Ultra-Conformable Ionic Skin with Multi-Modal Sensing, Broad-Spectrum Antimicrobial and Regenerative Capabilities for Smart and Expedited Wound Care

Natural polymer starch-based materials for flexible electronic sensor development: A review of recent progress

In response to the burgeoning interest in the development of highly conformable and resilient flexible electronic sensors capable of transducing diverse physical stimuli, this review investigates the pivotal role of natural polymers, specifically those derived from starch, in crafting sustainable and biocompatible sensing materials. Expounding on cutting-edge research, the exploration delves into innovative strategies employed to leverage the distinctive attributes of starch in conjunction with other polymers for the fabrication of advanced sensors. The comprehensive discussion encompasses a spectrum of starch-based materials, spanning all-starch-based gels to starch-based soft composites, meticulously scrutinizing their applications in constructing resistive, capacitive, piezoelectric, and triboelectric sensors. These intricately designed sensors exhibit proficiency in detecting an array of stimuli, including strain, temperature, humidity, liquids, and enzymes, thereby playing a pivotal role in the continuous and non-invasive monitoring of human body motions, physiological signals, and environmental conditions. The review highlights the intricate interplay between material properties, sensor design, and sensing performance, emphasizing the unique advantages conferred by starch-based materials, such as self-adhesiveness, self-healability, and re-processibility facilitated by dynamic bonding. In conclusion, the paper outlines current challenges and future research opportunities in this evolving field, offering valuable insights for prospective investigations.

A highly stretchable smart dressing for wound infection monitoring and treatment

Smart dressings integrated with bioelectronics have attracted considerable attention and become promising solutions for skin wound management. However, due to the mechanical distinction between human body and the interface of electronics, previous smart dressings often suffered obvious degradation in electrical performance when attached to the soft and curvilinear wound sites. Here, we report a stretchable dressing integrated with temperature and pH sensor for wound status monitoring, as well as an electrically controlled drug delivery system for infection treatment. The wound dressing was featured with the deployment of liquid metal for seamless connection between rigid electrical components and gold particle-based electrodes, achieving a stretchable soft-hard interface. Stretching tests showed that both the sensing system and drug delivery system exhibited good stretchability and long-term stable conductivity with the resistance change rate less than 6 % under 50 % strain. Animal experiments demonstrated that the smart dressing was capable of detecting bacterial infection via the biomarkers of temperature and pH value and the infection factors of wound were significantly improved with therapy through electrically controlled antibiotics releasing. This proof-of-concept prototype has potential to significantly improve management of the wound, especially those with dynamic strain.

Ultrasensitive Biomimetic Skin with Multimodal and Photoelectric Dual-Signal Sensing

Mimicking biological skin enabling direct, intelligent interaction between users and devices, multimodal sensing with optical/electrical (OE) output signals is urgently required. Owing to this, this work aims to logically design a stretchable OE biomimetic skin (OE skin), which can sensitively sense complex external stimuli of pressure, strain, temperature, and localization. The OE skin consists of elastic thin polymer-stabilized cholesteric liquid crystal films, an ion-conductive hydrogel layer, and an elastic protective membrane formed with thin polydimethylsiloxane. The as-designed OE skin exhibits customizable structural color on demand, good thermochromism, and excellent mechanochromism, with the ability to extend the full visible spectrum, a good linearity of over 0.99, fast response speed of 93 ms, and wide temperature range of 119 °C. In addition, the conduction resistance variation of ion-conductive hydrogel exhibits excellent sensing capabilities under pressure, stretch, and temperature, endowing a good linearity of 0.99998 (stretching from 0 to 150%) and high thermal sensitivity of 0.86% per °C. Such an outstanding OE skin provides design concepts for the development of multifunctional biomimetic skin used in human-machine interaction and can find wide applications in intelligent wearable devices and human-machine interactions.

