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21 pages, 6130 KiB

Open AccessArticle

Impact of Engineered Carbon Nanodiamonds on the Collapse Mechanism of Model Lung Surfactant Monolayers at the Air-Water Interface

by Aishik Chakraborty, Amanda Hertel, Hayley Ditmars and Prajnaparamita Dhar

Molecules 2020, 25(3), 714; https://doi.org/10.3390/molecules25030714 - 7 Feb 2020

Cited by 5 | Viewed by 2414

Abstract

Understanding interactions between inhaled nanoparticles and lung surfactants (LS) present at the air-water interface in the lung, is critical to assessing the toxicity of these nanoparticles. Specifically, in this work, we assess the impact of engineered carbon nanoparticles (ECN) on the ability of [...] Read more.

Understanding interactions between inhaled nanoparticles and lung surfactants (LS) present at the air-water interface in the lung, is critical to assessing the toxicity of these nanoparticles. Specifically, in this work, we assess the impact of engineered carbon nanoparticles (ECN) on the ability of healthy LS to undergo reversible collapse, which is essential for proper functioning of LS. Using a Langmuir trough, multiple compression-expansion cycles are performed to assess changes in the surface pressure vs. area isotherms with time and continuous cyclic compression-expansion. Further, theoretical analysis of the isotherms is used to calculate the ability of these lipid systems to retain material during monolayer collapse, due to interactions with ECNs. These results are complemented with fluorescence images of alterations in collapse mechanisms in these monolayer films. Four different model phospholipid systems, that mimic the major compositions of LS, are used in this study. Together, our results show that the ECN does not impact the mechanism of collapse. However, the ability to retain material at the interface during monolayer collapse, as well as re-incorporation of material after a compression-expansion cycle is altered to varying extent by ECNs and depends on the composition of the lipid mixtures. Full article

(This article belongs to the Special Issue Fluid Interfaces: From Colloids, Surfactants, Polymers and Nanoparticles to Their Mixtures)

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13 pages, 4771 KiB

Open AccessFeature PaperArticle

Interfacial Behavior of Oligo(Ethylene Glycol) Dendrons Spread Alone and in Combination with a Phospholipid as Langmuir Monolayers at the Air/Water Interface

by Da Shi, Dinh-Vu Nguyen, Mounir Maaloum, Jean-Louis Gallani, Delphine Felder-Flesch and Marie Pierre Krafft

Molecules 2019, 24(22), 4114; https://doi.org/10.3390/molecules24224114 - 14 Nov 2019

Cited by 4 | Viewed by 2778

Abstract

Dendrons consisting of two phosphonate functions and three oligo(ethylene glycol) (OEG) chains grafted on a central phenoxyethylcarbamoylphenoxy group were synthesized and investigated as Langmuir monolayers at the surface of water. The OEG chain in the para position was grafted with a t-Bu [...] Read more.

Dendrons consisting of two phosphonate functions and three oligo(ethylene glycol) (OEG) chains grafted on a central phenoxyethylcarbamoylphenoxy group were synthesized and investigated as Langmuir monolayers at the surface of water. The OEG chain in the para position was grafted with a t-Bu end-group, a hydrocarbon chain, or a partially fluorinated chain. These dendrons are models of structurally related OEG dendrons that were found to significantly improve the stability of aqueous dispersions of iron oxide nanoparticles when grafted on their surface. Compression isotherms showed that all OEG dendrons formed liquid-expanded Langmuir monolayers at large molecular areas. Further compression led to a transition ascribed to the solubilization of the OEG chains in the aqueous phase. Brewster angle microscopy (BAM) provided evidence that the dendrons fitted with hydrocarbon chains formed liquid-expanded monolayers throughout compression, whilst those fitted with fluorinated end-groups formed crystalline-like domains, even at large molecular areas. Dimyristoylphosphatidylcholine and dendron molecules were partially miscible in monolayers. The deviations to ideality were larger for the dendrons fitted with a fluorocarbon end-group chain than for those fitted with a hydrocarbon chain. Brewster angle microscopy and atomic force microscopy supported the view that the dendrons were ejected from the phospholipid monolayer during the OEG conformational transition and formed crystalline domains on the surface of the monolayer. Full article

(This article belongs to the Special Issue Fluid Interfaces: From Colloids, Surfactants, Polymers and Nanoparticles to Their Mixtures)

