Cupin-1.1 Adsorption Layers at the Surface of 8 M Urea Solutions.

The adsorption layers of cupin-1.1, one of the two evolutionary conserved β-barrel domains of vicilin─the garden pea storage globulin─at the liquid-gas interface were studied by a few methods of the surface chemistry. The kinetic dependencies of the surface pressure of cupin-1.

Physicochemical Studies on Amino Acid Based Metallosurfactants in Combination with Phospholipid.

Dicarboxylate metallosurfactants (AASM), synthesized by mixing N-dodecyl aminomalonate, -aspartate and -glutamate with CaCl, MnCl and CdCl, were characterized by XRD, FTIR, and NMR spectroscopy. Layered structures, formed by metallosurfactants, were evidenced from differential scanning calorimetry and thermogravimetric analyses. Solvent-spread monolayer of AASM in combination with soyphosphatidylcholine (SPC) and cholesterol (CHOL) were studied using Langmuir surface balance.

Dynamic properties of the layers of cupin-1.1 aggregates at the air/water interface.

Spread layers of amorphous aggregates of the structural domain of plant protein vicilin, cupin-1.1, at the water - air interface were studied by the surface tensiometry, dilational surface rheology, Brewster angle and atomic force microscopy. The layer properties differed strongly from the results for the layers of previously studied proteins.

Effect of cationic dendrimer on membrane mimetic systems in the form of monolayer and bilayer.

Interactions between a zwitterionic phospholipid, 1, 2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) and four anionic phospholipids dihexadecyl phosphate (DHP), 1, 2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG), 1, 2-dipalmitoyl-sn-glycero-3-phosphate (DPP) and 1, 2-dipalmitoyl-sn-glycero-3-phospho ethanol (DPPEth) in combination with an additional amount of 30 mol% cholesterol were separately investigated at air-buffer interface through surface pressure (π) - area (A) measurements. π-A isotherm derived parameters revealed maximum negative deviation from ideality for the mixtures comprising 30 mol% anionic lipids. Besides the film functionality, structural changes of the monomolecular films at different surface pressures in the absence and presence of polyamidoamine (PAMAM, generation 4), a cationic dendrimer, were visualised through Brewster angle microscopy and fluorescence microscopic studies.

Dynamic Properties of Adsorption Layers of κ-Casein Fibrils.

The dynamic surface properties of native κ-casein solutions and aqueous dispersions of its fibrils differ significantly from the corresponding properties of the systems with globular proteins. The dependence of the dynamic surface elasticity of κ-casein solutions on surface pressure has a local maximum, indicating partial displacement of macromolecules from the proximal region of the surface layer to the distal one. This dependence becomes monotonic for fibril dispersions, similar to the results for dispersions of globular protein fibrils, but unlike the latter case, the surface elasticity close to the steady state reaches values that are approximately four times higher than the data for native protein solutions at the same concentrations.

Dynamic Surface Properties of α-Lactalbumin Fibril Dispersions.

The dynamic surface properties of aqueous dispersions of α-lactalbumin (ALA) amyloid fibrils differ noticeably from the properties of the fibril dispersions of other globular proteins. As a result, the protocol of the application of ALA fibrils to form stable foams and emulsions has to be deviate from that of other protein fibrils. Unlike the fibrils of β-lactoglobulin and lysozyme, ALA fibrils can be easily purified from hydrolyzed peptides and native protein molecules.

Surface Properties of Protein-Polyelectrolyte Solutions. Impact of Polyelectrolyte Hydrophobicity.

The strong influence of an amphiphilic polyelectrolyte, poly(,-diallyl--hexyl--methylammonium chloride), on the surface properties of solutions of globular proteins (lysozyme, β-lactoglobulin, bovine serum albumin, and green fluorescent protein) depends on the protein structure and allows elucidation of the contribution of hydrophobic interactions in the protein-polyelectrolyte complex formation at the liquid-gas interface. At the beginning of adsorption, the surface properties are determined by the unbound amphiphilic component, but the influence of the protein-polyelectrolyte complexes of high surface activity increases at the approach to equilibrium. The kinetic dependencies of the dilational dynamic surface elasticity with one or two local maxima give a possibility to distinguish clearly between different steps of the adsorption process and to trace the formation of the distal region of the adsorption layer.

DNA Penetration into a Lysozyme Layer at the Surface of Aqueous Solutions.

The interactions of DNA with lysozyme in the surface layer were studied by performing infrared reflection-absorption spectroscopy (IRRAS), ellipsometry, surface tensiometry, surface dilational rheology, and atomic force microscopy (AFM). A concentrated DNA solution was injected into an aqueous subphase underneath a spread lysozyme layer. While the optical properties of the surface layer changed fast after DNA injection, the dynamic dilational surface elasticity almost did not change, thereby indicating no continuous network formation of DNA/lysozyme complexes, unlike the case of DNA interactions with a monolayer of a cationic synthetic polyelectrolyte.

