1
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Orlikowska-Rzeznik H, Versluis J, Bakker HJ, Piatkowski L. Cholesterol Changes Interfacial Water Alignment in Model Cell Membranes. J Am Chem Soc 2024; 146:13151-13162. [PMID: 38687869 PMCID: PMC11099968 DOI: 10.1021/jacs.4c00474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Revised: 04/20/2024] [Accepted: 04/22/2024] [Indexed: 05/02/2024]
Abstract
The nanoscopic layer of water that directly hydrates biological membranes plays a critical role in maintaining the cell structure, regulating biochemical processes, and managing intermolecular interactions at the membrane interface. Therefore, comprehending the membrane structure, including its hydration, is essential for understanding the chemistry of life. While cholesterol is a fundamental lipid molecule in mammalian cells, influencing both the structure and dynamics of cell membranes, its impact on the structure of interfacial water has remained unknown. We used surface-specific vibrational sum-frequency generation spectroscopy to study the effect of cholesterol on the structure and hydration of monolayers of the lipids 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), and egg sphingomyelin (SM). We found that for the unsaturated lipid DOPC, cholesterol intercalates in the membrane without significantly changing the orientation of the lipid tails and the orientation of the water molecules hydrating the headgroups of DOPC. In contrast, for the saturated lipids DPPC and SM, the addition of cholesterol leads to clearly enhanced packing and ordering of the hydrophobic tails. It is also observed that the orientation of the water hydrating the lipid headgroups is enhanced upon the addition of cholesterol. These results are important because the orientation of interfacial water molecules influences the cell membranes' dipole potential and the strength and specificity of interactions between cell membranes and peripheral proteins and other biomolecules. The lipid nature-dependent role of cholesterol in altering the arrangement of interfacial water molecules offers a fresh perspective on domain-selective cellular processes, such as protein binding.
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Affiliation(s)
- Hanna Orlikowska-Rzeznik
- Faculty
of Materials Engineering and Technical Physics, Poznan University of Technology, 60-965 Poznan, Poland
| | - Jan Versluis
- AMOLF,
Ultrafast Spectroscopy, 1098 XG Amsterdam, The Netherlands
| | - Huib J. Bakker
- AMOLF,
Ultrafast Spectroscopy, 1098 XG Amsterdam, The Netherlands
| | - Lukasz Piatkowski
- Faculty
of Materials Engineering and Technical Physics, Poznan University of Technology, 60-965 Poznan, Poland
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2
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Elstone N, Arnold T, Skoda MWA, Lewis SE, Li P, Hazell G, Edler KJ. Structural investigation of sulfobetaines and phospholipid monolayers at the air-water interface. Phys Chem Chem Phys 2022; 24:22679-22690. [PMID: 36106535 DOI: 10.1039/d2cp02695c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Mixtures of sulfobetaine based lipids with phosphocholine phospholipids are of interest in order to study the interactions between zwitterionic surfactants and the phospholipids present in cell membranes. In this study we have investigated the structure of mixed monolayers of sulfobetaines and phosphocholine phospholipids. The sulfobetaine used has a single 18-carbon tail, and is referred to as SB3-18, and the phospholipid used is DMPC. Surface pressure-area isotherms of the samples were used to determine whether any phase transitions were present during the compression of the monolayers. Neutron and X-ray reflectometry were then used to investigate the structure of these monolayers perpendicular to the interface. We found that the average headgroup and tail layer thickness was reasonably consistent across all mixtures, with a variation of less than 3 Å reported in the total thickness of the monolayers at each surface pressure. However, by selective deuteration of the two components of the monolayers, it was found that the two components have different tail layer thicknesses. For the mixture with equal compositions of DMPC and SB3-18 or with a higher composition of DMPC the tail tilts were found to be constant, resulting in a greater tail layer thickness for SB3-18 due to its longer tail. For the mixture higher in SB3-18 this was not the case, the tail tilt angle for the two components was found to be different and DMPC was found to have a greater tail layer thickness than SB3-18 as a result.
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Affiliation(s)
- Naomi Elstone
- Centre for Sustainable & Circular Technologies, University of Bath, Claverton Down, Bath, BA2 7AY, UK. .,Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK
| | - Thomas Arnold
- Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK.,European Spallation Source ERIC, P.O. Box 176, SE-221 00 Lund, Sweden.,Diamond Light Source, Harwell Science and Innovation Campus, Didcot, OX11 0DE, UK.,ISIS Neutron Source Facility, Harwell Science and Innovation Campus, Didcot, OX11 0DE, UK
| | - Maximilian W A Skoda
- ISIS Neutron Source Facility, Harwell Science and Innovation Campus, Didcot, OX11 0DE, UK
| | - Simon E Lewis
- Centre for Sustainable & Circular Technologies, University of Bath, Claverton Down, Bath, BA2 7AY, UK. .,Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK
| | - Peixun Li
- ISIS Neutron Source Facility, Harwell Science and Innovation Campus, Didcot, OX11 0DE, UK
| | - Gavin Hazell
- Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK
| | - Karen J Edler
- Centre for Sustainable & Circular Technologies, University of Bath, Claverton Down, Bath, BA2 7AY, UK. .,Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK
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3
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Sarkar P, Chattopadhyay A. Membrane Dipole Potential: An Emerging Approach to Explore Membrane Organization and Function. J Phys Chem B 2022; 126:4415-4430. [PMID: 35696090 DOI: 10.1021/acs.jpcb.2c02476] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Biological membranes are complex organized molecular assemblies of lipids and proteins that provide cells and membrane-bound intracellular organelles their individual identities by morphological compartmentalization. Membrane dipole potential originates from the electrostatic potential difference within the membrane due to the nonrandom arrangement (orientation) of amphiphile and solvent (water) dipoles at the membrane interface. In this Feature Article, we will focus on the measurement of dipole potential using electrochromic fluorescent probes and highlight interesting applications. In addition, we will focus on ratiometric fluorescence microscopic imaging technique to measure dipole potential in cellular membranes, a technique that can be used to address novel problems in cell biology which are otherwise difficult to address using available approaches. We envision that membrane dipole potential could turn out to be a convenient tool in exploring the complex interplay between membrane lipids and proteins and could provide novel insights in membrane organization and function.
