Probing Biointerfaces: Electrokinetics
Unravelling interrelations between charge, structure and biomolecular interactions defines an important analytical challenge in the development of new biomaterials. Theory and experimental techniques have been extended to explore processes occurring upon contact of polymeric biomaterials with aqueous environments. Significant progress was achieved in the quantitative reconstruction of streaming current data applying recent theories for the electrohydrodynamics of diffuse soft planar interfaces. Here, we review experimental approaches and theory to analyze the charging and structural changes of soft planar films in dependence on solution pH, salt concentration or temperature. Furthermore, we present and discuss data for stimuli-responsive polymer films and biohybrid hydrogel layers that demonstrate how the combination of streaming current, surface conductivity and swelling measurements allows for a comprehensive understanding of electrostatic and structural properties of these materials. In a third example we show how the combined application of fluorescence microscopy and electrokinetics provides new insights into fluidity modulations of phospholipid bilayers by electrolyte ions. Finally, we discuss potential future developments in the investigation of electrosurface phenomena.