Spread Layers of Lysozyme Microgel at Liquid Surface.

The spread layers of lysozyme (LYS) microgel particles were studied by surface dilational rheology, infrared reflection-absorption spectra, Brewster angle microscopy, atomic force microscopy, and scanning electron microscopy. It is shown that the properties of LYS microgel layers differ significantly from those of ß-lactoglobulin (BLG) microgel layers. In the latter case, the spread protein layer is mainly a monolayer, and the interactions between particles lead to the increase in the dynamic surface elasticity by up to 140 mN/m.

DNA Interaction with a Polyelectrolyte Monolayer at Solution-Air Interface.

The formation of ordered 2D nanostructures of double stranded DNA molecules at various interfaces attracts more and more focus in medical and engineering research, but the underlying intermolecular interactions still require elucidation. Recently, it has been revealed that mixtures of DNA with a series of hydrophobic cationic polyelectrolytes including poly(,-diallyl--hexyl--methylammonium) chloride (PDAHMAC) form a network of ribbonlike or threadlike aggregates at the solution-air interface. In the present work, we adopt a novel approach to confine the same polyelectrolyte at the solution-air interface by spreading it on a subphase with elevated ionic strength.

β-Lactoglobulin Adsorption Layers at the Water/Air Surface: 3. Neutron Reflectometry Study on the Effect of pH.

Several characteristics of β-lactoglobulin (BLG) layers adsorbed at the air/water interface exhibit a strong pH dependence, but our knowledge on the underlying structure-property relations is still fragmental. Here, we therefore extend our recent studies by neutron reflectometry (NR) and provide a comprehensive overview through direct measurements of the surface excess Γ and the layers' molecular structure. This enables comparison with available literature data to draw general conclusions.

Biophysical Correlates on the Composition, Functionality, and Structure of Dendrimer-Liposome Aggregates.

Interaction between negatively charged liposomes and cationic polyamidoamine dendrimers of different generations was investigated through size, zeta potential, turbidity, electron microscopy, atomic force microscopy, fluorescence spectroscopy, and calorimetric studies. Liposomes with the binary combination of 1,2-dipalmitoyl--glycero-3-phosphatidylcholine (DPPC) + dihexadecyl phosphate, DPPC + 1,2-dimyristoyl--glycero-3-phosphoglycerol, DPPC + 1,2-dipalmitoyl--glycero-3-phosphate, and DPPC + 1,2-dipalmitoyl--glycero-3-phosphoethanol were stable up to 60 days. The electrostatic nature of dendrimer-lipid bilayer interaction was evidenced through charge neutralization and subsequent reversal upon added dendrimer to liposome.

Dynamic Surface Properties of Mixed Dispersions of Silica Nanoparticles and Lysozyme.

The surface properties of mixed aqueous dispersions of lysozyme and silica nanoparticles were studied using surface-sensitive techniques in order to gain insight into the mechanism of the simultaneous adsorption of protein/nanoparticle complexes and free protein as well as the resulting layer morphologies. The properties were first monitored in situ during adsorption at the air/water interface using dilatational surface rheology, ellipsometry, and Brewster angle microscopy. Two main steps in the evolution of the surface properties were identified.

Dynamic Surface Properties of Fullerenol Solutions.

Application of dilational surface rheology, surface tensiometry, ellipsometry, Brewster angle, and transmission electron and atomic force microscopies allowed the estimation of the structure of the adsorption layer of a fullerenol with a large number of hydroxyl groups, C(OH) ( X = 30 ± 2). The surface properties of fullerenol solutions proved to be similar to the properties of dispersions of solid nanoparticles and differ from those of the solutions of conventional surfactants and amphiphilic macromolecules. Although the surface activity of fullerenol is not high, it forms adsorption layers of high surface elasticity up to 170 mN/m.

Orcinol Glucoside Loaded Polymer - Lipid Hybrid Nanostructured Lipid Carriers: Potential Cytotoxic Agents against Gastric, Colon and Hepatoma Carcinoma Cell Lines.

Purpose: Orcinol glucoside (OG) - loaded nanostructured lipid carrier (NLC), coated with polyethylene glycol-25/55-stearate (PEG-25/55-SA), were explored for delivering OG to improve in vitro cytotoxicity against gastrointestinal tract (GIT), colon and hepatoma carcinoma cell lines. It is being expected that the PEGylated formulations would possess the sustainability in withstanding the adverse physiological extremities like the most significant metabolic activities and phase I / II enzymatic activities in the intestines.

Methods: NLCs were prepared using tristearin, oleic acid and PEG-25/55-stearate by hot homogenization-ultrasonic dispersion; characterized by DLS, TEM, SEM, AFM, entrapment efficiency and drug loading capacity studies.

Adsorption kinetics of heptadecafluoro-1-nonanol: Phase transition and mixed control.

