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Huang Y, Chandran Suja V, Yang M, Malkovskiy AV, Tandon A, Colom A, Qin J, Fuller GG. Interfacial stresses on droplet interface bilayers using two photon fluorescence lifetime imaging microscopy. J Colloid Interface Sci 2024; 653:1196-1204. [PMID: 37793246 DOI: 10.1016/j.jcis.2023.09.092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2023] [Revised: 09/06/2023] [Accepted: 09/14/2023] [Indexed: 10/06/2023]
Abstract
HYPOTHESIS Response of lipid bilayers to external mechanical stimuli is an active area of research with implications for fundamental and synthetic cell biology. Developing novel tools for systematically imposing mechanical strains and non-invasively mapping out interfacial (membrane) stress distributions on lipid bilayers can accelerate research in this field. EXPERIMENTS We report a miniature platform to manipulate model cell membranes in the form of droplet interface bilayers (DIBs), and non-invasively measure spatio-temporally resolved interfacial stresses using two photon fluorescence lifetime imaging of an interfacially active molecular flipper (Flipper-TR). We established the effectiveness of the developed framework by investigating interfacial stresses accompanying three key processes associated with DIBs: thin film drainage between lipid monolayer coated droplets, bilayer formation, and bilayer separation. FINDINGS The measurements revealed fundamental aspects of DIBs including the existence of a radially decaying interfacial stress distribution post bilayer formation, and the simultaneous build up and decay of stress respectively at the bilayer corner and center during bilayer separation. Finally, utilizing interfacial rheology measurements and MD simulations, we also reveal that the tested molecular flipper is sensitive to membrane fluidity that changes with interfacial stress - expanding the scientific understanding of how molecular flippers sense stress.
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Affiliation(s)
- Yaoqi Huang
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA
| | - Vineeth Chandran Suja
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA; School of Engineering and Applied Sciences, Harvard University, MA - 02138, USA.
| | - Menghao Yang
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA
| | - Andrey V Malkovskiy
- Carnegie Institute for Science, Department of Plant Biology, Stanford CA 94305, USA
| | - Arnuv Tandon
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA
| | - Adai Colom
- Biofisika Institute (CSIC, UPV/EHU), 48940 Leioa, Spain; Department of Biochemistry and Molecular Biology, Faculty of Science and Technology, Campus Universitario, University of the Basque Country (UPV/EHU), 48940 Leioa, Spain
| | - Jian Qin
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA
| | - Gerald G Fuller
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA.
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2
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Andersson J, Kleinheinz D, Ramach U, Kiesenhofer N, Ashenden A, Valtiner M, Holt S, Koeper I, Schmidpeter PAM, Knoll W. Native Function of the Bacterial Ion Channel SthK in a Sparsely Tethered Lipid Bilayer Membrane Architecture. J Phys Chem B 2023; 127:3641-3650. [PMID: 37072125 PMCID: PMC10150356 DOI: 10.1021/acs.jpcb.2c07252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/20/2023]
Abstract
The plasma membrane protects the interiors of cells from their surroundings and also plays a critical role in communication, sensing, and nutrient import. As a result, the cell membrane and its constituents are among the most important drug targets. Studying the cell membrane and the processes it facilitates is therefore crucial, but it is a highly complex environment that is difficult to access experimentally. Various model membrane systems have been developed to provide an environment in which membrane proteins can be studied in isolation. Among them, tethered bilayer lipid membranes (tBLMs) are a promising model system providing a solvent-free membrane environment which can be prepared by self-assembly, is resistant to mechanical disturbances and has a high electrical resistance. tBLMs are therefore uniquely suitable to study ion channels and charge transport processes. However, ion channels are often large, complex, multimeric structures and their function requires a particular lipid environment. In this paper, we show that SthK, a bacterial cyclic nucleotide gated (CNG) ion channel that is strongly dependent on the surrounding lipid composition, functions normally when embedded into a sparsely tethered lipid bilayer. As SthK has been very well characterized in terms of structure and function, it is well-suited to demonstrate the utility of tethered membrane systems. A model membrane system suitable for studying CNG ion channels would be useful, as this type of ion channel performs a wide range of physiological functions in bacteria, plants, and mammals and is therefore of fundamental scientific interest as well as being highly relevant to medicine.
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Affiliation(s)
- Jakob Andersson
- Austrian Institute of Technology GmbH, Giefinggasse 4, 1210 Vienna, Austria
| | - David Kleinheinz
- Austrian Institute of Technology GmbH, Giefinggasse 4, 1210 Vienna, Austria
| | - Ulrich Ramach
- Technische Universität Wien, Wiedner Hauptstr. 8-10/134, 1040 Wien, Austria
- CEST Kompetenzzentrum für Oberflächentechnologie, Viktor Kaplan-Straße 2, 2700 Wiener Neustadt, Austria
| | | | - Alex Ashenden
- Flinders University of South Australia, Bedford Park SA, 5042 Adelaide, Australia
| | - Markus Valtiner
- Technische Universität Wien, Wiedner Hauptstr. 8-10/134, 1040 Wien, Austria
- CEST Kompetenzzentrum für Oberflächentechnologie, Viktor Kaplan-Straße 2, 2700 Wiener Neustadt, Austria
| | - Stephen Holt
- Australian Nuclear Science and Technology Organization, New Illawarra Rd, Lucas Heights, NSW 2234, Australia
| | - Ingo Koeper
- Flinders University of South Australia, Bedford Park SA, 5042 Adelaide, Australia
| | - Philipp A M Schmidpeter
- Weill Cornell Medicine, Department of Anesthesiology, 1300 York Avenue, New York, New York 10065, United States
| | - Wolfgang Knoll
- Austrian Institute of Technology GmbH, Giefinggasse 4, 1210 Vienna, Austria
- Danube Private University, Steiner Landstraße 124, 3500 Krems an der Donau, Austria
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Insight into the Impact of Oxidative Stress on the Barrier Properties of Lipid Bilayer Models. Int J Mol Sci 2022; 23:ijms23115932. [PMID: 35682621 PMCID: PMC9180489 DOI: 10.3390/ijms23115932] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 05/20/2022] [Accepted: 05/21/2022] [Indexed: 12/10/2022] Open
Abstract
As a new field of oxidative stress-based therapy, cold physical plasma is a promising tool for several biomedical applications due to its potential to create a broad diversity of reactive oxygen and nitrogen species (RONS). Although proposed, the impact of plasma-derived RONS on the cell membrane lipids and properties is not fully understood. For this purpose, the changes in the lipid bilayer functionality under oxidative stress generated by an argon plasma jet (kINPen) were investigated by electrochemical techniques. In addition, liquid chromatography-tandem mass spectrometry was employed to analyze the plasma-induced modifications on the model lipids. Various asymmetric bilayers mimicking the structure and properties of the erythrocyte cell membrane were transferred onto a gold electrode surface by Langmuir-Blodgett/Langmuir-Schaefer deposition techniques. A strong impact of cholesterol on membrane permeabilization by plasma-derived species was revealed. Moreover, the maintenance of the barrier properties is influenced by the chemical composition of the head group. Mainly the head group size and its hydrogen bonding capacities are relevant, and phosphatidylcholines are significantly more susceptible than phosphatidylserines and other lipid classes, underlining the high relevance of this lipid class in membrane dynamics and cell physiology.
