Responding double-porous lipid membrane: lyotropic phases in a polymer scaffold.

The large osmotic gradient over the outermost layer of human skin implies major structural changes along the gradient, which in turn affects transport. In particular, the possibility of phase changes introduces a non-linear element to the transport behaviour. We present a novel model membrane system to be used for studying these transport mechanisms, where we use a hydrophobic porous polymer membrane as a scaffold for lipid lyotropic phases. The polymer membrane provides mechanical robustness, but also prevents defects of the lipid lyotropic phases, and it can induce an orientation of anisotropic phases. We study the location, structure and phase behaviour of the confined phases. It is shown that this model membrane system allow for accurate measurements of transport through lipid membranes in the presence of different osmotic gradients. A theoretical description is evaluated and shows that this phenomenon can be understood in terms of the proposed mechanism of phase changes. The novel double-porous lipid membrane constitutes a mechanically robust system for studies in aligned systems, which is generally very difficult to achieve. This could have large implications for studies of transport processes in, e.g. skin and other biomembrane model systems.