Chondroitin sulfate hydrogels based on electrostatic interactions with enhanced adhesive properties: exploring the bulk and interfacial contributions.

Adhesive polysaccharide gels have highlighted their potential in biomedicine, tissue engineering, and wearable/implantable devices due to their tissue adhesive nature and excellent biocompatibility. However, the weak adhesive strength caused by the unclear relationship between the structure and the adhesive properties seriously hinders their further practical application. Here, a facile one-step synthesis method for adhesive and self-healing hydrogels with chondroitin sulfate (CS) and poly (methyl chloride quarternized N,N-dimethylamino ethylacrylate) (PDMAEA-Q) by ultraviolet light irradiation has been presented. We investigate the mechanism of the adhesion enhancement including improving the mechanical strength of gels (cohesion) and gel/substrate interfacial interactions (interfacial adhesion) by tailoring the compliance and cohesive energy density of the gel. The resultant soft and viscoelastic hydrogels displayed favorable adhesion ability on various substrates, and the adhesive strength to the iron substrate and porcine skin can reach 49.4 kPa and 15.4 kPa, respectively. Additionally, the gels also exhibited rapid self-healing properties and good cytocompatibility. We believe that the adhesive PDMAEA-Q/CS gel would be an ideal candidate for hydrogel glues for human-machine interfaces and biological tissues, and this design idea can open a new path for the preparation of adhesive polysaccharide hydrogels.

An extracellular matrix-inspired self-healing composite hydrogel for enhanced platelet-rich plasma-mediated chronic diabetic wound treatment.

Diabetes is generally accompanied by difficult-to-heal wounds, which often lead to permanent disability and even death of patients. Because of the abundance of a variety of growth factors, platelet rich plasma (PRP) has been proven to have great clinical potential for diabetic wound treatment. However, how to suppress the explosive release of its active components while realizing adaptability to different wounds remains important for PRP therapy. Here, an injectable, self-healing, and non-specific tissue-adhesive hydrogel formed by oxidized chondroitin sulfate and carboxymethyl chitosan was designed as an encapsulation and delivery platform for PRP. With a dynamic cross-linking structural design, the hydrogel can meet the clinical demands of irregular wounds with controllable gelation and viscoelasticity. Inhibition of PRP enzymolysis as well as sustained release of its growth factors is realized with the hydrogel, enhancing cell proliferation and migration in vitro. Notably, greatly accelerated healing of full thickness wounds of diabetic skins is enabled by promoting the formation of granulation tissues, collagen deposition and angiogenesis as well as reducing inflammation in vivo. This self-healing and extracellular matrix-mimicking hydrogel provides powerful assistance to PRP therapy, enabling its promising applications for the repair and regeneration of diabetic wounds.

Polysaccharide/Ti3C2Tx MXene adhesive hydrogels with self-healing ability for multifunctional and sensitive sensors.

Integrating functionalities such as adhesiveness, self-healing, and conductivity on a polysaccharide-based hydrogel is highly desirable for ever-expanding practical applications, but there is always a challenge. Herein, an elaborately designed nanocomposite hydrogel is fabricated by the addition of highly conductive Ti3C2Tx MXene nanosheets into chondroitin sulfate (CS)/N, N-dimethylamino ethyl acrylate (DMAEA-Q) hydrogel network. Owing to the introduction of sulfonated Ti3C2Tx MXene nanosheets, the as-prepared nanocomposite hydrogels exhibit excellent stretchability (> 5000% strain), rapid self-healing ability (< 60 s), and high adhesiveness (≈ 100 kPa). The proposed hydrogel demonstrates an outstanding electrical conductivity up to 5.33 S/m, allowing real-time monitoring of the bending and stretching movements and full recovery. Furthermore, the SMC hydrogels exhibit fast and stable photothermal conversion performance due to the inherent photothermal behavior. Notably, multifunctional SMC hydrogels present real-time and reversible humidity sensing upon H2O-induced swelling/contraction of nanochannels between the Ti3C2Tx MXene interlayers, enabling respiration monitoring applications.

A Surface Diffusion Barrier Strategy toward Water-Resistant Photonic Materials for Accurate Detection of Ethanol.

Photonic materials that enable visual detection of chemicals have shown great potential for wide applications in chemical, environmental, biotechnological, and food industries, but until now, using hydrophilic photonic materials for tracing water-soluble chemicals remains a major challenge due to the strong water interference. Here, we demonstrate a two-step co-assembly and subsequent surface coating strategy to develop an ethanol-sensitive and anti-water interference photonic crystal film. By using citric acid as a co-assembly phase, high ethanol sensing is realized because of the strong intermolecular affinity. By controlling the thickness of the outer polyvinyl butyral layer, selective ethanol penetration but a water barrier is enabled. Notably, the composite photonic films are free-standing, highly flexible, and controllably structurally colored. We further present using the composite film to quantitatively trace ethanol/water mixtures and potentially track drunk driving as a colorimetric sensor. The heuristic two-step modification strategy proposed in this work not only overcomes the limitation of water interference for hydrophilic colorimetric sensors but also provides references to develop more new photonic materials with water resistance that need to be applied in water/humid environments.

Highly Flame-Retardant and Low Heat/Smoke-Release Wood Materials: Fabrication and Properties.

Wood is an important renewable material exhibiting excellent physical and mechanical properties, environmental friendliness, and sustainability, and has been widely applied in daily life. However, its inherent flammability and susceptibility to fungal attack greatly limit its application in many areas. Use of fire-retardant coatings and preservatives has endowed wood with improved safety performance; importantly, the cooperative effect of dual treatments on the burning behavior and flame retardancy of wood needs to be better understood. Here, a two-step treatment for wood is proposed, with a copper-boron preservative (CBP) and a fire-retardant coating. The thermal degradation and burning behavior of treated wood were investigated. The CBP formed a physical barrier on the wood surface, facilitating a charring process at high temperatures and thus suppressing the release of heat and smoke. Notably, the dual-treated wood exhibited lower heat release and reduced smoke emission compared with the mono-treated wood, indicating a cooperative effect between CBP and fire-retardant coatings, beneficial to the improvement of fire safety. This experimental work improved fire retardance and suppressed smoke release in flammable materials, and offers a new design for developing fire-retardant coatings.