A Mg2+/polydopamine composite hydrogel for the acceleration of infected wound healing

Bioactive multifunctional hydrogels accelerate burn wound healing via M2 macrophage-polarization, antioxidant and anti-inflammatory

Globally, more than 300,000 fatalities occur from burns annually, and burn-wound healing continues to present significant challenges owing to the wound's propensity for infections, heavy bleeding, poor angiogenesis, and persistent inflammatory responses. The immunomodulation of macrophage polarization toward the M2 phenotype facilitates the healing of burn wounds by controlling the tissue microenvironment and expediting the transition from the inflammatory phase to proliferation. Here, a polydopamine-mediated graphene oxide (GA), tannic acid (TA), and magnesium ion (Mg2+)-incorporated multifunctional gelatin (Gel) scaffold (GTMG) is developed to accelerate wound healing by modulating the inflammatory microenvironment of burn wounds. GA and Mg2+ confer the scaffold with the conversion of M1-type to M2-type macrophages and vascular regeneration. TA and GA synergistically provide with antimicrobial capabilities to the hydrogel. Additionally, the multifunctional hydrogel shows strong hemostatic, anti-inflammatory and biocompatible properties. Due to its strong tissue adhesion and injectability, the hydrogel can also be used for various forms of dynamic burn wounds. In vivo research shows that the hydrogel may have hemostatic, anti-inflammatory, and M2-phenotypic macrophage-polarization effects, which increase the regeneration and repair effects of burn sites and shorten the burn-healing time. The results indicate that this multifunctional hydrogel offers a promising therapeutic approach for the treatment of burn wounds by altering the immunological microenvironment and accelerating the three phases of wound healing.

Magnesium Ion/Gallic Acid MOF-Laden Multifunctional Acellular Matrix Hydrogels for Diabetic Wound Healing

The main objective for diabetic wound treatment is the design of a functional dressing that scavenges free radicals, alleviates inflammation, and is antibacterial while promoting neovascularization. Herein, a multifunctional acellular matrix hydrogel was prepared with the antimicrobial peptide jelleine-1 and a magnesium ion/gallic acid metal framework to exhibit antioxidant, anti-inflammatory, and proangiogenesis effects in diabetic wounds. The prepared hydrogel termed Gel-J-MOF efficiently released gallic acid in the acidic microenvironment of the diabetic wound, scavenged excess free radicals in vitro, and effectively reduced the levels of inflammation by regulating M2 macrophage polarization in vivo. The antimicrobial peptide jelleine-1 in the composite hydrogel effectively inhibited S. aureus and E. coli in vitro, promoting a suitable microenvironment for wound healing. In the later stage of wound healing, the composite hydrogel stimulated angiogenesis, accelerating the re-epithelialization and collagen deposition in the wound. In conclusion, this multifunctional composite hydrogel provides a regulated microenvironment for treating diabetic wounds and, therefore, has significant potential application promise in the treatment of chronic diabetic wounds.

Quaternized chitosan-based photothermal antibacterial hydrogel with pro-vascularization and on-demand degradation properties for enhanced infected wound healing

Compromised skin barrier fails to prevent pathogenic bacterial invasion, leading to wound infection and potentially severe tissue damage, for which conventional wound dressings provide inadequate therapeutic outcomes. Herein, we have developed a multifunctional injectable hydrogel (QCS-APA/P@D@C) based on quaternized chitosan (QCS) and aldehyde-modified aliphatic polycarbonate (APA), incorporating Prussian Blue (PB) @Polydopamine (PDA) @Cu (P@D@C) submicron particles (SPs). This novel hydrogel exhibits photothermal antibacterial properties, on-demand removal capability, and Cu2+-facilitated wound healing enhancement. The QCS-APA/P@D@C hydrogel, crosslinked via dynamic Schiff-base bonds, exhibits remarkable antibacterial efficacy (>99 %) against various bacteria, including multidrug-resistant (MDR) bacteria, through the synergistic effects of QCS, Cu2+, and 808 nm near-infrared (NIR) photothermal effect. The hydrogel demonstrates rapid degradation (~12 min) upon exposure to N-acetylcysteine (NAC), facilitating on-demand removal and minimizing secondary trauma during dressing changes. Furthermore, the sustained release of Cu2+ within 1-10 μM significantly enhances the migration and tube formation of human umbilical vein endothelial cells (HUVECs). In a Staphylococcus aureus (S. aureus)-infected wound model of Sprague-Dawley (SD) rats, the QCS-APA/P@D@C hydrogel demonstrated effectively modulating wound inflammation, promoting collagen deposition and angiogenesis, and accelerating wound closure. These findings demonstrate that the QCS-APA/P@D@C hydrogel can effectively promote the healing of bacterially infected wounds.

