EAGER: (ST1) Dissipative Self-Assembly of Metabolic Soft Matter

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Non-technical Abstract"Humans can survive in hostile environments by building compartments (e.g., houses) and creating favorable conditions within their interiors (e.g., by heating or cooling). Similarly, living cells use material compartments and biochemical reactions to enable their proper function in diverse environments. These functions -such as the ability to move, adapt, heal, and communicate- derive from the close integration of material structures and chemical processes. The ability to synthesize "metabolic materials" with similar functionality remains extremely limited. It is known how to make material structures and how to control systems of chemical reactions. However, it is not known how to couple the two together to animate matter with flows of energy and information as living organisms do. To address this challenge, this project will create relatively simple material systems in which molecular compartments are coupled to chemical reactions by engineered feedback loops. It will demonstrate how such chemically-fueled metabolic materials can enable new functions such as the ability to assemble in hostile environments, to control size and morphology, to regulate fuel consumption, and to degrade on demand. The basic principles identified will guide the future realization of other chemically-fueled material systems inspired by living matter.Technical AbstractThis project proposes to create "metabolic soft matter" based on self-assembled polymeric compartments with primitive metabolic activity that modify their local environment to stabilize (or destabilize) the assembled structures. Metabolic activity is introduced by the co-assembly of supercharged enzymes into coacervate droplets formed by liquid-liquid phase separation of oppositely charged polyelectrolytes in water. In the presence of chemical "fuel", these enzymes catalyze reactions that alter the local conditions (e.g., pH) and thereby droplet stability. Importantly, the processes of self-assembly and metabolism are mutually dependent and allow for engineering both positive and negative feedback loops. Self-assembly enhances metabolic activity by concentrating enzymes within small volumes, thereby increasing the local concentration of metabolic product(s). Reaction-induced concentration changes serve to enhance or inhibit self-assembly depending on the choice of materials and reactions. Building on designed metabolic materials based on supercharged catalase that respond to pH changes driven by the decomposition of H2O2 fuel - this proposed work aims (1) to engineer the pH-dependent phase behavior of coacervate drops enriched with supercharged enzymes; (2) to quantify metabolic activity and its influence in modifying the drop environment; and (3) to couple metabolism and self-assembly using positive and negative feedback to enable dynamic functions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.