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Cao Y, Klein J. Lipids and lipid mixtures in boundary layers: From hydration lubrication to osteoarthritis. Curr Opin Colloid Interface Sci 2022. [DOI: 10.1016/j.cocis.2021.101559] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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5
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Boundary lubrication with aqueous solutions of silicone-based amphiphilic block copolymer aggregates: effect of concentration. Polym J 2021. [DOI: 10.1038/s41428-021-00515-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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6
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Nakhaei P, Margiana R, Bokov DO, Abdelbasset WK, Jadidi Kouhbanani MA, Varma RS, Marofi F, Jarahian M, Beheshtkhoo N. Liposomes: Structure, Biomedical Applications, and Stability Parameters With Emphasis on Cholesterol. Front Bioeng Biotechnol 2021; 9:705886. [PMID: 34568298 PMCID: PMC8459376 DOI: 10.3389/fbioe.2021.705886] [Citation(s) in RCA: 189] [Impact Index Per Article: 63.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Accepted: 08/09/2021] [Indexed: 12/12/2022] Open
Abstract
Liposomes are essentially a subtype of nanoparticles comprising a hydrophobic tail and a hydrophilic head constituting a phospholipid membrane. The spherical or multilayered spherical structures of liposomes are highly rich in lipid contents with numerous criteria for their classification, including structural features, structural parameters, and size, synthesis methods, preparation, and drug loading. Despite various liposomal applications, such as drug, vaccine/gene delivery, biosensors fabrication, diagnosis, and food products applications, their use encounters many limitations due to physico-chemical instability as their stability is vigorously affected by the constituting ingredients wherein cholesterol performs a vital role in the stability of the liposomal membrane. It has well established that cholesterol exerts its impact by controlling fluidity, permeability, membrane strength, elasticity and stiffness, transition temperature (Tm), drug retention, phospholipid packing, and plasma stability. Although the undetermined optimum amount of cholesterol for preparing a stable and controlled release vehicle has been the downside, but researchers are still focused on cholesterol as a promising material for the stability of liposomes necessitating explanation for the stability promotion of liposomes. Herein, the prior art pertaining to the liposomal appliances, especially for drug delivery in cancer therapy, and their stability emphasizing the roles of cholesterol.
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Affiliation(s)
- Pooria Nakhaei
- School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Ria Margiana
- Department of Anatomy, Faculty of Medicine, Universitas Indonesia, Depok, Indonesia
- Cipto Mangunkusumo Hospital, The National Referral Hospital, Central Jakarta, Indonesia
- Master’s Programme Biomedical Sciences, Faculty of Medicine, Universitas Indonesia, Depok, Indonesia
| | - Dmitry O. Bokov
- Institute of Pharmacy, Sechenov First Moscow State Medical University, Moscow, Russia
- Laboratory of Food Chemistry, Federal Research Center of Nutrition, Biotechnology, and Food Safety, Moscow, Russia
| | - Walid Kamal Abdelbasset
- Department of Health and Rehabilitation Sciences, College of Applied Medical Sciences, Prince Sattam Bin Abdulaziz University, Al Kharj, Saudi Arabia
- Department of Physical Therapy, Kasr Al-Aini Hospital, Cairo University, Giza, Egypt
| | - Mohammad Amin Jadidi Kouhbanani
- Department of Medical Nanotechnology, School of Advanced Medical Sciences and Technologies, Shiraz University of Medical Sciences, Shiraz, Czechia
| | - Rajender S. Varma
- Regional Centre of Advanced Technologies and Materials, Czech Advanced Technology and Research Institute, Palacký University in Olomouc, Olomouc, Czechia
| | - Faroogh Marofi
- Department of Hematology, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Mostafa Jarahian
- Toxicology and Chemotherapy Unit (G401), German Cancer Research Center, Heidelberg, Germany
| | - Nasrin Beheshtkhoo
- Department of Medical Nanotechnology, School of Advanced Medical Sciences and Technologies, Shiraz University of Medical Sciences, Shiraz, Czechia
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Wang F, Liu J, Zeng H. Interactions of particulate matter and pulmonary surfactant: Implications for human health. Adv Colloid Interface Sci 2020; 284:102244. [PMID: 32871405 PMCID: PMC7435289 DOI: 10.1016/j.cis.2020.102244] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Revised: 08/12/2020] [Accepted: 08/14/2020] [Indexed: 12/22/2022]
Abstract
Particulate matter (PM), which is the primary contributor to air pollution, has become a pervasive global health threat. When PM enters into a respiratory tract, the first body tissues to be directly exposed are the cells of respiratory tissues and pulmonary surfactant. Pulmonary surfactant is a pivotal component to modulate surface tension of alveoli during respiration. Many studies have proved that PM would interact with pulmonary surfactant to affect the alveolar activity, and meanwhile, pulmonary surfactant would be adsorbed to the surface of PM to change the toxic effect of PM. This review focuses on recent studies of the interactions between micro/nanoparticles (synthesized and environmental particles) and pulmonary surfactant (natural surfactant and its models), as well as the health effects caused by PM through a few significant aspects, such as surface properties of PM, including size, surface charge, hydrophobicity, shape, chemical nature, etc. Moreover, in vitro and in vivo studies have shown that PM leads to oxidative stress, inflammatory response, fibrosis, and cancerization in living bodies. By providing a comprehensive picture of PM-surfactant interaction, this review will benefit both researchers for further studies and policy-makers for setting up more appropriate regulations to reduce the adverse effects of PM on public health.
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Affiliation(s)
- Feifei Wang
- The Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou, Guangdong 510700, China,Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada
| | - Jifang Liu
- The Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou, Guangdong 510700, China.
| | - Hongbo Zeng
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada.
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Seimei A, Saeki D, Matsuyama H. Effect of polyelectrolyte structure on formation of supported lipid bilayers on polyelectrolyte multilayers prepared using the layer-by-layer method. J Colloid Interface Sci 2020; 569:211-218. [DOI: 10.1016/j.jcis.2020.02.079] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 01/20/2020] [Accepted: 02/19/2020] [Indexed: 11/17/2022]
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Bilotto P, Lengauer M, Andersson J, Ramach U, Mears LLE, Valtiner M. Interaction Profiles and Stability of Rigid and Polymer-Tethered Lipid Bilayer Models at Highly Charged and Highly Adhesive Contacts. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:15552-15563. [PMID: 31475831 DOI: 10.1021/acs.langmuir.9b01942] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Understanding interaction force versus distance profiles of supported lipid bilayers (SLBs) is relevant to a number of areas, which rely on these model systems, including, e.g., characterization of ligand/receptor interactions or bacterial adhesion. Here, the stability of 4 different SLB architectures was compared using the surface forces apparatus (SFA) and atomic force microscopy (AFM). Specifically, the outer envelope of the bilayer systems remained constant as 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). The inner layer was varied between DPPC and 1,2-dipalmitoyl-3-trimethylammonium-propane (DPTAP) both on mica, and self-assembled monolayers (SAMs) of hexadecanethiol and the polymer-tethered diphytanylglycerol-tetraethylene glycol-lipoid acid (DPhyTL) on smooth gold surfaces. In that same order these gave an increasing strength of interaction between the inner layer and the supporting substrate and hence improved stability under highly adhesive conditions. Detachment profiles from highly charged and highly adhesive contacts were characterized, and approach characteristics were fitted to DLVO models. We find increasing stability under highly adhesive loads, approaching the hydrophobic limit of the adhesive energy between the inner and outer layers for the SAM-based systems. For all four SLBs we further compare AFM surface topographies, which strongly depend on preparation conditions, and the DLVO fitting of the SFA approach curves finds a strong charge regulation behavior during interaction, dependent on the particular model system. In addition, we find undulation characteristics during approach and separation. The increased stability of the complex architectures on a gold support makes these model systems an ideal starting point for studying more complex strongly adhesive/interacting systems, including, for example, ligand/receptor interactions, biosensing interactions, or cell/surface interactions.
