Langmuir (Langmuir)

Publisher: American Chemical Society, American Chemical Society

Journal description

Langmuir is devoted to reporting new and original experimental and theoretical research of interest to chemists and chemical physicists in the fields of surface and colloid chemistry. Coverage includes such topics as micelles, visicles, emulsions, gels, surfacants, colloids, crystal growth, nucleation, liquid crystals, imaging spectroscopy, electro-chemistry, biological colloids & interfaces, biopolymers, nanostructures, multicomponent systems, and materials. In addition to these structures, Langmuir also carries articles on theory, simulation, modeling and experimental developments. Along with national award-winning lectures, Langmuir regularly features letters, articles, reviews, commentaries, notes, and special issues.

Current impact factor: 4.46

Impact Factor Rankings

2016 Impact Factor Available summer 2017
2014 / 2015 Impact Factor 4.457
2013 Impact Factor 4.384
2012 Impact Factor 4.187
2011 Impact Factor 4.186
2010 Impact Factor 4.268
2009 Impact Factor 3.898
2008 Impact Factor 4.097
2007 Impact Factor 4.009
2006 Impact Factor 3.902
2005 Impact Factor 3.705
2004 Impact Factor 3.295
2003 Impact Factor 3.098
2002 Impact Factor 3.248
2001 Impact Factor 2.963
2000 Impact Factor 3.045
1999 Impact Factor 2.937
1998 Impact Factor 2.813
1997 Impact Factor 2.852
1996 Impact Factor 3.47
1995 Impact Factor 3.143
1994 Impact Factor 3.232
1993 Impact Factor 2.628
1992 Impact Factor 2.638

Impact factor over time

Impact factor
Year

Additional details

5-year impact 4.54
Cited half-life 7.20
Immediacy index 0.68
Eigenfactor 0.18
Article influence 1.10
Website Langmuir website
Other titles Langmuir (Online), Langmuir
ISSN 1520-5827
OCLC 39280622
Material type Document, Periodical, Internet resource
Document type Internet Resource, Computer File, Journal / Magazine / Newspaper

Publisher details

American Chemical Society

  • Pre-print
    • Author cannot archive a pre-print version
  • Restrictions
    • Must obtain written permission from Editor
    • Must not violate ACS ethical Guidelines
  • Post-print
    • Author cannot archive a post-print version
  • Restrictions
    • If mandated by funding agency or employer/ institution
    • If mandated to deposit before 12 months, must obtain waiver from Institution/Funding agency or use AuthorChoice
    • 12 months embargo
  • Conditions
    • On author's personal website, pre-print servers, institutional website, institutional repositories or subject repositories
    • Non-Commercial
    • Must be accompanied by set statement (see policy)
    • Must link to publisher version
    • Publisher's version/PDF cannot be used
    • If mandated sooner than 12 months, must obtain waiver from Editors or use AuthorChoice
    • Reviewed on 07/08/2014
  • Classification
    white

