1
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Zafar MN, Pitt WG, Husseini GA. Encapsulation and release of calcein from herceptin-conjugated eLiposomes. Heliyon 2024; 10:e27882. [PMID: 38524567 PMCID: PMC10958368 DOI: 10.1016/j.heliyon.2024.e27882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2023] [Revised: 03/06/2024] [Accepted: 03/07/2024] [Indexed: 03/26/2024] Open
Abstract
Achieving an optimal therapeutic level is crucial in effectively eradicating cancer cells during treatment. However, conventional chemotherapy-associated systemic administration of anticancer agents leads to many side effects. To achieve the desired control over the target site, active targeting of HER2-positive breast cancer cells can be achieved by conjugating liposomal vesicles with Human Epidermal growth factor Receptor 2 (HER2) and inducing release of the encapsulated drug using ultrasound. To further enhance the delivery efficiency, nanoemulsion droplets exhibiting responsiveness to low-frequency ultrasound are encapsulated within these lipid vesicles. In this study, we prepared four different liposomal formulations, namely pegylated liposomes, emulsion liposomes (eLiposomes), HER-conjugated liposomes, and HER-conjugated eLiposomes, each loaded with calcein and subjected to a thorough characterization process. Their sizes, phospholipid concentration, and amount of antibody conjugation were compared and analyzed. Cryogenic transmission electron microscopy was used to confirm the encapsulation of nanoemulsion droplets within the liposomes. The drug-releasing performance of Herceptin-conjugated eLiposomes was found to surpass that of other liposomal formulations with a notably higher calcein release and established it as a highly effective nanocarrier. The study showcases the efficacy of calcein-loaded and Herceptin-conjugated eLiposomes, which demonstrate rapid and efficient drug release among other liposomal formulations when subjected to ultrasound. This discovery paves the way for a more targeted, efficient, and humane approach to cancer therapy.
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Affiliation(s)
- Mah Noor Zafar
- Biomedical Engineering Program, College of Engineering, American University of Sharjah, Sharjah, P.O. Box. 26666, United Arab Emirates
| | - William G. Pitt
- Department of Chemical Engineering, Brigham Young University, Provo, UT, 84602, USA
| | - Ghaleb A. Husseini
- Materials Science and Engineering Ph.D. Program, College of Arts and Sciences, American University of Sharjah, Sharjah, P.O. Box. 26666, United Arab Emirates
- Department of Chemical and Biological Engineering, College of Engineering, American University of Sharjah, Sharjah, P.O. Box 26666, United Arab Emirates
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2
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Rashmi, Hasheminejad H, Herziger S, Mirzaalipour A, Singh AK, Netz RR, Böttcher C, Makki H, Sharma SK, Haag R. Supramolecular Engineering of Alkylated, Fluorinated, and Mixed Amphiphiles. Macromol Rapid Commun 2022; 43:e2100914. [PMID: 35239224 DOI: 10.1002/marc.202100914] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Revised: 02/08/2022] [Indexed: 11/11/2022]
Abstract
The rational design of perfluorinated amphiphiles to control the supramolecular aggregation in aqueous medium is still a key challenge for the engineering of supramolecular architectures. Here we present the synthesis and physical properties of six novel non-ionic amphiphiles. We also studied the effect of mixed alkylated and perfluorinated segments in a single amphiphile and compared it with only alkylated and perfluorinated units. To explore their morphological behavior in aqueous medium, we used dynamic light scattering (DLS) and cryo-TEM/EM measurements. We further confirmed their assembly mechanisms with theoretical investigations, using the Martini model to perform large-scale coarse-grained molecular dynamics simulations. These novel synthesized amphiphiles offer a greater and more systematic understanding of how perfluorinated systems assemble in aqueous medium and suggest new directions for rational designing of new amphiphilic systems and interpreting their assembly process. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Rashmi
- Department of Chemistry, University of Delhi, Delhi, 110 007, India.,Institut für Chemie und Biochemie, Organische Chemie, Freie Universität Berlin, Takustraße 3, Berlin, 14195, Germany
| | - Hooman Hasheminejad
- Department of Polymer and Color Engineering, Amirkabir University of Technology, Tehran, Iran
| | - Svenja Herziger
- Forschungszentrum für Elektronenmikroskopie, Institut für Chemie und Biochemie, Freie Universität Berlin, Fabeckstraße 36a, Berlin, 14195, Germany
| | - Alireza Mirzaalipour
- Department of Polymer and Color Engineering, Amirkabir University of Technology, Tehran, Iran
| | - Abhishek K Singh
- Institut für Chemie und Biochemie, Organische Chemie, Freie Universität Berlin, Takustraße 3, Berlin, 14195, Germany
| | - Roland R Netz
- Freie Universität Berlin, Fachbereich Physik, Berlin, 14195, Germany
| | - Christoph Böttcher
- Forschungszentrum für Elektronenmikroskopie, Institut für Chemie und Biochemie, Freie Universität Berlin, Fabeckstraße 36a, Berlin, 14195, Germany
| | - Hesam Makki
- Department of Polymer and Color Engineering, Amirkabir University of Technology, Tehran, Iran
| | - Sunil K Sharma
- Department of Chemistry, University of Delhi, Delhi, 110 007, India
| | - Rainer Haag
- Institut für Chemie und Biochemie, Organische Chemie, Freie Universität Berlin, Takustraße 3, Berlin, 14195, Germany
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3
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Timmins LM, Burr AM, Carroll K, Keefe R, Teryek M, Cantolupo LJ, van der Loo JCM, Heathman TR, Gormley A, Smith D, Parekkadan B. Selecting a Cell Engineering Methodology During Cell Therapy Product Development. Cell Transplant 2021; 30:9636897211003022. [PMID: 34013781 PMCID: PMC8145581 DOI: 10.1177/09636897211003022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 02/16/2021] [Accepted: 02/25/2021] [Indexed: 12/22/2022] Open
Abstract
When considering the development pathway for a genetically modified cell therapy product, it is critically important that the product is engineered consistent with its intended human use. For scientists looking to develop and commercialize a new technology, the decision to select a genetic modification method depends on several practical considerations. Whichever path is chosen, the developer must understand the key risks and potential mitigations of the cell engineering approach. The developer should also understand the clinical implications: permanent/memory establishment versus transient expression, and clinical manufacturing considerations when dealing with transplantation of genetically engineered cells. This review covers important topics for mapping out a strategy for developers of new cell-based therapeutics. Biological, technological, manufacturing, and clinical considerations are all presented to map out development lanes for the initiation and risk management of new gene-based cell therapeutic products for human use.
