Lipid Transfer between Charged Supported Lipid Bilayers and Oppositely Charged Vesicles

Abstract

The bidirectional transfer of phospholipids between a charged, supported lipid bilayer (SLB) on SiO(2) and oppositely charged, unilamellar vesicles was studied by means of quartz crystal microbalance with dissipation (QCM-D) and optical reflectometry techniques. SLBs and vesicles were prepared from binary mixtures of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) mixed with different fractions of either 1-palmitoyl-2-oleoyl-sn-glycero-3-[phospho-l-serine] (POPS) (negatively charged) or 1-palmitoyl-2-oleoyl-sn-glycero-3-ethylphosphocholine (POEPC) (positively charged). The interaction process consists of an attachment-transfer-detachment (ATD) sequence, where added vesicles first attach to and interact with the SLB, after which they detach, leaving behind a compositionally modified SLB and ditto vesicles. When the process is complete, there is no net addition or reduction of total lipid mass in the SLB, but lipid exchange has occurred. The time scale of the process varies from a few to many tens of minutes depending on the type of charged lipid molecule and the relative concentration of charged lipids in the two membranes. Electrostatically symmetric cases, where only the charge sign (but not the fraction of charged lipid) was reversed between the SLB and the vesicles, produce qualitatively similar but quantitatively different kinetics. The time scale of the interaction varies significantly between the two cases, which is attributed to a combination of the differences in the molecular structure of the lipid headgroup for the positively and the negatively charged lipids used, and to nonsymmetric distribution of charged lipids in the lipid membranes. The maximum amounts of attached vesicles during the ATD process were estimated to be 25-40% of a full monolayer of vesicles, with the precise amount depending on the actual charge fractions in the vesicles and the SLB. Interrupted vesicle exposure experiments, and experiments where the bulk concentration of vesicles was varied, show that vesicles in some cases may be trapped irreversibly on the SLB, when only partial transfer of lipid molecules has occurred. Additional supply of vesicles and further transfer induces detachment, when a sufficient amount of oppositely charged lipids has been transferred to the SLB, so that the latter becomes repulsive to the attached vesicles. Possible mechanistic scenarios, including monomer insertion and hemifusion models, are discussed. The observed phenomena and the actual SLB preparation process form a platform both for studies of various intermembrane molecular transfer processes and for modifying the composition of SLBs in a controlled way, for example, for biosensor and cell culture applications.

Peptide-membrane interactions of arginine-tryptophan peptides probed using quartz crystal microbalance with dissipation monitoring

“…In short, solutions were added to the crystal in the following order: PBS, PBS-MgCl 2 , liposomes freshly diluted in PBS-MgCl 2 , PBS-MgCl 2 and PBS. MgCl 2 was added to facilitate the formation of negatively charged membranes (Kunze et al 2009). For POPC membranes, the liposomes were diluted in PBS without further addition of MgCl 2 .…”

No Evidence for Spontaneous Lipid Transfer at ER–PM Membrane Contact Sites

“…Regarding non-vesicular lipid exchange, the simplest mechanisms can be described as spontaneous lipid desorption from the donor membrane, followed by diffusion within the aqueous phase and adsorption by the acceptor membrane (Ferrell et al 1985;Kunze et al 2009), also Electronic supplementary material The online version of this article (doi:10.1007/s00232-015-9845-2) contains supplementary material, which is available to authorized users. called spontaneous lipid transfer (SLT) (Brown 1992;Lev 2012).…”

“…Here, the overall transfer kinetics is largely limited by contact establishment. Evidence for such a mechanism is provided by analysis of (i) transfer between charged vesicles and supported lipid bilayers (Solon et al 2006;Kunze et al 2009; for a detailed discussion on models see Kunze et al 2009) (ii) PC transport from donor liposomes to acceptor liposomes or cells (Jones and Thompson 1989;Longmuir and Malinick 1989;Jones and Thompson 1990) or (iii) cholesterol transfer from red blood cells to acceptor membranes (Steck et al 1988), prompting the suggestion that mechanisms independent from vesicular transport or LTPs are important for membrane biogenesis or lipid homeostasis (Jones and Thompson 1989;Lev 2010;Steck et al 2002;Kunze et al 2009;Lev 2012).…”

Amino acid based amphiphilic copolymer micelles as carriers of non-steroidal anti-inflammatory drugs: Solubilization, in vitro release and biological evaluation

“…is facilitated due to the presence of interfacial lipid layer (Kunze et al, 2009). Therefore, the polymer-based drug or vaccine delivery systems have attracted much attention due to their ability to perform multiple critical functions as mentioned above.…”