Publications in this journal

  • Ala' Al-Azizi · Andrew Draskovics · Giovanni Ramirez · Ali Erdemir · Seong H Kim
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    ABSTRACT: The effects of oxidation on wear of carbon/steel tribological interfaces were studied. When mechanical wear was small, the oxidation behavior of hydrogenated diamond-like carbon (H-DLC) and stainless steel (SS) sliding interface varied depending on the nature of the oxidizing environment. In dry air or oxygen, both H-DLC and SS wore readily. The wear debris of SS did not form iron oxide in dry air and oxygen. In humid nitrogen, however, the wear of H-DLC diminished with increasing humidity and the SS surface showed mild wear and iron oxide debris accumulated around the sliding contact region. These results revealed that different tribochemical reactions occur in dry oxygen and humid environments. In the absence of water, oxygen oxidizes the H-DLC surface making it susceptible to wear, creating debris and inducing wear on both H-DLC and SS. In contrast, adsorbed water molecules at less than 40% RH act as a molecular lubricant, while multi-water layers adsorbed at near-saturation act as electrolyte inducing electrochemical galvanic corrosion reactions on the SS. When hydrogen-free amorphous carbon (a-C) was used in tribo-tests, wear of the SS surface occurs, in addition to the tribochemical wear observed for H-DLC, due to the high hardness of the a-C film.
    No preview · Article · Feb 2016 · Langmuir
  • Sabina Maskey · J Matthew D Lane · Dvora Perahia · Gary S Grest
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    ABSTRACT: Polymers grafted onto nanoparticles have wide range of applications in electronic, optical and sensors fields. Here we present results for the chain conformation and structure of highly rigid di-substituted dialkyl poly para phenylene ethynylene (PPE) grafted on to 5 nm diameter silica nanoparticles as a function of solvent quality, molecular weight and coverage using molecular dynamics simulations. The conformation of PPEs determines the conjugation length and their assembly mode which in turn affects their electro-optical properties. In dilute solution, PPE chains are rigid and fully extended with an end-to-end distance which scales with the number of monomers independent of the solvent quality. In water which is a poor solvent for diethylhexyl PPE, the polymer chains grafted onto the nanoparticle aggregate into clusters which become more defined with increasing molecular weight and coverage. In toluene and decane, good solvents, the chains remain extended and do not aggregate. The distributions of the chains around the nanoparticle's core are homogeneous in good solvents whereas in poor solvents distributions are heterogeneous, independent of molecular weight and coverage.
    No preview · Article · Feb 2016 · Langmuir
  • James Sweeney · Grant Bruce Webber · Rob Atkin
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    ABSTRACT: The adsorbed layer conformation and lubricity of 35 kDa, 100 kDa and 300 kDa PEO adsorbed to ionic liquid (IL) - silica interfaces from 0.01 wt% solutions has been investigated using colloid probe atomic force microscopy. The ILs used were propylammonium nitrate (PAN) and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), which are protic and aprotic ILs, respectively. Normal force curves reveal steric interactions consistent with adsorbed polymer layers which are best fit using the mushroom model. Friction measurements show that the adsorbed polymer layer markedly reduces friction compared to surfaces sliding in the pure ILs, and that lubricity increases with polymer length. When polymer is adsorbed to the sliding surfaces friction is controlled by the the creation and disruption of intermolecular interactions between entangled chains, and the dragging of polymer chains through the interpenetration region. These experiments show that added polymer can reduce friction while maintaining the useful properties of ILs as lubricants.
    No preview · Article · Feb 2016 · Langmuir
  • Erica A Frankel · Philip C Bevilacqua · Christine D Keating
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    ABSTRACT: Phase separation of aqueous solutions containing polyelectrolytes can lead to formation of dense, solute-rich liquid droplets referred to as coacervates, surrounded by a dilute continuous phase of much larger volume. This type of liquid-liquid phase separation is thought to help explain the appearance of polyelectrolyte-rich intracellular droplets in the cytoplasm and nucleoplasm of extant biological cells, and may be relevant to protocellular compartmentalization of nucleic acids on the early Earth. Here we describe complex coacervates formed upon mixing the polycation poly(allylamine) (PAH, 15 kDa) with the anionic nucleotides adenosine 5' mono-, di-, and triphosphate (AMP, ADP, and ATP). Droplet formation was observed over a wide range of pH and MgCl2 concentrations. The nucleotides themselves as well as Mg2+ and RNA oligonucleotides were all extremely concentrated within the coacervates. Nucleotides present at just 2.5 mM in bulk solution had concentrations greater than 1 M inside the coacervate droplets. A solution with a total Mg2+ concentration of 10 mM had 1-5 M Mg2+ in the coacervates, and RNA random sequence (N54) partitioned ~10,000-fold into the coacervates. Coacervate droplets are thus rich in nucleotides, Mg2+, and RNA, providing a medium favorable for generating functional RNAs. Compartmentalization of nucleotides at high concentrations could have facilitated their polymerization to form oligonucleotides, which preferentially accumulate in the droplets. Locally high Mg2+ concentrations could have aided folding and catalysis in an RNA world, making coacervate droplets an appealing platform for exploring protocellular environments.
