Acylhydrazone Bonds Research Articles

Enteromorpha Prolifera Polysaccharide-Derived Injectable Hydrogel for Fast Intraoperative Hemostasis and Accelerated Postsurgical Wound Healing Following Tumor Resection.

Intraoperative bleeding and delayed postsurgical wound healing caused by persistent inflammation can increase the risk of tumor recurrence after surgical resection. To address these issues, Enteromorpha prolifera polysaccharide (PEP) with intrinsic potentials for hemostasis and wound healing, is chemically modified into aldehyde-PEP and hydrazine-PEP. Thereby, an injectable double-network hydrogel (OPAB) is developed via forming dual dynamic bonding of acylhydrazone bonds between the decorated aldehyde and hydrazine groups and hydrogen bonds between hydroxyl groups between boric acid and PEP skeletons. The OPAB exhibits controllable shape-adaptive gelation (35.0 s), suitable mechanical properties, nonstimulating self-healing (60 s), good wet tissue adhesion (30.9kPa), and pH-responsive biodegradability. For in vivo models, owing to these properties, OPAB can achieve rapid hemostasis within 30 s for the liver hemorrhage, and readily loading of curcumin nanoparticles to remarkably accelerate surgical wound closure by alleviating inflammation, re-epithelialization, granulation tissue formation, and collagen deposition. Overall, this multifunctional injectable hydrogel is a promising material that facilitates simultaneous intraoperative hemorrhage and postsurgical wound repair, holding significant potential in the clinical managements of bleeding and surgical wounds for tumor resection.

Rapid self-healing carboxymethyl chitosan/hyaluronic acid hydrogels with injectable ability for drug delivery

In this study, the quaternized carboxymethyl chitosan (QCMCS), oxidized hyaluronic acid (OHA), 3,3′-dithiobis-(propionohydrazide) (DTP) were used as raw materials for the synthesis of hydrogels with excellent properties as carriers for drug release. The hydrogels were prepared by a simple “one-pot” method without external stimuli on the basis of interactions between formed dynamic covalent bonds (imine bonds, acylhydrazone bonds, disulfide bonds) and hydrogen bonds. The hydrogels had rapid self-healing properties, with a self-healing rate of 96 % after 30 min, as well as good pH responsiveness and excellent cytocompatibility (up to 98 % cell survival). The compressive stress of the hydrogels reached 423 kPa. Moreover, a representative drug (acetylsalicylic acid) demonstrated sustained release in the hydrogels (>72 h). The drug release behaviour was shown to be consistent with the Fick diffusion mechanism by kinetic modelling. Collectively, the findings demonstrate that the QCMCS + OHA + DTP injectable self-healing hydrogels are a potential material for the construction of pH-controlled drug delivery platforms.

Dynamic covalent hydrogel fabricated in porous media through dynamic acylhydrazone bond from reactive precursors for deep profile control

In this work, we proposed a novel hydrogel system for in-depth conformance control through the dynamic covalent bond. Diffluent ketone-bearing and acyl hydrazide-bearing reactive precursors with low molecular weight are injected into the formation simultaneously, then gels in situ through dynamic hydrazone bonds to divert the post-injected fluid to un-swept oil zones. Ketone-bearing and acyl hydrazide-bearing reactive precursors with different reactive group ratios were synthesized by simple radical polymerization and hydrazinolysis. Rheological measurement results proved the two reactive precursors formed dynamic covalent hydrogel (DCG) through dynamic hydrazone bonds in deionized water and mineralized water. The viscoelasticity, flow behavior, and profile control behavior in the porous media of the DCG were evaluated. When the flow behavior and profile control experiments were conducted with a 9 m core, the injection pressure of DCG-20 % of which the molar ratio of the reactive group was 20 % was low (0–0.22 MPa) throughout the injection process, and the resistance factor was 4.40. After fully gelation, the post-water injection pressure significantly increased (0.22–7.54 MPa). The residual resistance factor was 150.80, and the plugging efficiency was 99.34 %. This work proved that the DCG consisting of ketone-bearing and acyl hydrazide-bearing reactive precursors not only had a strong injection capacity but also had a good profile control effect in porous media which meant the DCG fully met the need for deep profile control.