Preparation and characterization of 3D bioprinted gelatin methacrylate hydrogel incorporated with curcumin loaded chitosan nanoparticles for in vivo wound healing application

This study developed a biomimetic composite bioink consisting of gelatin methacrylate (GelMA) /chitosan nanoparticles (CSNPs) for extrusion-based 3D bioprinting. Additionally, curcumin(Cur)-loaded nanoparticles were incorporated which increased the proliferation and antibacterial activity of biomimetic skin constructs. The hydrogel, curcumin-loaded NPs, and the biocomposite was characterized chemically and physically. The results indicated proper modified gelatin with tunable physical characteristics, e.g., swelling ratio and biodegradability up to 1200 % and 25 days, respectively. In addition, the characterized CSNPs showed good distribution with a size of 370 nm and a zeta potential of 41.1 mV. We investigated the mechanical and cytocompatibility properties of chitosan nanoparticles encapsulated in hydrogel for emulating an extracellular matrix suitable for skin tissue engineering. CSNPs entrapped in GelMA (15 % w/v) exhibited controlled drug release during 5 days, which was fitted into various kinetic models to study the mass transfer mechanism behavior. Also, the composite hydrogels were effective as a barrier against both gram-positive and gram-negative bacteria at a concentration of 50 μg/ml nanoparticles in GelMA 15 %. Furthermore, the biocomposite was applied on Wistar rats for wound healing. As a result, this study provides a GelMA-NP50-Cur3 scaffold that promotes cell proliferation and decreases microbial infections in wounds.

Balanced chemical reactivity, antimicrobial properties and biocompatibility of decellularized dermal matrices for wound healing

The prevention of bacterial infection and prompt wound repair are crucial considerations when local skin tissue is compromised by burns, cuts, or similar injuries. Porcine acellular dermal matrix (pADM) is a commonly employed biological material in wound repair due to its inherent natural properties. Nonetheless, the pADM's primary constituent, collagen fibers, lacks antimicrobial properties and is vulnerable to bacterial infection when used in the treatment of incompletely debrided wounds. Meanwhile, conventional antimicrobial agents primarily consist of chemical compounds that exhibit inadequate biocompatibility and biological hazards. This research endeavors to create an antimicrobial collagen scaffold dressing utilizing the Schiff base reaction through the incorporation of oxidized chitosan diquaternary (ODHTCC) salt into the pADM. Compared with the unmodified pADM, ODHTCC-pADM (OD-pA) still retained the three-stranded helical structure of natural collagen. At an ODHTCC cross-linker concentration of 4%, the thermal denaturation temperature of OD-pA was 85 °C. According to the enzymatic degradation resistance test in vitro, the degradation resistance of OD-pA to type I collagenase was significantly improved compared with that of the uncross-linked pADM. In addition, OD-pA exhibited good antibacterial properties, with inhibition rates of 95.6% and 99.9% for E. coli and Staphylococcus aureus, respectively, and a cytotoxicity level 1, meeting the in vitro requirements of national biomedical materials. In vivo experiments showed that the OD-pA scaffold could better promote wound healing and more effectively promote the positive expression of bFGF, PDGF and VEGF. In conclusion, OD-pA has struck a balance between antibacterial properties, chemical reaction properties and biocompatibility, ultimately achieving controllability, and has broad application prospects in the field of antibacterial biomedical materials.

Smart Responsive and Controlled-Release Hydrogels for Chronic Wound Treatment

Chronic wounds are a major health challenge that require new treatment strategies. Hydrogels are promising drug delivery systems for chronic wound healing because of their biocompatibility, hydration, and flexibility. However, conventional hydrogels cannot adapt to the dynamic and complex wound environment, which involves low pH, high levels of reactive oxygen species, and specific enzyme expression. Therefore, smart responsive hydrogels that can sense and respond to these stimuli are needed. Crucially, smart responsive hydrogels can modulate drug release and eliminate pathological factors by changing their properties or structures in response to internal or external stimuli, such as pH, enzymes, light, and electricity. These stimuli can also be used to trigger antibacterial responses, angiogenesis, and cell proliferation to enhance wound healing. In this review, we introduce the synthesis and principles of smart responsive hydrogels, describe their design and applications for chronic wound healing, and discuss their future development directions. We hope that this review will inspire the development of smart responsive hydrogels for chronic wound healing.

