Bioactive hierarchical silk fibers created by bioinspired self-assembly

Linpeng Fan,Jing-Liang Li,Xungai Wang,Zengxiao Cai

doi:10.1038/s41467-021-22673-4

Abstract

Artificial recapitulation of the hierarchy of natural protein fibers is crucial to providing strategies for developing advanced fibrous materials. However, it is challenging due to the complexity of the natural environment. Inspired by the liquid crystalline spinning of spiders, we report the development of natural silk-like hierarchical fibers, with bundles of nanofibrils aligned in their long-axis direction, by self-assembly of crystallized silk fibroin (SF) droplets. The formation of self-assembled SF fibers is a process of coalesced droplets sprouting to form a branched fibrous network, which is similar to the development of capillaries in our body. The as-assembled hierarchical SF fibers are highly bioactive and can significantly enhance the spreading and growth of human umbilical vein endothelial cells compared to the natural SF fibers. This work could help to understand the natural silk spinning process of spiders and provides a strategy for design and development of advanced fibrous biomaterials for various applications.

Highlights

Artificial recapitulation of the hierarchy of natural protein fibers is crucial to providing strategies for developing advanced fibrous materials
One single silk fiber is a bundle of thinner fibrils aligned along its long axis and the width of the fibrils ranges from nanometers to sub-micrometers (Fig. 1a)[6,7,8]
Different from the micelle model, the liquid crystalline model proposes that the silk protein matrix in the silk gland contains numerous small spherical droplets with liquid crystalline property, which grow by coalescence and are subsequently spun into silk fibers (Fig. 1a)[11]

Summary

Introduction

Artificial recapitulation of the hierarchy of natural protein fibers is crucial to providing strategies for developing advanced fibrous materials. Inspired by the liquid crystalline spinning of spiders, we report the development of natural silk-like hierarchical fibers, with bundles of nanofibrils aligned in their long-axis direction, by self-assembly of crystallized silk fibroin (SF) droplets. In vitro recapitulation of the hierarchical suprafibrillar structure of natural silk fibers is crucial to understanding the in vivo assembly process and providing insight into the design and development of advanced artificial biomaterials. We aim to understand the self-assembly process of crystallized droplets of silk protein molecules to form hierarchical suprafibrillar silk fibers and provide strategies for development of advanced fibrous biomaterials in vitro (Fig. 1). This is very important for obtaining resultant materials with tailored morphologies and structures With this self-assembly system, hierarchical silk fibers with width and thickness down to nanometer scale can be produced at a very low concentration of SF solution (0.2% (wt/v) in this work), which is very challenging to achieve using the existing technologies

Objectives

Methods

Results