Metabolic activity to animate coacervate materials

Non-technical abstract:Biology has evolved a wide range of impressive materials, such as the strong and tough silks of spiders and the wet adhesive proteins of mussels. Scientists have long looked to these and other biological materials for inspiration to create new materials for society. However, these synthetic materials often lack many desirable features of biological materials such as the ability to grow, replicate, or self-regulate. This project seeks to impart some of these active functions found in biology to synthetic materials. This work aims to understand how the consumption of chemical fuel by biosynthetic materials impacts the material properties and function as well as how the material properties impact the consumption of chemical fuel. This will be done in model materials that contain enzymes, or nature’s catalysts, and polymers, or plastics. The impact of both external and internal chemical fuel driven changes on materials will be studied experimentally and using simple models. The goals of this work are both to create new functional, responsive materials and to understand how natural systems couple materials properties and active processes. These research objectives will be coupled with educational activities that provide interdisciplinary training for students from middle through graduate school. This will be achieved through complementary activities including a graduate student presentation series, outreach activities with middle school students, and summer research experience for high school students. Technical abstract:The project aims to create “metabolic” droplets in which chemical activity serves to alter and ultimately control material properties. This work is inspired by the capabilities of biomolecular condensates where phase separation of biopolymers creates the membraneless organelle and is often linked to biochemical reactions that occur in the organelle creating feedback loops that serve to modulate reaction rates. By coupling enzymatic activity to phase separation in vitro, we seek to animate equilibrium materials to create active, dynamic materials that capture life-like properties. This will be done in model complex coacervate droplets composed of the enzyme glucose oxidase and a cationic polymer. The composition and rheology of coacervate drops will first be characterized at equilibrium as a function of pH and initial composition. The system will then be pushed out of equilibrium triggering a variety of responses that include changes in drop rheology, formation of internal compartments (vacuoles), osmotic swelling and rupture, and size-dependent dissolution. This activity will be induced with pH changes that are initiated on the exterior or interior of the drops via addition of acid or glucose, respectively. With this work, we aim to understand how the rate of reaction-induced changes to pH compares to the rate of various relaxation mechanisms in coacervate drops to create new material structures and features that recapitulate features of living materials. In addition to these research goals, the project aims to provide educational and training opportunities for a diverse range of students. This will be achieved by (1) expanding a multidisciplinary student seminar series for graduate students and postdoctoral scholars, (2) implementing hands-on experiences on matter out-of-equilibrium for middle school students, and (3) offering summer research experiences for high school students.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.