One-Pot Preparation of Skin-Inspired Multifunctional Hybrid Hydrogel with Robust Wound Healing Capacity

Bioinspired hydrogels have demonstrated multiple superiorities over traditional wound dressings for wound healing applications. However, the fabrication of bioinspired hydrogel-based wound dressings with desired functionalities always requires multiple successive steps, time-consuming processes, and/or sophisticated protocols, plaguing their clinical applications. Here, a facile one-pot strategy is developed to prepare a skin-inspired multifunctional hydrogel within 30 min by incorporating elastin (an essential functional component of the dermal extracellular matrix), tannic acid, and chitosan into the covalently cross-linked poly(acrylamide) network through noncovalent interactions. The resulting hydrogel exhibits a Young's modulus (ca. 36 kPa) comparable to that of human skin, a high elongation-at-break (ca. 1550%), a satisfactory tensile strength (ca. 61 kPa), and excellent elastic self-restorability, enabling the hydrogel to synchronously and conformally deform with human skin when used as wound dressings. Importantly, the hydrogel displays a self-adhesive property to skin tissues with an appropriate bonding strength (ca. 55 kPa measured on intact porcine skin), endowing the hydrogel with the ability to rapidly self-adhere to intact human skin, sealing the wound surface and also easily being removed without residue left or trauma caused to the skin. The hydrogel also possesses remarkable antibacterial activity, antioxidant capability, and hemocompatibility. All of these collective beneficial properties enable the hydrogel to significantly accelerate the wound healing process, outperforming the commercial wound dressings.

Self-assembled carboxymethyl chitosan/zinc alginate composite film with excellent water resistant and antimicrobial properties for chilled meat preservation

A major way to reduce meat waste is to extend the shelf life of chilled meat with appropriate packaging. However, most of the packaging film cannot keep meat fresh because of its poor antibacterial and water resistance performance. In this paper, a composite film for chilled meat packaging was synthesized by simple self-assembly of zinc ions with chelating carboxyl groups. Introducing zinc ions into the composite system endows excellent water resistance and antibacterial properties to the film, which are demonstrated by the water vapor permeability and Escherichia coli and Staphylococcus aureus antibacterial tests. The as-prepared composite film also showed enhanced mechanical properties due to the formation of chelation bonds between zinc ions and carboxyl groups. Moreover, the chilled meat preservation test demonstrated the as-prepared composite film can significantly extend the shelf life of pork by five days, indicating its outstanding freshness preservation property. This work demonstrated a facile method to synthesize water-resistant and antimicrobial composite film, which can appear as an effective packaging material for chilled meat and offer a new idea to solve its short shelf-life problem.

Simple and Rapid Way to a Multifunctionally Conductive Hydrogel for Wearable Strain Sensors

Conductive hydrogels have gained increasing attention in the field of wearable smart devices. However, it remains a big challenge to develop a multifunctionally conductive hydrogel in a rapid and facile way. Herein, a conductive tannic acid-iron/poly (acrylic acid) hydrogel was synthesized within 30 s at ambient temperature by the tannic acid-iron (TA@Fe3+)-mediated dynamic catalytic system. The TA@Fe3+ dynamic redox autocatalytic pair could efficiently activate the ammonium persulfate to initiate the free-radical polymerization, allowing the gelation to occur easily and rapidly. The resulting hydrogel exhibited enhanced stretchability (3560%), conductivity (33.58 S/m), and strain sensitivity (gauge factor = 2.11). When damaged, it could be self-healed through the dynamic and reversible coordination bonds between the Fe3+ and COO- groups in the hydrogel network. Interestingly, the resulting hydrogel could act as a strain sensor to monitor various human motions including the huge movement of deformations (knuckle, wrist) and subtle motions (smiling, breathing) in real time due to its enhanced self-adhesion, good conductivity, and improved strain sensitivity. Also, the obtained hydrogel exhibited efficient electromagnetic interference (EMI) shielding performance with an EMI shielding effectiveness value of 24.5 dB in the X-band (8.2-12.4 GHz). Additionally, it displayed antibacterial properties, with the help of the activity of TA.