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Affiliation(s)
- Lauren M. Timmins
- Department of Biomedical Engineering, Rutgers University, Piscataway Township, NJ, USA
| | - Alexandra M. Burr
- Department of Biomedical Engineering, Rutgers University, Piscataway Township, NJ, USA
| | - Kristina Carroll
- Department of Biomedical Engineering, Rutgers University, Piscataway Township, NJ, USA
- Precision Biosciences, Durham, NC, USA
| | | | - Matthew Teryek
- Department of Biomedical Engineering, Rutgers University, Piscataway Township, NJ, USA
| | | | - Johannes C. M. van der Loo
- The Raymond G. Perelman Center for Cellular and Molecular Therapeutics, The Children’s Hospital of Philadelphia, Philadelphia, PA, USA
| | | | - Adam Gormley
- Department of Biomedical Engineering, Rutgers University, Piscataway Township, NJ, USA
| | - David Smith
- Minaris Regenerative Medicine, LLC, Allendale, NJ, USA
| | - Biju Parekkadan
- Department of Biomedical Engineering, Rutgers University, Piscataway Township, NJ, USA
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4
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Wang Z, Sun S, Lyu Q, Cheng M, Wang H, Li C, Sha H, Faller R, Hu S. Harnessed Dopant Block Copolymers Assist Decorating Membrane Pores: A Dissipative Particle Dynamics Study. Macromol Rapid Commun 2019; 41:e1900561. [PMID: 31859398 DOI: 10.1002/marc.201900561] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 11/21/2019] [Indexed: 12/20/2022]
Abstract
Self-assembly of asymmetric block copolymers (BCPs) around active pore edges has emerged as an important strategy to produce smart membranes with tunable pathways for solute transport. However, thus far, it is still challenging to manipulate pore shape and functionality for directional transformation under external stimuli. Here, a versatile strategy by mesoscale simulations to design stimuli-responsive pores with various edge decorations in hybrid membranes is reported. Dopant BCPs are used as decorators to stabilize pore edges and extend their function in reconfiguring pores in response to repeated membrane stretching/shrinking caused by external stimuli. The decoration morphologies are predictable since the assemblies of dopant BCPs around pore edges are closely related to their self-assemblies in solution. The coassembly between different BCPs in the hybrid membrane for the control of pore morphology is featured, and the parameter settings, including block incompatibility and molecular architecture for the construction of a specific pore, are determined. Results show that harnessed dopant BCPs in the hybrid membrane can enhance pore formation and induce directional pore shape and functionality transformation. Diversified pore decorations exhibit potential that can be further explored in selective solute transport and the design of stimuli-responsive smart nanodevices.
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Affiliation(s)
- Zhikun Wang
- School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266580, China
| | - Shuangqing Sun
- School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266580, China.,Institute of Advanced Materials, China University of Petroleum (East China), Qingdao, 266580, China
| | - Qiang Lyu
- School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266580, China
| | - Meng Cheng
- School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266580, China
| | - Hongbing Wang
- School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266580, China
| | - Chunling Li
- School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266580, China.,Institute of Advanced Materials, China University of Petroleum (East China), Qingdao, 266580, China
| | - Haoyan Sha
- Department of Chemical Engineering, University of California Davis, Davis, CA, 95616, USA
| | - Roland Faller
- Department of Chemical Engineering, University of California Davis, Davis, CA, 95616, USA
| | - Songqing Hu
- School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266580, China.,Institute of Advanced Materials, China University of Petroleum (East China), Qingdao, 266580, China
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5
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Ting CL, Awasthi N, Müller M, Hub JS. Metastable Prepores in Tension-Free Lipid Bilayers. PHYSICAL REVIEW LETTERS 2018; 120:128103. [PMID: 29694074 DOI: 10.1103/physrevlett.120.128103] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Indexed: 06/08/2023]
Abstract
The formation and closure of aqueous pores in lipid bilayers is a key step in various biophysical processes. Large pores are well described by classical nucleation theory, but the free-energy landscape of small, biologically relevant pores has remained largely unexplored. The existence of small and metastable "prepores" was hypothesized decades ago from electroporation experiments, but resolving metastable prepores from theoretical models remained challenging. Using two complementary methods-atomistic simulations and self-consistent field theory of a minimal lipid model-we determine the parameters for which metastable prepores occur in lipid membranes. Both methods consistently suggest that pore metastability depends on the relative volume ratio between the lipid head group and lipid tails: lipids with a larger head-group volume fraction (or shorter saturated tails) form metastable prepores, whereas lipids with a smaller head-group volume fraction (or longer unsaturated tails) form unstable prepores.