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Affiliation(s)
- Pierluigi Bilotto
- Institute of Applied Physics , Vienna University of Technology , Vienna 1040 , Austria
| | - Maximilian Lengauer
- Institute of Applied Physics , Vienna University of Technology , Vienna 1040 , Austria
| | | | - Ulrich Ramach
- Institute of Applied Physics , Vienna University of Technology , Vienna 1040 , Austria
- CEST Kompetenzzentrum für elektrochemische Oberflächentechnologie , Wiener Neustadt 2700 , Austria
| | - Laura L E Mears
- Institute of Applied Physics , Vienna University of Technology , Vienna 1040 , Austria
| | - Markus Valtiner
- Institute of Applied Physics , Vienna University of Technology , Vienna 1040 , Austria
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10
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Cao Y, Kampf N, Klein J. Boundary Lubrication, Hemifusion, and Self-Healing of Binary Saturated and Monounsaturated Phosphatidylcholine Mixtures ⧫. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:15459-15468. [PMID: 31296001 DOI: 10.1021/acs.langmuir.9b01660] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
A wide range of phosphatidylcholine (PC) lipids with different degrees of unsaturation has been identified in the human synovial fluid and on the cartilage surface. The outstanding lubricity of the articular cartilage surface has been attributed to boundary layers comprising complexes of such lipids, though to date, only lubrication by single-component PC-lipid-based boundary layers has been investigated. As distinguishable lubrication behavior has been found to be related to the PC structures, we herein examined the surface morphology (on mica) and the lubrication ability of binary PC lipid mixtures, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), using atomic force microscopy (AFM) and a surface force balance (SFB). These two PC lipids are among the most abundant saturated and unsaturated PC components in synovial joints. Small unilamellar vesicles (SUVs) prepared from DPPC-POPC mixtures (8:2, 5:5, and 2:8, molar ratios) ruptured and formed bilayers on mica. The normal and shear forces between two DPPC-POPC bilayer-coated mica surfaces across the corresponding SUV dispersions show good boundary lubrication (friction coefficients ≤ ca. 10-4) up to contact stresses of 8.3 ± 2.2 MPa for 8:2 DPPC-POPC and 5.0 ± 1.7 MPa for the others. Hemifusion induced at high normal pressures was observed, probably because of the height mismatch of two components. Reproducible successive approaches after hemifusion indicate rapid self-healing of the mica-supported bilayers in the presence of the SUVs reservoir. This work is a first step to provide insight concerning the lubrication, wear, and healing of the PC-based boundary layers, which must consist of multicomponent lipid mixtures, on the articular cartilage surface.
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Affiliation(s)
- Yifeng Cao
- Department of Materials and Interfaces , Weizmann Institute of Science , Rehovot 76100 , Israel
| | - Nir Kampf
- Department of Materials and Interfaces , Weizmann Institute of Science , Rehovot 76100 , Israel
| | - Jacob Klein
- Department of Materials and Interfaces , Weizmann Institute of Science , Rehovot 76100 , Israel
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Kurniawan J, Ventrici de Souza JF, Dang AT, Liu GY, Kuhl TL. Preparation and Characterization of Solid-Supported Lipid Bilayers Formed by Langmuir-Blodgett Deposition: A Tutorial. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:15622-15639. [PMID: 30465730 DOI: 10.1021/acs.langmuir.8b03504] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The structure, phase behavior, and properties of cellular membranes are derived from their composition, which includes phospholipids, sphingolipids, sterols, and proteins with various levels of glycosylation. Because of the intricate nature of cellular membranes, a plethora of in vitro studies have been carried out with model membrane systems that capture particular properties such as fluidity, permeability, and protein binding but vastly simplify the membrane composition in order to focus in detail on a specialized property or function. Supported lipid bilayers (SLB) are widely used as archetypes for cellular membranes, and this instructional review primarily focuses on the preparation and characterization of SLB systems formed by Langmuir deposition methods. Typical characterization methods, which take advantage of the planar orientation of SLBs, are illustrated, and references that go into more depth are included. This invited instructional review is written so that nonexperts can quickly gain in-depth knowledge regarding the preparation and characterization of SLBs. In addition, this work goes beyond traditional instructional reviews to provide expert readers with new results that cover a wider range of SLB systems than those previously reported in the literature. The quality of an SLB is frequently not well described, and details such as topological defects can influence the results and conclusions of an individual study. This article quantifies and compares the quality of SLBs fabricated from a variety of gel and fluid compositions, in correlation with preparation techniques and parameters, to generate general rules of thumb to guide the construction of designed SLB systems.
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Sorkin R, Kampf N, Zhu L, Klein J. Hydration lubrication and shear-induced self-healing of lipid bilayer boundary lubricants in phosphatidylcholine dispersions. SOFT MATTER 2016; 12:2773-84. [PMID: 26861851 DOI: 10.1039/c5sm02475g] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Measurements of normal and shear (frictional) forces between mica surfaces across small unilamellar vesicle (SUV) dispersions of the phosphatidylcholine (PC) lipids DMPC (14:0), DPPC (16:0) and DSPC (18:0) and POPC (16:0, 18:1), at physiologically high pressures, are reported. We have previously studied the normal and shear forces between two opposing surfaces bearing PC vesicles across pure water and showed that liposome lubrication ability improved with increasing acyl chain length, and correlated strongly with the SUV structural integrity on the substrate surface (DSPC > DPPC > DMPC). In the current study, surprisingly, we discovered that this trend is reversed when the measurements are conducted in SUV dispersions, instead of pure water. In their corresponding SUV dispersion, DMPC SUVs ruptured and formed bilayers, which were able to provide reversible and reproducible lubrication with extremely low friction (μ < 10(-4)) up to pressures of 70-90 atm. Similarly, POPC SUVs also formed bilayers which exhibited low friction (μ < 10(-4)) up to pressures as high as 160 atm. DPPC and DSPC SUVs also provided good lubrication, but with slightly higher friction coefficients (μ = 10(-3)-10(-4)). We believe these differences originate from fast self-healing of the softer surface layers (which are in their liquid disordered phase, POPC, or close to it, DMPC), which renders the robustness of the DPPC or DSPC (both in their solid ordered phase) less important in these conditions. Under these circumstances, the enhanced hydration of the less densely packed POPC and DMPC surface layers is now believed to play an important role, and allows enhanced lubrication via the hydration lubrication mechanism. Our findings may have implications for the understanding of complex biological systems such us biolubrication of synovial joints.
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Affiliation(s)
- Raya Sorkin
- Weizmann Institute of Science, Materials and Interfaces Department, Rehovot, Israel.
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13
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Stetter FWS, Cwiklik L, Jungwirth P, Hugel T. Single lipid extraction: the anchoring strength of cholesterol in liquid-ordered and liquid-disordered phases. Biophys J 2015; 107:1167-1175. [PMID: 25185552 DOI: 10.1016/j.bpj.2014.07.018] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Revised: 06/29/2014] [Accepted: 07/07/2014] [Indexed: 11/18/2022] Open
Abstract
Cholesterol is important for the formation of microdomains in supported lipid bilayers and is enriched in the liquid-ordered phase. To understand the interactions leading to this enrichment, we developed an AFM-based single-lipid-extraction (SLX) approach that enables us to determine the anchoring strength of cholesterol in the two phases of a phase-separated lipid membrane. As expected, the forces necessary for extracting a single cholesterol molecule from liquid-ordered phases are significantly higher than for extracting it from the liquid-disordered phases. Interestingly, application of the Bell model shows two energy barriers that correlate with the head and full length of the cholesterol molecule. The resulting lifetimes for complete extraction are 90 s and 11 s in the liquid-ordered and liquid-disordered phases, respectively. Molecular dynamics simulations of the very same experiment show similar force profiles and indicate that the stabilization of cholesterol in the liquid-ordered phase is mainly due to nonpolar contacts.
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Affiliation(s)
- Frank W S Stetter
- Physik-Department E22a and IMETUM, Technische Universität München, Munich, Germany
| | - Lukasz Cwiklik
- J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic; Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
| | - Pavel Jungwirth
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic; Department of Physics, Tampere University of Technology, Tampere, Finland
| | - Thorsten Hugel
- Physik-Department E22a and IMETUM, Technische Universität München, Munich, Germany.