Near-infrared light-responsive multifunctional hydrogel releasing peptide-functionalized gold nanorods sequentially for diabetic wound healing

Treatment for chronic diabetic wounds remains a clinical challenge. Wound healing process occurs in three phases: inflammation, proliferation and remodeling. Several factors including bacterial infection, decreased local angiogenesis and diminished blood supply delay wound healing. There is an urgent need to develop wound dressings with multiple biological effects for different stages of diabetic wound healing. Here, we develop a multifunctional hydrogel with two-stage sequential release upon near-infrared (NIR) stimulation, antibacterial activity and pro-angiogenic efficacy. This hydrogel consists of covalently crosslinked bilayer structure, with the lower thermoresponsive poly(N-isopropylacrylamide)/gelatin methacrylate (NG) layer and the upper highly stretchable alginate/polyacrylamide (AP) layer embedding different peptide-functionalized gold nanorods (AuNRs) in each layer. Antimicrobial peptide-functionalized AuNRs released from NG layer exert antibacterial effects. After NIR irradiation, the photothermal transition efficacy of AuNRs synergistically enhances bactericidal efficacy. The contraction of thermoresponsive layer also promotes the release of embedded cargos during early stage. The pro-angiogenic peptide-functionalized AuNRs released from AP layer promote angiogenesis and collagen deposition by accelerating fibroblast and endothelial cell proliferation, migration and tube formation during the subsequent healing phases. Therefore, the multifunctional hydrogel with effective antibacterial activity, pro-angiogenic efficacy and sequential release behaviors is a potential biomaterial for diabetic chronic wound healing.

Highly Elastic and Strain Sensing Corn Protein Electrospun Fibers for Monitoring of Wound Healing

Due to the lack of sufficient elasticity and strain sensing capability, protein-based ultrafine fibrous tissue engineering scaffolds, though favorable for skin repair, can hardly fulfill on-spot wound monitoring during healing. Herein, we designed highly elastic corn protein ultrafine fibrous smart scaffolds with a three-layer structure for motion tracking at an unpackaged state. The densely cross-linked protein networks were efficiently established by introducing a highly reactive epoxy and provided the fiber substrates with wide-range stretchability (360% stretching range) and ultrahigh elasticity (99.91% recovery rate) at a wet state. With the assistance of the polydopamine bonding layer, a silver conductive sensing layer was built on the protein fibers and endowed the scaffolds with wide strain sensing range (264%), high sensitivity (gauge factor up to 210.55), short response time (<70 ms), reliable cycling stability, and long-lasting duration (up to 30 days). The unpackaged smart scaffolds could not only support cell growth and accelerate wound closure but also track motions on skin and in vivo and trigger alarms once excessive wound deformations occurred. These features not only confirmed the great potential of these smart scaffolds for applications in tissue reconstruction and wound monitoring but also proved the possibility of employing various plant protein ultrafine fibers as flexible bioelectronics.

Conductive hydrogels for tissue repair

Conductive hydrogels (CHs) combine the biomimetic properties of hydrogels with the physiological and electrochemical properties of conductive materials, and have attracted extensive attention in the past few years. In addition, CHs have high conductivity and electrochemical redox properties and can be used to detect electrical signals generated in biological systems and conduct electrical stimulation to regulate the activities and functions of cells including cell migration, cell proliferation, and cell differentiation. These properties give CHs unique advantages in tissue repair. However, the current review of CHs is mostly focused on their applications as biosensors. Therefore, this article reviewed the new progress of CHs in tissue repair including nerve tissue regeneration, muscle tissue regeneration, skin tissue regeneration and bone tissue regeneration in the past five years. We first introduced the design and synthesis of different types of CHs such as carbon-based CHs, conductive polymer-based CHs, metal-based CHs, ionic CHs, and composite CHs, and the types and mechanisms of tissue repair promoted by CHs including anti-bacterial, antioxidant and anti-inflammatory properties, stimulus response and intelligent delivery, real-time monitoring, and promoted cell proliferation and tissue repair related pathway activation, which provides a useful reference for further preparation of bio-safer and more efficient CHs used in tissue regeneration.

