Smart Hydrogels Bearing Transient Gel–Sol–Gel Transition Behavior Driven by a Biocompatible Chemical Fuel

Abstract

Chemically fueled smart supramolecular gels have been of great interest because of their unique time-dependent properties. However, the vast majority of the already developed examples undergo fueled sol−gel−sol transition, where the gel materials possess nonlinear properties and usually involve the use of toxic chemical fuels, remarkably impeding their real-life applications. Here, we report on supramolecular hydrogels that show dynamic gel−sol−gel transition behavior driven by the consumption of biocompatible cyclodextrin (CD). The addition of CD converts the static hydrogels into sols, which are capable of returning to the original gel states through the spontaneous enzymatic hydrolysis of CD. The gel−sol−gel transition process is highly dynamic and tunable. Importantly, the system resides in a stable gel state after the depletion of the fuel, which would be beneficial for its functions. As an application, the hydrogel is used as a conceptual smart adhesive for fuel-controlled adhesion of model tissues. This work may contribute to the development of biocompatible nonequilibrium materials for high-tech applications, especially in the field of biomedicine.

Dynamic supramolecular hydrogels mediated by chemical reactions

“…1(d)). [87][88][89] In this case, the hydrogels are in the equilibrium state. The chemical fuel additive will drive the hydrogels' transformation into a solution, and then the transformation will reverse to the assembly state once the fuels are depleted.…”

“…8(a)). 88 In this system, PAA grafted with octadecyl (PAA-C 18 ) was dissolved in water and a stable supramolecular hydrogel was formed due to the formation of hydrophobic C 18 aggregates. With the addition of the chemical fuel, CD, the hydrophobic C 18 aggregates disintegrated because of the formation of a host-guest complexation of CD and C 18 , resulting in a gel-sol transition.…”

“…The chemical fuel additive will drive the hydrogels’ transformation into a solution, and then the transformation will reverse to the assembly state once the fuels are depleted. We also developed a series of out-of-equilibrium hydrogels powered by carbodiimide, 90,91 sugar 88 and reaction–diffusion mediated fuels, 92 which will be discussed later in this feature article.…”

Superparamagnetic Amine-Functionalized Maghemite Nanoparticles as a Thixotropy Promoter for Hydrogels and Magnetic Field-Driven Diffusion-Controlled Drug Release

“…2−4 Hydrogels exhibiting distinct responses based on various stimuli, including temperature, pH, light, and electric or magnetic fields, are classified as "smart" hydrogels. 5,6 A variety of intelligent hydrogels have been extensively studied in order to explore their potential use as controlled medication delivery systems. 7,8 These smart stimuliresponsive materials vary their volume in response to external factors like pH, 9−12 temperature, 13,14 magnetic field, 15,16 etc.…”

Transient Assembly of Macroscopically Structured Supramolecular Hydrogels Driven by Shaped Chemical Fuels

“…However, with the dissipation of fuels, the assembled materials spontaneously disintegrate over time, showing intrinsic dynamics. So far, various dynamic supramolecular objects have been created, such as hydrogels, − vesicles or droplets, − and others − driven by methylating agents, carbodiimide, pH regulators, and GTP/ATP. Scientists have also demonstrated access to dynamic supramolecular patterns by spatially distributing fuel solutions on a solid surface. ,, To date, chemically fueled dissipative self-assembly is often associated with the direct use of liquid fuel solutions, giving rise to bulk supramolecular materials lacking macroscopic structures.…”