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Reboucas RB, Faizi HA, Miksis MJ, Vlahovska PM. Stationary shapes of axisymmetric vesicles beyond lowest-energy configurations. SOFT MATTER 2024; 20:2258-2271. [PMID: 38353299 PMCID: PMC11325145 DOI: 10.1039/d3sm01463k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
We conduct a systematic exploration of the energy landscape of vesicle morphologies within the framework of the Helfrich model. Vesicle shapes are determined by minimizing the elastic energy subject to constraints of constant area and volume. The results show that pressurized vesicles can adopt higher-energy spindle-like configurations that require the action of point forces at the poles. If the internal pressure is lower than the external one, multilobed shapes are predicted. We utilize our results to rationalize experimentally observed spindle shapes of giant vesicles in a uniform AC electric field.
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Affiliation(s)
- Rodrigo B Reboucas
- Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, IL 60208, USA.
| | - Hammad A Faizi
- Department of Mechanical Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Michael J Miksis
- Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, IL 60208, USA.
| | - Petia M Vlahovska
- Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, IL 60208, USA.
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Reboucas RB, Miksis MJ, Vlahovska PM. Stationary shapes of axisymmetric vesicles beyond lowest-energy configurations. ARXIV 2023:arXiv:2311.14193v1. [PMID: 38045475 PMCID: PMC10690299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Subscribe] [Scholar Register] [Indexed: 12/05/2023]
Abstract
We conduct a systematic exploration of the energy landscape of vesicle morphologies within the framework of the Helfrich model. Vesicle shapes are determined by minimizing the elastic energy subject to constraints of constant area and volume. The results show that pressurized vesicles can adopt higher-energy spindle-like configurations that require the action of point forces at the poles. If the internal pressure is lower than the external one, multilobed shapes are predicted. We utilize our results to rationalize the experimentally observed spindle shapes of giant vesicles in a uniform AC field.
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Affiliation(s)
| | - Michael J. Miksis
- Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, IL 60208, USA
| | - Petia M. Vlahovska
- Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, IL 60208, USA
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Wubshet NH, Liu AP. Methods to mechanically perturb and characterize GUV-based minimal cell models. Comput Struct Biotechnol J 2022; 21:550-562. [PMID: 36659916 PMCID: PMC9816913 DOI: 10.1016/j.csbj.2022.12.025] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 12/15/2022] [Accepted: 12/15/2022] [Indexed: 12/23/2022] Open
Abstract
Cells shield organelles and the cytosol via an active boundary predominantly made of phospholipids and membrane proteins, yet allowing communication between the intracellular and extracellular environment. Micron-sized liposome compartments commonly known as giant unilamellar vesicles (GUVs) are used to model the cell membrane and encapsulate biological materials and processes in a cell-like confinement. In the field of bottom-up synthetic biology, many have utilized GUVs as substrates to study various biological processes such as protein-lipid interactions, cytoskeletal assembly, and dynamics of protein synthesis. Like cells, it is ideal that GUVs are also mechanically durable and able to stay intact when the inner and outer environment changes. As a result, studies have demonstrated approaches to tune the mechanical properties of GUVs by modulating membrane composition and lumenal material property. In this context, there have been many different methods developed to test the mechanical properties of GUVs. In this review, we will survey various perturbation techniques employed to mechanically characterize GUVs.
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Affiliation(s)
- Nadab H. Wubshet
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
| | - Allen P. Liu
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
- Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, MI 48109, USA
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48109, USA
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Aleksanyan M, Faizi HA, Kirmpaki MA, Vlahovska PM, Riske KA, Dimova R. Assessing membrane material properties from the response of giant unilamellar vesicles to electric fields. ADVANCES IN PHYSICS: X 2022; 8:2125342. [PMID: 36211231 PMCID: PMC9536468 DOI: 10.1080/23746149.2022.2125342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 09/12/2022] [Indexed: 06/16/2023] Open
Abstract
Knowledge of the material properties of membranes is crucial to understanding cell viability and physiology. A number of methods have been developed to probe membranes in vitro, utilizing the response of minimal biomimetic membrane models to an external perturbation. In this review, we focus on techniques employing giant unilamellar vesicles (GUVs), model membrane systems, often referred to as minimal artificial cells because of the potential they offer to mimick certain cellular features. When exposed to electric fields, GUV deformation, dynamic response and poration can be used to deduce properties such as bending rigidity, pore edge tension, membrane capacitance, surface shear viscosity, excess area and membrane stability. We present a succinct overview of these techniques, which require only simple instrumentation, available in many labs, as well as reasonably facile experimental implementation and analysis.