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Jurak M, Golabek M, Holysz L, Chibowski E. Properties of Langmuir and solid supported lipid films with sphingomyelin. Adv Colloid Interface Sci 2015; 222:385-97. [PMID: 24725646 DOI: 10.1016/j.cis.2014.03.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 03/19/2014] [Accepted: 03/20/2014] [Indexed: 12/11/2022]
Abstract
Biological cell membranes play a crucial role in various biological processes and their functionality to some extent is determined by the hydrophilic/hydrophobic balance. A significant progress in understanding the membrane structure was the discovery of laterally segregated lipid domains, called the lipid rafts. These raft domains are of ordered lamellar liquid-crystalline phase, while rest of the membrane exists in a relatively disordered lamellar liquid-crystalline phase. Moreover, the chemical constitution of the lipid rafts consists of a higher content (up to 50%) of cholesterol (Chol) and sphingomyelin (SM). Sphingomyelin also plays a significant role in the red cells of blood and nerves, in some diseases, as a precursor to ceramides, and other sphingolipid metabolites. In this paper properties of Langmuir and solid supported mixed lipid films of DPPC/SM, DOPC/SM, and Chol/SM are described. Special attention has been paid to wetting properties (hydrophobic/hydrophilic balance) of these films transferred onto a hydrophilic glass surface. To our knowledge such results have not yet been published in the literature. The properties were determined via contact angle measurements and then calculation of the films' apparent surface free energy. The films' wettability and their apparent surface free energy strongly depend on their composition. The energy is affected by both the structure of hydrocarbon chains of glycerophospholipids (DPPC and DOPC) and their interactions with SM. Properties of mixed Chol/SM monolayer depend also on the film stoichiometry. At a low Chol content (XChol=0.25) the interactions between SM and Chol are strong and hence the formation of binary complex is possible. This is accompanied by a decrease in the film surface free energy in comparison to that of pure SM monolayer, contrary to a higher Chol content where the monolayer energy increases. This suggests that cholesterol is excluded from the membrane thus increasing the film hydrophilicity. These results are consistent with the literature data and somehow confirm the hypothesis of lipid raft formation. The roughness of the investigated monolayer surfaces was also determined using optical profilometry. The roughness parameters of the DPPC, SM, and mixed DPPC/SM generally correlate with the changes of their apparent surface free energy, i.e. with the decreasing roughness the apparent surface free energy also decreases. However, this is not the case for mixed DOPC/SM monolayers. Although the roughness increases with SM content the apparent surface free energy decreases. Therefore some other factors, like the presence of unsaturated bonds in the DOPC molecule, influence the film phase state and the energy too. More experiments are needed to explain this hypothesis.
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Melbourne J, Clancy A, Seiffert J, Skepper J, Tetley TD, Shaffer MSP, Porter A. An investigation of the carbon nanotube--Lipid interface and its impact upon pulmonary surfactant lipid function. Biomaterials 2015; 55:24-32. [PMID: 25934449 DOI: 10.1016/j.biomaterials.2015.03.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Revised: 03/08/2015] [Accepted: 03/15/2015] [Indexed: 11/16/2022]
Abstract
Multiwalled carbon nanotubes (MWCNTs) are now synthesized on a large scale, increasing the risk of occupational inhalation. However, little is known of the MWCNT-pulmonary surfactant (PS) interface and its effect on PS functionality. The Langmuir-Blodgett trough was used to evaluate the impact of MWCNTs on fundamental properties of PS lipids which influence PS function, i.e. compression resistance and maximum obtainable pressure. Changes were found to be MWCNT length-dependent. 'Short' MWCNTs (1.1 μm, SD = 0.61) penetrated the lipid film, reducing the maximum interfacial film pressure by 10 mN/m (14%) in dipalmitoylphosphatidylcholine (DPPC) and PS, at an interfacial MWCNT-PS lipid mass ratio range of 50:1 to 1:1. 'Long' commercial MWCNTs (2.1 μm, SD = 1.2) caused compression resistance at the same mass loadings. 'Very long' MWCNTs (35 μm, SD = 19) sequestered DPPC and were squeezed out of the DPPC film. High resolution transmission electron microscopy revealed that all MWCNT morphologies formed DPPC coronas with ordered arrangements. These results provide insight into how nanoparticle aspect ratio affects the interaction mechanisms with PS, in its near-native state at the air-water interface.
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Affiliation(s)
- Jodie Melbourne
- Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
| | - Adam Clancy
- Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ, UK
| | - Joanna Seiffert
- National Heart and Lung Institute, Imperial College London, Dovehouse Street, London SW3 6LY, UK
| | - Jeremy Skepper
- Multi-Imaging Centre, Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
| | - Teresa D Tetley
- National Heart and Lung Institute, Imperial College London, Dovehouse Street, London SW3 6LY, UK
| | - Milo S P Shaffer
- Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ, UK
| | - Alexandra Porter
- Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
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16
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Kienle DF, Kuhl TL. Analyzing refractive index profiles of confined fluids by interferometry. Anal Chem 2014; 86:11860-7. [PMID: 25365770 DOI: 10.1021/ac503469x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This work describes an interferometry data analysis method for determining the optical thickness of thin films or any variation in the refractive index of a fluid or film near a surface. In particular, the method described is applied to the analysis of interferometry data taken with a surface force apparatus (SFA). The technique does not require contacting or confining the fluid or film. By analyzing interferometry data taken at many intersurface separation distances out to at least 300 nm, the properties of a film can be quantitatively determined. The film can consist of material deposited on the surface, like a polymer brush, or variation in a fluid's refractive index near a surface resulting from, for example, a concentration gradient, depletion in density, or surface roughness. The method is demonstrated with aqueous polyethylenimine (PEI) adsorbed onto mica substrates, which has a large concentration and therefore refractive index gradient near the mica surface. The PEI layer thickness determined by the proposed method is consistent with the thickness measured by conventional SFA methods. Additionally, a thorough investigation of the effects of random and systematic error in SFA data analysis and modeling via simulations of interferometry is described in detail.
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Affiliation(s)
- Daniel F Kienle
- Department of Chemical Engineering and Materials Science, University of California Davis , Davis, California 95616, United States
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17
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Ramkaran M, Badia A. Gel-to-Fluid Phase Transformations in Solid-Supported Phospholipid Bilayers Assembled by the Langmuir–Blodgett Technique: Effect of the Langmuir Monolayer Phase State and Molecular Density. J Phys Chem B 2014; 118:9708-21. [DOI: 10.1021/jp504092b] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Mohini Ramkaran
- Department of Chemistry,
FRQNT Centre for Self-Assembled Chemical Structures, Université de Montréal, C.P. 6128 succursale Centre-ville, Montréal, QC H3C 3J7, Canada
| | - Antonella Badia
- Department of Chemistry,
FRQNT Centre for Self-Assembled Chemical Structures, Université de Montréal, C.P. 6128 succursale Centre-ville, Montréal, QC H3C 3J7, Canada
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18
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19
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Oh DX, Shin S, Yoo HY, Lim C, Hwang DS. Surface forces apparatus and its applications for nanomechanics of underwater adhesives. KOREAN J CHEM ENG 2014. [DOI: 10.1007/s11814-014-0136-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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20
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Kurniawan J, Yin NN, Liu GY, Kuhl TL. Interaction forces between ternary lipid bilayers containing cholesterol. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:4997-5004. [PMID: 24716859 DOI: 10.1021/la500341c] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Interaction force-distance profiles between substrate-supported membranes composed of equimolar ternary mixtures of unsaturated phosphotidylcholine (PC) lipid, saturated PC lipid, and cholesterol were determined using the surface force apparatus. Both double and single unsaturated PC lipids were studied. In all cases, the membranes were slightly negatively charged, resulting in a weak, long-range electrostatic repulsion. Corroborative atomic force microscopy, zeta potential, and fluorescence microscopy measurements were used to establish that a small level of charged lipid impurities (∼1/400 lipid molecules) were responsible for the repulsive electrostatic interaction between the membranes. At contact, the membranes were adhesive. The magnitude of the adhesion was greater than the van der Waals interaction between pure PC membranes without cholesterol. The enhanced adhesion was primarily attributed to hydrophobic attraction due to the presence of nanoscopic membrane defects which exposed the underlying membrane leaflet. The interaction force-distance profiles also demonstrated that the nanoscopic defects enabled membrane restructuring in the contact region.
