Droplet-supported liquid-liquid lateral phase separation as a step to floating protein heterostructures

Liquid-liquid phase separation plays an important role in many natural and technological processes. Herein, we implement lateral microphase separation at the surface of oil micro-droplets suspended in water to prepare a range of discrete floating protein/polymer continuous two-dimensional (2D) heterostructures with variable interfacial domain structures and dynamics. We show that gel-like domains of bovine serum albumin (BSA) co-exist with fluid-like polyvinyl alcohol (PVA) regions at the oil droplet surface to produce floating heterostructures comprising a 2D phase-separated protein mesh or an array of discrete mobile protein rafts depending on the conditions employed. Enzymes are embedded in the discontinuous BSA domains to produce droplet-supported microphase-separated 2D reaction scaffolds that can be tuned for interfacial catalysis. Taken together, our work has general implications for the structural and functional augmentation of oil droplet interfaces and contributes to the surface engineering and functionality of droplet-based micro-reactors.