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Weakly HMJ, Wilson KJ, Goetz GJ, Pruitt EL, Li A, Xu L, Keller SL. Several common methods of making vesicles (except an emulsion method) capture intended lipid ratios. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.21.581444. [PMID: 38948736 PMCID: PMC11212916 DOI: 10.1101/2024.02.21.581444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Abstract
Researchers choose different methods of making giant unilamellar vesicles in order to satisfy different constraints of their experimental designs. A challenge of using a variety of methods is that each may produce vesicles of different lipid compositions, even if all vesicles are made from a common stock mixture. Here, we use mass spectrometry to investigate ratios of lipids in vesicles made by five common methods: electroformation on indium tin oxide slides, electroformation on platinum wires, gentle hydration, emulsion transfer, and extrusion. We made vesicles from either 5-component or binary mixtures of lipids chosen to span a wide range of physical properties: di(18:1)PC, di(16:0)PC, di(18:1)PG, di(12:0)PE, and cholesterol. For a mixture of all five of these lipids, ITO electroformation, Pt electroformation, gentle hydration, and extrusion methods result in only minor shifts (≤ 5 mol%) in lipid ratios of vesicles relative to a common stock solution. In contrast, emulsion transfer results in ∼80% less cholesterol than expected from the stock solution, which is counterbalanced by a surprising overabundance of saturated PC-lipid relative to all other phospholipids. Experiments using binary mixtures of some of the lipids largely support results from the 5-component mixture. Exact values of lipid ratios variations likely depend on the details of each method, so a broader conclusion is that experiments that increment lipid ratios in small steps will be highly sensitive to the method of lipid formation and to sample-to-sample variations, which are low (roughly ±2 mol% in the 5-component mixture and either scale proportionally with increasing mole fraction or remain low). Experiments that increment lipid ratios in larger steps or that seek to explain general trends or new phenomena will be less sensitive to the method used. SIGNIFICANCE STATEMENT Small changes to the amounts and types of lipids in membranes can drastically affect the membrane's behavior. Unfortunately, it is unknown whether (or to what extent) different methods of making vesicles alter the ratios of lipids in membranes, even when identical stock solutions are used. This presents challenges for researchers when comparing data with colleagues who use different methods. Here, we measure ratios of lipid types in vesicle membranes produced by five methods. We assess each method's reproducibility and compare resulting vesicle compositions across methods. In doing so, we provide a quantitative basis that the scientific community can use to estimate whether differences between their results can be simply attributed to differences between methods or to sample-to-sample variations.
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Pazzi J, Subramaniam AB. Dynamics of giant vesicle assembly from thin lipid films. J Colloid Interface Sci 2024; 661:1033-1045. [PMID: 38335788 DOI: 10.1016/j.jcis.2024.02.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2023] [Revised: 01/28/2024] [Accepted: 02/02/2024] [Indexed: 02/12/2024]
Abstract
MOTIVATION Giant unilamellar vesicles (GUVs), cell-like synthetic micrometer size structures, assemble when thin lipid films are hydrated in aqueous solutions. Quantitative measurements of static yields and distribution of sizes of GUVs obtained from thin film hydration methods were recently reported. Dynamic data such as the time evolution of yields and distribution of sizes, however, is not known. Dynamic data can provide insights into the assembly pathway of GUVs and guidelines for choosing conditions to obtain populations with desired size distributions. APPROACH We develop the 'stopped-time' technique to characterize the time evolution of the distribution of sizes and molar yields of populations of free-floating GUVs. We additionally capture high resolution time-lapse images of surface-attached GUV buds on the lipid films. We systematically study the dynamics of assembly of GUVs from three widely used thin film hydration methods, PAPYRUS (Paper-Abetted amPhiphile hYdRation in aqUeous Solutions), gentle hydration, and electroformation. FINDINGS We find that the molar yield versus time curves of GUVs demonstrate a characteristic sigmoidal shape, with an initial yield, a transient, and then a steady state plateau for all three methods. The population of GUVs showed a right-skewed distribution of diameters. The variance of the distributions increased with time. The systems reached steady state within 120 min. We rationalize the dynamics using the thermodynamically motivated budding and merging (BNM) model. These results further the understanding of lipid dynamics and provide for the first-time practical parameters to tailor the production of GUVs of specific sizes for applications.
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Affiliation(s)
- Joseph Pazzi
- Department of Bioengineering, University of California, Merced, CA 95343, United States
| | - Anand Bala Subramaniam
- Department of Bioengineering, University of California, Merced, CA 95343, United States.
