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Risse K, Drusch S. (Non)linear Interfacial Rheology of Tween, Brij and Span Stabilized Oil-Water Interfaces: Impact of the Molecular Structure of the Surfactant on the Interfacial Layer Stability. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40. [PMID: 39126646 PMCID: PMC11363120 DOI: 10.1021/acs.langmuir.4c02210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2024] [Revised: 08/05/2024] [Accepted: 08/05/2024] [Indexed: 08/12/2024]
Abstract
During emulsification and further processing (e.g., pasteurizing), the oil-water interface is mechanically and thermally stressed, which can lead to oil droplet aggregation and coalescence, depending on the interfacial properties. Currently, there is a lack of insights into the impact of the molecular structure (headgroup and FA chain) of low molecular weight emulsifiers (LME) on the resulting interfacial properties. Additionally, the crystallization/melting of the oil/the emulsifier is often neglected within interfacial rheological experiments. Within this study, the stability of interfaces formed by Tween, Span or Brij was determined as a function of their molecular structure, taking crystallization effects of the LME into account. The headgroup was kept constant while varying the FA, or vice versa. The interfacial film properties (viscoelasticity) were investigated at different temperatures using dilatational and interfacial shear rheology. Both the headgroup and the FA chain impacted the interfacial properties. For the same FA composition, a rather small hydrophobic headgroup resulted in a higher packed interface. The interfacial elasticity increased with increased FA chain length (C12 to C18). This seemed to be particularly the case when the emulsifier crystallized on the interface among cooling. In the case of a densely packed interface, network formation due to chain crystallization of the LME's FA chains occurs during the cooling step. The resulting interface shows predominantly elastic behavior.
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Affiliation(s)
- Kerstin Risse
- Technische Universität
Berlin, Faculty III Process
Sciences, Institute of Food Technology and Food Chemistry, Department
of Food Technology and Food Material Science, Straße des 17. Juni 135, 10623 Berlin, Germany
| | - Stephan Drusch
- Technische Universität
Berlin, Faculty III Process
Sciences, Institute of Food Technology and Food Chemistry, Department
of Food Technology and Food Material Science, Straße des 17. Juni 135, 10623 Berlin, Germany
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2
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Akos Z, Isai DG, Rajasingh S, Kosa E, Ghazvini S, Dhar P, Czirok A. Viscoelastic Properties of ECM-Rich Embryonic Microenvironments. Front Cell Dev Biol 2020; 8:674. [PMID: 32984301 PMCID: PMC7487363 DOI: 10.3389/fcell.2020.00674] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2019] [Accepted: 07/02/2020] [Indexed: 11/13/2022] Open
Abstract
The material properties of tissues and their mechanical state is an important factor in development, disease, regenerative medicine and tissue engineering. Here we describe a microrheological measurement technique utilizing aggregates of microinjected ferromagnetic nickel particles to probe the viscoelastic properties of embryonic tissues. Quail embryos were cultured in a plastic incubator chamber located at the center of two pairs of crossed electromagnets. We found a pronounced viscoelastic behavior within the ECM-rich region separating the mesoderm and endoderm in Hamburger Hamilton stage 10 quail embryos, consistent with a Zener (standard generalized solid) model. The viscoelastic response is about 45% of the total response, with a characteristic relaxation time of 1.3 s.
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Affiliation(s)
- Zsuzsa Akos
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, United States
| | - Dona Greta Isai
- Department of Anatomy & Cell Biology, University of Kansas Medical Center, Kansas City, KS, United States
| | - Sheeja Rajasingh
- Department of Bioscience Research, University of Tennessee Health Science Center, Memphis, TN, United States
| | - Edina Kosa
- Department of Research, Kansas City University of Medicine and Biosciences, Kansas City, MO, United States
| | - Saba Ghazvini
- Chemical & Petroleum Engineering, The University of Kansas, Lawrence, KS, United States
| | - Prajnaparamita Dhar
- Chemical & Petroleum Engineering, The University of Kansas, Lawrence, KS, United States
| | - Andras Czirok
- Department of Anatomy & Cell Biology, University of Kansas Medical Center, Kansas City, KS, United States.,Department of Biological Physics, Eotvos University, Budapest, Hungary
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3
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Barman S, Davidson ML, Walker LM, Anna SL, Zasadzinski JA. Inflammation product effects on dilatational mechanics can trigger the Laplace instability and acute respiratory distress syndrome. SOFT MATTER 2020; 16:6890-6901. [PMID: 32643749 PMCID: PMC7462632 DOI: 10.1039/d0sm00415d] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
In the lungs, the Laplace pressure, ΔP = 2γ/R, would be higher in smaller alveoli than larger alveoli unless the surface tension, γ decreases with alveolar interfacial area, A, such that 2ε > γ in which ε = A(dγ/dA) is the dilatational modulus. In Acute Respiratory Distress Syndrome (ARDS), lipase activity due to the immune response to an underlying trauma or disease causes single chain lysolipid concentrations to increase in the alveolar fluids via hydrolysis of double-chain phospholpids in bacterial, viral, and normal cell membranes. Increasing lysolipid concentrations decrease the dilatational modulus dramatically at breathing frequencies if the soluble lysolipid has sufficient time to diffuse off the interface, causing 2ε < γ, thereby potentially inducing the "Laplace Instability", in which larger alveoli have a lower internal pressure than smaller alveoli. This can lead to uneven lung inflation, alveolar flooding, and poor gas exchange, typical symptoms of ARDS. While the ARDS lung contains a number of lipid and protein species in the alveolar fluid in addition to lysolipids, the surface activity and frequency dependent dilatational modulus of lysolipid suggest how inflammation may lead to the lung instabilities associated with ARDS. At high frequencies, even at high lysolipid concentrations, 2ε - γ > 0, which may explain the benefits ARDS patients receive from high frequency oscillatory ventilation.
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Affiliation(s)
- Sourav Barman
- Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota, USA
| | - Michael L Davidson
- Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA
| | - Lynn M Walker
- Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA
| | - Shelly L Anna
- Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA
| | - Joseph A Zasadzinski
- Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota, USA
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4
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Skrzypiec M, Weiss M, Dopierała K, Prochaska K. Langmuir-Blodgett films of membrane lipid in the presence of hybrid silsesquioxane, a promising component of biomaterials. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2019; 105:110090. [PMID: 31546436 DOI: 10.1016/j.msec.2019.110090] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 08/01/2019] [Accepted: 08/14/2019] [Indexed: 12/11/2022]
Abstract
Functionalized polyhedral oligomeric silsesquioxanes (POSS) derivatives have great potential in biomedical applications such as tissue engineering, drug delivery, biosensors, dental composites and biomedical devices. Having the above in mind, in this paper, the study of the surface characteristics of binary Langmuir-Blodgett films consisting of an open cage silsesquioxane POSS-poly (ethylene glycol) (POSS-PEG) and 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine (DMPE), as a representative of phospholipid was conducted based on contact angle measurements of three liquids. The measured values of the contact angle (with water, formamide and diiodomethane as the wetting liquids) allowed to calculate surface free energy of the films from van Oss et al. approach. The film structure of the deposited layers was evaluated using an atomic force microscope. Analysis of the obtained results led to the conclusion, that the pure DMPE molecules create agglomerates onto a solid substrate, whereas the POSS-PEG molecules form a homogenous monolayer. After an addition of POSS-PEG to lipid film, changes in the surface properties are visible. The wettability as well as surface free energy depend on the molar ratio of both components. The AFM images shed more light on the changes of the DMPE monolayer topography caused by the POSS-PEG addition.
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Affiliation(s)
- Marta Skrzypiec
- Institute of Chemical Technology and Engineering, Poznan University of Technology, Berdychowo 4, 60-965 Poznań, Poland
| | - Marek Weiss
- Institute of Physics, Poznan University of Technology, Piotrowo 3, 60-965 Poznań, Poland
| | - Katarzyna Dopierała
- Institute of Chemical Technology and Engineering, Poznan University of Technology, Berdychowo 4, 60-965 Poznań, Poland
| | - Krystyna Prochaska
- Institute of Chemical Technology and Engineering, Poznan University of Technology, Berdychowo 4, 60-965 Poznań, Poland.
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5
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Hatta E, Nihei K. Emergence of a linear slope region of the isotherm in the first-order liquid-expanded-liquid-condensed phase transition in Langmuir monolayers. Phys Rev E 2019; 100:022801. [PMID: 31574626 DOI: 10.1103/physreve.100.022801] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Indexed: 06/10/2023]
Abstract
A nonhorizontal slope in the isotherm has been observed in the two-phase coexisting region of the first-order liquid-expanded (LE)-liquid-condensed (LC) phase transition in Langmuir monolayers for many decades. We show that the simple analysis of a phenomenological Landau free energy involving the coupling-energy contributions of molecular lateral density (ρ) with spontaneous collective chain tilt (θ) and two-dimensional strain (ɛ_{s}) inside the LC domain enables one to understand the origin of a nonhorizontal straight-line slope in the LE-LC phase coexistence region of the isotherm. The presence of ρ-ɛ_{s} coupling must be essential for the appearance of the straight-line shape of a nonhorizontal plateau in the isotherm. Moreover, it is found from the comparison of the two-dimensional contour plots of the free energy that an LE phase may persist significantly even at the later stage of the straight-line regime beyond a transition midpoint surface pressure in the presence of this coupling. The persistence of the LE phase may lead to the delay of transition progress as manifested more clearly by the appearance of a compressibility plateau in the coexistence region that indicates the existence of persistent equilibrium density fluctuations in the monolayer.