High‐performance vitrimer films containing acylhydrazone dynamic covalent bonds

AbstractVitrimer films containing acylhydrazone bonds are synthesized in two steps. Bio‐based vanillin and adipate dihydrazide are used to prepare diols containing acylhydrazone bonds in one step, which are introduced into the reaction system of vitrimer to obtain the final films. The process is concise and easy to operate. By utilizing the rigid structure of vitrimer films and introducing dynamic acylhydrazone bonds, the obtained vitrimer films exhibit strong mechanical strength (maximum tensile strength of 27.10 MPa and maintaining up to 185.52% of the original breaking strength), excellent self‐healing property (tensile strength of 26.26 MPa after 12 h of primary self‐healing and 5.24 MPa after 12 h of secondary self‐healing), and rapid shape memory property (recovery time of about 2 min), strong acid and alkali resistance (not dissolved within 24 h), good thermal stability (no decomposition occurs below 160 °C), and high storage modulus (reaches 1087 MPa). These comprehensive benefits yield a certain reference for the preparation of vitrimer materials with prime properties.

Synthesis of oxidized carboxymethyl cellulose/chitosan hydrogels doped with graphene oxide for pH- and NIR-responsive drug delivery

Biological macromolecules hydrogels are synthesized via the Schiff base reaction between oxidized carboxymethyl cellulose (oxCMC) and chitosan (CS), and graphene oxide (GO) and 5-fluorouracil (5-FU) are co-doped in the oxCMC/CS hydrogels during the cross-linking process. The acylhydrazone bonds (–HC = N–) between oxCMC and CS can be easily hydrolyzed in acidic solutions, leading to the swelling of the hydrogels and facilitated delivery of 5-FU. On the other hand, the doped GO is a promising photothermal agent, and the delivery of 5-FU can also be facilitated by the generated hyperthermia upon near infrared (NIR) irradiation. Therefore, pH- and NIR-responsive delivery of 5-FU from the hydrogels can be achieved. The kinetics of drug delivery indicate that the delivery of 5-FU from the hydrogels is controlled by first-order model. The drug-free carrier (oxCMC/CS/GO) has excellent biocompatibility while the developed drug delivery system (oxCMC/CS/GO/5-FU) exhibits high cytotoxicity against human hepatoma SMMC-7721 cells.

Dynamic acylhydrazone bonds cross-linked chromotropic photonic-ionic skin with self-healing and high resilience for interactive human-machine interface

Advanced skin systems realize perception and interaction with the environment through synergistic electrical and color signals generated by transmitting ions and manipulating photonic structures. Here, inspired by chameleon skins, a novel self-healing and resilient photonic-ionic skin (PI-skin) with electro-optical dual response is ingeniously constructed integrating the ordered micro-nano array and the dynamically covalently cross-linked ionogel. The elaborately designed polycation network with weak inter-chain interactions can promote the uniform distribution of high-content low-viscosity ionic liquid (IL), effectively eliminating energy dissipation and resulting in high resilience. Dynamic acylhydrazone bonds are served as reversible chemical crosslinking to realize high-efficiency self-healing and further enhance resilience. Notably, the artificially manipulated transition of the photonic array from dense packing to non-dense packing endows sensitive chromotropic properties synchronized with electrical response under stretched (Δλ > 130 nm) and compressed (Δλ > 160 nm). Furthermore, by harnessing the correspondence between electrical and optical signals, the control of optical signals over electrical signals is achieved for inputting complex coded information and constructing interactive human–machine interfaces. This work not only inspires the design and construction of high-level artificial skins but also stimulates the development of visual interactive devices and smart electronic/ionic products.

