1
|
Speer D, Salvador-Castell M, Huang Y, Liu GY, Sinha SK, Parikh AN. Surfactant-Mediated Structural Modulations to Planar, Amphiphilic Multilamellar Stacks. J Phys Chem B 2023; 127:7497-7508. [PMID: 37584633 PMCID: PMC10476200 DOI: 10.1021/acs.jpcb.3c01654] [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: 03/10/2023] [Revised: 08/01/2023] [Indexed: 08/17/2023]
Abstract
The hydrophobic effect, a ubiquitous process in biology, is a primary thermodynamic driver of amphiphilic self-assembly. It leads to the formation of unique morphologies including two highly important classes of lamellar and micellar mesophases. The interactions between these two types of structures and their involved components have garnered significant interest because of their importance in key biochemical technologies related to the isolation, purification, and reconstitution of membrane proteins. This work investigates the structural organization of mixtures of the lamellar-forming phospholipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and two zwitterionic micelle-forming surfactants, being n-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (Zwittergent 3-12 or DDAPS) and 1-oleoyl-2-hydroxy-sn-glycero-3-phosphocholine (O-Lyso-PC), when assembled by water vapor hydration with X-ray diffraction measurements, brightfield optical microscopy, wide-field fluorescence microscopy, and atomic force microscopy. The results reveal that multilamellar mesophases of these mixtures can be assembled across a wide range of POPC to surfactant (POPC:surfactant) concentration ratios, including ratios far surpassing the classical detergent-saturation limit of POPC bilayers without significant morphological disruptions to the lamellar motif. The mixed mesophases generally decreased in lamellar spacing (D) and headgroup-to-headgroup distance (Dhh) with a higher concentration of the doped surfactant, but trends in water layer thickness (Dw) between each bilayer in the stack are highly variable. Further structural characteristics including mesophase topography, bilayer thickness, and lamellar rupture force were revealed by atomic force microscopy (AFM), exhibiting homogeneous multilamellar stacks with no significant physical differences with changes in the surfactant concentration within the mesophases. Taken together, the outcomes present the assembly of unanticipated and highly unique mixed mesophases with varied structural trends from the involved surfactant and lipidic components. Modulations in their structural properties can be attributed to the surfactant's chemical specificity in relation to POPC, such as the headgroup hydration and the hydrophobic chain tail mismatch. Taken together, our results illustrate how specific chemical complexities of surfactant-lipid interactions can alter the morphologies of mixed mesophases and thereby alter the kinetic pathways by which surfactants dissolve lipid mesophases in bulk aqueous solutions.
Collapse
Affiliation(s)
- Daniel
J. Speer
- Chemistry
Graduate Group, University of California,
Davis, One Shields Avenue, Davis, California 95616, United States
| | - Marta Salvador-Castell
- Department
of Physics, University of California, San
Diego, 9500 Gilman Drive, La Jolla, California 92093, United States
| | - Yuqi Huang
- Department
of Chemistry, University of California,
Davis, One Shields Avenue, Davis, California 95616, United States
| | - Gang-Yu Liu
- Department
of Chemistry, University of California,
Davis, One Shields Avenue, Davis, California 95616, United States
| | - Sunil K. Sinha
- Department
of Physics, University of California, San
Diego, 9500 Gilman Drive, La Jolla, California 92093, United States
| | - Atul N. Parikh
- Chemistry
Graduate Group, University of California,
Davis, One Shields Avenue, Davis, California 95616, United States
- Department
of Biomedical Engineering, University of
California, Davis, One
Shields Avenue, Davis, California 95616, United States
| |
Collapse
|
2
|
Żak A, Rajtar N, Kulig W, Kepczynski M. Miscibility of Phosphatidylcholines in Bilayers: Effect of Acyl Chain Unsaturation. MEMBRANES 2023; 13:411. [PMID: 37103838 PMCID: PMC10146409 DOI: 10.3390/membranes13040411] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 04/02/2023] [Accepted: 04/03/2023] [Indexed: 06/19/2023]
Abstract
The miscibility of phospholipids in a hydrated bilayer is an issue of fundamental importance for understanding the organization of biological membranes. Despite research on lipid miscibility, its molecular basis remains poorly understood. In this study, all-atom MD simulations complemented by Langmuir monolayer and DSC experiments have been performed to investigate the molecular organization and properties of lipid bilayers composed of phosphatidylcholines with saturated (palmitoyl, DPPC) and unsaturated (oleoyl, DOPC) acyl chains. The experimental results showed that the DOPC/DPPC bilayers are systems exhibiting a very limited miscibility (strongly positive values of excess free energy of mixing) at temperatures below the DPPC phase transition. The excess free energy of mixing is divided into an entropic component, related to the ordering of the acyl chains, and an enthalpic component, resulting from the mainly electrostatic interactions between the headgroups of lipids. MD simulations showed that the electrostatic interactions for lipid like-pairs are much stronger than that for mixed pairs and temperature has only a slight influence on these interactions. On the contrary, the entropic component increases strongly with increasing temperature, due to the freeing of rotation of acyl chains. Therefore, the miscibility of phospholipids with different saturations of acyl chains is an entropy-driven process.
Collapse
Affiliation(s)
- Agata Żak
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Kraków, Poland
| | - Natan Rajtar
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Kraków, Poland
| | - Waldemar Kulig
- Department of Physics, University of Helsinki, P.O. Box 64, FI-00014 Helsinki, Finland
| | - Mariusz Kepczynski
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Kraków, Poland
| |
Collapse
|
3
|
Yakaew S, Luangpradikun K, Phimnuan P, Nuengchamnong N, Kamonsutthipaijit N, Rugmai S, Nakyai W, Ross S, Ungsurungsei M, Viyoch J, Ross G. Investigation into poloxamer 188‐based cubosomes as a polymeric carrier for poor water‐soluble actives. J Appl Polym Sci 2022. [DOI: 10.1002/app.51612] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Swanya Yakaew
- Department of Pharmaceutical Technology, Faculty of Pharmaceutical Sciences and Center of Excellence for Innovation in Chemistry Naresuan University Phitsanulok Thailand
| | - Kunlathida Luangpradikun
- Department of Pharmaceutical Technology, Faculty of Pharmaceutical Sciences and Center of Excellence for Innovation in Chemistry Naresuan University Phitsanulok Thailand
| | - Preeyawass Phimnuan
- Department of Pharmaceutical Technology, Faculty of Pharmaceutical Sciences and Center of Excellence for Innovation in Chemistry Naresuan University Phitsanulok Thailand
| | - Nitra Nuengchamnong
- Science Laboratory Center, Faculty of Science Naresuan University Phitsanulok Thailand
| | | | - Supagorn Rugmai
- Synchrotron Light Research Institute (Public Organization) Nakhon Ratchasima Thailand
| | - Wongnapa Nakyai
- Department of Chemistry, Faculty of Science Ramkhamhaeng University Bangkok Thailand
| | - Sukunya Ross
- Department of Chemistry, Faculty of Science Naresuan University Phitsanulok Thailand
| | - Malyn Ungsurungsei
- Research & Development Division S & J International Enterprises Public Company Limited Bangkok Thailand
| | - Jarupa Viyoch
- Department of Pharmaceutical Technology, Faculty of Pharmaceutical Sciences and Center of Excellence for Innovation in Chemistry Naresuan University Phitsanulok Thailand
| | - Gareth Ross
- Department of Chemistry, Faculty of Science Naresuan University Phitsanulok Thailand
| |
Collapse
|
4
|
Genova J, Chamati H, Petrov M. Study of SOPC with embedded pristine and amide-functionalized single wall carbon nanotubes by DSC and FTIR spectroscopy. Colloids Surf A Physicochem Eng Asp 2020. [DOI: 10.1016/j.colsurfa.2020.125261] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
|
5
|
Abstract
Many critical biological events, including biochemical signaling, membrane traffic, and cell motility, originate at membrane surfaces. Each such event requires that members of a specific group of proteins and lipids rapidly assemble together at a specific site on the membrane surface. Understanding the biophysical mechanisms that stabilize these assemblies is critical to decoding and controlling cellular functions. In this article, we review progress toward a quantitative biophysical understanding of the mechanisms that drive membrane heterogeneity and organization. We begin from a physical perspective, reviewing the fundamental principles and key experimental evidence behind each proposed mechanism. We then shift to a biological perspective, presenting key examples of the role of heterogeneity in biology and asking which physical mechanisms may be responsible. We close with an applied perspective, noting that membrane heterogeneity provides a novel therapeutic target that is being exploited by a growing number of studies at the interface of biology, physics, and engineering.
