1
|
Zuo YY. Comparative biophysical study of clinical surfactants using constrained drop surfactometry. Am J Physiol Lung Cell Mol Physiol 2024; 327:L535-L546. [PMID: 39159363 DOI: 10.1152/ajplung.00058.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Revised: 06/16/2024] [Accepted: 08/12/2024] [Indexed: 08/21/2024] Open
Abstract
Surfactant replacement therapy is crucial in managing neonatal respiratory distress syndrome (RDS). Currently licensed clinical surfactants in the United States and Europe, including Survanta, Infasurf, Curosurf, and Alveofact, are all derived from bovine or porcine sources. We conducted a comprehensive examination of the biophysical properties of these four clinical surfactant preparations under physiologically relevant conditions, using constrained drop surfactometry (CDS). The assessed biophysical properties included the adsorption rate, quasi-static and dynamic surface activity, resistance to surfactant inhibition by meconium, and the morphology of the adsorbed surfactant films. This comparative study unveiled distinct in vitro biophysical properties of these clinical surfactants and revealed correlations between their chemical composition, lateral film structure, and biophysical functionality. Notably, at 1 mg/mL, Survanta exhibited a significantly lower adsorption rate compared with the other preparations at the same surfactant concentration. At 10 mg/mL, Infasurf, Curosurf, and Survanta all demonstrated excellent dynamic surface activity, whereas Alveofact exhibited the poorest quasi-static and dynamic surface activity. The suboptimal surface activity of Alveofact is found to be correlated with its unique monolayer-predominant morphology, in contrast to other surfactants forming multilayers. Curosurf, in particular, showcased superior resistance to biophysical inhibition by meconium compared with other preparations. Understanding the diverse biophysical behaviors of clinical surfactants provides crucial insights for precision and personalized design in treating RDS and other respiratory conditions. The findings from this study contribute valuable perspectives for the development of more efficacious and fully synthetic surfactant preparations.NEW & NOTEWORTHY A thorough investigation into the biophysical properties of four animal-derived clinical surfactant preparations was conducted through constrained drop surfactometry under physiologically relevant conditions. This comparative study unveiled unique in vitro biophysical characteristics among these clinical surfactants, establishing correlations between their chemical composition, lateral film structure, and biophysical functionality. The acquired knowledge offers essential insights for the precise and personalized design of clinical surfactant for the treatment of respiratory distress syndrome and other respiratory conditions.
Collapse
Affiliation(s)
- Yi Y Zuo
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii, United States
- Department of Pediatrics, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, United States
| |
Collapse
|
2
|
Cejas JDP, Rosa AS, González Paz AN, Disalvo EA, Frías MDLA. Impact of chlorogenic acid on surface and phase properties of cholesterol-enriched phosphatidylcholine membranes. Arch Biochem Biophys 2024; 753:109913. [PMID: 38286353 DOI: 10.1016/j.abb.2024.109913] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 11/26/2023] [Accepted: 01/25/2024] [Indexed: 01/31/2024]
Abstract
This study analyses the insertion of Chlorogenic acid (CGA) in phosphatidylcholine (PC) membranes enriched with cholesterol (Chol). While cholesterol decreases the area per lipid and increases the dipole potential, CGA increases and decreases these values, respectively. When CGA is inserted into cholesterol-containing DMPC membranes, these effects cancel out, resulting in values that overlap with those of DMPC monolayers without Chol and CGA. The presence of CGA also compensates the increase of dipole potential produced by Chol which can be explain as a consequence of the orientation of CGA molecule at the interphase opposing the cholesterol dipole moieties and water dipoles. This compensatory effect is less effective when lipids lack carbonyl groups (CO). When monolayers are composed by unsaturated PCs the Chol compensation is found at higher concentrations of CGA due to the direct interaction between CGA and Chol. These results suggest that cholesterol modulates the interaction and distribution of CGA in the lipid membrane, which may have implications for its biological activity.
Collapse
Affiliation(s)
- Jimena Del P Cejas
- Applied Biophysics and Food Research Center (Centro de Investigaciones en Biofísica Aplicada y Alimentos, CIBAAL, National University of Santiago del Estero and CONICET), Laboratory of Biointerphases and Biomimetic Systems, RN 9 - Km 1125, 4206, Santiago del Estero, Argentina
| | - Antonio S Rosa
- Applied Biophysics and Food Research Center (Centro de Investigaciones en Biofísica Aplicada y Alimentos, CIBAAL, National University of Santiago del Estero and CONICET), Laboratory of Biointerphases and Biomimetic Systems, RN 9 - Km 1125, 4206, Santiago del Estero, Argentina
| | - Agustín N González Paz
- Applied Biophysics and Food Research Center (Centro de Investigaciones en Biofísica Aplicada y Alimentos, CIBAAL, National University of Santiago del Estero and CONICET), Laboratory of Biointerphases and Biomimetic Systems, RN 9 - Km 1125, 4206, Santiago del Estero, Argentina
| | - Edgardo A Disalvo
- Applied Biophysics and Food Research Center (Centro de Investigaciones en Biofísica Aplicada y Alimentos, CIBAAL, National University of Santiago del Estero and CONICET), Laboratory of Biointerphases and Biomimetic Systems, RN 9 - Km 1125, 4206, Santiago del Estero, Argentina
| | - María de Los A Frías
- Applied Biophysics and Food Research Center (Centro de Investigaciones en Biofísica Aplicada y Alimentos, CIBAAL, National University of Santiago del Estero and CONICET), Laboratory of Biointerphases and Biomimetic Systems, RN 9 - Km 1125, 4206, Santiago del Estero, Argentina.
| |
Collapse
|
3
|
Abstract
Pulmonary surfactant is a critical component of lung function in healthy individuals. It functions in part by lowering surface tension in the alveoli, thereby allowing for breathing with minimal effort. The prevailing thinking is that low surface tension is attained by a compression-driven squeeze-out of unsaturated phospholipids during exhalation, forming a film enriched in saturated phospholipids that achieves surface tensions close to zero. A thorough review of past and recent literature suggests that the compression-driven squeeze-out mechanism may be erroneous. Here, we posit that a surfactant film enriched in saturated lipids is formed shortly after birth by an adsorption-driven sorting process and that its composition does not change during normal breathing. We provide biophysical evidence for the rapid formation of an enriched film at high surfactant concentrations, facilitated by adsorption structures containing hydrophobic surfactant proteins. We examine biophysical evidence for and against the compression-driven squeeze-out mechanism and propose a new model for surfactant function. The proposed model is tested against existing physiological and pathophysiological evidence in neonatal and adult lungs, leading to ideas for biophysical research, that should be addressed to establish the physiological relevance of this new perspective on the function of the mighty thin film that surfactant provides.
Collapse
Affiliation(s)
- Fred Possmayer
- Department of Biochemistry, Western University, London, Ontario N6A 3K7, Canada
- Department of Obstetrics/Gynaecology, Western University, London, Ontario N6A 3K7, Canada
| | - Yi Y Zuo
- Department of Mechanical Engineering, University of Hawaii at Manon, Honolulu, Hawaii 96822, United States
- Department of Pediatrics, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii 96826, United States
| | - Ruud A W Veldhuizen
- Department of Physiology & Pharmacology, Western University, London, Ontario N6A 5C1, Canada
- Department of Medicine, Western University, London, Ontario N6A 3K7, Canada
- Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
| | - Nils O Petersen
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
- Department of Chemistry, Western University, London, Ontario N6A 5B7, Canada
| |
Collapse
|
4
|
Liekkinen J, Olżyńska A, Cwiklik L, Bernardino de la Serna J, Vattulainen I, Javanainen M. Surfactant Proteins SP-B and SP-C in Pulmonary Surfactant Monolayers: Physical Properties Controlled by Specific Protein-Lipid Interactions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:4338-4350. [PMID: 36917773 PMCID: PMC10061932 DOI: 10.1021/acs.langmuir.2c03349] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 02/07/2023] [Indexed: 06/18/2023]
Abstract
The lining of the alveoli is covered by pulmonary surfactant, a complex mixture of surface-active lipids and proteins that enables efficient gas exchange between inhaled air and the circulation. Despite decades of advancements in the study of the pulmonary surfactant, the molecular scale behavior of the surfactant and the inherent role of the number of different lipids and proteins in surfactant behavior are not fully understood. The most important proteins in this complex system are the surfactant proteins SP-B and SP-C. Given this, in this work we performed nonequilibrium all-atom molecular dynamics simulations to study the interplay of SP-B and SP-C with multicomponent lipid monolayers mimicking the pulmonary surfactant in composition. The simulations were complemented by z-scan fluorescence correlation spectroscopy and atomic force microscopy measurements. Our state-of-the-art simulation model reproduces experimental pressure-area isotherms and lateral diffusion coefficients. In agreement with previous research, the inclusion of either SP-B and SP-C increases surface pressure, and our simulations provide a molecular scale explanation for this effect: The proteins display preferential lipid interactions with phosphatidylglycerol, they reside predominantly in the lipid acyl chain region, and they partition into the liquid expanded phase or even induce it in an otherwise packed monolayer. The latter effect is also visible in our atomic force microscopy images. The research done contributes to a better understanding of the roles of specific lipids and proteins in surfactant function, thus helping to develop better synthetic products for surfactant replacement therapy used in the treatment of many fatal lung-related injuries and diseases.
Collapse
Affiliation(s)
- Juho Liekkinen
- Department
of Physics, University of Helsinki, FI-00560 Helsinki, Finland
| | - Agnieszka Olżyńska
- J.
Heyrovský Institute of Physical Chemistry, Czech Academy of
Sciences, CZ-18223 Prague, Czech Republic
| | - Lukasz Cwiklik
- J.
Heyrovský Institute of Physical Chemistry, Czech Academy of
Sciences, CZ-18223 Prague, Czech Republic
| | - Jorge Bernardino de la Serna
- National
Heart and Lung Institute, Imperial College
London, Sir Alexander Fleming Building, London SW7 2AZ, U.K.
- NIHR
Imperial Biomedical Research Centre, London SW7 2AZ, U.K.
| | - Ilpo Vattulainen
- Department
of Physics, University of Helsinki, FI-00560 Helsinki, Finland
| | - Matti Javanainen
- Institute
of Biotechnology, University of Helsinki, FI-00790 Helsinki, Finland
- Institute
of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, CZ-16100 Prague 6, Czech Republic
| |
Collapse
|
5
|
Dziura M, Castillo SR, DiPasquale M, Gbadamosi O, Zolnierczuk P, Nagao M, Kelley EG, Marquardt D. Investigating the Effect of Medium Chain Triglycerides on the Elasticity of Pulmonary Surfactant. Chem Res Toxicol 2023; 36:643-652. [PMID: 36926887 DOI: 10.1021/acs.chemrestox.2c00349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/18/2023]
Abstract
In recent years, vaping has increased in both popularity and ease of access. This has led to an outbreak of a relatively new condition known as e-cigarette/vaping-associated lung injury (EVALI). This injury can be caused by physical interactions between the pulmonary surfactant (PS) in the lungs and toxins typically found in vaping solutions, such as medium chain triglycerides (MCT). MCT has been largely used as a carrier agent within many cannabis products commercially available on the market. Pulmonary surfactant ensures proper respiration by maintaining low surface tensions and interface stability throughout each respiratory cycle. Therefore, any impediments to this system that negatively affect the efficacy of this function will have a strong hindrance on the individual's quality of life. Herein, neutron spin echo (NSE) and Langmuir trough rheology were used to probe the effects of MCT on the mechanical properties of pulmonary surfactant. Alongside a porcine surfactant extract, two lipid-only mimics of progressing complexity were used to study MCT effects in a range of systems that are representative of endogenous surfactant. MCT was shown to have a greater biophysical effect on bilayer systems compared to monolayers, which may align with biological data to propose a mechanism of surfactant inhibition by MCT oil.
