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El-Beyrouthy J, Freeman E. Characterizing the Structure and Interactions of Model Lipid Membranes Using Electrophysiology. MEMBRANES 2021; 11:319. [PMID: 33925756 PMCID: PMC8145864 DOI: 10.3390/membranes11050319] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 04/22/2021] [Accepted: 04/25/2021] [Indexed: 11/16/2022]
Abstract
The cell membrane is a protective barrier whose configuration determines the exchange both between intracellular and extracellular regions and within the cell itself. Consequently, characterizing membrane properties and interactions is essential for advancements in topics such as limiting nanoparticle cytotoxicity. Characterization is often accomplished by recreating model membranes that approximate the structure of cellular membranes in a controlled environment, formed using self-assembly principles. The selected method for membrane creation influences the properties of the membrane assembly, including their response to electric fields used for characterizing transmembrane exchanges. When these self-assembled model membranes are combined with electrophysiology, it is possible to exploit their non-physiological mechanics to enable additional measurements of membrane interactions and phenomena. This review describes several common model membranes including liposomes, pore-spanning membranes, solid supported membranes, and emulsion-based membranes, emphasizing their varying structure due to the selected mode of production. Next, electrophysiology techniques that exploit these structures are discussed, including conductance measurements, electrowetting and electrocompression analysis, and electroimpedance spectroscopy. The focus of this review is linking each membrane assembly technique to the properties of the resulting membrane, discussing how these properties enable alternative electrophysiological approaches to measuring membrane characteristics and interactions.
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Affiliation(s)
| | - Eric Freeman
- School of Environmental, Civil, Agricultural and Mechanical Engineering, College of Engineering, University of Georgia, Athens, GA 30602, USA;
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2
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Impedance characterization of biocompatible hydrogel suitable for biomimetic lipid membrane applications. Electrochim Acta 2021. [DOI: 10.1016/j.electacta.2021.137917] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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3
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Kang X, Alibakhshi MA, Wanunu M. One-Pot Species Release and Nanopore Detection in a Voltage-Stable Lipid Bilayer Platform. NANO LETTERS 2019; 19:9145-9153. [PMID: 31724865 DOI: 10.1021/acs.nanolett.9b04446] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Biological nanopores have been used as powerful platforms for label-free detection and identification of a range of biomolecules for biosensing applications and single molecule biophysics studies. Nonetheless, high limit of detection (LOD) of analytes due to inefficient biomolecular capture into biological nanopores at low voltage poses practical limits on their biosensing efficacy. Several approaches have been proposed to improve the voltage stability of the membrane, including polymerization and hydrogel coating, however, these compromise the lipid fluidity. Here, we developed a chip-based platform that can be massively produced on a wafer scale that is capable of sustaining high voltages of 350 mV with comparable membrane areas to traditional systems. Using this platform, we demonstrate sensing of DNA hairpins in α-hemolysin nanopores at the nanomolar regime under high voltage. Further, we have developed a workflow for one-pot enzymatic release of DNA hairpins with different stem lengths from magnetic microbeads, followed by multiplexed nanopore-based quantification of the hairpins within minutes, paving the way for novel nanopore-based multiplexed biosensing applications.