Multifunctional dynamic chitosan-guar gum nanocomposite hydrogels in infection and diabetic wound healing

Traditional wound care methods are less effective for infectious and diabetic wounds, highlighting an urgent need for effective strategies. The study aimed to design a self-healing hydrogel with antibacterial, antioxidant, and photothermal capabilities to treat infectious and diabetic wounds. Silver nanoparticles (AgNPs) were loaded into mesoporous polydopamine (MPDA) nanoparticles to form Ag@MPDA nanoparticles. Ag@MPDA was incorporated into the cationic guar gum-chitosan-boric acid (CCB) hydrogel to obtain the PA-CCB hydrogel. PA-CCB hydrogel exhibited excellent self-healing and adhesive properties, adapting well to the dynamic wound environment. PA-CCB hydrogel combined with photothermal therapy (PTT) could effectively eradicated E. coli (99.9 %) and S. aureus (99.7 %). The PA-CCB hydrogel reduced excessive reactive oxygen species and promoted the migration of fibroblasts in vitro. In the infected mouse wound models, the PA-CCB hydrogel effectively inhibited bacteria. After combining with PTT, the antibacterial ability of the PA-CCB hydrogel was further enhanced. In the diabetic mouse wound models, the PA-CCB hydrogel reduced the inflammatory level of wound tissue. In both models, after combining with PTT, the PA-CCB hydrogel exhibited further improvements in angiogenesis, collagen deposition, and re-epithelialization. By integrating multifunctional hydrogel with PTT, the PA-CCB hydrogel exhibited broad application potential for infectious and diabetic wounds.

A novel chitosan hydrogel nanocomposite, embedded with polydopamine-modified graphitic carbon nitride, for accelerating the healing process of infected wounds

The overuse of antibiotics to treat infected wounds leads to antibiotic resistance, highlighting the need for the development of non-antibiotic-dependent multifunctional biomaterials for wound healing. This study was conducted to evaluate the effects of hydrogels containing a graphite-polydopamine (PDA) carbon nitride composite (g-C₃N₄), based on marine polysaccharides (chitosan; Cit), in a mouse model of infected wounds. The formulations prepared were Chitosan/PDA (Cit/PDA), Cit/PDA/g-C₃N₄ 10 %, and Cit/PDA/g-C₃N₄ 20 %. The physicochemical properties of these structures were analyzed, and other tests confirmed their successful synthesis. In vitro antibacterial and toxicity assays were conducted and somenstrated both the safety and antibacterial activity of the hydrogels. These hydrogels were then applied for the treatment of infected wounds and showed significant potential for increasing wound contraction, decreasing total bacterial count and pathological parameters, and modulating in the expression of key biomarkers (Nrf-2, CCL-2, EGF, KGF, and COL-1 A) compared to a commercial topical antibiotic. The results showed greater wound contraction, increased antibacterial activity, and higher expression of EGF, KGF, and COL-1 A in the treated groups, particularly in the Cit/PDA/g-C₃N₄ 10 %-treated group. This hydrogel formulation showed comparable effectiveness to antibiotics in the treatment of infected wounds and also potential for clinical applications.

External stimuli-driven catalytic hydrogels for biomedical applications

Hydrogels, bearing three-dimensional networks formed through chemical or physical crosslinking of hydrophilic macromolecules, benefit from their biocompatibility, tunable properties, and high loading capacities, and thus hold great promise for biomedical applications. Recent advancements have increasingly focused on the integration of non-invasive external stimuli-such as light, heat, electricity, magnetism, and ultrasound-into hydrogel design. These external stimuli-driven catalytic hydrogels can dynamically respond to these stimuli, allowing for high spatial and temporal precision in their application. This capability enables in situ activation, controlled degradation, and catalytic reactions, making them ideal for next-generation clinical interventions. This review discusses the design strategies for external stimuli-driven catalytic hydrogels, concentrating on essential mechanisms of catalytic processes aimed at optimizing therapeutic efficacy. The discussion highlights the importance of precise control over the chemical and physical properties of hydrogels in response to specific stimuli, elucidating the regulatory mechanisms that dictate hydrogel behavior and deepening the understanding of their applications with enhanced spatial and temporal resolution.

