Mussel-Inspired Adhesive and Tough Hydrogel Based on Nanoclay Confined Dopamine Polymerization

Abstract

Adhesive hydrogels are attractive biomaterials for various applications, such as electronic skin, wound dressing, and wearable devices. However, fabricating a hydrogel with both adequate adhesiveness and excellent mechanical properties remains a challenge. Inspired by the adhesion mechanism of mussels, we used a two-step process to develop an adhesive and tough polydopamine-clay-polyacrylamide (PDA-clay-PAM) hydrogel. Dopamine was intercalated into clay nanosheets and limitedly oxidized between the layers, resulting in PDA-intercalated clay nanosheets containing free catechol groups. Acrylamide monomers were then added and in situ polymerized to form the hydrogel. Unlike previous single-use adhesive hydrogels, our hydrogel showed repeatable and durable adhesiveness. It adhered directly on human skin without causing an inflammatory response and was easily removed without causing damage. The adhesiveness of this hydrogel was attributed to the presence of enough free catechol groups in the hydrogel, which were created by controlling the oxidation process of the PDA in the confined nanolayers of clay. This mimicked the adhesion mechanism of the mussels, which maintain a high concentration of catechol groups in the confined nanospace of their byssal plaque. The hydrogel also displayed superior toughness, which resulted from nanoreinforcement by clay and PDA-induced cooperative interactions with the hydrogel networks. Moreover, the hydrogel favored cell attachment and proliferation, owning to the high cell affinity of PDA. Rat full-thickness skin defect experiments demonstrated that the hydrogel was an excellent dressing. This free-standing, adhesive, tough, and biocompatible hydrogel may be more convenient for surgical applications than adhesives that involve in situ gelation and extra agents.

Tough Adhesion of Nucleobase‐Tackifed Gels in Diverse Solvents

“…[17][18][19] However, most works only focused on the adhesion behavior in air and/or water, the technology of strong adhesion and acrylate adenine were utilized to fabricate adhesive gels via the radical polymerization in the mixed solvents of water and DMSO. [31,32] A huge challenge for achieving a robust adhesion interface in various solvents was resisting the swelling stress and dissolution from the solvent medium. [29,30] As shown in Figure 1b, the gels presented a robust tensile strength of 47 kPa and toughness of 300 kJ m −3 at the high stain of 1520%.…”

Graphene Oxide Hybrid Supramolecular Hydrogels with Self‐Healable, Bioadhesive and Stimuli‐Responsive Properties and Drug Delivery Application

“…For the potential biomedical applications, however, it may require the self‐healable hydrogels to demonstrate good biocompatibility, and more important to have a combination of multifunctions, for example, the adhesive ability to tissues and substrates in wound closure, electronic skin, and biosensor applications . Currently, the majority of adhesive hydrogels have been prepared based on the inspiration from natural marine mussels . In nature, subsequent to the secretion of mussel adhesive protein, the oxidation of catechol side chains of 3,4‐dihydroxy‐phenylalanine (DOPA) leads to the intermolecular coupling of mussel adhesive proteins and excellent adhesion to solid surfaces.…”

Multipurpose and Durable Adhesive Hydrogel Assisted by Adenine and Uracil from Ribonucleic Acid

“…Hydrogels, which are formed by crosslinking hydrophilic polymer chains in an aqueous medium, are fascinating materials because of their resemblance to biological tissues . Adhesive hydrogels have attracted considerable attention in various fields, such as 3D printing, wound dressing, tissue adhesive and wearable devices . However, traditional hydrogels exhibit the weak adhesive ability for substrates because of the lack of suitable adhesive interacting sites with covalent and noncovalent interactions.…”

“…Among them, physical adhesion has drawn much attention for the design of universal adhesive hydrogels because of the simple processes involved in their operation and their widespread applications. The physical adhesion depends on noncovalent interactions, such as hydrogen bonding, metal complexation, hydrophobic effects, π–π stacking and cation–π interactions . The reversible features of physical interactions play an important role in the introduction of repeated adhesive behaviour.…”

“…Mussel‐inspired strategies provide impressive inspiration for adhesive materials based on the various molecular recognition of catechol molecules . However, catechol‐based adhesive hydrogels have suffered from weak adhesion ability and the catechol is easily oxidised to quinone, leading to a decline in the level of adhesive behaviour . To design hydrogels with strong and durable adhesive properties, therefore, some novel adhesive molecules should be considered to develop a new generation of adhesive hydrogels.…”