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Affiliation(s)
- Parijat Sarkar
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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4
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Sánchez-López E, Esteruelas G, Ortiz A, Espina M, Prat J, Muñoz M, Cano A, Calpena AC, Ettcheto M, Camins A, Alsafi Z, Souto EB, García ML, Pujol M. Dexibuprofen Biodegradable Nanoparticles: One Step Closer towards a Better Ocular Interaction Study. NANOMATERIALS (BASEL, SWITZERLAND) 2020; 10:E720. [PMID: 32290252 PMCID: PMC7221783 DOI: 10.3390/nano10040720] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 03/30/2020] [Accepted: 04/04/2020] [Indexed: 02/08/2023]
Abstract
Ocular inflammation is one of the most prevalent diseases in ophthalmology, which can affect various parts of the eye or the surrounding tissues. Non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, are commonly used to treat ocular inflammation in the form of eye-drops. However, their bioavailability in ocular tissues is very low (less than 5%). Therefore, drug delivery systems such as biodegradable polymeric PLGA nanoparticles constitute a suitable alternative to topical eye administration, as they can improve ocular bioavailability and simultaneously reduce drug induced side effects. Moreover, their prolonged drug release can enhance patient treatment adherence as they require fewer administrations. Therefore, several formulations of PLGA based nanoparticles encapsulating dexibuprofen (active enantiomer of Ibuprofen) were prepared using the solvent displacement method employing different surfactants. The formulations have been characterized and their interactions with a customized lipid corneal membrane model were studied. Ex vivo permeation through ocular tissues and in vivo anti-inflammatory efficacy have also been studied.
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Affiliation(s)
- Elena Sánchez-López
- Department of Pharmacy, Pharmaceutical Technology and Physical Chemistry, Faculty of Pharmacy, University of Barcelona, 08028 Barcelona, Spain; (G.E.); (A.O.); (M.E.); (J.P.); (M.M.); (A.C.); (A.C.C.); (M.L.G.); (M.P.)
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
- Center for Biomedical Research in Neurodegenerative Diseases Network (CIBERNED), Carlos III Health Institute, 28031 Madrid, Spain; (M.E.); (A.C.)
| | - Gerard Esteruelas
- Department of Pharmacy, Pharmaceutical Technology and Physical Chemistry, Faculty of Pharmacy, University of Barcelona, 08028 Barcelona, Spain; (G.E.); (A.O.); (M.E.); (J.P.); (M.M.); (A.C.); (A.C.C.); (M.L.G.); (M.P.)
| | - Alba Ortiz
- Department of Pharmacy, Pharmaceutical Technology and Physical Chemistry, Faculty of Pharmacy, University of Barcelona, 08028 Barcelona, Spain; (G.E.); (A.O.); (M.E.); (J.P.); (M.M.); (A.C.); (A.C.C.); (M.L.G.); (M.P.)
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Marta Espina
- Department of Pharmacy, Pharmaceutical Technology and Physical Chemistry, Faculty of Pharmacy, University of Barcelona, 08028 Barcelona, Spain; (G.E.); (A.O.); (M.E.); (J.P.); (M.M.); (A.C.); (A.C.C.); (M.L.G.); (M.P.)
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Josefina Prat
- Department of Pharmacy, Pharmaceutical Technology and Physical Chemistry, Faculty of Pharmacy, University of Barcelona, 08028 Barcelona, Spain; (G.E.); (A.O.); (M.E.); (J.P.); (M.M.); (A.C.); (A.C.C.); (M.L.G.); (M.P.)
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Montserrat Muñoz
- Department of Pharmacy, Pharmaceutical Technology and Physical Chemistry, Faculty of Pharmacy, University of Barcelona, 08028 Barcelona, Spain; (G.E.); (A.O.); (M.E.); (J.P.); (M.M.); (A.C.); (A.C.C.); (M.L.G.); (M.P.)
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Amanda Cano
- Department of Pharmacy, Pharmaceutical Technology and Physical Chemistry, Faculty of Pharmacy, University of Barcelona, 08028 Barcelona, Spain; (G.E.); (A.O.); (M.E.); (J.P.); (M.M.); (A.C.); (A.C.C.); (M.L.G.); (M.P.)
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
- Center for Biomedical Research in Neurodegenerative Diseases Network (CIBERNED), Carlos III Health Institute, 28031 Madrid, Spain; (M.E.); (A.C.)
| | - Ana Cristina Calpena
- Department of Pharmacy, Pharmaceutical Technology and Physical Chemistry, Faculty of Pharmacy, University of Barcelona, 08028 Barcelona, Spain; (G.E.); (A.O.); (M.E.); (J.P.); (M.M.); (A.C.); (A.C.C.); (M.L.G.); (M.P.)
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Miren Ettcheto
- Center for Biomedical Research in Neurodegenerative Diseases Network (CIBERNED), Carlos III Health Institute, 28031 Madrid, Spain; (M.E.); (A.C.)
