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Khadka NK, Mortimer MF, Marosvari M, Timsina R, Mainali L. Membrane elasticity modulated by cholesterol in model of porcine eye lens-lipid membrane. Exp Eye Res 2022; 220:109131. [PMID: 35636489 PMCID: PMC10131281 DOI: 10.1016/j.exer.2022.109131] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2021] [Revised: 05/08/2022] [Accepted: 05/22/2022] [Indexed: 11/29/2022]
Abstract
Experimental evidence shows that the eye lens loses its elasticity dramatically with age. It has also been reported that the cholesterol (Chol) content in the eye lens fiber cell plasma membrane increases significantly with age. High Chol content leads to the formation of cholesterol bilayer domains (CBDs) in the lens membrane. The role of high Chol associated with lens elasticity is unclear. The purpose of this research is to investigate the membrane elasticity of the model of porcine lens-lipid (MPLL) membrane with increasing Chol content to elucidate the role of high Chol in lens membrane elasticity. In this study, we used atomic force microscopy (AFM) to study the mechanical properties (breakthrough force and area compressibility modulus (KA)) of the MPLL membrane with increasing Chol content where KA is the measure of membrane elasticity. We varied Chol concentration in Chol/MPLL membrane from 0 to ∼71 mol%. Supported Chol/MPLL membranes were prepared by fusion of small unilamellar vesicles (SUVs) on top of a flat mica surface. SUVs of the Chol/MPLL lipid mixture were prepared with the rapid solvent exchange method followed by probe-tip sonication. For the Chol/MPLL mixing ratio of 0, AFM image showed the formation of two distinct phases of the membrane, i.e., liquid-disordered phase (ld) and solid-ordered phase (so) membrane. However, with Chol/MPLL mixing ratio of 0.5 and above, only liquid-ordered phase (lo) membrane was formed. Also, two distinct breakthrough forces corresponding to ld and so were observed for Chol/MPLL mixing ratio of 0, whereas only one breakthrough force was observed for membranes with Chol/MPLL mixing ratio of 0.5 and above. No significant difference in the membrane surface roughness was measured with increasing Chol content for these membranes; however, breakthrough force and KA for lo membrane increased when Chol/MPLL mixing ratio was increased from 0.5 to 1. Interestingly above the Chol/MPLL mixing ratio of 1, both breakthrough force and KA decreased, indicating the formation of CBDs. Furthermore, these results showed that membrane elasticity increases at high Chol content, suggesting that high Chol content in lens membrane might be responsible for maintaining lens membrane elasticity.
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Affiliation(s)
- Nawal K Khadka
- Department of Physics, Boise State University, Boise, ID, USA
| | | | - Mason Marosvari
- Department of Physics, Boise State University, Boise, ID, USA
| | - Raju Timsina
- Department of Physics, Boise State University, Boise, ID, USA
| | - Laxman Mainali
- Department of Physics, Boise State University, Boise, ID, USA; Biomolecular Sciences Graduate Program, Boise State University, Boise, ID, USA.
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Kamble S, Patil S, Kulkarni M, Appala VRM. Interleaflet Decoupling in a Lipid Bilayer at Excess Cholesterol Probed by Spectroscopic Ellipsometry and Simulations. J Membr Biol 2020; 253:647-659. [PMID: 33221946 DOI: 10.1007/s00232-020-00156-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 11/11/2020] [Indexed: 11/26/2022]
Abstract
Artificial lipid membranes are often investigated as a replica of the cell membrane in the form of supported lipid bilayers (SLBs). In SLBs, the phase state of a lipid bilayer strongly depends on the presence of molecules such as cholesterol, ceramide, and physical parameters such as temperature. Cholesterol is a key molecule of biological membranes and it exerts condensing effect on lipid bilayers. In this paper, we demonstrate the influence of excess cholesterol content on a supported lipid bilayer of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) (fluid-phase) using spectroscopic ellipsometry (SE) and coarse-grained (CG) molecular dynamics (MD) simulations. The results show the condensation effect due to cholesterol addition up to 30% and interleaflet decoupling at excess cholesterol beyond 30%. SE results show the separation of individual leaflets of the bilayer and influence of cholesterol on the biophysical properties such as thickness and optical index. CG simulations were performed at different ratios of DOPC:cholesterol mixtures to explore cholesterol-driven bilayer properties and stability. The simulations displayed the accumulation of cholesterol molecules at the interface of the lower and upper leaflets of the bilayer, thus leading to undulations in the bilayer. This work reports the successful application of SE technique to study lipid-cholesterol interactions for the first time.
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Affiliation(s)
- Sagar Kamble
- Department of Applied Physics, Defence Institute of Advanced Technology (DIAT) DU, Girinagar, Pune, India
| | - Snehal Patil
- Department of Applied Physics, Defence Institute of Advanced Technology (DIAT) DU, Girinagar, Pune, India
| | - Mandar Kulkarni
- Division of Biophysical Chemistry, Chemical Center, Lund University, 22100, Lund, Sweden.
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Muzio MD, Millan-Solsona R, Borrell JH, Fumagalli L, Gomila G. Cholesterol Effect on the Specific Capacitance of Submicrometric DOPC Bilayer Patches Measured by in-Liquid Scanning Dielectric Microscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:12963-12972. [PMID: 33084346 DOI: 10.1021/acs.langmuir.0c02251] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The specific capacitance of biological membranes is a key physical parameter in bioelectricity that also provides valuable physicochemical information on composition, phase, or hydration properties. Cholesterol is known to modulate the physicochemical properties of biomembranes, but its effect on the specific capacitance has not been fully established yet. Here we use the high spatial resolution capabilities of in-liquid scanning dielectric microscopy in force detection mode to directly demonstrate that DOPC bilayer patches at 50% cholesterol concentration show a strong reduction of their specific capacitance with respect to pure DOPC bilayer patches. The reduction observed (∼35%) cannot be explained by the small increase in bilayer thickness (∼16%). We suggest that the reduction of the specific capacitance might be due to the dehydration of the polar head groups caused by the insertion of cholesterol molecules in the bilayer. The results reported confirm the potential of in-liquid SDM to study the electrical and physicochemical properties of lipid bilayers at very small scales (down to ∼200 nm here), with implications in fields such as biophysics, bioelectricity, biochemistry, and biosensing.
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Affiliation(s)
- Martina Di Muzio
- Nanoscale Bioelectrical Characterization, Institut de Bioenginyeria de Catalunya, The Barcelona Institute of Science and Technology, 08028 Barcelona, Spain
| | - Ruben Millan-Solsona
- Nanoscale Bioelectrical Characterization, Institut de Bioenginyeria de Catalunya, The Barcelona Institute of Science and Technology, 08028 Barcelona, Spain
| | | | | | - Gabriel Gomila
- Nanoscale Bioelectrical Characterization, Institut de Bioenginyeria de Catalunya, The Barcelona Institute of Science and Technology, 08028 Barcelona, Spain
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4
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Solvent-assisted preparation of supported lipid bilayers. Nat Protoc 2019; 14:2091-2118. [DOI: 10.1038/s41596-019-0174-2] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 04/02/2019] [Indexed: 11/08/2022]
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Williams AT, Donno R, Tirelli N, Dryfe RAW. Biofunctional few-layer metal dichalcogenides and related heterostructures produced by direct aqueous exfoliation using phospholipids. RSC Adv 2019; 9:37061-37066. [PMID: 35539078 PMCID: PMC9075593 DOI: 10.1039/c9ra07764b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Accepted: 11/06/2019] [Indexed: 11/21/2022] Open
Abstract
We report a novel, inexpensive and green method for preparing aqueous dispersions of various biofunctional transition-metal dichalcogenides (MoS2, WS2, TiS2 and MoSe2) and their related heterostructures directly via ultrasonic exfoliation mediated by the presence of phospholipids. The dispersions predominantly consist of few-layer flakes coated with 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), as confirmed by Raman, photoluminescence and X-ray photoelectron spectroscopies. The phospholipid coating renders the flakes biofunctional, which coupled with the unique properties of transition-metal dichalcogenides and their heterostructures, suggests this method will have great potential in biological applications. We report a method for preparing aqueous dispersions of biofunctional transition-metal dichalcogenides (MoS2, WS2, TiS2 and MoSe2) and their related heterostructures directly via ultrasonic exfoliation mediated by the presence of phospholipids.![]()
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Affiliation(s)
| | - Roberto Donno
- Laboratory of Polymers and Biomaterials
- Fondazione Istituto Italiano di Tecnologia
- Genoa
- Italy
| | - Nicola Tirelli
- Laboratory of Polymers and Biomaterials
- Fondazione Istituto Italiano di Tecnologia
- Genoa
- Italy
| | - Robert A. W. Dryfe
- School of Chemistry
- University of Manchester
- Manchester
- UK
- National Graphene Institute
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Dols-Perez A, Fumagalli L, Gomila G. Interdigitation in spin-coated lipid layers in air. Colloids Surf B Biointerfaces 2018; 172:400-406. [PMID: 30195157 DOI: 10.1016/j.colsurfb.2018.08.041] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 08/14/2018] [Accepted: 08/19/2018] [Indexed: 10/28/2022]
Abstract
In this study, we show that dry saturated phospholipid layers prepared by the spin-coating technique could present thinner regions associated to interdigitated phases under some conditions. The morphological characteristics of lipid layers of saturated phosphocholines, such as dilauroylphosphatidylcholine (DLPC), dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine (DPPC) and distearoylphosphatidylcholine (DSPC), have been measured by Atomic Force Microscopy and revealed that the presence of interdigitated regions is not induced by the same parameters that induce them in hydrated samples. To achieve these results the effect of the lipid hidrocabonated chain length, the presence of alcohol in the coating solution, the spinning velocity and the presence of cholesterol were tested. We showed that DPPC and DSPC bilayers, on the one side, can show structures with similar height than interdigitated regions observed in hydrated samples, while, on the other side, DLPC and DMPC tend to show no evidence of interdigitation. Results indicate that the presence of interdigitated areas is due to the presence of lateral tensions and, hence, that they can be eliminated by releasing these tensions by, for instance, the addition of cholesterol. These results demonstrate that interdigitation in lipid layers is a rather general phenomena and can be observed in lipid bilayers in dry conditions.