Collapse
Affiliation(s)
- Maksymilian Dziura
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON N9B 3P4, Canada
| | - Stuart R Castillo
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON N9B 3P4, Canada
| | - Mitchell DiPasquale
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON N9B 3P4, Canada
| | - Omotayo Gbadamosi
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON N9B 3P4, Canada
| | - Piotr Zolnierczuk
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States
| | - Michihiro Nagao
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States.,Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, United States.,Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, United States
| | - Elizabeth G Kelley
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Drew Marquardt
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON N9B 3P4, Canada.,Department of Physics, University of Windsor, Windsor, ON N9B 3P4, Canada
| |
Collapse
|
6
|
Dayeen FR, Brandner BA, Martynowycz MW, Kucuk K, Foody MJ, Bu W, Hall SB, Gidalevitz D. Effects of cholesterol on the structure and collapse of DPPC monolayers. Biophys J 2022; 121:3533-3541. [PMID: 35841141 PMCID: PMC9515002 DOI: 10.1016/j.bpj.2022.07.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2022] [Revised: 06/02/2022] [Accepted: 07/05/2022] [Indexed: 11/29/2022] Open
Abstract
Cholesterol induces faster collapse by compressed films of pulmonary surfactant. Because collapse prevents films from reaching the high surface pressures achieved in the alveolus, most therapeutic surfactants remove or omit cholesterol. The studies here determined the structural changes by which cholesterol causes faster collapse by films of dipalmitoyl phosphatidylcholine, used as a simple model for the functional alveolar film. Measurements of isobaric collapse, with surface pressure held constant at 52 mN/m, showed that cholesterol had little effect until the mol fraction of cholesterol, Xchol, exceeded 0.20. Structural measurements of grazing incidence X-ray diffraction at ambient laboratory temperatures and a surface pressure of 44 mN/m, just below the onset of collapse, showed that the major structural change in an ordered phase occurred at lower Xchol. A centered rectangular unit cell with tilted chains converted to an untilted hexagonal structure over the range of Xchol = 0.0-0.1. For Xchol = 0.1-0.4, the ordered structure was nearly invariant; the hexagonal unit cell persisted, and the spacing of the chains was essentially unchanged. That invariance strongly suggests that above Xchol = 0.1, cholesterol partitions into a disordered phase, which coexists with the ordered domains. The phase rule requires that for a binary film with coexisting phases, the stoichiometries of the ordered and disordered regions must remain constant. Added cholesterol must increase the area of the disordered phase at the expense of the ordered regions. X-ray scattering from dipalmitoyl phosphatidylcholine/cholesterol fit with that prediction. The data also show a progressive decrease in the size of crystalline domains. Our results suggest that cholesterol promotes adsorption not by altering the unit cell of the ordered phase but by decreasing both its total area and the size of individual crystallites.
Collapse
Affiliation(s)
- Fazle R Dayeen
- Department of Physics, Center for Molecular Study of Condensed Soft Matter (μCoSM), Pritzker Institute of Biomedical Science and Engineering, Illinois Institute of Technology, Chicago, Illinois
| | - Bret A Brandner
- Pulmonary & Critical Care Medicine, Oregon Health & Science University, Portland, Oregon
| | - Michael W Martynowycz
- Howard Hughes Medical Institute and Department of Biological Chemistry, University of California Los Angeles, Los Angeles, California
| | - Kamil Kucuk
- Department of Physics, Center for Molecular Study of Condensed Soft Matter (μCoSM), Pritzker Institute of Biomedical Science and Engineering, Illinois Institute of Technology, Chicago, Illinois
| | - Michael J Foody
- Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois
| | - Wei Bu
- NSF's ChemMatCARS, Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois
| | - Stephen B Hall
- Pulmonary & Critical Care Medicine, Oregon Health & Science University, Portland, Oregon.
| | - David Gidalevitz
- Department of Physics, Center for Molecular Study of Condensed Soft Matter (μCoSM), Pritzker Institute of Biomedical Science and Engineering, Illinois Institute of Technology, Chicago, Illinois.
| |
Collapse
|
7
|
Rogachev AV, Novikova NN, Kovalchuk MV, Malakhova YN, Konovalov OV, Stepina ND, Shlyapnikova EA, Kanev IL, Shlyapnikov YM, Yakunin SN. Permeation of Nanoparticles into Pulmonary Surfactant Monolayer: In Situ X-ray Standing Wave Studies. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:3630-3640. [PMID: 35302765 DOI: 10.1021/acs.langmuir.1c02179] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
High-resolution X-ray techniques were applied to examine the effects of gold nanoparticles (size <5 nm) on natural pulmonary surfactant and pure DPPC monolayers preliminarily formed on water subphase in a Langmuir trough. Hydrophobic and hydrophilic nanoparticles were delivered from nanoaerosol using electrodeposition method. Grazing incidence diffraction, X-ray reflectivity, and X-ray standing wave measurements allow to monitor the changes in molecular organization of lipid monolayer and to locate the position of gold nanoparticles. X-ray experiments were performed over a period of 9-14 h. The obtained results evidenced that, on a long time scale, the deposition of nanoparticles, even at low doses, can induce pronounced alterations in lipid monolayer. The presented data can help to elucidate the mechanism of pulmonary translocation of inhaled nanoparticles that is of special interest for biomedical investigations of potential risk of nanoaerosols for human health.
Collapse
Affiliation(s)
- A V Rogachev
- National Research Center Kurchatov Institute, National Research Center Kurchatov Institute, Moscow, 123182 Russia
| | - N N Novikova
- National Research Center Kurchatov Institute, National Research Center Kurchatov Institute, Moscow, 123182 Russia
| | - M V Kovalchuk
- National Research Center Kurchatov Institute, National Research Center Kurchatov Institute, Moscow, 123182 Russia
| | - Yu N Malakhova
- National Research Center Kurchatov Institute, National Research Center Kurchatov Institute, Moscow, 123182 Russia
| | - O V Konovalov
- ESRF─The European Synchron Radiation Facility, 38043 Grenoble, France
| | - N D Stepina
- Shubnikov Institute of Crystallography, Federal Scientific Research Centre, "Crystallography and Photonics″, Russian Academy of Sciences, Moscow, 119333 Russia
| | - E A Shlyapnikova
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, 142290 Russia
| | - I L Kanev
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, 142290 Russia
| | - Yu M Shlyapnikov
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, 142290 Russia
| | - S N Yakunin
- National Research Center Kurchatov Institute, National Research Center Kurchatov Institute, Moscow, 123182 Russia
| |
Collapse
|
8
|
Liekkinen J, de Santos Moreno B, Paananen RO, Vattulainen I, Monticelli L, Bernardino de la Serna J, Javanainen M. Understanding the Functional Properties of Lipid Heterogeneity in Pulmonary Surfactant Monolayers at the Atomistic Level. Front Cell Dev Biol 2020; 8:581016. [PMID: 33304898 PMCID: PMC7701215 DOI: 10.3389/fcell.2020.581016] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 10/16/2020] [Indexed: 01/11/2023] Open
Abstract
Pulmonary surfactant is a complex mixture of lipids and proteins lining the interior of the alveoli, and constitutes the first barrier to both oxygen and pathogens as they progress toward blood circulation. Despite decades of study, the behavior of the pulmonary surfactant at the molecular scale is poorly understood, which hinders the development of effective surfactant replacement therapies, useful in the treatment of several lung-related diseases. In this work, we combined all-atom molecular dynamics simulations, Langmuir trough measurements, and AFM imaging to study synthetic four-component lipid monolayers designed to model protein-free pulmonary surfactant. We characterized the structural and dynamic properties of the monolayers with a special focus on lateral heterogeneity. Remarkably, simulations reproduce almost quantitatively the experimental data on pressure-area isotherms and the presence of lateral heterogeneities highlighted by AFM. Quite surprisingly, the pressure-area isotherms do not show a plateau region, despite the presence of liquid-condensed nanometer-sized domains at surface pressures larger than 20 mN/m. In the simulations, the liquid-condensed domains were small and transient, but they did not coalesce to yield a separate phase. They were only slightly enriched in DPPC and cholesterol, and their chemical composition remained very similar to the overall composition of the monolayer membrane. Instead, they differed from liquid-expanded regions in terms of membrane thickness (in agreement with AFM data), diffusion rates, as well as acyl chain packing and orientation. We hypothesize that such lateral heterogeneities are crucial for lung surfactant function, as they allow both efficient packing, to achieve low surface tension, and sufficient fluidity, critical for rapid adsorption to the air–liquid interface during the breathing cycle.
Collapse
Affiliation(s)
- Juho Liekkinen
- Department of Physics, University of Helsinki, Helsinki, Finland
| | - Berta de Santos Moreno
- National Heart & Lung Institute, Faculty of Medicine, Imperial College London, London, United Kingdom
| | - Riku O Paananen
- Helsinki Eye Lab, Ophthalmology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Ilpo Vattulainen
- Department of Physics, University of Helsinki, Helsinki, Finland.,Computational Physics Laboratory, Tampere University, Tampere, Finland.,MEMPHYS - Centre for Biomembrane Physics, Odense, Denmark
| | - Luca Monticelli
- Molecular Microbiology and Structural Biochemistry (MMSB), UMR 5086 CNRS & University of Lyon, Lyon, France
| | | | - Matti Javanainen
- Computational Physics Laboratory, Tampere University, Tampere, Finland.,Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague, Czechia
| |
Collapse
|
9
|
Andreev K, Martynowycz MW, Kuzmenko I, Bu W, Hall SB, Gidalevitz D. Structural Changes in Films of Pulmonary Surfactant Induced by Surfactant Vesicles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:13439-13447. [PMID: 33080138 PMCID: PMC8754419 DOI: 10.1021/acs.langmuir.0c01813] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
When compressed by the shrinking alveolar surface area during exhalation, films of pulmonary surfactant in situ reduce surface tension to levels at which surfactant monolayers collapse from the surface in vitro. Vesicles of pulmonary surfactant added below these monolayers slow collapse. X-ray scattering here determined the structural changes induced by the added vesicles. Grazing incidence X-ray diffraction on monolayers of extracted calf surfactant detected an ordered phase. Mixtures of dipalmitoyl phosphatidylcholine and cholesterol, but not the phospholipid alone, mimic that structure. At concentrations that stabilize the monolayers, vesicles in the subphase had no effect on the unit cell, and X-ray reflection showed that the film remained monomolecular. The added vesicles, however, produced a concentration-dependent increase in the diffracted intensity. These results suggest that the enhanced resistance to collapse results from enlargement by the additional material of the ordered phase.
