Spatio-temporal control over complex coacervates using electrochemistry and electric fields

Coacervates are aqueous phases formed through liquid-liquid phase separation (LLPS). They are often used as mimics of membraneless organelles (MLOs) – liquid droplets that play different roles in cellular biology [1]. Since MLOs are dynamic (forming transiently, moving, changing properties, and responding to stimuli), there is a growing interest in bringing coacervates out-of-equilibrium as well [2]. Complex coacervates contain oppositely-charged polyelectrolytes, which makes them particularly susceptible to external electric fields [3]. Herein, we present two methods that provide spatio-temporal control over complex coacervates utilizing their interactions with electricity.

In the first project, we use an electrochemical potential to drive the out-of-equilibrium formation, movement and destruction of coacervate droplets, mimicking the dynamic properties of MLOs. Opposite electrochemical reactions control the formation and destruction of coacervates, while electrophoresis drives their mobility in the electric field. Overall, we have designed a system that can maintain a formation-destruction regime for several hours without the production of any waste.

In the second project, we focus on the electroemulsification of complex coacervates. Our results show that some coacervates can undergo splitting in weak electric fields (< 3 V/cm), leading to the emulsification of the material. This phenomenon can be controlled by tuning the composition of the coacervates, the ionic strength of the supernatant and the strength of the electric field. Altogether, this opens a possibility for control over the colloidal stability of complex coacervates.

References

1.     Donau, C. et al., “Active coacervate droplets as a model for membraneless organelles and protocells”, Nat Commun, 2020, 11, 5167.

2.     Slootbeek, A. D et al., “Growth, Replication and Division Enable Evolution of Coacervate Protocells”, Chem. Commun. 2022, 58 (80), 11183–11200.

3.     Agrawal, J. F. et al., “Manipulation of coacervate droplets with an electric field”, PNAS, 2022, 119, 32, e2203483119.