Hydrogel Nanoarchitectonics of a Flexible and Self-Adhesive Electrode for Long-Term Wireless Electroencephalogram Recording and High-Accuracy Sustained Attention Evaluation

Hydrogels are ideal building blocks to fabricate the next generation of electrodes for acquiring high-quality physiological electrical signals, for example, electroencephalography (EEG). However, collection of EEG signals still suffers from electrode deformation, sweating, extensive body motion and vibration, and environmental interference. Herein, polyvinyl alcohol and polyvinylpyrrolidone are selected to prepare a hydrogel network with tissue-like modulus and excellent flexibility. Additionally, polydopamine nanoparticles, obtained by polydopamine peroxidation, are integrated into the hydrogel to endow them with higher transparency, higher self-adhesion, and lower impedance. Consequently, a multichannel and wirelessly operated hydrogel electrode can establish a conformal and stable interface with tissue and illustrate high channel uniformity, low interfacial contact impedance, low power noise, long-term stability, and a tolerance to sweat and motion. Furthermore, the hydrogel electrode shows the unprecedented ability to classify the recorded high-quality prefrontal EEG signals into seven-category sustained attention with high accuracy (91.5%), having great potential applications in the assessment of human consciousness and in multifunctional diagnoses.

Sacrificial gelatin of PAM-Alginate-BC hydrogel tube with tunable diameter as nerve conduit

Peripheral nerve regeneration is still one of the biggest challenges, autologous nerve transplantation is the 'gold standard' for evaluating its alternative therapy. However, the source of autologous nerves is limited, it is imminent to synthesize a nerve-guiding catheter material with a controllable diameter of a small orifice. Sacrificial gelatin polyacrylamide-Alginate-Bacterial cellulose (PAM-Alginate-BC) hydrogel overcomes poor mechanical properties with tunable diameter. In addition, the PAM-Alginate-BC hydrogel possesses the beneficial properties required for cell scaffolding with surface adhesion ability. The PAM-Alginate-BC materials options have potential applications in peripheral nerve regeneration.

Kartogenin-Conjugated Double-Network Hydrogel Combined with Stem Cell Transplantation and Tracing for Cartilage Repair

The effectiveness of existing tissue-engineering cartilage (TEC) is known to be hampered by weak integration of biocompatibility, biodegradation, mechanical strength, and microenvironment supplies. The strategy of hydrogel-based TEC holds considerable promise in circumventing these problems. Herein, a non-toxic, biodegradable, and mechanically optimized double-network (DN) hydrogel consisting of polyethylene glycol (PEG) and kartogenin (KGN)-conjugated chitosan (CHI) is constructed using a simple soaking strategy. This PEG-CHI-KGN DN hydrogel possesses favorable architectures, suitable mechanics, remarkable cellular affinity, and sustained KGN release, which can facilitate the cartilage-specific genes expression and extracellular matrix secretion of peripheral blood-derived mesenchymal stem cells (PB-MSCs). Notably, after tracing the transplanted cells by detecting the rabbit sex-determining region Y-linked gene sequence, the allogeneic PB-MSCs are found to survive for even 3 months in the regenerated cartilage. Here, the long-term release of KGN is able to efficiently and persistently activate multiple genes and signaling pathways to promote the chondrogenesis, chondrocyte differentiation, and survival of PB-MSCs. Thus, the regenerated tissues exhibit well-matched histomorphology and biomechanical performance such as native cartilage. Consequently, it is believed this innovative work can expand the choice for developing the next generation of orthopedic implants in the loadbearing region of a living body.