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Affiliation(s)
- Christina L Ting
- Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
| | - Neha Awasthi
- University of Goettingen, Institute for Microbiology and Genetics, 37077 Göttingen, Germany
- Göttingen Center for Molecular Biosciences, 37077 Göttingen, Germany
| | - Marcus Müller
- University of Goettingen, Institute for Theoretical Physics, 37077 Göttingen, Germany
| | - Jochen S Hub
- University of Goettingen, Institute for Microbiology and Genetics, 37077 Göttingen, Germany
- Göttingen Center for Molecular Biosciences, 37077 Göttingen, Germany
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6
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Ilton M, DiMaria C, Dalnoki-Veress K. Direct Measurement of the Critical Pore Size in a Model Membrane. PHYSICAL REVIEW LETTERS 2016; 117:257801. [PMID: 28036217 DOI: 10.1103/physrevlett.117.257801] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Indexed: 05/27/2023]
Abstract
We study pore nucleation in a model membrane system, a freestanding polymer film. Nucleated pores smaller than a critical size close, while pores larger than the critical size grow. Holes of varying size were purposefully prepared in liquid polymer films, and their evolution in time was monitored using optical and atomic force microscopy to extract a critical radius. The critical radius scales linearly with film thickness for a homopolymer film. The results agree with a simple model which takes into account the energy cost due to surface area at the edge of the pore. The energy cost at the edge of the pore is experimentally varied by using a lamellar-forming diblock copolymer membrane. The underlying molecular architecture causes increased frustration at the pore edge resulting in an enhanced cost of pore formation.
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Affiliation(s)
- Mark Ilton
- Department of Physics & Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada
| | - Christian DiMaria
- Department of Physics & Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada
| | - Kari Dalnoki-Veress
- Department of Physics & Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada
- Laboratoire de Physico-Chimie Théorique, UMR CNRS Gulliver 7083, ESPCI ParisTech, PSL Research University, 75005 Paris, France
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7
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Dehghan A, Pastor KA, Shi AC. Line tension of multicomponent bilayer membranes. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 91:022713. [PMID: 25768537 DOI: 10.1103/physreve.91.022713] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Indexed: 06/04/2023]
Abstract
The line tension or edge energy of bilayer membranes self-assembled from binary amphiphilic molecules is studied using self-consistent-field theory (SCFT). Specifically, solutions of the SCFT equations corresponding to an infinite membrane with a circular pore, or an open membrane, are obtained for a coarse-grained model in which the amphiphilic species and hydrophilic solvents are represented by ABandED diblock copolymers and C homopolymers, respectively. The edge energy of the membrane is extracted from the free energy of the open membranes. Results for membranes composed of mixtures of symmetric and cone- or inverse cone-shaped amphiphilic molecules with neutral and/or repulsive interactions are obtained and analyzed. It is observed that an increase in the concentration of the cone-shaped species leads to a decrease of the line tension. In contrast, adding inverse cone-shaped copolymers results in an increase of the line tension. Furthermore, the density profile of the copolymers reveals that the line tension is regulated by the distribution of the amphiphiles at the bilayer edge.
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Affiliation(s)
- Ashkan Dehghan
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada L8S 4M1
| | - Kyle A Pastor
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada L8S 4M1
| | - An-Chang Shi
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada L8S 4M1
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8
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Choudhury CK, Kumar A, Roy S. Characterization of Conformation and Interaction of Gene Delivery Vector Polyethylenimine with Phospholipid Bilayer at Different Protonation State. Biomacromolecules 2013; 14:3759-68. [DOI: 10.1021/bm4011408] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
| | - Abhinaw Kumar
- Department
of Chemistry, Indian Institute of Science Education and Research, Pune 411008, India
| | - Sudip Roy
- Physical
Chemistry Division, National Chemical Laboratory, Pune 411008, India
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9
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Lattin JR, Pitt WG, Belnap DM, Husseini GA. Ultrasound-induced calcein release from eLiposomes. ULTRASOUND IN MEDICINE & BIOLOGY 2012; 38:2163-73. [PMID: 23062373 DOI: 10.1016/j.ultrasmedbio.2012.08.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Revised: 07/28/2012] [Accepted: 08/01/2012] [Indexed: 05/25/2023]
Abstract
Ultrasound is explored as a method of inducing the release of encapsulated materials from eLiposomes, defined as liposomes containing emulsion droplets. Emulsions were formed using perfluorohexane and perfluoropentane. eLiposomes were formed by folding interdigitated lipid sheets into closed vesicles around the emulsion droplets. Cryogenic transmission electron microscopy was used to verify droplet encapsulation. Self-quenched calcein was also encapsulated inside the vesicles. A fluorometer was used to measure baseline fluorescence, calcein release after ultrasound exposure, and total release from the vesicles. eLiposome samples released 3 to 5 times more of the encapsulated calcein than did controls when exposed to 20-kHz ultrasound. Calcein release increased with exposure time and intensity of ultrasound. eLiposomes with large (400 nm) droplets produced more calcein release than small (100 nm) droplets. These observations suggest that the emulsions are vaporized by ultrasound and that the Laplace pressure in the emulsions has an effect on droplet vaporization.
