Formation of Multiphase Complex Coacervates and Partitioning of Biomolecules within them.

Biological systems employ liquid-liquid phase separation to localize macromolecules and processes. The properties of intracellular condensates that allow for multiple, distinct liquid compartments and the impact of their coexistence on phase composition and solute partitioning are not well understood. Here, we generate two and three coexisting macromolecule-rich liquid compartments by complex coacervation based on ion pairing in mixtures that contain two or three polyanions together with one, two, or three polycations. While in some systems polyelectrolyte order-of-addition was important to achieve coexisting liquid phases, for others it was not, suggesting that the observed multiphase droplet morphologies are energetically favorable. Polyelectrolytes were distributed across all coacervate phases, depending on the relative interactions between them, which in turn impacted partitioning of oligonucleotide and oligopeptide solutes. These results show the ease of generating multiphase coacervates and the ability to tune their partitioning properties via the polyelectrolyte sharing inherent to multiphase complex coacervate systems.