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Affiliation(s)
- James Kurniawan
- Department of Chemical Engineering and Materials Science and ‡Department of Chemistry, University of California-Davis , Davis, California 95616, United States
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21
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Seror J, Sorkin R, Klein J. Boundary lubrication by macromolecular layers and its relevance to synovial joints. POLYM ADVAN TECHNOL 2014. [DOI: 10.1002/pat.3295] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Jasmine Seror
- Department of Materials and Interfaces; Weizmann Institute of Science; Rehovot 76100 Israel
| | - Raya Sorkin
- Department of Materials and Interfaces; Weizmann Institute of Science; Rehovot 76100 Israel
| | - Jacob Klein
- Department of Materials and Interfaces; Weizmann Institute of Science; Rehovot 76100 Israel
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22
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Redondo-Morata L, Giannotti MI, Sanz F. Structural impact of cations on lipid bilayer models: Nanomechanical properties by AFM-force spectroscopy. Mol Membr Biol 2013; 31:17-28. [DOI: 10.3109/09687688.2013.868940] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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23
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Barthel E, Roquigny R, Serreau L, Denoyel R, Clerc-Imperor M, Drummond C. Contact interaction of double-chained surfactant layers on silica: bilayer rupture and capillary bridge formation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:14473-14481. [PMID: 24171391 DOI: 10.1021/la403044x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The contact between two layers of double-chained C18 surfactants adsorbed on silica has been investigated. Using a custom-made surface forces apparatus with high stiffness, we have studied the process of (1) compression and collapse of the layers and (2) surface separation after layer collapse. A continuum mechanics model accounts for the compression and collapse of the surfactant layers. The layer compressibility and molecular energy of rupture can be inferred directly. When the surfaces are rinsed in deionized water, an intriguing structural force is observed: the resulting attractive interaction induces the diffusion of surfactant to the contact area, with the gradual buildup of a capillary bridge of the pure smectic phase of the surfactant. Models are proposed to analyze the force profile.
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Affiliation(s)
- Etienne Barthel
- Surface du Verre et Interfaces, CNRS/Saint-Gobain , BP 135, 93303 Aubervilliers Cedex, France
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24
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Stetter FWS, Hugel T. The nanomechanical properties of lipid membranes are significantly influenced by the presence of ethanol. Biophys J 2013; 104:1049-55. [PMID: 23473487 DOI: 10.1016/j.bpj.2013.01.021] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Revised: 12/16/2012] [Accepted: 01/14/2013] [Indexed: 12/27/2022] Open
Abstract
Ethanol has a profound impact on biological systems and is moreover used in various medical and nonmedical applications. Its interaction with the lipid part of biological membranes has been the subject of intensive studies, but surprisingly, to our knowledge, no study has examined the influence of ethanol on lipid bilayer nanomechanics. We performed atomic force microscopy-based measurements to assess the influence of ethanol on the nanomechanical properties of fluid supported lipid bilayers. Ethanol significantly reduces membrane stability, bilayer thickness, Young's modulus, area stretch modulus, and bending stiffness. Altogether, our data suggest that ethanol addition to supported lipid bilayers supports both the hydrophobic and the hydrophilic permeation pathways by a decrease of bilayer thickness and reduced stability, respectively.
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Affiliation(s)
- Frank W S Stetter
- IMETUM, Physik-Department, E22a, Technische Universität München, Munich, Germany
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25
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Sorkin R, Kampf N, Dror Y, Shimoni E, Klein J. Origins of extreme boundary lubrication by phosphatidylcholine liposomes. Biomaterials 2013; 34:5465-75. [PMID: 23623226 DOI: 10.1016/j.biomaterials.2013.03.098] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Accepted: 03/31/2013] [Indexed: 11/29/2022]
Abstract
Phosphatidylcholine (PC) vesicles have been shown to have remarkable boundary lubricating properties under physiologically-high pressures. Here we carry out a systematic study, using a surface force balance, of the normal and shear (frictional) forces between two opposing surfaces bearing different PC vesicles across water, to elucidate the origin of these properties. Small unilamellar vesicles (SUVs, diameters < 100 nm) of the symmetric saturated diacyl PCs DMPC (C(14)), DPPC (C(16)) and DSPC (C(18)) attached to mica surfaces were studied in their solid-ordered (SO) phase on the surface. Overall liposome lubrication ability improves markedly with increasing acyl chain length, and correlates strongly with the liposomes' structural integrity on the substrate surface: DSPC-SUVs were stable on the surface, and provided extremely efficient lubrication (friction coefficient μ ≈ 10(-4)) at room temperature at pressures up to at least 18 MPa. DMPC-SUVs ruptured following adsorption, providing poor high-pressure lubrication, while DPPC-SUVs behavior was intermediate between the two. These results can be well understood in terms of the hydration-lubrication paradigm, but suggest that an earlier conjecture, that highly-efficient lubrication by PC-SUVs depended simply on their being in the SO rather than in the liquid-disordered phase, should be more nuanced. Our results indicate that the resistance of the SUVs to mechanical deformation and rupture is the dominant factor in determining their overall boundary lubrication efficiency in our system.
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Affiliation(s)
- Raya Sorkin
- Materials and Interfaces Department, Weizmann Institute of Science, Rehovot 76100, Israel
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26
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Preparation of DOPC and DPPC Supported Planar Lipid Bilayers for Atomic Force Microscopy and Atomic Force Spectroscopy. Int J Mol Sci 2013; 14:3514-39. [PMID: 23389046 PMCID: PMC3588056 DOI: 10.3390/ijms14023514] [Citation(s) in RCA: 150] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Revised: 01/29/2013] [Accepted: 02/01/2013] [Indexed: 11/16/2022] Open
Abstract
Cell membranes are typically very complex, consisting of a multitude of different lipids and proteins. Supported lipid bilayers are widely used as model systems to study biological membranes. Atomic force microscopy and force spectroscopy techniques are nanoscale methods that are successfully used to study supported lipid bilayers. These methods, especially force spectroscopy, require the reliable preparation of supported lipid bilayers with extended coverage. The unreliability and a lack of a complete understanding of the vesicle fusion process though have held back progress in this promising field. We document here robust protocols for the formation of fluid phase DOPC and gel phase DPPC bilayers on mica. Insights into the most crucial experimental parameters and a comparison between DOPC and DPPC preparation are presented. Finally, we demonstrate force spectroscopy measurements on DOPC surfaces and measure rupture forces and bilayer depths that agree well with X-ray diffraction data. We also believe our approach to decomposing the force-distance curves into depth sub-components provides a more reliable method for characterising the depth of fluid phase lipid bilayers, particularly in comparison with typical image analysis approaches.
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27
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Abstract
Lipid bilayers are natural barriers of biological cells and cellular compartments. Membrane proteins integrated in biological membranes enable vital cell functions such as signal transduction and the transport of ions or small molecules. In order to determine the activity of a protein of interest at defined conditions, the membrane protein has to be integrated into artificial lipid bilayers immobilized on a surface. For the fabrication of such biosensors expertise is required in material science, surface and analytical chemistry, molecular biology and biotechnology. Specifically, techniques are needed for structuring surfaces in the micro- and nanometer scale, chemical modification and analysis, lipid bilayer formation, protein expression, purification and solubilization, and most importantly, protein integration into engineered lipid bilayers. Electrochemical and optical methods are suitable to detect membrane activity-related signals. The importance of structural knowledge to understand membrane protein function is obvious. Presently only a few structures of membrane proteins are solved at atomic resolution. Functional assays together with known structures of individual membrane proteins will contribute to a better understanding of vital biological processes occurring at biological membranes. Such assays will be utilized in the discovery of drugs, since membrane proteins are major drug targets.
