D. O. Grigoriev

Dynamics of protein and mixed protein/surfactant adsorption layers at the water/fluid interface.

The adsorption behaviour of proteins and systems mixed with surfactants of different nature is described. In the absence of surfactants the proteins mainly adsorb in a diffusion controlled manner. Due to lack of quantitative models the experimental results are discussed partly qualitatively. There are different types of interaction between proteins and surfactant molecules. These interactions lead to protein/surfactant complexes the surface activity and conformation of which are different from those of the pure protein. Complexes formed with ionic surfactants via electrostatic interaction have usually a higher surface activity, which becomes evident from the more than additive surface pressure increase. The presence of only small amounts of ionic surfactants can significantly modify the structure of adsorbed proteins. With increasing amounts of ionic surfactants, however, an opposite effect is reached as due to hydrophobic interaction and the complexes become less surface active and can be displaced from the interface due to competitive adsorption. In the presence of non-ionic surfactants the adsorption layer is mainly formed by competitive adsorption between the compounds and the only interaction is of hydrophobic nature. Such complexes are typically less surface active than the pure protein. From a certain surfactant concentration of the interface is covered almost exclusively by the non-ionic surfactant. Mixed layers of proteins and lipids formed by penetration at the water/air or by competitive adsorption at the water/chloroform interface are formed such that at a certain pressure the components start to separate. Using Brewster angle microscopy in penetration experiments of proteins into lipid monolayers this interfacial separation can be visualised. A brief comparison of the protein adsorption at the water/air and water/n-tetradecane shows that the adsorbed amount at the water/oil interface is much stronger and the change in interfacial tension much larger than at the water/air interface. Also some experimental data on the dilational elasticity of proteins at both interfaces measured by a transient relaxation technique are discussed on the basis of the derived thermodynamic model. As a fast developing field of application the use of surface tensiometry and rheometry of mixed protein/surfactant mixed layers is demonstrated as a new tool in the diagnostics of various diseases and for monitoring the progress of therapies.

New Method for Fabrication of Loaded Micro-and Nanocontainers: Emulsion Encapsulation by Polyelectrolyte Layer-by-Layer Deposition on the Liquid Core

A novel approach to the emulsion encapsulation was developed by combining the advantages of direct encapsulation of a liquid colloidal core with the accuracy and multifunctionality of layer-by-layer polyelectrolyte deposition. Experimental data obtained for the model oil-in-water emulsion confirm unambiguously the alternating PE assembly in the capsule shell as well as the maintenance of the liquid colloidal core. Two different mechanisms of capsule destruction upon interaction with the solid substrate were observed and qualitatively explained. The proposed method can be easily generalized to the preparation of oil-filled capsules in various oil/water/polyelectrolyte systems important in the field of pharmacy, medicine, and food industry.

Properties of mixed protein/surfactant adsorption layers

The adsorption isotherms, adsorption kinetics and surface rheological properties of β-lactoglobulin, β-casein, in the absence and presence of Tween 20 were measured. To study the adsorption process (isotherms and kinetics) at the water–air interface the pendant drop technique (axial drop shape analysis, ADSA), and ring tensiometry were used. The surface shear rheological parameters were measured with a torsion pendulum set-up. Also, data of the equilibrium film thickness and surface diffusion coefficients obtained from fluorescence recovery after photobleaching (FRAP) measurements are used to understand the competitive adsorption mechanism. The adsorption process and shear rheological behaviour of the studied systems show a rather complex behaviour which depends most of all on the systems composition. At high protein or surfactant content the behaviour is controlled by the main component while for the more mixed systems the adsorption process is complex and consists of partial adsorption, surfactant–protein interaction and protein rearrangement as a function of surface coverage. The results obtained illustrate that all these processes must be taken into account in future new theoretical models to be derived for such systems.

Polyelectrolyte complexes as a “smart” depot for self-healing anticorrosion coatings

Various types of “intelligent” self-healing anticorrosion coatings using stimuli-responsive behaviour of polyelectrolyte/inhibitor complexes are presented. Flat nanocomposite multilayers as well as colloidally-templated micro- and nanocarriers with incorporated inhibitor are employed as main building blocks for the formation of novel protective materials. The corrosion inhibitor is incorporated as a structural element (organic molecule), as an inorganic precipitate or in a porous inorganic particle. Being induced by local pH changes during corrosion development, polyelectrolyte/inhibitor complexes afford the unique ability of active feedback and sustained release of inhibitor exactly at the corrosion-damaged sites. Elimination of the corrosive attack returns the complex layer back into the sealed state, providing effective storage and consumption of inhibitor. Insertion of complex-based elements into the coating matrix not only allows the combination of passive and active corrosion protection but also imparts the self-healing properties.