Collapse
Affiliation(s)
- Wade F Zeno
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas 78712, USA;
| | - Kasey J Day
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas 78712, USA;
| | - Vernita D Gordon
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA
- Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA
- Center for Nonlinear Dynamics, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Jeanne C Stachowiak
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas 78712, USA;
- Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA
| |
Collapse
|
6
|
Carpenter TS, López CA, Neale C, Montour C, Ingólfsson HI, Di Natale F, Lightstone FC, Gnanakaran S. Capturing Phase Behavior of Ternary Lipid Mixtures with a Refined Martini Coarse-Grained Force Field. J Chem Theory Comput 2018; 14:6050-6062. [DOI: 10.1021/acs.jctc.8b00496] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Timothy S. Carpenter
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | | | | | - Cameron Montour
- Biochemistry and Molecular Biology Department, Georgetown University, Washington, DC 20057, United States
| | - Helgi I. Ingólfsson
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Francesco Di Natale
- Applications, Simulations, and Quality Division, Computation Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Felice C. Lightstone
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | | |
Collapse
|
7
|
Ali MA, Kataoka N, Ranneh AH, Iwao Y, Noguchi S, Oka T, Itai S. Enhancing the Solubility and Oral Bioavailability of Poorly Water-Soluble Drugs Using Monoolein Cubosomes. Chem Pharm Bull (Tokyo) 2017; 65:42-48. [PMID: 28049915 DOI: 10.1248/cpb.c16-00513] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Monoolein cubosomes containing either spironolactone (SPI) or nifedipine (NI) were prepared using a high-pressure homogenization technique and characterized in terms of their solubility and oral bioavailability. The mean particle size, polydispersity index (PDI), zeta potential, solubility and encapsulation efficiency (EE) values of the SPI- and NI-loaded cubosomes were determined to be 90.4 nm, 0.187, -13.4 mV, 163 µg/mL and 90.2%, and 91.3 nm, 0.168, -12.8 mV, 189 µg/mL and 93.0%, respectively, which were almost identical to those of the blank cubosome. Small-angle X-ray scattering analyses confirmed that the SPI-loaded, NI-loaded and blank cubosomes existed in the cubic space group Im3̄m. The lattice parameters of the SPI- and NI-loaded cubosomes were 147.6 and 151.6 Å, respectively, making them almost identical to that of blank cubosome (151.0 Å). The in vitro release profiles of the SPI- and NI-loaded cubosomes showed that they released less than 5% of the drugs into various media over 12-48 h, indicating that most of the drug remained encapsulated within the cubic phase of their lipid bilayer. Furthermore, the in vivo pharmacokinetic results suggested that these cubosomes led to a considerable increase in the systemic oral bioavailability of the drugs compared with pure dispersions of the same materials. Notably, the stability results indicated that the mean particle size and PDI values of these cubosomes were stable for at least 4 weeks. Taken together, these results demonstrate that monoolein cubosomes represent promising drug carriers for enhancing the solubility and oral bioavailability of poorly water-soluble drugs.
Collapse
Affiliation(s)
- Md Ashraf Ali
- Department of Pharmaceutical Engineering & Drug Delivery Science, Graduate School of Integrated Pharmaceutical & Nutritional Sciences, University of Shizuoka
| | | | | | | | | | | | | |
Collapse
|
8
|
Schmid F. Physical mechanisms of micro- and nanodomain formation in multicomponent lipid membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1859:509-528. [PMID: 27823927 DOI: 10.1016/j.bbamem.2016.10.021] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 10/19/2016] [Accepted: 10/27/2016] [Indexed: 12/17/2022]
Abstract
This article summarizes a variety of physical mechanisms proposed in the literature, which can generate micro- and nanodomains in multicomponent lipid bilayers and biomembranes. It mainly focusses on lipid-driven mechanisms that do not involve direct protein-protein interactions. Specifically, it considers (i) equilibrium mechanisms based on lipid-lipid phase separation such as critical cluster formation close to critical points, and multiple domain formation in curved geometries, (ii) equilibrium mechanisms that stabilize two-dimensional microemulsions, such as the effect of linactants and the effect of curvature-composition coupling in bilayers and monolayers, and (iii) non-equilibrium mechanisms induced by the interaction of a biomembrane with the cellular environment, such as membrane recycling and the pinning effects of the cytoplasm. Theoretical predictions are discussed together with simulations and experiments. The presentation is guided by the theory of phase transitions and critical phenomena, and the appendix summarizes the mathematical background in a concise way within the framework of the Ginzburg-Landau theory. This article is part of a Special Issue entitled: Lipid order/lipid defects and lipid-control of protein activity edited by Dirk Schneider.
Collapse
Affiliation(s)
- Friederike Schmid
- Institute of Physics, Johannes Gutenberg University, 55099 Mainz, Germany
| |
Collapse
|
9
|
Douliez JP, Houssou BH, Fameau AL, Navailles L, Nallet F, Grélard A, Dufourc EJ, Gaillard C. Self-Assembly of Bilayer Vesicles Made of Saturated Long Chain Fatty Acids. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:401-410. [PMID: 26700689 DOI: 10.1021/acs.langmuir.5b03627] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Saturated long chain fatty acids (sLCFA, e.g., C14:0, C16:0, and C18:0) are potentially the greenest and cheapest surfactants naturally available. However, because aqueous sodium soaps of sLCFA are known to crystallize, the self-assembly of stable bilayer vesicles has not been reported yet. Here, by using such soaps in combination with guanidine hydrochloride (GuHCl), which has been shown recently to prevent crystallization, we were capable of producing stable bilayer vesicles made of sLCFA. The phase diagrams were established for a variety of systems showing that vesicles can form in a broad range of composition and pH. Both solid state NMR and small-angle neutron scattering allowed demonstrating that in such vesicles sLCFA are arranged in a bilayer structure which exhibits similar dynamic and structural properties as those of phospholipid membranes. We expect these vesicles to be of interest as model systems of protocells and minimal cells but also for various applications since fatty acids are potentially substitutes to phospholipids, synthetic surfactants, and polymers.
Collapse
Affiliation(s)
- Jean-Paul Douliez
- UMR 1332, biologie et pathologie du fruit, INRA , centre de Bordeaux, 33883 Villenave d'Ornon, France
| | | | - A-Laure Fameau
- UR 1268 Biopolymères Interactions et Assemblages, INRA , rue de la Géraudière, 44316 Nantes, France
| | | | | | | | | | - Cédric Gaillard
- UR 1268 Biopolymères Interactions et Assemblages, INRA , rue de la Géraudière, 44316 Nantes, France
| |
Collapse
|
10
|
Ali MA, Noguchi S, Iwao Y, Oka T, Itai S. Preparation and Characterization of SN-38-Encapsulated Phytantriol Cubosomes Containing α-Monoglyceride Additives. Chem Pharm Bull (Tokyo) 2016; 64:577-84. [DOI: 10.1248/cpb.c15-00984] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Md Ashraf Ali
- Laboratory of Pharmaceutical Engineering & Drug Delivery Science, Graduate School of Integrated Pharmaceutical & Nutritional Sciences, University of Shizuoka
- Department of Pharmacy, Faculty of Life Science, Mawlana Bhashani Science and Technology University
| | - Shuji Noguchi
- Laboratory of Pharmaceutical Engineering & Drug Delivery Science, Graduate School of Integrated Pharmaceutical & Nutritional Sciences, University of Shizuoka
| | - Yasunori Iwao
- Laboratory of Pharmaceutical Engineering & Drug Delivery Science, Graduate School of Integrated Pharmaceutical & Nutritional Sciences, University of Shizuoka
| | - Toshihiko Oka
- Department of Physics, Faculty of Science and Nanomaterials Research Division, Research Institute of Electronics, Shizuoka University
| | - Shigeru Itai
- Laboratory of Pharmaceutical Engineering & Drug Delivery Science, Graduate School of Integrated Pharmaceutical & Nutritional Sciences, University of Shizuoka
| |
Collapse
|
11
|
Vargas C, Arenas RC, Frotscher E, Keller S. Nanoparticle self-assembly in mixtures of phospholipids with styrene/maleic acid copolymers or fluorinated surfactants. NANOSCALE 2015; 7:20685-96. [PMID: 26599076 DOI: 10.1039/c5nr06353a] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Self-assembling nanostructures in aqueous mixtures of bilayer-forming lipids and micelle-forming surfactants are relevant to in vitro studies on biological and synthetic membranes and membrane proteins. Considerable efforts are currently underway to replace conventional detergents by milder alternatives such as styrene/maleic acid (SMA) copolymers and fluorinated surfactants. However, these compounds and their nanosized assemblies remain poorly understood as regards their interactions with lipid membranes, particularly, the thermodynamics of membrane partitioning and solubilisation. Using (19)F and (31)P nuclear magnetic resonance spectroscopy, static and dynamic light scattering, and isothermal titration calorimetry, we have systematically investigated the aggregational state of a zwitterionic bilayer-forming phospholipid upon exposure to an SMA polymer with a styrene/maleic acid ratio of 3 : 1 or to a fluorinated octyl phosphocholine derivative called F(6)OPC. The lipid interactions of SMA(3 : 1) and F(6)OPC can be thermodynamically conceptualised within the framework of a three-stage model that treats bilayer vesicles, discoidal or micellar nanostructures, and the aqueous solution as distinct pseudophases. The exceptional solubilising power of SMA(3 : 1) is reflected in very low membrane-saturating and solubilising polymer/lipid molar ratios of 0.10 and 0.15, respectively. Although F(6)OPC saturates bilayers at an even lower molar ratio of 0.031, this nondetergent does not solubilise lipids even at >1000-fold molar excess, thus highlighting fundamental differences between these two types of mild membrane-mimetic systems. We rationalise these findings in terms of a new classification of surfactants based on bilayer-to-micelle transfer free energies and discuss practical implications for membrane-protein research.