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28
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Sunnick E, Janshoff A, Geil B. Energetics of adhesion cluster formation in the context of biological membranes. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 86:051913. [PMID: 23214820 DOI: 10.1103/physreve.86.051913] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Revised: 10/30/2012] [Indexed: 06/01/2023]
Abstract
The orchestration of cellular adhesion is an intricate process that involves a multitude of specialized proteins but at the same time follows a simple physical plan. It is still not totally known why cells create clusters of bonds to adhere on a substrate. Besides experimental methods to study cellular adhesion there exist several different theoretical models to describe the stability of focal adhesion clusters. The model proposed in this work makes it possible to understand the formation of adhesion bond clusters. It explains the emergence of a long-range bond-bond attraction that originates from the finite membrane elasticity as the driving force of cluster growth. In combination with a thermally driven bond disintegration such a model will eventually be able to explain the kinetic stability of finite size bond clusters. The model extends conventional two-state models where bonds are either open or closed by introducing a rich scenario of metastable states associated with hysteretic behavior in the bond closure and rupture dynamics.
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Affiliation(s)
- Eva Sunnick
- Institut für Physikalische Chemie, Universität Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
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29
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Goldberg R, Klein J. Liposomes as lubricants: beyond drug delivery. Chem Phys Lipids 2011; 165:374-81. [PMID: 22119851 DOI: 10.1016/j.chemphyslip.2011.11.007] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Revised: 11/10/2011] [Accepted: 11/11/2011] [Indexed: 10/15/2022]
Abstract
In this paper we review recent work (Goldberg et al., 2011a,b) on a new use for phosphatidylcholine liposomes: as ultra-efficient boundary lubricants at up to the highest physiological pressures. Using a surface force balance, we have measured the normal and shear interactions as a function of surface separation between layers of hydrogenated soy phophatidylcholine (HSPC) small unilamellar vesicles (SUVs) adsorbed from dispersion, at both pure water and physiologically high salt concentrations of 0.15 M NaNO(3). Cryo-Scanning Electron Microscopy shows each surface to be coated by a close-packed HSPC-SUV layer with an over-layer of liposomes on top. The shear forces reveal strikingly low friction coefficients down to 2×10(-5) in pure water system or 6×10(-4) in the 150 mM salt system, up to contact pressures of at least 12 MPa (pure water) or 6 MPa (high salt), comparable with those in the major joints. This low friction is attributed to the hydration lubrication mechanism arising from rubbing of the highly hydrated phosphocholine-headgroup layers exposed at the outer surface of each liposome, and provides support for the conjecture that phospholipids may play a significant role in biological lubrication.
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Affiliation(s)
- Ronit Goldberg
- Dept. of Materials and Interfaces, Weizmann Institute, Rehovot 76100, Israel
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30
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Alam JM, Yamazaki M. Spontaneous insertion of lipopolysaccharide into lipid membranes from aqueous solution. Chem Phys Lipids 2011; 164:166-74. [DOI: 10.1016/j.chemphyslip.2010.12.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2010] [Revised: 12/17/2010] [Accepted: 12/21/2010] [Indexed: 10/18/2022]
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31
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Garcia-Manyes S, Redondo-Morata L, Oncins G, Sanz F. Nanomechanics of Lipid Bilayers: Heads or Tails? J Am Chem Soc 2010; 132:12874-86. [DOI: 10.1021/ja1002185] [Citation(s) in RCA: 117] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Sergi Garcia-Manyes
- Department of Biological Sciences, Columbia University, New York, 10027, New York, Departament de Química Física, Universitat de Barcelona, 08028, Spain, Institut de Bioenginyeria de Catalunya, Barcelona, 08028, Spain, Serveis Cientificotècnics, Universitat de Barcelona, 08028, Spain, and CIBER-BBN, Zaragoza 50018, Spain
| | - Lorena Redondo-Morata
- Department of Biological Sciences, Columbia University, New York, 10027, New York, Departament de Química Física, Universitat de Barcelona, 08028, Spain, Institut de Bioenginyeria de Catalunya, Barcelona, 08028, Spain, Serveis Cientificotècnics, Universitat de Barcelona, 08028, Spain, and CIBER-BBN, Zaragoza 50018, Spain
| | - Gerard Oncins
- Department of Biological Sciences, Columbia University, New York, 10027, New York, Departament de Química Física, Universitat de Barcelona, 08028, Spain, Institut de Bioenginyeria de Catalunya, Barcelona, 08028, Spain, Serveis Cientificotècnics, Universitat de Barcelona, 08028, Spain, and CIBER-BBN, Zaragoza 50018, Spain
| | - Fausto Sanz
- Department of Biological Sciences, Columbia University, New York, 10027, New York, Departament de Química Física, Universitat de Barcelona, 08028, Spain, Institut de Bioenginyeria de Catalunya, Barcelona, 08028, Spain, Serveis Cientificotècnics, Universitat de Barcelona, 08028, Spain, and CIBER-BBN, Zaragoza 50018, Spain
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32
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Lorenz B, Keller R, Sunnick E, Geil B, Janshoff A. Colloidal probe microscopy of membrane–membrane interactions: From ligand–receptor recognition to fusion events. Biophys Chem 2010; 150:54-63. [DOI: 10.1016/j.bpc.2010.02.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Revised: 02/05/2010] [Accepted: 02/07/2010] [Indexed: 10/19/2022]
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33
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Stability and tribological performances of fluid phospholipid bilayers: effect of buffer and ions. Colloids Surf B Biointerfaces 2010; 80:232-9. [PMID: 20634046 DOI: 10.1016/j.colsurfb.2010.06.012] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2010] [Revised: 05/21/2010] [Accepted: 06/17/2010] [Indexed: 11/24/2022]
Abstract
We have investigated the mechanical and tribological properties of supported Dioleoyl phosphatidylcholine (DOPC) bilayers in different solutions: ultrapure water (pH 5.5), saline solution (150 mM NaCl, pH 5.8), Tris buffer (pH 7.2) and Tris saline buffer (150 mM NaCl, pH 7.2). Friction forces are measured using a homemade biotribometer. Lipid bilayer degradation is controlled in situ during friction tests using fluorescence microscopy. Mechanical resistance to indentation is measured by force spectroscopy with an atomic force microscope. This study confirms that mechanical stability under shear or normal load is essential to obtain low and constant friction coefficients. In ultrapure water, bilayers are not resistant and have poor lubricant properties. On the other hand, in Tris saline buffer, they fully resist to indentation and exhibit low (micro=0.035) and stable friction coefficient with no visible wear during the 50 min of the friction test. The unbuffered saline solution improves the mechanical resistance to indentation but not the lubrication. These results suggest that the adsorption of ions to the zwiterrionic bilayers has different effects on the mechanical and tribological properties of bilayers: higher resistance to normal indentation due to an increase in bilayer cohesion, higher lubrication due to an increase in bilayer-bilayer repulsion.
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34
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Nanomechanics of lipid bilayers by force spectroscopy with AFM: A perspective. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:741-9. [DOI: 10.1016/j.bbamem.2009.12.019] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2009] [Revised: 12/16/2009] [Accepted: 12/20/2009] [Indexed: 01/11/2023]
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35
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Miao S, Leeman H, De Feyter S, Schoonheydt R. Three-Component Langmuir-Blodgett Films Consisting of Surfactant, Clay Mineral, and Lysozyme: Construction and Characterization. Chemistry 2010; 16:2461-9. [DOI: 10.1002/chem.200900584] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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36
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Liu J, Jiang X, Ashley C, Brinker CJ. Electrostatically mediated liposome fusion and lipid exchange with a nanoparticle-supported bilayer for control of surface charge, drug containment, and delivery. J Am Chem Soc 2009; 131:7567-9. [PMID: 19445508 DOI: 10.1021/ja902039y] [Citation(s) in RCA: 194] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The loading and containment of cargo within nanoparticles and their efficient delivery to cells represent a primary challenge in nanomedicine. We report lipid exchange between free and mesoporous silica nanoparticle-supported lipid bilayers as an effective means of containing cargo, controlling charge, and directing delivery to mammalian cells. The delivery of a membrane-impermeable dye (calcein) and a chemotherapeutic drug (doxorubicin) are demonstrated. Exchanged lipid bilayers minimized premature drug release, and an overall positive charge on the supported lipid bilayer effected enhanced delivery.
