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A letter to the editor comments on a clinical study titled "Lipid emulsion therapy during the management of the critically-ill poisoned patient: a prospective cohort study." The study found that survival after lipid emulsion administration in patients intoxicated with various drugs is not correlated with drug lipophilicity. The letter argues that the study's use of the logarithm of the octanol/water partition coefficient (log P) as a measure of lipophilicity may not be accurate, and suggests that the logarithm of the distribution coefficient (log D) is a more reasonable descriptor. The letter also discusses the concept of a "lipid sink" and suggests that the increase in systolic blood pressure observed with lipid emulsion therapy may be due to a direct inhibitory effect on endothelial nitric oxide release. [Extracted from the article]

• Major FFF approaches since 2012 for selected biomacromolecules are demonstrated. • Special attention is given for biomacromolecule fractionation, isolation, and purification. • Fragile structural integrity of biomacromolecules is preserved by field-flow fractionation. • AF4 (AsFlFFF) is the most dominant technique in the biomacromolecule studies. • Great possibility to collect fractions of complex samples for further analysis. Field-flow fractionation (FFF) with its several variants, has developed into a mature methodology. The scope of the FFF investigations has expanded, covering both a wide range of basic studies and especially a wide range of analytical applications. Special attention of this review is given to the achievements of FFF with reference to recent applications in the fractionation, isolation, and purification of biomacromolecules, and from which especially those of (in alphabetical order) bacteria, cells, extracellular vesicles, liposomes, lipoproteins, nucleic acids, and viruses and virus-like particles. In evaluating the major approaches and trends demonstrated since 2012, the most significant biomacromolecule applications are compiled in tables. It is also evident that asymmetrical flow field-flow fractionation is by far the most dominant technique in the studies. The industry has also shown current interest in FFF and adopted it in some sophisticated fields. FFF, in combination with appropriate detectors, handles biomacromolecules in open channel in a gentle way due to the lack of shear forces and unwanted interactions caused by the stationary phase present in chromatography. In addition, in isolation and purification of biomacromolecules quite high yields can be achieved under optimal conditions. [ABSTRACT FROM AUTHOR]

• Capillary electromigration techniques relevant for lipid membrane/β-blocker studies. • Unilamellar vesicles are preferred in liposome electrokinetic chromatography. • New stationary phases for immobilized artificial chromatography are needed. • PC is the most common phospholipid in lipid membrane/β-blocker interaction studies. • Propranolol has been the most studied β-blockers in lipid membrane studies. β-Blockers belong to a frequently used class of drugs primarily used to treat heart and circulatory conditions. Here we describe the use of lipid vesicles and liposomes as cell membrane biomimicking models in capillary electromigration (CE) and liquid chromatography (LC) techniques for the investigation of interactions between lipid membranes and β-blockers. In addition to liposomes, the use of commercial intravenous lipid emulsions, and their interactions with β-blockers are also discussed. Different CE and LC instrumental techniques designed for these purposes are introduced. Other methodologies for studying interactions between β-blockers and lipid membranes are also briefly discussed, and the different methodologies are compared. The aim is to give the reader a good overview on the status of the use of liposomes and lipids in CE and LC for studying β-blocker interactions. [ABSTRACT FROM AUTHOR]

Abstract: The reassembly of the S-layer protein SlpA of Lactobacillus brevis ATCC 8287 on positively charged liposomes was studied by small angle X-ray scattering (SAXS) and zeta potential measurements. SlpA was reassembled on unilamellar liposomes consisting of 1-palmitoyl-2-oleyl-sn-glycero-3-phosphocholine and 1,2-dioleoyl-3-trimethylammonium-propane, prepared by extrusion through membranes with pore sizes of 50nm and 100nm. Similarly extruded samples without SlpA were used as a reference. The SlpA-containing samples showed clear diffraction peaks in their SAXS intensities. The lattice constants were calculated from the diffraction pattern and compared to those determined for SlpA on native cell wall fragments. Lattice constants for SlpA reassembled on liposomes (a =9.29nm, b =8.03nm, and γ =84.9°) showed a marked change in the lattice constants b and γ when compared to those determined for SlpA on native cell wall fragments (a =9.41nm, b =6.48nm, and γ =77.0°). The latter are in good agreement with values previously determined by electron microscopy. This indicates that the structure formed by SlpA is stable on the bacterial cell wall, but SlpA reassembles into a different structure on cationic liposomes. From the (10) reflection, the lower limit of crystallite size of SlpA on liposomes was determined to be 92nm, corresponding to approximately ten aligned lattice planes. [Copyright &y& Elsevier]

Gold nanoparticles ( GNPs) are popular colloidal substrates in various sensor, imaging, and nanomedicine applications. In separation science, they have raised some interest as a support for sample preparation. Reasons for their popularity are their low cost, ability for size-controlled synthesis with well-defined narrow nanoparticle size distributions, as well as straightforward surface functionalization by self-assembling (thiol-containing) molecules on the surface, which allows flexible introduction of functionalities for the selective capture of analytes. Most commonly, the method of first choice for size determination is dynamic light scattering ( DLS). However, DLS has some serious shortcomings, and results from DLS may be misleading. For this reason, in this contribution several distinct complementary nanoparticle sizing methodologies were utilized and compared to characterize citrate-capped GNPs of different diameters in the range of 13-26 nm. Weaknesses and strengths of DLS, transmission electron microscopy, asymmetrical-flow field-flow fractionation and nanoelectrospray gas-phase electrophoretic mobility molecular analysis are discussed and the results comparatively assessed. Furthermore, the distinct GNPs were characterized by measuring their zeta-potential and surface plasmon resonance spectra. Overall, the combination of methods for GNP characterization gives a more realistic and comprehensive picture of their real physicochemical properties, (hydrodynamic) diameter, and size distribution. [ABSTRACT FROM AUTHOR]

CE has matured into a well-known and much used separation technique, with applications covering more or less all types of samples. EKC, which originally was developed for the separation of uncharged compounds, is still today under much development, with main focus on finding the perfect or ideal carriers (pseudo-stationary phase) for a broad range of analytes. In this review, the use of lipid dispersions as pseudostationary phases in EKC performed in capillaries and microchips, in addition to CE frontal analysis and partial filling EKC using lipid dispersions is discussed. Various types of lipid dispersions including liposomes, PEG-stabilized aggregates, proteoliposomes, lipid-based nanoparticles, and commercial lipid emulsions are described. The purpose of the review is to give the reader an overview of how EKC, CE frontal analysis, and partial filling EKC, have been applied to the study of interactions between analytes and lipid membranes. [ABSTRACT FROM AUTHOR]

Abstract: Silica particles were covalently modified with phospholipids and used as packing material for nano-liquid chromatography (nano-LC). This modification involved aminopropylsilylation of the raw silica particles using 3-(aminopropyl)-triethoxysilane, covalent binding of glutaraldehyde molecules to the aminopropylsilylated particles, and finally covalent binding of different phospholipid vesicles containing primary amino groups to the iminoaldehyde silica particles. Capillaries with an inner diameter of 100μm were packed with phospholipid-coated silica particles using a slurry packing method. The packed capillaries were tested in nano-LC with UV-detection for the separation of acidic, neutral, and basic model analytes. The effect of the buffer ion on the retention factor of the analytes was evaluated using buffer solutions with constant ionic strength and pH. In addition, the effect of the volume of methanol in the mobile phase was studied. The calculated distribution coefficients (log K D) of the model compounds were in agreement with those reported in the literature. A good correlation between log K D values and octanol/water partitioning coefficients (P o/w) for neutral hydrophobic analytes was obtained proving the applicability of the method for predicting partitioning of the compounds with the biomembranes. [Copyright &y& Elsevier]