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Affiliation(s)
- James R Lattin
- Chemical Engineering Department, Brigham Young University, Provo, UT 84602, USA
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10
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Javadi M, Pitt WG, Belnap DM, Tsosie NH, Hartley JM. Encapsulating nanoemulsions inside eLiposomes for ultrasonic drug delivery. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:14720-9. [PMID: 22989347 DOI: 10.1021/la303464v] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
An eLiposome is a liposome encapsulating an emulsion nanodroplet and can be used for drug delivery. For example, therapeutic agents are encapsulated inside the eLiposomes, and the application of ultrasound can cause the emulsion droplet to change from liquid to gas, thus increasing the volume inside the vesicle and causing rupture and the release of the drug. In this research, two different methods were used to prepare eLiposomes. In the first method, emulsion droplets were made of perfluorohexane or perfluoropentane and stabilized with 1,2-dipalmitoyl-sn-glycero-3-phosphate. A layer of 1,2-dimyristoyl-sn-glycero-3-phosphocholine was dried in a round-bottomed flask. Then the emulsion suspension was added to the flask. As the suspension hydrated the phospholipids, they formed liposomes around the emulsions. In the second method, emulsions and liposomes were made separately, and then they were mixed using ultrasound. The advantage of this second method compared to the previous one is that eLiposomes can be made with fewer restrictions because of incompatible combinations of surfactants. Dynamic light scattering and transmission electron microscopy were used to measure the size of the emulsions, liposomes, and eLiposomes. The size of eLiposomes is appropriate for extravasation into tumors with malformed capillary beds. We hypothesize that ultrasound breaks open these eLiposomes. Both types of eLiposomes were constructed with folate attached via a poly(ethylene glycol) tether to induce endocytosis of the eLiposome. The latter eLiposomes were successfully used to deliver calcein as a model drug to HeLa cells.
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Affiliation(s)
- Marjan Javadi
- Chemical Engineering Department, Brigham Young University, Provo, Utah 84602, USA
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11
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Guo K, Li J. Exploration of the shapes of double-walled vesicles with a confined inner membrane. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:285103. [PMID: 21709351 DOI: 10.1088/0953-8984/23/28/285103] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We investigate double-walled vesicles as a simple model system for multi-vesicular structures, where the inner membrane is confined within the outer membrane. Various shapes of double-walled vesicles in two dimensions are obtained by means of our recently-developed discrete space variation method, and the shapes of each layer are found to be interdependent. Confined within the outer membrane, an inner membrane with a larger surface area always shows a cristae shape. As previous simulations and theoretical analyses of a single-walled vesicle have been done before, the geometric properties of double-walled vesicles, including the mean square radius of gyration and volume within the vesicle membrane, are studied in detail as functions of the pressure and surface area. It is found that due to the inter-space restriction of each layer, double-walled vesicles exhibit different behaviors compared with the previously-observed scaling laws of single-walled vesicles. It is straightforward to extend this study to more complicated and realistic biological systems, such as those including electrostatic interactions between membranes and solvent, phase separation, and cooperative interactions between multicomponent membranes.
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Affiliation(s)
- Kunkun Guo
- College of Materials Science and Engineering, Hunan University, Changsha, People's Republic of China.
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12
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Ting CL, Appelö D, Wang ZG. Minimum energy path to membrane pore formation and rupture. PHYSICAL REVIEW LETTERS 2011; 106:168101. [PMID: 21599415 PMCID: PMC3225126 DOI: 10.1103/physrevlett.106.168101] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2011] [Indexed: 05/27/2023]
Abstract
We combine dynamic self-consistent field theory with the string method to calculate the minimum energy path to membrane pore formation and rupture. In the regime where nucleation can occur on experimentally relevant time scales, the structure of the critical nucleus is between a solvophilic stalk and a locally thinned membrane. Classical nucleation theory fails to capture these molecular details and significantly overestimates the free energy barrier. Our results suggest that thermally nucleated rupture may be an important factor for the low rupture strains observed in lipid membranes.
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Affiliation(s)
- Christina L. Ting
- Biochemistry and Molecular Biophysics, California Institute of Technology, Pasadena, California 91125, USA
| | - Daniel Appelö
- Mechanical Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | - Zhen-Gang Wang
- Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
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13
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Norizoe Y, Daoulas KC, Müller M. Measuring excess free energies of self-assembled membrane structures. Faraday Discuss 2010; 144:369-91; discussion 445-81. [DOI: 10.1039/b901657k] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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14
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Roiter Y, Ornatska M, Rammohan AR, Balakrishnan J, Heine DR, Minko S. Interaction of lipid membrane with nanostructured surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:6287-6299. [PMID: 19466783 DOI: 10.1021/la900119a] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Tiny details of the phospholipid (DMPC) membrane morphology in close vicinity to nanostructured silica surfaces have been discovered in the atomic force microscopy experiments. The structural features of the silica surface were varied in the experiments by the deposition of silica nanoparticles of different diameter on plane and smooth silica substrates. It was found that, due to the barrier function of the lipid membrane, only particles larger than 22 nm in diameter with a smooth surface were completely enveloped by the lipid membrane. However, nanoparticles with bumpy surfaces (curvature diameter of bumps as that of particles <22 nm) were only partially enveloped by the lipid bilayer. For the range of nanostructure dimensions between 1.2 and 22 nm, the lipid membrane underwent structural rearrangements by forming pores (holes). The nanoparticles were accommodated into the pores but not enveloped by the lipid bilayer. The study also found that the lipid membrane conformed to the substrate with surface structures of dimensions less than 1.2 nm without losing the membrane integrity. The experimental results are in accord with the analytical free energy model, which describes the membrane coverage, and numerical simulations which evaluate adhesion of the membrane and dynamics as a function of surface topology. The results obtained in this study are useful for the selection of dimensions and shapes for drug-delivery cargo and for the substrate for supported lipid bilayers. They also help in qualitative understanding the role of length scales involved in the mechanisms of endocytosis and cytotoxicity of nanoparticles. These findings provide a new approach for patterning supported lipid membranes with well-defined features in the 1.2-22 nm range.
