Fig. 2 |. Examples of methods used to fabricate and design protein-based biomaterials.

a, Overview of the process for spinning protein fibres: (left) wet spinning, in which fibres form in a liquid coagulation bath; (middle) dry spinning, in which extruded proteins in solvent dry out into fibres and (right) electrospinning, in which a voltage is applied to an extruded protein solution that forms fibres on a collection plate. b, The layer-by-layer method for creating nanotubes is a stepwise method that alternates between proteins and oppositely charged amino acid solutions to form multilayer tubes within a porous support membrane that is subsequently dissolved. c, S-layer arrays from recombinantly produced proteins or isolated from native S-layers can be assembled in various manners, for example, in solution, on solid supports, surrounding liposomes or at air–water interfaces. d, Representation of two key aspects of protein and biomaterial self-assembly. Hydrophobic residues can be interdigitated for optimal packing, and polar residues can form complex hydrogen bonding networks and other electrostatic interactions that promote assembly of components. e, An overview of a widely used computational nanoparticle design pipeline that uses docking algorithms to bring together components in space and sample their rotational and translational degrees of freedom. The resulting interfaces between components are then designed using computational tools such as Rosetta and ProteinMPNN. f, Two examples of how proteins that associate with one another can be used to create larger macroscale biomaterials such as hydrogels using both structured and unstructured linkers. For the unstructured linkers, a two-component system design consists of ABABA and CBC, in which A and C are proteins that associate with one another and B is a flexible linker. When the two systems are mixed, proteins A and C form a crosslink resulting in a macroscopic hydrogel. For the structured linkers, two different protein oligomers are each genetically fused to different associative groups that can then covalently or non-covalently crosslink to form larger macroscopic hydrogels. HSA, human serum albumin. Part e adapted with permission from ref. 218, PNAS. Part f adapted with permission from ref. 189, PNAS.