Effects of Flow and Bulk Vesicle Concentration on Supported Lipid Bilayer Formation

Supported lipid bilayers (SLBs) have been used extensively in a variety of biotechnology applications and fundamental studies exploring lipid behavior. Despite their widespread use, various physicochemical parameters have yet to be thoroughly investigated for their impact on SLB formation. In this work, we have studied the importance of flow in inducing the rupture of surface adsorbed chicken egg-derived l-a-phosphatidylcholine (egg PC) vesicles on silica and gold surfaces via quartz crystal microbalance with dissipation monitoring (QCM-D). On silica at 25 degrees C, egg PC vesicles were found to adsorb in a flattened configuration (similar to 13 nm thick, compared to bulk vesicle diameters of similar to 165 nm) but only undergo a transition to a stable SLB under flow conditions. In the absence of flow, an increase in system temperature to 37 degrees C was able to promote vesicle rupture and SLB formation on silica with a 10 times lower rupture time, compared to rupture under continuous flow (175 mu L/min flow rate). Gold surfaces, with their increased hydrophobicity, led to less vesicle flattening once adsorbed (structures similar to 60 nm thick), and did not support vesicle rupture or SLB formation, even at flow rates of up to 650 mu L/min. We also showed that, under continuous flow conditions, vesicle adsorption rates on silica surfaces follow Langmuir kinetics, with an inverse dependence on bulk vesicle concentration, while an empirical power law dependence of vesicle rupture time on bulk vesicle concentration was observed. Ultimately, this work elicits fundamental insight into the importance of flow and bulk vesicle concentration in the adsorbed vesicle rupture process during SLB formation using QCM-D.