Multifunctional Injectable Bioadhesive with Toll-like Receptor 4 and Myeloid Differentiation Factor 2 Antagonistic Anti-inflammatory Potential for Periodontal Regeneration

Effectively addressing inflammation in periodontitis is challenging as conventional injectable hydrogels typically require the addition of drugs to provide sufficient anti-inflammatory effects. To overcome this limitation, we developed a multifunctional injectable hydrogel with inherent properties that antagonize the Toll-like receptor 4 and myeloid differentiation factor 2 complex (TLR4-MD2). This hydrogel allows for direct inhibition of inflammatory pathways without the need for additional drugs. We identified xylitol, caffeic acid, and citric acid as natural materials that effectively meet biological needs for anti-inflammatory and antibacterial effects as well as support bone regeneration. With this in mind, we developed a caffeic-acid-modified poly(xylitol succinate) (PXS)-based iCPC@MgO composite hydrogel and tested its potential application for periodontal regeneration. The iCPC@MgO hydrogel demonstrated rapid wet tissue adhesion and injectability, which are ascribed to incorporating catechol groups derived from caffeic acid. Intriguingly, the PXS polymer used for synthesizing the hydrogel was found to possess anti-inflammatory properties and act as an antagonist for the TLR4-MD2 complex. This hydrogel also exhibited outstanding antibacterial efficiency against Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans by stimulating antibiotic synthesis within bacteria and disrupting bacterial cell walls. In a periodontitis mouse model, the iCPC@MgO hydrogel demonstrated the therapeutic potential of reducing inflammatory factors, inhibiting dominant periodontitis-associated bacteria, and maintaining subgingival microbiota balance in addition to the regenerative effects. These properties, combined with their ecofriendly nature, firmly established the iCPC@MgO hydrogel as a highly promising option for use in periodontitis therapy as well as in tissue healing, repair, and regeneration in various other inflammatory conditions.

Injectable dual-network hyaluronic acid nanocomposite hydrogel for prevention of postoperative breast cancer recurrence and wound healing

High locoregional recurrence rates and potential wound infections remain a significant challenge for postoperative breast cancer patients. Herein, we developed a dual-network hyaluronic acid (HA) nanocomposite hydrogel composed of herring sperm DNA (hsDNA) bridged methacrylated HA (HAMA) and FeMg-LDH-ppsa nanohybrid chelated catechol-modified HA (HADA) for the prevention of breast cancer recurrent, anti-infection, and promoting wound healing. Dynamic reversible hsDNA cross-linking combined with metal-catechol chelating renders the hydrogel injectability, rapid self-healing ability, and enhanced mechanical properties. FeMg-LDH-ppsa nanohybrids obtained by in situ polymerization of aniline derivatives in the FeMg-LDH interlayer exhibited excellent photothermal effect. Upon near-infrared (NIR) irradiation, the photothermal effect mediated by FeMg-LDH-ppsa can unwind the hsDNA duplex, enabling the controlled release of preloaded DOX for synergistic photothermal-chemotherapy antitumor. Meanwhile, the catechol-metal (Fe3+/Mg2+) moieties in the hydrogel enhanced tissue adhesion and exhibited intrinsic antimicrobial and bioactive properties, which in combination with the NIR-assisted photothermal effect, significantly accelerated infected wound healing through sterilizing microorganisms, alleviating inflammation, re-epithelialization, and angiogenesis. Overall, this multifunctional hydrogel represented a promising candidate in postoperative wound management for simultaneous tumor elimination, antiinfection, and wound repair.