    No preview · Article · Feb 2016 · Langmuir
  • Tino Kirchhuebel · Marco Gruenewald · Falko Sojka · Satoshi Kera · Fabio Bussolotti · Takahiro Ueba · Nobuo Ueno · Gael Rouille · Roman Forker · Torsten Fritz
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    ABSTRACT: Tetraphenyldibenzoperiflanthene (DBP) is a promising candidate as a component of highly efficient organic photovoltaic cells and organic light emitting diodes. The structural properties of thin films of this particular lander-type molecule on Ag(111) were investigated by complementary techniques. Highly ordered structures were obtained and their mutual alignment characterized by means of low-energy electron diffraction (LEED). Scanning tunneling microscopy (STM) images reveal two slightly different arrangements within the first monolayer (ML), both describable as specific herringbone patterns with two molecules per unit cell whose dibenzoperiflanthene framework is parallel to the surface. In contrast, single DBP molecules in the second ML were imaged with much higher intramolecular resolution resembling the shape of the frontier orbitals in the gas phase, as calculated by means of density functional theory (DFT). Further deposition leads to the growth of highly ordered bilayer islands on top of the first ML with identical unit cell dimensions and orientation but slightly inclined molecules. This suggests that the first ML acts as a template for the epitaxial growth of further layers. Simultaneously, a significant number of second-layer molecules mainly located at step edges or scattered over narrow terraces does not form highly ordered aggregates.
    No preview · Article · Feb 2016 · Langmuir
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    ABSTRACT: A simple and green strategy is presented to decorate graphene with nanoparticles, based on laser ablation of targets in graphene auqeous solution. Ag and graphene oxide (GO) are chosen as model materials. The surface of GO sheets is strongly anchored with spherical Ag nanoparticles. The density and size of the Ag nanoparticles can be easily tuned by laser ablation conditions. Further, the GO sheets can be decorated with other nanoparticles from simple metals or semiconductors to multicomponent hybrids. Additionally, the Ag nanoparticle/GO sheet colloids can be utilized as blocks to build three-dimensional structures, such as sandwich membranes by evaporation-induced self-assembly. These graphene-based composite materials could be very useful in catalysis, sensors and nanodevices. Particularly, the Ag nanoparticle/GO sheet sandwich composite membranes exhibit excellent surface-enhanced Raman scattering performance and possess the huge potential in trace-detecting persistent organic pollutants in the environment.
    No preview · Article · Feb 2016 · Langmuir
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    ABSTRACT: Encapsulation of small molecules, proteins and other macromolecules within the protective water core of reverse micelles is emerging as a powerful strategy for a variety of applications. The cationic surfactant cetyl trimethylammonium bromide (CTAB) in combination with hexanol as a cosurfactant is particularly useful in the context of solution NMR spectroscopy of encapsulated proteins. Small angle x-ray and neutron scattering is employed to investigate the internal structure of the CTAB/hexanol reverse micelle particle under conditions appropriate for high resolution NMR spectroscopy. The scattering profiles are used to benchmark extensive molecular dynamics simulations of this reverse micelle system, and indicate that the parameters used in these simulations recapitulate experimental results. Shape distribution profiles and simulations indicate formation of homogeneous solutions of small approximately spherical reverse micelle particles at a water loading of 20 comprised of ~150 CTAB and 240 hexanol molecules. The 3000 waters comprising the reverse micelle core show a gradient of translational diffusion that reaches that of bulk water at the center. Rotational diffusion is slowed relative to bulk throughout the water core, with the greatest slowing near the CTAB head groups. The 5 Å thick interfacial region of the micelle consists of overlapping layers of Br- enriched water, CTAB head groups and hexanol hydroxyl groups, containing about one third of the total water. This study employs well-parameterized MD simulations, x-ray and neutron scattering, and electrostatic theory to illuminate fundamental properties of CTAB/hexanol reverse micelle size, shape, partitioning, and water behavior.
    No preview · Article · Feb 2016 · Langmuir