Collapse
Affiliation(s)
- Konstantin Andreev
- Department of Physics, Center for Molecular Study of Condensed Soft Matter (μCoSM), Pritzker Institute of Biomedical Science and Engineering, Illinois Institute of Technology, Chicago, Illinois 60616, United States
| | - Michael W Martynowycz
- Department of Physics, Center for Molecular Study of Condensed Soft Matter (μCoSM), Pritzker Institute of Biomedical Science and Engineering, Illinois Institute of Technology, Chicago, Illinois 60616, United States
- X-ray Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
| | - Ivan Kuzmenko
- X-ray Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
| | - Wei Bu
- The Center for Advanced Radiation Sources (CARS), University of Chicago, Chicago, Illinois 60637, United States
| | - Stephen B Hall
- Pulmonary & Critical Care Medicine, Oregon Health & Science University, Portland, Oregon 97239, United States
| | - David Gidalevitz
- Department of Physics, Center for Molecular Study of Condensed Soft Matter (μCoSM), Pritzker Institute of Biomedical Science and Engineering, Illinois Institute of Technology, Chicago, Illinois 60616, United States
| |
Collapse
|
10
|
Korchowiec B, Stachowicz-Kuśnierz A, Korchowiec J. The role of DPPG in lung surfactant exposed to benzo[a]pyrene. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2019; 21:438-445. [PMID: 30729964 DOI: 10.1039/c8em00497h] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Lung surfactant (LS) occurs at the air-water interface in the alveoli. Its main function is to reduce the work needed to expand the alveoli during inhalation and prevent the alveolar collapse during exhalation. Disturbance of this complex interfacial system by the uptake of pollutant molecules can lead to changes in fluidity, permeability, phase separation and domain formation, which in turn can lead to serious impairment in lung function. Knowledge of the LS-pollutant interaction is essential for understanding the mechanism of this process. In this study, we investigate the interaction of LS models with benzo[a]pyrene (BaP). Dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylglycerol (DPPG) sodium salt, and their 4 : 1 mixture are used as LS models. Surface pressure-area isotherms and molecular dynamics simulations are employed to study the properties of LS monolayers. It was found that the addition of BaP has a destabilizing effect on the mixed DPPC/DPPG monolayer, manifested by the decrease in surface pressure. Compression of a monolayer during a respiratory cycle may expel BaP to the bulk solution. It was demonstrated that DPPG is an active component that prevents the BaP molecule from entering the water subphase; as a minor component of LS it can effectively reduce this process. In addition, the presence of BaP in LS models induces the reduction of monolayer hydration in the hydrophilic region and the increase in chain ordering in the hydrophobic region. The observed changes in monolayer fluidity and phase behavior can be a source of various lung function disorders.
Collapse
Affiliation(s)
- Beata Korchowiec
- Department of Physical Chemistry and Electrochemistry, Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Krakow, Poland
| | | | | |
Collapse
|
11
|
Stachowicz-Kuśnierz A, Cwiklik L, Korchowiec J, Rogalska E, Korchowiec B. The impact of lipid oxidation on the functioning of a lung surfactant model. Phys Chem Chem Phys 2018; 20:24968-24978. [PMID: 30239547 DOI: 10.1039/c8cp04496a] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Apart from being responsible for sufficient pulmonary compliance and preventing alveolar collapse, lung surfactant (LS) also forms the first barrier for uptake of inhaled pathogens. As such it is susceptible to damage caused by various deleterious compounds present in air, e.g. oxidants capable of oxidizing unsaturated LS lipids. This study examines the consequences of oxidizing 20% of unsaturated lipids in an LS model: a mixed 1 : 1 DPPC : POPC monolayer. POxnoPC (1-palmitoyl-2-(9-oxo-nonanoyl)-sn-glycero-3-phosphocholine) is considered as the main oxidation product. Experimental surface pressure-area isotherms and polarization-modulation infrared reflection-absorption spectroscopy are employed to probe changes in the macroscopic properties of the unsaturated lipid monolayer induced by oxidation. Microscopic details of the influence of oxidation on the monolayer's phase behavior are elucidated by molecular dynamics simulations at varying lipid packing. We demonstrate that unsaturated lipid oxidation shifts the isotherm towards larger areas and advances monolayer collapse. This is caused by a reversal of the oxidized sn-2 chains of POxnoPC towards the subphase, driven by electrostatic interactions between the aldehyde, glycerin, and water. Increased lipid bulkiness, hindered transition to the LC phase, and transfer of oxidized chain terminals to the subphase have been identified as the most troublesome consequences of this process. They result in the reduction of monolayer stability and its capability to withstand high surface pressures. This may lead to uncontrolled and irreversible loss of lipids from the surface.
Collapse
Affiliation(s)
- A Stachowicz-Kuśnierz
- Department of Theoretical Chemistry, Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Krakow, Poland.
| | | | | | | | | |
Collapse
|
12
|
Kumar K, Chavarha M, Loney RW, Weiss TM, Rananavare SB, Hall SB. The L γ Phase of Pulmonary Surfactant. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:6601-6611. [PMID: 29715426 PMCID: PMC6526724 DOI: 10.1021/acs.langmuir.8b00460] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
To determine how different components affect the structure of pulmonary surfactant, we measured X-ray scattering by samples derived from calf surfactant. The surfactant phospholipids demonstrated the essential characteristics of the Lγ phase: a unit cell with a lattice constant appropriate for two bilayers, and crystalline chains detected by wide-angle X-ray scattering (WAXS). The electron density profile, obtained from scattering by oriented films at different relative humidities (70-97%), showed that the two bilayers, arranged as mirror images, each contain two distinct leaflets with different thicknesses and profiles. The detailed structures suggest one ordered leaflet that would contain crystalline chains and one disordered monolayer likely to contain the anionic compounds, which constitute ∼10% of the surfactant phospholipids. The spacing and temperature dependence detected by WAXS fit with an ordered leaflet composed of dipalmitoyl phosphatidylcholine. Physiological levels of cholesterol had no effect on this structure. Removing the anionic phospholipids prevented formation of the Lγ phase. The cationic surfactant proteins inhibited Lγ structures, but at levels unlikely related to charge. Because the Lγ phase, if arranged properly, could produce a self-assembled ordered interfacial monolayer, the structure could have important functional consequences. Physiological levels of the proteins, however, inhibit formation of the Lγ structures at high relative humidities, making their physiological significance uncertain.
Collapse
Affiliation(s)
- Kamlesh Kumar
- Departments of Biochemistry & Molecular Biology, Medicine, and Physiology & Pharmacology, Oregon Heath & Science University, Portland, OR 97239-3098
| | - Mariya Chavarha
- Departments of Biochemistry & Molecular Biology, Medicine, and Physiology & Pharmacology, Oregon Heath & Science University, Portland, OR 97239-3098
| | - Ryan W. Loney
- Departments of Biochemistry & Molecular Biology, Medicine, and Physiology & Pharmacology, Oregon Heath & Science University, Portland, OR 97239-3098
| | - Thomas M. Weiss
- Stanford University, SLAC/SSRL Building 137, 2575 Sand Hill Road MS69, Menlo Park, CA 94025
| | | | - Stephen B. Hall
- Departments of Biochemistry & Molecular Biology, Medicine, and Physiology & Pharmacology, Oregon Heath & Science University, Portland, OR 97239-3098
- To whom correspondence should be addressed: Stephen B. Hall, Pulmonary & Critical Care Medicine, Mail Code UHN-67, Oregon Health & Science University, Portland, Oregon 97239-3098, , Telephone: (503) 494-6667
| |
Collapse
|
13
|
Nguyen TL, Perlman CE. Tracheal acid or surfactant instillation raises alveolar surface tension. J Appl Physiol (1985) 2018; 125:1357-1367. [PMID: 29771610 DOI: 10.1152/japplphysiol.00397.2017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Whether alveolar liquid surface tension, T, is elevated in the acute respiratory distress syndrome (ARDS) has not been demonstrated in situ in the lungs. Neither is it known how exogenous surfactant, which has failed to treat ARDS, affects in situ T. We aim to determine T in an acid-aspiration ARDS model before and after exogenous surfactant administration. In isolated rat lungs, we combine servo-nulling pressure measurement and confocal microscopy to determine alveolar liquid T according to the Laplace relation. Administering 0.01 N (pH 1.9) HCl solution by alveolar injection or tracheal instillation, to model gastric liquid aspiration, raises T. Subsequent surfactant administration fails to normalize T. Furthermore, in normal lungs, tracheal instillation of control saline or exogenous surfactant raises T. Lavaging the trachea with saline and injecting the lavage solution into the alveolus raises T, suggesting that tracheal instillation may wash T-raising airway contents to the alveolus. Adding 0.01 N HCl or 5 mM CaCl2-either of which aggregates mucins-to tracheal lavage solution reduces or eliminates the effect of lavage solution on alveolar T. Following tracheal saline instillation, liquid suctioned directly out of alveoli through a micropipette contains mucins. Additionally, alveolar injection of gastric mucin solution raises T. We conclude that 1) tracheal liquid instillation likely washes T-raising mucins to the alveolus and 2) even exogenous surfactant that could be delivered mucin-free to the alveolus might not normalize T in acid-aspiration ARDS. NEW & NOTEWORTHY We demonstrate in situ in isolated lungs that surface tension is elevated in an acid-aspiration acute respiratory distress syndrome (ARDS) model. Following tracheal liquid instillation, also in isolated lungs, we directly sample alveolar liquid. We find that liquid instillation into normal lungs washes mucins to the alveolus, thereby raising alveolar surface tension. Furthermore, even if exogenous surfactant could be delivered mucin-free to the alveolus, exogenous surfactant might fail to normalize alveolar surface tension in acid-aspiration ARDS.
Collapse
Affiliation(s)
- Tam L Nguyen
- Department of Biomedical Engineering, Stevens Institute of Technology , Hoboken, New Jersey
| | - Carrie E Perlman
- Department of Biomedical Engineering, Stevens Institute of Technology , Hoboken, New Jersey
| |
Collapse
|
14
|
Xu L, Bosiljevac G, Yu K, Zuo YY. Melting of the Dipalmitoylphosphatidylcholine Monolayer. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:4688-4694. [PMID: 29565138 DOI: 10.1021/acs.langmuir.8b00579] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Langmuir monolayer self-assembled at the air-water interface represents an excellent model for studying phase transition and lipid polymorphism in two dimensions. Compared with numerous studies of phospholipid phase transitions induced by isothermal compression, there are very scarce reports on two-dimensional phase transitions induced by isobaric heating. This is mainly due to technical difficulties of continuously regulating temperature variations while maintaining a constant surface pressure in a classical Langmuir-type film balance. Here, with technological advances in constrained drop surfactometry and closed-loop axisymmetric drop shape analysis, we studied the isobaric heating process of the dipalmitoylphosphatidylcholine (DPPC) monolayer. It is found that temperature and surface pressure are two equally important intensive properties that jointly determine the phase behavior of the phospholipid monolayer. We have determined a critical point of the DPPC monolayer at a temperature of 44 °C and a surface pressure of 57 mN/m. Beyond this critical point, no phase transition can exist in the DPPC monolayer, either by isothermal compression or by isobaric heating. The melting process of the DPPC monolayer studied here provides novel insights into the understanding of a wide range of physicochemical and biophysical phenomena, such as surface thermodynamics, critical phenomena, and biophysical study of pulmonary surfactants.