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Van de Cauter L, van Buren L, Koenderink GH, Ganzinger KA. Exploring Giant Unilamellar Vesicle Production for Artificial Cells - Current Challenges and Future Directions. SMALL METHODS 2023; 7:e2300416. [PMID: 37464561 DOI: 10.1002/smtd.202300416] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 05/30/2023] [Indexed: 07/20/2023]
Abstract
Creating an artificial cell from the bottom up is a long-standing challenge and, while significant progress has been made, the full realization of this goal remains elusive. Arguably, one of the biggest hurdles that researchers are facing now is the assembly of different modules of cell function inside a single container. Giant unilamellar vesicles (GUVs) have emerged as a suitable container with many methods available for their production. Well-studied swelling-based methods offer a wide range of lipid compositions but at the expense of limited encapsulation efficiency. Emulsion-based methods, on the other hand, excel at encapsulation but are only effective with a limited set of membrane compositions and may entrap residual additives in the lipid bilayer. Since the ultimate artificial cell will need to comply with both specific membrane and encapsulation requirements, there is still no one-method-fits-all solution for GUV formation available today. This review discusses the state of the art in different GUV production methods and their compatibility with GUV requirements and operational requirements such as reproducibility and ease of use. It concludes by identifying the most pressing issues and proposes potential avenues for future research to bring us one step closer to turning artificial cells into a reality.
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Affiliation(s)
- Lori Van de Cauter
- Autonomous Matter Department, AMOLF, Amsterdam, 1098 XG, The Netherlands
| | - Lennard van Buren
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, 2629 HZ, The Netherlands
| | - Gijsje H Koenderink
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, 2629 HZ, The Netherlands
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Cooper A, Girish V, Subramaniam AB. Osmotic Pressure Enables High-Yield Assembly of Giant Vesicles in Solutions of Physiological Ionic Strengths. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:5579-5590. [PMID: 37021722 PMCID: PMC10116648 DOI: 10.1021/acs.langmuir.3c00457] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Giant unilamellar vesicles (GUVs) are micrometer-scale minimal cellular mimics that are useful for bottom-up synthetic biology and drug delivery. Unlike assembly in low-salt solutions, assembly of GUVs in solutions with ionic concentrations of 100-150 mM Na/KCl (salty solutions) is challenging. Chemical compounds deposited on the substrate or incorporated into the lipid mixture could assist in the assembly of GUVs. Here, we investigate quantitatively the effects of temperature and chemical identity of six polymeric compounds and one small molecule compound on the molar yields of GUVs composed of three different lipid mixtures using high-resolution confocal microscopy and large data set image analysis. All the polymers moderately increased the yields of GUVs either at 22 or 37 °C, whereas the small molecule compound was ineffective. Low-gelling temperature agarose is the singular compound that consistently produces yields of GUVs of greater than 10%. We propose a free energy model of budding to explain the effects of polymers in assisting the assembly of GUVs. The osmotic pressure exerted on the membranes by the dissolved polymer balances the increased adhesion between the membranes, thus reducing the free energy for bud formation. Data obtained by modulating the ionic strength and ion valency of the solution shows that the evolution of the yield of GUVs supports our model's prediction. In addition, polymer-specific interactions with the substrate and the lipid mixture affects yields. The uncovered mechanistic insights provide a quantitative experimental and theoretical framework to guide future studies. Additionally, this work shows a facile means for obtaining GUVs in solutions of physiological ionic strengths.
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Affiliation(s)
- Alexis Cooper
- Department
of Chemistry and Biochemistry, University
of California, Merced, Merced, California 95343, United States
| | - Vaishnavi Girish
- Department
of Bioengineering, University of California,
Merced, Merced, California 95343, United States
| | - Anand Bala Subramaniam
- Department
of Bioengineering, University of California,
Merced, Merced, California 95343, United States
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Dolder N, Müller P, von Ballmoos C. Experimental platform for the functional investigation of membrane proteins in giant unilamellar vesicles. SOFT MATTER 2022; 18:5877-5893. [PMID: 35916307 PMCID: PMC9364335 DOI: 10.1039/d2sm00551d] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Giant unilamellar vesicles (GUVs) are micrometer-sized model membrane systems that can be viewed directly under the microscope. They serve as scaffolds for the bottom-up creation of synthetic cells, targeted drug delivery and have been widely used to study membrane related phenomena in vitro. GUVs are also of interest for the functional investigation of membrane proteins that carry out many key cellular functions. A major hurdle to a wider application of GUVs in this field is the diversity of existing protocols that are optimized for individual proteins. Here, we compare PVA assisted and electroformation techniques for GUV formation under physiologically relevant conditions, and analyze the effect of immobilization on vesicle structure and membrane tightness towards small substrates and protons. There, differences in terms of yield, size, and leakage of GUVs produced by PVA assisted swelling and electroformation were found, dependent on salt and buffer composition. Using fusion of oppositely charged membranes to reconstitute a model membrane protein, we find that empty vesicles and proteoliposomes show similar fusion behavior, which allows for a rapid estimation of protein incorporation using fluorescent lipids.