- Department of Pharmacology, Toxicology and Therapeutic Chemistry, Faculty of Pharmacy, University of Barcelona, 08028 Barcelona, Spain
| | - Antoni Camins
- Center for Biomedical Research in Neurodegenerative Diseases Network (CIBERNED), Carlos III Health Institute, 28031 Madrid, Spain; (M.E.); (A.C.)
- Department of Pharmacology, Toxicology and Therapeutic Chemistry, Faculty of Pharmacy, University of Barcelona, 08028 Barcelona, Spain
| | - Zaid Alsafi
- Glaucoma and Retinal Neurodegeneration Research Visual Neuroscience, UCL Institute of Ophthalmology, Bath Street, London EC1V 9EL, UK;
| | - Eliana B. Souto
- Department of Pharmaceutical Technology, Faculty of Pharmacy, University of Coimbra, Pólo das Ciências da Saúde, Azinhaga de Santa Comba, 3000-548 Coimbra, Portugal;
- CEB—Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
| | - Maria Luisa García
- Department of Pharmacy, Pharmaceutical Technology and Physical Chemistry, Faculty of Pharmacy, University of Barcelona, 08028 Barcelona, Spain; (G.E.); (A.O.); (M.E.); (J.P.); (M.M.); (A.C.); (A.C.C.); (M.L.G.); (M.P.)
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
- Center for Biomedical Research in Neurodegenerative Diseases Network (CIBERNED), Carlos III Health Institute, 28031 Madrid, Spain; (M.E.); (A.C.)
| | - Montserrat Pujol
- Department of Pharmacy, Pharmaceutical Technology and Physical Chemistry, Faculty of Pharmacy, University of Barcelona, 08028 Barcelona, Spain; (G.E.); (A.O.); (M.E.); (J.P.); (M.M.); (A.C.); (A.C.C.); (M.L.G.); (M.P.)
- Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
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5
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Kateh Shamshiri M, Momtazi-Borojeni AA, Khodabandeh Shahraky M, Rahimi F. Lecithin soybean phospholipid nano-transfersomes as potential carriers for transdermal delivery of the human growth hormone. J Cell Biochem 2019; 120:9023-9033. [PMID: 30506803 DOI: 10.1002/jcb.28176] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2018] [Accepted: 11/12/2018] [Indexed: 12/28/2022]
Abstract
Pharmaceutical molecules such as peptides and proteins are usually injected into the body. Numerous efforts have been made to find new noninvasive ways to administer these peptides. In this study, highly flexible vesicles (transfersomes [TFs]) were designed as a new modern transdermal drug delivery system for systemic drug administration through the skin, which had also been evaluated in vitro. In this study, two growth hormone-loaded TF formulations were prepared, using soybean lecithin and two different surfactants; F1 _sodium deoxycholate and F 2 _sodium lauryl sulfate. Thereafter, the amount of skin penetration by the two formulas was assessed using the Franz diffusion cell system. TF formulations were evaluated for size, zeta potential and in vitro skin penetration across the rat skin. Results indicated that vesicle formulations were stable for 4 weeks and their mean sizes were 241.33 ± 17 and 171 ± 12.12 nm in the F 1 and F 2 formulation, respectively. After application to rat skin, transport of the human growth hormone (hGH) released from the TF formulations was found to be higher than that of the hGH alone. Maximum amounts of transdermal hormone delivery were estimated to be 489.54 ± 8.301 and 248.46 ± 4.019 ng·cm-2 , for F 1 and F 2 , respectively. The results demonstrate the capability of the TF-containing growth hormone in transdermal delivery and superiority of the F 1 to F 2 TFs.
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Affiliation(s)
- Maryam Kateh Shamshiri
- Department of Biology, Faculty of Science, Islamic Azad University, Science and Research Branch, Tehran, Iran
| | - Amir Abbas Momtazi-Borojeni
- Division of Nanotechnology Research Center, Bu-Ali Research Institute, Mashhad University of Medical Sciences, Mashhad, Iran
- Department of Medical Biotechnology, Student Research Committee, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Mahvash Khodabandeh Shahraky
- Division of Industrial and Environmental Biotechnology (IIEB), National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran
| | - Fatemeh Rahimi
- Division of Industrial and Environmental Biotechnology (IIEB), National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran
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6
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Cyboran-Mikołajczyk S, Żyłka R, Jurkiewicz P, Pruchnik H, Oszmiański J, Hof M, Kleszczyńska H. Interaction of procyanidin B 3 with membrane lipids – Fluorescence, DSC and FTIR studies. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:1362-1371. [DOI: 10.1016/j.bbamem.2017.04.026] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 04/05/2017] [Accepted: 04/28/2017] [Indexed: 12/22/2022]
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7
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Richens JL, Lane JS, Bramble JP, O'Shea P. The electrical interplay between proteins and lipids in membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:1828-36. [DOI: 10.1016/j.bbamem.2015.03.017] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Revised: 03/16/2015] [Accepted: 03/18/2015] [Indexed: 11/17/2022]
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8
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9
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Ostroumova OS, Efimova SS, Schagina LV. Changes of dipole potential of phospholipid membranes resulted from flavonoid adsorption. Biophysics (Nagoya-shi) 2013. [DOI: 10.1134/s0006350913030123] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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10
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Orsi M, Essex JW. Physical properties of mixed bilayers containing lamellar and nonlamellar lipids: insights from coarse-grain molecular dynamics simulations. Faraday Discuss 2013; 161:249-72; discussion 273-303. [DOI: 10.1039/c2fd20110k] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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11
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Efimova SS, Ostroumova OS. Effect of dipole modifiers on the magnitude of the dipole potential of sterol-containing bilayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:9908-14. [PMID: 22702338 DOI: 10.1021/la301653s] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The effects of various subclasses of flavonoids, Rose Bengal, and different styrylpyridinium dyes on the magnitude of the dipole potential of membranes composed of pure phospholipids and sterol-containing bilayers were investigated. Changes in the steady-state membrane conductance induced by cation-ionophore complexes were measured to examine the changes in the dipole potential of lipid bilayers. The characteristic parameters of the Langmuir adsorption isotherm for different flavonoids and Rose Bengal and the slope of the linear dependence of the dipole potential change on the aqueous concentrations of RH dyes were estimated. Chalcones (phloretin and phloridzin) and flavonols (quercetin and myricetin) strictly decrease the dipole potential of phospholipid- and sterol-containing membranes; the unsaturation of the C-ring and the hydrophobicity of the molecule contribute to the ability of the flavonoid to reduce the bilayer dipole potential. Rose Bengal decreases the magnitude of the bilayer dipole potential to a similar extent, but its affinity for membrane lipids is higher; the effects of RH dyes, chalcones, and phloroglucinol are determined by sterol concentration and type.
