Engineering Self-Adaptive Multi-Response Thermochromic Hydrogel for Energy-Saving Smart Windows and Wearable Temperature-Sensing.

Buildings account for ≈40% of the total energy consumption. In addition, it is challenging to control the indoor temperature in extreme weather. Therefore, energy-saving smart windows with light regulation have gained increasing attention. However, most emerging base materials for smart windows have disadvantages, including low transparency at low temperatures, ultra-high phase transition temperature, and scarce applications. Herein, a self-adaptive multi-response thermochromic hydrogel (PHC-Gel) with dual temperature and pH response is engineered through "one-pot" integration tactics. The PHC-Gel exhibits excellent mechanical, adhesion, and electrical conductivity properties. Notably, the low critical solubility temperature (LCST) of PHC-Gel can be regulated over a wide temperature range (20-35 °C). The outdoor practical testing reveals that PHC-Gel has excellent light transmittance at low temperatures and radiation cooling performances at high temperatures, indicating that PHC-Gel can be used for developing energy-saving windows. Actually, PHC-Gel-based thermochromic windows show remarkable visible light transparency (Tlum ≈ 95.2%) and solar modulation (△Tsol ≈ 57.2%). Interestingly, PHC-Gel has superior electrical conductivity, suggesting that PHC-Gel can be utilized to fabricate wearable signal-response and temperature sensors. In summary, PHC-Gel has broad application prospects in energy-saving smart windows, smart wearable sensors, temperature monitors, infant temperature detection, and thermal management.

Facile "Synergistic Inner-Outer Activation" Strategy for Nano-Engineering of Nature-Skin-Derived Wearable Daytime Radiation Cooling Materials.

Natural skin-derived products, as traditional wearable materials are widely used in people's daily life due to the products' excellent origins. Herein, a versatile daytime-radiation cooling wearable natural skin (RC-skin) consisting of the collagen micro-nano fibers with the on-demand double-layer radiation cooling structure is nano-engineered through the proposed facile "synergistic inner-outer activation" strategy. The bottom layer (inner strategy) of the RC-skin is fabricated by filling the skin with the Mg11 (HPO3 )8 (OH)6 nanoparticles by soaking. The superstratum (outer strategy) is constituted by a composite coating with an irregular microporous structure. The RC-skin harvests the inherent advantages of natural building blocks including sufficient hydrophobicity, excellent mechanical properties, and friction resistance. Owing to the subtle double-layer structure design, the solar reflectance and the average emissivity in the mid-infrared band of RC-skin are ≈92.7% and ≈95%, respectively. Therefore, the RC-skin's temperature in the sub-ambient is reduced by ≈7.5 °C. Various outdoor practical application experiments further substantiate that RC-skin has superior radiation cooling performances. Collectively, RC-skin has broad-application prospects for intelligent wearing, low-carbon travel, building materials, and intelligent thermoelectric power generation, and this study also provides novel strategies for developing natural-skin-derived functional materials.

Thermoresponsive Hemostatic Hydrogel with a Biomimetic Nanostructure Constructed from Aggregated Collagen Nanofibers.

Uncontrollable bleeding poses considerable fatality risks by large-volume blood losses. Current emergency antibleeding handlings including either compression with gauze or "passive" blood transfusion are thus far from ideal, while most recently developed hemostatic agents still share common limitations without considering the subsequent tissue repairing and antibacterial activity after treatment. Herein, we introduce a novel bioinspired aggregated collagen nanofiber-based biocompatible and efficient hemostatic hydrogel material (TS-Gel-Ag-col) prepared by the integration of multifunctional compounds of muco-mimetic poloxamer, polyvinylpyrrolidone, and dencichine/chitosan dialdehyde synergistic crosslinked aggregated collagen nanofibers decorated with silver nanoparticles. Comprehensive material characterization and in vitro and in vivo studies of TS-Gel-Ag-col demonstrate that these materials possess effective antihemorrhagic and antibacterial wound protection effects. Moreover, TS-Gel-Ag-col can facilitate the tissue repairing of skin wounds by promoting revascularization. TS-Gel-Ag-col holds great promise for next-generation collagen-based absorbable hemostatic materials and for the development of smart artificial skins.

A Review of Recent Progress on Collagen-Based Biomaterials.