Abstract: In this work we elucidated the applicability of phosphonium-based ionic liquids (ILs) as pseudostationary phase in electrokinetic capillary chromatography (EKC) with UV-detection. The phosphonium ILs studied contain bromide, chlorine, or tosylate ions, as counter ions, and alkyl side chains of variable length on the phosphorous atom. The effects of the type and concentration of the IL, pH, ionic strength, and type of background electrolyte solution on the electroosmotic flow (EOF) and on the effective electrophoretic mobilities of some neutral model analytes were investigated and large variations in the migration times were observed. Especially the IL employed remarkably affected the strength and direction of the EOF Successful separations were obtained for neutral aromatic singly substituted analytes, namely benzene, toluene, phenol, and nitrobenzene. The results demonstrated the potential of capillary electromigration methods for rapid interaction studies between ILs and analytes, which is useful for the development of novel materials for sample preparation and separation purposes or for novel catalyst and chemical processing studies. [Copyright &y& Elsevier]

Abstract: The need for novel packing materials in both capillary electrochromatography (CEC) and capillary liquid chromatography (CLC) is apparent and the development towards more selective, application-oriented chromatographic phases is under progress world-wide. In this study we have synthesized new polyethyleneimine (PEI) functionalized Mn2O3, SiO2, SnO2, and ZrO2 particles for the fabrication of packed capillary columns for CEC and CLC. The nanocasting approach was successful for the preparation of functionalized metal oxide materials with a controlled porosity and morphology. PEI functionalization was done using ethyleneimine monomers to create particles which are positively charged in aqueous solution below pH 9. This functionalization allowed the possibility to have both hydrophobic (due to its alkyl chain) and ionic interactions (due to positively charged amino groups) with selected compounds. For comparison aminopropyl-functionalized silica was also synthesized and tested. Both slurry pressure and electrokinetic packing procedures used gave similar results, but fast sedimentation of the material caused some problems during the packing. The high stability and wide pH range of PEI-functionalized SiO2 material, with potential for hydrophobic and electrostatic interactions, proved to be useful for the CEC and CLC separation of some model acidic and neutral compounds. [Copyright &y& Elsevier]

Abstract: The use of asymmetrical flow field-flow fractionation (AsFlFFF) in the study of heat-induced aggregation of proteins is demonstrated with bovine serum albumin (BSA) as a model analyte. The hydrodynamic diameter (d h), the molar mass of heat-induced aggregates, and the radius of gyration (R g) were calculated in order to get more detailed understanding of the conformational changes of BSA upon heating. The hydrodynamic diameter of native BSA at ambient temperature was ∼7nm. The particle size was relatively stable up to 60°C; above 63°C, however, BSA underwent aggregation (growth of hydrodynamic diameter). The hydrodynamic diameters of the aggregated particles, heated to 80°C, ranged from 15 to 149nm depending on the BSA concentration, duration of incubation, and the ionic strength of the solvent. Heating of BSA in the presence of sodium dodecyl sulfate (1.7 or 17mM) did not lead to aggregation. The heat-induced aggregates were characterized in terms of their molar mass and particle size together with their respective distributions with a hyphenated technique consisting of an asymmetrical field-flow fractionation device and a multi-angle light scattering detector and a UV-detector. The carrier solution comprised 8.5mM phosphate and 150mM sodium chloride at pH 7.4. The weight-average molar mass (M w) of native BSA at ambient temperature is 6.6×104 gmol−1. Incubation of solutions with BSA concentrations of 1.0 and 2.5mgmL−1 at 80°C for 1h resulted in aggregates with M w 1.2×106 and 1.9×106 gmol−1, respectively. The average radius of gyration and the average hydrodynamic radius of the heat-induced aggregate samples were calculated and compared to the values obtained from the size distributions measured by AsFlFFF. For comparison static light scattering measurements were carried out and the corresponding average molar mass distributions of solutions with BSA concentrations of 1.0 and 2.5mgmL−1 at 80°C for 1h gave aggregates with M w 1.7×106 and 3.5×106 gmol−1, respectively. [Copyright &y& Elsevier]

Abstract: A phospholipid–bovine serum albumin (BSA) coating was developed for chiral capillary electrochromatographic separation of d- and l-tryptophan. Temperature, liposome composition, and liposome–BSA mixing and extrusion were found to have critical effects on the chiral separation of d- and l-tryptophan in terms of resolution, separation efficiency, and migration times. A solution of 0.5mM phosphatidylcholine (PC)–1 mg/ml BSA performed better than a solution of 0.5mM PC/phosphatidylserine (PS) (80:20, mol%)–1 mg/ml BSA as capillary coating; baseline separation of the enantiomers with satisfactory resolution was then achieved. Temperature played a crucial role in the chiral separation, as demonstrated for phospholipid-coated capillaries immobilized with BSA and lysozyme. The d- and l-tryptophans showed a marked difference in separation efficiency on the PC–BSA-coated capillary; the theoretical plate number of l-tryptophan was above 500,000m−1, whereas that of d-tryptophan was only about 22,000m−1. Immobilized BSA (pI 4.7) showed better chiral separation selectivity for the enantiomers than did immobilized lysozyme (pI 10.5), α-chymotrypsin (pI 8.1–8.3), or avidin (pI 10.0–10.5); also resolution was better and analysis time was faster. Hydrophobic interactions played an important role in the BSA-immobilized phospholipid-coated capillaries. The importance of protein net charge and molar mass for its immobilization in phospholipid-coated capillaries is discussed. [Copyright &y& Elsevier]

A novel, comprehensive two-dimensional asymmetric field-flow fractionation-liquid chromatographic system is described (AsF1FFF-RPLC). The interface is based on a switching valve, and the whole sample is analyzed in both dimensions. The system proved to be repeatable and quantitative in the characterization of egg white proteins. Four peaks at 4, 5.5-6.0, 7.5-8.0, and 10.0-11.0 nm, and corresponding to lysozyme, ovalbumin, transferrin, and a dimer of transferrin, were obtained in the AsFIFFF first-dimension system. Lysozyme also produced an additional peak, which overlapped with ovalbumin. Twelve compounds were separated in the LC second-dimension system. Identifications were made with the help of standards (ovalbumin, ovotransferrin, lysozyme) and by comparison of the peak areas, particle sizes, and retention data with values given in the literature. The effect of heat on egg white denaturation was studied, and the unfolding of peptide bonds of the protein was found to be pronounced when the sample was heated in phosphate solution. [ABSTRACT FROM AUTHOR]

Low-density lipoprotein (LDL) particles were immobilized on the inner wall of a fused-silica capillary and used in a study of the interactions between LDL and neutral drugs in electrochromatography. The effect of coating parameters (pH, ionic strength of the coating solution, duration of the coating procedure) on the properties and stability of the coating was examined. The stability of the coating was highest when the pH of the coating solution was under the pa value of the LDL particles. Interactions of unmodified LDL coatings with drugs were compared with those of acetylated LDL coatings. Acetylation of LDL neutralizes the positive charge on the lysine residues of the protein component of LDL particles, and acetylated LDL was used as a reference to examine the effect of the positively charged amino acids in the unmodified coating. Under similar coating conditions, acetylated LDL coating yielded stronger EOF evidently due to the decreased number of positive charges on LDL particles. The interactions of the unmodified and acetylated LDL coatings with steroids aldosterone, testosterone, and progesterone were comparable, which indicates that the density of immobilized LDL particles is not appreciably altered by acetylation. As expected, the strength of the interactions between steroids and the LDL coating increased with hydrophobicity of the drug. [ABSTRACT FROM AUTHOR]