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Affiliation(s)
- Svetlana S Efimova
- Institute of Cytology of the Russian Academy of Sciences, St. Petersburg 194064, Russia
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12
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Abstract
There are three kinds of membrane potentials: the surface potentials, resulting from the accumulation of charges at the membrane surfaces; the transmembrane potential, determined by imbalance of charge in the aqueous solutions; and the dipole potential, a membrane-internal potential from the dipolar components of the phospholipids and interface water. The absolute value of the dipole potential has been very difficult to measure, although its value has been estimated to be in the range of 200-1,000 mV from ion translocation rates (determined by the planar lipid bilayer method), the surface potential of lipid monolayers (determined by the lipid monolayer method), molecular-dynamics calculations, and electron scattering using cryoelectron microscopy (cryo-EM). Spectroscopy methods have also been used to monitor the dipole potential changes on the basis of the observed fluorescence changes of voltage-sensitive probes. The dipole potential accounts for the much larger permeability of a bare phospholipid membrane to anions than cations and affects the conformation and function of membrane proteins.
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Affiliation(s)
- Liguo Wang
- Department of Biological Structure, University of Washington, Seattle, Washington 98195, USA.
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13
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Ostroumova OS, Efimova SS, Schagina LV. Probing amphotericin B single channel activity by membrane dipole modifiers. PLoS One 2012; 7:e30261. [PMID: 22276169 PMCID: PMC3261894 DOI: 10.1371/journal.pone.0030261] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Accepted: 12/12/2011] [Indexed: 12/03/2022] Open
Abstract
The effects of dipole modifiers and their structural analogs on the single channel activity of amphotericin B in sterol-containing planar phosphocholine membranes are studied. It is shown that the addition of phloretin in solutions bathing membranes containing cholesterol or ergosterol decreases the conductance of single amphotericin B channels. Quercetin decreases the channel conductance in cholesterol-containing bilayers while it does not affect the channel conductance in ergosterol-containing membranes. It is demonstrated that the insertion of styryl dyes, such as RH 421, RH 237 or RH 160, in bilayers with either cholesterol or ergosterol leads to the increase of the current amplitude of amphotericin B pores. Introduction of 5α-androstan-3β-ol into a membrane-forming solution increases the amphotericin B channel conductance in a concentration-dependent manner. All the effects are likely to be attributed to the influence of the membrane dipole potential on the conductance of single amphotericin B channels. However, specific interactions of some dipole modifiers with polyene-sterol complexes might also contribute to the activity of single amphotericin B pores. It has been shown that the channel dwell time increases with increasing sterol concentration, and it is higher for cholesterol-containing membranes than for bilayers including ergosterol, 6-ketocholestanol, 7-ketocholestanol or 5α-androstan-3β-ol. These findings suggest that the processes of association/dissociation of channel forming molecules depend on the membrane fluidity.
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Affiliation(s)
- Olga S Ostroumova
- Institute of Cytology of the Russian Academy of Sciences, St. Petersburg, Russia.
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14
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Orsi M, Essex JW. The ELBA force field for coarse-grain modeling of lipid membranes. PLoS One 2011; 6:e28637. [PMID: 22194874 PMCID: PMC3241685 DOI: 10.1371/journal.pone.0028637] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Accepted: 11/11/2011] [Indexed: 02/05/2023] Open
Abstract
A new coarse-grain model for molecular dynamics simulation of lipid membranes is presented. Following a simple and conventional approach, lipid molecules are modeled by spherical sites, each representing a group of several atoms. In contrast to common coarse-grain methods, two original (interdependent) features are here adopted. First, the main electrostatics are modeled explicitly by charges and dipoles, which interact realistically through a relative dielectric constant of unity (ε(r) = 1). Second, water molecules are represented individually through a new parametrization of the simple Stockmayer potential for polar fluids; each water molecule is therefore described by a single spherical site embedded with a point dipole. The force field is shown to accurately reproduce the main physical properties of single-species phospholipid bilayers comprising dioleoylphosphatidylcholine (DOPC) and dioleoylphosphatidylethanolamine (DOPE) in the liquid crystal phase, as well as distearoylphosphatidylcholine (DSPC) in the liquid crystal and gel phases. Insights are presented into fundamental properties and phenomena that can be difficult or impossible to study with alternative computational or experimental methods. For example, we investigate the internal pressure distribution, dipole potential, lipid diffusion, and spontaneous self-assembly. Simulations lasting up to 1.5 microseconds were conducted for systems of different sizes (128, 512 and 1058 lipids); this also allowed us to identify size-dependent artifacts that are expected to affect membrane simulations in general. Future extensions and applications are discussed, particularly in relation to the methodology's inherent multiscale capabilities.