Since the 2010s, the demand for healthcare models has exceeded the prevailing resources available due to the rapid increase in the aging population in China. However, a significant gap in development of biomedical materials remains, especially between China and the western developed countries. Collagen is the major protein of the extracellular matrix (ECM) and has been extensively applied in medical fields. Collagen-based biomaterials (CBBs) are used to prepare dressings and dermal substitutes, surgical sutures, plasma substitutes, tissue-engineered scaffolds, and drug delivery systems; this is attributed to their exceptional biocompatibility, biodegradability, hypoimmunogenicity, and coordination between collagen hosts and tissues. This review provides thorough strides in CBB structures, crosslinking and forming technologies, and real-world applications. First, the natural origin and specific structures of animal-derived collagen and non-animal-derived collagen are introduced and compared. Second, crosslinking methods and forming technologies of CBBs across the board are discussed. Third, several examples are considered to demonstrate the practical biomedical use of CBBs and highlight cautionary notes. Finally, the underlying development directions of CBBs from an interdisciplinary perspective are outlined. This review aims to provide comprehensive mechanisms by which collagen can be uniquely and practically used as advanced biomaterial, hence providing options for augmenting its development in China.

Nature-Skin-Derived e-Skin as Versatile "Wound Therapy-Health Monitoring" Bioelectronic Skin-Scaffolds: Skin to Bio-e-Skin.

Electronic skins (e-skins) have the potential to turn into breakthroughs in biomedical applications. Herein, a novel acellular dermal matrix (ADM)-based bioelectronic skin (e-ADM) is used to fabricate versatile "wound therapy-health monitoring" tissue-nanoengineered skin scaffolds via a facile "one-pot" bio-compositing strategy to incorporate the conductive carbon nanotubes and self-assembled micro-copper oxide microspheres with a cicada-wing-like rough surface and nanocone microstructure. The e-ADM exhibits robust tensile strength (22 MPa), flexibility, biodegradability, electroactivity, and antibacterial properties. Interestingly, e-ADM exhibits the pH-responsive ability for intelligent command between sterilization and wound repair . Additionally, e-ADM enables accurate real-time monitoring of human activities, providing a novel flexible e-skin sensor to record injury and motions. In vitro and in vivo experiments show that with electrical stimulation, e-ADM could prominently facilitate cell growth and proliferation and further promote full-thickness skin wound healing, providing a comprehensive therapeutic strategy for smart sensing and tissue repair, guiding the development of high-performance "wound therapy-health monitoring" bioelectronic skin-scaffolds.

Development of a multifunctional injectable temperature-sensitive gelatin-based adhesive double-network hydrogel.

Gelatin-based bioadhesives are suitable for the treatment of wounds due to their inherent biocompatibility, lack of immunogenicity, and potential for modification. However, common limitations with such adhesives include their adhesive strength and versatility. In the present study, a multifunctional injectable temperature-sensitive gelatin-based adhesive double-network hydrogel (DNGel) was engineered using facile dual-syringe methodology. An integrative crosslinking strategy utilized the complexation of catechol-Fe3+ and NIPAAm-methacryloyl. As anticipated, the DNGel exhibited multifunctional therapeutic properties, namely temperature-sensitivity, mechanical flexibility, good adhesive strength, injectability, self-healing capability, antibacterial activity, and the capability to enable hemostasis and wound healing. The bioinspired dynamic double-network was stabilized by a number of molecular interactions between components in the DNGel, providing multifunctional therapeutic performance. In addition, comprehensive in vitro and in vivo testing confirmed that the adhesive hydrogel exhibited effective antihemorrhagic properties and accelerated wound healing by the promotion of revascularization, representing considerable potential as a next-generation multifunctional smart adhesive patch.

Fly-antennae-inspired biomass-based fluorescent platform for NH3 quantitative detection and visual real-time monitoring of seafood spoilage.

Traditional strategies for quantitative detection of NH3 and monitoring of seafood spoilage still have some pervasive issues of cumbersome operation, time-consuming, high-cost, and inefficient real-time monitoring, and visualization. Integration of biomass-based materials and aggregation-induced emission (AIE) fluorescence probes exhibit conceivable potential in seafood detection and environmental monitoring. Herein, a fly-antennae-inspired biomass-based solid-state fluorescent platform (PAA-FP) with effective, easy-to-use, reusable, low-cost and highly sensitive characteristics is nanoengineered for NH3 quantitative detection (detection limit = 0.5 ppm) and visual real-time monitoring of seafood spoilage using smartphones. The PAA-FP possesses an anticipative "fly-antennae-like" microstructure and offers selective recognition of NH3 by naked eyes in daylight with excellent solid-state fluorescence properties. Moreover, PAA-FP is simply reused at least 5 times after AcOH fumigation. Comprehensive application experiments substantiate that PAA-FP successfully achieves quantitative detection of NH3 and realizes the visual real-time daylight monitoring of food spoilage using a simple color recognizing smartphone software. The present study demonstrates an effective fabrication strategy to explore various multifunctional biomass-based materials for sensing hazardous and noxious substances.

Feasibility Study of Gelatin Preparation from the Bioinspired Collagen Aggregates by a "Two-step" Facile Degradation Method.

Gelatin is the putative research hotspot of natural products, but gelatin prepared by traditional alkali methods has seriously affected its applications due to the worryingly low molecular weight and poor gel strength. Herein, we took the lead to extract the distinct gelatin from a kind of bioinspired collagen aggregate (CA) by a two-step controlled degradation method. Structural analysis suggested that the CA better preserves the natural aggregated structure of nature collagen (typical D-periodic cross-striated pattern). Compared with the gelatin gelatinized by the conventional alkali method (G-Al) and commercial gelatin (CG), the gelatin (G-CA) from CA had a wide molecular weight distribution range, high transparency, high viscosity, and strong gel strength as expected. Meanwhile, the G-CA film exhibited better mechanical performance and thermostability than CG and G-Al films, and water vapor permeability was also higher in the G-CA film, whereas water solubility was higher in the CG and G-Al films. Thus, the G-CA film is more conducive to the use of food packaging or edible films, exhibiting more potential market application prospects. Notably, G-CA based on CA from waste hide offal provides a way to reuse leather waste resources and further realize green and clean production in leather industry.

Spider-Web and Ant-Tentacle Doubly Bio-Inspired Multifunctional Self-Powered Electronic Skin with Hierarchical Nanostructure.

For the practical applications of wearable electronic skin (e-skin), the multifunctional, self-powered, biodegradable, biocompatible, and breathable materials are needed to be assessed and tailored simultaneously. Integration of these features in flexible e-skin is highly desirable; however, it is challenging to construct an e-skin to meet the requirements of practical applications. Herein, a bio-inspired multifunctional e-skin with a multilayer nanostructure based on spider web and ant tentacle is constructed, which can collect biological energy through a triboelectric nanogenerator for the simultaneous detection of pressure, humidity, and temperature. Owing to the poly(vinyl alcohol)/poly(vinylidene fluoride) nanofibers spider web structure, internal bead-chain structure, and the collagen aggregate nanofibers based positive friction material, e-skin exhibits the highest pressure sensitivity (0.48 V kPa-1 ) and high detection range (0-135 kPa). Synchronously, the nanofibers imitating the antennae of ants provide e-skin with short response and recovery time (16 and 25 s, respectively) to a wide humidity range (25-85% RH). The e-skin is demonstrated to exhibit temperature coefficient of resistance (TCR = 0.0075 °C-1 ) in a range of the surrounding temperature (27-55 °C). Moreover, the natural collagen aggregate and the all-nanofibers structure ensure the biodegradability, biocompatibility, and breathability of the e-skin, showing great promise for practicability.

Skin-inspired gelatin-based flexible bio-electronic hydrogel for wound healing promotion and motion sensing.

Next generation tissue-engineered skin scaffolds promise to provide sensory restoration through electrical stimulation in addition to effectively rebuilding and repairing skin. The integration of real-time monitoring of the injury motion activities can fundamentally improve the therapeutic efficacy by providing detailed data to guide the clinical practice. Herein, a mechanically-flexible, electroactive, and self-healable hydrogels (MESGel) was engineered for the combinational function of electrically-stimulated accelerated wound healing and motion sensing. MESGel shows outstanding biocompatibility and multifunctional therapeutic properties including flexibility, self-healing characteristics, biodegradability, and bioelectroactivity. Moreover, MESGel shows its potential of being a novel flexible electronic skin sensor to record the injury motion activities. Comprehensive in vitro and in vivo experiments prove that MESGel can facilitate effective electrical stimulation, actively promoting proliferation in Chinese hamster lung epithelial cells and therefore can accelerate favorable epithelial biology during skin wound healing, demonstrating an effective therapeutic strategy for a full-thickness skin defect model and leading to new-type flexible bioelectronics.