Collapse
Affiliation(s)
- Carolyn Vargas
- Molecular Biophysics, University of Kaiserslautern, Erwin-Schrödinger-Str. 13, 67663 Kaiserslautern, Germany.
| | | | | | | |
Collapse
|
12
|
Musgrove A, Bizzotto D. Potential Controls the Interaction of Liposomes with Octadecanol-Modified Au Electrodes: An in Situ AFM Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:12797-12806. [PMID: 26528884 DOI: 10.1021/acs.langmuir.5b03605] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The formation of supported lipid bilayers using liposomes requires interaction with the solid surface, rupture of the liposome, and spreading to cover the surface with a lipid bilayer. This can result in a less-than-uniform coating of the solid surface. Presented is a method that uses the electrochemical poration of an adsorbed lipid-like layer on a Au electrode to control the interaction of 100 nm DOPC liposomes. An octadecanol-coated Au-on-mica surface was imaged using tapping-mode AFM during the application of potential in the presence or absence of liposomes. When the substrate potential was made negative enough, defects formed in the adsorbed layer and new taller features were observed. More features were observed and existing features increased in size with time spent at this negative poration potential. The new features were 1.8-2.0 nm higher than the octadecanol-coated gold surface, half the thickness of a DOPC bilayer. These features were not observed in the absence of liposomes when undergoing the same potential perturbation. In the presence of liposomes, the application of a poration potential was needed to initiate the formation of these taller features. Once the applied potential was removed, the features stopped growing and no new regions were observed. The size of these new regions was consistent with the footprint of a flattened 100 nm liposome. It is speculated that the DOPC liposomes were able to interact with the defects and became soluble in the octadecanol, creating a taller region that was limited in size to the liposome that adsorbed and became incorporated. This AFM study confirms previous in situ fluorescence measurements of the same system and illustrates the use of a potential perturbation to control the formation of these regions of increased DOPC content.
Collapse
Affiliation(s)
- Amanda Musgrove
- AMPEL, Department of Chemistry, University of British Columbia , Vancouver, British Columbia V6T 1Z4, Canada
| | - Dan Bizzotto
- AMPEL, Department of Chemistry, University of British Columbia , Vancouver, British Columbia V6T 1Z4, Canada
| |
Collapse
|
13
|
Wang M, Zander T, Liu X, Liu C, Raj A, Florian Wieland D, Garamus VM, Willumeit-Römer R, Claesson PM, Dėdinaitė A. The effect of temperature on supported dipalmitoylphosphatidylcholine (DPPC) bilayers: Structure and lubrication performance. J Colloid Interface Sci 2015; 445:84-92. [DOI: 10.1016/j.jcis.2014.12.042] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Revised: 12/09/2014] [Accepted: 12/11/2014] [Indexed: 10/24/2022]
|
14
|
Chong JYT, Mulet X, Keddie DJ, Waddington L, Mudie ST, Boyd BJ, Drummond CJ. Novel steric stabilizers for lyotropic liquid crystalline nanoparticles: PEGylated-phytanyl copolymers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:2615-2629. [PMID: 25068381 DOI: 10.1021/la501471z] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Lyotropic liquid crystalline nanostructured particles (e.g., cubosomes and hexosomes) are being investigated as delivery systems for therapeutics in biomedical and pharmaceutical applications. Long term stability of these particulate dispersions is generally provided by steric stabilizers, typically commercially available amphiphilic copolymers such as Pluronic F127. Few examples exist of tailored molecular materials designed for lyotropic liquid crystalline nanostructured particle stabilization. A library of PEGylated-phytanyl copolymers (PEG-PHYT) with varying PEG molecular weights (200-14K Da) was synthesized to assess their performance as steric stabilizers for cubosomes and to establish structure-property relationships. The PEGylated-lipid copolymers were first found to self-assemble in excess water in the absence of cubosomes and also displayed thermotropic liquid crystal phase behavior under cross-polarized light microscopy. An accelerated stability assay was used to assess the performance of the copolymers, compared to Pluronic F127, for stabilizing phytantriol-based cubosomes. Several of the PEGylated-lipid copolymers showed steric stabilizer effectiveness comparable to Pluronic F127. Using synchrotron small-angle X-ray scattering and cryo-transmission electron microscopy, the copolymers were shown to retain the native internal lyotropic liquid crystalline structure, double diamond cubic phase (Q2(D)), of phytantriol dispersions; an important attribute for controlling downstream performance.
Collapse
Affiliation(s)
- Josephine Y T Chong
- CSIRO Materials Science and Engineering, Private Bag 10, Clayton, VIC 3169, Australia
| | | | | | | | | | | | | |
Collapse
|
15
|
Gerelli Y, de Ghellinck A, Jouhet J, Laux V, Haertlein M, Fragneto G. Multi-lamellar organization of fully deuterated lipid extracts of yeast membranes. ACTA ACUST UNITED AC 2014; 70:3167-76. [PMID: 25478835 DOI: 10.1107/s1399004714022913] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Accepted: 10/18/2014] [Indexed: 05/28/2023]
Abstract
Neutron scattering studies on mimetic biomembranes are currently limited by the low availability of deuterated unsaturated lipid species. In the present work, results from the first neutron diffraction experiments on fully deuterated lipid extracts from the yeast Pichia pastoris are presented. The structural features of these fully deuterated lipid stacks are compared with those of their hydrogenous analogues and with other similar synthetic systems. The influence of temperature and humidity on the samples has been investigated by means of small momentum-transfer neutron diffraction. All of the lipid extracts investigated self-assemble into multi-lamellar stacks having different structural periodicities; the stacking distances are affected by temperature and humidity without altering the basic underlying arrangement. At high relative humidity the deuterated and hydrogenous samples are similar in their multi-lamellar arrangement, being characterized by two main periodicities of ∼75 and ∼110 Å reflecting the presence of a large number of polar phospholipid molecules. Larger differences are found at lower relative humidity, where hydrogenous lipids are characterized by a larger single lamellar structure than that observed in the deuterated samples. In both cases the heterogeneity in composition is reflected in a wide structural complexity. The different behaviour upon dehydration can be related to compositional differences in the molecular composition of the two samples, which is attributed to metabolic effects related to the use of perdeuterated growth media.