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Affiliation(s)
- Mario Orsi
- School of Chemistry, University of Southampton, Southampton, United Kingdom.
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15
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Orsi M, Noro MG, Essex JW. Dual-resolution molecular dynamics simulation of antimicrobials in biomembranes. J R Soc Interface 2011; 8:826-41. [PMID: 21131331 PMCID: PMC3104353 DOI: 10.1098/rsif.2010.0541] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2010] [Accepted: 11/09/2010] [Indexed: 11/12/2022] Open
Abstract
Triclocarban and triclosan, two potent antibacterial molecules present in many consumer products, have been subject to growing debate on a number of issues, particularly in relation to their possible role in causing microbial resistance. In this computational study, we present molecular-level insights into the interaction between these antimicrobial agents and hydrated phospholipid bilayers (taken as a simple model for the cell membrane). Simulations are conducted by a novel 'dual-resolution' molecular dynamics approach which combines accuracy with efficiency: the antimicrobials, modelled atomistically, are mixed with simplified (coarse-grain) models of lipids and water. A first set of calculations is run to study the antimicrobials' transfer free energies and orientations as a function of depth inside the membrane. Both molecules are predicted to preferentially accumulate in the lipid headgroup-glycerol region; this finding, which reproduces corresponding experimental data, is also discussed in terms of a general relation between solute partitioning and the intramembrane distribution of pressure. A second set of runs involves membranes incorporated with different molar concentrations of antimicrobial molecules (up to one antimicrobial per two lipids). We study the effects induced on fundamental membrane properties, such as the electron density, lateral pressure and electrical potential profiles. In particular, the analysis of the spontaneous curvature indicates that increasing antimicrobial concentrations promote a 'destabilizing' tendency towards non-bilayer phases, as observed experimentally. The antimicrobials' influence on the self-assembly process is also investigated. The significance of our results in the context of current theories of antimicrobial action is discussed.
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Affiliation(s)
- Mario Orsi
- School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK
| | - Massimo G. Noro
- Unilever R&D Port Sunlight, Quarry Road East, Bebington, Wirral, CH63 3JW, UK
| | - Jonathan W. Essex
- School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK
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16
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Characterization and In Vitro Skin Permeation of Meloxicam-Loaded Liposomes versus Transfersomes. JOURNAL OF DRUG DELIVERY 2010; 2011:418316. [PMID: 21490750 PMCID: PMC3066552 DOI: 10.1155/2011/418316] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/16/2010] [Revised: 09/11/2010] [Accepted: 10/18/2010] [Indexed: 11/18/2022]
Abstract
The goal of this study was to develop and evaluate the potential use of liposome and transfersome vesicles in the transdermal drug delivery of meloxicam (MX). MX-loaded vesicles were prepared and evaluated for particle size, zeta potential, entrapment efficiency (%EE), loading efficiency, stability, and in vitro skin permeation. The vesicles were spherical in structure, 90 to 140 nm in size, and negatively charged (−23 to −43 mV). The %EE of MX in the vesicles ranged from 40 to 70%. Transfersomes provided a significantly higher skin permeation of MX compared to liposomes. Fourier Transform Infrared Spectroscopy (FT-IR) and Differential Scanning Calorimetry (DSC) analysis indicated that the application of transfersomes significantly disrupted the stratum corneum lipid. Our research suggests that MX-loaded transfersomes can be potentially used as a transdermal drug delivery system.
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Orsi M, Michel J, Essex JW. Coarse-grain modelling of DMPC and DOPC lipid bilayers. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:155106. [PMID: 21389551 DOI: 10.1088/0953-8984/22/15/155106] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Our recently developed coarse-grain model for dimyristoylphosphatidylcholine (DMPC) has been improved and extended to dioleylphosphatidylcholine (DOPC), a more typical constituent of real biological membranes. Single-component DMPC and DOPC bilayers have been simulated using microsecond-long molecular dynamics. We investigated properties that are difficult or impossible to access experimentally, such as the pressure distribution, the spontaneous curvature and the diffusion pattern of individual lipid molecules. Moreover, we studied the dipole potential, a basic physical feature of paramount biological importance that cannot be currently modelled by other coarse-grain approaches. In fact, a complete representation of the system electrostatics and a realistic description of the water component make our method unique amongst the existing coarse-grain membrane models. The spontaneous permeation of water, a phenomenon out of reach of standard atomistic models, was also observed and quantified; this was possible thanks to the efficiency of our model, which is about two orders of magnitude less computationally expensive than atomic-level counterparts. Results are generally in good agreement with the literature data. Further model extensions and future applications are proposed.
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Affiliation(s)
- Mario Orsi
- School of Chemistry, University of Southampton, Southampton SO17 1BJ, UK
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The local electric field within phospholipid membranes modulates the charge transfer reactions in reaction centres. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:1039-49. [DOI: 10.1016/j.bbabio.2009.03.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2009] [Revised: 03/03/2009] [Accepted: 03/05/2009] [Indexed: 11/19/2022]
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Starke-Peterkovic T, Clarke RJ. Effect of headgroup on the dipole potential of phospholipid vesicles. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 39:103-10. [PMID: 19132364 DOI: 10.1007/s00249-008-0392-y] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2008] [Revised: 12/01/2008] [Accepted: 12/08/2008] [Indexed: 11/25/2022]
Abstract
The dipole potentials, psi (d), of phospholipid vesicles composed of pure dimyristoylphosphatidylcholine (DMPC) or vesicles in which 50 mol% of the DMPC was substituted by dimyristoylphosphatidylserine (DMPS), dimyristoylphosphatidylglycerol (DMPG), dimyristoylethanolamine (DMPE), dimyristoylphosphatidic acid (DMPA) or monomyristoylphosphatidylcholine (MMPC) were measured via a fluorescent ratiometric method utilizing the probe di-8-ANEPPS. The PS and PG headgroups were found to cause only minor changes in psi (d). PE caused an increase in psi (d) of 51 mV. This could be explained by a decrease in the dielectric constant of the glycerol backbone region as well as a movement of the P(-)-N(+) dipole of the less bulky PE headgroup to a position more parallel to the membrane surface than in PC. The negatively charged PA headgroup increases psi (d) by 215 mV relative to PC alone. This indicates that the positive pole of the dipole predominantly responsible for the dipole potential is located at a position closer to the interior of the membrane than the phosphate group. The increase in the charge of the negative pole of the dipole by the phosphate group of PA increases the electrical potential drop across the lipid headgroup region. The incorporation of the single chain lipid MMPC into the membrane causes a decrease in psi (d) of 142 mV. This can be explained by a decrease in packing density within the membrane of carbonyl dipoles from the sn-2 chain of DMPC. The results presented should contribute to a better understanding of the electrical effect of lipid headgroups on the functioning of membrane proteins.
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Membrane dipole potential of interaction between amyloid protein and phospholipid membranes is dependent on protein aggregation state. ACTA ACUST UNITED AC 2008. [DOI: 10.1016/j.jcice.2008.03.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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21
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Matos PM, Gonçalves S, Santos NC. Interaction of peptides with biomembranes assessed by potential-sensitive fluorescent probes. J Pept Sci 2008; 14:407-15. [PMID: 18189333 DOI: 10.1002/psc.1005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Peptide-membrane interaction is an important step to be evaluated in a study of the activity and mode of action of several bioactive peptides. A variety of methods are available; however, few of them satisfy the criteria of being sensitive, biocompatible, versatile, easy to perform, and allowing real-time monitoring as the use of potential-sensitive fluorescent probes. Here we review methods for detecting the effects of membrane-active peptides, even those that are not intrinsically fluorescent, on the different types of membrane potentials, with a special emphasis on studies conducted with living cells. FPE is a probe sensitive to surface potential and detects electrostatic interactions at the water-lipid interface. Di-8-ANEPPS is sensitive to dipole potential and detects membrane incorporations. Transmembrane potential changes reveal major membrane destabilizations, such as in pore formation. The combination of the information obtained from the three potential variations can lead to a more elucidative picture of the mechanisms of the interaction of relevant peptides with biomembranes.
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Affiliation(s)
- Pedro M Matos
- Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Av. Prof. Egas Moniz, 1649-028 Lisboa, Portugal
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22
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Vitha MF, Clarke RJ. Comparison of excitation and emission ratiometric fluorescence methods for quantifying the membrane dipole potential. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:107-14. [PMID: 16904627 DOI: 10.1016/j.bbamem.2006.06.022] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2006] [Revised: 06/28/2006] [Accepted: 06/29/2006] [Indexed: 10/24/2022]
Abstract
We are interested in developing fluorescence methods for quantifying lateral variations in the dipole potential across cell surfaces. Previous work in this laboratory showed that the ratio of fluorescence intensities of the voltage-sensitive dye di-8-ANEPPS using excitation wavelengths at 420 and 520 nm correlates well with measurements of the dipole potential. In the present work we evaluate the use of di-8-ANEPPS and an emission ratiometric method for measuring dipole potentials, as Bullen and Saggau (Biophys. J. 65 (1999) 2272-2287) have done to follow changes in the membrane potential in the presence of an externally applied field. Emission ratiometric methods have distinct advantages over excitation methods when applied to fluorescence microscopy because only a single wavelength is needed for excitation. We found that unlike the excitation ratio, the emission ratio does not correlate with the dipole potential of vesicles made from different lipids. A difference in the behaviour of the emission ratio in saturated compared to unsaturated lipid vesicles was noted. Furthermore, the emission ratio did not respond in the same way as the excitation ratio when cholesterol, 6-ketocholestanol, 7-ketocholesterol, and phloretin were added to dimyristoylphosphatidylcholine (DMPC) vesicles. We attribute the lack of correlation between the emission ratio and the dipole potential to simultaneous changes in membrane fluidity caused by changes in membrane composition, which do not occur when the electric field is externally applied as in the work of Bullen and Saggau. Di-8-ANEPPS can, thus, only be used via an excitation ratiometric method to quantify the dipole potential.
