CE and asymmetrical flow-field flow fractionation studies of polymer interactions with surfaces and solutes reveal conformation changes of polymers.

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.

Immobilization of natural lipid biomembranes and their interactions with choline carboxylates. A nanoplasmonic sensing study.

The cell membrane is mainly composed of lipid bilayers with inserted proteins and carbohydrates. Lipid bilayers made of purified or synthetic lipids are widely used for estimating the effect of target compounds on cell membranes. However, the composition of such biomimetic membranes is much simpler than the composition of biological membranes.

Overcoming the Pitfalls of Cytochrome P450 Immobilization through the Use of Fusogenic Liposomes.

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.

Nanoplasmonic Sensing and Capillary Electrophoresis for Fast Screening of Interactions between Phosphatidylcholine Biomembranes and Surfactants.

Nanoplasmonic sensing (NPS), based on localized surface plasmon resonance, with sensors composed of glass covered with golden nanodisks and overlaid with a SiO coating was applied in this study. Egg phosphatidylcholine (eggPC), being an easily accessible membrane-forming lipid, was used for preparation of biomimicking membranes. Small unilamellar vesicles with an approximate hydrodynamic diameter of 30 nm, formed by sonication in 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid buffer, were adsorbed within 10 min on the sensor surface either as intact vesicles or as a planar bilayer.

Correlation between Ionic Liquid Cytotoxicity and Liposome-Ionic Liquid Interactions.

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.

Cholesterol affects the interaction between an ionic liquid and phospholipid vesicles. A study by differential scanning calorimetry and nanoplasmonic sensing.

The present work aims at studying the interactions between cholesterol-rich phosphatidylcholine-based lipid vesicles and trioctylmethylphosphonium acetate ([P][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.

Pure Glaucoma Drugs Are Toxic to Immortalized Human Corneal Epithelial Cells, but They Do Not Destabilize Lipid Membranes.

Purpose: Most pure glaucoma drugs (pGDs) are hydrophobic substances intended to reduce elevated intraocular pressure. The aims of our study were to determine the toxicity of pGDs (brimonidine tartrate, brinzolamide, latanoprost, timolol maleate, and pilocarpine hydrochloride) on ocular surface cells and to establish whether their toxicity is subsequent to cellular membrane destabilization.

Methods: The toxicity of clinically efficient doses of pGDs was measured at different time points in a cell culture of human corneal epithelial cells using a redox indicator.

Adsorption of Proteins on Colloidal Lignin Particles for Advanced Biomaterials.

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.

Unraveling Interactions between Ionic Liquids and Phospholipid Vesicles Using Nanoplasmonic Sensing.

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.

Effects of phosphonium-based ionic liquids on phospholipid membranes studied by small-angle X-ray scattering.

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) (80:20mol%) or eggPC, eggPG, and cholesterol (60:20:20mol%) 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.

Novel cationic polyelectrolyte coatings for capillary electrophoresis.

The use of bare fused silica capillary in CE can sometimes be inconvenient due to undesirable effects including adsorption of sample or instability of the EOF. This can often be avoided by coating the inner surface of the capillary. In this work, we present and characterize two novel polyelectrolyte coatings (PECs) poly(2-(methacryloyloxy)ethyl trimethylammonium iodide) (PMOTAI) and poly(3-methyl-1-(4-vinylbenzyl)-imidazolium chloride) (PIL-1) for CE.

Partial filling affinity capillary electrophoresis including adsorption energy distribution calculations--towards reliable and feasible biomolecular interaction studies.

In this work, a method to study and analyze the interaction data in free solution by exploiting partial filling affinity capillary electrophoresis (PF-ACE) followed by adsorption energy distribution calculations (AED) prior model fit to adsorption isotherms will be demonstrated. PF-ACE-AED approach allowed the possibility to distinguish weak and strong interactions of the binding processes between the most common apolipoprotein E protein isoforms (apoE2, apoE3, apoE4) of high density lipoprotein (HDL) and apoE-containing HDL2 with major glycosaminoglycan (GAG) chain of proteoglycans (PGs), chondroitin-6-sulfate (C6S). The AED analysis clearly revealed the heterogeneity of the binding processes.

