Interfacial Free Energies of Cells and Polymers in Aqueous Media

Abstract

The interfacial free energy at the surface of cells in aqueous media, γCM determines the free energy of adhesion and the equilibrium constant for adhesion not only between different cells but also between cells and polymer surfaces. Previously described methods for measuring contact angles on cells in polymer containing, biphasic aqueous media (Biochim. Biophys. Acta. 602, 269, 1980; 640, 557, 1980) have been extended to provide values of γCM for cells in physiological media. To do this, an empirical equation of state was developed to describe the relations between contact angles and interfacial free energies in 3 component systems consisting of 2 fluids (gas or liquid) and one solid. In such systems, the bulk phase (gas or liquid) is designated “B”, the test droplet (liquid) is designated “D” and the solid phase is designated “S”. The contact angle between the drop and the solid when both are immersed in the bulk fluid is given by θ. The equation which was developed thus relates measured contact angles and bulk fluid-drop interfacial free energies, γBD to both of the solid-liquid interfacial free energies γSB, and γSD. This was used to determine cell-medium interfacial free energies from contact angle data. Cell-medium interfacial free energies in polyethyleneglycol-dextran biphasic media, and the polymer concentrations in these media were extrapolated to give γCM in polymer-free media.