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4
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Fonseka M, Liang B, Orosz KS, Jones IW, Hall HK, Christie HS, Aspinwall CA, Saavedra SS. Nanodomain Formation in Planar Supported Lipid Bilayers Composed of Fluid and Polymerized Dienoyl Lipids. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:12483-12491. [PMID: 31454251 PMCID: PMC7719349 DOI: 10.1021/acs.langmuir.9b02101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Polymerization of synthetic phospholipid monomers has been widely used to enhance the stability of lipid membranes in applications such as membrane-based biosensing, where the inherent instability of fluid-phase lipid bilayers can be problematic. However, lipid polymerization typically decreases membrane fluidity, which may be required to maintain the activity of reconstituted integral proteins and peptides. Prior work has shown that a bilayer composed of binary mixtures of poly(lipid) and fluid lipid exhibits enhanced stability and supports the function of incorporated biomolecules. This work examines the structural basis of these findings using planar supported lipid bilayers (PSLBs) composed of binary mixtures of a polymerizable lipid, 1,2-bis[10-(2',4'-hexadienoloxy)decanoyl]-sn-glycero-3-phosphocholine (bis-SorbPC), and a nonpolymerizable lipid, 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC). Fluorescence recovery after photobleaching (FRAP) measurements showed that long-range lateral diffusion was minimally affected when the poly(lipid) mole ratio was ≤0.7. Atomic force microscopy, used to examine phase segregation in these PSLBs, showed that DPhPC forms a continuous lipid matrix that is 0.2-0.4 nm thicker than the island-like poly(bis-SorbPC) domains, with lateral dimensions of ≤200 nm. The nanoscale phase segregation allows for long-range lateral diffusion of lipid probes in the DPhPC matrix. The combination of fluidity and stability in these materials should make them useful in membrane-based biosensing applications.
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Affiliation(s)
- Malithi Fonseka
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA
| | - Boying Liang
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA
| | - Kristina S. Orosz
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA
| | - Ian W. Jones
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA
| | - H. K. Hall
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA
| | - Hamish S. Christie
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA
| | - Craig A. Aspinwall
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA
- BIO5 Institute and Department of Biomedical Engineering, University of Arizona, Tucson, AZ, 85721, USA
| | - S. Scott Saavedra
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, USA
- BIO5 Institute and Department of Biomedical Engineering, University of Arizona, Tucson, AZ, 85721, USA
- Author to whom correspondence should be addressed.
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Beltramo PJ, Van Hooghten R, Vermant J. Millimeter-area, free standing, phospholipid bilayers. SOFT MATTER 2016; 12:4324-31. [PMID: 27050618 DOI: 10.1039/c6sm00250a] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Minimal model biomembrane studies have the potential to unlock the fundamental mechanisms of cellular function that govern the processes upon which life relies. However, existing methods to fabricate free-standing model membranes currently have significant limitations. Bilayer sizes are often tens of micrometers, decoupling curvature or substrate effects, orthogonal control over tension, and solvent exchange combined with microscopy techniques is not possible, which restricts the studies that can be performed. Here, we describe a versatile platform to generate free standing, planar, phospholipid bilayers with millimeter scale areas. The technique relies on an adapted thin-film balance apparatus allowing for the dynamic control of the nucleation and growth of a planar black lipid membrane in the center of an orifice surrounded by microfluidic channels. Success is demonstrated using several different lipid types, including mixtures that show the same temperature dependent phase separation as existing protocols, moreover, membranes are highly stable. Two advantages unique to the proposed method are the dynamic control of the membrane tension and the possibility to make extremely large area membranes. We demonstrate this by showing how a block polymer, F68, used in drug delivery increases the membrane compliance. Together, the results demonstrate a new paradigm for studying the mechanics, structure, and function of model membranes.
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Affiliation(s)
- Peter J Beltramo
- Department of Materials, ETH Zürich, Vladimir-Prelog-Weg 5, 8093 Zürich, Switzerland.
| | - Rob Van Hooghten
- Department of Chemical Engineering, KU Leuven, Celestijnenlaan 200F, 3001 Heverlee, Belgium
| | - Jan Vermant
- Department of Materials, ETH Zürich, Vladimir-Prelog-Weg 5, 8093 Zürich, Switzerland.
