A Highly Stretchable, Real‐Time Self‐Healable Hydrogel Adhesive Matrix for Tissue Patches and Flexible Electronics

Abstract

The development of biocompatible self‐healable hydrogel adhesives for skin or wet, stretchable surfaces in air or under water is highly desirable for various biomedical applications ranging from skin patches to bioelectronics. However, it has been proven to be very challenging because most existing hydrogel adhesives are cytotoxic, or poorly adhere to dynamic or stretchable surfaces in wet environments. In this study, multifunctional hydrogel adhesives derived from silk fibroin (SF) and tannic acid (TA) are effectively constructed with high extensibility (i.e., up to 32 000%), real‐time self‐healing capability, underwater adhesivity, water‐sealing ability, biocompatibility, and antibiotic properties. According to all‐atom molecular dynamics simulation studies, the properties of the hydrogel adhesives, especially high extensibility, are mainly attributed to the hydrogen bonds between TA and the SF chains in water, and water and TA molecules can result in loose assemblies with fewer β‐sheets, and more random coils in the SF. Conductivity can also be easily introduced to the adhesive matrix and adjusted when the strain of the adhesives occurs. Considering that it has multiple functions and can be efficiently prepared, the proposed hydrogel adhesives have the potential for future medical applications, such as tissue adhesives and integrated bioelectronics.

Functional silk fibroin hydrogels: preparation, properties and applications

“…It can be observed from the literature that the popular way to prepare the silk fibroin selfhealing hydrogels employing the dynamic chemical bonds is mainly based on the introduction of the amide and catechol groups as well as the generation of the dynamic diol-borate ester bonds. For instance, Jun Luo et al 73 developed the SF/ tannic acid (TA) composite hydrogel. Owing to the reversible hydrogen bonding interaction between the amide group of SF and polyphenol group of TA, the resulting SF/TA composite hydrogel exhibited the self-healing function.…”

“…In addition to the ionic and carbon-based nanocomposite hydrogels, the conductive polymer hydrogels also represent an important class of materials. Jun Luo et al 73 introduced the conductive polymer poly(3,4-ethylene dioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) in the SF/TA hydrogel. The obtained hydrogel could brighten a small lamp.…”

Medical Applications Based on Supramolecular Self-Assembled Materials From Tannic Acid

“…Adatoz et al ( 2018 ) prepared hydrogen-bonded and pH-responsive poly(2-ethyl-2-oxazoline) (PEOX) and TA multilayers by LbL deposition, which can be reassembled into H-bonded pH-responsive PEOX/TA fibers in phosphate buffer solution, pH 3, validating that pH-responsive fiber aggregates have certain application prospects in a variety of biomedical applications from controlled release to sensors. Luo et al ( 2020 ), using silk fibroin (SF) and TA as raw materials, effectively constructed multifunctional hydrogel adhesives with high extensibility (up to 32,000%), real-time self-healing ability, underwater adhesion, sealing, biocompatibility, and antibacterial properties, through the hydrogen bonding of TA and SF chains in water, which has potential applications in medical fields such as tissue adhesives and integrated bioelectronics, as shown in Figure 6B . Although the polyhydroxyl structure of TA can provide relatively stable hydrogen bonds under physiological conditions due to the inherent limitations of the hydrogen-bond structure, it is greatly affected by pH, ionic strength, and other factors.…”

“…(A) PTX-NP assembled by intermolecular hydrogen-bonded interactions have features including P-gp inhibitory functions and pH-sensitive behavior (Le et al, 2018 ). (B) The formation schematic of the FT hydrogel adhesive (dominated by hydrogen-bond interactions) (Luo et al, 2020 ).…”

Ultra-fast self-gelling powder mediate robust wet adhesion to promote healing of gastrointestinal perforations

“…Adhesive hydrogels that can strongly adhere to wet tissues have been widely used in wound dressings, [1][2][3][4][5] hemostatic agents, [6][7][8][9][10] wearable devices, [11][12][13] drug delivery systems, 14,15 and tissue engineering, [16][17][18][19][20][21] owing to their strong adhesion, excellent biocompatibility, good permeability, high deformability, and tunable mechanical properties. Two main hydrogel design strategies have been adopted to achieve adhesion on wet tissues: adhering prefabricated adhesive hydrogels [22][23][24][25][26][27][28][29] on wet tissues and forming adhesive hydrogels on wet tissues in situ from precursor solutions.…”