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Affiliation(s)
- Yuri Roiter
- Department of Chemistry and Biomolecular Science, NanoBio Laboratory (NABLAB), Clarkson University, Potsdam, New York 13699-5810, USA
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15
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Li S, Zheng F, Zhang X, Wang W. Stability and rupture of archaebacterial cell membrane: a model study. J Phys Chem B 2009; 113:1143-52. [PMID: 19123825 DOI: 10.1021/jp808079h] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
It is known that the thermoacidophilic archaebacterium Sulfolobus acidocaldarius can grow in hot springs at 65-80 degrees C and live in acidic environments (pH 2-3); however, the origin of its unusual thermal stability remains unclear. In this work, using a vesicle as a model, we study the thermal stability and rupture of archaebacterial cell membrane. We perform a simulation investigation of the structure-property relationship of monolayer membrane formed by bolaform lipids and compare it with that of bilayer membrane formed by monopolar lipids. The origin of the unusually thermal stability of archaebacterial cell and the mechanism for its rupture are presented in molecular details.
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Affiliation(s)
- Shuangyang Li
- Beijing University of Chemical Technology, Beijing 100029, China
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16
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Roiter Y, Ornatska M, Rammohan AR, Balakrishnan J, Heine DR, Minko S. Interaction of nanoparticles with lipid membrane. NANO LETTERS 2008; 8:941-944. [PMID: 18254602 DOI: 10.1021/nl080080l] [Citation(s) in RCA: 241] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
A nanoscale range of surface feature curvatures where lipid membranes lose integrity and form pores has been found experimentally. The pores were experimentally observed in the l-alpha-dimyristoyl phosphatidylcholine membrane around 1.2-22 nm polar nanoparticles deposited on mica surface. Lipid bilayer envelops or closely follows surface features with the curvatures outside of that region. This finding provides essential information for the understanding of nanoparticle-lipid membrane interaction, cytotoxicity, preparation of biomolecular templates and supported lipid membranes on rough and patterned surfaces.
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Affiliation(s)
- Yuri Roiter
- Department of Chemistry and Biomolecular Science, Clarkson University, Potsdam, NY 13699-5810, USA
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17
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Hallow DM, Seeger RA, Kamaev PP, Prado GR, LaPlaca MC, Prausnitz MR. Shear-induced intracellular loading of cells with molecules by controlled microfluidics. Biotechnol Bioeng 2008; 99:846-54. [PMID: 17879304 PMCID: PMC2883260 DOI: 10.1002/bit.21651] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This study tested the hypothesis that controlled flow through microchannels can cause shear-induced intracellular loading of cells with molecules. The overall goal was to design a simple device to expose cells to fluid shear stress and thereby increase plasma membrane permeability. DU145 prostate cancer cells were exposed to fluid shear stress in the presence of fluorescent cell-impermeant molecules by using a cone-and-plate shearing device or high-velocity flow through microchannels. Using a syringe pump, cell suspensions were flowed through microchannels of 50-300 microm diameter drilled through Mylar sheets using an excimer laser. As quantified by flow cytometry, intracellular uptake and loss of viability correlated with the average shear stress. Optimal results were observed when exposing the cells to high shear stress for short durations in conical channels, which yielded uptake to over one-third of cells while maintaining viability at approximately 80%. This method was capable of loading cells with molecules including calcein (0.62 kDa), large molecule weight dextrans (150-2,000 kDa), and bovine serum albumin (66 kDa). These results supported the hypothesis that shear-induced intracellular uptake could be generated by flow of cell suspensions through microchannels and further led to the design of a simple, inexpensive, and effective device to deliver molecules into cells. Such a device could benefit biological research and the biotechnology industry.