Engineering Surface-Adaptive Metal-Organic Framework Armor to Promote Infected Wound Healing

Metal-organic frameworks (MOFs) hold enormous promise for treating bacterial infections to circumvent the threat of antibiotic resistance. However, positioning MOFs on wound dressings is hindered and remains a significant challenge. Herein, a facile heterointerfacial engineering strategy was developed to tailor the "MOF armor" that adaptively weaponized the poly(ε-caprolactone) electrospun dressing with excellent bacteria-killing efficacy. Hydrophilic epitaxial crystallization to enhance the interfacial wettability is the key to induce the uniform seeding of Cu2+ and thus to generate a compact MOF layer on the electrospun dressing. The universality of the proposed strategy was demonstrated by the construction of different kinds of MOFs (HKUST-1, ZIF-8, and ZIF-67) on variously shaped substrates (nanofibers, pellets, plates, and 3D-printed porous scaffolds). By optimizing the Cu2+ loading, the Cu-MOF armor exhibited sustained ion release behavior, strong antibacterial activity, and good biocompatibility. In vivo rat model revealed that the Cu-MOF armor significantly promoted infected wound healing by inhibiting inflammatory factors, promoting collagen deposition, and angiogenesis. This unique MOF armor provides an appealing and effective solution for designing and fabricating advanced wound dressings.

Advancements in GelMA bioactive hydrogels: Strategies for infection control and bone tissue regeneration

Infectious bone defects present a significant clinical challenge, characterized by infection, inflammation, and subsequent bone tissue destruction. Traditional treatments, including antibiotic therapy, surgical debridement, and bone grafting, often fail to address these defects effectively. However, recent advancements in biomaterials research have introduced innovative solutions for managing infectious bone defects. GelMA, a three-dimensional network of hydrophilic polymers that can absorb and retain substantial amounts of water, has attracted considerable attention in the fields of materials science and biomedical engineering. Its distinctive properties, such as biocompatibility, responsiveness to stimuli, and customisable mechanical characteristics make GelMA an exemplary scaffold material for bone tissue engineering. This review aims to thoroughly explore the current literature on antibacterial and osteogenic strategies using GelMA hydrogels for the restoration of infected bones. It discusses their fabrication methods, biocompatibility, antibacterial effectiveness, and bioactivity. We conclude by discussing the existing challenges and future research directions in this field, with the hope of inspiring further innovations in the synthesis, modification, and application of GelMA-based hydrogels for infection control and bone tissue regeneration.

Design Strategy, On-Demand Control, and Biomedical Engineering Applications of Wet Adhesion

The adhesion of tissues to external devices is fundamental to numerous critical applications in biomedical engineering, including tissue and organ repair, bioelectronic interfaces, adhesive robotics, wearable electronics, biomedical sensing and actuation, as well as medical monitoring, treatment, and healthcare. A key challenge in this context is that tissues are typically situated in aqueous and dynamic environments, which poses a bottleneck to further advancements in these fields. Wet adhesion technology (WAT) presents an effective solution to this issue. In this review, we summarize the three major design strategies and control methods of wet adhesion, comprehensively and systematically introducing the latest applications and advancements of WAT in the field of biomedical engineering. First, single adhesion mechanism under the frameworks of the three design strategies is systematically introduced. Second, control methods for adhesion are comprehensively summarized, including spatiotemporal control, detachment control, and reversible adhesion control. Third, a systematic summary and discussion of the latest applications of WAT in biomedical engineering research and education were presented, with a particular focus on innovative applications such as tissue-electronic interface devices, ingestible devices, end-effector components, in vivo medical microrobots, and medical instruments and equipment. Finally, opportunities and challenges encountered in the design and development of wet adhesives with advanced adhesive performance and application prospects are discussed.

Nanomaterials at the forefront of antimicrobial therapy by photodynamic and photothermal strategies

In the face of the increasing resistance of microorganisms to traditional antibiotics, the development of innovative treatment methods is becoming increasingly urgent. Nanophototherapy technology can precisely target the infected area and achieve synergistic antibacterial effects in multiple modes. This phototherapy method has shown significant efficacy in treating diseases caused by drug-resistant bacteria, especially in the elimination of biofilms, where it has demonstrated strong dissolution capabilities. PTT utilizes photothermal agents to convert near-infrared light into heat, effectively killing bacteria and promoting tissue regeneration. Similarly, PDT utilizes photosensitizers, which produce reactive oxygen species (ROS) when activated by light, destroying the structure and function of bacterial cells. This review summarizes photothermal agents and photosensitizers used for antibacterial purposes. In conducting our literature review, we employed a systematic approach to ensure a comprehensive and representative selection of studies. Additionally, this article explores the potential of phototherapy in regulating wound microenvironments, promoting wound healing, and activating the immune system. Nanophototherapeutic materials show great potential for application in antibacterial treatment and are expected to provide innovative solutions for drug-resistant bacterial infections that traditional antibiotics are struggling to address.

