Sea Cucumber-Inspired Autolytic Hydrogels Exhibiting Tunable High Mechanical Performances, Repairability, and Reusability

Abstract

Inspired by stimuli-responsive remarkable changes in consistency (hardening, softening, autolysis) of sea cucumbers, we synthesized a supramolecular polymer(SP) hydrogel directly by photoinitiated aqueous polymerization of N-acryloyl 2-glycine monomer bearing one amide and one carboxyl group on the side chain. The SP hydrogels doped with Ca(2+) demonstrated excellent mechanical properties-high tensile strength (∼1.3 MPa), large stretchability (up to 2300%), high compressive strength (∼10.8 MPa), and good toughness (∼1000 J m(-2)) due to cooperative hydrogen bonding interactions from amide and carboxyl together with Ca(2+) cross-linking. Responding to the change in pH and Ca(2+) concentration, the hydrogels could modulate their network stability and mechanical properties: at pH3.0 and higher Ca(2+) content, the hydrogel formed low swelling network which was stiff and stable; in alkaline or neutral buffer with lower content of or without Ca(2+), the hydrogel formed a highly swollen transient network, which was soft and eventually autolyzed. The reversible multiple noncovalent bonds enabled the hydrogels to achieve thermoplasticity, self-healability, and reusability. Notably, distinct formulations of hydrogels could be welded together under heating to form a gradient hydrogel. In vitro cytotoxicity assay and subcutaneous implantation indicated that the SP hydrogels were biocompatible and autolytic in vivo. The SP hydrogels may find applications as temporary biodevices for intestinal drug delivery or for injectable filling in assisting suturing small vessels.

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

“…[26] In this study, copolymerization of GelMA can maintain the swelling stability of the PACG-GelMA hydrogel in aqueous solution because of chemical crosslinking networks formed. [26] In this study, copolymerization of GelMA can maintain the swelling stability of the PACG-GelMA hydrogel in aqueous solution because of chemical crosslinking networks formed.…”

“…[27,28] Figure 1 summarizes the mechanical properties of the fully swollen PACG-GelMA hydrogels. [26,31] However, excessively high crosslinking density of GelMA may interfere with the formation of PACG hydrogen bonds, resulting in a decline of mechanical strength. And when the GelMA content is fixed, the mechanical strengths are considerably increased with the increment in monomer content of ACG.…”

“…[26] Nevertheless, at a physiological neutral pH, the PACG hydrogel was quickly autolyzed and disintegrated within several hours, making it unsuitable for tissue repair scaffold application. Previously, inspired by remarkable stimuliresponsive changes in consistency of sea cucumbers, we prepared supramolecular poly (N-acryloyl 2-glycine) (PACG) hydrogel with side chain containing amide and carboxyl dual hydrogen bonds, which not only contributed to strengthening the hydrogels formed, but also served as dynamic bonds to modulate the mechanical properties of the hydrogels.…”

A High Strength Self-Healable Antibacterial and Anti-Inflammatory Supramolecular Polymer Hydrogel

“…Recently, great achievements have been made in the development of high strength hydrogels, placing great hope on substitution and regeneration of soft supporting tissues . As implantable devices or bioscaffolds, the biomaterials themselves are required not to evoke the foreign body response, which is associated with the response of immune system to xenobiotics .…”

Biphasic Synergistic Gel Materials with Switchable Mechanics and Self‐Healing Capacity

“…[1,2] Currently, hydrogels with ahydrophilic polymer network mainly utilize reversible noncovalent polymer netpoints (that is,h ydrogen bonding,i onic cross-linking, hydrophobic micelles,a nd crystalline segments) to tune their mechanical performance and physicochemical properties. [1,2] Currently, hydrogels with ahydrophilic polymer network mainly utilize reversible noncovalent polymer netpoints (that is,h ydrogen bonding,i onic cross-linking, hydrophobic micelles,a nd crystalline segments) to tune their mechanical performance and physicochemical properties.…”