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Affiliation(s)
- Daniel M. Hallow
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Richard A. Seeger
- The Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Pavel P. Kamaev
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Gustavo R. Prado
- The Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Michelle C. LaPlaca
- The Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Mark R. Prausnitz
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
- The Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University, Georgia Institute of Technology, Atlanta, GA 30332, USA
- Address for correspondence Mark Prausnitz School of Chemical & Biomolecular Engineering Georgia Institute of Technology 311 Ferst Drive Atlanta, GA 30332-0100, USA Phone: (404) 385-5135 Fax: (404) 894-2291
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18
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Boucher PA, Joós B, Zuckermann MJ, Fournier L. Pore formation in a lipid bilayer under a tension ramp: modeling the distribution of rupture tensions. Biophys J 2007; 92:4344-55. [PMID: 17400693 PMCID: PMC1877783 DOI: 10.1529/biophysj.106.092023] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The rupture of fluid membrane vesicles with a steady ramp of micropipette suction has been shown to produce a distribution of breakage tensions, with a mean that rises rapidly with tension rate. Starting from a lattice model that incorporates the essential features of the lipid bilayers held together with hydrophobic forces, and developing it to handle varying tension rates, we reproduce the main features of the experimental results. In essence, we show that the rupture kinetics are driven by the nucleation and growth of pores, with two limiting kinetics-growth-limited and nucleation-limited. The model has been extended to address the role of peptides in solution that can adsorb and insert themselves into the bilayer. At concentrations below those required to spontaneously rupture the membrane, the effect of the peptides is to lower the rupture tensions systematically for all tension rates.
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19
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Photos PJ, Bermudez H, Aranda-Espinoza H, Shillcock J, Discher DE. Nuclear pores and membrane holes: generic models for confined chains and entropic barriers in pore stabilization. SOFT MATTER 2007; 3:364-371. [PMID: 32900153 DOI: 10.1039/b611412c] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The lumen of the nuclear pore complex is increasingly understood to be lined by a polymer brush that entropically regulates transport in and out of the nucleus-and it seems likely that similar effects probably arise with glycocalyx-lined holes in cell membranes. Here we mimic such pore-confined brushes with self-assembled polymer membranes imbued with nano-holes. Experiment and theory help elucidate the entropic origin and stabilization of the pores, which appear to have a similar basis as steric stabilization of colloids bearing polymer brushes. Free energies of interacting brushes reveal stable minima at pore sizes smaller than the classical metastable point, with little effect of the particular pore geometry. Such entropic forces have potential implications for lock and key mechanisms of nuclear pore assembly as well as transient poration of cells and synthetic nano-pores with regulatory mechanisms for transport.
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Affiliation(s)
- Peter J Photos
- Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
| | - Harry Bermudez
- Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
| | - Helim Aranda-Espinoza
- Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
| | - Julian Shillcock
- Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
| | - Dennis E Discher
- Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
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20
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Loison C, Mareschal M, Schmid F. Pores in bilayer membranes of amphiphilic molecules: coarse-grained molecular dynamics simulations compared with simple mesoscopic models. J Chem Phys 2006; 121:1890-900. [PMID: 15260741 DOI: 10.1063/1.1752884] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We investigate pores in fluid membranes by molecular dynamics simulations of an amphiphile-solvent mixture, using a molecular coarse-grained model. The amphiphilic membranes self-assemble into a lamellar stack of amphiphilic bilayers separated by solvent layers. We focus on the particular case of tensionless membranes, in which pores spontaneously appear because of thermal fluctuations. Their spatial distribution is similar to that of a random set of repulsive hard disks. The size and shape distribution of individual pores can be described satisfactorily by a simple mesoscopic model, which accounts only for a pore independent core energy and a line tension penalty at the pore edges. In particular, the pores are not circular: their shapes are fractal and have the same characteristics as those of two-dimensional ring polymers. Finally, we study the size-fluctuation dynamics of the pores, and compare the time evolution of their contour length to a random walk in a linear potential.
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Affiliation(s)
- C Loison
- Max Planck Institut für Chemische Physik fester Stoffe, Nöthnitzer str. 40, D-01187 Dresden, Germany.
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21
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Tolpekina TV, den Otter WK, Briels WJ. Simulations of stable pores in membranes: system size dependence and line tension. J Chem Phys 2006; 121:8014-20. [PMID: 15485265 DOI: 10.1063/1.1796254] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Amphiphilic bilayers with a pore were simulated using a coarse grained model. By stretching the bilayer to 70% beyond its equilibrium surface area, we established the phase diagram of pores, identifying regions where pores are stable, metastable, or unstable. A simple theoretical model is proposed to explain the phase diagram, and to calculate the critical and equilibrium relative stretches. Interestingly, these are found to scale with the inverse cubic root of the number of amphiphiles in the bilayer, thus explaining the order of magnitude difference between the simulated and the measured values. Three different methods are used to calculate a line tension coefficient of (3.5-4.0) x 10(-11) J/m, in good agreement with experimental data.
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Affiliation(s)
- T V Tolpekina
- Computational Dispersion Rheology, Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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22
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Abstract
We report a computer-simulation study of the free-energy barrier for the nucleation of pores in the bilayer membrane under constant stretching lateral pressure. We find that incipient pores are hydrophobic but as the lateral size of the pore nucleus becomes comparable with the molecular length, the pore becomes hydrophilic. In agreement with previous investigations, we find that the dynamical process of growth and closure of hydrophilic pores is controlled by the competition between the surface tension of the membrane and the line tension associated with the rim of the pore. We estimate the line tension of a hydrophilic pore from the shape of the computed free-energy barriers. The line tension thus computed is in a good agreement with available experimental data. We also estimate the line tension of hydrophobic pores at both macroscopic and microscopic levels. The comparison of line tensions at these two different levels indicates that the "microscopic" line tension should be carefully distinguished from the "macroscopic" effective line tension used in the theoretical analysis of pore nucleation. The overall shape of the free-energy barrier for pore nucleation shows no indication for the existence of a metastable intermediate during pore nucleation.