Crocin-1 laden thermosensitive chitosan-based hydrogel with smart anti-inflammatory performance for severe full-thickness burn wound therapeutics

Burns are the fourth most common type of civilian trauma worldwide, and the management of severe irregular scald wounds remains a significant challenge. Herein, crocin-1 laden hydroxybutyl chitosan (CRO-HBC) thermosensitive hydrogel with smart anti-inflammatory performance was developed for accelerating full-thickness burn healing. The injectable and shape adaptability of the CRO-HBC gel make it a promising candidate for effectively filling scald wounds with irregular shapes, while simultaneously providing protection against external pathogens. The CRO-HBC gel network formed by hydrophobic interactions exhibited an initial burst release of crocin-1, followed by a gradual and sustained release over time. The excessive release of ROS and pro-inflammatory cytokines should be effectively regulated in the early stage of wound healing. The controlled release of crocin-1 from the CRO-HBC gel adequately addresses this requirement for wound healing. The CRO-HBC hydrogel also exhibited an excellent biocompatibility, an appropriate biodegradability, keratinocyte migration facilitation properties, and a reactive oxygen species scavenging capability. The composite CRO-HBC hydrogel intelligently mitigated inflammatory responses, promoted angiogenesis, and exhibited a commendable efficacy for tissue regeneration in a full-thickness scalding model. Overall, this innovative temperature-sensitive CRO-HBC injectable hydrogel dressing with smart anti-inflammatory performance has enormous potential for managing severe scald wounds.

Intelligent bacteria-targeting ZIF-8 composite for fluorescence imaging-guided photodynamic therapy of drug-resistant superbug infections and burn wound healing

Infected burn wounds are characterized by persistent drug-resistant bacterial infection coupled with an inflammatory response, impeding the wound-healing process. In this study, an intelligent nanoparticle system (CCM+TTD@ZIF-8 NPs) was prepared using curcumin (CCM), an aggregation-induced emission luminogens (TTD), and ZIF-8 for infection-induced wound healing. The CCM+TTD@ZIF-8 NPs showed multiple functions, including bacteria targeting, fluorescence imaging and pH response-guided photodynamic therapy (PDT), and anti-inflammatory. The positive charges of ZIF-8 NPs allowed the targeting of drug-resistant bacteria in infected wounds, thereby realizing fluorescence imaging of bacteria by emitting red fluorescence at the infected site upon blue light irradiation. The pH-responsive characteristics of the CCM+TTD@ZIF-8 NPs also enabled controllable CCM release onto the infected wound site, thereby promoting the specific accumulation of ROS at the infected site, with outstanding bactericidal efficacy against drug-resistant Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) strains in vitro/in vivo. Additionally, due to the excellent bactericidal effect and anti-inflammatory properties of CCM+TTD@ZIF-8 NPs combined with blue light irradiation, the regeneration of epidermal tissue, angiogenesis, and collagen deposition was achieved, accelerating the healing process of infected burn wounds. Therefore, this CCM+TTD@ZIF-8 NPs with multifunctional properties provides great potential for infected burn wound healing.

Photothermal enhanced antibacterial chitosan-based polydopamine composite hydrogel for hemostasis and burn wound repairing

Bleeding and bacterial infection are common problems associated with wound treatment, while effective blood clotting and vessel regeneration promotion are the primary considerations to design the wound dressing materials. This research presents a chitosan-based hydrogel with grafted quaternary ammonium and polyphosphate (QCSP hydrogel) as the antibacterial hemostatic dressing to achieve burn wound treatment. The tissue adhesion of the hydrogel sealed the blood flow and the polyphosphate grafted to the chitosan promoted the activation of coagulation factor V to enhance the hemostasis. At the same time, the grafted quaternary ammonium enhanced the antibacterial ability of the biodegradable hydrogel wound dressing. In addition, the polydopamine as a photothermal agent was composited into the hydrogel to enhance the antibacterial and reactive oxygen scavenging performance. The in vivo hemostasis experiment proved the polyphosphate enhanced the coagulation property. Moreover, this photothermal property of the composite hydrogel enhanced the burn wound repairing rate combined with the NIR stimulus. As a result, this hydrogel could have potential application in clinic as dressing material for hemostasis and infection prone would repairing.

