Biomaterials are tightly associated with the development of human civilization. A biomaterial is any material, natural or man‐made, that comprises whole or part of a living structure or biomedical device which performs, augments, or replaces a natural function. Although some natural matters were used as biomaterials at the early stage of civilization, synthetic biomaterials became the mainstream nowadays (Chapter 1). With the potential to recapitulate the intricate biological systems, and perhaps even to decipher the meaning of life, developing biomaterials from scratch is gaining traction among synthetic biologists. Among the multi-scale natural living systems, the one consisting of phase-separated protein condensates at the molecular level (Chapter 2) and those of multicellular assem...[ Read more ]

Biomaterials are tightly associated with the development of human civilization. A biomaterial is any material, natural or man‐made, that comprises whole or part of a living structure or biomedical device which performs, augments, or replaces a natural function. Although some natural matters were used as biomaterials at the early stage of civilization, synthetic biomaterials became the mainstream nowadays (Chapter 1). With the potential to recapitulate the intricate biological systems, and perhaps even to decipher the meaning of life, developing biomaterials from scratch is gaining traction among synthetic biologists. Among the multi-scale natural living systems, the one consisting of phase-separated protein condensates at the molecular level (Chapter 2) and those of multicellular assemblies at the cellular level (Chapter 3) drew our interest mostly, thanks to their genetic programmability.

In Chapter 2, we created subcellular active matter that underwent small-molecule/light-induced phase transition (SLIPT) by combining the neuron-derived synaptic adhesion/organizing molecule (SAM) , the soluble elastin-like polypeptide (ELP), and the B₁₂-dependent protein photoreceptor CarHc. The recombinant protein comprising these three domains transitioned into condensed phase inside living cells upon addition of AdoB12 and returned to dilute phase on light irradiation, rendering a robust platform for studying the roles of protein phase transition in synapse regulation.

In Chapter 3, we illustrated a strategy that enabled the assembly of engineered Saccharomyces cerevisiae into self-propagating ELMs via ultra-high-affinity protein/protein interactions. These yeast cells were genetically engineered to display on their surfaces the protein pairs SpyTag/SpyCatcher or CL7/Im7, which enabled their assembly into multicellular structures capable of further growth and proliferation. The assembly process could be controlled precisely via optical tweezers or microfluidics. Furthermore, introducing of functional motifs such as super uranyl binding protein or mussel foot proteins via genetic programming applied these materials in uranium extraction from seawater and bioadhesion, pointing to their potential in chemical separation and biomedical applications

Together, the thesis demonstrated the feasibility of using specific protein/protein interactions to synthesize self-assembled biomaterials, ranging from subcellular to multicellular levels, which has opened up a new dimension for materials synthetic biology.