Universal Strategy for Designing Shape Memory Hydrogels

Abstract

Smart polymeric biomaterials have been the focus of many recent biomedical studies, especially those with adaptability to defects and potential to be implanted in the human body. Herein we report a versatile and straightforward method to convert non-thermoresponsive hydrogels into thermoresponsive systems with shape memory ability. As a proof of concept, a thermoresponsive polyurethane mesh was embedded within a methacrylated chitosan (CHTMA), gelatin (GELMA), laminarin (LAMMA) or hyaluronic acid (HAMA) hydrogel network, which afforded hydrogel composites with shape memory ability. With this system, we achieved good to excellent shape fixity ratios (50–90%) and excellent shape recovery ratios (∼100%, almost instantaneously) at body temperature (37 °C). Cytocompatibility tests demonstrated good viability either with cells on top or encapsulated during all shape memory processes. This straightforward approach opens a broad range of possibilities to convey shape memory properties to virtually any synthetic or natural-based hydrogel for several biological and nonbiological applications.

A Supramolecular Injectable Methacryloyl Chitosan‐Tricine‐Based Hydrogel with 3D Printing Potential for Tissue Engineering Applications

“…CHTMA was initially synthesized through a nucleophilic substitution reaction between CHT and methacrylic acid (MA), promoted by carbodiimide chemistry. [ 20 ] After a 24 h‐reaction period, the reaction mixture was purified in 7‐day long dialysis and after freeze‐drying, CHTMA was obtained as a white solid in 84% yield and 17% substitution degree (SD). The methacryloyl moieties’ insertion onto the CHT's backbone was confirmed and quantified by 1 H nuclear magnetic resonance (NMR), and the obtained results were in good agreement with the reported data.…”

“…Furthermore, methacryloyl chitosan (CHTMA) has been reported as a platform to develop cytocompatible systems. [19][20][21] However, there's a lack of single-network CHT derivatives that can be fully solubilized in aqueous solutions at physiological pH (pH 7.4), while maintaining cytocompatibility and reinforcing the poor mechanical properties typically associated with single-networking CHT-based systems. Tricine, or N-[Tris(hydroxymethyl)methyl]glycine, [22] is an amino acid with antioxidant properties usually applied in the fields of biomedicine and physiology.…”

Programmable Thermo‐Responsive Actuation of Hydrogels via Light‐Guided Surface Growth of Active Layers on Shape Memory Substrates

“…Hydrogels exhibiting shape memory functionalities, known as shape memory hydrogels (SMHs), represent another class of stimuli-responsive hydrogels that can controllably vary their shapes. [16][17][18] Theoretically, the shape memory effect is based on the controlled formation and dissociation of intermolecular interactions for strain fixation and relaxation. [19][20][21][22][23][24][25] One SMH can be conveniently programmed into different temporary shapes in different cycles and later recover to its original shape, presenting high flexibility of the shape-changing behaviors.…”

Synergy of Hofmeister effect and ligand crosslinking enabled the facile fabrication of super-strong, pre-stretching-enhanced gelatin-based hydrogels

“…The introduction of reversible physical cross-linking is an effective way to impart excellent fatigue resistance and shape recovery capability to hydrogels. 24…”

“…The introduction of reversible physical cross-linking is an effective way to impart excellent fatigue resistance and shape recovery capability to hydrogels. 24 Gelatin is a widely used biopolymer that can be obtained by hydrolyzing collagen from animal epidermis, such as pigs, cattle, and fish. Gelatin has good biocompatibility and its side chains contain a large number of hydroxyl and amino groups, and other reactive groups, which are widely used in wound dressing, 25,26 drug delivery, 27 and the food industry.…”