Optimized pore geometry on silicon substrate surface for long time phospholipid cell membrane stability*

The study of artificial membranes composed by phospholipid bilayer on solid substrates has become a relevant way to gain insights into the physical behavior of cell membranes. In this work, using very high resolution ellipsometry (VHRE), was studied the behavior of lipid bilayers of DPPC deposited from their gas phase on porous silicon (pSi) substrates with different pore sizes. The film thickness was controlled during deposition, in situ, with VHRE. In a first step, it was necessary to optimize the pore depth that permits to obtain a reproducible ellipsometric signal for the bare, clean substrate. In the next step, we studied the lipid bilayers formation over different pore diameters to achieve membranes, which are stable during an extended period of time (several days) after hydration. Using VHRE and Stray Light Intensity (SLI) measurements, we observed for some characteristic substrate geometries changes in thickness and roughness of the lipid bilayers, related to phase transitions as a function of temperature, according to the literature.