Understanding How Membrane Surface Charge Influences Lipid Bicelle Adsorption onto Oxide Surfaces.

The adsorption of two-dimensional bicellar disks onto solid supports is an emerging fabrication technique to form supported lipid bilayers (SLBs) that is efficient and requires minimal sample preparation. To date, nearly all relevant studies have focused on zwitterionic lipid compositions and silica-based surfaces, and extending the scope of investigation to other lipid compositions and surfaces would improve our understanding of application possibilities and underpinning formation processes. Herein, using the quartz crystal microbalance-dissipation technique, we systematically investigated the adsorption of charged lipid bicelles onto silicon dioxide, titanium oxide, and aluminum oxide surfaces. Depending on the lipid composition and substrate, we observed different adsorption pathways, including (i) SLB formation via one- or two-step adsorption kinetics, (ii) monotonic adsorption without SLB formation, and (iii) negligible adsorption. On each substrate, SLB formation could be achieved with particular lipid compositions, whereas the trend in adsorption pathways varied according to the substrate and could be controlled by adjusting the bicelle-substrate interaction strength. To rationalize these findings, we discuss how electrostatic and hydration forces affect bicelle-substrate interactions on different oxide surfaces. Collectively, our findings demonstrate the broad utility of lipid bicelles for SLB formation while revealing physicochemical insights into the role of interfacial forces in controlling bicelle adsorption pathways.