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Affiliation(s)
- Juewen Liu
- Center for Micro-Engineered Materials, University of New Mexico, Albuquerque, New Mexico 87106, USA
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37
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Adsorption and onset of lubrication by a double-chained cationic surfactant on silica surfaces. J Colloid Interface Sci 2009; 332:382-8. [DOI: 10.1016/j.jcis.2008.12.065] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2008] [Revised: 12/19/2008] [Accepted: 12/20/2008] [Indexed: 11/18/2022]
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38
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Scomparin C, Lecuyer S, Ferreira M, Charitat T, Tinland B. Diffusion in supported lipid bilayers: influence of substrate and preparation technique on the internal dynamics. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2009; 28:211-20. [PMID: 19101741 DOI: 10.1140/epje/i2008-10407-3] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2008] [Revised: 07/22/2008] [Accepted: 11/17/2008] [Indexed: 05/22/2023]
Abstract
The diffusion law of DMPC and DPPC in Supported Lipid Bilayers (SLB), on different substrates, has been investigated in details by Fluorescence Recovery After Patterned Photobleaching (FRAPP). Over micrometer length scales, we demonstrate the validity of a purely Brownian diffusive law both in the gel and the fluid phases of the lipids. Measuring the diffusion coefficient as a function of temperature, we characterize the gel-to-liquid phase transition of DMPC and DPPC. It is shown that, depending on the type of substrate and the method used for bilayer preparation, completely different behaviours can be observed. On glass substrates, using the Langmuir-Blodgett deposition technique, both leaflets of the bilayer have the same dynamics. On mica, the dynamics of the proximal leaflet is slower than the dynamics of the distal leaflet, although the transition temperature is the same for both layers. Preparing bilayers from vesicle fusion in same conditions leads to more random behaviours and shifted transition temperatures.
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Affiliation(s)
- C Scomparin
- CINAM-CNRS UPR 3118, 13288 Marseille Cedex 09, France
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39
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Trunfio-Sfarghiu AM, Berthier Y, Meurisse MH, Rieu JP. Role of nanomechanical properties in the tribological performance of phospholipid biomimetic surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:8765-8771. [PMID: 18620439 DOI: 10.1021/la8005234] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The role of phospholipid bilayers in controlling and reducing frictional forces between biological surfaces is investigated by three complementary experiments: friction forces are measured using a homemade tribometer, mechanical resistance to indentation is measured by AFM, and lipid bilayer degradation is controlled in situ during friction testing using fluorescence microscopy. DPPC lipid bilayers in the solid phase generate friction coefficients as low as 0.002 (comparable to that found for cartilage) that are stable through time. DOPC bilayers formed by the vesicle fusion method or the adsorption of mixed micelles generate higher friction coefficients. These coefficients increased through time, during which the bilayers degraded. The friction coefficient is correlated with the force needed to penetrate the bilayer with the AFM tip. With only one bilayer in the contact region, the friction increased to a similar value of about 0.08 for the DPPC and DOPC. Our study therefore shows that good mechanical stability of the bilayers is essential and suggests that the low friction coefficient is ensured by the hydration layers between adjacent lipid bilayers.
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Hughes AV, Howse JR, Dabkowska A, Jones RAL, Lawrence MJ, Roser SJ. Floating lipid bilayers deposited on chemically grafted phosphatidylcholine surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:1989-99. [PMID: 18198904 DOI: 10.1021/la702050b] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Floating supported bilayers (FSBs) are new systems which have emerged over the past few years to produce supported membrane mimics, where the bilayers remain associated with the substrate, but are cushioned from the substrates constraining influence by a large hydration layer. In this paper we describe a new approach to fabricating FSBs using a chemically grafted phospholipid layer as the support for the floating membrane. The grafted lipid layer was produced using a Langmuir-Schaeffer transfer of acryloyl-functionalized lipid onto a pre-prepared substrate, with AIBN-induced cross-polymerization to permanently bind the lipids in place. A bilayer of DSPC was then deposited onto this grafted monolayer using a combination of Langmuir-Blodgett and Langmuir-Schaeffer transfer. The resulting system was characterized by neutron reflection under two water contrasts, and we show that the new system shows a hydrating layer of approximately 17.5 A in the gel phase, which is comparable to previously described FSB systems. We provide evidence that the grafted substrate is reusable after cleaning and suggest that this greatly simplifies the fabrication and characterization of FSBs compared to previous methods.
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Affiliation(s)
- Arwel V Hughes
- ISIS, Rutherford Appleton Laboratory, Chilton, Didcot, OX11 OPU, U.K.
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Park JW, Ahn DJ. Temperature effect on nanometer-scale physical properties of mixed phospholipid monolayers. Colloids Surf B Biointerfaces 2008; 62:157-61. [DOI: 10.1016/j.colsurfb.2007.09.020] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2007] [Revised: 09/10/2007] [Accepted: 09/17/2007] [Indexed: 11/16/2022]
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Min Y, Akbulut M, Belman N, Golan Y, Zasadzinski J, Israelachvili J. Normal and shear forces generated during the ordering (directed assembly) of confined straight and curved nanowires. NANO LETTERS 2008; 8:246-252. [PMID: 18069875 DOI: 10.1021/nl072553e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The effects of shape on nanowire interactions and shear-induced ordering were studied. Both the normal and lateral forces were sensitive to the particles' curvature. (i) No adhesion was observed between the confining surfaces, and the force profiles were short-ranged and mostly reversible for straight wires but longer-ranged and irreversible for curved wires. (ii) Structural phase transitions can occur in confined nanoparticle films. (iii) During shearing, straight wires order or align more easily than curved wires.
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Affiliation(s)
- Younjin Min
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California 93106, USA
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43
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Mager MD, Melosh NA. Lipid bilayer deposition and patterning via air bubble collapse. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:9369-77. [PMID: 17683151 DOI: 10.1021/la701372b] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
We report a new method for forming patterned lipid bilayers on solid substrates. In bubble collapse deposition (BCD), an air bubble is first "inked" with a monolayer of phospholipid molecules and then touched to the surface of a thermally oxidized silicon wafer and the air is slowly withdrawn. As the bubble shrinks, the lipid monolayer pressure increases. Once the monolayer exceeds the collapse pressure, it folds back on itself, depositing a stable lipid bilayer on the surface. These bilayer disks have lateral diffusion coefficients consistent with high quality supported bilayers. By sequentially depositing bilayers in overlapping areas, fluid connections between bilayers of different compositions are formed. Performing vesicle rupture on the open substrate surrounding this bilayer patch results in a fluid but spatially isolated bilayer. Very little intermixing was observed between the vesicle rupture and bubble-deposited bilayers.
