One-pot solvent exchange preparation of non-swellable, thermoplastic, stretchable and adhesive supramolecular hydrogels based on dual synergistic physical crosslinking

Abstract

With their unique properties of self-healing and viscoelasticity, physically crosslinked supramolecular hydrogels are promising materials for soft robotics, wearable electronics and biomedical applications. However, the weak mechanical properties of supramolecular hydrogels, especially those prepared with natural polymers, limit their wide-spread application, and swelling is one of the key factors that contributes to the weakening of hydrogels. Herein, we utilize a simple one-pot solvent exchange method to prepare non-swellable, thermoplastic and tough supramolecular gelatin hydrogels based on two synergistic physical crosslinkings, namely, the self-assembled tri-helix structure of gelatin and the hydrophobic aggregation of gelatin-grafted and free hydrophobic motifs. The obtained hydrogels possess a stable water content above 70% with extended incubation in water. These hydrogels are highly malleable upon heating but are extremely stretchable and tough after cooling to room temperature. Furthermore, the supramolecular gelatin hydrogels exhibit robust adhesion to various material surfaces and minimal cytotoxicity. NPG Asia Materials (2018) 10, e455; doi:10.1038/am.2017.208; published online 5 January 2018 INTRODUCTION Hydrogels, due to their high water content and tunable physical and biological properties, are extensively used in soft robotics, wearable electronics and biomedical applications. 1-6 Supramolecular hydrogels, which are solely stabilized by physical crosslinkings, such as host-guest interactions, electrostatic attraction and hydrophobic aggregation, have recently received increasing attention due to their unique properties, including self-healing, energy dissipation and viscoelasticity. 7-13 However, the poor mechanical performance of supramolecular hydrogels, especially hydrogels prepared with natural polymers, which possess superior biocompatibility and bioactivity, remain a major hurdle to the wide-spread application of these hydrogels. To improve the mechanical properties of chemically crosslinked hydrogels, researchers have developed ingenious strategies, including nanocomposite hydrogels, double-network hydrogels, hybrid crosslinking hydrogels and tetra-polyethylene glycol hydrogels. [14][15][16][17][18][19][20][21][22] Recently, increasing research attention has been dedicated to enhancing the mechanical performance of physically crosslinked supramolecular hydrogels. One recent study demonstrated very tough physical hydrogels composed of polyampholytes. 23 Another study showed that pre-assembled host

Osteochondral Regeneration with 3D‐Printed Biodegradable High‐Strength Supramolecular Polymer Reinforced‐Gelatin Hydrogel Scaffolds

“…Hydrogels are emerging as a promising class of biomaterials for both soft and hard tissue regeneration. [18][19][20] Recently, mechanically resilient gelatin hydrogels crosslinked by supramolecular host-guest interactions [21] or dual synergistic physical crosslinking [22] were reported by Bian. [14][15][16][17] Among a wide array of hydrogels for tissue engineering, gelatin hydrogel has been developed as a variety of bioinks for 3D printing due to its better biocompatibility, biodegradability, bioactivity, and abundance from diverse sources.…”

Self‐Healing Materials for Energy‐Storage Devices

“…Covalent dynamic chemistries usually include disulfide bonds, [ 80–83 ] acylhydrazone bonds, [ 84–86 ] imine bonds, [ 87–89 ] Diels–Alder reaction, [ 90–92 ] and borate ester bonds. [ 93–95 ] While noncovalent dynamic interactions include hydrogen bonds, [ 24,96–104 ] metal–ligand coordination, [ 26,105–107 ] electrostatic interactions, [ 108 ] host–guest interactions, [ 109–112 ] hydrophobic interactions, [ 113,114 ] π–π stacking interactions, [ 115,116 ] and crystallization. [ 117 ] Due to these reversible dynamic bonds, intrinsic self‐healing materials can repair themselves repeatedly at the same fracture position without external healing agents, which avoids the tedious encapsulation process involved in extrinsic self‐healing materials.…”

High-Strength Albumin Hydrogels With Hybrid Cross-Linking

“…However, the poor mechanical properties of natural protein hydrogels is one of the main drawbacks impeding their application in some cases (Silva et al, 2017;Tang et al, 2018). Recently, great efforts have been made to enhance the mechanical properties of natural protein hydrogels, and some strategies have been developed, including nanocomposite (Yuk et al, 2016;Qin et al, 2017;Wang et al, 2017Wang et al, , 2018, physical cross-linking (Toivonen et al, 2015;Feng et al, 2018;Yan et al, 2019;Zhang et al, 2019), solvent induction (Li et al, 2016;Zhang et al, 2016;Hashemnejad et al, 2017;Zhu et al, 2018), double network (Bhattacharjee et al, 2015;Luo et al, 2016;Rangel-Argote et al, 2018;Tavsanli and Okay, 2019), hybrid cross-linking (Moura et al, 2011;Epstein-Barash et al, 2012;Xu et al, 2016;Nojima and Iyoda, 2018;Yang et al, 2018), and so on.…”