Stable Membraneless Complex Coacervate Microdroplets

Complex coacervate microdroplets are membraneless compartments that selectively sequester biological molecules from their surroundings and enhance bioreactions. Yet, their use as protocell models and bioreactors has been limited owing to a lack of feasible strategies to prevent their uncontrolled coalescence. Herein, we introduce an approach to mitigate coalescence of complex coacervate microdroplets using comb polyelectrolytes as stabilizers while retaining the membraneless coacervate-water interfaces, creating membraneless coacervate emulsions with months-long stabilities. Tunability of microdroplet size and stability is achieved by regulation of comb polyelectrolyte concentration and molecular weight. Importantly, the comb polyelectrolyte-stabilized coacervate microdroplets spontaneously sequester and retain proteins over extended periods. Moreover, enhanced catalytic activity of proteins and significant (up to 10-fold) acceleration of bioreactions is achieved in stabilized complex coacervate dispersions, even when stored for up to 48 hours. Our findings are expected to expand the utility of complex coacervate microdroplets as artificial protocells, encapsulants, and bioreactors, and also facilitate their use in pharmaceutical, agricultural, food, and cosmetics formulations.