Divalent cations affect the stability and structure of phospholipid vesicles and also the binding and immobilization of proteins into phospholipid membranes. The effect of calcium, magnesium, and zinc on zwitterionic phosphatidylcholine (PC) coatings in fused silica capillaries for electrophoresis was the primary interest in this work. In addition, the effect of temperature on the coating stability was investigated by coating 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes at temperatures above and below the gel- to fluid-state transition. All coatings were performed with PC large unilamellar vesicles (LUV) in 40mM N-(2-hydroxyethyl)piperazine-N′-(2-ethanesulfonic acid) (HEPES) at pH 7.4 as basic solution. HEPES (40mM) at pH 7.4 was used as background electrolyte (BGE) throughout the study. The stability of the coating was studied by measuring the electroosmotic flow. A molar ratio of 1:3PC/Ca2+ or PC/Mg2+ gave the best coating stability owing to the increased rigidity of the phospholipid membrane furnished by the divalent metal ions. Better results were obtained with DPPC in the more rigid gel state than in the fluid state: the electroosmotic flow was much suppressed and the PC coating was stabilized. Coating the fused silica capillary with PC liposome–metal ion buffer solutions resulted in good electrophoretic separation of basic model proteins (pI-values 7.8–11.0). The electrophoretic results demonstrate the importance of stabilizing the phospholipid coating on fused silica capillaries, either by the addition of divalent metal ions (Ca2+, Mg2+, or Zn2+) or by working in the gel-state region of the phospholipid. [Copyright &y& Elsevier]

The structural resemblance of liposomes to natural cell membranes has caused them to be employed in liquid chromatographic and capillary electromigration techniques to study the interactions between analytes and phospholipid membranes. Phospholipids and liposomes are immobilized in stationary phases for liquid chromatography by a variety of techniques, to which we give special attention. We present selected applications to the separation of analytes. Though still few, applications in capillary electromigration are particularly attractive because of the small amounts of liposomes and samples that are required. We demonstrate the promising use of liposomes as carriers and coating materials in capillary electrophoresis with reference to recent applications. We note future directions for the utilization of phospholipids and liposomes in liquid chromatographic and capillary electromigration techniques. [Copyright &y& Elsevier]

The effect of calcium on phospholipid coatings in fused silica capillaries used in capillary electrophoresis was studied. The anionic liposomes used for the coating consisted of 3 mM 1-palmitoyl-2-oleyl-sn-glycero-3-phosphatidylcholine and phosphatidylserine in the ratio 80/20 mol%. Coating was performed as part of the preconditioning, and the capillaries could be used for several runs without the need for liposomes in the background electrolyte solution or for liposome rinses between runs. Phospholipids could easily be flushed away by rinsing with a chloroform-methanol (2:1 v/v) mixture, which made it possible to recoat and reuse the capillaries. A calcium:phospholipid ratio of approximately 3 gave the most stable coating. The stability of the coating and success of the coating procedure were studied by measuring the electroosmotic flow and by separating uncharged steroids, which were used as model compounds. Many parameters that affect the coating, such as preconditioning (with different acids and bases), buffer, temperature during coating, and the physical structures of liposomes, were studied, with and without calcium in the liposome solution. The separation of steroids was improved and was less dependent on coating conditions when calcium was present during the coating. Capillaries optimally coated with anionic phospholipids were applied in the separation of phenols. [ABSTRACT FROM AUTHOR]

Of ammonium, lithium and sodium salts of dodecyl sulfate studied as surfactants in the separation of iridoid glycosides by micellar electrokinetic capillary chromatography (MECC), the last one gave the best results. Eleven neutral iridoid glycosides were separated by MECC with sodium dodecyl sulfate as surfactant, and the water–micelle partition coefficients of the compounds were calculated. The separation system was coupled via a coaxial sheath flow electrospray interface to a mass spectrometer, and the partial filling technique was used in the on-line analysis. Seven plant species belonging to five genera (Plantago, Veronica, Melampyrum, Succisa and Valeriana) were screened for the iridoid glycosides by the new method that was developed. The findings confirmed those of an earlier study on five of the iridoid glycosides. Some new iridoid glycosides were found in Plantago lanceolata, Veronica spicata and V. chamaedrys. [Copyright &y& Elsevier]

Regioselective modifications of cellulose using activated cellulose derivatives such as 6‐halo‐6‐deoxycelluloses provide a convenient approach for developing sustainable products with properties tailored to specific applications. However, maintaining precise regiochemical control of substituent distribution in 6‐halo‐6‐deoxycelluloses is challenging due to their insolubility in most common solvents and the resulting difficulties in precise structure elucidation by modern instrumental analytical techniques. Herein, an accessible NMR‐based approach toward detailed characterization of 6‐halo‐6‐deoxycelluloses, including the determination of the degrees of substitution at carbon 6 (DS6), is presented. It is shown that the direct‐dissolution cellulose solvent, tetrabutylphosphonium acetate:DMSO‐d6, converts 6‐halo‐6‐deoxycelluloses to 6‐monoacetylcellulose, enabling in situ solution‐state NMR measurements. A range of 1D and 2D NMR experiments is used to demonstrate the quantitivity of the conversion and provide optimum dissolution conditions. In comparison with other NMR‐based derivatization protocols for elucidating the structure of 6‐halo‐6‐deoxycelluloses, the presented approach offers major advantages in terms of accuracy, speed, and simplicity of analysis, and minimal requirements for reagents or NMR instrumentation. [ABSTRACT FROM AUTHOR]

Investigates the physiochemical properties of a mixed micellar system of sodium dodecyl sulfate and sodium cholate. Study of micelle-micelle and micelle-buffer interactions in a buffer solution; Micellar electrokinetic capillary chromatography separation of corticosteroids and cmc determinations; Nuclear magnetic resonance relaxation studies.

