All-Amyloid Functional Coacervates.

Electrostatic complex coacervates offer a robust pathway to convert homogeneous oppositely charged polyelectrolyte solutions into condensed structured liquids via liquid-liquid phase separation (LLPS). Directing these principles toward artificial, all-proteinaceous complex coacervates enables the development of soft matter systems fully compatible with a broad range of advanced biotechnological products. Here, we employ charge-tunable β-lactoglobulin and lysozyme amyloid nanofibrils as building blocks toward fully proteinaceous functional materials. The functionality is dictated by engineering the composition and self-organization of oppositely charged amyloid nanofibrils at the liquid-liquid interface. Depending on the path and process followed, we demonstrate all-amyloid interfacial complex coacervates in the form of vein-like tubular structures or capsules with tunable electrical or ionic conductivity, viscoelasticity, multidimensional morphology, and programmable macromolecular crowding. These constructs, made solely of amyloid constituents, provide a general platform for artificial protein scaffolds and advanced materials with potential applications in bioelectronics and bio-optics.