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    ABSTRACT: Injection of optimized chemistry water in enhanced oil recovery (EOR) has gained much interest in the last few years. Crude oil-water interfaces can have a viscoelastic character affected by the adsorption of amphiphilic molecules. The brine concentration as well as surfactants may strongly affect the fluid-fluid interfacial viscoelasticity. In this work we investigate interfacial viscoelasticity of two different oils in terms of brine concentration and a nonionic surfactant. We correlate these measurements with oil recovery in a glass-etched flow microchannel. Interfacial viscoelasticity develops relatively fast in both oils, stabilizes at about 48 hours. The interfaces are found to be more elastic than viscous. The interfacial elastic (G') and viscous (G") moduli increase as the salt concentration decreases until a maximum in viscoelasticity is observed around 0.01% wt. of salt. Monovalent (Na+) and divalent (Mg2+) cations are used to investigate the effect of ion type; no difference is observed at low salinity. The introduction of a small amount of a surfactant (100 ppm) increases the elasticity of the crude oil - water interface at high salt concentration. Aqueous solutions, that give the maximum interface viscoelasticity, and high salinity brines are used to displace oil in a glass-etched "porous media" micromodel. Pressure fluctuations after breakthrough are observed in systems with high salt concentration while at low salt concentration there are no appreciable pressure fluctuations. Oil recovery increases by 5-10% in low salinity brines. By using a small amount of a nonionic surfactant with high salinity brine, oil recovery is enhanced 10% with no pressure fluctuations. Interface elasticity reduces the snap-off of the oil phase leading to higher oil recovery from water injection. This study sheds light on significance of interface viscoelasticity in oil recovery by change in salt concentration and by addition of small amount of a nonionic surfactant.
    No preview · Article · Feb 2016 · Langmuir
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    ABSTRACT: Crystallization of polyethylene oxide (PEO)-sodium iodine (NaI) composites is investigated by differential scanning calorimetry (DSC), extensional rheology and in-situ small angle X-ray scattering (SAXS), aiming to demonstrate versatile roles played by polymer-ion interaction. In the isothermal quiescent crystallization process, the decrease of crystal growth rate is observed for PEO-NaI and is attributed to slow chain movement caused by coordination between cations and polymer. In-situ SAXS on extensional flow-induced-crystallization (FIC) shows enhanced kinetics and orientation for both PEO and PEO-NaI with increasing strain rate. However an overall weaker strain-rate dependence of FIC is observed for PEO-NaI, which can be interpreted as a synergistic consequence of promoted nucleation under flow and impeded crystal growth by polymer-ion interaction. A possible microscopic mechanism is proposed to account for the experimental observation based on the formation of transient cross-linking points in PEO-NaI and their influences on the entanglement network of polymer under various flow fields. The disclosed strain-rate dependence and various ion effects on behaviors of PEO-salt composites contribute to a comprehensive understanding of polymer-ion solid polyelectrolytes.
    No preview · Article · Jan 2016 · Langmuir
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    ABSTRACT: The interaction of electrospun mats with water is critical for many possible applications, and the water contact angle on the surface is the parameter usually measured to characterize wetting. Although useful for hydrophobic surfaces, this approach is limited for hydrophilic mats, where wicking has also to be considered. In this case, it is still unclear how the fiber surface chemical composition and morphology will affect the wetting behavior of electrospun mats. In this work, wetting was studied with different hydrophilic membranes produced by blending thermoplastic elastomer SEBS with amphiphilic PEO-PPO-PEO molecules. Three different types of PEO-PPO-PEO, with different molar masses, PEO content and physical form were used. The effect of these differences on the wetting behavior of the electrospun mats was evaluated by contact angle goniometry, wicking measurements and different imaging techniques. X-ray photoelectron spectroscopy was used to characterize the surface chemical composition. The smaller molecules quickly saturated the surface at low concentrations, making the mats hydrophilic. The sheath of PEO-PPO-PEO also resulted in fast absorption of water, when comparing the saturated and non-saturated surfaces. Longer PEO chain-ends seemed to hinder complete segregation and also led to a higher activation time when in contact with water. Liquid PEO-PPO-PEO was easily leached by water.
    No preview · Article · Jan 2016 · Langmuir