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Affiliation(s)
- Eiji Hatta
- Nanoelectronics Laboratory, Graduate School of Information Science and Technology, Hokkaido University, Sapporo, 060-0814, Japan
| | - Ko Nihei
- Nanoelectronics Laboratory, Graduate School of Information Science and Technology, Hokkaido University, Sapporo, 060-0814, Japan
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Detailed characterization of POSS-poly(ethylene glycol) interaction with model phospholipid membrane at the air/water interface. Colloids Surf B Biointerfaces 2018; 171:167-175. [DOI: 10.1016/j.colsurfb.2018.07.029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 06/23/2018] [Accepted: 07/13/2018] [Indexed: 12/11/2022]
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7
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Guzmán E, Tajuelo J, Pastor JM, Rubio MÁ, Ortega F, Rubio RG. Shear rheology of fluid interfaces: Closing the gap between macro- and micro-rheology. Curr Opin Colloid Interface Sci 2018. [DOI: 10.1016/j.cocis.2018.05.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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8
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Piskorz J, Mlynarczyk DT, Szczolko W, Konopka K, Düzgüneş N, Mielcarek J. Liposomal formulations of magnesium sulfanyl tribenzoporphyrazines for the photodynamic therapy of cancer. J Inorg Biochem 2018; 184:34-41. [PMID: 29679798 DOI: 10.1016/j.jinorgbio.2018.04.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 03/22/2018] [Accepted: 04/08/2018] [Indexed: 12/12/2022]
Abstract
Photodynamic therapy of cancer comprises the activation of photosensitizer molecules delivered to cancer cells, to generate reactive oxygen species that mediate cytotoxicity. In this study, previously synthesized dendritic magnesium tribenzoporphyrazines were incorporated into four types of liposomes containing either 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) or 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) as the zwitterionic lipids. The addition of either l-α-phosphatidyl-dl-glycerol (PG) or 1,2-dioleoyl-3-trimethylammoniumpropane (DOTAP) imparted a negative or positive charge, respectively. Novel formulations were tested in oral squamous cell carcinoma cell lines (CAL 27, HSC-3) as well as cervical adenocarcinoma cells (HeLa). Positively charged DOTAP:POPC liposomes were the most effective carriers for all tested tribenzoporphyrazines. Calculated IC50 values for DOTAP:POPC liposomes indicated that the incorporation of tribenzoporphyrazines into these liposomes can improve photocytotoxicity up to 50-fold compared to the free forms of macrocycles. Oral cancer cells (CAL 27 and HSC-3) were more sensitive to liposomal photodynamic treatment than HeLa cells.
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Affiliation(s)
- Jaroslaw Piskorz
- Department of Inorganic and Analytical Chemistry, Poznan University of Medical Sciences, Grunwaldzka 6, 60-780 Poznan, Poland.