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del Rio Martinez JM, Zaitseva E, Petersen S, Baaken G, Behrends JC. Automated formation of lipid membrane microarrays for ionic single-molecule sensing with protein nanopores. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2015; 11:119-125. [PMID: 25115837 DOI: 10.1002/smll.201402016] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Indexed: 06/03/2023]
Abstract
Efficient use of membrane protein nanopores in ionic single-molecule sensing requires technology for the reliable formation of suspended molecular membranes densely arrayed in formats that allow high-resolution electrical recording. Here, automated formation of bimolecular lipid layers is shown using a simple process where a poly(tetrafluoroethylene)-coated magnetic bar is remotely actuated to perform a turning motion, thereby spreading phospholipid in organic solvent on a nonpolar surface containing a <1 mm(2) 4 × 4 array of apertures with embedded microelectrodes (microelectrode cavity array). Parallel and high-resolution single-molecule detection by single nanopores is demonstrated on the resulting bilayer arrays, which are shown to form by a classical but very rapid self-assembly process. The technique provides a robust and scalable solution for the problem of reliable, automated formation of multiple independent lipid bilayers in a dense microarray format, while preserving the favorable electrical properties of the microelectrode cavity array.
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Affiliation(s)
- Juan M del Rio Martinez
- Laboratory for Membrane Physiology and -Technology, Department of Physiology, University of Freiburg, Hermann-Herder-Str. 7, 79104, Freiburg, Germany
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Ryu H, Choi S, Park J, Yoo YE, Yoon JS, Seo YH, Kim YR, Kim SM, Jeon TJ. Automated Lipid Membrane Formation Using a Polydimethylsiloxane Film for Ion Channel Measurements. Anal Chem 2014; 86:8910-5. [DOI: 10.1021/ac501397t] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hyunil Ryu
- Department
of Biological Engineering, Inha University, Incheon, 402-751, South Korea
- Biohybrid
Systems Research Center (BSRC), Inha University, Incheon, 402-751, South Korea
| | - Sangbaek Choi
- Department
of Biological Engineering, Inha University, Incheon, 402-751, South Korea
- Biohybrid
Systems Research Center (BSRC), Inha University, Incheon, 402-751, South Korea
| | - Joongjin Park
- Department
of Biological Engineering, Inha University, Incheon, 402-751, South Korea
- Biohybrid
Systems Research Center (BSRC), Inha University, Incheon, 402-751, South Korea
| | - Yeong-Eun Yoo
- Nano-Mechanical
Systems Research Division, Korea Institute of Machinery and Materials, Daejeon, 305-343, South Korea
| | - Jae Sung Yoon
- Nano-Mechanical
Systems Research Division, Korea Institute of Machinery and Materials, Daejeon, 305-343, South Korea
| | - Young Ho Seo
- Department
of Mechanical and Mechatronics Engineering, Kangwon National University, Chuncheon, 200-701, South Korea
| | - Young-Rok Kim
- Institute
of Life Science and Resources and Department of Food Science and Biotechnology, Kyung Hee University, Yongin, 472-864, South Korea
| | - Sun Min Kim
- Biohybrid
Systems Research Center (BSRC), Inha University, Incheon, 402-751, South Korea
- Department
of Mechanical Engineering, Inha University, Incheon, 402-751, Republic of Korea
| | - Tae-Joon Jeon
- Department
of Biological Engineering, Inha University, Incheon, 402-751, South Korea
- Biohybrid
Systems Research Center (BSRC), Inha University, Incheon, 402-751, South Korea
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Mayer M, Yang J. Engineered ion channels as emerging tools for chemical biology. Acc Chem Res 2013; 46:2998-3008. [PMID: 23932142 DOI: 10.1021/ar400129t] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Over the last 25 years, researchers have developed exogenously expressed, genetically engineered, semi-synthetic, and entirely synthetic ion channels. These structures have sufficient fidelity to serve as unique tools that can reveal information about living organisms. One of the most exciting success stories is optogenetics: the use of light-gated channels to trigger action potentials in specific neurons combined with studies of the response from networks of cells or entire live animals. Despite this breakthrough, the use of molecularly engineered ion channels for studies of biological systems is still in its infancy. Historically, researchers studied ion channels in the context of their own function in single cells or in multicellular signaling and regulation. Only recently have researchers considered ion channels and pore-forming peptides as responsive tools to report on the chemical and physical changes produced by other biochemical processes and reactions. This emerging