Collapse
Affiliation(s)
- Yuri Gerelli
- Institut Laue-Langevin, 71 Avenue des Martyrs, 38000 Grenoble, France
| | | | - Juliette Jouhet
- Laboratoire de Physiologie Cellulaire and Végétale (LPCV), CNRS (UMR5168)/Université Grenoble Alpes/INRA (USC1359)/CEA Grenoble, Institut de Recherches en Technologies et Sciences pour le Vivant (iRTSV), 17 Rue des Martyrs, 38054 Grenoble CEDEX 9, France
| | - Valérie Laux
- Institut Laue-Langevin, 71 Avenue des Martyrs, 38000 Grenoble, France
| | - Michael Haertlein
- Institut Laue-Langevin, 71 Avenue des Martyrs, 38000 Grenoble, France
| | - Giovanna Fragneto
- Institut Laue-Langevin, 71 Avenue des Martyrs, 38000 Grenoble, France
| |
Collapse
|
16
|
Fong WK, Hanley TL, Thierry B, Tilley A, Kirby N, Waddington LJ, Boyd BJ. Understanding the photothermal heating effect in non-lamellar liquid crystalline systems, and the design of new mixed lipid systems for photothermal on-demand drug delivery. Phys Chem Chem Phys 2014; 16:24936-53. [DOI: 10.1039/c4cp03635b] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
|
17
|
Fameau AL, Arnould A, Saint-Jalmes A. Responsive self-assemblies based on fatty acids. Curr Opin Colloid Interface Sci 2014. [DOI: 10.1016/j.cocis.2014.08.005] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
18
|
Ramakrishnan N, Sunil Kumar PB, Radhakrishnan R. Mesoscale computational studies of membrane bilayer remodeling by curvature-inducing proteins. PHYSICS REPORTS 2014; 543:1-60. [PMID: 25484487 PMCID: PMC4251917 DOI: 10.1016/j.physrep.2014.05.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Biological membranes constitute boundaries of cells and cell organelles. These membranes are soft fluid interfaces whose thermodynamic states are dictated by bending moduli, induced curvature fields, and thermal fluctuations. Recently, there has been a flood of experimental evidence highlighting active roles for these structures in many cellular processes ranging from trafficking of cargo to cell motility. It is believed that the local membrane curvature, which is continuously altered due to its interactions with myriad proteins and other macromolecules attached to its surface, holds the key to the emergent functionality in these cellular processes. Mechanisms at the atomic scale are dictated by protein-lipid interaction strength, lipid composition, lipid distribution in the vicinity of the protein, shape and amino acid composition of the protein, and its amino acid contents. The specificity of molecular interactions together with the cooperativity of multiple proteins induce and stabilize complex membrane shapes at the mesoscale. These shapes span a wide spectrum ranging from the spherical plasma membrane to the complex cisternae of the Golgi apparatus. Mapping the relation between the protein-induced deformations at the molecular scale and the resulting mesoscale morphologies is key to bridging cellular experiments across the various length scales. In this review, we focus on the theoretical and computational methods used to understand the phenomenology underlying protein-driven membrane remodeling. Interactions at the molecular scale can be computationally probed by all atom and coarse grained molecular dynamics (MD, CGMD), as well as dissipative particle dynamics (DPD) simulations, which we only describe in passing. We choose to focus on several continuum approaches extending the Canham - Helfrich elastic energy model for membranes to include the effect of curvature-inducing proteins and explore the conformational phase space of such systems. In this description, the protein is expressed in the form of a spontaneous curvature field. The approaches include field theoretical methods limited to the small deformation regime, triangulated surfaces and particle-based computational models to investigate the large-deformation regimes observed in the natural state of many biological membranes. Applications of these methods to understand the properties of biological membranes in homogeneous and inhomogeneous environments of proteins, whose underlying curvature fields are either isotropic or anisotropic, are discussed. The diversity in the curvature fields elicits a rich variety of morphological states, including tubes, discs, branched tubes, and caveola. Mapping the thermodynamic stability of these states as a function of tuning parameters such as concentration and strength of curvature induction of the proteins is discussed. The relative stabilities of these self-organized shapes are examined through free-energy calculations. The suite of methods discussed here can be tailored to applications in specific cellular settings such as endocytosis during cargo trafficking and tubulation of filopodial structures in migrating cells, which makes these methods a powerful complement to experimental studies.
Collapse
Affiliation(s)
- N. Ramakrishnan
- Department of Chemical and Biomolecular Engineering, Department of Bioengineering, Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA-19104
| | - P. B. Sunil Kumar
- Department of Physics, Indian Institute of Technology Madras, Chennai, India - 600036
| | - Ravi Radhakrishnan
- Department of Chemical and Biomolecular Engineering, Department of Bioengineering, Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA-19104
| |
Collapse
|
19
|
Chong JYT, Mulet X, Postma A, Keddie DJ, Waddington LJ, Boyd BJ, Drummond CJ. Novel RAFT amphiphilic brush copolymer steric stabilisers for cubosomes: poly(octadecyl acrylate)-block-poly(polyethylene glycol methyl ether acrylate). SOFT MATTER 2014; 10:6666-6676. [PMID: 25058647 DOI: 10.1039/c4sm01064g] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Copolymers, particularly Pluronics®, are typically used to sterically stabilise colloidal nanostructured particles composed of a lyotropic liquid crystalline bicontinuous cubic phase (cubosomes). There is a need to design and assess new functionalisable stabilisers for these colloidal drug delivery systems. Six amphiphilic brush copolymers, poly(octadecyl acrylate)-block-poly(polyethylene glycol methyl ether acrylate) (P(ODA)-b-P(PEGA-OMe)), synthesised by reversible addition-fragmentation chain transfer (RAFT), were assessed as novel steric stabilisers for cubosomes. It was found that increasing the density of PEG on the nanostructured particle surface by incorporating a PEG brush design (i.e., brush copolymer), provided comparable and/or increased stabilisation effectiveness compared to a linear PEG structure, Pluronic® F127, which is extensively used for steric stabilisation of cubosomes. Assessment was conducted both prior to and following the removal of the dodecyl trithiocarbonate end-group, by free radical-induced reduction. The reduced (P(ODA)-b-P(PEGA-OMe) copolymers were more effective steric stabilisers for phytantriol and monoolein colloidal particle dispersions than their non-reduced analogues. High throughput characterisation methodologies, including an accelerated stability assay (ASA) and synchrotron small angle X-ray scattering (SAXS), were implemented in this study for the rapid assessment of steric stabiliser effectiveness and lyotropic liquid crystalline phase identification. Phytantriol cubosomes stabilised with P(ODA)-b-P(PEGA-OMe) copolymers exhibited a double diamond cubic phase (Q(2)(D)), whilst monoolein cubosomes exhibited a primitive cubic phase (Q(2)(P)), analogous to those formed using Pluronic® F127.
Collapse
Affiliation(s)
- Josephine Y T Chong
- CSIRO Materials Science and Engineering, Private Bag 10, Clayton, VIC 3169, Australia.
| | | | | | | | | | | | | |
Collapse
|
20
|
Kel O, Tamimi A, Fayer MD. The Influence of Cholesterol on Fast Dynamics Inside of Vesicle and Planar Phospholipid Bilayers Measured with 2D IR Spectroscopy. J Phys Chem B 2014; 119:8852-62. [DOI: 10.1021/jp503940k] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Oksana Kel
- Department
of Chemistry, Stanford University, Stanford, California 94305-5080, United States
| | - Amr Tamimi
- Department
of Chemistry, Stanford University, Stanford, California 94305-5080, United States
| | - Michael D. Fayer
- Department
of Chemistry, Stanford University, Stanford, California 94305-5080, United States
| |
Collapse
|
21
|
Smith EA, Smith C, Tanksley B, Dea PK. Effects of cis- and trans-unsaturated lipids on an interdigitated membrane. Biophys Chem 2014; 190-191:1-7. [DOI: 10.1016/j.bpc.2014.03.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 03/14/2014] [Accepted: 03/14/2014] [Indexed: 11/25/2022]
|
22
|
Maximo GJ, Costa MC, Coutinho JAP, Meirelles AJA. Trends and demands in the solid–liquid equilibrium of lipidic mixtures. RSC Adv 2014. [DOI: 10.1039/c4ra02715a] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The increasing importance of oil chemistry in industry and academic research demands a deeper understanding of solid–liquid equilibria of lipidic systems that is still far from complete.