Collapse
Affiliation(s)
- Lu Xu
- Department of Mechanical Engineering , University of Hawaii at Manoa , Honolulu , Hawaii 96822 , United States
| | - Gordon Bosiljevac
- Department of Mechanical Engineering , University of Hawaii at Manoa , Honolulu , Hawaii 96822 , United States
| | - Kyle Yu
- Department of Mechanical Engineering , University of Hawaii at Manoa , Honolulu , Hawaii 96822 , United States
| | - Yi Y Zuo
- Department of Mechanical Engineering , University of Hawaii at Manoa , Honolulu , Hawaii 96822 , United States
- Department of Pediatrics, John A. Burns School of Medicine , University of Hawaii , Honolulu , Hawaii 96826 , United States
| |
Collapse
|
15
|
Thomas AN, Borden MA. Hydrostatic Pressurization of Lung Surfactant Microbubbles: Observation of a Strain-Rate Dependent Elasticity. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:13699-13707. [PMID: 29064252 DOI: 10.1021/acs.langmuir.7b03307] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The microbubble offers a unique platform to study lung surfactant mechanics at physiologically relevant geometry and length scale. In this study, we compared the response of microbubbles (∼15 μm initial radius) coated with pure dipalmitoyl-phosphatidylcholine (DPPC) versus naturally derived lung surfactant (SURVANTA) when subjected to linearly increasing hydrostatic pressure at different rates (0.5-2.3 kPa/s) at room temperature. The microbubbles contained perfluorobutane gas and were submerged in buffered saline saturated with perfluorobutane at atmospheric pressure. Bright-field microscopy showed that DPPC microbubbles compressed spherically and smoothly, whereas SURVANTA microbubbles exhibited wrinkling and smoothing cycles associated with buckling and collapse. Seismograph analysis showed that the SURVANTA collapse amplitude was constant, but the collapse rate increased with the pressurization rate. An analysis of the pressure-volume curves indicated that the dilatational elasticity increased during compression for both shell types. The initial dilatational elasticity for SURVANTA was nearly twice that of DPPC at higher pressurization rates (>1.5 kPa/s), producing a pressure drop of up to 60 kPa across the film prior to condensation of the perfluorobutane core. The strain-rate dependent stiffening of SURVANTA shells likely arises from their composition and microstructure, which provide enhanced in-plane monolayer rigidity and lateral repulsion from surface-associated collapse structures. Overall, these results provide new insights into lung surfactant mechanics and collapse behavior during compression.
Collapse
Affiliation(s)
- Alec N Thomas
- Department of Mechanical Engineering and ‡Materials Science and Engineering Program, University of Colorado , Boulder, Colorado 80309, United States
| | - Mark A Borden
- Department of Mechanical Engineering and ‡Materials Science and Engineering Program, University of Colorado , Boulder, Colorado 80309, United States
| |
Collapse
|
16
|
Stachowicz-Kuśnierz A, Trojan S, Cwiklik L, Korchowiec B, Korchowiec J. Modeling Lung Surfactant Interactions with Benzo[a]pyrene. Chemistry 2017; 23:5307-5316. [DOI: 10.1002/chem.201605945] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Indexed: 01/05/2023]
Affiliation(s)
| | - Sonia Trojan
- Department of Chemistry; Jagiellonian University; ul. Ingardena 3 30-060 Kraków Poland
| | - Lukasz Cwiklik
- J. Heyrovský Institute of Physical Chemistry; Academy of Sciences of the Czech Republic; v.v.i. Dolejškova 3 18223 Prague 8 Czech Republic
| | - Beata Korchowiec
- Department of Chemistry; Jagiellonian University; ul. Ingardena 3 30-060 Kraków Poland
| | - Jacek Korchowiec
- Department of Chemistry; Jagiellonian University; ul. Ingardena 3 30-060 Kraków Poland
| |
Collapse
|
17
|
Brandsma J, Postle AD. Analysis of the regulation of surfactant phosphatidylcholine metabolism using stable isotopes. Ann Anat 2017; 211:176-183. [PMID: 28351529 DOI: 10.1016/j.aanat.2017.02.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 02/27/2017] [Accepted: 02/28/2017] [Indexed: 01/22/2023]
Abstract
The pathways and mechanisms that regulate pulmonary surfactant synthesis, processing, secretion and catabolism have been extensively characterised using classical biochemical and analytical approaches. These have constructed a model, largely in experimental animals, for surfactant phospholipid metabolism in the alveolar epithelial cell whereby phospholipid synthesised on the endoplasmic reticulum is selectively transported to lamellar body storage vesicles, where it is subsequently processed before secretion into the alveolus. Surfactant phospholipid is a complex mixture of individual molecular species defined by the combination of esterified fatty acid groups and a comprehensive description of surfactant phospholipid metabolism requires consideration of the interactions between such molecular species. However, until recently, lipid analytical techniques have not kept pace with the considerable advances in understanding of the enzymology and molecular biology of surfactant metabolism. Refinements in electrospray ionisation mass spectrometry (ESI-MS) can now provide very sensitive platforms for the rapid characterisation of surfactant phospholipid composition in molecular detail. The combination of ESI-MS and administration of phospholipid substrates labelled with stable isotopes extends this analytical approach to the quantification of synthesis and turnover of individual molecular species of surfactant phospholipid. As this methodology does not involve radioactivity, it is ideally suited to application in clinical studies. This review will provide an overview of the metabolic processes that regulate the molecular specificity of surfactant phosphatidylcholine together with examples of how the application of stable isotope technologies in vivo has, for the first time, begun to explore regulation of the molecular specificity of surfactant synthesis in human subjects.
Collapse
Affiliation(s)
- Joost Brandsma
- Academic Unit of Clinical & Experimental Sciences, Faculty of Medicine, University of Southampton, United Kingdom
| | - Anthony D Postle
- Academic Unit of Clinical & Experimental Sciences, Faculty of Medicine, University of Southampton, United Kingdom.
| |
Collapse
|
18
|
Zuo YY, Chen R, Wang X, Yang J, Policova Z, Neumann AW. Phase Transitions in Dipalmitoylphosphatidylcholine Monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:8501-6. [PMID: 27479299 PMCID: PMC5522960 DOI: 10.1021/acs.langmuir.6b01482] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A self-assembled phospholipid monolayer at an air-water interface is a well-defined model system for studying surface thermodynamics, membrane biophysics, thin-film materials, and colloidal soft matter. Here we report a study of two-dimensional phase transitions in the dipalmitoylphosphatidylcholine (DPPC) monolayer at the air-water interface using a newly developed methodology called constrained drop surfactometry (CDS). CDS is superior to the classical Langmuir balance in its capacity for rigorous temperature control and leak-proof environments, thus making it an ideal alternative to the Langmuir balance for studying lipid polymorphism. In addition, we have developed a novel Langmuir-Blodgett (LB) transfer technique that allows the direct transfer of lipid monolayers from the droplet surface under well-controlled conditions. This LB transfer technique permits the direct visualization of phase coexistence in the DPPC monolayer. With these technological advances, we found that the two-dimensional phase behavior of the DPPC monolayer is analogous to the three-dimensional phase transition of a pure substance. This study has implications in the fundamental understanding of surface thermodynamics as well as applications such as self-assembled monolayers and pulmonary surfactant biophysics.
Collapse
Affiliation(s)
- Yi Y. Zuo
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
- Department of Pediatrics, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii 96826, United States
| | - Rimei Chen
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
| | - Xianju Wang
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
- College of Electronic Engineering, South China Agricultural University, Guangzhou, China 510642
| | - Jinlong Yang
- Department of Mechanical Engineering, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
| | - Zdenka Policova
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario Canada, M5S 3G8
| | - A. Wilhelm Neumann
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario Canada, M5S 3G8
| |
Collapse
|
19
|
Kotula AP, Anna SL. Insoluble layer deposition and dilatational rheology at a microscale spherical cap interface. SOFT MATTER 2016; 12:7038-7055. [PMID: 27478885 DOI: 10.1039/c5sm03133h] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The dilatational properties of insoluble monolayers are important for understanding the mechanics of biological systems and consumer products, but isolating the dilatational response of an interface is challenging due to the difficulties in separating dilatation from shear and other deformation modes. Oscillations of a microscale bubble radius are useful for generating purely dilatational flows, but the current deposition methods for insoluble layers onto fluid interfaces are not easily scaled down. In this paper, we describe a miscible solvent exchange procedure for generating insoluble layers at an air-water interface pinned at the tip of a capillary tens of micrometers in diameter. We show that the amount of surfactant adsorbed at the interface can be controlled by the initial concentration dissolved in isopropanol (the starting solvent) and the volumetric flow rate of solvent exchange. Surface pressure-area isotherms and dilatational moduli are measured concurrently for three insoluble surfactants: palmitic acid (PA), dimyristoylphosphatidylcholine (DMPC) and dipalmitoylphosphatidylcholine (DPPC). The isotherms measured on the microscale interface compare well with previous experiments performed on a Langmuir trough. However, the magnitudes of the dilatational moduli differ from those measured on either Langmuir trough or pendant drop apparatuses. Several possible reasons for the observed differences are discussed. A comparison of the dilatational modulus with the Gibbs elasticity is used to determine the presence of dilatational extra stresses at the interface. The isotherm and dilatational modulus of the insoluble component of the industrial surfactant Tween 80 are measured using this approach. The methods developed here also open the possibility for future study of the important role of finite size effects on microstructure formation and the resulting interfacial mechanics.
Collapse
Affiliation(s)
- Anthony P Kotula
- Center for Complex Fluids Engineering, Carnegie Mellon University, Pittsburgh, PA, USA.
| | - Shelley L Anna
- Center for Complex Fluids Engineering, Carnegie Mellon University, Pittsburgh, PA, USA.
| |
Collapse
|
20
|
Baoukina S, Tieleman DP. Computer simulations of lung surfactant. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2431-2440. [PMID: 26922885 DOI: 10.1016/j.bbamem.2016.02.030] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Revised: 02/21/2016] [Accepted: 02/23/2016] [Indexed: 01/26/2023]
Abstract
Lung surfactant lines the gas-exchange interface in the lungs and reduces the surface tension, which is necessary for breathing. Lung surfactant consists mainly of lipids with a small amount of proteins and forms a monolayer at the air-water interface connected to bilayer reservoirs. Lung surfactant function involves transfer of material between the monolayer and bilayers during the breathing cycle. Lipids and proteins are organized laterally in the monolayer; selected species are possibly preferentially transferred to bilayers. The complex 3D structure of lung surfactant and the exact roles of lipid organization and proteins remain important goals for research. We review recent simulation studies on the properties of lipid monolayers, monolayers with phase coexistence, monolayer-bilayer transformations, lipid-protein interactions, and effects of nanoparticles on lung surfactant. This article is part of a Special Issue entitled: Biosimulations edited by Ilpo Vattulainen and Tomasz Róg.