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    ABSTRACT: We present an in-situ structural study of the surface behaviour of PS-b-PAA monolayers at the air/water interface at pH 2, for which the PAA blocks are neutral and using DMF as spreading solvent. The surface pressure versus molecular area isotherm shows a perfectly reversible pseudo-plateau over several cycles of compression/decompression. The width of such plateau enlarges when increasing temperature, conversely to what is classically observed in case of an in-plane 1st order transition. We combined SNR experiments with contrast variation to solve the profile of each block perpendicular to the surface with GISAXS measurements to determine the in-plane structure of the layer. SNR experiments showed that both PS and PAA blocks remain adsorbed on the surface for all surface pressure probed. A correlation peak at Qxy* = 0.021 Å-1 is evidenced by GISAXS at very low surface pressure which intensity first increases on the plateau. When compressing further, its intensity decays while Qxy* is shifted towards low Qxy. The peak fully disappears at the end of the plateau. These results are interpreted by the formation of surface aggregates induced by DMF molecules at the surface. These DMF molecules remain adsorbed within the PS core of the aggregates. Upon compression, they are progressively expelled from the monolayer, which gives rise to the pseudo-plateau on the isotherm. The intensity of the GISAXS correlation peak is set by the amount of DMF within the monolayer as it vanishes when all DMF molecules are expelled. This result emphizes the role of the solvent in Langmuir monolayer formed by amphiphilic copolymers which hydrophobic and hydrophilic parts are composed by long polymer chains.
    No preview · Article · Jan 2016 · Langmuir
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    ABSTRACT: Despite extensive studies on the folding and function of cytochrome c, the mechanisms underlying its aggregation remain largely unknown. We herein examined the aggregation behavior of the physiologically relevant two types of cytochrome c, metal-bound cytochrome c, and its fragment with high amyloidogenicity as predicted in alcohol/water mixtures. Although the aggregation propensity of holo cytochrome c was low due to high solubility, markedly unfolded apo cytochrome c, lacking the heme prosthetic group, strongly promoted the propensity for amorphous aggregation with increases in hydrophobicity. Silver-bound apo cytochrome c increased the capacity of fibrillar aggregation (i.e., protofibrils or immature fibrils) due to subtle structural changes of apo cytochrome c by strong binding of silver. However, mature amyloid fibrils were not detected for any of the cytochrome c variants or its fragment, even with extensive ultrasonication, which is a powerful amyloid inducer. These results revealed the intrinsically low amyloidogenicity of cytochrome c, which is beneficial for its homeostasis and function by facilitating the folding and minimizing irreversible amyloid formation. We propose that intrinsically low amyloidogenicity of cytochrome c is attributed to the low metastability of supersaturation. The phase diagram constructed based on solubility and aggregate type is useful for a comprehensive understanding of protein aggregation. Furthermore, amorphous aggregation, which is also viewed as a generic property of proteins, and amyloid fibrillation can be distinguished from each other by the metastability of supersaturation.
    No preview · Article · Jan 2016 · Langmuir
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    ABSTRACT: In this manuscript we describe the formation of functional honeycomb-like porous surfaces fabricated by the breath figures technique using blends of either amino-terminated poly(styrene) or a poly(styrene)-b-poly(acrylic acid) block copolymer with homopoly(styrene). Thus, the porous interfaces exhibited either amino or acid groups selectively located inside of the holes, which were subsequently employed to anchor stimuli-responsive nanogels by electrostatic interactions. These nanogels were prepared from poly(N-isopropylacrylamide) (PNIPAM) crosslinked with dendritic polyglycerol (dPG) and semi-interpenetrated with either 2-(dimethylamino)ethyl methacrylate (DMAEMA) or 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) to produce positively and negatively charged nanogel surfaces, respectively. The immobilization of these semi-interpenetrated networks onto the surfaces allowed us to have unique stimuli-responsive surfaces with both controlled topography and composition. More interestingly, the surfaces exhibited stimuli-responsive behavior by variations on the pH or temperature. Finally, the surfaces were evaluated regarding their capacity to induce a thermally-triggered protein release at temperatures above the cloud point temperature (Tcp) of the nanogels.
    No preview · Article · Jan 2016 · Langmuir
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    ABSTRACT: Anaerobic fermentation can transform carbohydrates to yield a multicomponent mixture comprising mainly of acetone, 1-butanol, and ethanol (ABE) in a typical weight ratio of 3:6:1. Compared to ethanol, 1-butanol, the main product of ABE fermentation, offers significant advantages as a biofuel or a fuel-additive. However, the toxicity of 1-butanol for cell cultures requires broth concentrations to be low in 1-butanol (approximately 1 - 2 wt%). An energy efficient recovery method that performs well even at low 1-butanol concentrations is therefore necessary to ensure economic feasibility of the ABE fermentation process. In this work, configurational-bias Monte Carlo simulations in the Gibbs ensemble are performed to probe the adsorption of 1-butanol/water solutions onto all-siliceous zeolites with the framework types MFI and FER. At low solution concentration, the selectivity and capacity for 1-butanol in MFI are larger than those in FER, while the opposite is true for concentrations at or above those of ABE broths. Structural analysis at various loadings sheds light on the different sorbate--sorbate and sorbate--sorbent interactions that govern trends in adsorption in each zeolite.
    No preview · Article · Jan 2016 · Langmuir
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    ABSTRACT: The site-specific immobilization of histidine-tagged proteins to patterns formed by far-field and near-field exposure of films of aminosilanes with protein-resistant photolabile protecting groups is demonstrated. After deprotection of the aminosilane, either through a mask or using a scanning near-field optical microscope, the amine terminal groups are derivatized first with glutaraldehyde and then with N-(5-amino-1-carboxypentyl)iminodiacetic acid to yield a nitrilo triacetic acid (NTA) terminated surface. After complexation with Ni2+, this surface binds histidine-tagged GFP and CpcA-PEB in a site-specific fashion. The chemistry is simple and reliable, and leads to extensive surface functionalization. Bright fluorescence is observed in fluorescence microscopy images of micrometer- and nanometer-scale patterns. X-ray photoelectron spectroscopy is used to study quantitatively the efficiency of photodeprotection and the reactivity of the modified surfaces. The efficiency of the protein binding process is investigated quantitatively by ellipsometry and by fluorescence microscopy. We find that regions of the surface not exposed to UV light bind negligible amounts of His-tagged proteins, indicating that the oligo(ethylene glycol) adduct on the nitrophenyl protecting group confers excellent protein resistance; in contrast, exposed regions bind His-GFP very effectively, yielding strong fluorescence that is almost completely removed on treatment of the surface with imidazole, confirming a degree of site-specific binding in excess of 90%. This simple strategy offers a versatile generic route to the spatially selective site-specific immobilization of proteins at surfaces.
    No preview · Article · Jan 2016 · Langmuir
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    ABSTRACT: Medical ultrasound imaging often employs ultrasound contrast agents (UCAs), injectable microbubbles stabilized by shells or membranes. In tissue, the compressible gas cores can strongly scatter acoustic signals, resonate, and emit harmonics. However, bubbles generated by conventional methods have nonuniform sizes, reducing the fraction that resonates with a given transducer. Microfluidic flow-focusing is an alternative production method which generates highly monodisperse bubbles with uniform constituents, enabling more-efficient contrast enhancement than current UCAs. Production size is tunable by adjusting gas pressure and solution flow rate, but solution effects on downstream stable size and lifetime have not been closely examined. This study therefore investigated several solution parameters, including DSPC:DSPE-PEG2000 lipid ratio, concentration, viscosity, and preparation temperature to determine their effects on stabilization. It was found that bubble lifetime roughly correlated with stable size, which in turn was strongly influenced by primary-lipid-to-emulsifier ratio, analogous to its effects on conventional bubble yield and Langmuir-trough compressibility in existing studies. Raising DSPE-PEG2000 fraction in solution reduced bubble surface area in proportion to its reduction of lipid packing density at low compression in literature. In addition, surface area was found to increase proportionately with lipid concentration above 2.1 mM. On the other hand, viscosities above or below 2.3-3.3 mPa·s seemed to reduce bubble size. Finally, lipid preparation at room temperature led to smaller bubbles compared to preparation near or above the primary lipid's phase transition point. Understanding these effects will further improve on post-formation control over microfluidic bubble production, and facilitate size-tuning for optimal contrast enhancement.
    No preview · Article · Jan 2016 · Langmuir
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    ABSTRACT: A long chain amino acid containing dipeptide has been found to form a hydrogel in phosphate buffer whose pH ranges from 6.0-8.8. The hydrogel formed at pH 7.46 has been characterized by small angle X-ray scattering (SAXS), wide angle powder X-ray diffraction (PXRD), FT-IR, field emission scanning electron microscopic (FE-SEM), high-resolution transmission electron microscopic (HR-TEM) imaging and rheological analyses. The microscopic imaging studies suggest the formation of a nanofibrillar 3D network for the hydrogel. As observed visually and confirmed rheologically, the hydrogel at pH 7.46 exhibits thixotropy. This thixotropic property can be exploited to inject the peptide. Furthermore, the hydrogel exhibits remarkable antibacterial activity against Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa which are responsible for many common diseases. The hydrogel has potential applications due to biocompatibility with human red blood cells and human fibroblast cells. Interestingly, this hydrogel shows high resistance towards proteolytic enzymes making it a new potential antimicrobial agent for future applications. It has also been observed that a small change in molecular structure of the gelator peptide not only turns the gelator into a non-gelator molecule under similar conditions but also has a significant negative impact on its bactericidal character.
