Convergent synthesis of diversified reversible network leads to liquid metal-containing conductive hydrogel adhesives

Yong Xu,Martin Bornhäuser,Dagmar Voigt,Michelle Patino Gaillez,Jens Pietzsch,Thomas Kurth,Meiying Cui,Rebecca Rothe,Sandra Hauser,Yixin Zhang,Takuya Miyagawa

doi:10.1038/s41467-021-22675-2

Abstract

Many features of extracellular matrices, e.g., self-healing, adhesiveness, viscoelasticity, and conductivity, are associated with the intricate networks composed of many different covalent and non-covalent chemical bonds. Whereas a reductionism approach would have the limitation to fully recapitulate various biological properties with simple chemical structures, mimicking such sophisticated networks by incorporating many different functional groups in a macromolecular system is synthetically challenging. Herein, we propose a strategy of convergent synthesis of complex polymer networks to produce biomimetic electroconductive liquid metal hydrogels. Four precursors could be individually synthesized in one to two reaction steps and characterized, then assembled to form hydrogel adhesives. The convergent synthesis allows us to combine materials of different natures to generate matrices with high adhesive strength, enhanced electroconductivity, good cytocompatibility in vitro and high biocompatibility in vivo. The reversible networks exhibit self-healing and shear-thinning properties, thus allowing for 3D printing and minimally invasive injection for in vivo experiments.

Highlights

Many features of extracellular matrices, e.g., self-healing, adhesiveness, viscoelasticity, and conductivity, are associated with the intricate networks composed of many different covalent and non-covalent chemical bonds
An opaque slurry was generated after 30 min of sonication, and stable Eutectic gallium–indium (EGaIn) nanodroplets were obtained after washing and size-grading
The transmission electron microscopy (TEM) images demonstrate that the liquid metals (LM) nanodroplets were welldispersed (Fig. 1c) and showed a core–shell structure with tannic acid (TA) as hydrophilic coating

Summary

Introduction

Many features of extracellular matrices, e.g., self-healing, adhesiveness, viscoelasticity, and conductivity, are associated with the intricate networks composed of many different covalent and non-covalent chemical bonds. In contrast to the rigid metal nanoparticles, LMs provide unique features to create soft, injectable, and cytocompatible conductive materials for many biomedical applications, such as drug delivery and wearable electronics[19,21,22,23] For many applications, such as wearable bioelectronics[24], wound dressing[25], tissue engineering[26], and drug delivery[27], a hydrogel needs to adhere firmly to substrate surfaces under either dry or wet conditions. The synergy among different types of chemical bonds, including covalent imine bond (Schiff base), hydrogen bond, π–π/anion–π/ cation–π interaction, and electrostatic interaction, has resulted in reliable adhesive strength comparable to clinically used fibrin glue The reversibility of these interactions has led to selfassembled biomatrices, which can be used to encapsulate cells for 3D cell culture, as well as injectable materials for biocompatibility tests in mice

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Results

Conclusion