Collapse
Affiliation(s)
- Svetlana Baoukina
- Department of Biological Sciences and Centre for Molecular Simulation, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada.
| | - D Peter Tieleman
- Department of Biological Sciences and Centre for Molecular Simulation, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada.
| |
Collapse
|
21
|
Orgeig S, Morrison JL, Daniels CB. Evolution, Development, and Function of the Pulmonary Surfactant System in Normal and Perturbed Environments. Compr Physiol 2015; 6:363-422. [PMID: 26756637 DOI: 10.1002/cphy.c150003] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Surfactant lipids and proteins form a surface active film at the air-liquid interface of internal gas exchange organs, including swim bladders and lungs. The system is uniquely positioned to meet both the physical challenges associated with a dynamically changing internal air-liquid interface, and the environmental challenges associated with the foreign pathogens and particles to which the internal surface is exposed. Lungs range from simple, transparent, bag-like units to complex, multilobed, compartmentalized structures. Despite this anatomical variability, the surfactant system is remarkably conserved. Here, we discuss the evolutionary origin of the surfactant system, which likely predates lungs. We describe the evolution of surfactant structure and function in invertebrates and vertebrates. We focus on changes in lipid and protein composition and surfactant function from its antiadhesive and innate immune to its alveolar stability and structural integrity functions. We discuss the biochemical, hormonal, autonomic, and mechanical factors that regulate normal surfactant secretion in mature animals. We present an analysis of the ontogeny of surfactant development among the vertebrates and the contribution of different regulatory mechanisms that control this development. We also discuss environmental (oxygen), hormonal and biochemical (glucocorticoids and glucose) and pollutant (maternal smoking, alcohol, and common "recreational" drugs) effects that impact surfactant development. On the adult surfactant system, we focus on environmental variables including temperature, pressure, and hypoxia that have shaped its evolution and we discuss the resultant biochemical, biophysical, and cellular adaptations. Finally, we discuss the effect of major modern gaseous and particulate pollutants on the lung and surfactant system.
Collapse
Affiliation(s)
- Sandra Orgeig
- School of Pharmacy & Medical Sciences and Sansom Institute for Health Research, University of South Australia, Adelaide, Australia
| | - Janna L Morrison
- School of Pharmacy & Medical Sciences and Sansom Institute for Health Research, University of South Australia, Adelaide, Australia
| | - Christopher B Daniels
- School of Pharmacy & Medical Sciences and Sansom Institute for Health Research, University of South Australia, Adelaide, Australia
| |
Collapse
|
22
|
Composition, structure and mechanical properties define performance of pulmonary surfactant membranes and films. Chem Phys Lipids 2014; 185:153-75. [PMID: 25260665 DOI: 10.1016/j.chemphyslip.2014.09.002] [Citation(s) in RCA: 192] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 09/06/2014] [Accepted: 09/11/2014] [Indexed: 12/30/2022]
Abstract
The respiratory surface in the mammalian lung is stabilized by pulmonary surfactant, a membrane-based system composed of multiple lipids and specific proteins, the primary function of which is to minimize the surface tension at the alveolar air-liquid interface, optimizing the mechanics of breathing and avoiding alveolar collapse, especially at the end of expiration. The goal of the present review is to summarize current knowledge regarding the structure, lipid-protein interactions and mechanical features of surfactant membranes and films and how these properties correlate with surfactant biological function inside the lungs. Surfactant mechanical properties can be severely compromised by different agents, which lead to surfactant inhibition and ultimately contributes to the development of pulmonary disorders and pathologies in newborns, children and adults. A detailed comprehension of the unique mechanical and rheological properties of surfactant layers is crucial for the diagnostics and treatment of lung diseases, either by analyzing the contribution of surfactant impairment to the pathophysiology or by improving the formulations in surfactant replacement therapies. Finally, a short review is also included on the most relevant experimental techniques currently employed to evaluate lung surfactant mechanics, rheology, and inhibition and reactivation processes.
Collapse
|
23
|
Alexandrova L, Grigorov L. Studying three phase contact in the system air/DMPC water dispersion/silica. Colloids Surf A Physicochem Eng Asp 2014. [DOI: 10.1016/j.colsurfa.2014.06.005] [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]
|
24
|
|
25
|
Kwan JJ, Borden MA. Lipid monolayer collapse and microbubble stability. Adv Colloid Interface Sci 2012; 183-184:82-99. [PMID: 22959721 DOI: 10.1016/j.cis.2012.08.005] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Revised: 08/10/2012] [Accepted: 08/10/2012] [Indexed: 12/16/2022]
Abstract
Microbubbles are micrometer-size gaseous particles suspended in water, and they are often stabilized by a lipid monolayer shell. Natural microbubbles are found in freshwater and saltwater systems, and engineered microbubbles have a variety of applications in food sciences, biotechnology and medicine. Lipid-coated microbubbles are found to have remarkable stability and mechanical behavior owing to the resistance of the lipid monolayer encapsulation to collapse. The purpose of this review is to tie in recent observations of lipid-coated microbubble dissolution and gas exchange with current literature on the physics of lipid monolayer collapse in the context of lung surfactant. Based on this analysis, we conclude that microbubble shells collapse through the nucleation of microscopic folds, which then catalyze the formation and aggregation of new folds, leading to macroscopic folding events. This process results in a cyclic behavior of crumple-to-smooth transitions, which can be modulated through lipid composition. Eventually, the microbubbles stabilize at 1-2 μm diameter, regardless of initial size or lipid composition, and various mechanisms for this stabilization are postulated. Our ultimate goal is to inspire the reader to consider lipid monolayer collapse as the main long-term stabilizing mechanism for lipid-coated microbubbles, and to stimulate the use of microbubbles as a platform for studying monolayer collapse phenomena.
Collapse
|
26
|
Khoojinian H, Goodarzi JP, Hall SB. Optical factors in the rapid analysis of captive bubbles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:14081-14089. [PMID: 22950373 PMCID: PMC3489924 DOI: 10.1021/la301864d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Bubbles and droplets offer multiple advantages over Langmuir troughs for compressing interfacial films. Experiments, however, that manipulate films to maintain constant surface tension (γ) present problems because they require feedback. Measurements of bubbles and droplets calculate γ from the shape of the interface, and calculations in real time based on finding the Laplacian shape that best fits the interface can be difficult. Faster methods obtain γ from only the height and diameter, but the bubbles and droplets rest against a solid support, which obscures one section of the interface and complicates measurements of the height. The experiments here investigated a series of optical variables that affect the visualized location of the different surfaces for captive bubbles. The pitch of the support and camera as well as the collimation of illuminating light affected the accuracy of the measured dimensions. The wavelength of illumination altered the opacity of turbid subphases and hydrated gel used to form the solid support. The width of all visualized edges depended on the spectral width and collimation of the illuminating light. The intensity of illumination had little effect on the images as long as the grayscale remained within the dynamic range of the camera. With optimization of these optical factors, the width of all edges narrowed significantly. The surfaces away from the solid support approached the infinite sharpness of the physical interface. With these changes, the grayscale at the upper interface provided the basis for locating all surfaces, which improved real-time measurements based on the height and diameter.
Collapse
Affiliation(s)
| | | | - Stephen B. Hall
- Address correspondence to: Stephen B. Hall, Pulmonary & Critical Care Medicine, Mail Code UHN-67, OHSU, Portland, OR 97239-3098, Telephone: 503-494-6667,
| |
Collapse
|
27
|
Brown NJ, Dohm MT, Bernardino de la Serna J, Barron AE. Biomimetic N-terminal alkylation of peptoid analogues of surfactant protein C. Biophys J 2011; 101:1076-85. [PMID: 21889444 DOI: 10.1016/j.bpj.2011.04.055] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Revised: 04/11/2011] [Accepted: 04/18/2011] [Indexed: 10/17/2022] Open
Abstract
Surfactant protein C (SP-C) is a hydrophobic lipopeptide that is critical for lung function, in part because it physically catalyzes the formation of surface-associated surfactant reservoirs. Many of SP-C's key biophysical properties derive from its highly stable and hydrophobic α-helix. However, SP-C's posttranslational modification with N-terminal palmitoyl chains also seems to be quite important. We created a new (to our knowledge) class of variants of a synthetic, biomimetic family of peptide mimics (peptoids) that allow us to study the functional effects of biomimetic N-terminal alkylation in vitro. Mimics were designed to emulate the amphipathic patterning, helicity, and hydrophobicity of SP-C, and to include no, one, or two vicinal amide-linked, N-terminal octadecyl chains (providing a reach equivalent to that of natural palmitoyl chains). Pulsating bubble surfactometry and Langmuir-Wilhelmy surface balance studies showed that alkylation improved biomimetic surface activities, yielding lower film compressibility and lower maximum dynamic surface tensions. Atomic force microscopy studies indicated that alkyl chains bind to and retain segregated interfacial surfactant phases at low surface tensions by inducing 3D structural transitions in the monolayer's fluid-like phase, forming surfactant-associated reservoirs. Peptoid-based SP-C mimics are easily produced and purified, and offer much higher chemical and secondary structure stability than polypeptide-based mimics. In surfactant replacements intended for medical use, synthetic SP mimics reduce the odds of pathogen contamination, which may facilitate the wider use of surfactant treatment of respiratory disorders and diseases.
Collapse
Affiliation(s)
- Nathan J Brown
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, USA
| | | | | | | |
Collapse
|
28
|
Lessons from the biophysics of interfaces: Lung surfactant and tear fluid. Prog Retin Eye Res 2011; 30:204-15. [DOI: 10.1016/j.preteyeres.2011.02.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Revised: 02/11/2011] [Accepted: 02/15/2011] [Indexed: 12/26/2022]
|
29
|
Overvelde M, Garbin V, Sijl J, Dollet B, de Jong N, Lohse D, Versluis M. Nonlinear shell behavior of phospholipid-coated microbubbles. ULTRASOUND IN MEDICINE & BIOLOGY 2010; 36:2080-92. [PMID: 21030140 DOI: 10.1016/j.ultrasmedbio.2010.08.015] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2010] [Revised: 08/21/2010] [Accepted: 08/27/2010] [Indexed: 05/11/2023]
Abstract
The influence of the stabilizing phospholipid-coating on the nonlinear dynamics of ultrasound contrast agent microbubbles is investigated. We record the radial dynamics of individual microbubbles with an ultra high-speed camera as a function of both driving pressure and frequency. The viscoelastic shell was found to enhance the nonlinear bubble response at acoustic pressures as low as 10 kPa. For increasing acoustic pressures a decrease of the frequency of maximum response was observed for a distinct class of bubbles, leading to a pronounced skewness of the resonance curve, which we show to be the origin of the "thresholding" behavior (Emmer et al. 2007). For the other bubbles, the frequency of maximum response was found to lie just above the resonance frequency of an uncoated microbubble and to be independent of the applied acoustic pressure. The shell-buckling bubble model (Marmottant et al. 2005), which accounts for buckling and rupture of the shell, captures both cases for a unique set of the shell parameters, the relevant parameter being the phospholipid concentration at the bubble interface.
