Interfacial Forces Dictate the Pathway of Phospholipid Vesicle Adsorption onto Silicon Dioxide Surfaces

Abstract

The pathway of vesicle adsorption onto a solid support depends on the material composition of the underlying support, and there is significant interest in developing material-independent strategies to modulate the spectrum of vesicle-substrate interactions on a particular surface. Herein, using the quartz crystal microbalance-dissipation (QCM-D) technique, we systematically investigated how solution pH and membrane surface charge affect vesicle adsorption onto a silicon dioxide surface. While vesicle adsorption and spontaneous rupture to form complete supported lipid bilayer (SLBs) occurred in acidic conditions, it was discovered that a wide range of adsorption pathways occurred in alkaline conditions, including (i) vesicle adsorption and spontaneous rupture to form complete SLBs, (ii) vesicle adsorption and spontaneous rupture to form incomplete SLBs, (iii) irreversible adsorption of intact vesicles, (iv) reversible adsorption of intact vesicles, and (v) negligible adsorption. In general, SLB formation became more favorable with increasingly positive membrane surface charge although there were certain conditions at which attractive electrostatic forces were insufficient to promote vesicle rupture. To rationalize these findings, we discuss how solution pH and membrane surface charge affect interfacial forces involved in vesicle-substrate interactions. Taken together, our findings present a comprehensive picture of how interfacial forces dictate the pathway of phospholipid vesicle adsorption onto silicon dioxide surfaces and offer a broadly applicable framework to characterize the interactions between phospholipid vesicles and inorganic material surfaces.

Hybrid Lipid-Polymer Bilayers: pH-Mediated Interactions between Hybrid Vesicles and Glass

“…These changes in frequency corresponded to a dramatic increase and then a decrease in acoustic dissipation to an equilibrium value of ΔD = 1 × 10 −6 , indicating a rigid film consistent with the adsorption-then-fusion of lipid vesicles to form an SLB. Performing the same experiment with vesicles in solutions at higher pH revealed three additional previously reported [11,15] pH-mediated QCM-D behaviors consistent with irreversible vesicle adsorption (pH = 10), reversible vesicle adsorption (pH = 11), and no adsorption (pH = 12). SLBs can be easily distinguished from adsorbed lipid vesicles by comparing the ∆f/n, ∆D, and estimated film thicknesses.…”

“…The limited number of reports on the interaction of hybrid and polymer vesicles with glass surfaces describe substantially different conclusions under very similar conditions (i.e., same pH)-from bilayer formation, to irreversible vesicle adsorption, to no interaction at all [22,23,26]. The range of reported results is possibly due to insufficient vesicle substrate interactions which-as demonstrated for lipid-only systems [11]-can be mediated by varying buffer pH. To our knowledge there has been no systematic study of the effects of buffer pH on hybrid vesicle adsorption and fusion.…”

“…In the years since first described by Tamm et al [10], the formation of lipid bilayers on siliceous surfaces is a thoroughly studied phenomenon and the literature presents a great number of insights into the process. For example, the interaction between lipid vesicles and glass substrates is highly dependent on pH due to the changes it induces on the surface charge of the substrate [11], resulting in outcomes that range from adsorbed vesicles to supported lipid bilayers (SLBs). In addition to pH, other factors that affect vesicle-substrate interaction include temperature, cation valency, osmotic pressure, vesicle concentration and flow conditions [12][13][14][15].…”

Nanoarchitectonic‐Based Material Platforms for Environmental and Bioprocessing Applications

“…QCM−D measurements revealed that using untreated vesicles to fabricate SLBs led to a higher number of defects indicative of unruptured vesicles. More recently, it was demonstrated that, by systematically varying solution pH and membrane surface charge, it is possible to control vesicle adsorption behavior on silicon dioxide surfaces . Five different pathways were identified, including (i) complete SLB formation, (ii) incomplete SLB formation, (iii) irreversible vesicle adsorption, (iv) reversible vesicle adsorption, or (v) no adsorption, and the experimental results were consistent with the corresponding trend in vesicle‐substrate interaction strength (Figure ).…”

Generation of Solvent‐Free 3D Lipid Structure Arrays on High Aspect Ratio Si Microwell Substrate

“…In particular, due to the stability limitations of synthetic lipid membranes, the focus has been on the formation of the lipid layer supported on solid substrates in the form of 1) lipid bilayers or monolayers directly deposited on the substrate [1][2][3][4] ; 2) tethered bilayer membranes on solid surfaces [5][6][7] ; and 3) suspended lipid bilayers over micro or nanoapertures. In particular, due to the stability limitations of synthetic lipid membranes, the focus has been on the formation of the lipid layer supported on solid substrates in the form of 1) lipid bilayers or monolayers directly deposited on the substrate [1][2][3][4] ; 2) tethered bilayer membranes on solid surfaces [5][6][7] ; and 3) suspended lipid bilayers over micro or nanoapertures.…”