Fluid protein condensates for bio-inspired applications

Since the discovery of tropoelastin liquid–liquid phase separation in the 1950s, it has been recognized that fluid protein condensates, including coacervates and liquid crystals, are involved in the biofabrication of functional materials in numerous organisms. Prominent examples include elastin, spider silk, the mussel byssus and various biomineralized tissues as well as less studied systems such as velvet worm slime, sandcastle worm cement and the squid beak; similar mechanisms might lead to amyloid formation in neurodegenerative diseases. Engineers have exploited these fundamental insights to produce synthetic condensates for various biomedical applications. In this Review, we highlight biological systems in which protein condensates are involved in the production of biopolymeric and biocomposite materials (and possible implications of disruption of these structures in pathologies), and we discuss examples where extracted biological concepts have inspired translational applications. We emphasize the common strategies observed between different biological systems for the use of condensates in the assembly of various fibres, adhesives and composites. Finally, we discuss the applications of bio-inspired condensates in drug delivery, biomedical adhesives, tissue engineering and bioengineered composites.