Vesicle adhesion in the electrostatic strong-coupling regime studied by time-resolved small-angle X-ray scattering

• Published in: Soft matter Vol. 16; no. 17; pp. 4142 - 4154
• Main Authors: Komorowski, Karlo, Schaeper, Jannis, Sztucki, Michael, Sharpnack, Lewis, Brehm, Gerrit, Köster, Sarah, Salditt, Tim
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 06.05.2020
• Subjects: Adhesion; Calcium; Calcium ions; Charge density; Chemical Sciences; Coupling; Ions; Lipids; Microfluidics; Phase transitions; Small angle X ray scattering; Surface charge; Vesicles; X-ray scattering; Zinc; POISSON-BOLTZMANN
• ISSN: 1744-683X; 1744-6848; 1744-6848
• DOI: 10.1039/d0sm00259c

We have used time-resolved small-angle X-ray scattering (SAXS) to study the adhesion of lipid vesicles in the electrostatic strong-coupling regime induced by divalent ions. The bilayer structure and the interbilayer distance d w between adhered vesicles was studied for different DOPC:DOPS mixtures varying the surface charge density of the membrane, as well as for different divalent ions, such as Ca 2+ , Sr 2+ , and Zn 2+ . The results are in good agreement with the strong coupling theory predicting the adhesion state and the corresponding like-charge attraction based on ion-correlations. Using SAXS combined with the stopped-flow rapid mixing technique, we find that in highly charged bilayers the adhesion state is only of transient nature, and that the adhering vesicles subsequently transform to a phase of multilamellar vesicles, again with an inter-bilayer distance according to the theory of strong binding. Aside from the stopped-flow SAXS instrumentations used primarily for these results, we also evaluate microfluidic sample environments for vesicle SAXS in view of future extension of this work. We have used time-resolved small-angle X-ray scattering (SAXS) to study the adhesion of lipid vesicles in the electrostatic strong-coupling regime induced by divalent ions.