class of molecular probes has a number of useful characteristics. For instance, these structures can greatly amplify the signal of chemical changes: the binding of one molecule to a ligand-gated ion channel can result in flux of millions of ions across a cell membrane. In addition, gating occurs on sub-microsecond time scales, resulting in fast response times. Moreover, the signal is complementary to existing techniques because the output is ionic current rather than fluorescence or radioactivity. And finally, ion channels are also localized at the membrane of cells where essential processes such as signaling and regulation take place. This Account highlights examples, mostly from our own work, of uses of ion channels and pore-forming peptides such as gramicidin in chemical biology. We discuss various strategies for preparing synthetically tailored ion channels that range from de novo designed synthetic molecules to genetically engineered or simply exogenously expressed or reconstituted wild-type channels. Next we consider aspects of experimental design by comparing various membrane environments or systems that make it possible to quantify the response of ion channels to biochemical processes of interest. We present applications of ion channels to answer questions in chemical biology, and propose potential future developments and applications of these single molecule probes. Finally we discuss the hurdles that impede the routine use of ion channel probes in biochemistry and cell biology laboratories and developments and strategies that could overcome these problems. Optogenetics has facilitated breakthroughs in neuroscience, and these results give a dramatic idea of what may lie ahead for designed ion channels as a functional class of molecular probes. If researchers can improve molecular engineering to increase ion channel versatility and can overcome the barriers to collaborating across disciplines, we conclude that these structures could have tremendous potential as novel tools for chemical biology studies.
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Affiliation(s)
- Michael Mayer
- Department of Chemical Engineering and Department of Biomedical Engineering, University of Michigan, 1101 Beal Avenue, Ann Arbor, Michigan 48109-2110, United States
| | - Jerry Yang
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, MC 0358, La Jolla, California 92093-0358, United States
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9
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Leptihn S, Castell OK, Cronin B, Lee EH, Gross LCM, Marshall DP, Thompson JR, Holden M, Wallace MI. Constructing droplet interface bilayers from the contact of aqueous droplets in oil. Nat Protoc 2013; 8:1048-57. [DOI: 10.1038/nprot.2013.061] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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10
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Tantawi KH, Cerro R, Berdiev B, Martin MED, Montes FJ, Patel D, Williams JD. Investigation of transmembrane protein fused in lipid bilayer membranes supported on porous silicon. J Med Eng Technol 2012; 37:28-34. [DOI: 10.3109/03091902.2012.733056] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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11
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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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12
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Nanopore sensors: From hybrid to abiotic systems. Biosens Bioelectron 2012; 38:1-10. [DOI: 10.1016/j.bios.2012.05.013] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Revised: 05/02/2012] [Accepted: 05/12/2012] [Indexed: 11/22/2022]
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Padermshoke A, Konishi S, Ara M, Tada H, Ishibashi TA. Novel SiO2-deposited CaF2 substrate for vibrational sum-frequency generation (SFG) measurements of chemisorbed monolayers in an aqueous environment. APPLIED SPECTROSCOPY 2012; 66:711-718. [PMID: 22732544 DOI: 10.1366/11-06583] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A novel SiO(2)-deposited CaF(2) (SiO(2)/CaF(2)) substrate for measuring vibrational sum-frequency generation (SFG) spectra of silane-based chemisorbed monolayers in aqueous media has been developed. The substrate is suitable for silanization and transparent over a broad range of the infrared (IR) probe. The present work demonstrates the practical application of the SiO(2)/CaF(2) substrate and, to our knowledge, the first SFG spectrum at the solid/water interface of a silanized monolayer observed over the IR fingerprint region (1780-1400 cm(-1)) using a back-side probing geometry. This new substrate can be very useful for SFG studies of various chemisorbed organic molecules, particularly biological compounds, in aqueous environments.