Nucleus-targeting orange-emissive carbon dots delivery adriamycin for enhanced anti-liver cancer therapy

Carbon dots (CDs) with precise targeting function show great potential in the field of drug delivery therapeutics. In this study, the functionalized nucleus-targeting orange-emissive CDs with nuclear localization sequence (NLS) were loaded with adriamycin (DOX) to obtain a nucleus-targeting orange-emissive CDs drug delivery system (CDs-NLS-DOX), which delivered DOX to tumor cell nuclei to enhance its anti-tumor activity. The drug carrier orange-emissive CDs showed excitation-independent behavior, stable and enhanced imaging capability and good biocompatibility in vitro and in vivo. Meanwhile, the CDs-NLS could target the nuclei efficiently, and the CDs-NLS-DOX complexes had a high drug loading rate (59.4%) after loading DOX, exhibiting pH-dependent DOX release behavior through breaking acylhydrazone bond in a weak acidic environment. In addition, the CDs-NLS-DOX complexes exhibited an enhanced killing activity against human hepatoma cells (HepG2). The in vivo therapeutic effects on HepG2 nude mice transplanted tumors indicated the CDs-NLS-DOX had a stronger ability to inhibit tumor growth compared to free DOX. In short, CDs-NLS-DOX is expected to be a precise and efficient nucleus-targeting nano-drug delivery system for tumor treatment.

A series of novel 1H-indole-7-carbohydrazide derivatives with photoswitching and AIE properties: “On-off” fluorescence sensors for Cu2+

In order to exploit novel fluorescent sensors with photoswitching properties, six fluorescent molecules were synthesized via coupling 1H-indole-7-carbohydrazide and corresponding substituted formaldehyde through an acylhydrazone bond. All title compounds were characterized via1H, 13C NMR, and elemental analysis, the single crystal structure of compound IC-PD was obtained via X-ray diffraction. The compounds IC-EL and IC-4PZ exhibited aggregation-induced emission (AIE) characteristics and also with regular responses to temperature and alkalinity in the solvent system dominated via deionized water. Probes IC-PL, IC-4PZ, and IC-PD could be used as fluorescence probes to detect copper (Ⅱ) with the LODs of 0.37, 0.27, and 0.26 μM in concentration of 0–50 μM, especially extraordinary bits of complex IC-PD-Cu2+ could also exhibited bright yellow in tetrahydrofuran (THF), which ensured the convenience of detection for Cu2+ ion. The exploration on the combination mechanism of representative compound IC-PD and Cu2+ ion via FT-IR and 1H NMR, which confirmed that the proton of hydrazide was protonated via Cu2+ ion, resulting in the excited state intramolecular proton transfer (ESIPT) process was interfered. When IC-PD was irradiation to the 302 nm photostationary state (PSS), the fluorescence emission intensity of IC-PD in THF was slightly enhanced, accompanied with the increased sensitivity of detection for Cu2+. Although the improvement was not significant, it was also provided a design foundation for the development of stimuli responsive fluorescent materials with photoswitching properties.

Synthesis of the pH-sensitive nanoparticles based on the acylhydrazone bonds conjugated doxorubicin and studies on their in vivo anti-tumor effects

The purpose of this study was to synthesize DHPD polymers through the conjugation of doxorubicin (DOX) molecules onto poly(ethylene glycol) (PEG) chains via acylhydrazone bonds, and to fabricate pH-responsive DHPD nanoparticles (NPs) for investigation of their biosecurity and in vivo anti-tumor activity. The morphology, size distribution, stability, pH-responsiveness, biosecurity, and in vivo anti-tumor effects of the DHPD NPs were evaluated. Characterization of the DHPD polymers using 1H NMR, FTIR, and Raman spectra confirmed their successful synthesis. The DHPD NPs exhibited a round morphology with an average diameter of 144.4 ± 1.7 nm and a polydispersity index (PDI) of 0.23 ± 0.02. Biosecurity studies indicated that the DHPD NPs were non-toxic to treated mice, and in vitro cell tests demonstrated their ability to be taken up by 4T1 cells. Under the acidic microenvironment of 4T1 cells, the acylhydrazone bonds were cleaved, resulting in increased DOX delivery to tumor cells and improved in vivo anti-tumor effects. Animal experiments confirmed that the DHPD NPs reduced DOX toxicity while enhancing its anti-tumor activity. Furthermore, results from the analysis of γ-interferon (INF-γ), tumor necrosis factor-α (TNF-α), epidermal growth factor (EGF), and vascular endothelial growth factor (VEGF) indicated that the DHPD NPs improved the anti-4T1 tumor effect of DOX, suggesting their potential application in the treatment of breast cancer.