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Affiliation(s)
- Nicolas Dolder
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
| | - Philipp Müller
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
| | - Christoph von Ballmoos
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
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Gözen I, Köksal ES, Põldsalu I, Xue L, Spustova K, Pedrueza-Villalmanzo E, Ryskulov R, Meng F, Jesorka A. Protocells: Milestones and Recent Advances. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2106624. [PMID: 35322554 DOI: 10.1002/smll.202106624] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Revised: 02/06/2022] [Indexed: 06/14/2023]
Abstract
The origin of life is still one of humankind's great mysteries. At the transition between nonliving and living matter, protocells, initially featureless aggregates of abiotic matter, gain the structure and functions necessary to fulfill the criteria of life. Research addressing protocells as a central element in this transition is diverse and increasingly interdisciplinary. The authors review current protocell concepts and research directions, address milestones, challenges and existing hypotheses in the context of conditions on the early Earth, and provide a concise overview of current protocell research methods.
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Affiliation(s)
- Irep Gözen
- Centre for Molecular Medicine Norway, Faculty of Medicine, University of Oslo, Oslo, 0318, Norway
| | - Elif Senem Köksal
- Centre for Molecular Medicine Norway, Faculty of Medicine, University of Oslo, Oslo, 0318, Norway
| | - Inga Põldsalu
- Centre for Molecular Medicine Norway, Faculty of Medicine, University of Oslo, Oslo, 0318, Norway
| | - Lin Xue
- Centre for Molecular Medicine Norway, Faculty of Medicine, University of Oslo, Oslo, 0318, Norway
| | - Karolina Spustova
- Centre for Molecular Medicine Norway, Faculty of Medicine, University of Oslo, Oslo, 0318, Norway
| | - Esteban Pedrueza-Villalmanzo
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg, SE-412 96, Sweden
- Department of Physics, University of Gothenburg, Universitetsplatsen 1, Gothenburg, 40530, Sweden
| | - Ruslan Ryskulov
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg, SE-412 96, Sweden
| | - Fanda Meng
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg, SE-412 96, Sweden
- School of Basic Medicine, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, 250000, China
| | - Aldo Jesorka
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg, SE-412 96, Sweden
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Hamada N, Longo ML. Characterization of phase separation phenomena in hybrid lipid/block copolymer/cholesterol bilayers using laurdan fluorescence with log-normal multipeak analysis. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183887. [PMID: 35150645 DOI: 10.1016/j.bbamem.2022.183887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 02/01/2022] [Accepted: 02/03/2022] [Indexed: 06/14/2023]
Abstract
Phase separation phenomena in hybrid lipid/block copolymer/cholesterol bilayers combining polybutadiene-block-polyethylene oxide (PBdPEO), egg sphingomyelin (egg SM), and cholesterol were studied with fluorescence spectroscopy and microscopy for comparison to lipid bilayers composed of palmitoyl oleoyl phosphatidylcholine (POPC), egg SM, and cholesterol. Laurdan emission spectra were decomposed into three lognormal curves. The temperature dependence of the ratios of the areas of the middle and lowest energy peaks revealed temperature break-point (Tbreak) values that were in better agreement, compared to generalized polarization inflection temperatures, with phase transition temperatures in giant unilamellar vesicles (GUVs). Agreement between GUV and spectroscopy results was further improved for hybrid vesicles by using the ratio of the area of the middle peak to the sum of the areas all three peaks to find the Tbreak values. For the hybrid vesicles, trends at Tbreak are hypothesized to be correlated with the mechanisms by which the phase transition takes place, supported by the compositional range as well as the morphologies of domains observed in GUVs. Low miscibility of PBdPEO and egg SM is suggested by the finding of relatively high Tbreak values at cholesterol contents greater than 30 mol%. Further, GUV phase behavior suggests stronger partitioning of cholesterol into PBdPEO than into POPC, and less miscibility of PBdPEO than POPC with egg SM. These results, summarized using a heat-map, contribute to the limited body of knowledge regarding the effect of cholesterol on hybrid membranes, with potential application toward the development of such materials for drug delivery or membrane protein reconstitution.
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Affiliation(s)
- Naomi Hamada
- Department of Chemical Engineering, University of California Davis, Davis, CA 95616, United States
| | - Marjorie L Longo
- Department of Chemical Engineering, University of California Davis, Davis, CA 95616, United States.
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One-pot treatment of cellulose using iron oxide catalysts to produce nanocellulose and water-soluble oxidised cellulose. Carbohydr Polym 2022; 282:119060. [DOI: 10.1016/j.carbpol.2021.119060] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Revised: 12/20/2021] [Accepted: 12/26/2021] [Indexed: 01/22/2023]
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