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Affiliation(s)
- Mina Aleksanyan
- Department of Colloid Chemistry, Max Planck Institute of Colloids and Interfaces, 14476 Potsdam, Germany
- Institute for Chemistry and Biochemistry, Free University of Berlin, 14195 Berlin, Germany
| | - Hammad A. Faizi
- Department of Mechanical Engineering, Northwestern University, Evanston, IL, USA
| | - Maria-Anna Kirmpaki
- Department of Colloid Chemistry, Max Planck Institute of Colloids and Interfaces, 14476 Potsdam, Germany
| | - Petia M. Vlahovska
- Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, IL, USA
| | - Karin A. Riske
- Departamento de Biofísica, Universidade Federal de São Paulo, São Paulo, 04039-032 Brazil
| | - Rumiana Dimova
- Department of Colloid Chemistry, Max Planck Institute of Colloids and Interfaces, 14476 Potsdam, Germany
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Faizi HA, Tsui A, Dimova R, Vlahovska PM. Bending Rigidity, Capacitance, and Shear Viscosity of Giant Vesicle Membranes Prepared by Spontaneous Swelling, Electroformation, Gel-Assisted, and Phase Transfer Methods: A Comparative Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:10548-10557. [PMID: 35993569 PMCID: PMC9671160 DOI: 10.1021/acs.langmuir.2c01402] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Closed lipid bilayers in the form of giant unilamellar vesicles (GUVs) are commonly used membrane models. Various methods have been developed to prepare GUVs, however it is unknown if all approaches yield membranes with the same elastic, electric, and rheological properties. Here, we combine flickering spectroscopy and electrodefomation of GUVs to measure, at identical conditions, membrane capacitance, bending rigidity and shear surface viscosity of palmitoyloleoylphosphatidylcholine (POPC) membranes formed by several commonly used preparation methods: thin film hydration (spontaneous swelling), electroformation, gel-assisted swelling using poly(vinyl alcohol) (PVA) or agarose, and phase-transfer. We find relatively similar bending rigidity value across all the methods except for the agarose hydration method. In addition, the capacitance values are similar except for vesicles prepared via PVA gel hydration. Intriguingly, membranes prepared by the gel-assisted and phase-transfer methods exhibit much higher shear viscosity compared to electroformation and spontaneous swelling, likely due to remnants of polymers (PVA and agarose) and oils (hexadecane and mineral) in the lipid bilayer structure.
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Affiliation(s)
- Hammad A Faizi
- Department of Mechanical Engineering, McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois 60208, United States
| | - Annie Tsui
- Department of Industrial Engineering, McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois 60208, United States
| | - Rumiana Dimova
- Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14476 Potsdam, Germany
| | - Petia M Vlahovska
- Department of Engineering Sciences and Applied Mathematics, McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois 60208, United States
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Faizi HA, Dimova R, Vlahovska PM. A vesicle microrheometer for high-throughput viscosity measurements of lipid and polymer membranes. Biophys J 2022; 121:910-918. [PMID: 35176271 PMCID: PMC8943812 DOI: 10.1016/j.bpj.2022.02.015] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 01/08/2022] [Accepted: 02/09/2022] [Indexed: 11/02/2022] Open
Abstract
Viscosity is a key property of cell membranes that controls mobility of embedded proteins and membrane remodeling. Measuring it is challenging because existing approaches involve complex experimental designs and/or models, and the applicability of some methods is limited to specific systems and membrane compositions. As a result there is scarcity of systematic data, and the reported values for membrane viscosity vary by orders of magnitude for the same system. Here, we show how viscosity of membranes can be easily obtained from the transient deformation of giant unilamellar vesicles. The approach enables a noninvasive, probe-independent, and high-throughput measurement of the viscosity of membranes made of lipids or polymers with a wide range of compositions and phase state. Using this novel method, we have collected a significant amount of data that provides insights into the relation between membrane viscosity, composition, and structure.
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Affiliation(s)
- Hammad A Faizi
- Department of Mechanical Engineering, Northwestern University, Evanston, Illinois
| | - Rumiana Dimova
- Department of Theory and Bio-Systems, Max Planck Institute of Colloids and Interfaces, Science Park Golm, Potsdam, Germany
| | - Petia M Vlahovska
- Department of Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, Illinois.
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