A gel based on vesicle-vesicle adhesion induced by polyelectrolyte: from morphology to rheology

Phospholipid membranes are of great interest for encapsulation due to its outstanding barrier properties. Here we show that one can build an elastic solid with giant vesicles (1-30 mm diameter) that adhere to one another. A slight negative potential on the lipid membrane enables electrostatic attraction with polycations, which induces vesicle-vesicle adhesion. The vesicle adhesion leads to a macroscopic vesicle based gel that is >99% water but has a closed-cell structure. Shear rheology measurements show a low-frequency modulus of a few Pa and linear response extending to very large strains of approximately 0.7. We find that the vesicle adhesion strength and shear modulus can be tuned with polyelectrolyte concentration. We also find that the shear modulus does not scale with vesicle size as long as the adhesion strength is held constant. The vesicle gel system shows great potential as a soft-solid platform for a stimulus-responsive material that can deliver reagents on demand.