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Affiliation(s)
- Mark F Vitha
- Department of Chemistry, Drake University, Des Moines, Iowa 50311, USA
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Starke-Peterkovic T, Turner N, Vitha MF, Waller MP, Hibbs DE, Clarke RJ. Cholesterol effect on the dipole potential of lipid membranes. Biophys J 2006; 90:4060-70. [PMID: 16513788 PMCID: PMC1459515 DOI: 10.1529/biophysj.105.074666] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2005] [Accepted: 01/18/2006] [Indexed: 01/05/2023] Open
Abstract
The effect of cholesterol removal by methyl-beta-cyclodextrin on the dipole potential, psi(d), of membrane vesicles composed of natural membrane lipids extracted from the kidney and brain of eight vertebrate species was investigated using the voltage-sensitive fluorescent probe di-8-ANEPPS. Cyclodextrin treatment reduced cholesterol levels by on average 80% and this was associated with an average reduction in psi(d) of 50 mV. Measurements of the effect of a range of cholesterol derivatives on the psi(d) of DMPC lipid vesicles showed that the magnitude of the effect correlated with the component of the sterol's dipole moment perpendicular to the membrane surface. The changes in psi(d) observed could not be accounted for solely by the electric field originating from the sterols' dipole moments. Additional factors must arise from sterol-induced changes in lipid packing, which changes the density of dipoles in the membrane, and changes in water penetration into the membrane, which changes the effective dielectric constant of the interfacial region. In DMPC membranes, the cholesterol-induced change in psi(d) was biphasic, i.e., a maximum in psi(d) was observed at approximately 35-45 mol %, after which psi(d) started to decrease. We suggest that this could be associated with a maximum in the strength of DMPC-cholesterol intermolecular forces at this composition.
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Affiliation(s)
- Thomas Starke-Peterkovic
- School of Chemistry, University of Sydney, Sydney NSW 2006, Australia; Department of Biomedical Science, University of Wollongong, Wollongong NSW 2522, Australia; and Department of Chemistry, Drake University, Des Moines, Iowa 50311
| | - Nigel Turner
- School of Chemistry, University of Sydney, Sydney NSW 2006, Australia; Department of Biomedical Science, University of Wollongong, Wollongong NSW 2522, Australia; and Department of Chemistry, Drake University, Des Moines, Iowa 50311
| | - Mark F. Vitha
- School of Chemistry, University of Sydney, Sydney NSW 2006, Australia; Department of Biomedical Science, University of Wollongong, Wollongong NSW 2522, Australia; and Department of Chemistry, Drake University, Des Moines, Iowa 50311
| | - Mark P. Waller
- School of Chemistry, University of Sydney, Sydney NSW 2006, Australia; Department of Biomedical Science, University of Wollongong, Wollongong NSW 2522, Australia; and Department of Chemistry, Drake University, Des Moines, Iowa 50311
| | - David E. Hibbs
- School of Chemistry, University of Sydney, Sydney NSW 2006, Australia; Department of Biomedical Science, University of Wollongong, Wollongong NSW 2522, Australia; and Department of Chemistry, Drake University, Des Moines, Iowa 50311
| | - Ronald J. Clarke
- School of Chemistry, University of Sydney, Sydney NSW 2006, Australia; Department of Biomedical Science, University of Wollongong, Wollongong NSW 2522, Australia; and Department of Chemistry, Drake University, Des Moines, Iowa 50311
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Shynkar VV, Klymchenko AS, Duportail G, Demchenko AP, Mély Y. Two-color fluorescent probes for imaging the dipole potential of cell plasma membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2005; 1712:128-36. [PMID: 15921656 DOI: 10.1016/j.bbamem.2005.03.015] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2004] [Revised: 03/30/2005] [Accepted: 03/31/2005] [Indexed: 11/19/2022]
Abstract
The dipole potential (Psi(d)) constitutes a large and functionally important part of the electrostatic potential of cell plasma membranes. However, its direct measurement is not possible. Herein, new 3-hydroxyflavone fluorescent probes were developed that respond strongly to Psi(d) changes by a variation of the intensity ratio of their two well-separated fluorescence bands. Using fluorescence spectroscopy with cell suspensions and confocal microscopy with adherent cells, we showed, for the first time, two-color fluorescence ratiometric measurement and visualization of Psi(d) in cell plasma membranes. Using this new tool, a heterogeneous distribution of this potential within the membrane was evidenced.
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Affiliation(s)
- Vasyl V Shynkar
- Laboratoire de Pharmacologie et Physicochimie des interactions cellulaires et moléculaires, UMR 7034 du CNRS, Faculté de Pharmacie, Université Louis Pasteur, 67401 Illkirch, France
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Auner BG, O'Neill MAA, Valenta C, Hadgraft J. Interaction of phloretin and 6-ketocholestanol with DPPC-liposomes as phospholipid model membranes. Int J Pharm 2005; 294:149-55. [PMID: 15814239 DOI: 10.1016/j.ijpharm.2005.01.031] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2004] [Revised: 01/10/2005] [Accepted: 01/20/2005] [Indexed: 10/25/2022]
Abstract
Phloretin and 6-ketocholestanol are penetration enhancers for percutaneous delivery of certain topically applied drugs. In the present study some physicochemical experiments have been performed to elucidate the mechanism of action of phloretin and 6-ketocholestanol. The penetration enhancing effect of phloretin and 6-ketocholestanol is believed to be due to their increase of the fluidity of the intercellular lipid bilayers of the stratum corneum. Phospholipid vesicles were chosen as a simple model to represent these bilayers. The effect of phloretin and 6-ketocholestanol on phase transition temperature and enthalpy was studied using differential scanning calorimetry. Beside of that the size of liposomes was monitored when the amount of penetration enhancer in the liposome preparation was changed. Addition of increasing amounts of phloretin and 6-ketocholestanol to the bilayer resulted in lowering of phase transition temperatures and increasing the enthalpy. Additionally the size of the liposomes was increased when penetration enhancer was added. The results suggest that phloretin as well as 6-ketocholestanol would interact with stratum corneum lipids in a similar manner, both reduce the diffusional resistance of the stratum corneum to drugs with balanced hydrophilic-lipophilic characteristics.