Collapse
Affiliation(s)
- Guilherme J. Maximo
- Laboratory of Extraction
- Applied Thermodynamics and Equilibrium
- School of Food Engineering
- University of Campinas
- Campinas, Brazil
| | | | | | - Antonio J. A. Meirelles
- Laboratory of Extraction
- Applied Thermodynamics and Equilibrium
- School of Food Engineering
- University of Campinas
- Campinas, Brazil
| |
Collapse
|
23
|
Jahnke N, Krylova OO, Hoomann T, Vargas C, Fiedler S, Pohl P, Keller S. Real-time monitoring of membrane-protein reconstitution by isothermal titration calorimetry. Anal Chem 2013; 86:920-7. [PMID: 24354292 PMCID: PMC3886389 DOI: 10.1021/ac403723t] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
![]()
Phase diagrams offer a wealth of
thermodynamic information on aqueous
mixtures of bilayer-forming lipids and micelle-forming detergents,
providing a straightforward means of monitoring and adjusting the
supramolecular state of such systems. However, equilibrium phase diagrams
are of very limited use for the reconstitution of membrane proteins
because of the occurrence of irreversible, unproductive processes
such as aggregation and precipitation that compete with productive
reconstitution. Here, we exemplify this by dissecting the effects
of the K+ channel KcsA on the process of bilayer self-assembly
in a mixture of Escherichia coli polar lipid extract
and the nonionic detergent octyl-β-d-glucopyranoside.
Even at starting concentrations in the low micromolar range, KcsA
has a tremendous impact on the supramolecular organization of the
system, shifting the critical lipid/detergent ratios at the onset
and completion of vesicle formation by more than 2-fold. Thus, equilibrium
phase diagrams obtained for protein-free lipid/detergent mixtures
would be misleading when used to guide the reconstitution process.
To address this issue, we demonstrate that, even under such nonequilibrium
conditions, high-sensitivity isothermal titration calorimetry can
be exploited to monitor the progress of membrane-protein reconstitution
in real time, in a noninvasive manner, and at high resolution to yield
functional proteoliposomes with a narrow size distribution for further
downstream applications.
Collapse
Affiliation(s)
- Nadin Jahnke
- Molecular Biophysics, University of Kaiserslautern , Erwin-Schrödinger-Str. 13, 67663 Kaiserslautern, Germany
| | | | | | | | | | | | | |
Collapse
|
24
|
Abstract
We review recent computer simulation studies of undulating lipid bilayers. Theoretical interpretations of such fluctuating membranes are most commonly based on generalized Helfrich-type elastic models, with additional contributions of local "protrusions" and/or density fluctuations. Such models provide an excellent basis for describing the fluctuations of tensionless bilayers in the fluid Lαphase at a quantitative level.However, this description is found to fail for membranes in the gel phase and for membranes subject to high tensions. The fluctuations of tilted gel membranes (Lβ′phase) show a signature of the modulated ripple structure Pβ′, which is a nearby phase observed in the pretransition regime between the Lαand Lβ′state. This complicates a quantitative analysis on mesoscopic length scales. In the case of fluid membranes under tension, the large-wavelength fluctuation modes are found to be significantly softer than predicted by theory.In the latter context, we also address the general problem of the relation between frame tension and the fluctuation tension, which has been discussed somewhat controversially in recent years. Simulations of very simple model membranes with fixed area show that the fluctuations should be controlled by the frame tension, and not by the internal tension.
Collapse
Affiliation(s)
- FRIEDERIKE SCHMID
- Institute of Physics, Johannes-Gutenberg University of Mainz, D-55099 Mainz, Germany
| |
Collapse
|
25
|
Experimental Solid–Liquid Phase Equilibria of a Methyl Ester/Amide/Nitrile Ternary System by DSC. J AM OIL CHEM SOC 2013. [DOI: 10.1007/s11746-013-2320-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
26
|
Hanulová M, Weiss M. Membrane-mediated interactions – a physico-chemical basis for protein sorting. Mol Membr Biol 2012; 29:177-85. [DOI: 10.3109/09687688.2012.667838] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
|
27
|
Jones JW, Lue L, Saiani A, Tiddy GJT. Density, DSC, X-ray and NMR measurements through the gel and lamellar phase transitions of 1-myristoyl-2-stearoyl-sn-glycero-3-phosphatidylcholine (MSPC) and 1-stearoyl-2-myristoyl-sn-glycero-3-phosphatidylcholine (SMPC): observation of slow relaxation processes and mechanisms of phase transitions. Phys Chem Chem Phys 2012; 14:5452-69. [DOI: 10.1039/c2cp23136k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
28
|
Baik J, Rosania GR. Macrophages sequester clofazimine in an intracellular liquid crystal-like supramolecular organization. PLoS One 2012; 7:e47494. [PMID: 23071814 PMCID: PMC3469554 DOI: 10.1371/journal.pone.0047494] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Accepted: 09/17/2012] [Indexed: 12/30/2022] Open
Abstract
Clofazimine is a poorly-soluble but orally-bioavailable small molecule drug that massively accumulates in macrophages when administered over prolonged periods of time. To determine whether crystal-like drug inclusions (CLDIs) that form in subcellular spaces correspond to pure clofazimine crystals, macrophages of clofazimine-fed mice were elicited with an intraperitoneal thioglycollate injection. Inside these cells, CLDIs appeared uniform in size and shape, but were sensitive to illumination. Once removed from cells, CLDIs were unstable. Unlike pure clofazimine crystals, isolated CLDIs placed in distilled water burst into small birefringent globules, which aggregated into larger clusters. Also unlike pure clofazimine crystals, CLDIs fragmented when heated, and disintegrated in alkaline media. In contrast to all other organelles, CLDIs were relatively resistant to sonication and trypsin digestion, which facilitated their biochemical isolation. The powder x-ray diffraction pattern obtained from isolated CLDIs was consistent with the diffraction pattern of liquid crystals and inconsistent with the expected molecular diffraction pattern of solid, three dimensional crystals. Observed with the transmission electron microscope (TEM), CLDIs were bounded by an atypical double-layered membrane, approximately 20 nanometers thick. CLDIs were polymorphic, but generally exhibited an internal multilayered organization, comprised of stacks of membranes 5 to 15 nanometers thick. Deep-etch, freeze-fracture electron microscopy of unfixed snap-frozen tissue samples confirmed this supramolecular organization. These results suggest that clofazimine accumulates in macrophages by forming a membrane-bound, multilayered, liquid crystal-like, semi-synthetic cytoplasmic structure.
Collapse
Affiliation(s)
- Jason Baik
- Department of Pharmaceutical Sciences, University of Michigan College of Pharmacy, Ann Arbor, Michigan, United States of America
| | - Gus R. Rosania
- Department of Pharmaceutical Sciences, University of Michigan College of Pharmacy, Ann Arbor, Michigan, United States of America
- * E-mail:
| |
Collapse
|
29
|
Demé B, Zemb T. Hydration forces between bilayers in the presence of dissolved or surface-linked sugars. Curr Opin Colloid Interface Sci 2011. [DOI: 10.1016/j.cocis.2011.05.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
30
|
Henriques VB, Germano R, Lamy MT, Tamashiro MN. Phase transitions and spatially ordered counterion association in ionic-lipid membranes: theory versus experiment. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:13130-13143. [PMID: 21848301 DOI: 10.1021/la202302x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Aqueous dispersions of phosphatidylglycerol (PG) lipids may present an anomalous chain-melting transition at low ionic strengths, as seen by different experimental techniques such as calorimetry or light scattering. The anomaly disappears at high ionic strengths or for longer acyl-chain lengths. In this article, we use a statistical model for the bilayer that distinguishes both lipid chain and headgroup states in order to compare model and experimental thermotropic and electrical properties. The effective van der Waals interactions among hydrophobic chains compete with the electrostatic repulsions between polar headgroups, which may be ionized (counterion dissociated) or electrically neutral (associated with counterions). Electric degrees of freedom introduce new thermotropic charge-ordered phases in which headgroup charges may be spatially ordered, depending on the electrolyte ionic strength, introducing a new rationale for experimental data on PGs. The thermal phases presented by the model for different chain lengths, at fixed ionic strength, compare well with an experimental phase diagram constructed on the basis of differential scanning calorimetry profiles. In the case of dispersions of DMPG (dimyristoyl phosphatidylglycerol) with added monovalent salt, the model properties reproduce the main features displayed by data from differential scanning calorimetry as well as the characteristic profile for the degree of ionization of the bilayer surface across the anomalous transition region, obtained from the theoretical interpretation of electrokinetic (conductivity and electrophoretic mobility) measurements.