Liposome capillary electrokinetic chromatography was used to investigate the interactions between three β‐blockers of different hydrophobicity and various liposome solutions. The studied β‐blockers comprised alprenolol, propranolol, and carvedilol. The composition of the liposome solutions, containing 1‐palmitoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphocholine, 1,2‐dioleoyl‐sn‐glycero‐3‐phos‐phoethanolamine, 1‐palmitoyl‐2‐oleoyl‐sn‐glycero‐3‐phospho‐l‐serine, and cholesterol in various molar ratios, was designed by a response surface methodology‐central composite design approach. Subsequently, after conducting the liposome capillary electrokinetic chromatography experiments and determining the retention factors from the electrophoretic mobilities of the compounds, and further calculating the distribution coefficients, an analysis of variance was performed. After extracting the statistical models, optimal operational conditions were obtained based on the developed models. To further investigate the interactions between the β‐blockers and the liposomes, nanoplasmonic sensing experiments were carried out on two different liposome systems. The overall results demonstrate the strong influence of cholesterol and 1‐palmitoyl‐2‐oleoyl‐sn‐glycero‐3‐phospho‐l‐serine on the distribution coefficients. [ABSTRACT FROM AUTHOR]

• Chromatographic retention of 26 molecules was studied by IAM LC and LEKC. • LEKC data could not be achieved for hydrophilic neutral or anionic compounds. • IAM related better with partition than with distribution coefficients in n-octanol. • For LEKC, the relationships were linear to partition coefficients in n-octanol. • LEKC outperformed IAM in modelling the pulmonary permeability of drugs. This study pioneers a comparison of the application of biomimetic techniques, immobilised artificial membrane liquid chromatography (IAM LC) and liposome electrokinetic capillary chromatography (LEKC), for the prediction of pulmonary drug permeability. The pulmonary absorption profiles of 26 structurally unrelated drug-like molecules were evaluated using their IAM hydrophobicity index (CHI IAM) measured in IAM LC, and the logarithm of distribution constants (log K LEKC) derived from the LEKC experiments. Lipophilicity (phospholipids) parameters obtained from IAM LC and most LEKC analyses were linearly related to the n -octanol/water partitioning coefficients of the neutral forms (i.e. , log P o/w values) to a moderate extent. However, the relationship with distribution coefficients at the experimental pH (7.4) (i.e., log D 7.4) were weaker overall for IAM LC data and sigmoidal for some liposome compositions (phosphatidyl choline (PC): phosphatidyl inositol (PI) 85:15 mol% and 90:10 mol%) and concentrations (4 mM) in LEKC. This suggests that phospholipid partitioning supports both hydrophobic and electrostatic interactions occurring between ionised drugs and charged phospholipid moieties. The latter interactions are original when compared to those taking place in the more established n -octanol/water partitioning systems. A stronger correlation (R2 > 0.65) was identified between the LEKC retention parameters, and the experimental apparent lung permeability (i.e., log P app values) as opposed to the values obtained by IAM LC. Therefore, LEKC offers unprecedented advantages over IAM LC in simulating cell membrane partitioning processes in the pulmonary delivery of drugs. Although LEKC has the advantage of more effectively simulating the electrostatic and hydrophobic forces in drug/pulmonary membrane interactions in vitro , the technique is unsuitable for analysing highly hydrophilic neutral or anionic compounds at the experimental pH. Conversely, IAM LC is useful for analysing compounds spanning a wider range of lipophilicity. Its simpler and more robust implementation, and propensity for high-throughput automation make it a favourable choice for researchers in drug development and pharmacological studies. [ABSTRACT FROM AUTHOR]

Highlights: [•] Silica-based monolith is introduced as a support for liposome immobilization. [•] A new biomimicking chromatographic phase was evaluated by capillary LC and cryo-SEM. [•] Analyte–liposome interactions were investigated. [•] The column permeability depends on the type of liposome dispersion and buffer used. [ABSTRACT FROM AUTHOR]

Intravenous lipid emulsion is a recommended treatment for local anesthetic intoxication. The lipid sink theory hypothesizes that the mechanism behind the lipid treatment is the entrapment of toxic drugs in plasma, preventing them from reaching target receptors. Lipid sink treatment has also been used as a last refuge treatment for severe tricyclic antidepressant intoxication with seemingly beneficial results. We selected three drugs, i.e. amiodarone, ketamine, and amitriptyline, that can cause severe intoxication and compared their interactions with two commercial fat emulsions (Intralipid® and ClinOleic®) and one synthetic liposome (80:20 mol% phosphatidylcholine/phosphatidylglycerol) dispersion. The interaction studies were carried out by capillary electrokinetic chromatography and the retention factors and distributions constants of the drugs were calculated. The results demonstrate that there is stronger interaction between the drugs and the synthetic liposome dispersion than with the commercial emulsions. [ABSTRACT FROM AUTHOR]

Abstract: The function of mammalian ocular lens is to provide a sharp image to the retina. Accordingly, the lens needs to be transparent and minimize light scattering. To do so the lens fiber cells first loose intracellular organelles, organize the cytoplasm and arrange the fiber cell membranes. Because the fiber cells are metabolically inactive, the plasma membrane becomes the only cellular organelle and consequently, the phase behavior of these membranes determines the physiological state of the lens. Previous studies have shown that lipids extracted from the nuclear and cortical region of human lens show a temperature-induced phase transition close to the body temperature. Yet, the physiological function of this phase transition is not known, and even the presence of the phase transition in intact lenses is unknown. Positron annihilation lifetime spectroscopy (PALS) was used to characterize the sub-nanometer-sized local structure of intact porcine lens and these studies were complemented with differential scanning calorimeter and mass spectrometric analysis in extracted porcine lens lipids. Using PALS, we present evidence for the presence of a temperature-dependent structural transition centered at 35.5°C in-situ in clear extracted porcine lenses. Further studies employing extracted lens lipids and purified egg-yolk sphingomyelin and cholesterol mixtures suggest that the nano-scale transition emerges from the phase behavior of lens lipids. Based on our results, PALS seems to be a viable method for gaining additional information on biological tissues, especially since it enables non-destructive studies on intact tissues. [Copyright &y& Elsevier]

Abstract: In the case of local anesthetic intoxication, intravenous administration of lipid-based Intralipid dispersion (Fresenius Kabi) can be used for the entrapment of hydrophobic drugs. Our long-term aim is to develop a sensitive, efficient, and non-harmful lipid-based formulation to specifically trap harmful substances. In this study liposome electrokinetic capillary chromatography (LEKC) was used to study the interactions between local anesthetics and Intralipid or liposome dispersions. Intralipid dispersion and extruded liposomes with different concentrations of 1-palmitoyl-2-oleyl-sn-glycerophosphatidylcholine (POPC), phosphatidylglycerol, cardiolipin, cholesterol, oleic acid, and linoleic acid were used as a pseudostationary phase in LEKC and their interactions with lidocaine, prilocaine, and bupivacaine were studied. POPC liposomes containing 1mol% of palmitoyl-2-[12-[(7-nitro-2-1,3-benzoxadiazol-4-yl)amino]dodecanoyl]-sn-glycero-3-phosphocholine as a fluorescent marker were used for the first time in LEKC connected with laser-induced fluorescent detection in order to calculate the retention factor for anesthetics. [Copyright &y& Elsevier]

Abstract: Anionic phospholipids phosphatidic acid (PA), phosphatidylglycerol (PG), phosphatidylinositol (PI), and phosphatidylserine (PS) were examined for their effect on 1-palmitoyl-2-oleyl-sn-glycero-3-phosphatidylcholine (POPC)-containing liposomes used as coating material in capillary electrochromatography. Liposome solvent was N-(2-hydroxyethyl)piperazine-N′-(2-ethanesulfonic acid) (HEPES) buffer at pH 7.4 with and without 3mM of CaCl2. The background electrolyte solution was HEPES buffer at pH 7.4. The net charge, size, and short-term stability of the liposomes were measured with a Zetasizer. Results showed that calcium interacts with all liposomes but most strongly with POPC/PA. The relative migration times, retention factors, and resolution of the model analytes (one cationic, three uncharged ions, and one anionic) were studied. All liposomes successfully coated the silica capillary. Without calcium the strongest interaction and best separation of the analytes were with the POPC/PI and POPC/PS coatings, while interactions with the POPC/PA coating were weak. Calcium enhanced the interactions of the model analytes with all coatings, and the interactions were then strongest with the POPC/PA coating. In the presence of calcium there appears to be a slight reorganization of the coating with increasing number of runs. Our results indicate strong interactions between calcium and the phosphate groups in phospholipids and demonstrate the significant role of the phospholipid polar head group in phospholipid coatings on silica surfaces. [Copyright &y& Elsevier]

