Protein–Polyphenol Networks: From Fundamentals to Biomedical Applications

Abstract

Naturally occurring building blocks have attracted scientific interest for the assembly of functional materials due to their intrinsic biocompatibility and biodegradability. Proteins are a particularly crucial class of functional biomacromolecules involved in most fundamental processes of living organisms that can be assembled into nanomaterials for various biomedical applications. Another ubiquitous class of biomacromolecules are polyphenols, which have traditionally been referred to as “vegetable tannins”, have recently been employed in engineering advanced materials, owing to their available physicochemical and biological properties and capability of assembly through diverse interactions.

This thesis aims to introduce protein–polyphenol networks (PPNs), namely interconnected networks of proteins and polyphenols that can be deposited on a wide array of substrates. The polyphenol-mediated protein assembly of materials such as films, capsules, or nanoparticles (NPs) are introduced in this thesis because self-assembly approaches allow for the rapid generation of tailorable materials under mild conditions. This thesis also focuses on exploring the fundamentals of the interactions between proteins and polyphenols, which helps in understanding the assembly mechanism of PPNs.

The binding affinity between polypeptides and polyphenols is studied by analytical chemistry techniques, focusing on the interactions between side chains of proteins and polyphenols, which is crucial for the controllable design of protein-based materials. Then, a straightforward and versatile strategy through interfacial polyphenol-mediated protein assembly is introduced to create a library of functional PPN materials, including bioactive surface coatings and functional capsules. Moreover, the PPN capsules not only can be used to clarify the governing interaction(s) between different proteins and polyphenols, but also can be employed in various applications (e.g., enzymatic catalysis, fluorescence imaging, and cell targeting).

Next, a template-mediated supramolecular assembly method is developed to synthesize PPN NPs capable of endosomal escape and subsequent protein release in the cytosol. The versatility of this strategy in terms of NP size and protein type makes this a promising platform for potential applications in protein therapeutics. Finally, the protein–polyphenol interactions related to actual biological environments are investigated by the studying protein corona formed around different polyphenol-modified gold NPs (AuNPs). Protein corona compositional analysis demonstrates the binding preference of serum proteins with various polyphenols, and cellular uptake behaviors of polyphenol–AuNPs can elucidate the role of polyphenols in bio–nano interactions, which can act as reference works for the future implementation of polyphenols in biomedical applications.