Stabilized Coacervate Microdroplets as a Platform for RNA Compartmentalization and Manipulation in Electric Fields

Coacervate microdroplets have been widely studied as protocell models due to their ability to grow, divide, and selectively concentrate biomolecules such as RNA. However, their rapid fusion and unrestricted molecular exchange pose a significant challenge to maintaining distinct genetic identities over time, making sustained evolutionary processes unfeasible. The rapid spread of parasitic RNA within coacervate populations could further hinder their potential role in prebiotic evolution. In this study, we demonstrate that exposure to distilled water, mimicking freshwater environments, induces the formation of electrostatic crosslinks at the droplet interface. These crosslinks effectively prevent droplet fusion indefinitely while also modulating the diffusion and compartmentalization of RNA. The retention timescales of RNA within individual droplets vary based on RNA length and structure, extending over several days. This prolonged molecular retention provides a potential mechanism for maintaining distinct RNA populations within separate coacervate compartments. Our findings suggest that nonfusing, membraneless coacervates could serve as primitive protocells capable of sustaining compartmentalized ribozyme activity in early Earth conditions. By stabilizing coacervate structures, environmental factors such as freshwater influx may have played a key role in shaping early molecular evolution, offering new insights into the origin of functional RNA systems. Beyond their implications for early life, these stabilized coacervates exhibit intrinsic polarizability due to their charged nature and diffuse counterion clouds, making them highly responsive to electric fields. We show that individual droplets and their larger assemblies can be precisely manipulated using low-voltage fields comparable in magnitude to a standard 9-volt battery. This controllability opens new possibilities for using coacervates as tunable materials for encapsulating, transporting, and delivering cargos in applications spanning biomedicine and manufacturing. Additionally, these systems serve as a model for understanding electrodynamic behaviors in biological materials, shedding light on how living systems may harness electrostatic interactions for organization and function.