Polyphenol-Binding Amyloid Fibrils Self-Assemble into Reversible Hydrogels with Antibacterial Activity

Abstract

Adaptable hydrogel networks with reversible connectivity have emerged as a promising platform for biomedical applications. Synthetic copolymers and low-molecular-weight gelators (LMWG) have been shown to form reversible hydrogels through self-assembly of the molecules driven by self-complementary hydrophobic interaction and hydrogen bonding. Here, inspired by the adhesive proteins secreted by mussels, we found that simply adding natural polyphenols, such as epigallocatechin gallate (EGCG) to amyloid fibrils present in the nematic phase, successfully drives the formation of hydrogels through self-assembly of the hybrid supramolecules. The hydrogels show birefringence under polarized light, indicating that the nematic orientation is preserved in the gel phase. Gel stiffness enhances with incubation time and with an increase in molecular ratios between polyphenol and fibrils, fibril concentration, and pH. The hydrogels are shear thinning and thermostable from 25 to 90 °C without any phase transition. The integrity of the trihydroxyl groups, the gallate ester moiety in EGCG, and the hydrophobicity of the polyphenols govern the interactions with the amyloid fibrils and thus the properties of the ensuing hydrogels. The EGCG-binding amyloid fibrils, produced from lysozyme and peptidoglycans, retain the main binding functions of the enzyme, inducing bacterial agglomeration and immobilization on both Gram-positive and Gram-negative bacteria. Furthermore, the antibacterial mechanism of the lysozyme amyloid fibril hydrogels is initiated by membrane disintegration. In combination with the lack of cytotoxicity to human colonic epithelial cells demonstrated for these hybrid supramolecules, a potential role in combating multidrug-resistant bacteria in biomedical applications is suggested, such as in targeting diseases related to infection of the small intestine.

Phenolic Building Blocks for the Assembly of Functional Materials

“…[177] The TNA hydrogel exhibits adhesiveness, extensibility, and superior in vivo hemostatic ability. Very recently, Hu et al [178] demonstrated the formation of a hydrogel by adding polyphenols such as EGCG to amyloid fibrils present in the nematic phase. The resulting gels have been observed to be shear thinning and thermostable in the range of 25-90 °C without occurrence of a phase transition.…”

Tannin-controlled micelles and fibrils of κ-casein

“…Particularly strong tendency to integrate EGCG into micelles was reported in the case of milk casein 30 . A reversible fibrillar self-assembly of proteins with ability to up-take EGCG was also recently reported 31 . In the present work we focus on fibrillar aggregation of micellar κ-casein, a well-known protein from milk 32 , and investigate how the tannin epigallocatechin-gallate (EGCG, 458 g/mol) can be used to understand the aggregation mechanism and control the system.…”

Adhesive behavior and detachment mechanisms of bacterial amyloid nanofibers

“…For instance, mutations and grafts on the peptide sequence of functional amyloids such as curli can change the interfacial strength, as well as mechanical properties such as bending rigidity, which may explain variations in the performance of amyloid based adhesives. [59][60][61][62] Furthermore, polymeric or DNAbased self-assembled nanofibers could also be studied in a similar manner to examine whether biological amyloids offer any advantages over such systems in terms of adhesive performance. 63,64 The current work focusing on the development of computational phase diagrams for adhesion sets the stage for pursuing these diverse research directions to evaluate a variety of interfacial phenomena relevant to biological, as well as engineered adhesives.…”