Collapse
Affiliation(s)
- Marlies Overvelde
- Physics of Fluids Group, Research Institute for Biomedical Technology and Technical Medicine MIRA, University of Twente, Enschede, The Netherlands
| | | | | | | | | | | | | |
Collapse
|
30
|
Keating E, Waring AJ, Walther FJ, Possmayer F, Veldhuizen RAW, Petersen NO. A ToF-SIMS study of the lateral organization of lipids and proteins in pulmonary surfactant systems. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:614-21. [PMID: 21110942 DOI: 10.1016/j.bbamem.2010.11.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Revised: 10/27/2010] [Accepted: 11/12/2010] [Indexed: 01/11/2023]
Abstract
Pulmonary surfactant is a complex lipid-protein mixture whose main function is to reduce the surface tension at the air-liquid interface of alveoli to minimize the work of breathing. The exact mechanism by which surfactant monolayers and multilayers are formed and how they lower surface tension to very low values during lateral compression remains uncertain. We used time-of-flight secondary ion mass spectrometry to study the lateral organization of lipids and peptide in surfactant preparations ranging in complexity. We show that we can successfully determine the location of phospholipids, cholesterol and a peptide in surfactant Langmuir-Blodgett films and we can determine the effect of cholesterol and peptide addition. A thorough understanding of the lateral organization of PS interfacial films will aid in our understanding of the role of each component as well as different lipid-lipid and lipid-protein interactions. This may further our understanding of pulmonary surfactant function.
Collapse
|
31
|
Possmayer F, Hall SB, Haller T, Petersen NO, Zuo YY, Bernardino de la Serna J, Postle AD, Veldhuizen RAW, Orgeig S. Recent advances in alveolar biology: some new looks at the alveolar interface. Respir Physiol Neurobiol 2010; 173 Suppl:S55-64. [PMID: 20206718 DOI: 10.1016/j.resp.2010.02.014] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Revised: 01/30/2010] [Accepted: 02/23/2010] [Indexed: 11/18/2022]
Abstract
This article examines the manner in which some new methodologies and novel concepts have contributed to our understanding of how pulmonary surfactant reduces alveolar surface tension. Investigations utilizing small angle X-ray diffraction, inverted interface fluorescence microscopy, time of flight-secondary ion mass spectroscopy, atomic force microscopy, two-photon fluorescence microscopy and electrospray mass spectroscopy are highlighted and a new model of ventilation-induced acute lung injury described. This contribution attempts to emphasize how these new approaches have resulted in a fuller appreciation of events presumably occurring at the alveolar interface.
Collapse
Affiliation(s)
- Fred Possmayer
- University of Western Ontario, Departments of Obstetrics/Gynaecology and Biochemistry, London, Ontario, Canada.
| | | | | | | | | | | | | | | | | |
Collapse
|
32
|
Andreassen S, Steimle KL, Mogensen ML, Bernardino de la Serna J, Rees S, Karbing DS. The effect of tissue elastic properties and surfactant on alveolar stability. J Appl Physiol (1985) 2010; 109:1369-77. [PMID: 20724566 DOI: 10.1152/japplphysiol.00844.2009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This paper presents a novel mathematical model of alveoli, which simulates the effects of tissue elasticity and surfactant on the stability of human alveoli. The model incorporates a spherical approximation to the alveolar geometry, the hysteretic behavior of pulmonary surfactant and tissue elasticity. The model shows that the alveolus without surfactant and the elastic properties of the lung tissue are always at an unstable equilibrium, with the capability both to collapse irreversibly and to open with infinite volume when the alveolus has small opening radii. During normal tidal breathing, the alveolus can becomes stable, if surfactant is added. Including the passive effect of tissue elasticity stabilizes the alveolus, further allowing the alveoli to be stable, even for lung volumes below residual volume. The model is the first to describe the combined effects of tissue elasticity and surfactant on alveolar stability. The model may be used as an integrated part of a more comprehensive model of the respiratory system, since it can predict opening pressures of alveoli.
Collapse
Affiliation(s)
- Steen Andreassen
- Center for Model-Based Medical Decision Support, Aalborg University, Aalborg, Denmark.
| | | | | | | | | | | |
Collapse
|
33
|
Physicochemical effects enhance surfactant transport in pulsatile motion of a semi-infinite bubble. Biophys J 2010; 96:312-27. [PMID: 18849416 DOI: 10.1529/biophysj.108.131805] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2008] [Accepted: 09/05/2008] [Indexed: 01/18/2023] Open
Abstract
In this study, we investigate the sorption of pulmonary surfactant (Infasurf, Ony, Buffalo, NY) occurring at the air-liquid interface of a semi-infinite finger of air as it oscillates and progresses along a small rigid tube (1 mm inner diameter) occluded with a surfactant-doped solution of concentrations C=0.1, 0.05, or 0.01 mg/mL. This simple experimental model of pulmonary airway reopening is designed to examine how altering the fluid flow field may lower reopening pressures and lead to a reduction in airway wall damage that is associated with the mechanical ventilation of an obstructed pulmonary system in airways of the deep lung with depleted endogenous and little exogenous surfactant. We analyzed a range of pulsatile flow scenarios by varying the oscillation frequency (0< or =f < or =1 Hz), the oscillation flow waveform, and the steady flow rate (Q(steady)=0.1 or 0.01 mL/min). These experimental studies indicate that a high frequency (1 Hz, amplitude = 5 mm), fast-forward oscillation waveform superimposed onto a fast steady flow (0.1 mL/min) substantially reduces mean reopening pressures (31%) as a consequence of the modified flow field and the commensurate increase in surfactant transport and adsorption. This result suggests that imposing high frequency, low amplitude oscillations during airway reopening will help to diminish ventilator-induced lung injury.
Collapse
|
34
|
Saleem M, Meyer MC, Breitenstein D, Galla HJ. Calcium ions as "miscibility switch": colocalization of surfactant protein B with anionic lipids under absolute calcium free conditions. Biophys J 2009; 97:500-8. [PMID: 19619464 DOI: 10.1016/j.bpj.2009.05.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2008] [Revised: 05/07/2009] [Accepted: 05/08/2009] [Indexed: 11/28/2022] Open
Abstract
One of the main determinants of lung surfactant function is the complex interplay between its protein and lipid components. The lipid specificity of surfactant protein B (SP-B), however, and the protein's ability to selectively squeeze out lipids, has remained contradictory. In this work we present, for the first time to our knowledge, by means of time-of-flight secondary ion mass spectrometry chemical imaging, a direct evidence for colocalization of SP-B as well as its model peptide KL(4) with negatively charged dipalmitoylphosphatidylglycerol under absolute calcium free conditions. Our results prove that protein/lipid localization depends on the miscibility of all surfactant components, which itself is influenced by subphase ionic conditions. In contrast to our earlier studies reporting SP-B/KL(4) colocalization with zwitterionic dipalmitoylphosphatidylcholine, in the presence of even the smallest traces of calcium, we finally evidence an apparent reversal of protein/lipid mixing behavior upon calcium removal with ethylene diamine tetraacetic acid. In addition, scanning force microscopy measurements reveal that by depleting the subphase from calcium ions the protrusion formation ability of SP-B or KL(4) is not hampered. However, in the case of KL(4), distinct differences in protrusion morphology and height are visible. Our results support the idea that calcium ions act as a "miscibility switch" in surfactant model systems and probably are one of the major factors steering lipid/protein mixing behavior as well as influencing the protein's protrusion formation ability.
Collapse
Affiliation(s)
- Mohammed Saleem
- Institute of Biochemistry, University of Münster, Münster, Germany
| | | | | | | |
Collapse
|
35
|
Saad SMI, Policova Z, Acosta EJ, Neumann AW. Axisymmetric drop shape analysis-constrained sessile drop (ADSA-CSD): a film balance technique for high collapse pressures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:10843-10850. [PMID: 18759471 DOI: 10.1021/la801683q] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Collapse pressure of insoluble monolayers is a property determined from surface pressure/area isotherms. Such isotherms are commonly measured by a Langmuir film balance or a drop shape technique using a pendant drop constellation (ADSA-PD). Here, a different embodiment of a drop shape analysis, called axisymmetric drop shape analysis-constrained sessile drop (ADSA-CSD) is used as a film balance. It is shown that ADSA-CSD has certain advantages over conventional methods. The ability to measure very low surface tension values (e.g., <2 mJ/m2), an easier deposition procedure than in a pendant drop setup, and leak-proof design make the constrained sessile drop constellation a better choice than the pendant drop constellation in many situations. Results of compression isotherms are obtained on three different monolayers: octadecanol, dipalmitoyl-phosphatidyl-choline (DPPC), and dipalmitoyl-phosphatidyl-glycerol (DPPG). The collapse pressures are found to be reproducible and in agreement with previous methods. For example, the collapse pressure of DPPC is found to be 70.2 mJ/m2. Such values are not achievable with a pendant drop. The collapse pressure of octadecanol is found to be 61.3 mJ/m2, while that of DPPG is 59.0 mJ/m2. The physical reasons for these differences are discussed. The results also show a distinctive difference between the onset of collapse and the ultimate collapse pressure (ultimate strength) of these films. ADSA-CSD allows detailed study of this collapse region.
Collapse
Affiliation(s)
- Sameh M I Saad
- Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Road, Toronto, Ontario, Canada M5S 3G8
| | | | | | | |
Collapse
|
36
|
Abstract
Pulmonary surfactant spreads on the thin ( approximately 0.1 microm) liquid layer that lines the alveoli, forming a film that reduces surface tension and allows normal respiration. Pulmonary surfactant deposited in vitro on liquid layers that are several orders of magnitude thicker, however, does not reach the low surface tensions ( approximately 0.001 N/m) achieved in the lungs during exhalation when the surfactant film compresses. This is due to collapse, a surface phase transition during which the surfactant film, rather than decreasing surface tension by increasing its surface density, becomes thicker at constant surface tension ( approximately 0.024 N/m). Formation of the collapse phase requires transport of surfactant to collapse sites, and this transport can be hindered in thinner liquid layers by viscous resistance to motion. Our objective is to determine the effect of the liquid-layer thickness on surfactant transport, which might affect surfactant collapse. To this end, we developed a mathematical model that accounts for the effect of the liquid-layer thickness on surfactant transport, and focused on surfactant spreading and collapse. Model simulations showed a marked decrease in collapse rates for thinner liquid layers, but this decrease was not enough to completely explain differences in surfactant film behavior between in vitro and in situ experiments.
Collapse
|
37
|
Rugonyi S, Biswas SC, Hall SB. The biophysical function of pulmonary surfactant. Respir Physiol Neurobiol 2008; 163:244-55. [PMID: 18632313 DOI: 10.1016/j.resp.2008.05.018] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2008] [Revised: 05/23/2008] [Accepted: 05/24/2008] [Indexed: 01/12/2023]
Abstract
Pulmonary surfactant lowers surface tension in the lungs. Physiological studies indicate two key aspects of this function: that the surfactant film forms rapidly; and that when compressed by the shrinking alveolar area during exhalation, the film reduces surface tension to very low values. These observations suggest that surfactant vesicles adsorb quickly, and that during compression, the adsorbed film resists the tendency to collapse from the interface to form a 3D bulk phase. Available evidence suggests that adsorption occurs by way of a rate-limiting structure that bridges the gap between the vesicle and the interface, and that the adsorbed film avoids collapse by undergoing a process of solidification. Current models, although incomplete, suggest mechanisms that would partially explain both rapid adsorption and resistance to collapse as well as how different constituents of pulmonary surfactant might affect its behavior.
