Migration of phospholipid vesicles in response to OH⁻stimuli

Abstract

We demonstrate migration of phospholipid vesicles in response to a pH gradient. Upon simple micro-injection of a NaOH solution, the vesicles linearly moved to the tip of the micro-pipette and the migration velocity was proportional to the gradient of OH(-) concentration. Vesicle migration was characteristic of OH(-) ions and no migration was observed for monovalent salts or nonionic sucrose solutions. The migration of vesicles is quantitatively described by the surface tension gradient model where the hydrolysis of the phospholipids by NaOH solution decreases the surface tension of the vesicle. The vesicles move toward a direction where the surface energy decreases. Thus the chemical modification of lipids produces a mechanical force to drive vesicles.

pH sensing by lipids in membranes: The fundamentals of pH-driven migration, polarization and deformations of lipid bilayer assemblies

“…A line of our work has focused on studying the various effects of pH changes on giant unilamellar vesicle (GUV). We demonstrated that a pH change can induce vesicle migration and global deformation [5], as well as polarization in vesicles involving phase-separated membrane domains [6]. Furthermore, we showed that localized pH heterogeneities can induce local dynamical membrane deformations and developed a theoretical description of this phenomenon [7][8][9][10].…”

“…The flow, if existing, should occur inside the membrane and promote a visible vectorial motion of domains. Results on 2 types of vesicle migration phenomena were unable to detect such a motion on lipid vesicles which behaved as hard shells [5,66]. On the other hand, Marangoni effects have been found responsible for local deformations (see Section 4).…”

Dynamics of fatty acid vesicles in response to pH stimuli

“…8 The position of the micro-pipette tip is (0,0,0). 8 The position of the micro-pipette tip is (0,0,0).…”

“…The excess membrane produced by the fusion clung to the fused spherical vesicle as a black patch at the contact zone (arrow in Fig. 8 Thus effects of the pH stimuli on vesicles depend on the types of amphiphilic molecules that compose the vesicle. Dissipative particle dynamics simulations propose the following dynamics of tension-induced vesicle fusion.…”

“…Shear flow causes two characteristic motions of vesicles. 8 This behaviour might be due to the alkaline hydrolysis of the phospholipids, which decreases the local surface tension of the membrane, driving them toward the region where the surface tension is lower. In the presence of electric fields, vesicles are deformed and form transient pores due to the electric stress.…”