Surface initiated polymerization of a cationic monomer on inner surfaces of silica capillaries: analyte separation by capillary electrophoresis versus polyelectrolyte behavior.

[2-(Methacryloyl)oxyethyl]trimethylammonium chloride was successfully polymerized by surface-initiated atom transfer radical polymerization method on the inner surface of fused-silica capillaries resulting in a covalently bound poly([2-(methacryloyl)oxyethyl]trimethylammonium chloride) coating. The coated capillaries provided in capillary electrophoresis an excellent run-to-run repeatability, capillary-to-capillary and day-to-day reproducibility. The capillaries worked reliably over 1 month with EOF repeatability below 0.

Collagen I and III and their decorin modified surfaces studied by atomic force microscopy and the elucidation of their affinity toward positive apolipoprotein B-100 residue by quartz crystal microbalance.

Collagen, the major component of extracellular matrix (ECM) and the most abundant protein in the human body, is implicated in the development of atherosclerosis. Collagen types I and III were immobilized on fused-silica capillary to investigate their shape, size and structure by atomic force microscopy (AFM). For comparison, collagen was also immobilized on a mica surface.

Sugar treatment of human lipoprotein particles and their separation by capillary electrophoresis.

Entrapment of lipoprotein particles in the extracellular matrix of the arterial intima is a characteristic feature of the development of atherosclerosis, the disease behind myocardial infarction and stroke. In this study, sugars were exploited in the separation of lipoproteins by CE. Monosaccharides, disaccharides and one sugar alcohol used during ultracentrifugal isolation of lipoproteins prevented the strong and unfavorable adsorption of lipoprotein particles on the capillary wall, allowing their selective separation in uncoated fused silica capillary.

Open tubular capillary electrochromatography: a useful microreactor for collagen I glycation and interaction studies with low-density lipoprotein particles.

Diabetes, a multifunctional disease and a major cause of morbidity and mortality in the industrialized countries, strongly associates with the development and progression of atherosclerosis. One of the consequences of high level of glucose in the blood circulation is glycation of long-lived proteins, such as collagen I, the most abundant component of the extracellular matrix (ECM) in the arterial wall. Glycation is a long-lasting process that involves the reaction between a carbonyl group of the sugar and an amino group of the protein, usually a lysine residue.

Partial filling affinity capillary electrophoresis with cationic poly(vinylpyrrolidone)-based copolymer coatings for studies on human lipoprotein-steroid interactions.

Human plasma lipoproteins have strong hydrophobic interactions with steroids and their fatty acyl derivatives such as estradiol fatty acyl esters. In this work, affinity capillary electrophoresis with the partial filling technique was applied to study the hydrophobic interactions between lipoproteins, which are nanometer-sized particles, and nonconjugated steroids. The capillaries were first rinsed with one of two novel poly(vinylpyrrolidone) (PVP)-based cationic copolymers that were strongly adsorbed onto the fused-silica surface via electrostatic interactions.

Noncovalent poly(1-vinylpyrrolidone)-based copolymer coating for the separation of basic proteins and lipoproteins by CE.

A new simple and fast noncovalent coating method based on poly(1-vinylpyrrolidone-co-2-dimethylaminoethyl methacrylate) copolymer was developed for CE. Merely 2 min flushing of the capillary with the poly(1-vinylpyrrolidone-co-2-dimethylaminoethyl methacrylate) copolymer was required. The copolymer is adsorbed onto the fused-silica surface by hydrogen bonding and electrostatic interactions.

CEC: a tool for mimicking collagen-surface interactions with apolipoprotein B-100 peptides.

Collagens I and III are involved in the formation of the extracellular matrix and presumably in the development of several diseases, such as atherosclerosis. In this study, stable collagen and collagen-decorin coatings were prepared on the inner surfaces of fused silica CEC capillaries, enabling study of the interactions between collagen and selected peptide fragments of apolipoprotein B-100 (apoB-100), the main protein of low-density lipoprotein (LDL) particles. Interactions of positive, neutral, and negative peptide fragments of apoB-100 were elucidated.