BPS2026 – Formation of model membrane array by self-spreading of phospholipid bilayers and its kinetic analysis

Supported lipid bilayers (SLBs) have attracted interest as a model membrane platform for biophysical studies and biosensor applications. SLBs act as two-dimensional liquid and have lateral fluidity. It could have the potential advantages as the ultrathin medium of lateral transportation and separation of membrane-embedded molecules. Self-spreading is a spontaneous wetting phenomenon of a lipid bilayer from a condensed reservoir of liquid crystalline lipid bilayers on a solid surface. We recently studied self-spreading of SLBs in a framework of polymeric lipid bilayer as a model of directional lipid membrane flow. The polymeric bilayer was formed using a photopolymerizable diacetylene lipid, 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DiynePC) and worked as a framework stabilizing the fluid SLBs. The self-spreading SLBs elongated in the polymeric bilayer channels without penetrating into the polymeric bilayer regions. We analyzed the velocity of the self-spreading using a quasi-one-dimensional polymeric bilayer framework and compared with theoretical model based on energetic gain and frictional dissipation. The kinetics of self-spreading was also analyzed by varying its lipid compositions, the array design, and the ionic strength of the buffer. The spreading velocity of bilayers containing anionic phospholipid (phosphatidylserine and phosphatidic acid) was significantly reduced, suggesting lower energetic gain of wetting due to the electrostatic repulsion (glass surface is also negatively charged). On the other hand, bilayers containing cationic phospholipids (ethyl-phosphatidylcholine and DOTAP) did not enhance the spreading velocity. The asymmetric influences of charged lipids point to the complex interplay between the energetic gain and frictional drag. The obtained results show that directional lipid flow by self-spreading is influenced by the interactions between SLBs and the substrate. This information would be useful for molecular transportation using lipid flow.