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16 pages, 1210 KiB

Open AccessArticle

Reflectometry Reveals Accumulation of Surfactant Impurities at Bare Oil/Water Interfaces

by Ernesto Scoppola, Samantha Micciulla, Lucas Kuhrts, Armando Maestro, Richard A. Campbell, Oleg V. Konovalov, Giovanna Fragneto and Emanuel Schneck

Molecules 2019, 24(22), 4113; https://doi.org/10.3390/molecules24224113 - 14 Nov 2019

Cited by 10 | Viewed by 2951

Abstract

Bare interfaces between water and hydrophobic media like air or oil are of fundamental scientific interest and of great relevance for numerous applications. A number of observations involving water/hydrophobic interfaces have, however, eluded a consensus mechanistic interpretation so far. Recent theoretical studies ascribe [...] Read more.

Bare interfaces between water and hydrophobic media like air or oil are of fundamental scientific interest and of great relevance for numerous applications. A number of observations involving water/hydrophobic interfaces have, however, eluded a consensus mechanistic interpretation so far. Recent theoretical studies ascribe these phenomena to an interfacial accumulation of charged surfactant impurities in water. In the present work, we show that identifying surfactant accumulation with X-ray reflectometry (XRR) or neutron reflectometry (NR) is challenging under conventional contrast configurations because interfacial surfactant layers are then hardly visible. On the other hand, both XRR and NR become more sensitive to surfactant accumulation when a suitable scattering length contrast is generated by using fluorinated oil. With this approach, significant interfacial accumulation of surfactant impurities at the bare oil/water interface is observed in experiments involving standard cleaning procedures. These results suggest that surfactant impurities may be a limiting factor for the investigation of fundamental phenomena involving water/hydrophobic interfaces. Full article

(This article belongs to the Special Issue Fluid Interfaces: From Colloids, Surfactants, Polymers and Nanoparticles to Their Mixtures)

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14 pages, 3811 KiB

Open AccessArticle

Structure of Langmuir Monolayers of Perfluorinated Fatty Acids: Evidence of a New 2D Smectic C Phase

by Philippe Fontaine, Eduardo J. M. Filipe, Marie-Claude Fauré, Tomas Rego, Stephanie Taßler, Ana Carolina Alves, Gonçalo M. C. Silva, Pedro Morgado and Michel Goldmann

Molecules 2019, 24(19), 3590; https://doi.org/10.3390/molecules24193590 - 5 Oct 2019

Cited by 7 | Viewed by 3434

Abstract

Due to the characteristic chain rigidity and weak intermolecular interactions of perfluorinated substances, the phase diagram of Langmuir monolayer formed by perfluorinated molecules has been interpreted so far as displaying only two phases, a 2D gas (G) and a liquid condensed (LC). However, [...] Read more.

Due to the characteristic chain rigidity and weak intermolecular interactions of perfluorinated substances, the phase diagram of Langmuir monolayer formed by perfluorinated molecules has been interpreted so far as displaying only two phases, a 2D gas (G) and a liquid condensed (LC). However, in this work, we presented Grazing Incidence X-ray Diffraction measurements, which exhibit two diffraction peaks on the transition plateau: One is the signature of the hexagonal structure of the LC phase, the second one is associated to the low-density fluid phase and is thus more ordered than expected for a 2D gas or a typical fluid phase. Atomistic molecular dynamics simulations, performed on the transition plateau, revealed the existence of clusters in which domains of vertical molecules organized in a hexagonal lattice coexist with domains of parallel lines formed by tilted molecules, a new structure that could be described as a “2D smectic C” phase. Moreover, the diffraction spectrum calculated from the simulation trajectories compared favorably with the experimental spectra, fully validating the simulations and the proposed interpretation. The results were also in agreement with the thermodynamic analysis of the fluid phase and X-ray Reflectivity experiments performed before and after the transition between these two phases. Full article

(This article belongs to the Special Issue Fluid Interfaces: From Colloids, Surfactants, Polymers and Nanoparticles to Their Mixtures)

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16 pages, 1819 KiB

Open AccessArticle

Surfactant-Like Behavior for the Adsorption of Mixtures of a Polycation and Two Different Zwitterionic Surfactants at the Water/Vapor Interface

by Andrew Akanno, Eduardo Guzmán, Laura Fernández-Peña, Francisco Ortega and Ramón G. Rubio

Molecules 2019, 24(19), 3442; https://doi.org/10.3390/molecules24193442 - 23 Sep 2019

Cited by 25 | Viewed by 3205

Abstract

The bulk and interfacial properties of solutions formed by a polycation (i.e., poly(diallyl-dimethylammonium chloride), PDADMAC) and two different zwitterionic surfactants (i.e., coco-betaine (CB) and cocoamidopropyl-betaine (CAPB)) have been studied. The bulk aggregation of the polyelectrolyte and the two surfactants was analyzed by turbidity [...] Read more.