The Core-Shell Microneedle with Probiotic Extracellular Vesicles for Infected Wound Healing and Microbial Homeostasis Restoration

Wound healing is a dynamic process involving the timely transition of organized phases. However, infected wounds often experience prolonged inflammation due to microbial overload. Thus, addressing the viable treatment needs across different healing stages is a critical challenge in wound management. Herein, a novel core-shell microneedle (CSMN) patch is designed for the sequential delivery of tannic acid-magnesium (TA-Mg) complexes and extracellular vesicles from Lactobacillus druckerii (LDEVs). Upon application to infected sites, CSMN@TA-Mg/LDEV releases TA-Mg first to counteract pathogenic overload and reduce reactive oxygen species (ROS), aiding the transition to proliferative phase. Subsequently, the sustained release of LDEVs enhances the activities of keratinocytes and fibroblasts, promotes vascularization, and modulates the collagen deposition. Notably, dynamic track of microbial composition demonstrates that CSMN@TA-Mg/LDEV can both inhibit the aggressive pathogen and increase the microbial diversity at wound sites. Functional analysis further highlights the potential of CSMN@TA-Mg/LDEV in facilitating wound healing and skin barrier restoration. Moreover, it is confirmed that CSMN@TA-Mg/LDEV can accelerate wound closure and improve post-recovery skin quality in the murine infected wound. Conclusively, this innovative CSMN patch offers a rapid and high-quality alternative treatment for infected wounds and emphasizes the significance of microbial homeostasis.

α-Amylase and polydopamine@polypyrrole-based hydrogel microneedles promote wound healing by eliminating bacterial infection

In this paper, we designed a novel "Freeze-thaw" type hydrogel microneedle (PP-CDLut-AMY MN). The "Freeze-thaw" cycle endows the MN excellent water absorption, with a dissolution rate of up to 486 %. The addition of polydopamine@polypyrrole (PP) enabled the MN to have a stable temperature increase to approximately 50 °C under near-infrared light irradiation, which exhibited killing rates of 99 % and 98 % against free S. aureus and E. coli, respectively. Natural macromolecule α-Amylase (AMY) was used as a bacterial biofilm disintegrator, and the destruction rate of S. aureus biofilm reached 83.2 %. Meanwhile, the incorporation of Hydroxypropyl-β-cyclodextrin @Luteolin (CDLut) provided the MN with good antioxidant properties, which could scavenge 73.35 % of DPPH free radicals. In vivo experiments have shown that the MN can effectively promote the healing of wounds infected by S. aureus biofilm and that the stable and gentle photothermal effect did not cause unnecessary damage to the surrounding tissues. We believe that this novel hydrogel MN has great potential to combat bacterial biofilms associated with wound infections.

Carbonized Polymer Dot-Tannic Acid Nanoglue: Tissue Reinforcement with Concurrent Fluorescent Tracking, Insulin Delivery, and Reactive Oxygen Species Regulation for Normal and Diabetic Wound Healing

Nanotizing biosealant components offer a multitude of chemical functionalities for superior adhesion-cohesion, delivering unique properties for comprehensive wound healing that are otherwise impossible to achieve using commercial variants. For the first time, a two-step controlled hydrothermal pyrolysis is reported to nanotize dopamine, phloroglucinol, and glutaraldehyde into carbon dot (CD) to be subsequently converted into carbonized polymer dot (CPD) with gelatin as a co-substrate. Chemical crosslinking of CD with gelatin through Schiff base formation before the second pyrolysis step ensures a complex yet porous polymeric network. The retention of chemical functionalities indigenous to CD substrates and gelatin along with the preservation of CD photoluminescence in CPD for optical tracking is achieved. A unique nanoformulation is created with the CPD through tannic acid (TA) grafting evolving CPD-TA nanoglue demonstrating ≈1.32 MPa strength in lap shear tests conducted on porcine skin, surpassing traditional bioadhesives. CPD-TA nanoglue uploaded insulin as chosen cargo disbursal at the wound site for healing normal and in vitro diabetic wound models using HEKa cells with extraordinary biocompatibility. Most importantly, CPD-TA can generate reactive oxygen species (ROS) and scavenge simultaneously under ambient conditions (23 W white LED or dark) for on-demand sterilization or aiding wound recovery through ROS scavenging.