Development of Nanoparticle Stabilized Polymer Nanocontainers with High Content of the Encapsulated Active Agent and Their Application in Water‐Borne Anticorrosive Coatings

A novel method for the encapsulation of organic active agents in nanoparticle-armored polymer composite nanocontainers (analog of Pickering emulsions) is introduced. The multifunctionality of the constituents allows a fabrication path that does not require auxiliary materials. Embedding the composite nanocontainers into a water-based alkyd resin and subsequent film formation yields a homogeneous polymer film doped with highly disperse composite nanocontainers. The resistance and self-healing of such a film on aluminium is enhanced.

Application of smart organic nanocontainers in feedback active coatings

The key element of a novel generation of protective coatings with feedback activity to the external and internal triggers is an embedding of smart nano- or microcontainers into the coating matrix. When implanted in various types of coating matrices, these containers with a sensitive polymeric shell and water or oil interior provide controlled release of the encapsulated active materials upon action by external stimuli. In the article at hand we survey recent achievements in this new field of development and application of filled sensitive containers in biomedical and self-healing protective coatings. Diverse stimuli-responsive and self-repairing systems (implants, matrices, coatings) in different branches, from medicine to corrosion protection, are presented and their advantages as well as drawbacks are discussed in terms of the field-specific protection efficiency.

Equilibrium of Adsorption of Mixed Milk Protein/Surfactant Solutions at the Water/Air Interface

Ellipsometry and surface profile analysis tensiometry were used to study and compare the adsorption behavior of beta-lactoglobulin (BLG)/C10DMPO, beta-casein (BCS)/C10DMPO and BCS/C12DMPO mixtures at the air/solution interface. The adsorption from protein/surfactant mixed solutions is of competitive nature. The obtained adsorption isotherms suggest a gradual replacement of the protein molecules at the interface with increasing surfactant concentration for all studied mixed systems. The thickness, refractive index, and the adsorbed amount of the respective adsorption layers, determined by ellipsometry, decrease monotonically and reach values close to those for a surface covered only by surfactant molecules, indicating the absence of proteins from a certain surfactant concentration on. These results correlate with the surface tension data. A continuous increase of adsorption layer thickness was observed up to this concentration, caused by the desorption of segments of the protein and transforming the thin surface layer into a rather diffuse and thick one. Replacement and structural changes of the protein molecules are discussed in terms of protein structure and surface activity of surfactant molecules. Theoretical models derived recently were used for the quantitative description of the equilibrium state of the mixed surface layers.

Adsorption of alkyl dimethyl phosphine oxides at the solution/air interface.

Abstract The surface tension isotherms were measured for homologous series of alkyl dimethyl phosphine oxides using different experimental techniques: maximum bubble pressure technique, drop volume technique and ring tensiometry. The adsorption data obtained for the surfactants with hydrocarbon chains from 8 to 16 alkyl groups are interpreted by a reorientation isotherm assuming two possible partial molar surface areas of surfactant molecules, i.e. states with maximum ( ω 1 ) and minimum ( ω 2 ) surface area. The lower homologues ( n ⩽13) of C n DMPO do not adsorb in the state with the large molar area, while the molecules with long alkyl chains ( n ⩾14) adsorb in both states. The area values determined from the experimental isotherms agree well with those calculated from the molecular geometry.

Polyfunctional active coatings with damage-triggered water-repelling effect

New smart anticorrosion coatings based on a combination of passive and active parts were developed. The active part is presented by polyurethane microcontainers loaded with alkoxysilanes possessing a long hydrophobic tail. High efficiency of the coating is achieved by the combination of passivating and water-repelling properties of the loaded material.

Impact of Globule Unfolding on Dilational Viscoelasticity of β-Lactoglobulin Adsorption Layers

The dynamic surface dilational elasticity, surface pressure, and adsorbed amount of the mixed solutions of beta-lactoglobulin and guanidine hydrochloride were measured as a function of surface age and denaturant concentration. It was shown that the conformational transition from compact globules to disordered protein molecules in the surface layer leads to strong changes in the surface elasticity kinetic dependencies and thereby can be easily detected by measuring the surface dilational rheological properties. The corresponding changes of the kinetic dependencies of the surface pressure and adsorbed amount are not so pronounced but correlate with the results on surface dilational elasticity.