Bioinspired mechanically active adhesive dressings to accelerate wound closure

Gelatin-DOPA-knob/fibrinogen hydrogel inspired by fibrin polymerization and mussel adhesion for rapid and robust hemostatic sealing

Tissue adhesives have attracted significant interest in the field of hemostasis. However, challenges including weak tissue adhesion, inadequate biocompatibility, and instability limit their clinical applications. Here, we have developed a gelatin-DOPA-knob/fibrinogen hydrogel inspired by the fibrin polymerization and mussel adhesion, resulting in a biocompatible bioadhesive with outstanding adhesion performance and great storage stability. This strategy involves modifying gelatin with knob peptides and catechol groups inducing crosslinking with fibrinogen to form a hydrogel via knob-hole interactions, and enhancing interfacial adhesion performance by interacting with the blood-covered tissue through catechol groups and knob peptides. This hydrogel exhibits rapid gelation, enhanced mechanical strength and adhesion properties, compared to the commonly used fibrin glue in surgery. The hydrogel significantly reduces the time required to hemostasis and the amount of blood loss in severe hemorrhage models. It ensures superior hemostatic efficacy, excellent biocompatibility, and long-term storage stability, which holds significant promise in medical settings.

Piezoelectric dual-network tough hydrogel with on-demand thermal contraction and sonopiezoelectric effect for promoting infected-joint-skin-wound healing via FAK and AKT signaling pathways

The dynamic and whole stage management of infected wound healing throughout the entire repair process, including intelligent on-demand wound closure and the regulation of the transition from bactericidal to reparative phases, remains a major challenge. This study develops sonopiezoelectric-effect-mediated on-demand reactive-oxygen-species release by incorporating piezoelectric barium titanate modified with gold nanoparticles and a thermally responsive dual-network tough hydrogel dressing with a physical network structure based on ureidopyrimidinone-modified gelatin crosslinked by multiple hydrogen bonds, and with a chemical network structure based on N-isopropylacrylamide and methacryloyl gelatin formed via radical polymerization. This hydrogel exhibits temperature-sensitive softening, on-demand thermal contraction performance, high mechanical strength, good tissue adhesion, outstanding piezoelectricity, tunable sonopiezoelectric behavior, regulatable photothermal properties and desirable biocompatibility. The tunable sonopiezoelectric effect enables the hydrogel to eliminate wound bacteria in the short term, and effectively promote human fibroblast proliferation and migration over the long term. The hydrogel dressing actively contracts to close wound edges and further promotes the healing of MRSA-infected skin defects in the neck of mice by promoting fibroblast migration, enhancing collagen deposition and facilitating angiogenesis via up-regulating the FAK and AKT signaling pathways, providing a novel design strategy for developing dressings targeting chronic joint-skin wounds.

Advances in Designer Materials for Chronic Wound Healing

Significance: Nonhealing or chronic wounds represent a significant and growing global health concern, imposing substantial burdens on individuals, health care systems, and economies worldwide. Although the standard-of-care treatment involves the application of wound dressings, most dressing materials are not specifically designed to address the pathological processes underlying chronic wounds. This review highlights recent advances in biomaterial design tailored to chronic wound healing. Recent Advances: Chronic wounds are characterized by persistent inflammation, impaired granulation tissue formation, and delayed re-epithelialization. Newly developed designer materials aim to manage reactive oxygen species and extracellular matrix degradation to suppress inflammation while promoting vascularization, cell proliferation, and epithelial migration to accelerate tissue repair. Critical Issues: Designing optimal materials for chronic wounds remains challenging due to the diverse etiology and a multitude of pathological mechanisms underlying chronic wound healing. While designer materials can target specific aberrations, designing a materials approach that restores all aberrant wound-healing processes remains the Holy Grail. Addressing these issues requires a deep understanding of how cells interact with the materials and the complex etiology of chronic wounds. Future Directions: New material approaches that target wound mechanics and senescence to improve chronic wound closure are under development. Layered materials combining the best properties of the approaches discussed in this review will pave the way for designer materials optimized for chronic wound healing.

A Bio-Responsive Hydrogel with Spatially Heterogeneous Structure for Treating Infectious Tissue Injuries

Infectious tissue injuries, exacerbated by bacterial infections and antibiotic resistance, pose significant challenges for treatment and may lead to life-threatening systemic infections. In this study, a bio-responsive hydrogel system is developed, leveraging silver ions (Ag⁺) encapsulated in Preyssler-type polyoxometalates (POMs). The Ag⁺ ions are selectively released in response to endogenous sodium ions (Na⁺) within the biological environment, enabling broad-spectrum antibacterial activity. The POM serves as a protective matrix for Ag⁺, preserving its bioactivity while mitigating cytotoxicity and the reduction in antimicrobial efficacy associated with prolonged exposure. Additionally, a dual-channel technique is employed to fabricate fiber membranes with controllable and continuously stacked chemical compositions, ensuring efficient and uniform POM incorporation via hydrogen bonding within the fiber matrix. Subsequently, in situ hierarchical cross-linking process generated a spatially heterogeneous hydrogel with an interpenetrating network structure at multiple scales. This differentiated microstructure facilitates the controlled loading and release of diverse therapeutic components. Meanwhile, bioactive exosomes are integrated into the hydrogel, further enhancing its regenerative potential for treating infectious tissue injuries. In vitro and in vivo experiments demonstrated that the advanced hydrogel system provide a viable and efficient platform for addressing the challenges associated with infectious tissue injuries, offering a promising strategy for clinical applications.

Medical adhesives for soft tissue wound repair with good biocompatibility, flexibility, and high adhesive strength

Compared with traditional soft tissue wound closure methods such as sutures and staplers, bioadhesives have significant advantages in terms of tissue compatibility, ease of use, and wound adaptability, making them a hot topic among current wound repair materials. This study aimed to select polyurethane materials with good biocompatibility and high mechanical strength, optimize the prepolymer formula, develop new curing agents, and obtain a new dual-component polyurethane bioadhesive. Furthermore, key research will be conducted on its mechanical properties and tissue adhesion performance. The results show that through the optimization of prepolymer formulations and the development of novel curing agents, a dual-component polyurethane bioadhesive with good biocompatibility, flexibility, and high adhesive strength was obtained. This adhesive can quickly and effectively bond common soft tissue (skin, muscle) traumatic wounds, with an adhesive strength of up to 72 kPa. This adhesive matches well with the mechanical properties of soft tissues and safely and tightly adheres to the surface of soft tissues. Additionally, this dual-component polyurethane adhesive holds promise for repairing other soft tissues, such as the lungs and intestines, with broad application prospects.

Development of Bioorthogonally Degradable Tough Hydrogels Using Enamine N-Oxide Based Crosslinkers

Inducibly degradable polymers present new opportunities to integrate tough hydrogels into a wide range of biomaterials. Rapid and inducible degradation enables fast transition in material properties without sacrificing material integrity prior to removal. In pursuit of bioorthogonal chemical modalities that will enable inducible polymer degradation in biologically relevant environments, enamine N-oxide crosslinkers are developed for double network acrylamide-based polymer/alginate hydrogels. Bioorthogonal dissociation initiated by the application of aqueous diboron solution through several delivery mechanisms effectively lead to polymer degradation. Their degradation by aqueous B2(OH)4 solution results in a fracture energy half-life of <10 min. The biocompatibility of the degradable hydrogels and B2(OH)4 reagent is assessed, and the removability of strongly adhered tough hydrogels on mice skin is evaluated. Thermoresponsive PNiPAAm/Alg hydrogels are fabricated and application of the hydrogels as a chemically inducible degradable intraoral wound dressing is demonstrated. It is demonstrated through in vivo maximum tolerated dose studies that diboron solution administered to mice by oral gavage is well tolerated. Successful integration of enamine N-oxides within the tough double network hydrogels as chemically degradable motifs demonstrates the applicability of enamine N-oxides in the realm of polymer chemistry and highlights the importance of chemically induced bioorthogonal dissociation reactions for materials science.