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Affiliation(s)
- Zun-Jing Wang
- Fundamenteel Onderzoek der Materie (FOM), Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ Amsterdam, The Netherlands.
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23
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Abstract
We study the nucleation of a single pore in a fluctuating lipid membrane, specifically taking into account the membrane fluctuations, as well as the shape fluctuations of the pore. For large enough pores, the nucleation free energy is well-described by shifts in the effective membrane surface tension and the pore line tension. Using our framework, we derive the stability criteria for the various pore formation regimes. In addition to the well-known large-tension regime from the classical nucleation theory of pores, we also find a low-tension regime in which the effective line and surface tensions can change sign from their bare values. The latter scenario takes place at sufficiently high temperatures, where the opening of a stable pore of finite size is entropically favorable.
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Affiliation(s)
- Oded Farago
- Materials Research Laboratory, University of California, Santa Barbara, CA 93106, USA
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24
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Knoll A, Lyakhova KS, Horvat A, Krausch G, Sevink GJA, Zvelindovsky AV, Magerle R. Direct imaging and mesoscale modelling of phase transitions in a nanostructured fluid. NATURE MATERIALS 2004; 3:886-891. [PMID: 15568030 DOI: 10.1038/nmat1258] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2004] [Accepted: 09/15/2004] [Indexed: 05/24/2023]
Abstract
The kinetics of phase transitions is essential for understanding pattern formation in structured fluids. These fluids play a key role in the morphogenesis of biological cells, and they are very common in pharmaceutical products and plastic materials. Until now, it has not been possible to follow phase transitions in structured fluids experimentally in real time and with high spatial resolution. Previous work has relied on static images and indirect experimental evidence from spatially averaging scattering experiments. Simulating the processes with computer models is a further challenge because of the multiple time and length scales involved. Our movies based on in situ scanning force microscopy show the time sequence of the elementary steps of a phase transition in a fluid film of block copolymer from the cylinder to the perforated lamella phase. The movies validate a versatile simulation model that gives physical insight into the nature of the process. Our approach provides a means of improving the study and understanding of pattern formation processes in nanostructured fluids. We expect a significant impact on nanotechnology where block copolymers serve as self-organized templates for the synthesis of inorganic nanostructured materials.
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Affiliation(s)
- A Knoll
- Physikalische Chemie II, Universität Bayreuth, D-95440 Bayreuth, Germany
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25
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Loison C, Mareschal M, Kremer K, Schmid F. Thermal fluctuations in a lamellar phase of a binary amphiphile–solvent mixture: A molecular-dynamics study. J Chem Phys 2003. [DOI: 10.1063/1.1626634] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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26
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Farago O, Pincus P. The effect of thermal fluctuations on Schulman area elasticity. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2003; 11:399-408. [PMID: 15011041 DOI: 10.1140/epje/i2003-10049-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We study the elastic properties of a two-dimensional fluctuating surface whose area density is allowed to deviate from its optimal (Schulman) value. The behavior of such a surface is determined by an interplay between the area-dependent elastic energy, the curvature elasticity, and the entropy. We identify three different elastic regimes depending on the ratio Ap/As between the projected (frame) and the saturated areas. We show that thermal fluctuations modify the elastic energy of stretched surfaces (Ap/As>1), and dominate the elastic energy of compressed surfaces (Ap/As<1). When Ap approximately As the elastic energy is not much affected by the fluctuations; the frame area at which the surface tension vanishes becomes smaller than As and the area elasticity modulus increases.
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Affiliation(s)
- O Farago
- Materials Research Laboratory, University of California, Santa Barbara, CA 93106, USA.
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27
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28
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Sundaram J, Mellein BR, Mitragotri S. An experimental and theoretical analysis of ultrasound-induced permeabilization of cell membranes. Biophys J 2003; 84:3087-101. [PMID: 12719239 PMCID: PMC1302870 DOI: 10.1016/s0006-3495(03)70034-4] [Citation(s) in RCA: 169] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Application of ultrasound transiently permeabilizes cell membranes and offers a nonchemical, nonviral, and noninvasive method for cellular drug delivery. Although the ability of ultrasound to increase transmembrane transport has been well demonstrated, a systematic dependence of transport on ultrasound parameters is not known. This study examined cell viability and cellular uptake of calcein using 3T3 mouse cell suspension as a model system. Cells were exposed to varying acoustic energy doses at four different frequencies in the low frequency regime (20-100 kHz). At all frequencies, cell viability decreased with increasing acoustic energy dose, while the fraction of cells exhibiting uptake of calcein showed a maximum at an intermediate energy dose. Acoustic spectra under various ultrasound conditions were also collected and assessed for the magnitude of broadband noise and subharmonic peaks. While the cell viability and transport data did not show any correlation with subharmonic (f/2) emission, they correlated with the broadband noise, suggesting a dominant contribution of transient cavitation. A theoretical model was developed to relate reversible and irreversible membrane permeabilization to the number of transient cavitation events. The model showed that nearly every stage of transient cavitation, including bubble expansion, collapse, and subsequent shock waves may contribute to membrane permeabilization. For each mechanism, the volume around the bubble within which bubbles induce reversible and irreversible membrane permeabilization was determined. Predictions of the model are consistent with experimental data.