Biofabrication and Characterization of Collagens with Different Hierarchical Architectures.

Herein, three categories of collagens with different hierarchical architectures, including collagen molecules (Col), collagen microfibrils (F-col), and collagen fiber bundles (Ag-col), were systematically biofabricated based on the biosynthesis pathway of natural collagen. Their macroscopic properties, that is, physicochemical and biological properties, and hierarchical structures were evaluated synthetically. The results showed that Col had a rigid rod-like fibrous triple helix structure, whereas F-col and Ag-col had the typical D-periodic cross-striated patterns with lengths of about 54 and 60 nm in the longitudinal direction, respectively. We further found that collagens with higher hierarchical structures had more superior thermal stability, mechanical properties, and biodegradability. Among all three collagens, Ag-col was the best: it had the highest bioactivity and hemostatic properties and could better promote cell adhesion, growth, and proliferation and better improve the secretion of growth factors. Overall, we have a reason to believe that collagens with a higher hierarchical structure can serve as a better alternative source of collagenous materials for further applications in biological industries.

Development of a novel bio-inspired "cotton-like" collagen aggregate/chitin based biomaterial with a biomimetic 3D microstructure for efficient hemostasis and tissue repair.

Hemostatic materials based on collagen and chitin are commonly assessed with regard to their topical absorbability and bioactivity. However, their clinical application faces challenges such as relatively long hemostatic and wound healing times, single function, as well as wound bleeding in patients with blood diseases. Herein, a novel bio-inspired "cotton-like" collagen aggregate/chitin based biomaterial for rapid hemostatic and tissue repair (V-3D-Ag-col) was fabricated by a specific gradient-removal solvent approach. Significantly, for the first time, an advanced collagen aggregate (Ag-col) composed of typical D-periodic cross-striated collagen fibrils and thick collagen fiber bundles was used instead of traditional collagen molecules (Col) to construct a hemostatic material. The target material showed a biomimetic 3D microstructure and "cotton-like" appearance, as expected, which were conducive to platelet adhesion and aggregation. The fabricated V-3D-Ag-col exhibited superior thermo-stability, hemostatic activity and biodegradability. More importantly, V-3D-Ag-col could significantly promote cell growth and proliferation. Further, V-3D-Ag-col could accelerate the wound healing process better than the same material based on conventional collagen (V-3D-Col). In consequence, V-3D-Ag-col has the potential to become a new generation of collagen-absorbable functional hemostatic materials. Furthermore, Ag-col can replace the currently available conventional collagen materials as raw materials for the new generation of collagen-based biomedical materials.

Feasibility Study of Tissue Transglutaminase for Self-Catalytic Cross-Linking of Self-Assembled Collagen Fibril Hydrogel and Its Promising Application in Wound Healing Promotion.

Collagen-based bio-hydrogels are undoubtedly a hot spot in the development of biological dressings for wound healing promotion. Herein, glutamine transaminase (TGase), a biological nontoxic cross-linker with high specific activity and reaction rate under mild conditions, was utilized for the self-catalytic cross-linking of the regenerated collagen (COL) fibril hydrogel fabricated through a molecular self-assembly method. The results showed that the natural triple helical conformation of COL remained completely integrated after self-catalytic cross-linking TGase, which was definitively the fundamental for maintaining its superior bioactivity. It was worth noting that TGase could promote the self-assembly process of COL building blocks into a higher order D-period cross-striated structure. Also, the reconstructed TGase cross-linked COL fibrils exhibited a higher degree of interfiber entanglements with more straight and longer fibrils. Meanwhile, the thermal stability of COL was significantly improved after introducing TGase. Besides, the cytocompatibility analysis suggested that the regenerated COL fibril hydrogel showed excellent cell growth activity and proliferation ability when the dosage of TGase is less than 40 U/g. Further, animal experiments indicated that the targeted COL fibril hydrogel could significantly promote skin wound healing, exhibiting better capacity of skin tissue for regeneration than the COL hydrogel untreated as expected. Therefore, the reconstructed TGase cross-linked COL fibril hydrogel could serve as a novel soft material for wound healing promotion.