| | - Dariusz T Mlynarczyk
- Department of Chemical Technology of Drugs, Poznan University of Medical Sciences, Grunwaldzka 6, 60-780 Poznan, Poland
| | - Wojciech Szczolko
- Department of Chemical Technology of Drugs, Poznan University of Medical Sciences, Grunwaldzka 6, 60-780 Poznan, Poland
| | - Krystyna Konopka
- Department of Biomedical Sciences, University of the Pacific, 155 Fifth Street, San Francisco, CA 94103, USA
| | - Nejat Düzgüneş
- Department of Biomedical Sciences, University of the Pacific, 155 Fifth Street, San Francisco, CA 94103, USA
| | - Jadwiga Mielcarek
- Department of Inorganic and Analytical Chemistry, Poznan University of Medical Sciences, Grunwaldzka 6, 60-780 Poznan, Poland
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9
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Bykov A, Loglio G, Ravera F, Liggieri L, Miller R, Noskov B. Dilational surface elasticity of spread monolayers of pulmonary lipids in a broad range of surface pressure. Colloids Surf A Physicochem Eng Asp 2018. [DOI: 10.1016/j.colsurfa.2018.01.031] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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10
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Ghazvini S, Alonso R, Alhakamy N, Dhar P. pH-Induced Changes in the Surface Viscosity of Unsaturated Phospholipids Monitored Using Active Interfacial Microrheology. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:1159-1170. [PMID: 29019691 DOI: 10.1021/acs.langmuir.7b02803] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Lipid membranes, a major component of cells, are subjected to significant changes in pH depending on their location in the cell: the outer leaflet of the cell membrane is exposed to a pH of 7.4 whereas lipid membranes that make up late endosomes and lysosomes are exposed to a pH of as low as 4.4. The purpose of this study is to evaluate how changes in the environmental pH within cells alter the fluidity of phospholipid membranes. Specifically, we studied pH-induced alterations in the surface arrangement of monounsaturated lipids with zwitterionic headgroups (phosphoethanolamine (PE) and phosphocholine (PC)) that are abundant in plasma membranes as well as anionic lipids (phosphatidylserine (PS) and phosphatidylglycerol (PG)) that are abundant in inner membranes using a combination of techniques including surface tension vs area measurements, interfacial microrheology, and fluorescence/atomic force microscopy. Using an active interfacial microrheology technique, we find that phospholipids with zwitterionic headgroups show a significant increase in their surface viscosity at acidic pH. This increase in surface viscosity is also found to depend on the size of the lipid headgroup, with a smaller headgroup showing a greater increase in viscosity. The observed pH-induced increase in viscosity is also accompanied by an increase in the cohesion pressure between zwitterionic molecules at acidic pH and a decrease in the average molecular area of the lipids, as measured by fitting the surface pressure isotherms to well-established equations of state. Because fluorescent images show no change in the phase of the lipids, we attribute this change in surface viscosity to the pH-induced reorientation of the P--N+ dipoles that form part of the polar lipid headgroup, resulting in increased lipid-lipid interactions. Anionic PG headgroups do not demonstrate this pH-induced change in viscosity, suggesting that the presence of a net negative charge on the headgroup causes electrostatic repulsion between the headgroups. Our results also show that active interfacial microrheology is a sensitive technique for detecting minute changes in the lipid headgroup orientation induced by changes in the local membrane environment, even in unsaturated phospholipids where the surface viscosity is close to the experimental detection limit.
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Affiliation(s)
| | | | - Nabil Alhakamy
- Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, King Abdulaziz University , Jeddah, KSA
- Department of Pharmaceutical Chemistry, University of Kansas , Lawrence, Kansas 66047, United States
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11
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Orczyk M, Wojciechowski K, Brezesinski G. Disordering Effects of Digitonin on Phospholipid Monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:3871-3881. [PMID: 28333465 DOI: 10.1021/acs.langmuir.6b04613] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Digitonin, a steroidal saponin obtained from the foxglove plant (Digitalis purpurea), displays a wide spectrum of biological properties and is often used as a model in mechanistic investigations of the biological activity of saponins. In the present study, Langmuir monolayers of zwitterionic (DPPC, DMPE, POPC, POPE, DSPC, DSPE, and DPPE) and ionic (DPPS and DPPG) phospholipids were employed in order to better understand the effect of digitonin on the lipid organization. For this purpose, a combination of surface pressure relaxation, infrared reflection absorption spectroscopy (IRRAS), and fluorescence microscopy measurements was used. The observed increase in surface pressure (Π) suggests that digitonin can adsorb at the air/water interface, both bare and covered with the uncompressed phospholipid monolayers. However, the detailed analysis of IRRAS and fluorescence microscopy data shows that digitonin interacts with the lipid monolayers in a very selective way, and both the headgroup and the lipid tails affect this interaction. Nevertheless, it should be noted that in no case did digitonin cause any disruptive effects on the monolayers. The DPPE and DPPS monolayers get disordered by penetration with digitonin, despite an increase in surface pressure, leading to an unprecedented LC-LE transition. Interestingly, saponin could be easily squeezed out of these monolayers by mechanical compression.