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Affiliation(s)
- Jagannathan Sundaram
- Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, USA
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29
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Fournier L, Joós B. Lattice model for the kinetics of rupture of fluid bilayer membranes. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2003; 67:051908. [PMID: 12786179 DOI: 10.1103/physreve.67.051908] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2002] [Revised: 02/18/2003] [Indexed: 05/24/2023]
Abstract
We have constructed a model for the kinetics of rupture of membranes under tension, applying physical principles relevant to lipid bilayers held together by hydrophobic interactions. The membrane is characterized by the bulk compressibility (for expansion) K, the thickness 2h(t) of the hydrophobic part of the bilayer, the hydrophobicity sigma, and a parameter gamma characterizing the tail rigidity of the lipids. The model is a lattice model which incorporates strain relaxation, and considers the nucleation of pores at constant area, constant temperature, and constant particle number. The particle number is conserved by allowing multiple occupancy of the sites. An equilibrium "phase diagram" is constructed as a function of temperature and strain with the total pore surface and distribution as the order parameters. A first-order rupture line is found with increasing tension, and a continuous increase in protopore concentration with rising temperature till instability. The model explains current results on saturated and unsaturated phosphatidylcholine lipid bilayers and thicker artificial bilayers made of diblock copolymers. Pore size distributions are presented for various values of area expansion and temperature, and the fractal dimension of the pore edge is evaluated.
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Affiliation(s)
- Luc Fournier
- Ottawa Carleton Institute of Physics, University of Ottawa Campus, Ottawa, Ontario, Canada K1N-6N5
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30
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31
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Noguchi H. Fusion and toroidal formation of vesicles by mechanical forces: A Brownian dynamics simulation. J Chem Phys 2002. [DOI: 10.1063/1.1510114] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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32
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Abstract
We studied the interaction of bilayer vesicles and adhesive nanoparticles using a Brownian dynamics simulation. The nanoparticles are simple models of proteins or colloids. The adhering nanoparticle induces the morphological change of the vesicle: budding, formation of two vesicles in which only outer monolayers are connected, and fission. We also show that the nanoparticle promotes the fusion process: fusion-pore opening from a stalk intermediate, a neck-like structure that only connects outer monolayers of two vesicles. The nanoparticle bends the stalk, and induces the pore opening.
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Affiliation(s)
- Hiroshi Noguchi
- Department of Applied Molecular Science, Institute for Molecular Science, Okazaki 444-8585, Japan.
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33
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Li XJ, Schick M. Fluctuations in mixtures of lamellar- and nonlamellar-forming lipids. J Chem Phys 2000. [DOI: 10.1063/1.481694] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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34
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Swelling limits for bilayer microstructures: the implosion of lamellar structure versus disordered lamellae. Curr Opin Colloid Interface Sci 2000. [DOI: 10.1016/s1359-0294(00)00032-7] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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35
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Discher BM, Won YY, Ege DS, Lee JC, Bates FS, Discher DE, Hammer DA. Polymersomes: tough vesicles made from diblock copolymers. Science 1999; 284:1143-6. [PMID: 10325219 DOI: 10.1126/science.284.5417.1143] [Citation(s) in RCA: 1791] [Impact Index Per Article: 71.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Vesicles were made from amphiphilic diblock copolymers and characterized by micromanipulation. The average molecular weight of the specific polymer studied, polyethyleneoxide-polyethylethylene (EO40-EE37), is several times greater than that of typical phospholipids in natural membranes. Both the membrane bending and area expansion moduli of electroformed polymersomes (polymer-based liposomes) fell within the range of lipid membrane measurements, but the giant polymersomes proved to be almost an order of magnitude tougher and sustained far greater areal strain before rupture. The polymersome membrane was also at least 10 times less permeable to water than common phospholipid bilayers. The results suggest a new class of synthetic thin-shelled capsules based on block copolymer chemistry.
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Affiliation(s)
- B M Discher
- School of Engineering and Applied Science, and Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA
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36
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Hotyst R. Fluctuating Euler characteristics in lamellar and microemulsion phases. Curr Opin Colloid Interface Sci 1998. [DOI: 10.1016/s1359-0294(98)80060-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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37
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Abstract
The growth of thermally induced pores in a two-dimensional model fluid membrane is investigated by Monte Carlo simulation. Holes appear in the membrane via an activated process, and their subsequent growth is controlled by an edge energy per unit length or line tension. The barrier height and line tension, together with a lateral tension, are the independent parameters of the model. In the resulting phase diagram, a rupture transition separates an intact membrane from a disintegrated state. The approach to the ruptured state shows distinct regimes. Reducing the barrier height at large line tension produces multiple, quasi-independent, small holes whose behavior is dominated by their edge energy, whereas at lower line tensions shape fluctuations of the holes facilitate their coalescence into a single large hole. At a small value of line tension and large barrier height, a single hole spontaneously permeabilizes the membrane in an entropically driven phase transition. Entropy dominates pore growth for line tensions not far below those measured for artificial vesicles. Permeabilization of lipid bilayers by certain peptides involves perturbing lipid-lipid cohesive energies, and our simulations show that at small line tensions the entropy of hole shape fluctuations destroys the model membrane's stability.
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Affiliation(s)
- J C Shillcock
- Max-Planck-Institut für Kolloid- und Grenzflächenforschung, Teltow-Seehof, Germany
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38
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Müller M, Schick M. Structure and nucleation of pores in polymeric bilayers: A Monte Carlo simulation. J Chem Phys 1996. [DOI: 10.1063/1.472682] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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