Debonding-On-Demand Polymeric Wound Patches for Minimal Adhesion and Clinical Communication

Herein, a multifunctional bilayer wound patch is developed by integrating a debonding-on-demand polymeric tissue adhesive (DDPTA) with an ionic conducting elastomer (ICE). As a skin adhesive layer, the DDPTA is soft and adherent at skin temperature but hard and non-tacky when cooled, so it provides unique temperature-triggered quick adhesion and non-forced detachment from the skin. During use, the dense surface of the DDPTA prevents blood infiltration and reduces unnecessary blood loss with gentle pressing. Moreover, its hydrophobic matrix helps to repel blood and prevents the formation of clots, thus precluding wound tearing during its removal. This unique feature enables the DDPTA to avoid the severe deficiencies of hydrophilic adhesives, providing a reliable solution for a wide range of secondary wound injuries. The DDPTA is versatile in that it can be covered with ICE to configure a DDPTA@ICE patch for initiating non-verbal communication systems by the fingers, leading toward sign language recognition and a remote clinical alarm system. This multifunctional wound patch with debonding-on-demand can promote a new style of tissue sealant for convenient clinical communication.

Highly tough and ionic conductive starch/poly(vinyl alcohol) hydrogels based on a universal soaking strategy

High-performance hydrogels with favorable mechanical strength, high modulus, sufficient ionic conductivity and freezing resistance have far-ranging applications in flexible electronic equipment. Nevertheless, it is challenging to combine admirable mechanical properties and high ionic conductivity into one hydrogel. Herein, a facile strategy was developed for the preparation of the hydrogel with excellent strength (1.45 MPa), super Young's modulus (8.85 MPa) and high conductivity (1.47 S/m) using starch and poly(vinyl alcohol) (PVA) as raw materials. The starch/PVA/Gly/Na₃Cit (SPGN) gel was firstly cross-linked by crystalline regions of PVA upon freezing-thawing cycles. It was further immersed in the saturated Na₃Cit solution to enhance the interaction between the substrates through the salting-out effect. The effect of soaking time on the crystallinity, intermolecular interactions, mechanical and electrical properties of SPGN gel was demonstrated by X-ray diffraction, Fourier transform infrared spectroscopy, tensile and impedance testing measurements. The introduction of glycerol and Na₃Cit also endowed SPGN gels with favorable anti-freezing properties. The SPGN gel could maintain high mechanical flexibility and ionic conductivity at -15 °C.

Programmable gear-based mechanical metamaterials

Elastic properties of classical bulk materials can hardly be changed or adjusted in operando, while such tunable elasticity is highly desired for robots and smart machinery. Although possible in reconfigurable metamaterials, continuous tunability in existing designs is plagued by issues such as structural instability, weak robustness, plastic failure and slow response. Here we report a metamaterial design paradigm using gears with encoded stiffness gradients as the constituent elements and organizing gear clusters for versatile functionalities. The design enables continuously tunable elastic properties while preserving stability and robust manoeuvrability, even under a heavy load. Such gear-based metamaterials enable excellent properties such as continuous modulation of Young's modulus by two orders of magnitude, shape morphing between ultrasoft and solid states, and fast response. This allows for metamaterial customization and brings fully programmable materials and adaptive robots within reach.

A starch-regulated adhesive hydrogel dressing with controllable separation properties for painless dressing change

The development of hydrogel dressings provides unprecedented opportunities for clinical medicine. However, the traditional hydrogel dressings cannot achieve controllable adhesion and separation, which often brings unbearable pain and secondary damage to patients during removal. In this work, a starch-regulated adhesive hydrogel dressing with controllable separation properties is reported. This hydrogel dressing can achieve rapid separation through the dissociation competition mechanism of polar small molecules, which will not cause any damage or discomfort to the skin or tissues, and greatly facilitate dressing replacement. The adhesive strength of the hydrogel reaches 0.06 MPa, and remains relatively stable after repeated utilization. Meanwhile, the inhibition rate of the hydrogel for E. coli, S. aureus and C. albicans is more than 99.9%. At the same time, the hydrogel also has good swelling properties, mechanical properties and biocompatibility, and exhibits a high healing efficiency (95.01 ± 3.76%) in a rat full-thickness skin defect model. This novel hydrogel dressing with controllable separation properties provides a facile and effective method for wound management and treatment, and has great promise for long-term application of wound dressings.

