A pH controlled temperature response reprogramming hydrogel for monitoring human electrophysiological signals

Bioinspired Polyacrylamide/(polyvinyl alcohol-copper acetate) Hydrogel with Cooling-triggered Shape Memory, Color Changing, and Self-healing Behavior

Inspired by many living creatures with adjustment of shape and color in ever-changing environment, color changeable shape memory hydrogels are designed and expected to be potential candidates in the fields spanning from anti-counterfeiting to biomedical devices. However, they normally require complex synthesis, and more importantly, the cooling-induced shape recovery hydrogel is still rare and in its infancy so far. Herein, we have developed a unique color changeable shape memory hydrogel by simply incorporating polyvinyl alcohol and copper acetate into covalent polyacrylamide network. As core functional element, copper ions serve as reversible crosslinks after heating to achieve excellent cooling-triggered shape memory effect, color shifting and self-healing behavior, showing significant potential in diverse applications like grabbing, information encryption, and biomimetic designs. This work may guide the development of cooling-triggered smart hydrogels for practical applications. This article is protected by copyright. All rights reserved.

The effect of promoting hydrogen bond aggregation based on PEMTC on the mechanical properties and shape memory function of polyurethane elastomers

In this work, small molecule diols named PEMTC were synthesized from isophorone diisocyanate, N-(2-hydroxyethyl)acrylamide and trimethylolpropane by a semi-directional method. PEMTC (2-(prop-2-enamido)ethyl N-{3-[({[2-ethyl-3-hydroxy-2(hydroxymethyl)propoxy]carbonyl}amino)methyl]-3,5,5-trimethylcyclohexyl}carbamate) contains hydrogen bond active site and light-initiated C=C. We introduced it as a branch chain block into poly(ε-caprolactone) (PCL). By feeding and monitoring the reaction process, we synthesized a large number of polyurethane elastomers, hydrogen bonds PCL-based elastomer (HPE), which contain a large number of dynamic hydrogen bonds. Under UV irradiation, PEMTC can make HPE molecules aggregate and cross-link, improve the degree of internal hydrogen bonding interaction of HPE materials and endow HPE materials with good elasticity, toughness, heat resistance and shape memory ability. After 270 nm UV irradiation, the elongation at break of HPE materials decreased from 607.14-1463.95% to 426.60-610.36%, but the strength at break of HPE materials increased from 3.36-13.52 to 10.28-41.52 MPa, and the toughness increased from 16.36-129.71 to 40.48-172.22 MJ m-3. In addition, the highest shape fixation rate of HPE after UV irradiation was 98.0%, and the recovery rate was 93.7%.

Fabrication of Multiresponsive Magnetic Nanocomposite Double-Network Hydrogels for Controlled Release Applications

Nanocomposite double-network hydrogels (ncDN hydrogels) have been demonstrated as promising biomaterials to present several desired properties (e.g., high mechanical strength, stimuli-responsiveness, and local therapy) for biomedicine. Here, a new type of ncDN hydrogels featuring definable microstructures and properties as well as multistimuli responsiveness for controlled release applications is developed. Amine-functionalized iron oxide nanoparticles (IOPs_NH₂ ) are used as nanoparticle cross-linkers to simultaneously connect the dual networks of gelatin (Gel) and polydextran aldehyde (PDA) through hydrogen bonding, electrostatic interactions, and dynamic imine bonds. The pH- and temperature-responsive Gel/PDA/IOP_NH₂ ncDN hydrogels present a fast release profile of proteins at acidic pH and high temperature. Besides, IOP_NH₂ also contributes the magnetic-responsiveness to the ncDN hydrogels, allowing the use of magnetic field to generate heat to facilitate the structural change of hydrogels and the subsequent applications. Taken together, a versatile ncDN hydrogel platform capable of multistimuli responsiveness and local heating for controlled release is developed for advanced biomedical applications.