    No preview · Article · Jan 2016 · Langmuir
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    ABSTRACT: We demonstrate that the lamella-forming polystyrene-block-poly(N-methyl-4-vinyl pyridinium iodine) (PS-b-P4VPQ), with similar sizes of the PS and P4VPQ blocks, can be dispersed in the aqueous solutions by forming lipid/PS-P4VPQ multilamellae. Using small-angle neutron scattering (SANS) and 1,2-dipalmitoyl-d62-sn-glycero-3-phosphocholine (d62-DPPC) in D2O, a broad correlation peak is found in the scattering profile that signifies the formation of the loosely ordered d62-DPPC/PS-b-P4VPQ multilamellae . The thicknesses of the hydrophobic and hydrophilic layers of the d62-DPPC/PS-b-P4VPQ multilamellae are close to the PS layer and the condensed brush layer thicknesses as determined from previous neutron reflectometry studies on the PS-b-P4VPQ monolayer at the air-water interface. Such well dispersed d62-DPPC/PS-b-P4VPQ multilamellae are capable of forming multilamellae with DNA in aqueous solution. It is found that the encapsulation of DNA in the hydrophilic layer of the d62-DPPC/PS-b-P4VPQ multilamellae slightly increases the thickness of the hydrophilic layer. Adding CaCl2 can enhance the DNA adsorption in the hydrophilic brush layer and it is similar to that observed in the neutron reflectometry study of the DNA adsorption by the PS-b-P4VPQ monolayer.
    No preview · Article · Jan 2016 · Langmuir
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    ABSTRACT: Microfluidics offers unique characteristics to control the mixing of liquids under laminar flow. Its use for the assembly of lipoplexes represents an attractive alternative for the translation of gene delivery studies into clinical trials on a sufficient throughput scale. Here, it was shown that the microfluidic assembly of pDNA/cationic liposome (CL) lipoplexes allows the formation of nanocarriers with enhanced transfection efficiencies compared with the conventional bulk-mixing (BM) process under high pDNA loading conditions. Lipoplexes generated by microfluidic devices exhibit smaller and more homogeneous structures at a molar charge ratio (R±) of 1.5, representing the ratio of lipid to pDNA content. Using an optimized model to fit small-angle X-ray scattering (SAXS) curves, it was observed that large amounts of pDNA induces the formation of aggregates with a higher number of stacked bilayers (N~5) when was used the BM process, whereas microfluidic lipoplexes presented smaller structures with a lower number of stacked bilayers (N~2.5). In vitro studies further confirmed that microfluidic lipoplexes achieved higher in vitro transfection efficiencies in prostate cancer cells at R± 1.5, employing a reduced amount of cationic lipid. The correlation of mesoscopic characteristics with in vitro performance provides insights for the elucidation of the colloidal arrangement and biological behavior of pDNA/CL lipoplexes obtained by different processes, highlighting the feasibility of applying microfluidics to gene delivery.
    No preview · Article · Jan 2016 · Langmuir
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    ABSTRACT: Lubricin is a glycoprotein found in articular joints which has been long recognized as being an important biological boundary lubricant molecule and, more recently, and impressive anti-adhesive that readily self-assembles into a well ordered, polymer brush layer on virtually any substrate. The lubricin molecule possesses an overabundance of anionic charge, a property that is atypical among anti-adhesive molecules, that enables its use as a coating for applications involving electrokinetic processes such as electrophoresis and electroosmosis. Coating the surfaces of silica and polymeric microfluidic devices with self-assembled lubricin coatings affords a unique combination of excellent fouling resistance and high charge density that enables notoriously 'sticky' biomolecules such as proteins to be used and controlled electrokinetically in the device without complications arising from non-specific adsorption. Using capillary electrophoresis, we characterized the stability, uniformity, and electrokinetic properties of lubricin coatings applied to silica and PTFE capillaries over a range of run buffer pHs and when exposed to concentrated solutions of protein. In addition, we demonstrate the effectiveness of lubricin as a coating to minimize non-specific protein adsorption in an electrokinetically controlled polydimethyl siloxane/silica microfluidic device.
    No preview · Article · Jan 2016 · Langmuir