Chemical Feedback and Collective pH-Dynamics in Enzyme-Powered Artificial Cells.

Chemical communication between artificial cells (ACs) is crucial for the collective behavior in synthetic prototissues. Recently synthesized ACs show pH-responsive and pH-modifying behavior by an enzymatic chemical reaction. However, the chemical interplay between pH-responsive ACs is theoretically not well studied. Here, we report a simple two-variable model for such ACs that couples substrate conversion, enzyme activity, membrane permeability, and pH-buffering. We calibrate the model to recent experiments of glucose oxidase- and urease-loaded ACs, and reproduce a protection mechanism against external acid or base perturbations. Building on the derived models we predict the dynamics of AC-mixtures of the two antagonistic ACs. Depending on composition and initial pH, the mixtures exhibit a stable low-pH state, a stable high-pH state, or bistability, providing a minimal route to hysteretic pH control in AC-communities. On longer time scales, fuel depletion leads to transient states with programmable pH and lifetime. Our results demonstrate the potential of chemical communication in AC-systems and provide testable design rules for future experiments.