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Affiliation(s)
- Barbara G Auner
- Institute of Pharmaceutical Technology and Biopharmaceutics, Centre of Pharmacy, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
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Auner BG, Petzenhauser E, Valenta C. Influence of 6-Ketocholestanol on Skin Permeation of 5-Aminolevulinic Acid and Evaluation of Chemical Stability. J Pharm Sci 2004; 93:2780-7. [PMID: 15378565 DOI: 10.1002/jps.20130] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The ability of 6-ketocholestanol to increase the skin permeation of the prodrug aminolevulinic acid (5-ALA) was investigated. 6-Ketocholestanol was incorporated together with 5-ALA in four different formulations. Preparations used were a liquid solution/suspension of 5-ALA in buffer, 5-ALA in phospholipid liposomal formulations with and without gelating agent, and finally, a complex cream formulation also including phospholipids. Standard diffusion experiments of 5-ALA using Franz-type diffusion cells and porcine skin were performed. Drug stability was monitored by analyzing the 5-ALA content in the different formulations over time and viewing the preparation for microbial contamination. The analysis of 5-ALA as a nonfluorescent probe was performed after chemical reaction, leading to a fluorescent derivative. The 5-ALA permeation through porcine skin was increased threefold by 6-ketocholestanol in the cream formulation. The chemical stability of 5-ALA in the tested formulations was in the range of about 33 to 72% after an observation period of 28 days. After that time point microbial stability was no longer evident for formulations 2 and 3. Formulation 1 could be observed until day 34, and only formulation 4 showed a microbial stability over the whole observation period of 42 days.
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Affiliation(s)
- Barbara Gabriele Auner
- Institute of Pharmaceutical Technology and Biopharmaceutics, Centre of Pharmacy, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
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Abstract
Over the past 30 or so years there has been a considerable advance in our knowledge of the mechanisms of skin permeation. This has largely been brought about by the development of sophisticated biophysical techniques and increased computing powers. The advanced technology has clearly provided indications, at a molecular level, about routes of permeation and how the barrier function can be modulated by excipients with which actives are formulated. This publication reviews some of the advances that have been made and mathematical models that have been constructed to predict percutaneous penetration and transdermal delivery. The models also indicate the various enhancement strategies that can be used in dermal penetration. In the past, it has been difficult to identify precise mechanisms of action of the different classes of enhancer but a combination of appropriate biophysical techniques, mathematical modelling and chemometric analysis can help identify the contributing processes. The models can also be used to indicate rate control in transdermal delivery, whether it is in the applied delivery device or in the skin.
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Valenta C, Steininger A, Auner BG. Phloretin and 6-ketocholestanol: membrane interactions studied by a phospholipid/polydiacetylene colorimetric assay and differential scanning calorimetry. Eur J Pharm Biopharm 2004; 57:329-36. [PMID: 15018992 DOI: 10.1016/j.ejpb.2003.09.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2003] [Revised: 09/26/2003] [Accepted: 09/26/2003] [Indexed: 11/28/2022]
Abstract
The aim of this study was to investigate membrane interactions of phloretin and 6-ketocholestanol using different methods. A previously reported colorimetric assay with phospholipid/polydiacetylene (PDA) vesicles was used to examine a possible interaction of phloretin and 6-ketocholestanol with this target. During this interaction the used aggregates of lipids and conjugated PDA undergo a visible and quantifiable blue to red color transition. A positive result is indicative for a reaction response with membrane lipids of a simplified bilayer structure instead of the complex bilayer system of the stratum corneum. Results of this test confirm previous proposed membrane interactions by skin diffusion studies. Additional differential scanning calorimetry studies with 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes confirm a membrane interaction and indicates that phloretin and 6-ketocholestanol interact with the lipid layer and change structural parameters. They strongly decrease the lipid phase transition temperature of DMPC and DPPC liposomes by at least about 6.6 degrees C and maximally about 13.9 degrees C which refers to a higher fluidity of the membrane.
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Affiliation(s)
- C Valenta
- Institute of Pharmaceutical Technology and Biopharmaceutics, University of Vienna, Vienna, Austria.
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Auner BG, Valenta C, Hadgraft J. Influence of phloretin and 6-ketocholestanol on the skin permeation of sodium-fluorescein. J Control Release 2003; 89:321-8. [PMID: 12711454 DOI: 10.1016/s0168-3659(03)00124-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In the present study, we investigated the feasibility of enhancing the transport of the model drug sodium-fluorescein across rat, porcine and human skin by treating it with phloretin and 6-ketocholestanol. Both 6-ketocholestanol and phloretin were incorporated into unilamellar liposomes and used as a skin pre-treatment. Afterwards standard diffusion experiments with Franz-type diffusion cells were performed. The results indicate a positive effect of 6-ketocholestanol on the sodium-fluorescein diffusion in all skin types, whereas phloretin had no significant influence compared to the control in human skin. In contrast to this, phloretin had a significant positive effect in rat as well as in porcine skin after 30 h of diffusion. In addition to the permeation studies, the human skin samples were analysed by confocal laser scanning microscopy for direct visualisation of the sodium-fluorescein. As expected the results of the diffusion experiments were confirmed by this microscopic method.
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Affiliation(s)
- Barbara G Auner
- Institute of Pharmaceutical Technology and Biopharmaceutics, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria
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