Hydrogels for Treatment of Different Degrees of Osteoarthritis

Osteoarthritis (OA) is a common disease that severely restricts human activities and degrades the quality of life. Every year, millions of people worldwide are diagnosed with osteoarthritis, placing a heavy burden on society. Hydrogels, a polymeric material with good biocompatibility and biodegradability, are a novel approach for the treatment of osteoarthritis. In recent years, this approach has been widely studied with the development of materials science and tissue engineering technology. We reviewed the research progress of hydrogels in the treatment of osteoarthritis in the past 3 years. We summarized the required hydrogel properties and current applications according to the development and treatment of osteoarthritis. Furthermore, we listed the challenges of hydrogels for different types of osteoarthritis and presented prospects for future development.

A Composite Hydrogel Containing Mesoporous Silica Nanoparticles Loaded With Artemisia argyi Extract for Improving Chronic Wound Healing

Chronic wounds are a major health problem with increasing global prevalence, which endangers the physical and mental health of those affected and is a heavy burden to healthcare providers. Artemisia argyi extract (AE) has excellent antibacterial and anti-inflammatory properties. In this research, we developed AE loaded composite hydrogel scaffold based on methacrylate gelatin (GelMA)/methacrylate hyaluronic acid (HAMA) and mesoporous silica nanoparticle (MSN) as sustained-release drug carrier vehicles for the treatment of chronic wounds. The presented GelMA/1%HAMA hydrogel possessed stable rheological properties, suitable mechanical properties, appropriate biodegradability, swelling, sustained-release AE capacity. In vitro antibacterial and cell experiments showed that the GelMA/HAMA/MSN@AE hydrogel had excellent antibacterial activity and biocompatibility and induced macrophages to differentiate into M2 phenotype. In vivo wound healing of rat full-thickness cutaneous wounds further demonstrated that the prepared GelMA/HAMA/MSN@AE hydrogel could significantly promote chronic wound healing by upregulating the expression of IL-4, TGF-β1, CD31, and α-SMA but downregulating the expression of TNF-α and IFN-γ and promoting M1-M2 macrophages polarization. Altogether, we believe that the GelMA/HAMA/MSN@AE hydrogel will have wide application prospects in healing chronic wounds.

Wound Dressing: From Nanomaterials to Diagnostic Dressings and Healing Evaluations

Wound dressings based on nanomaterials play a crucial role in wound treatment and are widely used in a whole range of medical settings, from minor to life-threatening tissue injuries. This article presents an educational review on the accumulating knowledge in this multidisciplinary area to lay out the challenges and opportunities that lie ahead and ignite the further and faster development of clinically valuable technologies. The review analyzes the functional advantages of nanomaterial-based gauzes and hydrogels as well as hybrid structures thereof. On this basis, the review presents state-of-the-art advances to transfer the (semi)blind approaches to the evaluation of a wound state to smart wound dressings that enable real-time monitoring and diagnostic functions that could help in wound evaluation during healing. This review explores the translation of nanomaterial-based wound dressings and related medical aspects into real-world use. The ongoing challenges and future opportunities associated with nanomaterial-based wound dressings and related clinical decisions are presented and reviewed.

