Bioinspired supramolecular fibers drawn from a multiphase self-assembled hydrogel

Abstract

Inspired by biological systems, we report a supramolecular polymer-colloidal hydrogel (SPCH) composed of 98 wt % water that can be readily drawn into uniform (∼6-µm thick) "supramolecular fibers" at room temperature. Functionalized polymer-grafted silica nanoparticles, a semicrystalline hydroxyethyl cellulose derivative, and cucurbit[8]uril undergo aqueous self-assembly at multiple length scales to form the SPCH facilitated by host-guest interactions at the molecular level and nanofibril formation at colloidal-length scale. The fibers exhibit a unique combination of stiffness and high damping capacity (60-70%), the latter exceeding that of even biological silks and cellulose-based viscose rayon. The remarkable damping performance of the hierarchically structured fibers is proposed to arise from the complex combination and interactions of "hard" and "soft" phases within the SPCH and its constituents. SPCH represents a class of hybrid supramolecular composites, opening a window into fiber technology through low-energy manufacturing. supramolecular fiber | hydrogel | self-assembly | damping | spider silk I n nature, spiders spin silk fibers with superb properties at ambient temperatures and pressures (1, 2). We have yet to mimic such an elegant process. Conventionally, synthetic fibers are manufactured through a variety of spinning techniques, including wet, dry, gel, and electrospinning (3). Such approaches to generate fibers are limited by high energy input, laborious procedures, and intensive use of organic solvents. Supramolecular pathways enable the formation of filamentous soft materials that are showing promise in biomedical applications (4-6), such as cell culture (7-9) and tissue engineering (10). However, such materials are constrained by the length scale (submicrometer level) (11-13), energy intake during production (9), and complex design of assembly units (14).Here, we report drawing supramolecular fibers of arbitrary length from a dynamic supramolecular polymer-colloidal hydrogel (SPCH) at room temperature (Movie S1). The components consist of methyl viologen (MV)-functionalized polymer-grafted silica nanoparticles (P1), a semicrystalline polymer in the form of a hydroxyethyl cellulose derivative (H1), and cucurbit[8]uril (CB[8]) as illustrated in Fig. 1. The macrocycle CB[8] is capable of simultaneously encapsulating two guests within its cavity, forming a stable yet dynamic ternary complex, and has been exploited as a supramolecular "handcuff" to physical cross-link functional polymers (15-18). Introducing shape-persistent nanoparticles into the supramolecular hydrogel system allows for modification of the local gel structures at the colloidal-length scale, resulting in assemblies with unique emergent properties (19). The hierarchical nature of the SPCH is presented, where the hydrogel is composed of nanoscale fibrillar structures. The self-assembled SPCH composite exhibits great elasticity at a remarkably high water content (98%), showing a low-energy manufacturing process for fibers from natural, ...

Dynamic Hydrogels from Host–Guest Supramolecular Interactions

“…In another interesting approach to the generation of hydrogels, CB[8] can be threaded as a rotaxane on the first guest and used to cross‐link polymer network, which can then bind to a second guest pendant from a different polymer to enable additional cross‐linking for reversible interfacial adhesion (Figure B) . Hybrid hydrogels with altered mechanical properties can also be created from CB[8]‐based ternary complexes, such as by affixing the first guest to silica nanoparticles and the second guest to a polymer chain . Precursors that were first pre‐organized by ternary complex formation and subsequently polymerized into a hydrogel have also been explored for applications such as wound dressings, with the gel being easily removed by addition of a competing adamantane‐based guest for CB[8] …”

Preparation and Characterization of Artificial Spider Silk Produced through Microchannel Techniques

“…Mimicking this known knowledge, one can produce industrial quantities of SSs. Interestingly; these authors [8][9][10][11][12] obtained a water-soluble protein, which exactly mimic nature. This is important because one can now keep the spider protein soluble at very high amounts, which enables spider dragline silk RSDS formation.…”

“…Several researchers [2,[8][9][10][11][12] have found remarkable pH variation in these glands. They [2,[8][9][10][11][12] marked that these controlled variations stimulate certain portions of the SSs-protein, which initiates the production of RSDS in certain well localized (and recognized) point. Mimicking this known knowledge, one can produce industrial quantities of SSs.…”

“…As a direct consequence, producing industrial rate should implicate the direct usage of human-made silk compounds with human spinning technologies. Researchers starts to mimic spiders and turn to biomimetic-spinning technologies [2,[8][9][10][11][12]. Up to date, they did not reach to their aim.…”

Tailored Spider Silk: The Future Solution to Biomaterials

“…One of these biomaterials is spider silk (SS) that contains large proteins. SS-fibers are as tough as steel and some SS-fibers have elasticity near caoutchouc [1,2]. When one combines their fantastic characteristics, SS show double or even triple toughness of manufactured-fibers such as Kevlar or Nylon.…”