Max Planck Institute for Colloid and Interface Science

Germany

Max Planck Institute for Colloid and Interface Science

Germany
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Bykov A.G.,Saint Petersburg State University | Gochev G.,Max Planck Institute for Colloid and Interface Science | Gochev G.,Bulgarian Academy of Science | Loglio G.,CNR Institute for Energetics and Interphases | And 3 more authors.
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2017

The dynamic surface properties of mixed monolayers of 1,2-Dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC) and negatively charged polystyrene particles (PS) of different size were investigated with the aim to model the interactions of particles with biointerfaces. Special attention was paid to the aggregation of the particles at the water/air interface. The particle aggregates have a weaker influence on the dynamic properties of DPPC monolayers as compared with non-aggregated particles because of a shorter three phase contact line. The incorporation of particles into a DPPC monolayer leads to disordering of the monolayer structure, decreases the changes of surface properties in the course of two-dimensional phase transitions and the dynamic surface elasticity of the condensed lipid film. The influence of particles on the properties of mixed monolayers depends strongly on the ratio of lipid molecules and particles, and decreases with the decrease of particle surface concentration. The Brewster angle microscopy gives direct evidence of the PS particle aggregation in the course of compression of mixed monolayers. © 2016 Elsevier B.V.


Ulaganathan V.,Max Planck Institute for Colloid and Interface Science | Ulaganathan V.,Nestlé | Retzlaff I.,Max Planck Institute for Colloid and Interface Science | Won J.Y.,Max Planck Institute for Colloid and Interface Science | And 6 more authors.
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2016

The dynamic surface pressure Π of air bubbles aging in buffered β-lactoglobulin (BLG) solutions containing various protein concentrations C BLG (10-9-10-4 M), pH (3-7) and buffer concentrations C buff (1, 10 and 100mM) was measured as a function of time t by bubble profile analysis tensiometry. Adsorption kinetics was studied by recording Π(t) data for 80000s and the final Π-values were used to construct the surface pressure isotherm Π(C BLG) for the pH values of 3, 5, 7 (C buff =10mM) and 6.3 (in pure water). On the basis of obtained kinetic and concentration dependencies the effect of pH on the protein surface activity was qualitatively analyzed. At constant C buff =10mM and relatively low protein concentrations (C BLG <10-8 M), BLG exhibits the shortest induction time τind and highest Π-values at pH 7 (negative net charge), in comparison to pH 5 and 3, whereas at sufficiently high protein concentrations (ca. C BLG >10-6 M) BLG is the most surface active at pH 5 (negligible net charge in the vicinity of the isoelectric point, pI ≈5.1). At constant C buff, BLG solutions with pH 3 show the lowest surface activity. The influence of the ionic strength (buffer concentration) of the solution on the dynamic Π was studied at a selected protein concentration of C BLG =10-5 M. The kinetics of adsorption is weakly affected by C buff for solutions with pH 5 and significantly enhanced by increasing C buff for solutions with pH≠pI. The effect of the chemical nature of the electrolyte was obtained for non-buffered aqueous BLG solutions (natural pH ∼6.3) at different concentrations of NaCl or CaCl2. It is demonstrated that the adsorption kinetics and the surface pressure isotherm of BLG at the water/air surface depend strongly on the protein effective charge, which is dictated by the solution pH and ionic strength. © 2016 Elsevier B.V.


Gochev G.,Max Planck Institute for Colloid and Interface Science | Gochev G.,Bulgarian Academy of Science | Retzlaff I.,Max Planck Institute for Colloid and Interface Science | Aksenenko E.V.,NASU A. V. Dumansky Institute of Colloid and Water Chemistry | And 2 more authors.
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2013

The adsorption behaviour of β-Lactoglobulin (BLG) at the air/water surface and the visco-elastic properties of the BLG adsorption layers are discussed in terms of quasi-equilibrium adsorption isotherms and equation of state gained by comparing a model with a set of experimental data obtained by bubble profile analysis tensiometry. The presented simultaneous characterization of the adsorption isotherm and the dilational visco-elasticity under dynamic and equilibrium conditions is based on measurements of the dynamic surface pressure and its response to sinusoidal bubble area variations. The thermodynamic model was applied to the set of experimental data under the assumptions of monolayer compressibility, surface dimerization and development of a secondary layer. The effect of the bubble surface age on the adsorption isotherm and equation of state, and also on the visco-elastic characteristics is discussed and it allows concluding that the existence of a bilayer structure, which is formed beyond a certain protein adsorption, is responsible for the observed relaxation processes. © 2013 Elsevier B.V.


