Electrostatic Repulsion of Positively Charged Vesicles and Negatively Charged Objects

TL;DR

This paper explains how positively charged vesicles can repel negatively charged objects through a mechanism involving counterion aggregation, providing insights into experimental observations of electrostatic interactions.

Contribution

It introduces a novel mechanism where counterion aggregation causes positively charged vesicles to repel negatively charged objects, expanding understanding of electrostatic interactions in biological and colloidal systems.

Findings

Negatively charged objects can be repelled by positively charged vesicles.

Counterion aggregation leads to a net negative charge on the vesicle exterior.

The mechanism explains recent experimental results on surfactant vesicles.

Abstract

A positively charged, mixed bilayer vesicle in the presence of negatively charged surfaces (for example, colloidal particles) can spontaneously partition into an adhesion zone of definite area, and another zone that repels additional negative objects. Although the membrane itself has nonnegative charge in the repulsive zone, negative counterions on the interior of the vesicle spontaneously aggregate there, and present a net negative charge to the exterior. Beyond the fundamental result that oppositely charged objects can repel, our mechanism helps explain recent experiments on surfactant vesicles.