Abstract: 1,2-Dioleyl-3-trymethylammoniumpropane (DOTAP) lipid vesicles were employed as coating precursors to obtain a semipermanent cationic lipid bilayer in silica capillary. The coating procedure was relatively fast and simple. Reliable results for the separation of four basic proteins (α-chymotrypsinogen A, ribonuclease A, cytochrome C, lysozyme) were obtained by using an acetate buffer under acidic conditions. The RSDs of the migration times were not higher than 0.5% run-to-run and about 1% day-to-day (3 days), while the RSDs of the peak areas were within 7% day-to-day (3 days). The day-to-day RSD of the EOF mobility of about 1%, confirmed that the DOTAP coating was stable for the separation of basic proteins, under acidic buffers. In addition to basic proteins the DOTAP coating was found suitable under acidic conditions for the repeatable separation of neutral steroids. The potential of DOTAP as a carrier in background electrolyte solution was studied. [Copyright &y& Elsevier]

Abstract: Greater stability of liposome coatings and improved resolution of model steroids in capillary electrochromatography (CEC) were sought by adding small diamines (ethylenediamine, diaminopropane, bis-tris-propane, or N-(2-hydroxyethyl)piperazine-N′-(2-ethanesulfonic acid, HEPES)) to the liposome solution before coating of fused silica capillaries. The phospholipid coatings consisted of 1mM of 8:2mol% phosphatidylcholine (PC)/phosphatidylserine (PS) and 5mM of modifier in buffer solutions (acetate, phosphate, or Tris) at pH 4.0–7.4. The coating was based on a published procedure, and five steroids were used as neutral model analytes in evaluation of the coating. The results showed that under optimal conditions, the small linear diamines increased the packing density of anionic phospholipids, leading to improved separations. In addition, the choice of buffer for the liposome coating and separation appeared to influence the performance of the coatings. While buffers with amino groups take part in the phospholipid bilayer formation, buffers like phosphate may even have negative effect on coating formation. The factors affecting phospholipid coatings with diamines as modifiers are clarified. [Copyright &y& Elsevier]

Abstract: Polyelectrolyte complex (PEC) formation between cationic poly(methacryloxyethyl trimethylammonium chloride) (PMOTAC) and anionic poly(ethylene oxide)-block-poly(sodium methacrylate) (PEO-b-PMANa) was studied by asymmetrical flow field-flow fractionation and dynamic light scattering. The influence of ionic strength and mixing ratios of the charged units of the polyelectrolytes on the complex formation was evaluated. The diffusion coefficients and the hydrodynamic diameter distributions of the free and complexed polyelectrolytes were measured. In the absence of salt, the weight averaged hydrodynamic diameters were 48 and 28nm for PMOTAC and PEO-b-PMANa, respectively. In the presence of salt, the particles were smaller, with weight averaged hydrodynamic diameters of 44–45 and 8–10nm, respectively. In salt-free solution, at 1:1 mixing ratio of the charged monomer units of PMOTAC and PEO-b-PMANa, polydisperse particles with diameters of 2000–4000nm were formed. In the presence of 20, 80, and 160mM of sodium chloride, the 1:1 complexes were relatively monodisperse particles with weight averaged hydrodynamic diameters of 93, 124, and 120nm, respectively. [Copyright &y& Elsevier]

Large unilamellar vesicles of egg-phosphatidylcholine (eggPC), a naturally occurring phospholipid, were used in capillary electrophoresis (CE) for semi-permanent coating of fused silica capillaries. The stability of the phospholipid coating was tested at different cetyltrimethylammonium bromide (CTAB) concentrations with and without CaCl2 present in the coating solution. The effect of physical factors influencing the coating stability (e.g. duration of the coating time, storage temperature of the coating solution) were also studied. Standing overnight in background electrolyte (BGE) solution did not alter the eggPC phospholipid coating noticeably. The performance of the coating was tested with a mixture of basic proteins (lysozyme, ribonuclease A and a-chymotrypsinogen A). Highest efficiencies (over 200,000 plates m-1) were achieved when the capillary was filled for 15 h with a liposome solution containing both CTAB and CaCl2. [ABSTRACT FROM AUTHOR]

A new and relatively simple method was developed for coating of capillaries in electrophoresis with liposomes. The liposomes, with a diameter of about 100 nm, are large unilamellar vesicles prepared by extrusion. The liposomes contained 1-palmitoyl-2-oleyl-sn-glycero-3-phosphatidylcholine (POPC) or POPC with different proportions of bovine brain phosphatidylserine (PS) and cholesterol. They formed a bilayer structure on the silica surface enabling the separation of neutral compounds. The effectiveness of the coating in separation was evaluated with use of uncharged steroids as model compounds. The coating was also studied by measuring the electroosmotic flow. The best results, taking into consideration both separation and stability, were achieved with anionic 80:20 mol% POPC/PS liposomes. In addition, the effect of coating conditions on the results was investigated. Among the buffers studied [N-(2-hydroxyethyl)piperazine-N′-(2-ethanesulfonic acid) (HEPES), phosphate, tris(hydroxymethyl)aminomethane (Tris) and N-tris(hydroxymethyl)methylglycine (Tricine)], HEPES seemed to have a significant effect on the success of the coating. Successful separation of steroids was achieved only when HEPES buffer was used in the coating procedure and in the background electrolyte solution for the separation. With all other buffers the peaks of the model compounds overlapped. [Copyright &y& Elsevier]

Amphiphilic diblock copolymers consisting of a hydrophobic core containing a polymerized ionic liquid and an outer shell composed of poly(N‐isoprolylacrylamide) were investigated by capillary electrophoresis and asymmetrical flow‐field flow fractionation. The polymerized ionic liquid comprised poly(2‐(1‐butylimidazolium‐3‐yl)ethyl methacrylate tetrafluoroborate) with a constant block length (n = 24), while the length of the poly(N‐isoprolylacrylamide) block varied (n = 14; 26; 59; 88). Possible adsorption of the block copolymer on the fused silica capillary, due to alterations in the polymeric conformation upon a change in the temperature (25 and 45 °C), was initially studied. For comparison, the effect of temperature on the copolymer conformation/hydrodynamic size was determined with the aid of asymmetrical flow‐field flow fractionation and light scattering. To get more information about the hydrophilic/hydrophobic properties of the synthesized block copolymers, they were used as a pseudostationary phase in electrokinetic chromatography for the separation of some model compounds, that is, benzoates and steroids. Of particular interest was to find out whether a change in the length or concentration of the poly(N‐isoprolylacrylamide) block would affect the separation of the model compounds. Overall, our results show that capillary electrophoresis and asymmetrical flow‐field flow fractionation are suitable methods for characterizing conformational changes of such diblock copolymers. [ABSTRACT FROM AUTHOR]

