Membrane Nanotubes Increase the Robustness of Giant Vesicles

Abstract

Giant unilamellar vesicles (GUVs) provide a direct connection between the nano-and the microregime. On the one hand, these vesicles represent biomimetic compartments with linear dimensions of many micrometers. On the other hand, the vesicle walls are provided by single molecular bilayers that have a thickness of a few nanometers and respond sensitively to molecular interactions with small solutes, biopolymers, and nanoparticles. These nanoscopic responses are amplified by the GUVs and can then be studied on much larger scales. Therefore, GUVs are increasingly used as a versatile research tool for basic membrane science, bioengineering, and synthetic biology. Conventional GUVs have one major drawback, however: they have only a limited capability to cope with external perturbations such as osmotic inflation, adhesion, or micropipette aspiration that tend to rupture the membranes. In contrast, cell membranes tolerate the same kinds of mechanical perturbations without rupture because the latter membranes are coupled to reservoirs of membrane area. Here, we introduce GUVs with membrane nanotubes as model systems that include such area reservoirs. To demonstrate the increased robustness of these tubulated vesicles, we use micropipette aspiration and changes in the osmotic conditions applied to phospholipid membranes doped with the glycolipid GM1. A quantitative comparison between theory and experiment reveals that the response of the GUVs is governed by the membranes' spontaneous tension, a curvature-elastic material parameter that describes the bilayer asymmetry on the nanoscale. Because of their increased robustness, GUVs with nanotubes represent improved research tools for membrane science, in general, with potential applications as storage and delivery systems and as cell-like microcompartments in bioengineering, pharmacology, and synthetic biology.

Mechanical characterization of vesicles and cells: A review

“…More recently, GUVs with nanotubes embedded on the membrane surface was characterized using MA by Bhatia et al. . Although those GUVs did not have any internal structure like cytoskeleton or organelles, they behaved like a cell membrane due to the increase in membrane stiffness owing to the embedded nanotubes on the surface.…”

Reconstitution of immune cell interactions in free-standing membranes

“…Reductionist in vitro reconstitution technologies are finding widespread use for analysing the biophysical basis of complex cellular processes (Jorgensen et al, 2017, Liu andFletcher, 2009). GUVs have found applications in a broad range of fields, being used to probe many aspects of cell biology (Kahya, 2010, Bhatia et al, 2018, Prevost et al, 2017, Dubavik et al, 2012, Sezgin et al, 2015a, Richmond et al, 2011. Here, we presented a free-standing GUV-based membrane system with the potential to yield important insights into the spatiotemporal basis of immune cellcell interactions and lymphocyte activation.…”

Giant Vesicles with Encapsulated Magnetic Nanowires as Versatile Carriers, Transported via Rotating and Nonhomogeneous Magnetic Fields

“…On the other hand, the use of nanowires, with a diameter of a few hundreds of nanometers, minimizes the size of the actuated component in one of the dimensions, which can be crucial in the transport of the carrier through confined geometries. With this purpose in mind, relatively inextensible bilayers are transformed into highly deformable membranes by incorporating a nonionic surfactant with a lower packing parameter into the bilayer membrane . Amphiphilic molecules change the dynamics and structure of the bilayer, accumulating at the most stressed sites in the membrane and lowering the energetic cost of its deformation .…”

“…With this purpose in mind, relatively inextensible bilayers are transformed into highly deformable membranes by incorporating a nonionic surfactant with a lower packing parameter into the bilayer membrane. [37,38] Amphiphilic molecules change the dynamics and structure of the bilayer, accumulating at the most stressed sites in the membrane and lowering the energetic cost of its deformation. [24,38,39] The mechanical deformable biohybrid capsules allow for the manipulation and transport of molecules in a protective environment, through entangled paths, without requiring direct contact or chemical binding.…”