Hypothesis: The adsorption kinetics of heptadecafluoro-1-nonanol (CHFOH) onto a clean air-water interface at low surfactant concentrations (equilibrium surface tension, γ(C) > 65 mN/m) has been reported, and the controlling mechanism was found to be mixed diffusive-kinetic controlled (Kuo et al., JCIS 402 (2013) 131). However, it remains to be determined what the adsorption kinetics are at higher concentrations.

Adsorption of Denaturated Lysozyme at the Air-Water Interface: Structure and Morphology.

The application of protein deuteration and high flux neutron reflectometry has allowed a comparison of the adsorption properties of lysozyme at the air-water interface from dilute solutions in the absence and presence of high concentrations of two strong denaturants: urea and guanidine hydrochloride (GuHCl). The surface excess and adsorption layer thickness were resolved and complemented by images of the mesoscopic lateral morphology from Brewster angle microscopy. It was revealed that the thickness of the adsorption layer in the absence of added denaturants is less than the short axial length of the lysozyme molecule, which indicates deformation of the globules at the interface.

Effects of Aggregate Charge and Subphase Ionic Strength on the Properties of Spread Polyelectrolyte/Surfactant Films at the Air/Water Interface under Static and Dynamic Conditions.

We demonstrate the ability to tune the formation of extended structures in films of poly(sodium styrenesulfonate)/dodecyltrimethylammonium bromide at the air/water interface through control over the charge/structure of aggregates as well as the ionic strength of the subphase. Our methodology to prepare loaded polyelectrolyte/surfactant films from self-assembled liquid crystalline aggregates exploits their fast dissociation and Marangoni spreading of material upon contact with an aqueous subphase. This process is proposed as a potential new route to prepare cheap biocompatible films for transfer applications.

Formation of protein/surfactant adsorption layer as studied by dilational surface rheology.

The review discusses the mechanism of formation of protein/surfactant adsorption layers at the liquid - gas interface. The complexes of globular proteins usually preserve their compact structure a low surfactant concentrations. Therefore a simple kinetic model of the adsorption of charged compact nanoparticles is discussed first and compared with experimental data.

Phase Transitions in DNA/Surfactant Adsorption Layers.

The adsorption layers of complexes between DNA and oppositely charged surfactants dodecyltrimethylammonium bromide (DTAB) and cetyltrimethylammonium bromide (CTAB) at the solution/air interface were studied with surface tensiometry, dilational surface rheology, atomic force microscopy, Brewster angle microscopy, infrared absorption-reflection spectroscopy, and ellipsometry. Measurements of the kinetic dependencies of the surface properties gave a possibility to discover the time intervals corresponding to the coexistence of two-dimensional phases. One can assume that the observed phase transition is of the first order, unlike the formation of microaggregates in the adsorption layers of mixed solutions of synthetic polyelectrolytes and surfactants.

Double-Tailed Cystine Derivatives as Novel Substitutes of Phospholipids with Special Reference to Liposomes.

Cystine-based gemini surfactants with dodecyl, tetradecyl, hexadecyl, and octadecyl hydrocarbon chains were synthesized, and their interactions with unsaturated (soy phosphatidylcholine, SPC)/saturated (hydrogenated SPC, HSPC) soy phosphatidylcholines in the forms of a monolayer and a model liposome were estimated for different combinations of the components in the mixed systems. Studies of Langmuir monolayers at the air-aqueous buffer interface revealed condensation of the monomolecular films with the addition of surfactants. The effect of surfactants decreased according to the following order: octadecyl > hexadecyl > tetradecyl > dodecyl homologs.

Influence of Lipid Core Material on Physicochemical Characteristics of an Ursolic Acid-Loaded Nanostructured Lipid Carrier: An Attempt To Enhance Anticancer Activity.

The impact of saturation and unsaturation in the fatty acyl hydrocarbon chain on the physicochemical properties of nanostructured lipid carriers (NLCs) was investigated to develop novel delivery systems loaded with an anticancer drug, ursolic acid (UA). Aqueous NLC dispersions were prepared by a high-pressure homogenization-ultrasonication technique with Tween 80 as a stabilizer. Mutual miscibility of the components at the air-water interface was assessed by surface pressure-area measurements, where attractive interactions were recorded between the lipid mixtures and UA, irrespective of the extent of saturation or unsaturation in fatty acyl chains.

Polyelectrolyte/surfactant films spread from neutral aggregates.

We describe a new methodology to prepare loaded polyelectrolyte/surfactant films at the air/water interface by exploiting Marangoni spreading resulting from the dynamic dissociation of hydrophobic neutral aggregates dispensed from an aqueous dispersion. The system studied is mixtures of poly(sodium styrene sulfonate) with dodecyl trimethylammonium bromide. Our approach results in the interfacial confinement of more than one third of the macromolecules in the system even though they are not even surface-active without the surfactant.