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Affiliation(s)
- Aurora Dols-Perez
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ, Delft, Netherlands.
| | - Laura Fumagalli
- School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Gabriel Gomila
- Institut de Bioenginyeria de Catalunya (IBEC), C/ Baldiri i Reixac 15-21, 08028, Barcelona, Spain; Departament d'Enginyeria Electrònica i Biomèdica, Universitat de Barcelona, C/ Martí i Franquès 1, 08028, Barcelona, Spain
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Williams AT, Donno R, Tirelli N, Dryfe RA. Phospholipid-mediated exfoliation as a facile preparation method for graphene suspensions. RSC Adv 2018; 8:19220-19225. [PMID: 35539657 PMCID: PMC9080625 DOI: 10.1039/c8ra03365j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Accepted: 05/16/2018] [Indexed: 11/25/2022] Open
Abstract
This paper deals with simple, inexpensive and ‘green’ methods of production for graphene in colloidal dispersion. Herein, we report on such a method by preparing aqueous graphene dispersions via ultrasonic exfoliation in the presence of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). The product predominantly consists of few-layer graphene flakes coated by DOPC with a lateral size of a few tens to hundreds of nm, as confirmed by Raman and X-ray photoelectron spectroscopies, thermogravimetric analysis (TGA), dynamic light scattering (DLS) and atomic force microscopy (AFM). The novelty of this method lies in its dependence on a typical soft matter property: the fluidity of the hydrophobic chains. Stiffer phospholipids such as 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC, which possesses two palmitoyl chains) or 2-oleoyl-1-palmitoyl-sn-glycero-3-phosphocholine (POPC, one palmitoyl, one oleyl chain) are ineffective at dispersing graphene; however, in the presence of cholesterol these phospholipids also become effective mediators. The phospholipid coating renders the flakes compatible with biological environments. A simple, inexpensive and ‘green’ method of production for graphene in colloidal dispersion.![]()
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Affiliation(s)
| | - Roberto Donno
- Laboratory of Polymers and Biomaterials
- Fondazione Istituto Italiano di Tecnologia
- Genoa
- Italy
| | - Nicola Tirelli
- Laboratory of Polymers and Biomaterials
- Fondazione Istituto Italiano di Tecnologia
- Genoa
- Italy
- NorthWest Centre for Advanced Drug Delivery
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Ruiz-Rincón S, González-Orive A, de la Fuente JM, Cea P. Reversible Monolayer-Bilayer Transition in Supported Phospholipid LB Films under the Presence of Water: Morphological and Nanomechanical Behavior. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:7538-7547. [PMID: 28691823 DOI: 10.1021/acs.langmuir.7b01268] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Mixed monolayer Langmuir-Blodgett (LB) films of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and cholesterol (Chol) in the 1:1 ratio have been prepared onto solid mica substrates. Upon immersion in water or in an aqueous HEPES solution (pH 7.4) the monolayer LB films were spontaneously converted into well-organized bilayers leaving free mica areas. The process has been demonstrated to be reversible upon removal of the aqueous solution, resulting in remarkably free of defects monolayers that are homogeneously distributed onto the mica. In addition, the nanomechanical properties exhibited by the as-formed bilayers have been determined by means of AFM breakthrough force studies. The bilayers formed by immersion of the monolayer in an aqueous media exhibit nanomechanical properties and stability under compression analogous to those of DPPC:Chol supported bilayers obtained by other methods previously described in the literature. Consequently, the hydration of a monolayer LB film has been revealed as an easy method to produce well-ordered bilayers that mimic the cell membrane and that could be used as model cell membranes.