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Affiliation(s)
- M Orczyk
- Faculty of Chemistry, Warsaw University of Technology , Noakowskiego 3, 00-664 Warsaw, Poland
| | - K Wojciechowski
- Faculty of Chemistry, Warsaw University of Technology , Noakowskiego 3, 00-664 Warsaw, Poland
| | - G Brezesinski
- Max Planck Institute of Colloids and Interfaces , Science Park Potsdam-Golm, 14476 Potsdam, Germany
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12
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Sachan AK, Choi SQ, Kim KH, Tang Q, Hwang L, Lee KYC, Squires TM, Zasadzinski JA. Interfacial rheology of coexisting solid and fluid monolayers. SOFT MATTER 2017; 13:1481-1492. [PMID: 28125114 PMCID: PMC5720834 DOI: 10.1039/c6sm02797k] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Biologically relevant monolayer and bilayer films often consist of micron-scale high viscosity domains in a continuous low viscosity matrix. Here we show that this morphology can cause the overall monolayer fluidity to vary by orders of magnitude over a limited range of monolayer compositions. Modeling the system as a two-dimensional suspension in analogy with classic three-dimensional suspensions of hard spheres in a liquid solvent explains the rheological data with no adjustable parameters. In monolayers with ordered, highly viscous domains dispersed in a continuous low viscosity matrix, the surface viscosity increases as a power law with the area fraction of viscous domains. Changing the phase of the continuous matrix from a disordered fluid phase to a more ordered, condensed phase dramatically changes the overall monolayer viscosity. Small changes in the domain density and/or continuous matrix composition can alter the monolayer viscosity by orders of magnitude.
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Affiliation(s)
- A K Sachan
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA.
| | - S Q Choi
- Departments of Chemical and Biomolecular Engineering and KINC, KAIST, Daejeon, 305-701, Korea
| | - K H Kim
- Departments of Chemical and Biomolecular Engineering and KINC, KAIST, Daejeon, 305-701, Korea
| | - Q Tang
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA.
| | - L Hwang
- Department of Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, University of Chicago, Chicago, Illinois 60637, USA
| | - K Y C Lee
- Department of Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, University of Chicago, Chicago, Illinois 60637, USA
| | - T M Squires
- Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, USA
| | - J A Zasadzinski
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA.
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13
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Schwieger C, Blaffert J, Li Z, Kressler J, Blume A. Perfluorinated Moieties Increase the Interaction of Amphiphilic Block Copolymers with Lipid Monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:8102-15. [PMID: 27442444 DOI: 10.1021/acs.langmuir.6b01574] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The interaction of amphiphilic and triphilic block copolymers with lipid monolayers has been studied. Amphiphilic triblock copolymer PGMA20-PPO34-PGMA20 (GP) is composed of a hydrophobic poly(propylene oxide) (PPO) middle block that is flanked by two hydrophilic poly(glycerol monomethacrylate) (PGMA) side blocks. The attachment of a perfluoro-n-nonyl residue (F9) to either end of GP yields a triphilic polymer with the sequence F9-PGMA20-PPO34-PGMA20-F9 (F-GP). The F9 chains are fluorophilic, i.e., they have a tendency to demix in hydrophilic as well as in lipophilic environments. We investigated (i) the adsorption of both polymers to differently composed lipid monolayers and (ii) the compression behavior of mixed polymer/lipid monolayers. The lipid monolayers are composed of phospholipids with PC or PE headgroups and acyl chains of different length and saturation. Both polymers interact with lipid monolayers by inserting their hydrophobic moieties (PPO, F9). The interaction is markedly enhanced in the presence of F9 chains, which act as membrane anchors. GP inserts into lipid monolayers up to a surface pressure of 30 mN/m, whereas F-GP inserts into monolayers at up to 45 mN/m, suggesting that F-GP also inserts into lipid bilayer membranes. The adsorption of both polymers to lipid monolayers with short acyl chains is favored. Upon compression, a two-step squeeze-out of F-GP occurs, with PPO blocks being released into the aqueous subphase at 28 mN/m and the F9 chains being squeezed out at 48 mN/m. GP is squeezed out in one step at 28 mN/m because of the lack of F9 anchor groups. The liquid expanded (LE) to liquid condensed (LC) phase transition of DPPC and DMPE is maintained in the presence of the polymers, indicating that the polymers can be accommodated in LE- and LC-phase monolayers. These results show how fluorinated moieties can be included in the rational design of membrane-binding polymers.
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Affiliation(s)
- Christian Schwieger
- Institute of Chemistry, Martin Luther University Halle-Wittenberg , D-06099 Halle (Saale), Germany
| | - Jacob Blaffert
- Institute of Chemistry, Martin Luther University Halle-Wittenberg , D-06099 Halle (Saale), Germany
| | - Zheng Li
- Institute of Chemistry, Martin Luther University Halle-Wittenberg , D-06099 Halle (Saale), Germany
| | - Jörg Kressler
- Institute of Chemistry, Martin Luther University Halle-Wittenberg , D-06099 Halle (Saale), Germany
| | - Alfred Blume
- Institute of Chemistry, Martin Luther University Halle-Wittenberg , D-06099 Halle (Saale), Germany
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