Injectable multifunctional carboxymethyl chitosan/hyaluronic acid hydrogel for drug delivery systems

Injectable hydrogels with notable mechanical properties and self-healing ability are promising carriers for use as a drug delivery system. Here, adipic acid dihydrazide (ADH) and calcium ions (Ca2+) were introduced into quaternary ammonium carboxymethyl chitosan and aldehyde-modified hyaluronic acid hydrogels (QCS + OHA). The hydrogels were synthesized through the interaction of the Schiff bases (imine bonds, acylhydrazone bonds) and coordination bonds via a facile one-step approach. The gelation time (∼54 s) ensured excellent injectability. The QCS + OHA + ADH + Ca2+ hydrogel had notable mechanical properties (compressive stress up to 896.30 KPa), good self-healing ability (up to 94 %), good pH responsiveness, and excellent antibacterial properties. In addition, the QCS + OHA + ADH + Ca2+ hydrogel had a high drug loading capacity (121.3 mg/g) and sustained drug release behaviour (≥120 h). The results of cytotoxicity tests showed a high cell proliferation rate (up to 98 %) and good cytocompatibility. In summary, this work presents an injectable and self-healing pH-responsive hydrogel that can be used as a carrier for drug delivery systems.

Novel salicylic acid derivatives connecting to five-membered cycle through an acyl hydrazone bond as multi-stimuli responsive fluorescent smart materials with photoswitching properties

In order to exploit novel multi-stimuli responsive fluorescent materials, a series of novel fluorescent molecules of salicylic acid derivatives were designed and synthesized via introducing pyrazole or cyclopentane to the salicylic acid scaffold through a special Schiff base–acylhydrazone, and the molecular structures of representative compounds A2 and A4 were verified via single crystal X–ray diffraction. All title molecules could exhibit obvious solvatofluorochromism from cyan to indigo in several solutions with different polarity. The fluorescence titration data exhibited compound A2 and complex A2-Cu2+ with prime detection limits to Cu2+ (0.24 μM) and S2- ions (2.83 μM). The sensitive recognition of A2 to trifluoroacetic (TFA) and A2-TFA to triethylamine (TEA) were also confirmed via fluorescent titration experiments in various solutions, respectively. What’s more, the 1H NMR and UV/Vis absorption spectra further explained the mechanism between molecules and ions or molecules and TFA/TEA. Besides, the photoswitching properties of the compounds A2 and A3 could be demonstrated via the irradiation of special wavelength light or heating accompanied with changes in quantum yields. In addition, these phenomena of multiple responses were explained via Density Functional Theory (DFT) based on the Gaussian calculations. Thus, this work provided a preliminary basis for the research of multi-stimuli responsive fluorescent molecules with photoswitching properties.

Highly stretchable, fast self-healing nanocellulose hydrogel combining borate ester bonds and acylhydrazone bonds

Self-healing hydrogels have received considerable attention as a promising material for flexible electronic devices given their mechanical durability and structurally tunable properties. In this study, a highly stretchable self-healing hydrogel with dual cross-linking network was developed via borate ester bonds generated by polyvinyl alcohol and borax, and acylhydrazone bonds formed by aldehyde nanocellulose with adipic acid dihydrazide-modified alginate. Compared with the single network hydrogel composed of polyvinyl alcohol and borax, the introduction of dynamic acylhydrazone bonds greatly increases the flexibility of the hydrogel. The elongation rate increased from 480 % to approximately 1440 %, and the self-healing efficiency increased from 84.6 % to 92.7 % after healing for 60 min at ambient temperature without any stimulus. Moreover, the longer the self-healing time, the more evident the self-healing effect of the acylhydrazone bonds. In addition, electrical measurements confirmed a wide working strain range (ca.1000 %), durability, and reliability. Once assembled as a strain sensor, the hydrogel is able to monitor both large and subtle human motions. Besides, this hydrogel exhibited desirable biocompatibility, as demonstrated by in vitro cytotoxicity towards NIH 3T3 cells. These integrated properties make this nanocomposite hydrogel a promising candidate for future applications as green, flexible, and smart sensors.

Ginsenoside Rg5 nanomedicine composited hydrogel with metabolic regulation and immunomodulation properties for tunneling diabetic wounds therapy

Diabetic wounds behaved delayed healing mainly due to impaired metabolism, dysregulated inflammation, and unique tunneling morphology. Herein, a customized nanocomposite hydrogel for diabetic wounds therapy was designed, demonstrating injectability, shape-adaptivity, and mechanical durability that adapt to the tunneling wound morphology. The hydrogel performed controlled drug release for metabolic regulation and immunomodulatory under topical administration. This hydrogel consists of oxidized anredera cordifolia polysaccharide (OACS), adipic dihydrazide grafted collagen fiber (CF-ADH), and ginsenoside Rg5 loaded polyethyleneimine grafted F127 nanoparticles (F127-PEI@Rg5 NPs). Triple dynamic bonds contributed to the fast cross-linking reconstitution during shape-remodeling, including the acylhydrazone and amine bonds formed from CF-ADH and F127-PEI@Rg5 NPs with OACS, and the electrostatic interactions between the inherent carboxyl groups and protonated amino groups in the materials. The nanolization and two-step loading of Rg5 leaded to improved bioavailability and prolonged drug action time. As a result, this hydrogel exhibited expected regulation for key enzymes in glycolysis, and relieved insulin resistance, thus providing an adequate energy supply for tissue remolding. Additionally, it increased macrophages number and promoted macrophages polarization, thus breaking the prolonged inflammation of diabetic wounds. In vivo experiments showed that the healing period was shortened by 34%, suggesting a promising dressing for diabetic wounds.

3D printed heart valve mediated nitric oxide sustained release reduced potential for calcification and inflammatory capacity

Heart valve replacement have numerous problems, such as calcification, inflammation, and limited endothelialization. Herein, we used bio-degradable arginine-modified polylysine and oxidized hyaluronic acid as the substrate, expanding the advantages of rapid Schiff-base reaction of aldehydes and amino groups under physiological conditions to form dynamic acyl-hydrazone bonds. These were used to design dynamic adaptive hydrogels, and a polysaccharide/protein dual-network system that mimicked the extracellular matrix, realizing the excellent mechanical tunability and shear thinning properties of its hydrogel. The dual antibacterial mechanism effectively avoided the occurrence of infection-like inflammation after valve implantation. The hydrogel has great ability in promoting cellular proliferation, and can also promote cell migration through a potential cell recruitment mechanism. The hydrogel dynamically triggers and sustains NO release in vivo, removing highly expressed ROS in inflammatory site as needed. It further promotes angiogenesis, and provides targeted treatment for calcified aortic valve disease caused by oxidative stress signals. Furthermore, it exhibits exceptional anti-calcification properties and can enhance the upregulation of CD31 while suppressing the expression of IL-10 and TNF-α, thereby significantly promoting angiogenesis and reducing inflammation. Additionally, 3D printing technology enables the individualized customization of valves with diverse heterogeneous structures to achieve a high degree of biomimetic tissue.

Covalent Adaptable Polymethacrylate Networks by Hydrazide Crosslinking Via Isosorbide Levulinate Side Groups.