Photoactive broad-spectrum dressings with antimicrobial and antitumoral properties

In this work the development of photoactive dressings (PAD) with dual purpose, is presented. These PAD can be used for the topical treatment of persistent infections caused by fungi and bacteria and are also applicable in light antitumor therapy for carcinoma. The synthesized PAD were designed employing conjugated polymer nanoparticles (CPN) doped with platinum porphyrin which serve as polymerization photoinitiators and photosensitizers for the production of reactive oxygen species (ROS). This approach led to the synthesis of N-vinyl-2-pyrrolidone (NVP) hydrogels co-polymerized with [2-(methacryloyloxy)ethyl] trimethylammonium chloride (METAC). NVP and METAC were selected to impart a good biocompatibility with eukaryotic cell lines and antimicrobial properties, respectively. The combination of METAC with an efficient photogeneration of ROS by doped CPN resulted in a material with outstanding antimicrobial features. These dressings are capable of producing an aseptic environment upon irradiation and demonstrates a bacteriostatic profile in dark conditions. Additionally, the dressings fulfill critical requirements for topical applications, providing protection and acting as a barrier, with appropriate mechanical and swelling properties; as well as adequate water vapor transmission rates. The synthesized PAD have been shown to be biocompatible and non-toxic to erythrocytes and HaCaT cell line. PAD demonstrated efficacy in eliminating microbes such as fungi and bacteria. The underlying light-induced killing mechanism involved protein photooxidation, which amplified the effects of METAC mechanism that disrupt cellular membranes. Furthermore, in vitro studies using carcinoma cell lines displayed a complete cell eradication using a relatively low light dose (36 J/cm2 at 395 nm). These promising results reveal also the potential of PAD in the treatment of skin cancer.

Selectively oxidized chitin as a degradable and biocompatible hemostat for uncontrolled bleeding and wound healing

Chitin (CT), one of the most abundant biopolymers, is insoluble in both dilute aqueous solutions and common organic solvents. In traditional hemostatic applications, chitin must be either converted into acid-soluble chitosan by removing acetyl groups or dissolved in an alkaline aqueous solution at -20 °C. However, acetyl groups are more advantageous than amino groups in promoting hemostasis, biocompatibility, biodegradability, and wound healing. A significant challenge remains in retaining acetyl groups while directly preparing a hemostatic agent from chitin without requiring its dissociation. In this study, we have successfully applied oxidized chitin (OCT) as a hemostatic material, which is directly derived from chitin through a TEMPO-mediated selective oxidation of C6 primary hydroxyl groups to carboxyl groups. Due to its significantly higher hydrophilicity compared to chitin, OCT rapidly forms a gel upon contact with blood, efficiently sealing broken blood vessels and facilitating wound healing. Among OCTs with varying carboxylate contents and the commercial chitosan hemostat Celox™, OCT-24 demonstrated not only the best hemostatic performance in some injury models but also excellent biocompatibility and biodegradability, effectively preventing tissue adhesion and promoting wound healing. The selective oxidation offers a straightforward method for developing a highly effective hemostatic material from chitin to address uncontrolled massive bleeding.

Hydrogel-Based Biointerfaces: Recent Advances, Challenges, and Future Directions in Human-Machine Integration

Human-machine interfacing (HMI) has emerged as a critical technology in healthcare, robotics, and wearable electronics, with hydrogels offering unique advantages as multifunctional materials that seamlessly connect biological systems with electronic devices. This review provides a detailed examination of recent advancements in hydrogel design, focusing on their properties and potential applications in HMI. We explore the key characteristics such as biocompatibility, mechanical flexibility, and responsiveness, which are essential for effective and long-term integration with biological tissues. Additionally, we highlight innovations in conductive hydrogels, hybrid and composite materials, and fabrication techniques such as 3D/4D printing, which allow for the customization of hydrogel properties to meet the demands of specific HMI applications. Further, we discuss the diverse classes of polymers that contribute to hydrogel conductivity, including conducting, natural, synthetic, and hybrid polymers, emphasizing their role in enhancing electrical performance and mechanical adaptability. In addition to material design, we examine the regulatory landscape governing hydrogel-based biointerfaces for HMI applications, addressing the key considerations for clinical translation and commercialization. An analysis of the patent landscape provides insights into emerging trends and innovations shaping the future of hydrogel technologies in human-machine interactions. The review also covers a range of applications, including wearable electronics, neural interfaces, soft robotics, and haptic systems, where hydrogels play a transformative role in enhancing human-machine interactions. Thereafter, the review addresses the challenges hydrogels face in HMI applications, including issues related to stability, biocompatibility, and scalability, while offering future perspectives on the continued evolution of hydrogel-based systems for HMI technologies.

Material Design, Fabrication Strategies, and the Development of Multifunctional Hydrogel Composites Dressings for Skin Wound Management

The skin is fragile, making it very vulnerable to damage and injury. Untreated skin wounds can pose a serious threat to human health. Three-dimensional polymer network hydrogels have broad application prospects in skin wound dressings due to their unique properties and structure. The therapeutic effect of traditional hydrogels is limited, while multifunctional composite hydrogels show greater potential. Multifunctional hydrogels can regulate wound moisture through formula adjustment. Moreover, hydrogels can be combined with bioactive ingredients to improve their performance in wound healing applications. Stimulus-responsive hydrogels can respond specifically to the wound environment and meet the needs of different wound healing stages. This review summarizes the material types, structure, properties, design considerations, and formulation strategies for multifunctional hydrogel composite dressings used in wound healing. We discuss various types of recently developed hydrogel dressings, highlights the importance of tailoring their physicochemical properties, and addresses potential challenges in preparing multifunctional hydrogel wound dressings.

Bioinspired hierarchical porous tough adhesive to promote sealing of high-pressure bleeding

Timely and stable sealing of uncontrolled high-pressure hemorrhage in emergency situations outside surgical units remains a major clinical challenge, contributing to the high mortality rate associated with trauma. The currently widely used hemostatic bioadhesives are ineffective for hemorrhage from major arteries and the heart due to the absence of biologically compatible flexible structures capable of simultaneously ensuring conformal tough adhesion and biomechanical support. Here, inspired by the principle of chromatin assembly, we present a tissue-conformable tough matrix for robust sealing of severe bleeding. This hierarchical matrix is fabricated through a phase separation process, which involves the in-situ formation of nanoporous aggregates within a microporous double-network (DN) matrix. The dispersed aggregates disrupt the rigid physical crosslinking of the original DN matrix and function as a dissipative component, enabling the aggregate-based DN (aggDN) matrix to efficiently dissipate energy during stress and achieve improved conformal attachment to soft tissues. Subsequently, pre-activated bridging polymers facilitate rapid interfacial bonding between the matrix and tissue surfaces. They synergistically withstand considerable hydraulic pressure of approximately 700 mmHg and demonstrate exceptional tissue adhesion and sealing in rat cardiac and canine aortic hemorrhages, outperforming the commercially available bioadhesives. Our findings present a promising biomimetic strategy for engineering biomechanically compatible and tough adhesive hydrogels, facilitating prompt and effective treatment of hemorrhagic wounds.

Photothermal-manipulatable shape memory polyacrylamide/gelatin Janus hydrogel with drug carrier array for invasive wound closure and responsive drug release

Traditional wound closure methods often present several issues, including additional puncture wounds, adverse effects from anesthesia, and noticeable scarring. Inspired by embryonic wound healing, a Janus hydrogel (PG/Au-Asp@PCM) is designed to manipulate non-invasive wound closure by photothermal-responsive self-contraction of PG/Au-Asp@PCM, which is attributed to the shape memory behavior of PG/Au-Asp@PCM under near-infrared (NIR). Wherein, gelatin acts as a thermally reversible "switch" and polyacrylamide creates stable and cross-linked "net-points". The elongated PG/Au-Asp@PCM can be temporarily fixed at 4 °C, and subsequently self-contracts upon NIR irradiation, generating a recovery force of 10 kPa, adequate for the closure of wound spontaneously. The Janus hydrogel also incorporates a drug carrier loaded with phase change material (PCM) and aspirin. The PCM absorbs heat during its phase transition above 42 °C, offering the photothermal-responsive release of aspirin on-demand; additionally, it also reduces the risk of skin burn during NIR exposure. Animal studies confirm the effectiveness of PG/Au-Asp@PCM in wound closure. Moreover, wounds treated with PG/Au-Asp@PCM exhibit reduced inflammation, increased thickness of epidermal and dermal layers, and a smoother appearance without scarring. These findings reinforce the feasibility of the photothermal strategy utilizing PG/Au-Asp@PCM for non-invasive wound closure, resulting in enhanced cosmetic appearance and improved wound healing outcomes.

Fundamentals of wound care for amputation prevention

The initial skin breakdown and subsequent healing processes are complex and influenced by various parameters, including systemic factors, infectious bioburden, and perfusion. Vascular wounds comprise inadequate inflow (due to peripheral artery disease), microvascular damage (result of diabetes mellitus), or vasoconstriction. Normal healing of acute wounds occurs in a sequence of defined stages; however, if a dysregulated inflammatory state ensues, it is classified as chronic. Both chronic and vascular wounds carry an increased risk of amputation. Therefore, holistic wound care is crucial in preventing limb loss. This review outlines a systematic approach to wound assessment and examines the latest recommendations for managing vascular wounds, focusing on strategies for preventing amputations.

Polysaccharide-Based Self-Healing Hydrogel for pH-Induced Smart Release of Lauric Acid to Accelerate Wound Healing

It is highly desirable yet significantly challenging to fabricate an injectable, self-healing, controlled-release wound dressing that is responsive to the alkaline pH of the wounds. Herein, we propose a facile approach to prepare pH-responsive chitosan-oxidized carboxymethyl cellulose (CS-o-CMC) hydrogel constructs in which gelation was achieved via electrostatic and Schiff base formation. Importantly, the Schiff base was formed in acidic medium and the final pH of pregel solution was intrinsically raised to 7.0-7.4 due to the cross-linking by β-glycerol phosphate. The self-healing behavior of the hydrogel was an enthalpy-driven process and efficient in alkaline compared to acidic pH. The pH responsiveness offered a controlled release of lauric acid (LA) from CS-o-CMC/LA hydrogel and regulated the M2 polarization. Overall, reduction in inflammation led to rapid vascularization, reepithelialization, and significantly accelerated wound healing in rats. Our findings demonstrate a promising strategy for developing injectable, immunomodulatory wound dressings tailored to the challenging environment of wounds.

In Vitro Engineered ECM-incorporated Hydrogels for Osteochondral Tissue Repair: A Cell-Free Approach

Prevalence of osteoarthritis has been increasing in aging populations, which has necessitated the use of advanced biomedical treatments. These involve grafts or delivering drug molecules entrapped in scaffolds. However, such treatments often show suboptimal therapeutic effects due to poor half-life and off-target effects of drug molecules. As a countermeasure, a 3D printable robust hydrogel-based tissue-repair platform is developed containing decellularized extracellular matrix (dECM) from differentiated mammalian cells as the therapeutic cargo. Here, pre-osteoblastic and pre-chondrogenic murine cells are differentiated in vitro, decellularized, and incorporated into methacrylated gelatin (GelMA) solutions to form osteogenic (GelO) and chondrogenic (GelC) hydrogels, respectively. Integrating the bioactive dECM from differentiated cell sources allows GelO and GelC to induce differentiation in human adipose-derived stem cells (hASCs) toward osteogenic and chondrogenic lineages. Further, GelO and GelC can be covalently adhered using a carbodiimide coupling reaction, forming a multi-layered hydrogel with potential application as a bioactive osteochondral plug. The designed multi-layered hydrogel can also induce differentiation of hASCs in vitro. In conclusion, the bioactive dECM carrying 3D printed robust hydrogel offers a promising new drug and cell-free therapeutic strategy for bone and cartilage repair and future osteoarthritis management.

Photodynamic hemostatic silk fibroin film with photo-controllable modulation of macrophages for bacteria-infected wound healing

Massive hemorrhage and chronic wounds caused by bacterial infections after trauma are significant challenges in clinical practice. An ideal hemostatic wound dressing should simultaneously manage bleeding and prevent bacterial infections and also hold excellent biocompatibility and bioactivities to successfully modulate immune microenvironments to promote wound healing. In this study, a silk fibroin-based light-responsive film was demonstrated to possess effective capacity of light-induced non-compressible hemostasis on liver hemorrhage and tail bleeding in vivo by binding with blood platelets to promote the clotting cascade. The blood loss of the rats was significantly less after C-MASiF films were applied, which were 1223.33 ± 347.9 mg (liver trauma) and 363.33 ± 60.28 mg (tail trimming). Importantly, the films exhibited photo-controllable modulation activity on macrophages through repeated near-infrared irradiation to regulate the immune microenvironment to enhance photodynamic antibacterial therapy. Moreover, the light-responsive silk fibroin film effectively promoted Staphylococcus aureus infected burn wound healing in vivo. The quantity of residual bacteria in the wound sites of mice in the C-MASiF films group (0.05 ± 0.0047 × 108 CFU mL-1) was considerably less than that in the control group (3.18 ± 0.75 × 108 CFU mL-1), and the wound area in the C-MASiF group (78.03% ± 4.12%) was considerably smaller than that in the control group (60.33% ± 8.81%) after 14 days. Overall, this light-responsive silk fibroin film can provide a powerful strategy for wound healing of burns.

Multiscale modelling of active hydrogel elasticity driven by living polymers: softening by bacterial motor protein FtsZ

We present a neo-Hookean elasticity theory for hybrid mechano-active hydrogels, integrating motor proteins into polymer meshes to create composite materials with active softening due to modulable chain overlaps. Focusing on polyacrylamide (PA) hydrogels embedded with FtsZ, a bacterial cytokinetic protein powered by GTP, we develop a multiscale model using microscopic Flory theory of rubbery meshes through mesoscopic De Gennes' scaling concepts for meshwork dynamics and phenomenological Landau's formalism for second-order phase transitions. Our theoretical multiscale model explains the active softening observed in hybrid FtsZ-PA hydrogels by incorporating modulable meshwork dynamics, such as overlapping functionality and reptation dynamics, into an active mean-field of unbinding interactions. The novel FtsZ-based metamaterial and companion multiscale theory offer insights for designing, predicting, and controlling complex active hydrogels, with potential applications in technology and biomedicine.

Self-Cross-Linked Collagen Sponge from the Alosa sapidissima Scale for Hemostasis and Wound Healing Applications

Type I collagen, a crucial component maintaining the structural integrity and physiological function of various tissues, is widely regarded as one of the most suitable biomaterials for healthcare applications. In this study, shad scales, used for treating ulcers, scalds, and burns in traditional Chinese medicine, were exploited for type I collagen extraction. After self-assembly into hydrogels, the extracted collagen was subsequently freeze-dried to form collagen sponges. The collagen sponge promoted rapid hemostasis, neovascularization, and immune regulation. Additionally, it accelerated the formation of granulation tissue, re-epithelialization, and collagen remodeling at the wound site in full-thickness skin wound rat models. Consequently, the shad scale collagen sponge holds great promise for the treatment of chronic wounds and skin regeneration. Notably, the shad was sourced from sustainably recirculating aquaculture systems (RAS) farms that adhere to the Traceable Management of Animal Products Safety, ensuring that the derived collagen possesses potential in the medical apparatus market.

Low molecular weight fucoidan induces M2 macrophage polarization to attenuate inflammation through activation of the AMPK/mTOR autophagy pathway

Fucoidan, a sulfated polysaccharide with a complex structure, has gradually become the focus of biomedical research due to its remarkable biological activity and low toxicity. In this research, it was noted that low molecular weight fucoidan (LMWF) exhibited significant antimicrobial effects on Methicillin-resistant Staphylococcus aureus (MRSA) and promoted polarization towards M2 macrophages, leading to a substantial reduction in inflammatory responses within the lipopolysaccharide (LPS)-activated macrophages. We further explored the mechanism underlying the anti-inflammation activity. Our findings indicated that LMWF significantly enhanced the phosphorylation level of AMP-activated protein kinase (AMPK), inhibited the phosphorylation of the mammalian target of rapamycin (mTOR), and enhanced the expression of LC3II. Meanwhile, Compound C (CC) substantially reversed the anti-inflammation effect of LMWF, indicating that the AMPK pathway plays a pivotal role in this effect. In in vivo research, LMWF revealed impressive anti-inflammatory potential. LMWF treatment significantly eliminated MRSA and ameliorated inflammatory symptoms in mice's MRSA-infected skin wound model. Further analysis using Western Blot (WB) indicated significant AMPK/mTOR signaling pathway activation in mice treated with LMWF, which led to accelerated polarization of macrophages from the M1 to the M2 phenotype. In summary, we systematically explored the mechanism by which LMWF exerts anti-inflammatory effects through in vitro and in vivo experiments. It was confirmed that LMWF effectively induced the conversion of macrophages to an anti-inflammatory M2 phenotype by activating the AMPK/mTOR pathway. Simultaneously, LMWF effectively eradicated MRSA and accelerated wound healing in mice. This finding provides an important theoretical basis for further research on fucoidan.

Naturally Inspired Tree-Ring Structured Dressing Provides Sustained Wound Tightening and Accelerates Closure

Mechanically regulated wound dressings require a rational combination of contraction and adhesion functions as well as balancing exudate-induced swelling issues. However, many of the reported dressings face the dilemma of impaired function and impeded wound self-contraction due to fluid-absorbing swelling. In this study, inspired by the tree ring, a core-ring structured hydrogel dressing capable of mechanical modulation is designed, and prepare it using a simple two-step photopolymerization process. The core covers the center of the wound, contracts spontaneously at body temperature to generate a contractile force of 3.4 kPa, and resists swelling. Meanwhile, the ring adheres to the normal epidermis around the wound and transfers the contraction stress to the wound edge. The integration of a functionally independent core and ring ultimately achieves effective wound traction and avoids dressing swelling. In murine and porcine skin wound-healing models, this hydrogel with a closely connected core and ring promotes healing by accelerating epidermal closure (50% closure in mouse skin on day 2, 85% closure in pig skin on day 8), collagen deposition, vascular maturation, and extracellular matrix remodeling. These results can guide further research on mechanical force modulation in wound healing, with the potential for clinical translation.

Peptide-Induced Hydrogelation with Ordered Metal-Organic Framework Nanoparticles Generating Reactive Oxygen Species for Integrated Wound Repair

Hydrogels, with their high water content and flexible nature, are a promising class of medical dressings for combating bacterial wound infections. However, their development has been hindered by low sterilization efficiency. Here, this issue is addressed by designing a peptide hydrogel that assembles ordered metal-organic framework (MOF) nanoparticles with photocatalytic bactericidal activity. Specifically, a short peptide, Nap-Gly-Phe-Phe-His (Nap-GFFH), is used to induce the assembly of zinc-imidazolate MOF (ZIF-8) into a hydrogel (NHZ gel). This innovative structure integrates three key features: 1) ZIF-8 nanoparticles are encapsulated within the hydrogel, overcoming their inherent brittleness, insolubility, and limited moldability; 2) the ordered ZIF-8 structure enhances charge transfer, enabling efficient generation of reactive oxygen species (ROS); and 3) ZIF-8 simultaneously improves the photocatalytic bactericidal efficiency and mechanical properties of the hydrogel. The NHZ gel demonstrates remarkable antibacterial performance, achieving >99.9% and 99.99% inactivation of Escherichia coli and Staphylococcus aureus, respectively, within 15 min of simulated solar radiation. Additionally, the NHZ gel exhibits excellent biocompatibility, water retention, and exudate absorption, highlighting its broad potential for wound healing.

Hydrogel Fibers-Based Biointerfacing

The unique 1D structure of fibers offers intriguing attributes, including a high length-to-diameter ratio, miniatured size, light-weight, and flexibility, making them suitable for various biomedical applications, such as health monitoring, disease treatment, and minimally invasive surgeries. However, traditional fiber devices, typically composed of rigid, dry, and non-living materials, are intrinsically different from the soft, wet, and living essence of biological tissues, thereby posing grand challenges for long-term, reliable, and seamless interfacing with biological systems. Hydrogel fibers have recently emerged as a promising candidate, in light of their similarity to biological tissues in mechanical, chemical and biological aspects, as well as distinct fiber geometry. In this review, a comprehensive overview of recent progress in hydrogel fibers-based biointerfacing technology is provided. It thoroughly summarizes the manufacturing strategy and functional design, especially for hydrogel fibers with distinct optical and electron conductive performance, as well as responsiveness to triggers including thermal, magnetic field and ultrasonic wave, etc. Such unique attributes enable various biomedical applications, which are also examined in detail. Future challenges and potential directions, including biosafety, long-term reliability, sterilization, multi-modalities integration and intelligent therapeutic systems, are raised. This review will serve as a valuable resource for further advancement and implementation as next-generation biointerfacing technology.

In Situ Formation of Hydrogels Loaded with ZnO Nanoparticles Promotes Healing of Diabetic Wounds in Rats

The challenge of healing diabetic skin wounds presents a significant hurdle in clinical practice and scientific research. In response to this pressing concern, we have developed a temperature-sensitive, in situ-forming hydrogel comprising poly(n-isopropylacrylamide166-co-n-butyl acrylate9) -poly(ethylene glycol) -poly(n-isopropylacrylamide166-co-butyl acrylate9) copolymer, denoted as PEP, in combination with zinc oxide nanoparticles, forming what we refer to as PEP-ZnO hydrogel. The antimicrobial properties of the PEP-ZnO hydrogel against methicillin-resistant Staphylococcus aureus were rigorously assessed by using the bacteriostatic banding method. In vitro evaluations encompassed examinations of hemocompatibility and biocompatibility. The study further employed a diabetic Sprague-Dawley (SD) rat whole-layer trauma model for comprehensive in vivo analyses. In vivo healing assessments revealed the potential of the PEP-ZnO hydrogel, characterized by increased collagen deposition and enhanced vascularization at the trauma site, thus significantly expediting the healing process. Collectively, these findings endorse the PEP-ZnO hydrogel as a safe and effective dressing for addressing chronic wounds in diabetic patients. This hydrogel not only holds promise for improving the quality of life for diabetic individuals grappling with chronic wounds but also represents a noteworthy advancement in wound care.

Asymmetric porous hydrogel encapsulating vulcanized molecular brushes with anti-bacterial adhesion, anti-infection, and pro-healing properties towards infected wound treatment

Inspired by the hierarchical structure of the skin, asymmetric porous hydrogel encapsulating vulcanized molecular brushes (VMB@APH) as multifunctional wound dressing has been integrally constructed. The as-obtained VMB@APH effectively combines the anti-bacterial adhesion, anti-infection, and pro-healing properties, which is of great significance for accelerating the recovery of infected wounds.

Multiple strategies approach: A novel crosslinked hydrogel forming chitosan-based microneedles chemowrap patch loaded with 5-fluorouracil liposomes for chronic wound cancer treatment

Untreated or poorly managed chronic wounds can progress to skin cancer. Topically applied 5-fluorouracil (5-FU), a nonspecific cytostatic agent, can cause various side effects. Its high polarity also results in low cell membrane affinity and bioavailability. Hydrogel, used for its occlusive effect, is one platform for treating chronic wounds combined with PEGylated liposomes (LPs), developed to increase drug-skin affinity. This research aimed to develop a novel hydrogel forming chitosan-based microneedles (HFM) chemowrap patch containing 5-FU PEGylated LPs, improving 5-FU efficiency for pre-carcinogenic and carcinogenic skin lesions. The results indicated that the 5-FU-PEGylated LPs-loaded HFM chemowrap patch exhibited desirable physical and mechanical characteristics with complete penetration ability. Furthermore, in vivo skin permeation studies demonstrated the highest percentage of 5-FU permeated the skin (42.06 ± 11.82 %) and skin deposition (75.90 ± 1.13 %) compared to the other treatments, with demonstrated superior percentages of complete wound healing in in vivo (47.00 ± 5.77 % wound healing at day 7) and in NHF cells (92.79 ± 7.15 % at 48 h). Furthermore, 5-FU-PEGylated LPs-loaded HFM chemowrap patches exhibit efficient anticancer activity while maintaining safety for normal cells. The results also show that the developed formulation of a 5-FU-PEGylated LPs-loaded HFM chemowrap patch could enhance apoptosis higher than that of the 5-FU solution. Consequently, 5-FU PEGylated LPs-loaded HFM chemowrap patch represented a promising drug delivery approach for treating pre-carcinogenic and carcinogenic skin lesions.

A Skin Stress Shielding Platform Based on Body Temperature-Induced Shrinking of Hydrogel for Promoting Scar-Less Wound Healing

Stress concentration surrounding wounds drives fibroblasts into a state of high mechanical tension, leading to the delay of wound healing, exacerbating pathological fibrosis, and even causing tissue dysfunction. Here, an innovative skin stress-shielding hydrogel wound dressing is reported that makes the wound sites shrink as a response to body temperature and then remolds the stress micro-environment of wound sites to reduce the formation of skin scars. Composed of a modified natural temperature-sensitive polymer cross-linked with polyacrylic acid networks, this hydrogel wound dressing has demonstrated a substantial decrease in scar area for full-thickness wounds in rat models. The physical forces exerted by the wound dressing are instrumental in attenuating the activation and transduction of fibroblasts within the wound sites, thereby mitigating the excessive deposition of the extracellular matrix (ECM). Notably, the wound dressing significantly down-regulates the expression of transforming growth factor-β1(TGF-β1) and collagen I, while concurrently exerting a dramatic inhibitory effect on the integrin-focal adhesion kinase (FAK)/phosphorylated-FAK (p-FAK) signaling pathway. Collectively, the fabrication of functional hydrogels with a stress-shielding profile is a new route for achieving scar-less wound healing, thus offering immense potential for improving clinical outcomes and restoring tissue integrity.

An advanced hydrogel dressing system with progressive delivery and layer-to-layer response for diabetic wound healing

Wound healing in diabetic patients presents a significant challenge due to delayed inflammatory responses, which obstruct subsequent healing stages. In response, we have developed a progressive, layer-by-layer responsive hydrogel, specifically designed to meet the dynamic requirements of diabetic wounds throughout different healing phases. This hydrogel initiates with a glucose-responsive layer formed by boronate ester bonds between 4-arm-poly (ethylene glycol) succinimidyl glutarate (4arm-PEG-SG) and 3-aminophenylboronic acid. This configuration ensures precise control over the physicochemical properties, facilitating accurate drug release during the healing process. Furthermore, we have incorporated an active pharmaceutical ingredient ionic liquid (API) composed of diclofenac and L-carnitine. This combination effectively tackles the solubility and stability issues commonly associated with anti-inflammatory drugs. To further refine drug release, we integrated matrix metalloproteinase-9 (MMP-9)-sensitive gelatin microcapsules, ensuring a controlled release and preventing the abrupt, uneven drug distribution often seen in other systems. Our hydrogel's rheological properties closely resemble human skin, offering a more harmonious approach to diabetic wound healing. Overall, this progressive layer-by-layer responsive wound management system, which is a safe, efficient, and intelligent approach, holds significant potential for the clinical treatment of diabetic wounds. STATEMENT OF SIGNIFICANCE: The two main problems of diabetic wounds are the long-term infiltration of inflammation and the delayed repair process. In this experiment, a glucose-responsive hierarchical drug delivery system was designed to intelligently adjust gel properties to meet the needs of inflammation and repair stage of wound healing, accelerate the transformation of inflammation and repair stage, and accelerate the process of repair stage. In addition, in order to achieve accurate drug release in anti-inflammatory layer hydrogels and avoid sudden drug release due to poor solubility of anti-inflammatory small molecule drugs, we constructed a ionic liquid of active pharmaceutical ingredients (API-ILs) using diclofenac and L-carnitine as raw materials. It was wrapped in MMP-9 enzyme active gelatin microcapsule to construct a double-reaction anti-inflammatory layer gel to achieve accurate drug release. These findings highlight the potential of our system in treating diabetic wounds, providing a significant advance in wound treatment.

Designing injectable dermal matrix hydrogel combined with silver nanoparticles for methicillin-resistant Staphylococcus aureus infected wounds healing

Hydrogel-based delivery systems have now emerged as a pivotal platform for addressing chronic tissue defects, leveraging their innate capacity to suppress pathogenic infections and facilitate expedited tissue regeneration. In this work, an injectable hydrogel dressing, termed AgNPs-dermal matrix hydrogel (Ag@ADMH), has been designed to expedite the healing process of wounds afflicted with methicillin-resistant Staphylococcus aureus (MRSA), featuring sustained antibacterial efficacy. The synthesis of the hydrogel dressing entailed a self-assembly process of collagen fibers within an acellular dermal matrix to construct a three-dimensional scaffold, encapsulated with plant polyphenol-functionalized silver nanoparticles (AgNPs). The Ag@ADMH demonstrated exceptional biocompatibility, and enables a sustained release of AgNPs, ensuring prolonged antimicrobial activity. Moreover, the in vitro RT-qPCR analysis revealed that compared with ADMH, Ag@ADMH diminish the expression of iNOS while augmenting CD206 expression, thereby mitigating the inflammatory response and fostering wound healing. Especially, the Ag@ADMH facilitated a reduction in M1 macrophage polarization, as evidenced by a significant decrement in the M1 polarization trend and an enhanced M2/M1 ratio in dermal matrix hydrogels laden with AgNPs, corroborated by confocal microscopy and flow cytometry analyses of macrophage phenotypes. The in vivo assessments indicated that Ag@ADMH minimized fibrous capsule formation. In a full-thickness skin defect model of MRSA infection, the formulation significantly attenuated the inflammatory response by reducing MPO and CD68 expression levels, concurrently promoting collagen synthesis and CD34 expression, pivotal for vasculogenesis, thereby accelerating the resolution of MRSA-infected wounds. These attributes underscore the injectable extracellular matrix hydrogel as a formidable strategy for the remediation and regeneration of infected wounds.

Mechanically Interlocked [an]Daisy Chain Adhesives with Simultaneously Enhanced Interfacial Adhesion and Cohesion

Adhesives have been widely used to splice and repair materials to meet practical needs of humanity for thousands of years. However, developing robust adhesives with balanced adhesive and cohesive properties still remains a challenging task. Herein, we report the design and preparation of a robust mechanically interlocked [an]daisy chain network (DCMIN) adhesive by orthogonal integration of mechanical bonds and 2-ureido-4[1H]-pyrimidone (UPy) H-bonding in a single system. Specifically, the UPy moiety plays a dual role: it allows the formation of a cross-linked network and engages in multivalent interactions with the substrate for strong interfacial bonding. The mechanically interlocked [an]daisy chain, serving as the polymeric backbone of the adhesive, is able to effectively alleviate applied stress and uphold network integrity through synergistic intramolecular motions, and thus significantly improves the cohesive performance. Comparative analysis with the control made of the same quadruple H-bonding network but with non-interlocked [an]daisy chain backbones demonstrates that our DCMIN possesses superior adhesion properties over a wide temperature range. These findings not only contribute to a deep understanding of the structure-property relationship between microscopic mechanical bond motions and macroscopic adhesive properties but also provide a valuable guide for optimizing design principles of robust adhesives.

Temperature-responsive self-contraction nanofiber/hydrogel composite dressing facilitates the healing of diabetic-infected wounds

Bacterial infections and long-term inflammation cause serious secondary damage to chronic diabetic wounds and hinder the wound healing processes. Currently, multifunctional hydrogels have shown promising effects in chronic wound repair. However, traditional hydrogels only keep the wound moist and protect it from bacterial infection, and cannot provide mechanical force to contract the wound edges to achieve facilitated wound closure. Here, an asymmetric composite dressing was created by combining biaxially oriented nanofibers and hydrogel, inspired by the double-layer structure of the traditional Chinese medicinal plaster patch, for managing chronic wounds. Specifically, electrospun Poly-(lactic acid-co-trimethylene carbonate) (PLATMC) nanofibers and methacrylate gelatin (GelMa) hydrogel loaded with Epinecidin-1@chitosan (Epi-1@CS) nanoparticles are assembled as the temperature-responsive self-contracting nanofiber/hydrogel (TSNH) composite dressing. The substrate layer of PLATMC nanofibers combines topological morphology with material properties to drive wound closure through temperature-triggered contraction force. The functional layer of GelMa hydrogel is loaded with Epi-1@CS nanoparticles that combine satisfactory cytocompatibility, and antioxidant, anti-inflammatory, and antibacterial properties. Strikingly, in vivo, the TSNH dressing could regulate the diabetic wound microenvironment, thereby promoting collagen deposition, facilitating angiogenesis, and reducing the inflammatory response, which promotes the rapid healing of chronic wounds. This study highlights the potential of synergizing mechanical and biochemical signals in enhancing chronic wound treatment. Overall, this TSNH composite dressing is provided as a reliable approach to solving the long-standing problem of chronically infected wound healing.

Mechanoresponsive Drug Release from a Flexible, Tissue-Adherent, Hybrid Hydrogel Actuator

Soft robotic technologies for therapeutic biomedical applications require conformal and atraumatic tissue coupling that is amenable to dynamic loading for effective drug delivery or tissue stimulation. This intimate and sustained contact offers vast therapeutic opportunities for localized drug release. Herein, a new class of hybrid hydrogel actuator (HHA) that facilitates enhanced drug delivery is introduced. The multi-material soft actuator can elicit a tunable mechanoresponsive release of charged drug from its alginate/acrylamide hydrogel layer with temporal control. Dosing control parameters include actuation magnitude, frequency, and duration. The actuator can safely adhere to tissue via a flexible, drug-permeable adhesive bond that can withstand dynamic device actuation. Conformal adhesion of the hybrid hydrogel actuator to tissue leads to improved mechanoresponsive spatial delivery of the drug. Future integration of this hybrid hydrogel actuator with other soft robotic assistive technologies can enable a synergistic, multi-pronged treatment approach for the treatment of disease.

Cuttlefish ink-derived melanin nanoparticle-embedded tremella fuciformis polysaccharide hydrogels for the treatment of MRSA-infected diabetic wounds

Diabetic wounds arise great attention as they are difficult to heal and easily suffer from serious bacterial infection. However, the overuse of antibiotics increases the resistance of bacteria and makes common drugs ineffective. Here, we developed a photothermal hydrogel (TFP/NP) composed of tremella fuciformis polysaccharides (TFPs) and cuttlefish ink-derived melanin nanoparticles (NPs). The NPs can produce reliable photothermal effects under near-infrared laser (NIR) irradiation and help to remove the bacteria in the wounds, while TFPs were able to form hydrogel frameworks which possessed anti-inflammatory effects and could be applied to promote wound healing. The TFP/NP hydrogels produced stable thermal effects under NIR irradiation and could continuously kill bacteria. The experiment on a full-layer skin wound sMRSA activity and could improve the healing efficiency. The wounds of the mice could be repaired within 14 days after reasonable treatment. In addition, the hydrogels play significant roles in promoting collagen deposition, anti-inflammation, angiogenesis, and cell proliferation during the therapeutic process. This research provides a simple and effective method for the therapy of bacterial infection wounds through the synergistic effect of TFPs and NPs.

Carboxymethyl chitosan nanoparticle-modulated cationic hydrogels doped with copper ions for combating bacteria and facilitating wound healing

The simultaneous administration of antibacterial treatment and acceleration of tissue regeneration are crucial for the effective healing of infected wounds. In this work, we developed a facile hydrogel (PCC hydrogel) through coordination and hydrogen interactions by polymerizing acrylamide monomers in the presence of carboxymethyl chitosan nanoparticles and copper ions. The prepared PCC hydrogel demonstrated effective bacterial capture from wound exudation and exhibited a potent bactericidal activity against methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. Furthermore, slow release of copper ions from the hydrogel facilitated wound healing by promoting cell migration, collagen deposition and angiogenesis. Additionally, the PCC hydrogel possessed excellent biocompatibility and hemostatic properties. The practical effectiveness of PCC hydrogel in addressing bacterial infections and facilitating wound healing was verified using a mouse model of MRSA-induced wound infections. Overall, this work presents a simple yet efficient multifunctional hydrogel platform that integrates antibacterial activity, promotion of wound healing, and hemostasis for managing bacteria-associated wounds.

Rheological Characterization of Genipin-Based Crosslinking Pigment and O-Carboxymethyl Chitosan-Oxidized Hyaluronic Acid In Situ Formulable Hydrogels

The aim of this study was to develop a material capable of rapidly absorbing bodily fluids and forming a resilient, adhesive, viscoelastic hydrogel in situ to prevent post-surgical adhesions. This material was formulated using O-carboxymethyl chitosan (O-CMCS), oxidized hyaluronic acid (OHA), and a crosslinking pigment derived from genipin and glutamic acid (G/GluP). Both crosslinked (O-CMCS/OHA-G/GluP) and non-crosslinked hydrogels (O-CMCS/OHA) were evaluated using a HAAKE™ MARS™ rheometer for their potential as post-surgical barriers. A rheological analysis, including dynamic oscillatory measurements, revealed that the crosslinked hydrogels exhibited significantly higher elastic moduli (G'), indicating superior gel formation and mechanical stability compared to non-crosslinked hydrogels. The G/GluP crosslinker enhanced gel stability by increasing the separation between G' and G″ and achieving a lower loss tangent (tan δ < 1.0), indicating robustness under dynamic physiological conditions. The rapid hydration and gelation properties of the hydrogels underscore their effectiveness as physical barriers. Furthermore, the O-CMCS/OHA-G/GluP hydrogel demonstrated rapid self-healing and efficient application via spraying or spreading, with tissue adherence and viscoelasticity to facilitate movement between tissues and organs, effectively preventing adhesions. Additionally, the hydrogel proved to be both cost effective and scalable, highlighting its potential for clinical applications aimed at preventing post-surgical adhesions.

In Situ Triggered Self-Contraction Bioactive Microgel Assembly Accelerates Diabetic Skin Wound Healing by Activating Mechanotransduction and Biochemical Pathway

Chronic nonhealing skin wounds, characterized by reduced tissue contractility and inhibited wound cell survival under hyperglycemia and hypoxia, present a significant challenge in diabetic care. Here, an advanced self-contraction bioactive core-shell microgel assembly with robust tissue-adhesion (SMART-EXO) is introduced to expedite diabetic wound healing. The SMART-EXO dressing exhibits strong, reversible adhesion to damaged tissue due to abundant hydrogen and dynamic coordination bonds. Additionally, the core-shell microgel components and dynamic coordination bonds provide moderate rigidity, customizable self-contraction, and an interlinked porous architecture. The triggered in situ self-contraction of the SMART-EXO dressing enables active, tunable wound contraction, activating mechanotransduction in the skin and promoting the optimal fibroblast-to-myofibroblast conversion, collagen synthesis, and angiogenesis. Concurrently, the triggered contraction of SMART-EXO facilitates efficient loading and on-demand release of bioactive exosomes, contributing to re-epithelialization and wound microenvironment regulation in diabetic mice. RNA-seq results reveal the activation of critical signaling pathways associated with mechanosensing and exosome regulation, highlighting the combined biomechanical and biochemical mechanisms. These findings underscore SMART-EXO as a versatile, adaptable solution to the complex challenges of diabetic wound care.

Advancing Flexible Sensors through On-Demand Regulation of Supramolecular Nanostructures

The evolution of flexible sensors heavily relies on advances in soft-material design and sensing mechanisms. Supramolecular chemistry offers a powerful toolbox for manipulating nanoscale and molecular structures within soft materials, thus fostering recent advancements in flexible sensors and electronics. Supramolecular interactions have been utilized to nanoengineer functional sensing materials or construct chemical sensors with lower cost and broader targets. In this perspective, we will highlight the use of supramolecular interactions to regulate and optimize nanostructures within functional soft materials and illustrate their importance in expanding the nanocavities of bioreceptors for chemical sensing. Overall, a bridge between tissue-mimicking flexible sensors and cell-mimetic supramolecular chemistry has been built, which will further advance human healthcare innovation.

Nature-inspired adhesive systems

Many organisms in nature thrive in intricate habitats through their unique bio-adhesive surfaces, facilitating tasks such as capturing prey and reproduction. It's important to note that the remarkable adhesion properties found in these natural biological surfaces primarily arise from their distinct micro- and nanostructures and/or chemical compositions. To create artificial surfaces with superior adhesion capabilities, researchers delve deeper into the underlying mechanisms of these captivating adhesion phenomena to draw inspiration. This article provides a systematic overview of various biological surfaces with different adhesion mechanisms, focusing on surface micro- and nanostructures and/or chemistry, offering design principles for their artificial counterparts. Here, the basic interactions and adhesion models of natural biological surfaces are introduced first. This will be followed by an exploration of research advancements in natural and artificial adhesive surfaces including both dry adhesive surfaces and wet/underwater adhesive surfaces, along with relevant adhesion characterization techniques. Special attention is paid to stimulus-responsive smart artificial adhesive surfaces with tunable adhesive properties. The goal is to spotlight recent advancements, identify common themes, and explore fundamental distinctions to pinpoint the present challenges and prospects in this field.

Magneto-responsive biocomposites in wound healing: from characteristics to functions

The number of patients with non-healing wounds continuously increases, and has become a prominent societal issue that imposes a heavy burden on both patients and the entire healthcare system. Although traditional dressings play an important role in wound healing, the complexity and diversity of the healing process pose serious challenges in this field. Magneto-responsive biocomposites, with their excellent biocompatibility, remote spatiotemporal controllability, and unique convenience, demonstrate enticing advantages in the field of wound dressings. However, current research on magneto-responsive biocomposites as wound dressings lacks comprehensive and in-depth reviews, which to some extent, restricts the deeper understanding and further development of this field. Based on this, this paper reviews the latest advances in magnetic responsive wound dressings for wound healing. First, we review the process of skin wound healing and parameters for assessing repair progress. Then, we systematically discuss the preparation strategies and unique characteristics of magneto-responsive biocomposites, focusing on magneto-induced orientation, magneto-induced mechanical stimulation, and magnetocaloric effect. Subsequently, this review elaborates the multiple mechanisms of magneto-responsive biocomposites in promoting wound healing, including regulating cell behavior, enhancing electrical signal, controlling drug release, and accelerating tissue reconstruction. Finally, we further propose the development direction and future challenges of magnetic responsive biomaterials as wound dressings in clinical application.

Hydroxypropyl chitosan/ε-poly-l-lysine based injectable and self-healing hydrogels with antimicrobial and hemostatic activity for wound repair

The biggest obstacle to treating wound healing continues to be the production of simple, inexpensive wound dressings that satisfy the demands associated with full process of repair at the same time. Herein, a series of injectable composite hydrogels were successfully prepared by a one-pot method by utilizing the Schiff base reaction as well as hydrogen bonding forces between hydroxypropyl chitosan (HCS), ε-poly-l-lysine (EPL), and 2,3,4-trihydroxybenzaldehyde (TBA), and multiple cross-links formed by the reversible coordination between iron (III) and pyrogallol moieties. Notably, hydrogel exhibits excellent physicochemical properties, including injectability, self-healing, water retention, and adhesion, which enable to fill irregular wounds for a long period, providing a suitable moist environment for wound healing. Interestingly, the excellent hemostatic properties of the hydrogel can quickly stop bleeding and avoid the serious sequelae of massive blood loss in acute trauma. Moreover, the powerful antimicrobial and antioxidant properties also protect against bacterial infections and reduce inflammation at the wound site, thus promoting healing at all stages of the wound. The study of biohydrogel with multifunctional integration of wound treatment and smart medical treatment is clarified by this line of research.

Rapid-Response Water-Shrink Films with High Output Work Density Based on Polyethylene Oxide and α-Cyclodextrin for Autonomous Wound Closure

Conventional wound closure methods, including sutures and tissue adhesives, present significant challenges for self-care treatment, particularly in the context of bleeding wounds. Existing stimuli-responsive contractile materials designed for autonomous wound closure frequently lack sufficient output work density to generate the force needed to bring the wound edges into proximity or necessitate stimuli that are not compatible with the human body. Here, semi-transparent, flexible, and water-responsive shrinkable films, composed of poly(ethylene oxide) and α-cyclodextrin, are reported. These films exhibit remarkable stability under ambient conditions and demonstrate significant contraction (≈50%) within 6 s upon exposure to water, generating substantial contractile stress (up to 6 MPa) and output work density (≈1028 kJ m-3), which is 100 times larger than that of conventional hydrogel and 25 times larger than that of skeletal muscles. Remarkably, upon hydration, these films are capable of lifting objects 10 000 times their own weight. Leveraging this technology, water-shrink tapes, which, upon contact with water, effectively constrict human skin and autonomously close bleeding wounds in animal models within 10 seconds, are developed further. This work offers a novel approach to skin wound management, showing significant potential for emergency and self-care scenarios.

Cryogel wound dressings based on natural polysaccharides perfectly adhere to irregular wounds for rapid haemostasis and easy disassembly

Skin injuries can have unexpected surfaces, leading to uneven wound surfaces and inadequate dressing contact with these irregular surfaces. This can decrease the dressing's haemostatic action and increase the healing period. This study recommends the use of sticky and flexible cryogel coverings to promote faster haemostasis and efficiently handle uneven skin wounds. Alginate cryogels have a fast haemostatic effect and shape flexibility due to their macroporous structure. The material demonstrates potent antibacterial characteristics and enhances skin adherence by adding grafted chitosan with gallic acid. In irregular defect wound models, cryogels can cling closely to uneven damage surfaces due to their amorphous nature. Furthermore, their macroporous structure allows for quick haemostasis by quickly absorbing blood and wound exudate. After giving the dressing a thorough rinse, its adhesive strength reduces and it is simple to remove without causing any damage to the wound. Cryogel demonstrated faster haemostasis than gauze in a wound model on a rat tail, indicating that it has considerable potential for use as a wound dressing in the biomedical area.

Eco-Friendly Production of Polyvinyl Alcohol/Carboxymethyl Cellulose Wound Healing Dressing Containing Sericin

Wound dressing production represents an important segment in the biomedical healthcare field, but finding a simple and eco-friendly method that combines a natural compound and a biocompatible dressing production for biomedical application is still a challenge. Therefore, the aim of this study is to develop wound healing dressings that are environmentally friendly, low cost, and easily produced, using natural agents and a physical crosslinking technique. Hydrogel wound healing dressings were prepared from polyvinyl alcohol/carboxymethyl cellulose and sericin using the freeze-thawing method as a crosslinking method. The morphological characterization was carried out by scanning electron microscopy (SEM), whereas the mechanical analysis was carried out by dynamic mechanical analysis (DMA) to test the tensile strength and compression properties. Then, the healing property of the wound dressing material was tested by in vitro and ex vivo tests. The results show a three-dimensional microporous structure with no cytotoxicity, excellent stretchability with compressive properties similar to those of human skin, and excellent healing properties. The proposed hydrogel dressing was tested in vitro with HaCaT keratinocytes and ex vivo with epidermal tissues, demonstrating an effective advantage on wound healing acceleration. Accordingly, this study was successful in developing wound healing dressings using natural agents and a simple and green crosslinking method.

Visible-Light Cross-Linkable Multifunctional Hydrogels Loaded with Exosomes Facilitate Full-Thickness Skin Defect Wound Healing through Participating in the Entire Healing Process

The management of severe full-thickness skin defect wounds remains a challenge due to their irregular shape, uncontrollable bleeding, high risk of infection, and prolonged healing period. Herein, an all-in-one OD/GM/QCS@Exo hydrogel was prepared with catechol-modified oxidized hyaluronic acid (OD), methylacrylylated gelatin (GM), and quaternized chitosan (QCS) and loaded with adipose mesenchymal stem cell-derived exosomes (Exos). Cross-linking of the hydrogel was achieved using visible light instead of ultraviolet light irradiation, providing injectability and good biocompatibility. Notably, the incorporation of catechol groups and multicross-linked networks in the hydrogels conferred strong adhesion properties and mechanical strength against external forces such as tensile and compressive stress. Furthermore, our hydrogel exhibited antibacterial, anti-inflammatory, and antioxidant properties along with wound-healing promotion effects. Our results demonstrated that the hydrogel-mediated release of Exos significantly promotes cellular proliferation, migration, and angiogenesis, thereby accelerating skin structure reconstruction and functional recovery during the wound-healing process. Overall, the all-in-one OD/GM/QCS@Exo hydrogel provided a promising therapeutic strategy for the treatment of full-thickness skin defect wounds through actively participating in the entire process of wound healing.

Acer tegmentosum extract-mediated silver nanoparticles loaded chitosan/alginic acid scaffolds enhance healing of E. coli-infected wounds

This work developed Acer tegmentosum extract-mediated silver nanoparticles (AgNPs) loaded chitosan (CS)/alginic acid (AL) scaffolds (CS/AL-AgNPs) to enhance the healing of E. coli-infected wounds. The SEM-EDS and XRD results revealed the successful formation of the CS/AL-AgNPs. FTIR analysis evidenced that the anionic group of AL (-COO-) and cationic amine groups of CS (-NH3+) were ionically crosslinked to form scaffold (CS/AL). The CS/AL-AgNPs exhibited significant antimicrobial activity against both Gram-positive (G+) and Gram-negative (G-) bacterial pathogens, while being non-toxic to red blood cells (RBCs), the hen's egg chorioallantoic membrane (HET-CAM), and a non-cancerous cell line (NIH3T3). Treatment with CS/AL-AgNPs significantly accelerated the healing of E. coli-infected wounds by regulating the collagen deposition and blood parameters as evidenced by in vivo experiments. Overall, these findings suggest that CS/AL-AgNPs are promising for the treatment of infected wounds.

Hemostatic and Ultrasound-Controlled Bactericidal Silk Fibroin Hydrogel via Integrating a Perfluorocarbon Nanoemulsion

Excessive blood loss and infections are the prominent risks accounting for mortality and disability associated with acute wounds. Consequently, wound dressings should encompass adequate adhesive, hemostatic, and bactericidal attributes, yet their development remains challenging. This investigation presented the benefits of incorporating a perfluorocarbon nanoemulsion (PPP NE) into a silk-fibroin (SF)-based hydrogel. By stimulating the β-sheet conformation of the SF chains, PPP NEs drastically shortened the gelation time while augmenting the elasticity, mechanical stability, and viscosity of the hydrogel. Furthermore, the integration of PPP NEs improved hemostatic competence by boosting the affinity between cells and biomacromolecules. It also endowed the hydrogel with ultrasound-controlled bactericidal ability through the inducement of inner cavitation by perfluorocarbon and reactive oxygen species (ROS) generated by the sonosensitizer protoporphyrin. Ultimately, we employed a laparotomy bleeding model and a Staphylococcus aureus-infected trauma wound to demonstrate the first-aid efficacy. Thus, our research suggested an emulsion-incorporating strategy for managing emergency wounds.

Recent advances in harnessing biological macromolecules for wound management: A review

Wound dressings (WDs) are an essential component of wound management and serve as an artificial barrier to isolate the injured site from the external environment, thereby helping to prevent exogenous infections and supporting healing. However, maintaining a moist wound environment, providing protection from infection, good biocompatibility, and allowing for gas exchange, remain a challenge in device design. Functional wound dressings (FWDs) prepared from hybrid biological macromolecule-based materials can enhance efficacy of these systems for skin wound management. This review aims to provide an overview of the state-of-the-art FWDs within the field of wound management, with a specific focus on hybrid biomaterials, techniques, and applications developed over the past five years. In addition, we highlight the incorporation of biological macromolecules in WDs, the emergence of smart WDs, and discuss the existing challenges and future prospects for the development of advanced WDs.

Sprayable Zwitterionic Antibacterial Hydrogel With High Mechanical Resilience and Robust Adhesion for Joint Wound Treatment

Wound healing in movable parts, including the joints and neck, remains a critical challenge due to frequent motions and poor flexibility of dressings, which may lead to mismatching of mechanical properties and poor fitting between dressings and wounds; thus, increasing the risk of bacterial infection. This study proposes a sprayable zwitterionic antibacterial hydrogel with outstanding flexibility and desirable adhesion. This hydrogel precursor is fabricated by combining zwitterionic sulfobetaine methacrylate (SBMA) with poly(sulfobetaine methacrylate-co-dopamine methacrylamide)-modified silver nanoparticles (PSBDA@AgNPs) through robust electrostatic interactions. About 150 s of exposure to UV light, the SBMA monomer polymerizes to form PSB chains entangled with PSBDA@AgNPs, transformed into a stable and adhesion PSB-PSB@Ag hydrogel at the wound site. The resulting hydrogel has adhesive strength (15-38 kPa), large tensile strain (>400%), suitable shape adaptation, and excellent mechanical resilience. Moreover, the hydrogel displays pH-responsive behavior; the acidic microenvironment at the infected wound sites prompts the hydrogel to rapidly release AgNPs and kill bacteria. Further, the healing effect of the hydrogel is demonstrated on the rat neck skin wound, showing improved wound closing rate due to reduced inflammation and enhanced angiogenesis. Overall, the sprayable zwitterionic antibacterial hydrogel has significant potential to promote joint skin wound healing.

A 4D Printed Adhesive, Thermo-Contractile, and Degradable Hydrogel for Diabetic Wound Healing

Chronic wound healing remains a substantial clinical challenge. Current treatments are often either prohibitively expensive or insufficient in meeting the various requirements needed for effective diabetic wound healing. A 4D printing multifunctional hydrogel dressing is reported here, which aligns perfectly with wounds owning various complex shapes and depths, promoting both wound closure and tissue regeneration. The hydrogel is prepared via digital light process (DLP) 3D printing of the mixture containing N-isopropylacrylamide (NIPAm), curcumin-loaded Pluronic F127 micelles (Cur-PF127), and poly(ethylene glycol) diacrylate-dopamine (PEGDA575-Do), a degradable crosslinker. The use of PEGDA575-Do ensures tissue adhesion and degradability, and cur-PF127 serves as an antibacterial agent. Moreover, the thermo-responsive mainchains (i.e., polymerized NIPAm) enables the activation of wound contraction by body temperature. The features of the prepared hydrogel, including robust tissue adhesion, temperature-responsive contraction, effective hemostasis, spectral antibacterial, biocompatibility, biodegradability, and inflammation regulation, contribute to accelerating diabetic wound healing in Methicillin-resistant Staphylococcus aureus (MRSA)-infected full-thickness skin defect diabetic rat models and liver injury mouse models, highlighting the potential of this customizable, mechanobiological, and inflammation-regulatory dressing to expedite wound healing in various clinical settings.

Low-impedance tissue-device interface using homogeneously conductive hydrogels chemically bonded to stretchable bioelectronics

Stretchable bioelectronics has notably contributed to the advancement of continuous health monitoring and point-of-care type health care. However, microscale nonconformal contact and locally dehydrated interface limit performance, especially in dynamic environments. Therefore, hydrogels can be a promising interfacial material for the stretchable bioelectronics due to their unique advantages including tissue-like softness, water-rich property, and biocompatibility. However, there are still practical challenges in terms of their electrical performance, material homogeneity, and monolithic integration with stretchable devices. Here, we report the synthesis of a homogeneously conductive polyacrylamide hydrogel with an exceptionally low impedance (~21 ohms) and a reasonably high conductivity (~24 S/cm) by incorporating polyaniline-decorated poly(3,4-ethylenedioxythiophene:polystyrene). We also establish robust adhesion (interfacial toughness: ~296.7 J/m2) and reliable integration between the conductive hydrogel and the stretchable device through on-device polymerization as well as covalent and hydrogen bonding. These strategies enable the fabrication of a stretchable multichannel sensor array for the high-quality on-skin impedance and pH measurements under in vitro and in vivo circumstances.

A tough bioadhesive hydrogel supports sutureless sealing of the dural membrane in porcine and ex vivo human tissue

Complete sequestration of central nervous system tissue and cerebrospinal fluid by the dural membrane is fundamental to maintaining homeostasis and proper organ function, making reconstruction of this layer an essential step during neurosurgery. Primary closure of the dura by suture repair is the current standard, despite facing technical, microenvironmental, and anatomic challenges. Here, we apply a mechanically tough hydrogel paired with a bioadhesive for intraoperative sealing of the dural membrane in rodent, porcine, and human central nervous system tissue. Tensile testing demonstrated that this dural tough adhesive (DTA) exhibited greater toughness with higher maximum stress and stretch compared with commercial sealants in aqueous environments. To evaluate the performance of DTA in the range of intracranial pressure typical of healthy and disease states, ex vivo burst pressure testing was conducted until failure after DTA or commercial sealant application on ex vivo porcine dura with a punch biopsy injury. In contrast to commercial sealants, DTA remained adhered to the porcine dura through increasing pressure up to 300 millimeters of mercury and achieved a greater maximum burst pressure. Feasibility of DTA to repair cerebrospinal fluid leak in a simulated surgical context was evaluated in postmortem human dural tissue. DTA supported effective sutureless repair of the porcine thecal sac in vivo. Biocompatibility and adhesion of DTA was maintained for up to 4 weeks in rodents after implantation. The findings suggest the potential of DTA to augment or perhaps even supplant suture repair and warrant further exploration.