Collapse
Affiliation(s)
- V B Henriques
- Instituto de Física, Universidade de São Paulo, Caixa Postal 66318, 05314-970 São Paulo, SP, Brazil.
| | | | | | | |
Collapse
|
31
|
Schröder-Turk GE, Varslot T, de Campo L, Kapfer SC, Mickel W. A bicontinuous mesophase geometry with hexagonal symmetry. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:10475-10483. [PMID: 21728305 DOI: 10.1021/la201718a] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We report that a specific realization of Schwarz's triply periodic hexagonal minimal surface is isotropic with respect to the Doi-Ohta interface tensor and simultaneously has minimal packing and stretching frustration similar to those of the commonly found cubic bicontinuous mesophases. This hexagonal surface, of symmetry P6(3)/mmc with a lattice ratio of c/a = 0.832, is therefore a likely candidate geometry for self-assembled lipid/surfactant or copolymer mesophases. Furthermore, both the peak position ratios in its powder diffraction pattern and the elastic moduli closely resemble those of the cubic bicontinuous phases. We therefore argue that a genuine possibility of experimental misidentification exists.
Collapse
Affiliation(s)
- Gerd E Schröder-Turk
- Theoretische Physik, Friedrich-Alexander-Universität Erlangen-Nürnberg, D-91058 Erlangen, Germany.
| | | | | | | | | |
Collapse
|
32
|
Tamashiro MN, Barbetta C, Germano R, Henriques VB. Phase transitions and spatially ordered counterion association in ionic-lipid membranes: a statistical model. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 84:031909. [PMID: 22060405 DOI: 10.1103/physreve.84.031909] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Indexed: 05/31/2023]
Abstract
We propose a statistical model to account for the gel-fluid anomalous phase transitions in charged bilayer- or lamellae-forming ionic lipids. The model Hamiltonian comprises effective attractive interactions to describe neutral-lipid membranes as well as the effect of electrostatic repulsions of the discrete ionic charges on the lipid headgroups. The latter can be counterion dissociated (charged) or counterion associated (neutral), while the lipid acyl chains may be in gel (low-temperature or high-lateral-pressure) or fluid (high-temperature or low-lateral-pressure) states. The system is modeled as a lattice gas with two distinct particle types--each one associated, respectively, with the polar-headgroup and the acyl-chain states--which can be mapped onto an Ashkin-Teller model with the inclusion of cubic terms. The model displays a rich thermodynamic behavior in terms of the chemical potential of counterions (related to added salt concentration) and lateral pressure. In particular, we show the existence of semidissociated thermodynamic phases related to the onset of charge order in the system. This type of order stems from spatially ordered counterion association to the lipid headgroups, in which charged and neutral lipids alternate in a checkerboard-like order. Within the mean-field approximation, we predict that the acyl-chain order-disorder transition is discontinuous, with the first-order line ending at a critical point, as in the neutral case. Moreover, the charge order gives rise to continuous transitions, with the associated second-order lines joining the aforementioned first-order line at critical end points. We explore the thermodynamic behavior of some physical quantities, like the specific heat at constant lateral pressure and the degree of ionization, associated with the fraction of charged lipid headgroups.
Collapse
Affiliation(s)
- M N Tamashiro
- Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, 13083-970, Campinas, SP, Brazil.
| | | | | | | |
Collapse
|
33
|
Chiu MH, Prenner EJ. Differential scanning calorimetry: An invaluable tool for a detailed thermodynamic characterization of macromolecules and their interactions. J Pharm Bioallied Sci 2011; 3:39-59. [PMID: 21430954 PMCID: PMC3053520 DOI: 10.4103/0975-7406.76463] [Citation(s) in RCA: 190] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2010] [Revised: 10/05/2010] [Accepted: 10/19/2010] [Indexed: 11/04/2022] Open
Abstract
Differential Scanning Calorimetry (DSC) is a highly sensitive technique to study the thermotropic properties of many different biological macromolecules and extracts. Since its early development, DSC has been applied to the pharmaceutical field with excipient studies and DNA drugs. In recent times, more attention has been applied to lipid-based drug delivery systems and drug interactions with biomimetic membranes. Highly reproducible phase transitions have been used to determine values, such as, the type of binding interaction, purity, stability, and release from a drug delivery mechanism. This review focuses on the use of DSC for biochemical and pharmaceutical applications.
Collapse
Affiliation(s)
- Michael H Chiu
- Department of Biological Sciences, University of Calgary, T2N 1N4 Calgary, AB, Canada
| | | |
Collapse
|
34
|
Wang L, MacDonald RC. Cationic phospholiposomes: efficient delivery vehicles of anticancer derivatives of ATP to multiple myeloma cells. J Liposome Res 2011; 21:306-14. [PMID: 21457078 DOI: 10.3109/08982104.2011.565476] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Analogs of adenosine triphosphate (ATP) with substitutions at the 8-position have been shown to be cytotoxic to multiple myeloma, one of the most prevalent and serious blood cancers. However, these drugs do not readily cross biological membranes and are very sensitive to phosphatases present in body fluids. To circumvent these disadvantages, 8-substituted ATPs were encapsulated into cationic phospholiposomes generated from cationic phosphatidylcholines (EDOPC; 1,2-dioleoyl-sn-glycero-3-ethylphosphocholine, and EDPPC, the corresponding dipalmitoyl homolog), compounds with low toxicity that readily form liposomes. Vortexing was an efficient encapsulation procedure, more so than freeze-thawing. At the lipid:drug ratio of 5:1 (mol/mol), 20% of 8-Br-ATP was encapsulated within EDOPC liposomes. Efficient encapsulation and retention of 8-NH₂-ATP required the inclusion of cholesterol. Liposomes of EDOPC:cholesterol (55:45 mole/mole), at a lipid:drug mole ratio of 10:1, captured ~40% of the drug presented. Cytotoxicity assays of this formulation on multiple myeloma cells in culture showed encapsulated drug to be up to 10-fold more effective than free drug, depending upon dose. Intracellular distribution studies (based on fluorescent derivatives of lipids and of ATP) revealed that both liposomes and drug were taken up by multiple myeloma cells, and that uptake of a fluorescent ATP derivative was significantly greater when encapsulated than when free. Liposomes prepared from EDPPC, having a higher phase-transition temperature than EDOPC, captured 8-NH₂-ATP satisfactorily and released it more slowly than the unsaturated formulations, but were also less cytotoxic. The superior encapsulation efficiencies of the positively charged liposomes can be understood in terms of the electrostatic double layer due to a very high positive charge density on their inner surface. Electrostatic augmentation of encapsulation for small vesicles can be dramatic, easily exceeding an order of magnitude.
Collapse
Affiliation(s)
- Li Wang
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois 60208, USA
| | | |
Collapse
|
35
|
A hydrogen peroxide biosensor based on the direct electron transfer of hemoglobin encapsulated in liquid-crystalline cubic phase on electrode. Colloids Surf B Biointerfaces 2011; 82:359-64. [DOI: 10.1016/j.colsurfb.2010.09.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2010] [Revised: 09/04/2010] [Accepted: 09/07/2010] [Indexed: 11/18/2022]
|
36
|
Brooks NJ, Ces O, Templer RH, Seddon JM. Pressure effects on lipid membrane structure and dynamics. Chem Phys Lipids 2010; 164:89-98. [PMID: 21172328 DOI: 10.1016/j.chemphyslip.2010.12.002] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Revised: 12/07/2010] [Accepted: 12/09/2010] [Indexed: 11/30/2022]
Abstract
The effect of hydrostatic pressure on lipid structure and dynamics is highly important as a tool in biophysics and bio-technology, and in the biology of deep sea organisms. Despite its importance, high hydrostatic pressure remains significantly less utilised than other thermodynamic variables such as temperature and chemical composition. Here, we give an overview of some of the theoretical aspects which determine lipid behaviour under pressure and the techniques and technology available to study these effects. We also summarise several recent experiments which highlight the information available from these approaches.
Collapse
Affiliation(s)
- Nicholas J Brooks
- Membrane Biophysics Platform and Institute of Chemical Biology, Department of Chemistry, Imperial College London, South Kensington Campus, UK
| | | | | | | |
Collapse
|
37
|
Yarrow F, Kennedy E, Salaun F, Rice JH. Sub-wavelength infrared imaging of lipids. BIOMEDICAL OPTICS EXPRESS 2010; 2:37-43. [PMID: 21326633 PMCID: PMC3028496 DOI: 10.1364/boe.2.000037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2010] [Revised: 11/30/2010] [Accepted: 11/30/2010] [Indexed: 05/21/2023]
Abstract
Infrared absorption spectroscopy of lipid layers was performed by combining optics and scanning probe microscopy. This experimental approach enables sub-diffraction IR imaging with a spatial resolution on the nanometer scale of 1, 2-dioleoyl-sn-glycero-3-phosphocholine lipid layers.
