Developing bio-inspired materials via controlled protein assembly

Abstract

Self-assembly of proteins, endowed with great diversity, orthogonality, and modularity by natural selection, plays irreplaceable role orchestrating numerous biological cues in all organisms, and provides an infinite reservoir of inspirations for developing novel biomaterials and molecular tools. In this thesis, we highlight the calcium-dependent assembly of calmodulin (CaM)/M13, the enzymatic assembly of mussel foot protein (Mfp) driven by tyrosinase, the photo-responsive assembly of Phytochrome B (PhyB)/Phytochrome interacting factor (PIF), and stoichiometric assembly of PSG/SynGAP mediating formation of membraneless organelles, and demonstrate the design and synthesis of versatile biomaterials based via directed protein self-assembly.

In chapter 2, we report the creation of entirely protein-based Ca²⁺-responsive hydrogels by covalently assembling CaM and its cognate ligand, M13-peptide, using SpyTag/SpyCatcher chemistry. The resulting protein hydrogels comprising CaM and M13 exhibited mechanics and stability dependent on Ca²⁺ as well as suitability for 3D cell culturing. In chapter 3, we demonstrate the creation of entirely recombinant protein-based adhesive hydrogels by assembling mussel foot protein-3 (Mfp-3) via in vitro enzymatic oxidation mediated by recombinant tyrosinase. The resulting materials exhibited not only capacity of long-term cell encapsulation and post-gelation modification by SpyTagged proteins, but also robust water-resistant adhesion toward biological tissues which can be further improved with supplement of silica nanoparticles (Si-NPs). In chapter 4, we designed a red-light-induced dimerizer (rLID) based on PhyB and PIF from <span style="font-style:italic">Arabidopsis thaliana</span> that capable of promoting the PSG/SynGAP protein phase separation in HEK293T cells with far-red light illumination.

Taken together, this thesis demonstrates the feasibility of using inducible protein-protein interactions to design biomaterials with dynamic properties, including stimuli-responsiveness, water-resistant bioadhesion, and capability of cell encapsulation. In addition, this thesis points to a novel approach for designing optogenetic tools delivering opto-control with far-red light to cellular events governed by protein phase separation.

Date of Award	2020
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology