Stack-Based Hydrogels with Mechanical Enhancement, High Stability, Self-Healing Property, and Thermoplasticity from Poly(l-glutamic acid) and Ureido-Pyrimidinone

Abstract

Supramolecular hydrogels formed by noncovalent bonds are attractive “smart” materials, which can rapidly respond to external stimuli. However, only a handful of supramolecular hydrogels is applicable in tissue engineering, due to the instability and poor mechanical strength of noncovalent cross-linking hydrogels. Thus, a rigid and stable supramolecular hydrogel has been developed based on poly­(l-glutamic acid) and 2-ureido-4­[1H]­pyrimidinones (UPy), and the UPy stacks are noncovalent cross-linking interactions. The hydrogels show excellent mechanical strength and stability, in sharp contrast to noncovalent hydrogels cross-linked by UPy dimers and covalent hydrogels cross-linked by esterification. The hydrogels also exhibit remoldability, self-healing, and thermoplastic printing characteristics, which are caused by the reversible supramolecular property of UPy stacks. Also, the formation of hydrogels dependent on UPy stacks is further investigated by atomic force microscope, small-angle X-ray scattering, in situ X-ray diffraction, circular dichroism, and UV–vis spectroscopies. Finally, the hydrogels show commendable biocompatibility and degradability, which have high potential applications in regenerative medicine.

Integrative lymph node-mimicking models created with biomaterials and computational tools to study the immune system

“…Hydrogel is a type of soft material with interpenetrating 3D natural/synthetic networks swollen in water [ 47 , 53 , 54 ]. As hydrogels can be programmed to exhibit nature biomechanical and biochemical properties similar to natural tissues and organs, they have therefore, been extensively used to model human organs for drug development and screening [ [55] , [56] , [57] ].…”

Desired properties and corresponding improvement measures of electrospun nanofibers for membrane distillation, reinforcement, and self‐healing applications

“…Owing to the intrinsic fast dynamics of networks, high mobility of molecular chains, and vulnerability of dynamic covalent bonds to humidity, the functional integrity of self-healing materials is compromised. [160][161][162][163][164] The addition of self-healing nanofibers to composites can greatly improve their mechanical properties. Lee et al co-electrospun core-shell nanofiber mats that consisted of two different healing agents.…”

“…Owing to the intrinsic fast dynamics of networks, high mobility of molecular chains, and vulnerability of dynamic covalent bonds to humidity, the functional integrity of self‐healing materials is compromised. [ 160–164 ]…”

A Brief Overview on Preparation of Self-Healing Polymers and Coatings via Hydrogen Bonding Interactions

“…Hydrogen bonded dimerization of ureidopyrimidone (UPy) monomer was first reported by Meijer [69,70] and has been used in numerous supramolecular polymers with distinct properties and applications. UPy motifs that dimerize strongly via quadruple hydrogen bonds have been demonstrated to synthesize self-healing materials [71][72][73][74][75]. Ren Liu et al [76] introduced a combined system where curing was achieved through UV irradiation and self-healing through UPy based dynamic quadrupolar hydrogen bonds.…”