Collapse
Affiliation(s)
- Fiona Yarrow
- NanoPhotonics Research Group, School of Physics, University College Dublin, Belfield, Dublin, Ireland
| | | | | | | |
Collapse
|
38
|
Stark B, Pabst G, Prassl R. Long-term stability of sterically stabilized liposomes by freezing and freeze-drying: Effects of cryoprotectants on structure. Eur J Pharm Sci 2010; 41:546-55. [DOI: 10.1016/j.ejps.2010.08.010] [Citation(s) in RCA: 143] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Revised: 07/26/2010] [Accepted: 08/19/2010] [Indexed: 11/29/2022]
|
39
|
Yarrow F, Kuipers BWM. AFM study of the thermotropic behaviour of supported DPPC bilayers with and without the model peptide WALP23. Chem Phys Lipids 2010; 164:9-15. [PMID: 20932964 DOI: 10.1016/j.chemphyslip.2010.09.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2010] [Revised: 09/02/2010] [Accepted: 09/27/2010] [Indexed: 10/19/2022]
Abstract
Temperature-controlled Atomic Force Microscopy (TC-AFM) in Contact Mode is used here to directly image the mechanisms by which melting and crystallization of supported, hydrated DPPC bilayers proceed in the presence and absence of the model peptide WALP23. Melting from the gel L(β)' to the liquid-crystalline L(α) phase starts at pre-existing line-type packing defects (grain boundaries) in absence of the peptide. The exact transition temperature is shown to be influenced by the magnitude of the force exerted by the AFM probe on the bilayer, but is higher than the main transition temperature of non-supported DPPC vesicles in all cases due to bilayer-substrate interactions. Cooling of the fluid L(α) bilayer shows the formation of the line-type defects at the borders between different gel-phase regions that originate from different nuclei. The number of these defects depends directly on the rate of cooling through the transition, as predicted by classical nucleation theory. The presence of the transmembrane, synthetic model peptide WALP23 is known to give rise to heterogeneity in the bilayer as microdomains with a striped appearance are formed in the DPPC bilayer. This striated phase consists of alternating lines of lipids and peptide. It is shown here that melting starts with the peptide-associated lipids in the domains, whose melting temperature is lowered by 0.8-2.0°C compared to the remaining, peptide-free parts of the bilayer. The stabilization of the fluid phase is ascribed to adaptations of the lipids to the shorter peptide. The lipids not associated with the peptide melt at the same temperature as those in the pure DPPC supported bilayer.
Collapse
Affiliation(s)
- F Yarrow
- Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science, Science Faculty, Utrecht University, P.O. Box 80000, 3508 TA, Utrecht, The Netherlands.
| | | |
Collapse
|
40
|
Novales B, Riaublanc A, Navailles L, Houssou BH, Gaillard C, Nallet F, Douliez JP. Self-assembly and foaming properties of fatty acid-lysine aqueous dispersions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:5329-5334. [PMID: 20334439 DOI: 10.1021/la9034613] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We report on dispersions of fatty acid-lysine salts in aqueous solutions which are further used to produce foams. The alkyl chain length is varied from dodecyl to stearic. In aqueous solutions, the lysine salt of the dodecyl chain yields an isotropic solution, probably micelles, whereas for longer alkyl chains, vesicles formed but crystallized upon resting at room temperature or when kept at 4 degrees C. Solid-state NMR showed that in vesicles fatty acids are embedded in a lamellar arrangement passing from a gel to a fluid state upon heating; the transition temperature at which it occurs was determined by DSC. Those results are confirmed by small-angle neutron scattering which also give additional information on the bilayer structure. Incredibly stable foams are obtained using the palmitic acid/Lys salt whereas for other alkyl chain length, poor or no foam is formed. We conclude that the foamability is related to the phase behavior in aqueous solution.
Collapse
Affiliation(s)
- Bruno Novales
- UR1268 Biopolymères Interactions Assemblages, INRA, équipe Interfaces et Systèmes Dispersés, F-44316 Nantes, France
| | | | | | | | | | | | | |
Collapse
|
41
|
Jia Y, Joly H, Leek DM, Demetzos C, Omri A. The effect of aminoglycoside antibiotics on the thermodynamic properties of liposomal vesicles. J Liposome Res 2010; 20:84-96. [DOI: 10.3109/08982100903103896] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
|
42
|
Chemistry and Function of Phospholipids. FOOD SCIENCE AND TECHNOLOGY 2010. [DOI: 10.1201/9781420046649.ch2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
|
43
|
Smith EA, van Gorkum CM, Dea PK. Properties of phosphatidylcholine in the presence of its monofluorinated analogue. Biophys Chem 2009; 147:20-7. [PMID: 20064684 DOI: 10.1016/j.bpc.2009.12.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2009] [Revised: 12/15/2009] [Accepted: 12/15/2009] [Indexed: 10/20/2022]
Abstract
In aqueous solution, the monofluorinated phospholipid 1-palmitoyl-2-[16-fluoropalmitoyl]sn-glycero-3-phosphocholine (F-DPPC) interdigitates without the use of inducing agents. To understand the thermal and physical properties of this unique lipid, F-DPPC was combined with the non-fluorinated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), and 1,2-diarachidoyl-sn-glycero-3-phosphocholine (DAPC). Differential scanning calorimetry (DSC) was used to determine the miscibility and thermotropic phase behavior of these binary lipid mixtures. In addition, the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH) and a DPH-labeled analogue of DPPC, 2-(3-(diphenylhexatrienyl) propanoyl)-1-hexadecanoyl-sn-glycero-3-phosphocholine (beta-DPH HPC, aka DPH-PC or DPHpPC), were used to detect interdigitation. In F-DPPC, the fluorescence intensity of both probes decreased a similar amount and to a degree that is consistent with an interdigitated system. We also determined that there are two separate effects of increasing the ratio of F-DPPC in the DPPC/F-DPPC system. With low amounts of F-DPPC, there is little evidence that the system is heavily interdigitated. Instead, we hypothesize that the introduction of F-DPPC provides nucleation sites that alter the kinetics, reversibility, and temperature of the main transition (T(m)). At higher mol% of F-DPPC, we propose that interdigitated F-DPPC-rich domains form to create a phase-segregated system. While DPPC/F-DPPC was highly miscible, the DAPC/F-DPPC system was significantly less miscible. Additionally, we observed that DAPC/F-DPPC samples have reduced solubility in water, which affected the acquisition of fluorescence data. However, our DSC results indicate the existence of DAPC-rich and F-DPPC-rich components. Furthermore, this data support that the mixing was disruptive to lipid packing and that the presence of DAPC hinders the interdigitation of F-DPPC.
Collapse
Affiliation(s)
- Eric A Smith
- Department of Chemistry, Occidental College, 1600 Campus Road, Los Angeles, CA 90041, USA
| | | | | |
Collapse
|
44
|
Mishra PR, Gupta GK, Jain V. Stearic Acid and Glyceryl Monostearate Based Self-Assembled Vesicles: Preparation and In vitro Evaluation. J DISPER SCI TECHNOL 2009. [DOI: 10.1080/01932690903120128] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
|
45
|
Douliez JP, Novales B, Gaillard C. Synthesising gold nanoparticles within bola fatty acid nanosomes. J Colloid Interface Sci 2009; 337:610-3. [DOI: 10.1016/j.jcis.2009.05.042] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Revised: 05/11/2009] [Accepted: 05/20/2009] [Indexed: 10/20/2022]
|
46
|
Dunphy DR, Alam TM, Tate MP, Hillhouse HW, Smarsly B, Collord AD, Carnes E, Baca HK, Köhn R, Sprung M, Wang J, Brinker CJ. Characterization of lipid-templated silica and hybrid thin film mesophases by grazing incidence small-angle X-ray scattering. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:9500-9. [PMID: 19496546 PMCID: PMC2736351 DOI: 10.1021/la900748r] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The nanostructure of silica and hybrid thin film mesophases templated by phospholipids via an evaporation-induced self-assembly (EISA) process was investigated by grazing-incidence small-angle X-ray scattering (GISAXS). Diacyl phosphatidylcholines with two tails of 6 or 8 carbons were found to template 2D hexagonal mesophases, with the removal of lipid from these lipid/silica films by thermal or UV/O3 processing resulting in a complete collapse of the pore volume. Monoacyl phosphatidylcholines with single tails of 10-14 carbons formed 3D micellular mesophases; the lipid was found to be extractable from these 3D materials, yielding a porous material. In contrast to pure lipid/silica thin film mesophases, films formed from the hybrid bridged silsesquioxane precursor bis(triethoxysilyl)ethane exhibited greater stability toward (both diacyl and monoacyl) lipid removal. Ellipsometric, FTIR, and NMR studies show that the presence of phospholipid suppresses siloxane network formation, while actually promoting condensation reactions in the hybrid material. 1D X-ray scattering and FTIR data were found to be consistent with strong interactions between lipid headgroups and the silica framework.
