Elucidating the Reciprocal Interplay between Supramolecular Polymer Cytoskeletons and Fuel-Dependent Synthetic Cells

Synthetic cells are compartments designed to mimic the functions and characteristics of living cells. By constructing synthetic cells from abiotic, basic components (bottom-up), it is possible to investigate the minimal requirements for life and gain insights into fundamental principles of biology. Among the available platforms, complex coacervates are particularly attractive, due to their potential to encapsulate a wide range of biomolecules and other cargo, enabling genotype-phenotype mapping. By coupling coacervate formation to a fueled chemical reaction cycle, the synthetic cells become fuel-dependent, growing in the presence of fuel and decaying in its absence, resembling biological cells. However, constructing cellular substructures for these fuel-dependent synthetic cells, such as cytoskeletons, has remained an unresolved challenge. Here, we show that supramolecular (co)polymers can act as cytoskeletons for the synthetic cells, depending on their condenophilicity (their affinity for the droplet phase). By using two distinct supramolecular building blocks, the condenophilicity can be modulated. Supramolecular copolymers where only some of the monomers bind to the complex coacervate result in the formation of a protruding cytoskeleton in and around the droplet. However, as condenophilicity increases, the polymers partition strongly into the coacervates, leading to the formation of a fully encapsulated cytoskeleton. We found that these internal structures influence the synthetic cell properties, such as morphology and lifespan. Moreover, the synthetic cells can dynamically reconstitute the supramolecular fibers, creating distinct populations within the cells and the surrounding dilute phase. Our results demonstrate that orthogonally assembled structures can serve as cellular substructures for active complex coacervate-based synthetic cells, broadening the existing arsenal of tools to bestow these rudimentary synthetic cells with more life-like properties.