Polyphenol-mediated hyaluronic acid/tannic acid hydrogel with short gelation time and high adhesion strength for accelerating wound healing

Wound healing is a complex process involving a complicated interplay between numerous cell types and vascular systems. Hyaluronic acid (HA)-based hydrogel facilitates wound healing, and is involved in all processes. However, slow gelation speed and weak adhesion strength limit its ability to form a stable physical barrier quickly. Herein, we propose a HA-based composite hydrogel as the wound dressing based on oxidative coupling reaction. Tannic acid and dopamine-coated carbon particles (DCPs) containing abundant phenolic hydroxyl groups are incorporated into the HA-based hydrogel for increasing the number of crosslinking sites of oxidative coupling of the hydrogel and enhancing adhesion through the formation of covalent bonds and hydrogen bonds between hydrogel and wound sites. The composite hydrogel exhibits short gelation time (<6 s) and high adhesion strength (>8.1 kPa), which are superior to the references and commercial products of its kind. The in vitro experiments demonstrate that the hydrogel has low hemolytic reaction, negligible cytotoxicity, and the ability to promote fibroblast proliferation and migration. The in vivo full-thickness skin defect model experiments demonstrate that the hydrogel can accelerate wound healing under mild photothermal stimulation of DCPs by reducing inflammation, relieving tissue hypoxia, and promoting angiogenesis and epithelialization.

Cu2O-SnO2-PDA heterozygous nanozyme doped hydrogel mediated conglutinant microenvironment regulation for wound healing therapy

Bacterial infection significantly hinders the wound healing process. Overuse of antibiotics has led to the rise of drug resistance in bacteria, making the development of smart medical dressings that promote wound healing without antibiotics, a critical need. In this study, Cu₂O-SnO₂-PDA (PCS) nanoenzymes with Fenton-like activity and high photothermal conversion efficiency were developed. These nanoenzymes were then incorporated into a hydrogel through cross-linking of acrylamide (AM) and N-[Tris-(hydroxymethyl)methyl] acrylamide (THMA), forming a tough, highly-adhesive, and self-healing composite hydrogel (AT/PCS) with antimicrobial properties. The AT/PCS hydrogel exhibits excellent mechanical strength and adhesion, facilitating increased oxygen levels and strong adherence to the wound site. Moreover, it effectively regulates the wound microenvironment by combining synergistic chemodynamic therapy (CDT) and photothermal therapy (PTT) for antibacterial treatment. The AT/PCS hydrogel enhances collagen deposition and expedites wound healing in a rat model, largely due to its potent antibacterial properties.

Diphasic CeO2 Nanocrystal/Bioactive Glass Nanosphere-Based Composite Hydrogel for Diabetic Wound Healing by Reactive Oxygen Species Scavenging and Inflammation Regulation

Background: Antioxidant therapy aimed at reducing excessive local oxidative stress is one of the most important strategies for promoting diabetic wound repair. The reversible transformation of Ce3+/Ce4+ in ceria (CeO2) can reduce excessive local oxidative stress. However, inducing angiogenesis, local anti-inflammatory effects, and other positive effects are challenging. Therefore, ideal dressings for chronic diabetic wound management must concurrently reduce excessive oxidative stress, promote angiogenesis, and have anti-inflammatory effects. Methods: In this study, Ce-doped borosilicate bioactive glasses (BGs) were prepared using the sol-gel method, and CeO2 nanocrystals (CeO2-NCs) were precipitated on the glass surface by heat treatment to obtain BG-xCe composite glass nanospheres. Subsequently, nanospheres were modified by amino group and combined with dopamine and acrylamide to obtain BG-xCe/polydopamine/polyacrylamide (PDA/PAM) composite hydrogel. Then, the morphology and properties of composite hydrogels were detected, and the properties to treat the diabetic wounds were also evaluated. Results: The results demonstrated that the BG-10Ce/PDA/PAM composite hydrogel possessed excellent tensile and adhesive properties. In vitro, the migration and angiogenesis of human umbilical vein endothelial cells (HUVECs) and fibroblasts (L929) were enhanced by reducing reactive oxygen species (ROS) levels in the conditioned medium. Animal experiments have shown that CeO2-NCs in hydrogels effectively scavenge ROS in diabetic wounds, and Sr dissolved from the glassy phase can modulate macrophage polarization to the M2 phenotype. Conclusions: The synergistic effect of both amorphous materials and nanocrystals provides the BG-10Ce/PDA/PAM composite hydrogel with great potential for diabetic wound healing.