Abstract This work presents the development and validation of a quantitative HILIC UHPLC-ESI-QTOF-MS/MS method for amino acids combined with untargeted metabolic profiling of human corneal epithelial (HCE) cells after treatment with ionic liquids. The work included a preliminary metabotoxicity screening of 14 different ionic liquids, of which 9 carefully selected ionic liquids were chosen for a metabolomics study. This study is focused on the correlation between the toxicity of the ionic liquids and their metabolic profiles. The method development included the comparison of different MS/MS acquisition modes. A sequential window acquisition of all theoretical fragment ion mass spectra (SWATH) method with variable Q1 window widths and narrow Q1 target windows of 5 Da for most of the amino acids was selected as the optimal acquisition mode. Due to the absence of a true blank matrix, 13C,15N-isotopically labelled amino acids were utilized as surrogate calibrants, instead of proteinogenic amino acids. Partial least squares (PLS) analysis of the median effective concentrations (EC 50) of 9 selected ionic liquids showed a correlation with their metabolic profile measured by the untargeted screening. Graphical abstract fx1 Highlights • UHPLC-ESI-MS/MS method for quantitative amino acids analysis in cells developed. • Data-independent acquisition allows simultaneous untargeted metabolic profiling. • PLS reveals a correlation between metabolic profiles and toxicity of ILs. • The most toxic ILs tested were [P 4441 ][OAc], [P 14444 ][OAc] and [P 14444 ]Cl. • LC-MS metabolic profiling seems to be a useful strategy to classify the toxicity of ILs. [ABSTRACT FROM AUTHOR]

We introduce rapid replica molding of ordered, high-aspect-ratio, thiol-ene micropillar arrays for implementation of microfluidic immobilized enzyme reactors (IMERs). By exploiting the abundance of free surface thiols of off-stoichiometric thiol-ene compositions, we were able to functionalize the native thiol-ene micropillars with gold nanoparticles (GNPs) and these with proteolytic α-chymotrypsin (CHT) via thiol-gold interaction. The micropillar arrays were replicated via PDMS soft lithography, which facilitated thiol-ene curing without the photoinitiators, and thus straightforward bonding and good control over the surface chemistry (number of free surface thiols). The specificity of thiol-gold interaction was demonstrated over allyl-rich thiol-ene surfaces and the robustness of the CHT-IMERs at different flow rates and reaction temperatures using bradykinin hydrolysis as the model reaction. The product conversion rate was shown to increase as a function of decreasing flow rate (increasing residence time) and upon heating of the IMER to physiological temperature. Owing to the effective enzyme immobilization onto the micropillar array by GNPs, no further purification of the reaction solution was required prior to mass spectrometric detection of the bradykinin hydrolysis products and no clogging problems, commonly associated with conventional capillary packings, were observed. The activity of the IMER remained stable for at least 1.5 h (continuous use), suggesting that the developed protocol may provide a robust, new approach to implementation of IMER technology for proteomics research. Graphical abstract [ABSTRACT FROM AUTHOR]

Toxicity of β -blockers is one of the most common causes of poison-induced cardiogenic shock throughout the world. Therefore, methodologies for in vivo removal of the drugs from the body have been under investigation. Intralipid emulsion (ILE) is a common commercial lipid emulsion used for parenteral nutrition, but it has also been administered to patients suffering from drug toxicities. In this work, a set of β -blockers of different hydrophobicity's (log K D values ranging from 0.16 to 3.8) were investigated. The relative strength of the interactions between these compounds and the ILE was quantitatively assessed by means of binding constants and adsorption constants of the formed β -blocker-ILE complexes. The binding constants were determined by capillary electrokinetic chromatography and the adsorption constants were calculated based on different adsorption isotherms. Expectedly, the binding constants were strongly related to the log K D values of the β -blockers. The binding and adsorption constants also show that less hydrophobic β -blockers interact with ILE, suggesting that this emulsion could be useful for capturing such compounds in cases of their overdoses. Thus, the use of ILE for treatment of toxicities caused by a larger range of β -blockers is worth further investigation. • Interactions of β-blockers with Intralipid emulsion (ILE) were studied by EKC. • In-depth adsorption isotherm analysis was performed on β-blocker-ILE interactions. • Binding constants of ILE-β-blocker complexes were determined. • The more hydrophobic the β-blocker, the stronger are the interactions with ILE. • Hydrophobic β-blockers can potentially be captured by ILE in case of overdoses. [ABSTRACT FROM AUTHOR]

A methodology for preparing phosphonium-based ionic liquid modified silica-based monolithic capillary columns is presented. The silica monolithic columns with dimensions of 150 × 0.1 mm were modified by a phosphonium-based ionic liquid (trioctyl(3/4-vinylbenzyl)phosphonium chloride) via 3-(trimethoxysilyl)propyl methacrylate. The prepared columns were evaluated under hydrophilic interaction liquid chromatography separation conditions, employing a sample mixture containing purine and pyrimidine bases and nucleosides. Detection was made by UV. The high efficiency of the original silica monolith was preserved even after modification, and it reached values in the range of 98,000–174,000 theoretical plates/m. The effects of the concentration of acetonitrile in the mobile phase, the presence of additives in the mobile phase, such as, acetic acid or ammonium acetate, and the pH of the mobile phase on the separation of some selected analytes were investigated. The prepared columns showed different separation selectivity compared to silica, phenyl and sulfobetaine stationary phases. [ABSTRACT FROM AUTHOR]

This study aims at extending the understanding of the toxicity mechanism of ionic liquids (ILs) using various analytical methods and cytotoxicity assays. The cytotoxicity of eight ILs and one zwitterionic compound was determined using mammalian and bacterial cells. The time dependency of the IL toxicity was assessed using human corneal epithelial cells. Hemolysis was performed using human red blood cells and the results were compared with destabilization data of synthetic liposomes upon addition of ILs. The effect of the ILs on the size and zeta potential of liposomes revealed information on changes in the lipid bilayer. Differential scanning calorimetry was used to study the penetration of the ILs into the lipid bilayer. Pulsed field gradient nuclear magnetic resonance spectroscopy was used to determine whether the ILs occurred as unimers, micelles, or if they were bound to liposomes. The results show that the investigated ILs can be divided into three groups based on the cytotoxicity mechanism: cell wall disrupting ILs, ILs exerting toxicity through both cell wall penetration and metabolic alteration, and ILs affecting solely on cell metabolism. [ABSTRACT FROM AUTHOR]

Abstract: This study aims at extending the understanding of the toxicity mechanism of ionic liquids (ILs) using various analytical methods and cytotoxicity assays. The cytotoxicity of eight ILs and one zwitterionic compound was determined using mammalian and bacterial cells. The time dependency of the IL toxicity was assessed using human corneal epithelial cells. Hemolysis was performed using human red blood cells and the results were compared with destabilization data of synthetic liposomes upon addition of ILs. The effect of the ILs on the size and zeta potential of liposomes revealed information on changes in the lipid bilayer. Differential scanning calorimetry was used to study the penetration of the ILs into the lipid bilayer. Pulsed field gradient nuclear magnetic resonance spectroscopy was used to determine whether the ILs occurred as unimers, micelles, or if they were bound to liposomes. The results show that the investigated ILs can be divided into three groups based on the cytotoxicity mechanism: cell wall disrupting ILs, ILs exerting toxicity through both cell wall penetration and metabolic alteration, and ILs affecting solely on cell metabolism. [ABSTRACT FROM AUTHOR]