Gochev G.,Max Planck Institute for Colloid and Interface Science | Gochev G.,Bulgarian Academy of Science
Current Opinion in Colloid and Interface Science | Year: 2015

The development of the topic of thin liquid films (TLF) stabilized by polymers in the last five years is outlined. Different types of TLF are considered, namely foam, emulsion (aqueous or oil) and wetting films. The reviewed results envelop a variety of polymeric surfactant and polymer(polyelectrolyte)/surfactant systems which have been probed by several methods, however mostly by the thin film pressure balance technique. The discussion addresses major factors which affect the surface forces in the TLF: type and charge of the polymer, type of the film interfaces (water/air, water/oil or water/solid), solvent conditions (salinity/polarity) and addition of a second surface active component. Linkage with studies on the corresponding single interfacial layers and macroscopic systems (foams and emulsions) is briefly discussed as well. © 2015 Elsevier Ltd.


Dan A.,Max Planck Institute for Colloid and Interface Science | Dan A.,University of Wisconsin - Madison | Gochev G.,Max Planck Institute for Colloid and Interface Science | Gochev G.,Bulgarian Academy of Science | Miller R.,Max Planck Institute for Colloid and Interface Science
Journal of Colloid and Interface Science | Year: 2015

Oscillating drop tensiometry was applied to study adsorbed interfacial layers at water/air and water/hexane interfaces formed from mixed solutions of β-lactoglobulin (BLG, 1. μM in 10. mM buffer, pH 7 - negative net charge) and the anionic surfactant SDS or the cationic DoTAB. The interfacial pressure Π and the dilational viscoelasticity modulus |. E| of the mixed layers were measured for mixtures of varying surfactant concentrations. The double capillary technique was employed which enables exchange of the protein solution in the drop bulk by surfactant solution (sequential adsorption) or by pure buffer (washing out). The first protocol allows probing the influence of the surfactant on a pre-adsorbed protein layer thus studying the protein/surfactant interactions at the interface. The second protocol gives access to the residual values of Π and |. E| measured after the washing out procedure thus bringing information about the process of protein desorption.The DoTAB/BLG complexes exhibit higher surface activity and higher resistance to desorption in comparison with those for the SDS/BLG complexes due to hydrophobization via electrostatic binding of surfactant molecules. The neutral DoTAB/BLG complexes achieve maximum elastic response of the mixed layer. Mixed BLG/surfactant layers at the water/oil interface are found to reach higher surface pressure and lower maximum dilational elasticity than those at the water/air surface. The sequential adsorption mode experiments and the desorption study reveal that binding of DoTAB to pre-adsorbed BLG globules is somehow restricted at the water/air surface in comparison with the case of complex formation in the solution bulk and subsequently adsorbed at the water/air surface. Maximum elasticity is achieved with washed out layers obtained after simultaneous adsorption, i.e. isolation of the most surface active DoTAB/BLG complex. These specific effects are much less pronounced at the W/H interface. © 2015 Elsevier Inc.


PubMed | Max Planck Institute for Colloid and Interface Science and Bulgarian Academy of Science
Type: | Journal: Journal of colloid and interface science | Year: 2015

Oscillating drop tensiometry was applied to study adsorbed interfacial layers at water/air and water/hexane interfaces formed from mixed solutions of -lactoglobulin (BLG, 1 M in 10 mM buffer, pH 7 - negative net charge) and the anionic surfactant SDS or the cationic DoTAB. The interfacial pressure and the dilational viscoelasticity modulus |E| of the mixed layers were measured for mixtures of varying surfactant concentrations. The double capillary technique was employed which enables exchange of the protein solution in the drop bulk by surfactant solution (sequential adsorption) or by pure buffer (washing out). The first protocol allows probing the influence of the surfactant on a pre-adsorbed protein layer thus studying the protein/surfactant interactions at the interface. The second protocol gives access to the residual values of and |E| measured after the washing out procedure thus bringing information about the process of protein desorption. The DoTAB/BLG complexes exhibit higher surface activity and higher resistance to desorption in comparison with those for the SDS/BLG complexes due to hydrophobization via electrostatic binding of surfactant molecules. The neutral DoTAB/BLG complexes achieve maximum elastic response of the mixed layer. Mixed BLG/surfactant layers at the water/oil interface are found to reach higher surface pressure and lower maximum dilational elasticity than those at the water/air surface. The sequential adsorption mode experiments and the desorption study reveal that binding of DoTAB to pre-adsorbed BLG globules is somehow restricted at the water/air surface in comparison with the case of complex formation in the solution bulk and subsequently adsorbed at the water/air surface. Maximum elasticity is achieved with washed out layers obtained after simultaneous adsorption, i.e. isolation of the most surface active DoTAB/BLG complex. These specific effects are much less pronounced at the W/H interface.

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