Dynamic studies of the formation of model lipid membranes on highly curved lightguiding nanowires.

Supported lipid bilayers (SLBs) emulate the cell membrane and its functions. On flat surfaces, SLBs are formed by the adsorption and collapse of vesicles into SLB patches. They grow and merge, while reducing their exposed hydrophobic edges, until a mobile SLB is formed. However, curved surfaces can hinder SLB formation by mechanisms not fully understood.

Here, we form SLBs on vertical arrays of lightguiding semiconductor nanowires (NWs) of high convexity. They support waveguide modes, providing fluorescence signal enhancement (1-2 orders of magnitude) and higher signal-to-noise ratio than flat surfaces. Using real-time surface-sensitive fluorescence, the SLB formed at a faster rate on lightguiding NWs than on planar silica controls. Individual vesicle rupture and fusion events were detected when measuring single nanowires, and at high framerates, individual lipids diffusing in the SLB could be resolved as fast signal fluctuations.

We propose that the SLB starts forming on the flat space between NWs, while the higher curvature limits vesicle rupture on NWs. When reaching the NWs’ feet, the patches will expand along the NW circumference, since the hydrophobic edge remains constant. This is accelerated by the still unruptured vesicles on the NW.

These results explain the SLB formation process on curved and nanostructured surfaces, showing the potential of lightguiding NWs to study dynamic membrane phenomena at a single molecule level.