Dynamic and Hierarchically Structured Networks with Tissue-like Mechanical Behavior.

Collagen is the most abundant structural protein in soft tissues, and the duplication of its structure and mechanics represents a key challenge to nanotechnology. Here we report a fibrous supramolecular network that can mimic nearly all of the aspects of collagen from dynamic hierarchical architecture to nonlinear mechanical behavior. This complex self-assembly system is solely based on a glucose polymer: curdlan, which is synthesized by bacteria and can form a similar triple helix as collagen. Triggered by solvent and temperature cues, free curdlan chains wind into superhelical trimers, and the trimers then bundle hexagonally into nanofibers of 20-40 nm in diameter. The fibers are interconnected in a water-rich 3D network structure. The network is highly dynamic and stress-responsive, which can shift from isotropic to anisotropic organization by the winding/unwinding of stress-induced interfiber triple helical net-points. Mechanical tests show that these nanofiber networks exhibit similar nonlinear elasticity as collagenous tissues including skin and tendon. The supramolecular networks also display a very wide range of tensile strength from ∼60 KPa to ∼50 MPa depending on the specific network organization. These biomimetic and dynamic supernetworks may have applications in tissue engineering, drug delivery systems, artificial skin, and soft robotics.