Nanofiber/hydrogel core-shell scaffolds with three-dimensional multilayer patterned structure for accelerating diabetic wound healing

Impaired angiogenesis is one of the predominant reasons for non-healing diabetic wounds. Herein, a nanofiber/hydrogel core–shell scaffold with three-dimensional (3D) multilayer patterned structure (3D-PT-P/GM) was introduced for promoting diabetic wound healing with improved angiogenesis. The results showed that the 3D-PT-P/GM scaffolds possessed multilayered structure with interlayer spacing of about 15–80 μm, and the hexagonal micropatterned structures were uniformly distributed on the surface of each layer. The nanofibers in the scaffold exhibited distinct core–shell structures with Gelatin methacryloyl (GelMA) hydrogel as the shell and Poly (d, l-lactic acid) (PDLLA) as the core. The results showed that the porosity, water retention time and water vapor permeability of the 3D-PT-P/GM scaffolds increased to 1.6 times, 21 times, and 1.9 times than that of the two-dimensional (2D) PDLLA nanofibrous scaffolds, respectively. The in vitro studies showed that the 3D-PT-P/GM scaffolds could significantly promote cell adhesion, proliferation, infiltration and migration throughout the scaffolds, and the expression of cellular communication protein-related genes, as well as angiogenesis-related genes in the same group, was remarkably upregulated. The in vivo results further demonstrated that the 3D-PT-P/GM scaffolds could not only effectively absorb exudate and provide a moist environment for the wound sites, but also significantly promote the formation of a 3D network of capillaries. As a result, the healing of diabetic wounds was accelerated with enhanced angiogenesis, granulation tissue formation, and collagen deposition. These results indicate that nanofiber/hydrogel core–shell scaffolds with 3D multilayer patterned structures could provide a new strategy for facilitating chronic wound healing.

Multi-functional SiO32--releasing hydrogel with bioinspired mechanical properties and biodegradability for vascularized skeletal muscle regeneration

Vascularized skeletal muscle regeneration remains a great medical need but significant challenge. Biomaterial strategies that can facilitate the regeneration of muscle fibers and blood vessels are unavailable. Herein, we report...

Bioinspired Triboelectric Nanosensors for Self-Powered Wearable Applications

The sustainable operation of wearable sensors plays an important role in continuous and longtime health monitoring. Conventional batteries, which are bulky and rigid, do not satisfy these requirements and, rather, cause additional economic burdens and environmental problems by regular replacement of power sources. This article provides a review on an alternative solution in the form of self-powered devices that can harvest energy from the surrounding environment to support the operation of the wearable sensor. The Review starts with an introduction of the self-powered triboelectric nanosensors (TENSs) and its two independent modules: the energy harvester and the sensing module. The Review continues with the TENS-related bioinspired designs for wearable applications, while providing a bird's-eye view of their characteristics and applications. The ongoing challenges and prospects for providing personal healthcare with self-powered TENS are presented and discussed.

Bifunctional Smart Hydrogel Dressing with Strain Sensitivity and NIR-Responsive Performance

Smart response hydrogel has a broad application prospect in human health real-time monitoring due to its responses to a variety of stimuli. In this study, we developed a novel smart hydrogel dressing based on conductive MXene nanosheets and a temperature-sensitive PNIPAm polymer. γ-Methacryloxypropyltrimethoxysilane (KH570) was selected to functionalize the surface of MXene further to improve the interface compatibility between MXene and PNIPAm. Our prepared K-M/PNIPAm hydrogel was found to have a strain-sensitive property, as well as a respond to NIR phase change and volume change. When applied as a strain flexible sensor, this K-M/PNIPAm hydrogel exhibited a high strain sensitivity with a gauge factor (GF) of 4.491, a broad working strain range of ≈250%, a fast response of ∼160 ms, and good cycle stability (i.e., 3000 s at 20% strain). Besides, this K-M/PNIPAm hydrogel can be used as an efficient NIR light-controlled drug release carrier to achieve on-demand drug release. This work paved the way for the application of smart response hydrogel in human health real-time monitoring and NIR-controlled drug release functions.

Highly synergistic, electromechanical and mechanochromic dual-sensing ionic skin with multiple monitoring, antibacterial, self-healing, and anti-freezing functions

A novel electromechanical and mechanochromic dual-sensing ionic skin (DSI-skin) with multiple biological functions is achieved by mimicking biological skin.