Collapse
Affiliation(s)
- Sandra Rugonyi
- Division of Biomedical Engineering, Oregon Health & Science University, Portland, OR 97239-3098, USA.
| | | | | |
Collapse
|
38
|
Ghadiali SN, Gaver DP. Biomechanics of liquid-epithelium interactions in pulmonary airways. Respir Physiol Neurobiol 2008; 163:232-43. [PMID: 18511356 DOI: 10.1016/j.resp.2008.04.008] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2008] [Revised: 04/09/2008] [Accepted: 04/10/2008] [Indexed: 01/11/2023]
Abstract
The delicate structure of the lung epithelium makes it susceptible to surface tension induced injury. For example, the cyclic reopening of collapsed and/or fluid-filled airways during the ventilation of injured lungs generates hydrodynamic forces that further damage the epithelium and exacerbate lung injury. The interactions responsible for epithelial injury during airway reopening are fundamentally multiscale, since air-liquid interfacial dynamics affect global lung mechanics, while surface tension forces operate at the molecular and cellular scales. This article will review the current state-of-knowledge regarding the effect of surface tension forces on (a) the mechanics of airway reopening and (b) epithelial cell injury. Due to the complex nature of the liquid-epithelium system, a combination of computational and experimental techniques are being used to elucidate the mechanisms of surface-tension induced lung injury. Continued research is leading to an integrated understanding of the biomechanical and biological interactions responsible for cellular injury during airway reopening. This information may lead to novel therapies that minimize ventilation induced lung injury.
Collapse
Affiliation(s)
- Samir N Ghadiali
- Department of Mechanical Engineering and Mechanics, Bioengineering Program, Lehigh University, Bethlehem, PA 18015, USA.
| | | |
Collapse
|
39
|
Duncan SL, Larson RG. Comparing experimental and simulated pressure-area isotherms for DPPC. Biophys J 2008; 94:2965-86. [PMID: 18199666 PMCID: PMC2275714 DOI: 10.1529/biophysj.107.114215] [Citation(s) in RCA: 163] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Accepted: 12/03/2007] [Indexed: 11/18/2022] Open
Abstract
Although pressure-area isotherms are commonly measured for lipid monolayers, it is not always appreciated how much they can vary depending on experimental factors. Here, we compare experimental and simulated pressure-area isotherms for dipalmitoylphosphatidylcholine (DPPC) at temperatures ranging between 293.15 K and 323.15 K, and explore possible factors influencing the shape and position of the isotherms. Molecular dynamics simulations of DPPC monolayers using both coarse-grained (CG) and atomistic models yield results that are in rough agreement with some of the experimental isotherms, but with a steeper slope in the liquid-condensed region than seen experimentally and shifted to larger areas. The CG lipid model gives predictions that are very close to those of atomistic simulations, while greatly improving computational efficiency. There is much more variation among experimental isotherms than between isotherms obtained from CG simulations and from the most refined simulation available. Both atomistic and CG simulations yield liquid-condensed and liquid-expanded phase area compressibility moduli that are significantly larger than those typically measured experimentally, but compare well with some experimental values obtained under rapid compression.
Collapse
Affiliation(s)
- Susan L Duncan
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan, USA
| | | |
Collapse
|
40
|
Zuo YY, Veldhuizen RAW, Neumann AW, Petersen NO, Possmayer F. Current perspectives in pulmonary surfactant--inhibition, enhancement and evaluation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:1947-77. [PMID: 18433715 DOI: 10.1016/j.bbamem.2008.03.021] [Citation(s) in RCA: 361] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 12/06/2007] [Revised: 03/26/2008] [Accepted: 03/26/2008] [Indexed: 02/06/2023]
Abstract
Pulmonary surfactant (PS) is a complicated mixture of approximately 90% lipids and 10% proteins. It plays an important role in maintaining normal respiratory mechanics by reducing alveolar surface tension to near-zero values. Supplementing exogenous surfactant to newborns suffering from respiratory distress syndrome (RDS), a leading cause of perinatal mortality, has completely altered neonatal care in industrialized countries. Surfactant therapy has also been applied to the acute respiratory distress syndrome (ARDS) but with only limited success. Biophysical studies suggest that surfactant inhibition is partially responsible for this unsatisfactory performance. This paper reviews the biophysical properties of functional and dysfunctional PS. The biophysical properties of PS are further limited to surface activity, i.e., properties related to highly dynamic and very low surface tensions. Three main perspectives are reviewed. (1) How does PS permit both rapid adsorption and the ability to reach very low surface tensions? (2) How is PS inactivated by different inhibitory substances and how can this inhibition be counteracted? A recent research focus of using water-soluble polymers as additives to enhance the surface activity of clinical PS and to overcome inhibition is extensively discussed. (3) Which in vivo, in situ, and in vitro methods are available for evaluating the surface activity of PS and what are their relative merits? A better understanding of the biophysical properties of functional and dysfunctional PS is important for the further development of surfactant therapy, especially for its potential application in ARDS.
Collapse
Affiliation(s)
- Yi Y Zuo
- Department of Biochemistry, University of Western Ontario, London, Ontario, Canada
| | | | | | | | | |
Collapse
|
41
|
Mao G, Desai J, Flach CR, Mendelsohn R. Structural characterization of the monolayer-multilayer transition in a pulmonary surfactant model: IR studies of films transferred at continuously varying surface pressures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:2025-2034. [PMID: 18198907 DOI: 10.1021/la702612p] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The four-component system acyl chain perdeuterated 1,2-dipalmitoylphosphatidylcholine (DPPC)/1,2-dipalmitoylphosphatidylglycerol/ (DPPG)/pulmonary surfactant protein SP-C/cholesterol provides a useful model for in vitro biophysical studies of the reversible monolayer to multilayer transition that occurs during compression <--> expansion cycles in the lung. Monolayer films of this mixture (with chain perdeuterated DPPC-d62) at the air/water interface have been transferred to solid substrates under conditions of continuously varying surface pressure, an approach termed COVASP (continuously varying surface pressures) (Langmuir 2007, 23, 4958). The thermodynamic properties of the Langmuir films have been examined with pressure-area isotherms, while the molecular properties of the film constituents in the transferred films in the monolayer and multilayer phases have been examined with IR spectroscopy. Quantitative intensity measurements of the DPPC-d62, DPPG, and SP-C components in each phase reveal that the DPPG and SP-C constituents are relatively enriched in the multilayer compared with the DPPC-d62, although all three species are present in both phases. Some molecular structure information is available from the surface-pressure-induced variation in IR parameters. The DPPC-d62 exhibits slightly increased conformational order in the multilayer phase as detected from decreases in the CD2 stretching frequencies upon compression, while the lipid phosphate residues become dehydrated, as deduced from increases in the 1245 cm-1 symmetric PO2- stretching frequency. A small increase is observed in the protein amide I frequency; possible interpretations of these changes are presented. The current observations are compared with ideas contained in the "squeeze-out hypothesis" (Handbook of Physiology, The Respiratory System; American Physiological Society Press: Bethesda, MD, 1986; Vol. III, p 247) and in the "liquid crystalline collapse" model (Biophys. J. 2003, 84, 3792). Within the limitation of the current procedures, the data contain elements from both these descriptions of the monolayer transformation. Extensions and possible limitations of the COVASP-IR method are discussed.
Collapse
Affiliation(s)
- Guangru Mao
- Department of Chemistry, Olson Hall, Newark College, Rutgers University, Newark, New Jersey 07102, USA
| | | | | | | |
Collapse
|
42
|
Atomic force microscopy studies of functional and dysfunctional pulmonary surfactant films. I. Micro- and nanostructures of functional pulmonary surfactant films and the effect of SP-A. Biophys J 2008; 94:3549-64. [PMID: 18212010 DOI: 10.1529/biophysj.107.122648] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Monolayers of a functional pulmonary surfactant (PS) can reach very low surface tensions well below their equilibrium value. The mechanism by which PS monolayers reach such low surface tensions and maintain film stability remains unknown. As shown previously by fluorescence microscopy, phospholipid phase transition and separation seem to be important for the normal biophysical properties of PS. This work studied phospholipid phase transitions and separations in monolayers of bovine lipid extract surfactant using atomic force microscopy. Atomic force microscopy showed phospholipid phase separation on film compression and a monolayer-to-multilayer transition at surface pressure 40-50 mN/m. The tilted-condensed phase consisted of domains not only on the micrometer scale, as detected previously by fluorescence microscopy, but also on the nanometer scale, which is below the resolution limits of conventional optical methods. The nanodomains were embedded uniformly within the liquid-expanded phase. On compression, the microdomains broke up into nanodomains, thereby appearing to contribute to tilted-condensed and liquid-expanded phase remixing. Addition of surfactant protein A altered primarily the nanodomains and promoted the formation of multilayers. We conclude that the nanodomains play a predominant role in affecting the biophysical properties of PS monolayers and the monolayer-to-multilayer transition.
Collapse
|
43
|
Bernhard W, Schmiedl A, Koster G, Orgeig S, Acevedo C, Poets CF, Postle AD. Developmental changes in rat surfactant lipidomics in the context of species variability. Pediatr Pulmonol 2007; 42:794-804. [PMID: 17659602 DOI: 10.1002/ppul.20657] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Lung surfactant comprises mainly phosphatidylcholine (PC) species together with phosphatidylglycerols and surfactant proteins (SP) SP-A to -D. Changes in the concentrations of its principal components dipalmitoyl-PC, palmitoylmyristoyl-PC, palmitoylpalmitoleoyl-PC relative to developmental, structural and physiological differences are only partially understood. Particularly, their attribution to differences in air-liquid interface curvature, compared with dynamic parameters, such as respiratory rate, are controversial. We postulated that during alveolarization the changes in these principal PC components of surfactant differ from those in other phospholipid parameters, and that across endothermic vertebrates their concentrations are related to lung physiology rather than structure. We therefore investigated in rats from postnatal day (d)1 to d42 the pattern of surfactant phospholipids relative to alveolarization (d4-d14), and we discuss these changes in terms of molecular adaptation to pulmonary structure or physiology. Contrary to mammals with advanced alveolarization and increased respiratory rate (RR) at term, concentrations of dipalmitoyl-PC (49-52%) and palmitoylmyristoyl-PC (7-9%) in lung lavage fluid were identical at d1 and d42. At d7-d14, when in rats RR is increased, palmitoyl-myristoyl-PC transiently increased by 2.5- to 3.9-fold at the expense of dipalmitoyl-PC (-32% to 34%) and palmitoyl-palmitoleoyl-PC (-16%). Other lipidomic changes followed essentially different patterns of increase or decrease. Palmitoyl-myristoyl-PC was increased in large aggregates suggesting that it is an integral component of active surfactant. In the overall context of vertebrates, irrespective of age and lung structure, fractions of palmitoyl-myristoyl-PC, dipalmitoyl-PC and palmitoyl-palmitoleoyl-PC correlate with differences in RR rather than alveolar curvature. In adult mammals, however, only concentrations of palmitoyl-palmitoleoyl-PC correlate with RR.