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Affiliation(s)
- Morgan D Mager
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA
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Simon A, Girard-Egrot A, Sauter F, Pudda C, Picollet D'Hahan N, Blum L, Chatelain F, Fuchs A. Formation and stability of a suspended biomimetic lipid bilayer on silicon submicrometer-sized pores. J Colloid Interface Sci 2007; 308:337-43. [PMID: 17275017 DOI: 10.1016/j.jcis.2006.11.050] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2006] [Revised: 11/28/2006] [Accepted: 11/29/2006] [Indexed: 11/18/2022]
Abstract
We report the fabrication of a thin silicon membrane with an array of micrometer and submicrometer pores that acts as a scaffold for suspending a lipid bilayer. We successfully deposited a lipid bilayer by the Langmuir-Blodgett method on a synthetic silicon membrane bearing arrays of pores with sizes of 1000, 650, and 300 nm. Topographic images obtained by AFM showed a suspended lipid film spanning the pores, whatever the pore size. Higher stability of bilayers supported on smaller pores was shown by AFM characterization. These results represent an important first step to creating a biomimetic environment to study cell membrane dynamics and/or in developing a biosensor.
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Affiliation(s)
- A Simon
- CEA, DSV/DRDC/Biopuces, 38 054 Grenoble cedex 9, France.
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Köhler G, Moya SE, Leporatti S, Bitterlich C, Donath E. Stability and fusion of lipid layers on polyelectrolyte multilayer supports studied by colloidal force spectroscopy. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2007; 36:337-47. [PMID: 17294178 DOI: 10.1007/s00249-007-0135-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2006] [Revised: 01/11/2007] [Accepted: 01/17/2007] [Indexed: 11/30/2022]
Abstract
The interaction between lipid layers supported by polyelectrolyte multilayer cushions has been studied by means of colloidal force spectroscopy. In a typical experiment, a colloidal probe engineered with a layer-by-layer film and a lipid bilayer on top is approached to a planar surface coated in a symmetrical way. Kinks of a few nanometres in width appear when lipid layers are pressed together--reflecting either fusion processes between lipid layers or membranes, or the penetration of polymer blobs into or through the lipid layers. Retracting curves show a stepwise shape, which results from lipid tether formation or from polymer stretching, the latter suggesting that polyelectrolyte multilayers make contact as a result of penetration or lipid fusion.
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Affiliation(s)
- Guido Köhler
- Institute of Medical Physics and Biophysics, Medical Faculty, University of Leipzig, Leipzig, Germany.
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Inaoka Y, Yamazaki M. Vesicle fission of giant unilamellar vesicles of liquid-ordered-phase membranes induced by amphiphiles with a single long hydrocarbon chain. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:720-8. [PMID: 17209626 DOI: 10.1021/la062078k] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Vesicle fissions are very important processes of biomembranes in cells, but their mechanisms are not clear and are controversial. Using the single giant unilamellar vesicle (GUV) method, we recently found that low concentrations (less than the critical micelle concentration (CMC)) of lysophosphatidylcholine (lyso-PC) induced the vesicle fission of GUVs of dipalmitoylphosphatidylcholine/cholesterol(6/4) (DPPC/chol(6/4)) membranes and sphingomyelin/cholesterol membranes (6/4) in the liquid-ordered (lo) phase. In this report, to elucidate its mechanism, we have investigated the effect of low concentrations (much less than their CMC) of other amphiphiles with a single long hydrocarbon chain (i.e., single long chain amphiphiles) on DPPC/chol(6/4) GUVs as well as the effect of the membrane composition on the lyso-PC-induced vesicle fission. We found that low concentrations of single long chain amphiphiles (lyosophosphatidic acid, octylglucoside, and sodium dodecyl sulfate) induced the shape change from a prolate to two spheres connected by a very narrow neck, indicating that the single long chain amphiphiles can be partitioned into the external monolayer in the lo phase of the GUV from the aqueous solution. As the single long chain amphiphile concentrations were increased, all of them induced vesicle fission of DPPC/chol(6/4) GUVs above their threshold concentrations. To elucidate the role of cholesterol in the single long chain amphiphile-induced vesicle fission, we investigated the effect of lyso-PC on GUVs of dioleoyl-PC (DOPC)/chol(6/4) membranes in the Lalpha phase; no vesicle fission occurred, indicating that cholesterol in itself did not play an important role in the vesicle fission. Finally, to elucidate the effect of the inclusion of DOPC in the lo-phase membrane of GUVs on the lyso-PC-induced vesicle fission of the DPPC/chol(6/4) GUV, we investigated the effect of low concentrations of lyso-PC on GUVs of DPPC/DOPC/chol membranes. With an increase in DOPC concentration in the membrane, the threshold concentration of lyso-PC increased. At and above 30 mol % DOPC, no vesicle fission occurred. On the basis of these results, we have proposed a hypothesis of the mechanism of the single long chain amphiphile-induced vesicle fission of a GUV of a lo-phase membrane.
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Affiliation(s)
- Yasuyuki Inaoka
- Department of Physics, Faculty of Science, Shizuoka University, Shizuoka, 422-8529, Japan
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Angelatos AS, Katagiri K, Caruso F. Bioinspired colloidal systems via layer-by-layer assembly. SOFT MATTER 2006; 2:18-23. [PMID: 32646088 DOI: 10.1039/b511930h] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
This paper provides an overview of our recent work in the area of bioinspired colloidal particles. We highlight how modifying the basic polyelectrolyte multilayer shell with materials such as light-absorbing gold nanoparticles, lipid bilayer membranes, and targeting ligands can functionalize colloids prepared the layer-by-layer assembly technique. These nanoengineered colloids are expected to show promise in areas ranging from drug and gene delivery to cell membrane modeling.
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Affiliation(s)
- Alexandra S Angelatos
- Centre for Nanoscience and Nanotechnology, Department of Chemical and Biomolecular Engineering, The University of Melbourne, Victoria 3010, Australia.
| | - Kiyofumi Katagiri
- Centre for Nanoscience and Nanotechnology, Department of Chemical and Biomolecular Engineering, The University of Melbourne, Victoria 3010, Australia.
| | - Frank Caruso
- Centre for Nanoscience and Nanotechnology, Department of Chemical and Biomolecular Engineering, The University of Melbourne, Victoria 3010, Australia.
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Howland MC, Szmodis AW, Sanii B, Parikh AN. Characterization of physical properties of supported phospholipid membranes using imaging ellipsometry at optical wavelengths. Biophys J 2006; 92:1306-17. [PMID: 17142265 PMCID: PMC1783900 DOI: 10.1529/biophysj.106.097071] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Subnanometer-scale vertical z-resolution coupled with large lateral area imaging, label-free, noncontact, and in situ advantages make the technique of optical imaging ellipsometry (IE) highly suitable for quantitative characterization of lipid bilayers supported on oxide substrates and submerged in aqueous phases. This article demonstrates the versatility of IE in quantitative characterization of structural and functional properties of supported phospholipid membranes using previously well-characterized examples. These include 1), a single-step determination of bilayer thickness to 0.2 nm accuracy and large-area lateral uniformity using photochemically patterned single 1,2-dimyristoyl-sn-glycero-3-phosphocholine bilayers; 2), hydration-induced spreading kinetics of single-fluid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayers to illustrate the in situ capability and image acquisition speed; 3), a large-area morphological characterization of phase-separating binary mixtures of 1,2-dilauroyl-sn-glycero-3-phosphocholine and galactosylceramide; and 4), binding of cholera-toxin B subunits to GM1-incorporating bilayers. Additional insights derived from these ellipsometric measurements are also discussed for each of these applications. Agreement with previous studies confirms that IE provides a simple and convenient tool for a routine, quantitative characterization of these membrane properties. Our results also suggest that IE complements more widely used fluorescence and scanning probe microscopies by combining large-area measurements with high vertical resolution without the use of labeled lipids.
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Affiliation(s)
- Michael C Howland
- Chemical Engineering and Materials Science Group, University of California, Davis, California 95616, USA
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Garcia-Manyes S, Oncins G, Sanz F. Effect of pH and ionic strength on phospholipid nanomechanics and on deposition process onto hydrophilic surfaces measured by AFM. Electrochim Acta 2006. [DOI: 10.1016/j.electacta.2006.03.062] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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50
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Chapter 4 Visualization and Characterization of Domains in Supported Model Membranes. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/s1554-4516(05)03004-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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