Molecular design of protein-based materials - state of the art, opportunities and challenges at the interface between materials engineering and synthetic biology

Structural proteins like silk, squid ring teeth, elastin, collagen, or resilin, among others, are inspiring the development of new sustainable biopolymeric materials for applications including healthcare, food, soft robotics, or textiles. Furthermore, advances in the fields of soft materials and synthetic biology have a joint great potential to guide the design of novel structural proteins, despite both fields progressing mostly in a separate fashion so far. Using recombinant DNA technologies and microbial fermentations, we can design new structural proteins with monomer-level sequence control and a dispersity of ca. 1.0, based on permutations of tandem repeats derived from natural structural proteins. However, the molecular design of recombinant and repetitive structural proteins is a nontrivial task that is generally approached using low-throughput trial-and-error experimentation. Here, we review recent progress in this area, in terms of structure-function relationships and DNA synthesis technologies. We also discuss experimental and computational advances towards the establishment of rapid prototyping pipelines for this family of biopolymers. Finally, we highlight future challenges to make protein-based materials a commercially viable alternative to current fossil-based polymers.