Emulsion macrophase transfer for stabilizing membraneless polyelectrolyte complex coacervate droplets*

In this experimental work, we explored the interfacial properties of membraneless polyelectrolyte complex coacervate droplets prepared in a controlled saline environment via emulsion macrophase transfer. We achieved stability against droplet coarsening in a variety of polyelectrolyte coacervates, demonstrating the generality of this phenomenon. When subjected to a compressional force, rather than coalescing, the droplets deformed and remained stable in non-spherical shapes suggesting an elastic interface. Rheological measurements show that there is only a little change in the viscoelastic properties of the complexes upon stabilization, preserving the liquid-like properties of these complexes. These droplets were stable for over 2 months at lab conditions and were thermally stable at elevated temperatures way beyond physiological conditions. The absence of an external membrane on these droplets conserved their excellent biomolecular diffusion and partitioning capabilities, promoting their application as artificial bioreactors mimicking cells. Some of these properties were explored using enzyme cascade reactions localized within the coacervate droplets.