Collapse
Affiliation(s)
- Darren R. Dunphy
- University of New Mexico/NSF Center for Micro-Engineered Materials, Department of Chemical and Nuclear Engineering, Albuquerque, New Mexico 87131
| | - Todd M. Alam
- Department of Electronic and Nanostructured Materials, Sandia National Laboratories, Albuquerque, New Mexico 87185
| | - Michael P. Tate
- School of Chemical Engineering, Purdue University, 480 Stadium Mall Drive, West Lafayette, Indiana 47907
| | - Hugh W. Hillhouse
- School of Chemical Engineering, Purdue University, 480 Stadium Mall Drive, West Lafayette, Indiana 47907
| | - Bernd Smarsly
- Physikalisch-Chemisches Institut, Justus-Liebig-University Giessen, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany
| | - Andrew D. Collord
- University of New Mexico/NSF Center for Micro-Engineered Materials, Department of Chemical and Nuclear Engineering, Albuquerque, New Mexico 87131
| | - Eric Carnes
- University of New Mexico/NSF Center for Micro-Engineered Materials, Department of Chemical and Nuclear Engineering, Albuquerque, New Mexico 87131
| | - Helen K. Baca
- University of New Mexico/NSF Center for Micro-Engineered Materials, Department of Chemical and Nuclear Engineering, Albuquerque, New Mexico 87131
| | - Ralf Köhn
- University of New Mexico/NSF Center for Micro-Engineered Materials, Department of Chemical and Nuclear Engineering, Albuquerque, New Mexico 87131
- Department of Chemistry & Biochemistry, University of Munich, Butenandtstr. 5-13 (E), 81377 Munich, Germany
| | - Michael Sprung
- Advanced Photon Source, Argonne National Laboratory, 9700 S Cass Avenue, Argonne, Illinois 60439
| | - Jin Wang
- Advanced Photon Source, Argonne National Laboratory, 9700 S Cass Avenue, Argonne, Illinois 60439
| | - C. Jeffrey Brinker
- University of New Mexico/NSF Center for Micro-Engineered Materials, Department of Chemical and Nuclear Engineering, Albuquerque, New Mexico 87131
- Advanced Materials Laboratory, Sandia National Laboratories, Albuquerque, New Mexico 87185
- To whom correspondence should be addressed.
| |
Collapse
|
47
|
Boodhoo MV, Bouzidi L, Narine SS. The binary phase behavior of 1, 3-dipalmitoyl-2-stearoyl-sn-glycerol and 1, 2-dipalmitoyl-3-stearoyl-sn-glycerol. Chem Phys Lipids 2009; 160:11-32. [PMID: 19501207 DOI: 10.1016/j.chemphyslip.2009.02.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2009] [Revised: 02/16/2009] [Accepted: 02/17/2009] [Indexed: 11/29/2022]
Abstract
The binary phase behavior of purified 1, 3-dipalmitoyl-2-stearoyl-sn-glycerol (PSP) and 1, 2-dipalmitoyl-3-stearoyl-sn-glycerol (PPS) was investigated at a very slow (0.1 degrees C/min) and a relatively fast (3.0 degrees C/min) cooling rate. Mixtures with molar fractions of 0.1 increments were studied in terms of melting and crystallization, polymorphism, solid fat content (SFC), hardness and microstructure. Only the alpha-form of a double chain length (DCL) structure was detected for all mixtures in both experiments. The kinetic phase diagram, constructed using heating DSC thermograms, displayed two distinct behaviors separated by a singularity at the 0.5(PSP) composition: a eutectic in the X(PSP)< or =0.5 and a monotectic in the X(PSP)< or =0.5 concentration region. The singularity was attributed to the formation of a 1:1 (mol:mol) molecular compound. Apart from the segment from 0.0(PSP) to the eutectic point, X(E), the simulation of the liquidus line using a model based on the Hildebrand equation suggested that the molecular interactions are strong and tend to favor the formation of unlike pairs in the liquid state and that the miscibility is not significantly dependent on cooling rate. The kinetic effects are manifest in all measured properties, particularly dramatically in the X(PSP)< or =X(E) concentration region. An analysis of induction time as measured by pulse nuclear magnetic resonance (pNMR) showed that PPS retards crystal growth, an effect which can explain the peculiarity of this concentration region. At both cooling rates, fit of the SFC (%) versus time curves to a modified form of the Avrami model revealed two common growth modes for all the mixtures. The polarized light microscope (PLM) of the PSP-PPS mixtures revealed networks made of spherulitic crystallites of size, growth direction and boundaries that are varied and sensitive to composition and cooling rate. The change in the microstructure and final SFC (%), particularly noticeable at compositions close to the eutectic, explain in part the differences seen in relative hardness.
Collapse
Affiliation(s)
- M V Boodhoo
- Department of Agricultural Food and Nutritional Science, University of Alberta, Edmonton, Canada
| | | | | |
Collapse
|
48
|
The binary phase behavior of 1,3-dicaproyl-2-stearoyl-sn-glycerol and 1,2-dicaproyl-3-stearoyl-sn-glycerol. Chem Phys Lipids 2009; 157:21-39. [DOI: 10.1016/j.chemphyslip.2008.08.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2008] [Revised: 08/21/2008] [Accepted: 08/26/2008] [Indexed: 11/17/2022]
|
49
|
Davis JR, Panagiotopoulos AZ. Monte Carlo simulations of amphiphilic nanoparticle self-assembly. J Chem Phys 2008; 129:194706. [DOI: 10.1063/1.3009183] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
|
50
|
Bothun GD. Hydrophobic silver nanoparticles trapped in lipid bilayers: Size distribution, bilayer phase behavior, and optical properties. J Nanobiotechnology 2008; 6:13. [PMID: 19014492 PMCID: PMC2596172 DOI: 10.1186/1477-3155-6-13] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2008] [Accepted: 11/12/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Lipid-based dispersion of nanoparticles provides a biologically inspired route to designing therapeutic agents and a means of reducing nanoparticle toxicity. Little is currently known on how the presence of nanoparticles influences lipid vesicle stability and bilayer phase behavior. In this work, the formation of aqueous lipid/nanoparticle assemblies (LNAs) consisting of hydrophobic silver-decanethiol particles (5.7 +/- 1.8 nm) embedded within 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayers is demonstrated as a function of the DPPC/Ag nanoparticle (AgNP) ratio. The effect of nanoparticle loading on the size distribution, bilayer phase behavior, and bilayer fluidity is determined. Concomitantly, the effect of bilayer incorporation on the optical properties of the AgNPs is also examined. RESULTS The dispersions were stable at 50 degrees C where the bilayers existed in a liquid crystalline state, but phase separated at 25 degrees C where the bilayers were in a gel state, consistent with vesicle aggregation below the lipid melting temperature. Formation of bilayer-embedded nanoparticles was confirmed by differential scanning calorimetry and fluorescence anisotropy, where increasing nanoparticle concentration suppressed the lipid pretransition temperature, reduced the melting temperature, and disrupted gel phase bilayers. The characteristic surface plasmon resonance (SPR) wavelength of the embedded nanoparticles was independent of the bilayer phase; however, the SPR absorbance was dependent on vesicle aggregation. CONCLUSION These results suggest that lipid bilayers can distort to accommodate large hydrophobic nanoparticles, relative to the thickness of the bilayer, and may provide insight into nanoparticle/biomembrane interactions and the design of multifunctional liposomal carriers.
Collapse
Affiliation(s)
- Geoffrey D Bothun
- Department of Chemical Engineering, University of Rhode Island, Kingston, RI, 02881, USA.
| |
Collapse
|