Genetically Engineered Protein-Based Bioadhesives with Programmable Material Properties.

Silk-amyloid-mussel foot protein (SAM) hydrogels made from recombinant fusion proteins containing β-amyloid peptide, spider silk domain, and mussel foot protein (Mfp) are attractive bioadhesives as they display a unique combination of tunability, biocompatibility, bioabsorbability, strong cohesion, and underwater adhesion to a wide range of biological surfaces. To design tunable SAM hydrogels for tailored surgical repair applications, an understanding of the relationships between protein sequence and hydrogel properties is imperative. Here, we fabricated SAM hydrogels using fusion proteins of varying lengths of silk-amyloid repeats and Mfps to characterize their structure and properties.

Protein-Based Hydrogels and Their Biomedical Applications.

Hydrogels made from proteins are attractive materials for diverse medical applications, as they are biocompatible, biodegradable, and amenable to chemical and biological modifications. Recent advances in protein engineering, synthetic biology, and material science have enabled the fine-tuning of protein sequences, hydrogel structures, and hydrogel mechanical properties, allowing for a broad range of biomedical applications using protein hydrogels. This article reviews recent progresses on protein hydrogels with special focus on those made of microbially produced proteins.

Microbial Synthesis of High-Molecular-Weight, Highly Repetitive Protein Polymers.

High molecular weight (MW), highly repetitive protein polymers are attractive candidates to replace petroleum-derived materials as these protein-based materials (PBMs) are renewable, biodegradable, and have outstanding mechanical properties. However, their high MW and highly repetitive sequence features make them difficult to synthesize in fast-growing microbial cells in sufficient amounts for real applications. To overcome this challenge, various methods were developed to synthesize repetitive PBMs.

A Biosynthetic Hybrid Spidroin-Amyloid-Mussel Foot Protein for Underwater Adhesion on Diverse Surfaces.

Strong underwater adhesives are attractive materials for biomedical healing and underwater repair, but their success in applications has been limited, owing to challenges with underwater setting and with balancing surface adhesion and cohesion. Here, we applied synthetic biology approaches to overcome these challenges through design and synthesis of a novel hybrid protein consisting of the zipper-forming domains of an amyloid protein, flexible spider silk sequences, and a dihydroxyphenylalanine (DOPA)-containing mussel foot protein (Mfp). This partially structured, hybrid protein can self-assemble into a semi-crystalline hydrogel that exhibits high strength and toughness as well as strong underwater adhesion to a variety of surfaces, including difficult-to-adhere plastics, tendon, and skin.