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Affiliation(s)
- Adchara Padermshoke
- Center for Quantum Life Sciences, Hiroshima University, Higashi-Hiroshima, Japan
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14
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Claesson M, Frost R, Svedhem S, Andersson M. Pore spanning lipid bilayers on mesoporous silica having varying pore size. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:8974-8982. [PMID: 21650458 DOI: 10.1021/la201411b] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Synthetic lipid bilayers have similar properties as cell membranes and have been shown to be of great use in the development of novel biomimicry devices. In this study, lipid bilayer formation on mesoporous silica of varying pore size, 2, 4, and 6 nm, has been investigated using quartz crystal microbalance with dissipation monitoring (QCM-D), fluorescent recovery after photo bleaching (FRAP), and atomic force microscopy (AFM). The results show that pore-spanning lipid bilayers were successfully formed regardless of pore size. However, the mechanism of the bilayer formation was dependent on the pore size, and lower surface coverages of adsorbed lipid vesicles were required on the surface having the smallest pores. A similar trend was observed for the lateral diffusion coefficient (D) of fluorescently labeled lipid molecules in the membrane, which was lowest on the surface having the smallest pores and increased with the pore size. All of the pore size dependent observations are suggested to be due to the hydrophilicity of the surface, which decreases with increased pore size.
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Affiliation(s)
- Maria Claesson
- Department of Chemical and Biological Engineering, Chalmers University of Technology, Göteborg, Sweden
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15
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Bilayer lipid membranes supported on Teflon filters: A functional environment for ion channels. Biosens Bioelectron 2011; 26:3127-35. [DOI: 10.1016/j.bios.2010.12.013] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Revised: 12/05/2010] [Accepted: 12/07/2010] [Indexed: 11/18/2022]
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16
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Heitz BA, Xu J, Jones IW, Keogh JP, Comi TJ, Hall HK, Aspinwall CA, Saavedra SS. Polymerized planar suspended lipid bilayers for single ion channel recordings: comparison of several dienoyl lipids. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:1882-90. [PMID: 21226498 PMCID: PMC3043114 DOI: 10.1021/la1025944] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The stabilization of suspended planar lipid membranes, or black lipid membranes (BLMs), through polymerization of mono- and bis-functionalized dienoyl lipids was investigated. Electrical properties, including capacitance, conductance, and dielectric breakdown voltage, were determined for BLMs composed of mono-DenPC, bis-DenPC, mono-SorbPC, and bis-SorbPC both prior to and following photopolymerization, with diphytanoyl phosphocholine (DPhPC) serving as a control. Poly(lipid) BLMs exhibited significantly longer lifetimes and increased the stability of air-water transfers. BLM stability followed the order bis-DenPC > mono-DenPC ≈ mono-SorbPC > bis-SorbPC. The conductance of bis-SorbPC BLMs was significantly higher than that of the other lipids, which is attributed to a high density of hydrophilic pores, resulting in relatively unstable membranes. The use of poly(lipid) BLMs as matrices for supporting the activity of an ion channel protein (IC) was explored using α-hemolysin (α-HL), a model IC. Characteristic i-V plots of α-HL were maintained following photopolymerization of bis-DenPC, mono-DenPC, and mono-SorbPC, demonstrating the utility of these materials for preparing more durable BLMs for single-channel recordings of reconstituted ICs.
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Affiliation(s)
- Benjamin A. Heitz
- Department of Chemistry and Biochemistry and BIO5 Institute, University of Arizona, 1306 E. University Blvd., Tucson, AZ 85721
| | - Juhua Xu
- Department of Chemistry and Biochemistry and BIO5 Institute, University of Arizona, 1306 E. University Blvd., Tucson, AZ 85721
| | - Ian W. Jones
- Department of Chemistry and Biochemistry and BIO5 Institute, University of Arizona, 1306 E. University Blvd., Tucson, AZ 85721
| | - John P. Keogh
- Department of Chemistry and Biochemistry and BIO5 Institute, University of Arizona, 1306 E. University Blvd., Tucson, AZ 85721
| | - Troy J. Comi
- Department of Chemistry and Biochemistry and BIO5 Institute, University of Arizona, 1306 E. University Blvd., Tucson, AZ 85721
| | - Henry K. Hall
- Department of Chemistry and Biochemistry and BIO5 Institute, University of Arizona, 1306 E. University Blvd., Tucson, AZ 85721
| | - Craig A. Aspinwall
- Department of Chemistry and Biochemistry and BIO5 Institute, University of Arizona, 1306 E. University Blvd., Tucson, AZ 85721
| | - S. Scott Saavedra
- Department of Chemistry and Biochemistry and BIO5 Institute, University of Arizona, 1306 E. University Blvd., Tucson, AZ 85721
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Heitz BA, Jones IW, Hall HK, Aspinwall CA, Saavedra SS. Fractional polymerization of a suspended planar bilayer creates a fluid, highly stable membrane for ion channel recordings. J Am Chem Soc 2010; 132:7086-93. [PMID: 20441163 DOI: 10.1021/ja100245d] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Suspended planar lipid membranes (or black lipid membranes (BLMs)) are widely used for studying reconstituted ion channels, although they lack the chemical and mechanical stability needed for incorporation into high-throughput biosensors and biochips. Lipid polymerization enhances BLM stability but is incompatible with ion channel function when membrane fluidity is required. Here, we demonstrate the preparation of a highly stable BLM that retains significant fluidity by using a mixture of polymerizable and nonpolymerizable phospholipids. Alamethicin, a voltage-gated peptide channel for which membrane fluidity is required for activity, was reconstituted into mixed BLMs prepared using bis-dienoyl phosphatidylcholine (bis-DenPC) and diphytanoyl phosphatidylcholine (DPhPC). Polymerization yielded BLMs that retain the fluidity required for alamethicin activity yet are stable for several days as compared to a few hours prior to polymerization. Thus, these polymerized, binary composition BLMs feature both fluidity and long-term stability.
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Affiliation(s)
- Benjamin A Heitz
- Department of Chemistry and Biochemistry and BIO5 Institute, University of Arizona, Tucson, Arizona 85721, USA
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18
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Majd S, Yusko EC, Billeh YN, Macrae MX, Yang J, Mayer M. Applications of biological pores in nanomedicine, sensing, and nanoelectronics. Curr Opin Biotechnol 2010; 21:439-76. [PMID: 20561776 PMCID: PMC3121537 DOI: 10.1016/j.copbio.2010.05.002] [Citation(s) in RCA: 237] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2010] [Revised: 05/03/2010] [Accepted: 05/06/2010] [Indexed: 12/29/2022]
Abstract
Biological protein pores and pore-forming peptides can generate a pathway for the flux of ions and other charged or polar molecules across cellular membranes. In nature, these nanopores have diverse and essential functions that range from maintaining cell homeostasis and participating in cell signaling to activating or killing cells. The combination of the nanoscale dimensions and sophisticated - often regulated - functionality of these biological pores make them particularly attractive for the growing field of nanobiotechnology. Applications range from single-molecule sensing to drug delivery and targeted killing of malignant cells. Potential future applications may include the use of nanopores for single strand DNA sequencing and for generating bio-inspired, and possibly, biocompatible visual detection systems and batteries. This article reviews the current state of applications of pore-forming peptides and proteins in nanomedicine, sensing, and nanoelectronics.
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Affiliation(s)
- Sheereen Majd
- Department of Biomedical Engineering, University of Michigan, 1101 Beal Avenue, Ann Arbor, Michigan 48109-2110, USA
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