The present work aims at studying the interactions between cholesterol-rich phosphatidylcholine-based lipid vesicles and trioctylmethylphosphonium acetate ([P 8881 ][OAc]), a biomass dissolving ionic liquid (IL). The effect of cholesterol was assayed by using differential scanning calorimetry (DSC) and nanoplasmonic sensing (NPS) measurement techniques. Cholesterol-enriched dipalmitoyl-phosphatidylcholine vesicles were exposed to different concentrations of the IL, and the derived membrane perturbation was monitored by DSC. The calorimetric data could suggest that the binding and infiltration of the IL are delayed in the vesicles containing cholesterol. To clarify our findings, NPS was applied to quantitatively follow the resistance of 1-palmitoyl-2-oleoyl- sn -glycero-3-phosphocholine incorporating 0, 10, and 50 mol% of cholesterol toward the IL exposure over time. The membrane perturbation induced by different concentrations of IL was found to be a concentration dependent process on cholesterol-free lipid vesicles. Moreover, our results showed that lipid depletion in cholesterol-enriched lipid vesicles is inversely proportional to the increasing amount of cholesterol in the vesicles. These findings support that cholesterol-rich lipid bilayers are less susceptible toward membrane disrupting agents as compared to membranes that do not incorporate any sterols. This probably occurs because cholesterol tightens the phospholipid acyl chain packing of the plasma membranes, increasing their resistance and reducing their permeability. [ABSTRACT FROM AUTHOR]

Coating of colloidal lignin particles (CLPs), or lignin nanoparticles (LNPs), with proteins was evaluated in order to establish a safe, self-assembly mediated modification technique to tune their surface chemistry. Gelatin and poly- l-lysine formed the most pronounced protein corona on the CLP surface, as determined by dynamic light scattering (DLS) and zeta potential measurements. Spherical morphology of individual protein coated CLPs was confirmed by transmission electron (TEM) and atomic force (AFM) microscopy. A mechanistic adsorption study with several random coiled and globular model proteins was carried out using quartz crystal microbalance with dissipation monitoring (QCM-D). The three-dimensional (3D) protein fold structure and certain amino acid interactions were decisive for the protein adsorption on the lignin surface. The main driving forces for protein adsorption were electrostatic, hydrophobic, and van der Waals interactions, and hydrogen bonding. The relative contributions of these interactions were highly dependent on the ionic strength of the surrounding medium. Capillary electrophoresis (CE) and Fourier transform infrared spectroscopy (FTIR) provided further evidence of the adsorption-enhancing role of specific amino acid residues such as serine and proline. These results have high impact on the utilization of lignin as colloidal particles in biomedicine and biodegradable materials, as the protein corona enables tailoring of the CLP surface chemistry for intended applications. [ABSTRACT FROM AUTHOR]

Owing to their unique properties and unlimited structural combinations, the ubiquitous use of ionic liquids (ILs) is steadily increasing. The objective of the present work is to shed light onto the effects of amidinium- and phosphonium-based ILs on phospholipid vesicles using a nanoplasmonic sensing measurement technique. A new and relatively simple method was developed for the immobilization of large unilamellar vesicles on two different hydrophilic surfaces composed of titanium dioxide and silicon nitride nanolayers. Among the pretreatment conditions studied, vesicle attachment on both substrate materials was achieved with HEPES buffer in the presence of sodium hydroxide and calcium chloride. To get an understanding of how ILs interact with intact vesicles or with supported lipid bilayers, the ILs 1,5-diazabicyclo(4.3.0)non-5-enium acetate ([DBNH][OAc]), tributyl(tetradecyl)phosphonium acetate ([P14444][OAc]), and tributylmethylphosphonium acetate ([P4441][OAc]) were introduced into the biomimetic system, and the characteristics of their interactions with the immobilized vesicles were determined. Depending on the IL, in situ real-time IL binding and/or phospholipid removal processes were observed. Although [DBNH][OAc] did not have any significant effect on the phospholipid vesicles, the strongest and the most significant effect was observed with [P14444][OAc]. The latter caused clear changes in the phospholipid bilayer: the ILs interacted with the bilayers, resulting in deformation of the vesicles most probably due to the formation of vesicle-IL aggregates. Only a mild effect was observed when [P4441][OAc], at a very high concentration, was exposed to the intact vesicles. In general, these results led to new insights into the effects of ILs on phospholipid vesicles, which are of great importance to the overall understanding of the harmfulness of ILs on biomembranes and biomimicking systems. In addition, the present work highlights the pivotal role of this highly surface-sensitive indirect biosensing technique in scrutinizing and dissecting the integrity and architecture of phospholipid vesicles in the nanoscale range. [ABSTRACT FROM AUTHOR]

Liposomes were used as biomimetic models in capillary electrokinetic chromatography (EKC) for the determination of distribution constants (K D ) of certain local anesthetics and a commonly used preservative. Synthetic liposomes comprised phosphatidylcholine and phosphatidylglycerol phospholipids with and without cholesterol. In addition, ghost liposomes made from red blood cell (RBC) lipid extracts were used as pseudostationary phase to acquire information on how the liposome composition affects the interactions between anesthetics and liposomes. These results were compared with theoretical distribution coefficients at pH 7.4. In addition to 25 °C, the distribution constants were determined at 37 and 42 °C to simulate physiological conditions. Moreover, the usability of five electroosmotic flow markers in liposome (LEKC) and micellar EKC (MEKC) was studied. LEKC was proven to be a convenient and fast technique for obtaining data about the distribution constants of local anesthetics between liposome and aqueous phase. RBC liposomes can be utilized for more representative model of cellular membranes, and the results indicate that the distribution constants of the anesthetics are greatly dependent on the used liposome composition and the amount of cholesterol, while the effect of temperature on the distribution constants is less significant. [ABSTRACT FROM AUTHOR]

The effects of ionic liquids on model phospholipid membranes were studied by small-angle X-ray scattering, dynamic light scattering (DLS) and zeta potential measurements. Multilamellar 1-palmitoyl-2-oleoyl- sn -glycero-3-phosphocholine liposomes and large unilamellar vesicles composed of l -α-phosphatidylcholine (eggPC) and l -α-phosphatidylglycerol (eggPG) (80:20 mol%) or eggPC, eggPG, and cholesterol (60:20:20 mol%) were used as biomimicking membrane models. The effects of the phosphonium-based ionic liquids: tributylmethylphosphonium acetate, trioctylmethylphosphonium acetate, tributyl(tetradecyl)-phosphonium acetate, and tributyl(tetradecyl)-phosphonium chloride, were compared to those of 1-ethyl-3-methyl-imidazolium acetate. With multilamellar vesicles, the ionic liquids that did not disrupt liposomes decreased the lamellar spacing as a function of concentration. The magnitude of the effect depended on concentration for all studied ionic liquids. Using large unilamellar vesicles, first a slight decrease in the vesicle size, then aggregation of vesicles was observed by DLS for increasing ionic liquid concentrations. At concentrations just below those that caused aggregation of liposomes, large unilamellar vesicles were coated by ionic liquid cations, evidenced by a change in their zeta potential. The ability of phosphonium-based ionic liquids to affect liposomes is related to the length of the hydrocarbon chains in the cation. Generally, the ability of ionic liquids to disrupt liposomes goes hand in hand with inducing disorder in the phospholipid membrane. However, trioctylmethylphosphonium acetate selectively extracted and induced a well-ordered lamellar structure in phospholipids from disrupted cholesterol-containing large unilamellar vesicles. This kind of effect was not seen with any other combination of ionic liquids and liposomes. [ABSTRACT FROM AUTHOR]

