Bioinspired mineralizing microenvironments generated by liquid-liquid phase coexistence.

Biominerals can exhibit improved mechanical properties and intricate morphologies not seen in nonbiologically-produced minerals of ostensibly the same composition. The remarkable properties of biogenic minerals are thought to arise due to precise local control over the mineral deposition process, including organic and inorganic inclusions. Understanding how Biology uses mineralizing microenvironments to control the process and outcome of materials synthesis is a grand challenge that promises to enable new routes to high-performance materials. This proposal addresses this challenge using bioinspired microenvironments formed by liquid-liquid phase coexistence to understand and control mineral formation. Liquid-liquid phase coexistence has only recently been appreciated as a mechanism for subcellular compartmentalization. Intracellular aqueous droplet phases are increasingly understood to be key features of intracellular organization, providing distinct biochemical microenvironments where reactions can be controlled by local concentration of reagents and biocatalysts. Liquid-liquid phase separation thus appears to be an important and previously unappreciated tool in Biology's toolbox for materials synthesis.Key scientific questions to be addressed include: How does the local environment during mineral formation control the resulting material composition, structure, and properties? What is the impact of real-time modulations in this environment during the reaction?We recently developed artificial mineralizing vesicles based on lipid vesicle-stabilized all-aqueous emulsions that contained enzymes capable of catalyzing the production of calcium carbonate. Here, we will use artificial mineralizing vesicles with subcompartmentalized interiors as test beds to learn about the consequences of liquid-liquid phase coexistence on mineral deposition. The mineralizing microenvironments to be studied here are expected to: (1) enable control over gradients of organic and inorganic inclusions within monolithic minerals/crystals by tuning their local availability during their synthesis; and (2) produce distinct mineral compositions in adjacent compartments at the microscale, with control over their physical association, from non-contacting through Janus structures to core-shell geometries. These microenvironments further provide exciting opportunities to explore the impact of competing reactions and complex active media on materials synthesis. Understanding how to control mineral composition in these gradient and contacting geometries will ultimately aid in the construction of complex functional materials with desired composition, optical properties, and mechanical response.