Synthesis of an entirely protein-based adhesive hydrogel enabled by enzymatic oxidation

Abstract

Mussel foot has been long studied for their adhesive properties in diverse conditions, but it was until recently that these mussel foot proteins (Mfp) can be produced in the recombinant form using bacterial expression systems. However, there are drawbacks from using a bacterial system to express such proteins; some of which include: insolubility, difficulty in purification, and the relatively large size of the full-length protein. These difficulties can be avoided if only the functional portions of Mfp—the minimized adhesive domains—can be utilized. However, the adhesive domains are short in length, and they, when stand alone, may not be able to provide sufficient wet adhesiveness as the full-length proteins do. By inserting truncated adhesive domains derived from a mussel foot protein into the amine and carboxyl termini and the middle of an elastin-like polypeptide, we created TMfp: a recombinant protein that can form adhesive materials upon oxidation by tyrosinase—an enzyme that post-translationally oxidizes tyrosine into the adhesive moieties, DOPA. The resulting protein can not only serve as an adhesive interface but can also form an entirely protein-based hydrogel. The adhesive interface was shown to have adhesive properties to polymethyl methacrylate (PMMA) and glass surfaces. Furthermore, the stiffness of TMfp hydrogels can be modulated by using the coordination of DOPA-metal (e.g., Fe³⁺ and Ti³⁺). The material was well suited for 3D cell culturing and exhibited excellent cytocompatibility toward encapsulated human epithelial cells. This material has the potential to be a biocompatible adhesive material for biomedical and research purposes.

Date of Award	2018
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology