Dynamically Cross-Linked Double-Network Hydrogels with Matched Mechanical Properties and Ideal Biocompatibility for Artificial Blood Vessels.

Vessel transplantation is currently considered the "gold standard" treatment for cardiovascular disease. However, ideal artificial vascular grafts should possess good biocompatibility and mechanical strength that match those of native autologous vascular tissue to promote in vivo tissue regeneration. In this study, a series of dynamic cross-linking double-network hydrogels and the resultant hydrogel tubes were prepared. The hydrogels (named PCO), composed of rigid poly(vinyl alcohol) (PVA), flexible carboxymethyl chitosan (CMCS), and a cross-linker of aldehyde-based ß-cyclodextrin (OCD), were formed in a double-network structure with multiple dynamical cross-linking including dynamic imine bonds, hydrogen bonds, and microcrystalline regions. The PCO hydrogels exhibited superior mechanical strength, good network stability, and fatigue resistance. Additionally, it demonstrated excellent cell and blood compatibility. The results showed that the introduction of CMCS/OCD led to a significant increase in the proliferation rate of endothelial cells seeded on the surface of the hydrogel. The hemolysis rate in the test was lower than 0.3%, and both protein adsorption and platelet adhesion were reduced, indicating an excellent anticoagulant function. The plasma recalcification time test results showed that endogenous coagulation was alleviated to some extent. When formed into blood vessels and incubated with blood, no thrombus formation was observed, and there was minimal red blood cell aggregation. Therefore, this novel hydrogel tube, with excellent mechanical properties, exhibits antiadhesive characteristics toward blood cells and proteins, as well as antithrombotic properties, making it hold tremendous potential for applications in the biomedical and engineering fields.

Preparation and Characterization of Chloroprene Latexes Modified with Vinyl-POSS.

Water-based chloroprene latex is a solvent-free, environmentally friendly adhesive. Currently, its market demand is growing rapidly. However, there are problems such as a lack of heat resistance and poor mechanical properties, which limit its application. The introduction of vinyl-POSS (OVS) into the resin structure can effectively improve the thermal stability of chloroprene adhesives. In this paper, modified waterborne chloroprene latex was prepared by copolymerization of methyl methacrylate and OVS with chloroprene latex. The results showed that vinyl-POSS was successfully grafted onto the main chain of the waterborne chloroprene latex, and the modified waterborne chloroprene latex had good storage stability. With the increase in vinyl-POSS, the tensile strength of the chloroprene latex firstly increased and then decreased, the tensile property (peel strength of 20.2 kgf) was maintained well at a high temperature (100 °C), and the thermal stability of the chloroprene latex was improved. When the addition amount was 4%, the comprehensive mechanical properties were their best. This study provides a new idea for the construction of a new and efficient waterborne chloroprene latex system and provides more fields for the practical application of waterborne chloroprene latex. This newly developed vinyl-POSS modified chloroprene latex has great application potential for use in home furniture, bags, and seat cushions.

Host-Guest Assembly-Crosslinked Nanoemulsions with Dual-Antimicrobial Mechanism for Treating Multidrug-Resistant Bacterial Biofilms.

Plant essential oils have good antimicrobial properties, but their poor stability and compatibility in aqueous solutions greatly limit their practical application. To address this issue, a dynamically crosslinked nanoemulsion based on host-guest assembly was developed in this study. First, a ß-cyclodextrin-functionalized quaternary ammonium surfactant (ß-CD-QA) and adamantane-terminated polyethylene glycol (APA) crosslinker were first synthesized. Then, the oil-in-water host-guest crosslinked nanoemulsions (HGCTNs) were formed by incorporating tea tree essential oils (TTO) as a natural antimicrobial agent. The results showed that HGCTNs significantly improved the stability of the essential oil nanoemulsions and extended their shelf life. Furthermore, HGCTNs demonstrated effective antimicrobial properties against both Gram-negative/positive bacterioplankton and bacterial biofilms. The results of antibacterial experiments showed that the dynamically crosslinked HGCTNs exhibit superior antibacterial efficacy, with a minimum inhibitory concentration (MIC) of 12.5 v/v % (0.13 µL/mL TTO) and could eradicate the biofilms. The electrical conductivity of the bacterial solution gradually increased within 5 h of treatment with the nanoemulsions, indicating that the HGCTNs have a slow-release effect of TTO and sustainable antibacterial ability. The antimicrobial mechanism can be attributed to the synergistic antibacterial action of the ß-CD-QA surfactant containing a quaternary ammonium moiety and TTO, which are stabilized by nanoemulsions.

Highly Elastic, Self-Healing, Recyclable Interlocking Double-Network Liquid-Free Ionic Conductive Elastomers via Facile Fabrication for Wearable Strain Sensors.

Liquid-free ionic conductive elastomers (ICEs) are ideal materials for wearable strain sensors in increasingly flexible electronic devices. However, developing recyclable ICEs with high elasticity, self-healability, and recyclability is still a great challenge. In this study, we fabricated a series of novel ICEs by in situ polymerization of lipoic acid (LA) in poly(acrylic acid) (PAA) solution and cross-linking by coordination bonding and hydrogen bonding. One of the obtained dynamically cross-linked interlocking double-network ICEs, PLA-PAA4-1% ICE, showed excellent mechanical properties, with high elasticity (90%) and stretchability (610%), as well as rapid self-healability (mechanical self-healing within 2 h and electrical recovery within 0.3 s). The PLA-PAA4-1% ICE was used as a strain sensor and possessed excellent linear sensitivity and highly cyclic stability, effectively monitoring diverse human motions with both stretched and compressed deformations. Notably, the PLA-PAA4-1% ICE can be fully recycled and reused as a new strain sensor without any structure change or degradation in performance. This work provided a viable path to fabricate conductive materials by solving the two contradictions of high mechanical property and self-healability, and structure stability and recyclability. We believe that the superior overall performance and feasible fabrication make the developed PLA-PAA4-1% ICE hold great promise as a multifunctional strain sensor for practical applications in flexible wearable electronic devices and humanoid robotics.

Regioselective conjugate addition of isoxazol-5-ones to ethenesulfonyl fluoride.

The highly regioselective conjugate addition of isoxazol-5-ones to ethenesulfonyl fluoride (ESF) has been developed. In the presence of different bases, N2-alkylated and C4-alkylated isoxazol-5-ones with a sulfonyl fluoride group were obtained separately with good to excellent yields. Further transformations with amines and phenol gave sulfonamides and sulfonates. The intriguing combination of isoxazol-5-ones and the sulfonyl fluoride group produces valuable products for drug discovery.

Injectable thermo-sensitive and wide-crack self-healing hydrogel loaded with antibacterial anti-inflammatory dipotassium glycyrrhizate for full-thickness skin wound repair.

Severe skin injuries are hard to repair and susceptible to bacterial infection. Development of a versatile antimicrobial anti-inflammatory hydrogel dressing that eliminates concern over antibiotic resistance is urgently needed but remains an elusive goal. Our research, described herein, the design and fabrication of a new family of supramolecular hydrogels based on hydroxypropyl chitosan (HPCS) and poly(N-isopropylacrylamide) (PNIPAM) may prove to be that goal. Employing the reversible cross-linking by ß-cyclodextrin (ß-CD) and adamantyl (AD) pre-assembly, the hydrogels can be formed in a facile one-pot method. Additionally, the structure and performance of the hydrogels can be controlled by a simple adjustment of the AD content. The obtained hydrogels exhibit an abundance of desired properties; they are injectable, thermosensitive, highly ductile, self-healable (will self-heal recurring damage to the hydrogel bandage of up to several millimeters wide), biocompatible, and have antimicrobial activity against Staphylococcus aureus when infused with dipotassium glycyrrhizinate (DG). Using a mouse full-thickness skin defect model, in vivo wound healing evaluations revealed that the DG-loaded hydrogels (HP-3/DG10) applied to the wound resulted in rapid wound closure. The hydrogels promoted efficient tissue remolding, collagen deposition, decreased inflammation and performed better than the control groups of commercial TegadermTM film and 3M dressing. Given their multifunctionality and in vivo efficacy, the DG-loaded HP hydrogels hold great potential as a wound dressing for full-thickness skin repair. STATEMENT OF SIGNIFICANCE: Injectable hydrogels are receiving increasing attention as an ideal wound dressing. To the best of our knowledge, however, injectable and wide-crack self-healing hydrogel dressings have been hardly studied. A versatile antimicrobial hydrogel without drug resistance or cytotoxicity is also highly required. Therefore, in the present study, we constructed injectable thermosensitive and wide-crack self-healing hydrogels with antibacterial and anti-inflammatory properties. These hydrogels were developed through novel strategies of the wide-crack self-healing design and the loading of the bioactive antibacterial and anti-inflammatory agent dipotassium glycyrrhizinate. The simple preparation method and multifunctionality of the studied hydrogel composites may provide important insights for the development of future biomaterials for wound dressings and other biomedical applications.

Enantioselective Addition of Azlactones to Ethylene Sulfonyl Fluoride via Dual Catalysis.

Enantioselective conjugate addition of azlactones to ethylene sulfonyl fluoride has been achieved via the cooperative catalysis with (DHQD)2PHAL and a hydrogen-bond donor (HBD). This approach furnishes a facile access to a range of structurally diverse azlactone sulfonyl fluoride derivatives with good to excellent yields and enantioselectivities. The combination of azlactone and sulfonyl fluoride group produces valuable unnatural α-quaternary amino acid derivatives for the drug discovery.

Highly Enantioselective Addition of N-2,2,2-Trifluoroethylisatin Ketimines to Ethylene Sulfonyl Fluoride.

An enantioselective Michael addition between N-2,2,2-trifluoroethylisatin ketimines and ethylene sulfonyl fluoride has been disclosed. This method provides a facile strategy to access a range of structurally diverse isatin-derived α-(trifluoromethyl)imine derivatives with excellent yields and enantioselectivities. The intriguing combination of α-(trifluoromethyl)amine and sulfonyl fluoride groups leads to the valuable candidates for the drug discovery.

Repeatedly Intrinsic Self-Healing of Millimeter-Scale Wounds in Polymer through Rapid Volume Expansion Aided Host-Guest Interaction.

Implantable and wearable materials, which are usually used in/on a biological body, are mostly needed with biomimetic self-healing function. To enable repeatable large-wound self-healing and volume/structure recovery, we verified a proof-of-concept approach in this work. We design a polymer hydrogel that combines temperature responsiveness with an intrinsic self-healing ability through host-guest orthogonal self-assembly between two types of poly(N-isopropylacrylamide) (PNIPAM) oligomers. The result is thermosensitive, capable of fast self-repair of microcracks based on reversible host-guest assembly. More importantly, when a large open wound appears, the hydrogel can first close the wound via volume swelling and then completely self-repair the damage in terms of intrinsic self-healing. Meanwhile, its original volume can be easily recovered by subsequent contraction. As demonstrated by the experimental data, such millimeter-level wound self-healing and volume recovery can be repeatedly carried out in response to the short-term cooling stimulus. With low cytotoxicity and good biocompatibility, moreover, this highly intelligent hydrogel is greatly promising for practical large-wound self-healing in wound dressing, electronic skins, wearable biosensors, and humanoid robotics, which can tolerate large-scale human motions.

Dynamically crosslinked polymer nanocomposites to treat multidrug-resistant bacterial biofilms.

Multidrug-resistant biofilms are highly resistant to current antimicrobial therapies. We have developed an antimicrobial platform that integrates the bacteria-killing phytochemical carvacrol into dynamically crosslinked polymer nanocomposites (DCPNs). Taking advantage of a reversibly crosslinked Schiff-base scaffold throughout the engineered emulsions, DCPNs exhibited long-term shelf-life and good stability in serum, while readily disassembling in acidic microenvironments. Furthermore, we demonstrated that DCPNs efficiently penetrate the biofilm matrix, eradicating both Gram-negative/positive bacteria enclosed within. Moreover, DCPNs showed no observable toxicity to fibroblast mammalian cells with the same antimicrobial concentrations necessary to eradicate MDR biofilms. Given their potent antimicrobial and stimuli-responsive dissociation characteristics in a biofilm setting, DCPNs are a suitable therapeutic platform for combating MDR bacterial infections.

Tough and durable hydrogels with robust skin layers formed via soaking treatment.

Recent progress has seen significant advances in the mechanical performances of synthetic hydrogels. However, the mechanics of hydrogels usually suffer drastic degradation under repetitive mechanical and complicated environmental loadings. Here, we fabricate a class of biocompatible layered poly(vinyl alcohol) hydrogels by simply soaking a preformed poly(vinyl alcohol) gel in sodium silicate. The resulting hydrogels exhibit a combination of superior mechanical performances and good biocompatibility, along with exceptional chemical robustness. The layered structure is composed of a compact cover layer and a porous center layer. Both layers are composed of poly(vinyl alcohol). The network in the cover is crosslinked by ordered polarized H-bonds with swelling stability, while the porous center confines a large volume of interstitial water. The structural and crosslinking metric confers the hydrogels with capabilities to tolerate complicated mechanical and environmental loads. The optimized gel is tough (fracture energy >10 kJ m-2) and strong (fracture stress ≈ 5 MPa). The strengthening mechanism can be correlated to the layered structure, which causes the impeded flow of interstitial water. Their mechanical performance is maintained in strong acidic/alkaline, and concentrated electrolytes, and in the presence of salting-in and H-bond-breaking reagents even at elevated temperatures. We speculate that the dipole-dipole pairings of Oδ--Hδ+ Oδ--Hδ+ in the cover layer probably generate hydrophobic microdomains. This swelling-resistant interaction may protect the hydrogels from swelling in complex aqueous envrionments. We also discuss the possible mechanism of the formation of layered structures and their crosslinkings.