

Lipid Bilayers ◽

Thermodynamic Modeling ◽

Formation Process ◽

Lipid Membrane ◽

Substrate Surface ◽

Experimental Conditions ◽

Wide Range ◽

Underlying Mechanisms ◽

Compositional Diversity

The solvent-assisted lipid bilayer (SALB) formation method provides a simple and efficient, microfluidic-based strategy to fabricate supported lipid bilayers (SLBs) with rich compositional diversity on a wide range of solid supports. While various studies have been performed to characterize SLBs formed using the SALB method, relatively limited work has been carried out to understand the underlying mechanisms of SALB formation under various experimental conditions. Through thermodynamic modeling, we studied the experimental parameters that affect the SALB formation process, including substrate surface properties, initial lipid concentration, and temperature. It was found that all the parameters are critically important to successfully form high-quality SLBs. The model also helps to identify the range of parameter space within which conformal, homogeneous SLBs can be fabricated, and provides mechanistic guidance to optimize experimental conditions for lipid membrane-related applications.

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Stripping Material from a Supported Lipid Bilayer with High Speed Buffer Flow

American Journal of Undergraduate Research ◽

10.33697/ajur.2020.027 ◽

2020 ◽

Vol 17 (3) ◽

pp. 51-59

Author(s):

Michael Ornstead ◽

Ruth Hunter ◽

Mason Valentine ◽

Cameron Cooper ◽

Stephen Smith ◽

...

Keyword(s):

Lipid Bilayer ◽

Lipid Bilayers ◽

Microfluidic Device ◽

High Speed ◽

Membrane Vesicle ◽

Microfluidic Channel ◽

Lipid Vesicles ◽

Membrane Properties ◽

Supported Lipid Bilayer ◽

Glass Coverslip

A microfluidic device was created and used to demonstrate that supported lipid bilayers can be deposited on clean glass slides and removed using high velocity buffer flow (1-4 m/s linear velocity). This was accomplished by forcing the flow through a microfluidic channel covering an annealed glass coverslip bearing a supported lipid bilayer (SLB). The removal of bilayer material was monitored via fluorescence microscopy, and two basic regimes were observed: at 1-2 m/s smaller areas were stripped, while at 3-4 m/s larger areas were stripped. SLB removal was verified by two means. First, lipid vesicles labeled with a different fluorescent dye were added to the device and filled in holes left by the removal of the original SLB, allowing stripping to be verified visually. Second, the solutions obtained from stripping were concentrated and the fluorescence in the concentrates was measured. The ability to strip SLB from glass provides a relatively gentle method of creating spatially inhomogeneous SLB, which could be a useful tool in the continued investigation of membrane properties and components. KEYWORDS: Supported Lipid Bilayer; Membrane Vesicle; Microfluidic Device

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Water Pores in Planar Lipid Bilayers at Fast and Slow Rise of Transmembrane Voltage

Membranes ◽

10.3390/membranes11040263 ◽

2021 ◽

Vol 11 (4) ◽

pp. 263

Author(s):

Alenka Maček Lebar ◽

Damijan Miklavčič ◽

Malgorzata Kotulska ◽

Peter Kramar

Keyword(s):

Lipid Bilayer ◽

Lipid Bilayers ◽

Barrier Properties ◽

Model Systems ◽

Planar Lipid Bilayer ◽

Planar Lipid Bilayers ◽

Membrane Rupture ◽

Transmembrane Voltage ◽

Slow Rise ◽

The Moment

Basic understanding of the barrier properties of biological membranes can be obtained by studying model systems, such as planar lipid bilayers. Here, we study water pores in planar lipid bilayers in the presence of transmembrane voltage. Planar lipid bilayers were exposed to fast and slow linearly increasing voltage and current signals. We measured the capacitance, breakdown voltage, and rupture time of planar lipid bilayers composed of 1-pamitoyl 2-oleoyl phosphatidylcholine (POPC), 1-pamitoyl 2-oleoyl phosphatidylserine (POPS), and a mixture of both lipids in a 1:1 ratio. Based on the measurements, we evaluated the change in the capacitance of the planar lipid bilayer corresponding to water pores, the radius of water pores at membrane rupture, and the fraction of the area of the planar lipid bilayer occupied by water pores.planar lipid bilayer capacitance, which corresponds to water pores, water pore radius at the membrane rupture, and a fraction of the planar lipid bilayer area occupied by water pores. The estimated pore radii determining the rupture of the planar lipid bilayer upon fast build-up of transmembrane voltage are 0.101 nm, 0.110 nm, and 0.106 nm for membranes composed of POPC, POPS, and POPC:POPS, respectively. The fraction of the surface occupied by water pores at the moment of rupture of the planar lipid bilayer The fraction of an area that is occupied by water pores at the moment of planar lipid bilayer rupture is in the range of 0.1–1.8%.

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Tentative Peptide‒Lipid Bilayer Models Elucidating Molecular Behaviors and Interactions Driving Passive Cellular Uptake of Collagen-Derived Small Peptides

Molecules ◽

10.3390/molecules26030710 ◽

2021 ◽

Vol 26 (3) ◽

pp. 710

Author(s):

Pathomwat Wongrattanakamon ◽

Wipawadee Yooin ◽

Busaban Sirithunyalug ◽

Piyarat Nimmanpipug ◽

Supat Jiranusornkul

Keyword(s):

Lipid Bilayer ◽

Lipid Bilayers ◽

Mean Square Displacement ◽

Dynamics Simulation ◽

Coordinate Frame ◽

Mean Square ◽

Binding Modes ◽

Small Peptides ◽

Collagen Peptides ◽

Electron Density Profiles

Collagen contains hydroxyproline (Hyp), which is a unique amino acid. Three collagen-derived small peptides (Gly-Pro-Hyp, Pro-Hyp, and Gly-Hyp) interacting across a lipid bilayer (POPC model membrane) for cellular uptakes of these collagen-derived small peptides were studied using accelerated molecular dynamics simulation. The ligands were investigated for their binding modes, hydrogen bonds in each coordinate frame, and mean square displacement (MSD) in the Z direction. The lipid bilayers were evaluated for mass and electron density profiles of the lipid molecules, surface area of the head groups, and root mean square deviation (RMSD). The simulation results show that hydrogen bonding between the small collagen peptides and plasma membrane plays a significant role in their internalization. The translocation of the small collagen peptides across the cell membranes was shown. Pro-Hyp laterally condensed the membrane, resulting in an increase in the bilayer thickness and rigidity. Perception regarding molecular behaviors of collagen-derived peptides within the cell membrane, including their interactions, provides the novel design of specific bioactive collagen peptides for their applications.

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