Reversible crosslinking offers an attractive strategy to modify and improve the properties of polymer materials while concurrently enabling a pathway for chemical recycling. This can, for example, be achieved by incorporating a ketone functionality into the polymer structure to enable post-polymerization crosslinking with dihydrazides. The resulting covalent adaptable network contains acylhydrazone bonds cleavable under acidic conditions, thereby providing reversibility. In the present work, we regioselectively prepare a novel isosorbide monomethacrylate with a pendant levulinoyl group via a two-step biocatalytic synthesis. Subsequently, a series of copolymers with different contents of the levulinic isosorbide monomer and methyl methacrylate are prepared by radical polymerization. Using dihydrazides, these linear copolymers are then crosslinked via reaction with the ketone groups in the levulinic side chains. Compared to the linear prepolymers, the crosslinked networks exhibit enhanced glass transition temperatures and thermal stability, up to 170 and 286 °C, respectively. Moreover, the dynamic covalent acylhydrazone bonds are efficiently and selectively cleaved under acidic conditions to retrieve the linear polymethacrylates. We next show that recovered polymers can again be crosslinked with adipic dihydrazide, thus demonstrating the circularity of the materials. Consequently, we envision that these novel levulinic isosorbide-based dynamic polymethacrylate networks have great potential in the field of recyclable and reusable biobased thermoset polymers.

High-Performance Multi-Dynamic Bond Cross-Linked Hydrogel with Spatiotemporal siRNA Delivery for Gene-Cell Combination Therapy of Intervertebral Disc Degeneration.

Chronic inflammatory diseases, such as intervertebral disc degeneration (IVDD), which affect the lives of hundreds of millions of people, still lack effective and precise treatments. In this study, a novel hydrogel system with many extraordinary properties is developed for gene-cell combination therapy of IVDD. Phenylboronic acid-modified G5 PAMAM (G5-PBA) is first synthesized, and therapeutic siRNA silencing the expression of P65 mixed with G5-PBA (siRNA@G5-PBA) is then embedded into the hydrogel (siRNA@G5-PBA@Gel) based on multi-dynamic bonds including acyl hydrazone bonds, imine linkage, π-π stacking, and hydrogen bonding interactions. Local and acidic inflammatory microenvironment-responsive gene-drug release can achieve spatiotemporal regulation of gene expression. In addition, gene-drug release from the hydrogel can be sustained for more than 28 days in vitro and in vivo, greatly inhibiting the secretion of inflammatory factors and the subsequent degeneration of nucleus pulposus (NP) cells induced by lipopolysaccharide (LPS). Through prolonged inhibition of the P65/NLRP3 signaling pathway, the siRNA@G5-PBA@Gel is verified to relieve inflammatory storms, which can significantly enhance the regeneration of IVD when combined with cell therapy. Overall, this study proposes an innovative system for gene-cell combination therapy and a precise and minimally invasive treatment method for IVD regeneration.

Engineered Injectable Cell-Laden Chitin/Chitosan Hydrogel with Adhesion and Biodegradability for Calvarial Defect Regeneration.

Trade-off of high-strength and dynamic crosslinking of hydrogels remains an enormous challenge. Motivated by the self-healing property of biological tissues, the strategy of combining multiple dynamic bond mechanisms and a polysaccharide network is proposed to fabricate biomimetic hydrogels with sufficient mechanical strength, injectability, biodegradability, and self-healing property for bone reconstruction engineering. Stable acylhydrazone bonds endowed hydrogels with robust mechanical strength (>10 kPa). The integration of dynamic imine bonds and acylhydrazone bonds optimized the reversible characteristic to protect the cell during the injection and mimicked ECM microenvironment for cell differentiation as well as rapid adapting bone defect area. Furthermore, due to the slow enzymatic hydrolysis kinetics of chitosan and the self-healing properties of resulting networks, hydrogels exhibited a satisfactory biodegradation period (>8 weeks) that highly matches with bone regeneration. Additionally, rBMSC-laden hydrogels exhibited splendid osteogenic induction and bone reconstruction without prefabrication scaffolds and incubation, demonstrating tremendous potential for clinical application. This work proposes an efficient strategy for the construction of a low-cost multifunctional hydrogel, making polysaccharide-based hydrogels as the optimal carrier for enabling cellular functions in bone repair.

Salvianolic-Acid-B-Loaded HA Self-Healing Hydrogel Promotes Diabetic Wound Healing through Promotion of Anti-Inflammation and Angiogenesis.

