Self-healable hydrogels with crosslinking induced thermo-responsiveness and regulated properties from water soluble polymer

Poly(aspartic acid) based self-healing hydrogels with antibacterial and light-emitting properties for wound repair

We report here a self-healing hydrogel with antibacterial and light-emitting properties for wound repair. The hydrogel was prepared by reaction of poly(aspartic acid) (PASP) derivatives bearing groups of quaternary ammonium and boronic acid with poly(vinyl alcohol) (PVA). Due to the dynamic nature of boronic ester bonds, bacteria-killing activity of quaternary ammonium, and light-emitting activity of phenylboronic ester, the resultant hydrogels featured self-healing, antibacterial and light-emitting properties. The hydrogels show controlled release behavior of mouse epidermal growth factor (mEGF) and the in vivo studies show mEGF loaded hydrogel accelerate the wound repair of model mice and improve skin cell proliferation by prevention of bacterial infections. The PASP based hydrogels would show great promise in bio-applications, in particular for wound dressing and tissue repairing.

Flexible Self-Repairing Materials for Wearable Sensing Applications: Elastomers and Hydrogels

Flexible pressure and strain sensors have great potential for applications in wearable and implantable devices, soft robots, and artificial skin. The introduction of self-healing performance has made a positive contribution to the lifetime and stability of flexible sensors. At present, many self-healing flexible sensors with high sensitivity have been developed to detect the signal of organism activity. The sensitivity, reliability, and stability of self-healing flexible sensors depend on the conductive network and mechanical properties of flexible materials. This review focuses on the latest research progress of self-healing flexible sensors. First, various repair mechanisms of self-healing flexible materials are reviewed because these mechanisms contribute to the development of self-healing flexible materials. Then, self-healing elastomer flexible sensor and self-healing hydrogel flexible sensor are introduced and discussed respectively. The research status and problems to be solved of these two types of flexible sensors are discussed in detail. Finally, this rapidly developing and promising field of self-healing flexible sensors and devices is prospected.

Self-healing hydrogel with cross-linking induced thermo-response regulated light emission property

With increasing attention paid to smart materials, self-healing hydrogels with thermo-responses have been greatly developed in the past several years. At the same time, fluorescent or light emitting polymers have been studied for use as bioimaging tools and drug delivery vehicles. In this research, thermo-responsive self-healing hydrogels with aggregation-induced emission (AIE) property were prepared from tetraphenylethylene (TPE) containing TPE-poly(N,N-dimethylacrylamide-stat-Diacetone acrylamide) [TPE-P(DMA-stat-DAA)] cross-linked by diacylhydrazide. In addition to self-healing based on reversible acylhydrazone bond, the copolymer and hydrogels showed thermo-responses. The lower critical solution temperature (LCST) of the hydrogels was regulated to body temperature. Based on the AIE property of the TPE unit, the hydrogels showed an enhanced light emitting property above the LCST, which was regulated by temperature change. The in vitro cytotoxicity experiment showed that the hydrogels are not toxic, and the DOX release rate can be enhanced by low pH values, which endowed this kind of thermo-responsive light emitting hydrogel with great potential for applications in bio-diagnosis, drug delivery, artificial organs with light sensitive detection, etc.

Self-Healing Hydrogels with both LCST and UCST through Cross-Linking Induced Thermo-Response

Self-healing hydrogels have drawngreat attention in the past decade since the self-healing property is one of the characteristics of living creatures. In this study, poly(acrylamide-stat-diacetone acrylamide) P(AM-stat-DAA) with a pendant ketone group was synthesized from easy accessible monomers, and thermo-responsive self-healing hydrogels were prepared through a series of diacylhydrazide compounds cross-linking without any additional stimulus. Although the copolymers do not show thermo-response, the hydrogels became thermo-responsive andboth the lower critical solution temperature (LCST) and upper critical solution temperature (UCST) varied with the composition of the copolymer and structure of cross-linkers. With a dynamic covalent bond connection, the hydrogel showed gel-sol-gel transition triggered by acidity, redox, and ketone to acylhydrazide group ratios. This is another interesting cross-linking induced thermo-responsive (CIT) hydrogel with different properties compared to PNIPAM-based thermo-responsive hydrogels. The self-healing hydrogel with CIT properties could have great potential for application in areas related to bioscience, life simulation, and temperature switching.

Temperature-regulated aggregation-induced emissive self-healable hydrogels for controlled drug delivery

Thermoresponsive copolymers TPE-[P(DMA-stat-DAA)]₂ containing a tetraphenylethylene (TPE) moiety and a ketone group were synthesized.