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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]

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]

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]

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]

Ionic liquids are used to dewater a suspension of birch Kraft pulp cellulose nanofibrils (CNF) and as a medium for waterfree topochemical modification of the nanocellulose (a process denoted as "WtF-Nano"). Acetylation was applied as a model reaction to investigate the degree of modification and scope of effective ionic liquid structures. Little difference in reactivity was observed when water was removed, after introduction of an ionic liquid or molecular co-solvent. However, the viscoelastic properties of the CNF suspended in two ionic liquids show that the more basic, but non-dissolving ionic liquid, allows for better solvation of the CNF. Vibrio fischeri bacterial tests show that all ionic liquids in this study were harmless. Scanning electron microscopy and wide-angle X-ray scattering on regenerated samples show that the acetylated CNF is still in a fibrillar form. 1D and 2D NMR analyses, after direct dissolution in a novel ionic liquid electrolyte solution, indicate that both cellulose and residual xylan on the surface of the nanofibrils reacts to give acetate esters. [ABSTRACT FROM AUTHOR]

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]

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]

Lipidomics is an emerging field of science not only due to its integral part of cell biology and biophysics but also due to the key role of lipids in the modulation of membrane physical properties, signaling, and cell death regulation. The aim of this study was to characterize changes in N-palmitoyl ceramide concentration and in the global lipid profile in macrophages challenged by oxidized low-density lipoprotein and nutrient deprived hepatocytes. For this purpose, a quantitative targeted method based on gas chromatography-mass spectrometry for the determination of total N-palmitoyl ceramide concentrations in the cellular membranes of cells under stress was used. Ultrahigh-performance liquid chromatography-quadrupole-time of flight mass spectrometry was applied for the comprehensive profiling of lipids. In essence, we found that both models of cellular stress caused an increase in N-palmitoyl ceramide levels. In addition, increased levels of other ceramides were observed as well as up- and down-regulation of several other lipid species. [ABSTRACT FROM AUTHOR]

Immobilization of drug metabolizing enzymes on solid supports improves prediction of drug‐drug interactions by enabling enzyme inhibition assays under flow conditions. In article number 1800245, Tiina M. Sikanen and co‐workers use fusogenic liposomes for biotinylation of lipid bilayers to facilitate immobilization of the membrane‐bound cytochrome P450s on avidin‐functionalized microfluidic devices. Preservation of the full complexity of the lipid environment ensures that the authentic enzyme kinetic parameters can be maintained. [ABSTRACT FROM AUTHOR]

This work describes a new nanotechnology‐based immobilization strategy for cytochrome P450s (CYPs), the major class of drug metabolizing enzymes. Immobilization of CYPs on solid supports provides a significant leap forward compared with soluble enzyme assays by enabling the implementation of through‐flow microreactors for, for example, determination of time‐dependent inhibition. Immobilization of the complex CYP membrane‐protein system is however particularly challenging as the preservation of the authentic enzyme kinetic parameters requires the full complexity of the lipid environment. The developed strategy is based on the spontaneous fusion of biotinylated fusogenic liposomes with lipid bilayers to facilitate the gentle biotinylation of human liver microsomes that incorporate all main natural CYP isoforms. The same process is also feasible for the biotinylation of recombinant CYPs expressed in insect cells, same as any membrane‐bound enzymes in principle. As a result, CYPs could be immobilized on streptavidin‐functionalized surfaces, both those of commercial magnetic beads and customized microfluidic arrays, so that the enzyme kinetic parameters remain unchanged, unlike in previously reported immobilization approaches that often suffer from restricted substrate diffusion to the enzyme's active site and steric hindrances. The specificity and robustness of the functionalization method of customized microfluidic CYP assays are also carefully examined. Immobilization of membrane‐bound enzymes, such as the drug‐metabolizing cytochromes P450 (CYPs), is facilitated by a novel, nanotechnology‐inspired immobilization method utilizing membrane biotinylation via customized fusogenic liposomes. Unlike in previously reported immobilization approaches, the kinetic characteristics of CYPs remain unchanged using the developed method. [ABSTRACT FROM AUTHOR]