Interfaces and interphases are a vital part of everyday life—since the influence of their proximity might change considerably the behaviour of systems studied. The ability to study motion on the nanometre scale is essential for the understanding of transport phenomena to and from surfaces, thin films or membranes. It is indispensable to have analytical methods with spatio-temporal resolution adapted to these problems and which are non-invasive to obtain untainted results. The small dimensions lead to weak signals and therefore we need experimental setups which are able to amplify them. Here we describe a dynamic light scattering experiment where the evanescent part of waveguide modes is used as the source of light. Using waveguide modes increased the signal-to-noise ratio by a factor of 8 compared to evanescent waves generated by total internal reflection and it allows adjusting the spatial resolution near the interface in situ. This technique monitors changes of the waveguide surface as e.g. adsorption to it.

Polymer-supported bilayer lipid membranes offer great opportunities for the investigation of functional membrane proteins. Here we present a new approach in this direction by introducing a thin hydrogel layer as a soft ‘cushion’ on indium–tin oxide (ITO), providing a smooth, functional surface to form the protein-tethered BLM (ptBLM). ITO was used as a transparent electrode, enabling simultaneous implementation of electrochemical and optical waveguide techniques. The hydrogel poly(N-(2-hydroxyethyl)acrylamide-co-5-acrylamido-1-carboxypentyl-iminodiacetate-co-4-benzoylphenyl methacrylate) (P(HEAAm-co-NTAAAm-co-MABP)) was functionalized with the nickel chelating nitrilotriacetic acid (NTA) groups, to which cytochrome c oxidase (CcO) from Paracoccus denitrificans was bound in a well defined orientation via a his-tag attached to its subunit I. Given that the mesh size of P(HEAAm-co-NTAAAm-co-MABP) was smaller than the protein size, binding to the hydrogel occurred only on the top of the layer. The lipid bilayer was formed around the protein by in situdialysis. Electrochemical impedance spectroscopy showed good electrical sealing properties with a resistance of ∼1 MΩ cm2. Furthermore, surface plasmon resonance optical waveguide spectroscopy (SPR/OWS) indicated an increased anisotropy of the system after formation of the lipid bilayer. Cyclic voltammetry in the presence of reduced cytochrome c demonstrated that CcO was incorporated into the gel-supported ptBLM in a functionally active form.