Collapse
Affiliation(s)
- Wolfgang Bernhard
- Department of Neonatology, Faculty of Medicine, Eberhard-Karls-University, Tübingen, Germany.
| | | | | | | | | | | | | |
Collapse
|
44
|
Lhert F, Yan W, Biswas SC, Hall SB. Effects of hydrophobic surfactant proteins on collapse of pulmonary surfactant monolayers. Biophys J 2007; 93:4237-43. [PMID: 17720730 PMCID: PMC2098737 DOI: 10.1529/biophysj.107.111823] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
To determine if hydrophobic surfactant proteins affect the stability of pulmonary surfactant monolayers at an air/water interface, the studies reported here compared the kinetics of collapse for the complete set of lipids in calf surfactant with and without the proteins. Monomolecular films spread at the surface of captive bubbles were compressed at 37 degrees C to surface pressures above 46 mN/m, at which collapse first occurred. The rate of area-compression required to maintain a constant surface pressure was measured to directly determine the rate of collapse. For films with and without the proteins, higher surface pressures initially produced faster collapse, but the rates then reached a maximum and decreased to values <0.04 min(-1) above 53 mN/m. The maximum rate for the lipids with the proteins (1.22 +/- 0.28 min(-1)) was almost twice the value for the lipids alone (0.71 +/- 0.15 min(-1)). Because small increments in surface pressure produced large shifts in the rate close to the fastest collapse, compressions at a series of constant speeds also established the threshold rate required to achieve high surface pressure as an indirect indication of the fastest collapse. Both samples produced a sharply defined threshold that occurred at slightly faster compression with the proteins present, supporting the conclusion of the direct measurements that the proteins produce a faster maximum rate of collapse. Our results indicate that at 47-53 mN/m, the hydrophobic surfactant proteins destabilize the compressed monolayers and tend to limit access to the higher surface pressures at which the lipid films become metastable.
Collapse
Affiliation(s)
- Florence Lhert
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, Oregon 97239, USA
| | | | | | | |
Collapse
|
45
|
Keating E, Rahman L, Francis J, Petersen A, Possmayer F, Veldhuizen R, Petersen NO. Effect of cholesterol on the biophysical and physiological properties of a clinical pulmonary surfactant. Biophys J 2007; 93:1391-401. [PMID: 17526587 PMCID: PMC1929052 DOI: 10.1529/biophysj.106.099762] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Pulmonary surfactant is a complex mixture of lipids and proteins that forms a surface-active film at the air-water interface of alveoli capable of reducing surface tension to near 0 mN/m. The role of cholesterol, the major neutral lipid component of pulmonary surfactant, remains uncertain. We studied the physiological effect of cholesterol by monitoring blood oxygenation levels of surfactant-deficient rats treated or not treated with bovine lipid extract surfactant (BLES) containing zero or physiological amounts of cholesterol. Our results indicate no significant difference between BLES and BLES containing cholesterol immediately after treatment; however, during ventilation, BLES-treated animals maintained higher PaO2 values compared to BLES+cholesterol-treated animals. We used a captive bubble tensiometer to show that physiological amounts of cholesterol do not have a detrimental effect on the surface activity of BLES at 37 degrees C. The effect of cholesterol on topography and lateral organization of BLES Langmuir-Blodgett films was also investigated using atomic force microscopy. Our data indicate that cholesterol induces the formation of domains within liquid-ordered domains (Lo). We used time-of-flight-secondary ion mass spectrometry and principal component analysis to show that cholesterol is concentrated in the Lo phase, where it induces structural changes.
Collapse
Affiliation(s)
- Eleonora Keating
- Department of Chemistry, Surface Science Western, Western Science Center, Lawson Health Research Institute, University of Western Ontario, London, Canada
| | | | | | | | | | | | | |
Collapse
|
46
|
Ma G, Allen HC. New insights into lung surfactant monolayers using vibrational sum frequency generation spectroscopy. Photochem Photobiol 2007; 82:1517-29. [PMID: 16930094 DOI: 10.1562/2006-06-30-ir-958] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
At the air-water interface, interfacial molecular structure, intermolecular interactions, film relaxation and film respreading of model lung surfactant monolayers were studied using vibrational sum frequency generation (VSFG) spectroscopy combined with a Langmuir film balance. Chain-perdeuterated dipalmitoylphosphatidylcholine (DPPC-d62), palmitoyloleoyl-phosphatidylglycerol (POPG), palmitic acid (PA) and tripalmitin were investigated. In the DPPC-d62-PA binary monolayer, PA showed a condensing effect on the DPPC chains. On the contrary, in the DPPC-d62-POPG binary monolayer, POPG showed a fluidizing effect on the DPPC chains. In the ternary monolayer system of DPPC-d62-POPG-PA, the balance between the fluidizing and the condensing effect was also observed. In addition, the film relaxation behavior of DPPC-d62 and the enhanced film stability of DPPC-d62 caused by the addition of tripalmitin were observed. Real-time VSFG was also employed to study the respreading properties of a complex lung surfactant mixture containing DPPC-d62, POPG, PA and KL4 (a mimic of SP-B) peptide, which revealed DPPC enrichment after film compression.
Collapse
Affiliation(s)
- Gang Ma
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH, USA
| | | |
Collapse
|
47
|
Acosta EJ, Gitiafroz R, Zuo YY, Policova Z, Cox PN, Hair ML, Neumann AW. Effect of humidity on lung surfactant films subjected to dynamic compression/expansion cycles. Respir Physiol Neurobiol 2007; 155:255-67. [DOI: 10.1016/j.resp.2006.06.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2006] [Revised: 06/23/2006] [Accepted: 06/26/2006] [Indexed: 10/24/2022]
|
48
|
Zuo YY, Acosta E, Cox PN, Li D, Neumann AW. Effect of compressed bovine lipid extract surfactant films on oxygen transfer. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:1339-46. [PMID: 17241056 DOI: 10.1021/la061608+] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
In the lungs, oxygen transfer from the inspired air to the capillary blood needs to cross the surfactant lining layer of the alveoli. Therefore, the gas transfer characteristics of lung surfactant film are of fundamental physiological interest. However, previous in vitro studies-most relied on the Langmuir-type balance-fail to cover the low surface tension range (i.e., less than the equilibrium surface tension of approximately 25 mJ/m2) due to film leakage. We have recently developed a novel in vitro experimental strategy, the combination of axisymmetric drop shape analysis and captive bubble technique (ADSA-CB), in studying the effect of surfactant films on interfacial gas transfer (Langmuir 2005, 21, 5446). In the present work, ADSA-CB is used as a micro-film-balance to study the effect of compressed bovine lipid extract surfactant (BLES) films on oxygen transfer. A low surface tension ranging from approximately 25 mJ/m2 to 2 mJ/m2 is studied. The experimental results suggest that lung surfactant films at a low surface tension near 2 mJ/m2 provide resistance to oxygen transfer, as indicated by a decrease of 30-50% in the mass transfer coefficient (kL) of oxygen in BLES suspensions with respect to water. At higher surface tension (i.e., >6 mJ/m2), the resistance to oxygen transfer is only modest, i.e., the decrease in kL is less than 20% compared to water. The experimental results suggest that lung surfactant plays a role in oxygen transfer in the pulmonary system.
Collapse
Affiliation(s)
- Yi Y Zuo
- Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Road, Toronto, Ontario M5S 3G8, Canada
| | | | | | | | | |
Collapse
|
49
|
Ma G, Allen HC. Condensing effect of palmitic acid on DPPC in mixed Langmuir monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:589-97. [PMID: 17209610 DOI: 10.1021/la061870i] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The interaction between deuterated dipalmitoylphosphatidylcholine (DPPC-d62) and palmitic acid (PA) in mixed Langmuir monolayers is studied using vibrational sum frequency generation (VSFG) spectroscopy. Palmitic acid is an additive in exogenous lung surfactant preparations such as Survanta and Surfaxin. The effect of PA on the chain conformation and orientation of DPPC in the liquid-expanded and condensed phases is explored. A condensing effect of PA on DPPC is observed with VSFG. At 12 mN/m, DPPC-d62 alone is in the liquid-expanded phase. Adding PA increases the conformational ordering of DPPC chains and causes DPPC to transition from the expanded phase into the condensed phase. At 42 mN/m, DPPC-d62 and PA form a mixed structure in the condensed phase. The presence of PA decreases the chain tilt angle of DPPC, increasing the orientational ordering of DPPC chains. At 42 mN/m, there is also evidence from the frequency red shift of the PO2- symmetric stretch that the carboxyl group of PA forms a hydrogen bond with the phosphate group of DPPC in the condensed phase. From this work the effect of PA on DPPC is 2-fold: (1) PA increases the chain ordering of DPPC and promotes the LE and TC phase separation and (2) due to the miscibility between DPPC and PA in the condensed phase, PA decreases the collapse pressure.
Collapse
Affiliation(s)
- Gang Ma
- Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA
| | | |
Collapse
|
50
|
Abstract
Monomolecular films of phospholipids in the liquid-expanded (LE) phase after supercompression to high surface pressures (pi), well above the equilibrium surface pressure (pi(e)) at which fluid films collapse from the interface to form a three-dimensional bulk phase, and in the tilted-condensed (TC) phase both replicate the resistance to collapse that is characteristic of alveolar films in the lungs. To provide the basis for determining which film is present in the alveolus, we measured the melting characteristics of monolayers containing TC dipalmitoyl phosphatidylcholine (DPPC), as well as supercompressed 1-palmitoyl-2-oleoyl phosphatidylcholine and calf lung surfactant extract (CLSE). Films generated by appropriate manipulations on a captive bubble were heated from < or =27 degrees C to > or =60 degrees C at different constant pi above pi(e). DPPC showed the abrupt expansion expected for the TC-LE phase transition, followed by the contraction produced by collapse. Supercompressed CLSE showed no evidence of the TC-LE expansion, arguing that supercompression did not simply convert the mixed lipid film to TC DPPC. For both DPPC and CLSE, the melting point, taken as the temperature at which collapse began, increased at higher pi, in contrast to 1-palmitoyl-2-oleoyl phosphatidylcholine, for which higher pi produced collapse at lower temperatures. For pi between 50 and 65 mN/m, DPPC melted at 48-55 degrees C, well above the main transition for bilayers at 41 degrees C. At each pi, CLSE melted at temperatures >10 degrees C lower. The distinct melting points for TC DPPC and supercompressed CLSE provide the basis by which the nature of the alveolar film might be determined from the temperature-dependence of pulmonary mechanics.
Collapse
Affiliation(s)
- Wenfei Yan
- Department of Biochemistry, Oregon Health & Science University, Portland, OR 97239-3098, USA
| | | | | | | |
Collapse
|