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Affiliation(s)
| | | | - Jesús M de la Fuente
- Instituto de Ciencia de Materiales de Aragón (ICMA), Universidad de Zaragoza-CSIC , 50009 Zaragoza, Spain
- Networking Biomedical Research Center of Bioengineering, Biomaterials, and Nanomedicine (CIBER-BBN), Zaragoza, Spain
| | - Pilar Cea
- Departamento de Química Física, Facultad de Ciencias, Universidad de Zaragoza , 50009, Zaragoza, Spain
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Murthy AVR, Guyomarc'h F, Lopez C. Cholesterol Decreases the Size and the Mechanical Resistance to Rupture of Sphingomyelin Rich Domains, in Lipid Bilayers Studied as a Model of the Milk Fat Globule Membrane. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:6757-6765. [PMID: 27300157 DOI: 10.1021/acs.langmuir.6b01040] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Sphingomyelin-rich microdomains have been observed in the biological membrane surrounding milk fat globules (MFGM). The role played by cholesterol in these domains and in the physical properties and functions of the MFGM remains poorly understood. The objective of this work was therefore to investigate the phase state, topography, and mechanical properties of MFGM polar lipid bilayers as a function of cholesterol concentration, by combining X-ray diffraction, atomic force microscopy imaging, and force spectroscopy. At room temperature, i.e. below the phase transition temperature of the MFGM polar lipids, the bilayers showed the formation of sphingomyelin-rich domains in the solid ordered (so) phase that protruded about 1 nm above the liquid disordered (ld) phase. These so phase domains have a higher mechanical resistance to rupture than the ld phase (30 nN versus 15 nN). Addition of cholesterol in the MFGM polar lipid bilayers (i) induced the formation of liquid ordered (lo) phase for up to 27 mol % in the bilayers, (ii) decreased the height difference between the thicker ordered domains and the surrounding ld phase, (iii) promoted the formation of small sized domains, and (iv) decreased the mechanical resistance to rupture of the sphingomyelin-rich domains down to ∼5 nN. The biological and functional relevance of the lo phase cholesterol/sphingomyelin-rich domains in the membrane surrounding fat globules in milk remains to be elucidated. This study brought new insight about the functional role of cholesterol in milk polar lipid ingredients, which can be used in the preparation of food emulsions, e.g. infant milk formulas.
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Gomes MJ, Dreier J, Brewer J, Martins S, Brandl M, Sarmento B. A new approach for a blood-brain barrier model based on phospholipid vesicles: Membrane development and siRNA-loaded nanoparticles permeability. J Memb Sci 2016. [DOI: 10.1016/j.memsci.2016.01.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Calò A, Robles OV, Santos S, Verdaguer A. Capillary and van der Waals interactions on CaF2 crystals from amplitude modulation AFM force reconstruction profiles under ambient conditions. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2015; 6:809-819. [PMID: 25977852 PMCID: PMC4419597 DOI: 10.3762/bjnano.6.84] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 02/26/2015] [Indexed: 06/04/2023]
Abstract
There has been much interest in the past two decades to produce experimental force profiles characteristic of the interaction between nanoscale objects or a nanoscale object and a plane. Arguably, the advent of the atomic force microscope AFM was instrumental in driving such efforts because, in principle, force profiles could be recovered directly. Nevertheless, it has taken years before techniques have developed enough as to recover the attractive part of the force with relatively low noise and without missing information on critical ranges, particularly under ambient conditions where capillary interactions are believed to dominate. Thus a systematic study of the different profiles that may arise in such situations is still lacking. Here we employ the surfaces of CaF2, on which nanoscale water films form, to report on the range and force profiles that might originate by dynamic capillary interactions occurring between an AFM tip and nanoscale water patches. Three types of force profiles were observed under ambient conditions. One in which the force decay resembles the well-known inverse-square law typical of van der Waals interactions during the first 0.5-1 nm of decay, a second one in which the force decays almost linearly, in relatively good agreement with capillary force predicted by the constant chemical potential approximation, and a third one in which the attractive force is almost constant, i.e., forms a plateau, up to 3-4 nm above the surface when the formation of a capillary neck dominates the tip-sample interaction.
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Affiliation(s)
- Annalisa Calò
- Institut Català de Nanociència i Nanotecnologia (ICN2), Campus UAB, Bellaterra, Barcelona, 08193, Spain
| | - Oriol Vidal Robles
- Institut Català de Nanociència i Nanotecnologia (ICN2), Campus UAB, Bellaterra, Barcelona, 08193, Spain
| | - Sergio Santos
- Departament de Disseny i Programació de Sistemes Electrònics, Universitat Politècnica de Catalunya (UPC), Av. Bases 61, Manresa, Barcelona, 08242, Spain
| | - Albert Verdaguer
- Institut Català de Nanociència i Nanotecnologia (ICN2), Campus UAB, Bellaterra, Barcelona, 08193, Spain
- Consejo Superior de Investigaciones Científicas (CSIC), ICN2 Building, Bellaterra, Barcelona, 08193, Spain
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