The effect of 11 common amidinium, imidazolium, and phosphonium based ionic liquids (ILs) on zebrafish (Danio rerio) and Chinese hamster ovary cells (CHO) was investigated with specific emphasis on the effect of anion and cation chain length and aggregation of phosphonium based ILs. Viability and behavioral alteration in the locomotor activity and place preference, after IL treatment of 5 days postfertilization larvae, was recorded. Behavior and histological damage evaluation was performed for adult fish in order to get insight into the long-term effects of two potential biomass-dissolving ILs, [DBNH][OAc] and [P4441][OAc]. To get an understanding of how IL aggregation is linked to the toxicity of ILs, median effective concentrations (EC50) and critical micelle concentrations (CMC) were determined. The long-chain ILs were significantly more toxic than the short-chain ones, and the anion chain length was shown to be less significant than the cation chain length when assessing the impact of ILs on the viability of the organisms. Furthermore, most of the ILs were as monomers when the EC50 was reached. In addition, the ILs used in the long-term tests showed no significant effect on the zebrafish behavior, breeding, or histology, within the used concentration range. [ABSTRACT FROM AUTHOR]

This work describes for the first time a continuous process for selective metal extraction with an ionic liquid (IL) at room temperature. The hydrophobic fatty acid based IL tetraoctylphosphonium oleate ([P 8888 ][oleate]) was specifically chosen for its low viscosity and high selectivity towards transition metals. Applying [P 8888 ][oleate] for continuous metal ion extraction with 0.1 M sodium oxalate for regeneration resulted in a process with good and stable extraction efficiencies over time. The selectivity of the IL resulted in a process in which cobalt was selectively removed from two mixed salt solutions (Co/Na, Ca/Co/K) to obtain a pure cobalt stream after stripping the IL. The performed experiments showed that the contact time of the IL for extraction and stripping strongly influenced the achieved efficiencies. The stability of the IL was tested and it was shown that the fatty acid based IL was stable for the duration of the experiment. Liposome tests showed that the IL is very hydrophobic, which limits its leakage towards the water phase, but also results in a higher toxicity towards cell membranes. Economic analysis shows that the IL based process is not (yet) economical compared to ion-exchange resins, in case demineralised water is the only product. However, if the recovery of valuable metals is also taken into account and/or if brine disposal is an issue, then continuous IL metal extraction systems must be regarded as promising alternatives. [ABSTRACT FROM AUTHOR]

The worldwide use of ionic liquids (ILs) is steadily increasing, and even though they are often referred to as “green solvents” they have been reported to be toxic, especially toward aquatic organisms. In this work, we thoroughly study two phosphonium ILs; octyltributylphosphonium chloride ([P 8444 ]Cl) and tributyl(tetradecyl)phosphonium chloride ([P 14444 ]Cl). Firstly, the critical micelle concentrations (CMCs) of the ILs were determined with fluorescence spectroscopy and the optical pendant drop method in order to gain an understanding of the aggregation behavior of the ILs. Secondly, a biomimicking system of negatively charged unilamellar liposomes was used in order to study the effect of the ILs on biomembranes. Changes in the mechanical properties of adsorbed liposomes were determined by quartz crystal microbalance (QCM) measurements with silica coated quartz crystal sensors featuring a polycation layer. The results confirmed that both ILs were able to incorporate and alter the biomembrane structure. The membrane disrupting effect was emphasized with an increasing concentration and alkyl chain length of the ILs. In the extreme case, the phospholipid membrane integrity was completely compromised. [ABSTRACT FROM AUTHOR]

The effect of three phosphonium and imidazolium ionic liquids (ILs) on the interaction between liposomes and common pharmaceuticals found in wastewaters was studied. The liposomes comprised zwitterionic phosphatidyl choline and negatively charged phosphatidyl glycerol. A set of common cationic, anionic, and neutral compounds with varying chemical composition and unique structures were included in the study. The electrophoretic mobilities of the analytes were determined using conventional capillary electrophoresis (CE), using CE under reversed electroosmotic flow mobility conditions, and in the presence of ILs in the background electrolyte (BGE) solution by electrokinetic chromatography (EKC). In order to evaluate the impact of ILs on the interaction between the compounds and the liposomes, EKC was performed with liposome dispersions, with and without ILs. The retention factors of the compounds were calculated using BGEs including liposome dispersions with and without ILs. Two phosphonium based ILs, namely tributyl(tetradecyl)phosphonium chloride ([P 14444 ]Cl) and octyltributylphosphonium chloride ([P 8444 ]Cl), were chosen due to their long alkyl chains and their low aggregation concentrations. Another IL, i.e. 1-ethyl-3-methylimidazolium acetate ([emim][OAc]), was chosen based on our previous study, which suggests that it has a minimal or even nonexistent effect on liposomes at the used concentrations. The results indicate that the studied ILs have an effect on the interactions between wastewater compounds and liposomes, but the effect is highly dependent on the concentration of the IL and on the IL alkyl chain lengths. Most of the ILs hindered the interactions between the liposomes and the compounds, indicating strong interaction between ILs and liposomes. In addition, the nature of the studied compounds themselves affected the interactions. [ABSTRACT FROM AUTHOR]

In this study a strategy to immobilize phospholipids onto a polymer-based stationary phase is described. Methacrylate-based monoliths in capillary format (150 × 0.1 mm) were modified by soybean phosphatidylcholine through 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide coupling to obtain stationary phases suitable to mimic cell surface membranes. The covalent coupling reaction involves the phosphate group in phospholipids; therefore, the described methodology is suitable for all types of phospholipids. Immobilization of soy bean phosphatidylcholine on the monolith was confirmed by attenuated total reflectance Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry of the fatty alcohol profile, generated upon reductive cleavage of the fatty acyl side chains of the phospholipid on the monolith surface with lithium aluminium hydride. The prepared stationary phases were evaluated through studies on the retention of low-molar mass model analytes including neutral, acidic, and basic compounds. Liquid chromatographic studies confirmed predominant hydrophobic interactions between the analytes and the synthesized stationary phase; however, electrostatic interactions contributed to the retention as well. The synthesized columns showed high stability even with fully aqueous mobile phases such as Dulbecco's phosphate-buffered saline solution. [ABSTRACT FROM AUTHOR]

The toxicity of some promising biomass-dissolving amidinium-, imidazolium-, and phosphonium-based ionic liquids (ILs), toward two different cell lines, human corneal epithelial cells and Escherichia coli bacterial cells, was investigated. In addition, dynamic light scattering (DLS) and ? potential measurements were used to study the effect of the ILs on the size and surface charge of some model liposomes. Capillary electrophoresis (CE) was used for determination of the electrophoretic mobilities of the liposomes and for determination of the critical micelle concentration (cmc) of the ILs. The toxicity of the phosphonium ILs was highly dependent on the longest linear chain of the IL, due to increasing hydrophobicity, with the long-chain phosphonium ILs being toxic while the shorter-chain versions were significantly less toxic or not toxic at all. Amidinium and imidazolium ILs showed no significant effect on the cells, within the concentration range used. Moreover, the more hydrophobic ILs were found to have a major effect on the surface charges and size distributions of the model liposomes, which can lead to disruption of the lipid bilayer. This indicates that the cytotoxicity is at least to some extent dependent on direct interactions between ILs and the biomembrane. [ABSTRACT FROM AUTHOR]