Inflammatory dysfunction and angiogenesis inhibition are two main factors leading to the delayed healing of diabetic wounds. Hydrogels with anti-inflammatory and angiogenesis-promoting effects have been considered as promising wound care materials. Herein, a salvianolic acid B (SAB)-loaded hyaluronic acid (HA) self-healing hydrogel (HA/SAB) with anti-inflammatory and pro-angiogenesis capacities for diabetic wound healing is reported. The HA hydrogel was prepared via the covalent cross-linking of aldehyde groups in oxidized HA (OHA) and hydrazide groups in adipic dihydrazide (ADH)-modified HA (HA-ADH) with the formation of reversible acylhydrazone bonds. The obtained HA hydrogel exhibited multiple favorable properties such as porous structures, excellent self-healing properties, a sustainable release capacity of SAB, as well as excellent cytocompatibility. In addition, the effects of the SAB-loaded HA self-healing hydrogel were investigated via a full-thickness skin defect model using diabetic rats. The HA/SAB hydrogel showed enhanced skin regeneration effects with accelerated wound closure, shorter remaining dermal space length, thicker granulation tissue formation, and more collagen deposition. Furthermore, reduced inflammatory response and enhanced vascularization were found with HA/SAB2.5 hydrogel-treated wounds, indicating that the hydrogel promotes diabetic wound healing through the promotion of anti-inflammation and angiogenesis. Our results suggest that the fabricated SAB-loaded HA self-healing hydrogel is promising as a wound dressing for the treatment of diabetic wounds.

Tough, Photoluminescent, Self-Healing Waterborne Polyurethane Elastomers Resulting from Synergistic Action of Multiple Dynamic Bonds

Polymers that integrate multiple functions into one system broaden the application range of materials, but it remains a great challenge to obtain polymer materials with simultaneously high strength, high toughness, and high self-healing rate. In this work, we prepared waterborne polyurethane (WPU) elastomers using Schiff bases containing disulfide and acylhydrazone bonds (PD) as chain extenders. Acylhydrazone forming a hydrogen bond not only acts as a physical cross-linking point, which promotes the microphase separation of polyurethane to increase the thermal stability, tensile strength, and toughness of the elastomer, but also serves as a "clip" to integrate various dynamic bonds together to synergistically reduce the activation energy of the polymer chain movement and endow the molecular chain with faster fluidity. Therefore, WPU-PD exhibits excellent mechanical properties at room temperature, such as a tensile strength and a fracture energy of 25.91 MPa and 121.66 kJ m-2, respectively, and a high self-healing efficiency of 93.7% in a short time under moderate heating conditions. In addition, the photoluminescence property of WPU-PD enables us to track its self-healing process by monitoring change of the fluorescence intensity at the cracks, which helps to avoid the accumulation of cracks and improve the reliability of the elastomer. This self-healing polyurethane has a great potential application value in optical anticounterfeiting, flexible electronics devices, functional automobile protective films, and so on.

Conductive and self-healing hydrogel for flexible electrochemiluminescence sensor.

Aflexible electrochemiluminescence (ECL)hydrogel sensor exhibiting good self-healing was constructed. A transparent self-healing oxidized sodium alginate/hydrazide polyethylene glycol (OSA/PEG-DH) hydrogel was prepared by crosslinking dynamic covalent acylhydrazone bond. The introduction of 4-amino-DL-phenylalanine, a catalyst with good biocompatibility, allows rapid gelation and self-healing of hydrogel under mild conditions. Using the hydrogel as the sensing substrate, the ionic liquid (IL) 2-hydroxy-N,N,N-trimethylethanaminium chloride and the luminescent reagent N-(aminobutyl)-N-(ethylisoluminol) (ABEI) were simultaneously immobilized in the OSA/PEG-DH hydrogel to obtain the ABEI/IL/OSA/PEG-DH hydrogel. The ABEI/IL/OSA/PEG-DH hydrogel can be directly used as a semi-solid electrolyte for constructing a flexible ECL hydrogel sensor for the detection of H2O2, which acted as a coreactant of ABEI. The prepared flexible ECL sensor showed good self-healing performance, can restore ECL signal intensity within 20min after physical damage, and showed high accuracy in the analysis of complex serum samples. This research shed new light on the development of flexible ECL sensor for bioanalytical applications.