Cationic lipid absorption on titanium: a counterion-mediated bilayer-to-lipid-tubule-network transition.

By carefully tuning the screening effects of monovalent salt in solution, it is possible to control the formation of different lipid morphologies on a titanium dioxide substrate. A transition from an absorbed vesicle layer to fluid lipid bilayers is observed as a function of monovalent salt concentration in solution, and, above a threshold salt concentration, a network of lipid tubules with a fascinating distorted-hexagonal structure is formed in two dimensions on the substrate. We present fluorescence microscopy data for these different morphologies, confirming the connectivity and fluidity of the bilayers and tubules.