The role of van der Waals forces and hydrogen bonds in “hydrophobic interactions” between biopolymers and low energy surfaces

In a previous paper it was shown that negative interfacial tensions between predominantly monopolar surfaces (i.e., surfaces with mainly H-acceptor properties) and polar liquids are real phenomena. Such negative interfacial tensions do however decay rapidly. For miscible liquids, the decay of the interface is, in general, so rapid that it practically excludes measurement of interfacial tension. However, if one liquid is present in the form of a gel, and if the other liquid is placed as a drop upon the gel, there is often enough time to measure contact angles. This may be done at various concentrations of the liquid encased in the gel, and an extrapolation made to zero concentration of the gelling agent. With this method we found the existence of negative interfacial tensions at liquid/liquid interfaces.

Estimation of the polar parameters of the surface tension of liquids by contact angle measurements on gels

An energy storage device includes a first electrode comprising a first material and a second electrode comprising a second material, at least a portion of the first and second materials forming an interpenetrating network when dispersed in an electrolyte, the electrolyte, the first material and the second material are selected so that the first and second materials exert a repelling force on each other when combined. An electrochemical device, includes a first electrode in electrical communication with a first current collector; a second electrode in electrical communication with a second current collector; and an ionically conductive medium in ionic contact with said first and second electrodes, wherein at least a portion of the first and second electrodes form an interpenetrating network and wherein at least one of the first and second electrodes comprises an electrode structure providing two or more pathways to its current collector.

Battery structures, self-organizing structures and related methods

We owe a great debt to W. A. Zisman and his colleagues at the Naval Research Laboratory for their extensive, pioneering work that opened up the field of contact angles and made possible the development of the modern theory of wetting and adhesion. Their data on the wetting of solids by apolar liquids and by hydrogen bonding liquids pointed the way to the recent introduction of a theory of hydrogen bond interactions across interfaces. We will devote this chapter to a review of this new theory.

The Modern Theory of Contact Angles and the Hydrogen Bond Components of Surface Energies

Adsorption isotherms of four plasma proteins (fibrinogen, IgG, human serum albumin, and bovine serum albumin) using four different types of small particles as substrates (siliconized glass, Teflon, polyvinylchloride, and Nylon-6, 6) are reported. The suspending liquid medium was phosphate-buffered saline, with a surface tension higher than that of any of the proteins. In keeping with the thermodynamic expectations for these systems, protein adsorption decreases for all solids in sequence from fibrinogen (the most hydrophobic) to IgG, human serum albumin, and bovine serum albumin (the most hydrophilic). Furthermore, the extent of protein adsorption also decreases from the low surface tension (hydrophobic) to the higher surface tension solids, again as expected on thermodynamic grounds. There is one minor yet interesting exception to the thermodynamic pattern: In spite of the slightly lower surface tension of siliconized glass, the extent of protein adsorption is slightly higher to Teflon than to siliconized glass. This result is attributed to the theoretically well known phenomenon of “screening”.

Protein adsorption to polymer particles: Role of surface properties

Applications of net repulsive van der Waals forces between different particles, macromolecules, or biological cells in liquids

Thermodynamic model considerations suggest that the adhesion of biological cells to polymeric surfaces depends on the relative magnitude of the surface tension γSV of the substrates, the surface tension γCV of the cells, and the surface tension γLV of the suspending liquid medium. Glutaraldehyde-fixed erythrocytes are identified as suitable model particles for such studies. Experimental results of the extent of erythrocyte adhesion from suspension of mixtures of buffer and varying amounts of dimethyl sulfoxide (DMSO) confirm qualitatively and in certain aspects quantitatively the thermodynamic predictions. Specifically, the prediction that the extent of cell adhesion should become independent of substrate surface tension when γLV = γCV is confirmed by experiment. On the other hand for this case the free energy of adhesion predicting zero cell adhesion is not experimentally confirmed completely. However, performing these experiments with distilled water rather than buffer reduces erythrocyte adhesion to a negligible level. It emerges that van der Waals interactions are, by a large margin, the most important forces involved in cell adhesion to polymer surfaces. Nevertheless, not only divalent cations (through bridging effects), but also monovalent cations play a certain, though limited, role.

Erythrocyte adhesion to polymer surfaces

Elution of human granulocytes from nylon fibers by means of repulsive van der Waals forces.

Platelet activation on agar/agarose gel surfaces: Variation correlated with casting technique and hydrophobic/hydrophilic balance as reflected in contact angle measurements

In der vorliegenden Untersuchung werden thermodynamische Uberlegungen auf zwei biologische Vorgange, namlich Phagocytose und Blutplattchenadhasion, letzteres als wichtigen Schritt in der Thrombose angewandt. Es werden einfache, thermodynamische Modelle entwickelt, die die relevanten Anderungen der Helmholtzschen freien Energie liefern fur die Inklusion von Bakterien durch Phagocytzellen, als auch fur die Adhasion von Blutplattchen an die Oberflache von Biowerkstoffen. Die in den Ausdrucken fur die Helmholtzsche freie Energie enthaltenen Grenzflachenspannungen konnen aus Randwinkeldaten mittels einer grenzflachenenergetischen Zustandsgleichung erhalten werden. Diein vitro durchgefuhrten Untersuchungen der Phagocytose zeigen, das hydrophobe Bakterien leichter phagocytiert werden als hydrophile Bakterien; das hier benutzte thermodynamische Modell erklart diese Verhaltensweise.

C.J Van Oss

Papers

Applications of net repulsive van der Waals forces between different particles, macromolecules, or biological cells in liquids

Erythrocyte adhesion to polymer surfaces

Elution of human granulocytes from nylon fibers by means of repulsive van der Waals forces.

Platelet activation on agar/agarose gel surfaces: Variation correlated with casting technique and hydrophobic/hydrophilic balance as reflected in contact angle measurements

[Thermodynamic aspects of phagocytosis and thrombosis (author's transl)].