The bulk and interfacial properties of solutions formed by a polycation (i.e., poly(diallyl-dimethylammonium chloride), PDADMAC) and two different zwitterionic surfactants (i.e., coco-betaine (CB) and cocoamidopropyl-betaine (CAPB)) have been studied. The bulk aggregation of the polyelectrolyte and the two surfactants was analyzed by turbidity and electrophoretic mobility measurements, and the adsorption of the solutions at the fluid interface was studied by surface tension and interfacial dilational rheology measurements. Evidence of polymer–surfactant complex formation in bulk was only found when the number of surfactant molecules was closer to the number of charged monomers in solutions, which suggests that the electrostatic repulsion associated with the presence of a positively charged group in the surfactant hinders the association between PDADMAC and the zwitterionic surfactant for concentrations in which there are no micelles in solution. This lack of interaction in bulk is reflected in the absence of an influence of the polyelectrolyte in the interfacial properties of the mixtures, with the behavior being controlled by the presence of surfactant. This work has evidenced the significant importance of the different interactions involved in the system for controlling the interaction and complexation mechanisms of in polyelectrolyte–surfactant mixtures. Full article

(This article belongs to the Special Issue Fluid Interfaces: From Colloids, Surfactants, Polymers and Nanoparticles to Their Mixtures)

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13 pages, 2539 KiB

Open AccessArticle

Specific Ion Effects of Dodecyl Sulfate Surfactants with Alkali Ions at the Air–Water Interface

by Eric Weißenborn and Björn Braunschweig

Molecules 2019, 24(16), 2911; https://doi.org/10.3390/molecules24162911 - 10 Aug 2019

Cited by 22 | Viewed by 4238

Abstract

The influence of Li⁺, Na⁺ and Cs⁺ cations on the surface excess and structure of dodecyl sulfate (DS⁻) anions at the air–water interface was investigated with the vibrational sum-frequency generation (SFG) and surface tensiometry. Particularly, we have [...] Read more.

The influence of Li⁺, Na⁺ and Cs⁺ cations on the surface excess and structure of dodecyl sulfate (DS⁻) anions at the air–water interface was investigated with the vibrational sum-frequency generation (SFG) and surface tensiometry. Particularly, we have addressed the change in amplitude and frequency of the symmetric S-O stretching vibrations as a function of electrolyte and DS⁻ concentration in the presence of Li⁺, Na⁺ and Cs⁺ cations. For the Li⁺ and Na⁺ ions, we show that the resonance frequency is shifted noticeably from 1055 cm⁻¹ to 1063 cm⁻¹ as a function of the surfactants’ surfaces excess, which we attribute to the vibrational Stark effect within the static electric field at the air–water interface. For Cs⁺ ions the resonance frequency is independent of the surfactant concentration with the S-O stretching band centered at 1063 cm⁻¹. This frequency is identical to the frequency at the maximum surface excess when Li⁺ and Na⁺ ions are present and points to the ion pair formation between the sulfate headgroup and Cs⁺ counterions, which reduces the local electric field. In addition, SFG experiments of the O-H stretching bands of interfacial H₂O molecules are used in order to calculate the apparent double layer potential and the degree of dissociation between the surfactant head group and the investigated cations. The latter was found to be 12.0%, 10.4% and 7.7% for lithium dodecyl sulfate (LiDS), sodium dodecyl sulfate (SDS) and cesium dodecyl sulfate (CsDS) surfactants, which is in agreement with Collins ‘rule of matching water affinities’. Full article

(This article belongs to the Special Issue Fluid Interfaces: From Colloids, Surfactants, Polymers and Nanoparticles to Their Mixtures)

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14 pages, 2181 KiB

Open AccessArticle

Concentration Effects in the Interaction of Monoclonal Antibodies (mAbs) with their Immediate Environment Characterized by EPR Spectroscopy

by Haleh H. Haeri, Jacob Blaffert, Florian A. Schöffmann, Michaela Blech, Josef Hartl, Patrick Garidel and Dariush Hinderberger

Molecules 2019, 24(14), 2528; https://doi.org/10.3390/molecules24142528 - 10 Jul 2019

Cited by 9 | Viewed by 3368

Abstract

Monoclonal antibodies (mAbs) are often needed and applied in high concentration solutions, >100 mg/mL. Due to close intermolecular distances between mAbs at high concentrations (~10–20 nm at 200 mg/mL), intermolecular interactions between mAbs and mAbs and solvent/co-solute molecules become non-negligible. Here, EPR spectroscopy [...] Read more.

Monoclonal antibodies (mAbs) are often needed and applied in high concentration solutions, >100 mg/mL. Due to close intermolecular distances between mAbs at high concentrations (~10–20 nm at 200 mg/mL), intermolecular interactions between mAbs and mAbs and solvent/co-solute molecules become non-negligible. Here, EPR spectroscopy is used to study the high-concentration solutions of mAbs and their effect on co-solvated small molecules, using EPR “spin probing” assay in aqueous and buffered solutions. Such, information regarding the surrounding environments of mAbs at high concentrations were obtained and comparisons between EPR-obtained micro-viscosities (rotational correlation times) and macroscopic viscosities measured by rheology were possible. In comparison with highly viscous systems like glycerol-water mixtures, it was found that up to concentrations of 50 mg/mL, the mAb-spin probe systems have similar trends in their macro- (rheology) and micro-viscosities (EPR), whereas at very high concentrations they deviate strongly. The charged spin probes sense an almost unchanged aqueous solution even at very high concentrations, which in turn indicates the existence of large solvent regions that despite their proximity to large mAbs essentially offer pure water reservoirs for co-solvated charged molecules. In contrast, in buffered solutions, amphiphilic spin probes like TEMPO interact with the mAb network, due to slight charge screening. The application of EPR spectroscopy in the present work has enabled us to observe and discriminate between electrostatic and hydrophobic kinds of interactions and depict the potential underlying mechanisms of network formation at high concentrations of mAbs. These findings could be of importance as well for the development of liquid-liquid phase separations often observed in highly concentrated protein solutions. Full article

(This article belongs to the Special Issue Fluid Interfaces: From Colloids, Surfactants, Polymers and Nanoparticles to Their Mixtures)

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Review

Jump to: Research

23 pages, 6978 KiB

Open AccessReview

Recent Advances in Studying Interfacial Adsorption of Bioengineered Monoclonal Antibodies

by Peter Hollowell, Zongyi Li, Xuzhi Hu, Sean Ruane, Cavan Kalonia, Christopher F. van der Walle and Jian R. Lu

Molecules 2020, 25(9), 2047; https://doi.org/10.3390/molecules25092047 - 28 Apr 2020

Cited by 21 | Viewed by 4738

Abstract

Monoclonal antibodies (mAbs) are an important class of biotherapeutics; as of 2020, dozens are commercialized medicines, over a hundred are in clinical trials, and many more are in preclinical developmental stages. Therapeutic mAbs are sequence modified from the wild type IgG isoforms to [...] Read more.

Monoclonal antibodies (mAbs) are an important class of biotherapeutics; as of 2020, dozens are commercialized medicines, over a hundred are in clinical trials, and many more are in preclinical developmental stages. Therapeutic mAbs are sequence modified from the wild type IgG isoforms to varying extents and can have different intrinsic structural stability. For chronic treatments in particular, high concentration (≥ 100 mg/mL) aqueous formulations are often preferred for at-home administration with a syringe-based device. MAbs, like any globular protein, are amphiphilic and readily adsorb to interfaces, potentially causing structural deformation and even unfolding. Desorption of structurally perturbed mAbs is often hypothesized to promote aggregation, potentially leading to the formation of subvisible particles and visible precipitates. Since mAbs are exposed to numerous interfaces during biomanufacturing, storage and administration, many studies have examined mAb adsorption to different interfaces under various mitigation strategies. This review examines recent published literature focusing on adsorption of bioengineered mAbs under well-defined solution and surface conditions. The focus of this review is on understanding adsorption features driven by distinct antibody domains and on recent advances in establishing model interfaces suitable for high resolution surface measurements. Our summary highlights the need to further understand the relationship between mAb interfacial adsorption and desorption, solution aggregation, and product instability during fill-finish, transport, storage and administration. Full article

(This article belongs to the Special Issue Fluid Interfaces: From Colloids, Surfactants, Polymers and Nanoparticles to Their Mixtures)

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