Green synthesis-inspired antibacterial, antioxidant and adhesive hydrogels with ultra-fast gelation and hemostasis for promoting infected skin wound healing

Bacterial infections are a serious threat to wound healing and skin regeneration. In recent years, photothermal therapy (PTT) has become one of the most promising tools in the treatment of infectious diseases. However, wound dressings with photo-responsive properties are currently still limited by the difficulties of biosafety and thermal stability brought by the introduction of photosensitizers or photothermal agents. Therefore, how to improve the therapeutic efficiency and biosafety from material design is still a major challenge at present. In this study, the carboxymethyl chitosan (CMCS) and protocatechuic aldehyde (PA) hydrogels based on horseradish peroxidase (HRP) and hydrogen peroxide (H2O2) enzymatic catalysis was developed. Therein, HRP and H2O2 catalyzed cross-linking while polymerizing PA, which not only endowed the hydrogels with photothermal responsiveness but also with good biosafety through this enzyme-catalyzed green approach. Meanwhile, the hydrogels possessed highly efficient bacteriostatic ability with the assistance of near infrared (NIR). Moreover, the ultra-rapid gelation, strong tissue adhesion, high swelling ability, good antioxidant property and hemostatic property of the CMCS-PA hydrogels based on HRP/H2O2 enzymatic catalysis were suitable for the treatment of skin wounds. Meanwhile, NIR-assistant CMCS-PA hydrogels based on HRP/H2O2 enzymatic catalysis reduced inflammation, decreased bacterial infection, and promoted collagen deposition and angiogenesis, which showed remarkable therapeutic effects in a skin wound infection model. All results indicate that this green approach to introduce photothermal property by HRP-catalyzed PA polymerization endows the hydrogels with efficient photothermal conversion efficiency, suggesting that they are promising to provide new options for replacing photothermal agents and photosensitizers. STATEMENT OF SIGNIFICANCE: In recent years, wound dressings with photo-responsive properties are currently still limited by the difficulties of biosafety and thermal stability brought by the introduction of agent photosensitizers or photothermal agents. In this study, the carboxymethyl chitosan and protocatechuic aldehyde hydrogels based on horseradish peroxidase and hydrogen peroxide enzymatic catalysis was developed. The photothermal properties of hydrogels were transformed from absent to present just by horseradish peroxidase-catalyzed protocatechuic aldehyde polymerization in a green approach. Meanwhile, the hydrogels possessed highly efficient bacteriostatic ability with the assistance of near infrared. The green approach of introducing photothermal properties from material design solves the biosafety challenge. Therefore, this study is expected to provide new options for alternative photothermal agents and photosensitizers.

Bioinspired wet adhesive carboxymethyl cellulose-based hydrogel with rapid shape adaptability and antioxidant activity for diabetic wound repair

Currently, adhesive hydrogels have shown promising effect in chronic diabetic wound repair. However, there are issues and challenges in treating diabetic wounds due to inadequate wet adhesion, unable to fill irregular and deep wounds, and oxidative stress. Herein, a mussel-inspired naturally hydrogel dressing with rapid shape adaptability, wet adhesion and antioxidant abilities for irregular, deep and frequently movement diabetic wounds repair was constructed by comprising catechol modified carboxymethyl cellulose (CMC-DA) and tannic acid. Benefiting from the reversible hydrogen bonding, the resulting hydrogels exhibited injectability, remarkable self-healing ability, rapid shape adaptability and strong tissue adhesion (45.9 kPa), thereby contributing to self-adaptive irregular-shaped wounds or moving joint parts. Especially, the adhesion strength of the hydrogel on wet tissue still remained at 14.9 kPa. Besides, the hydrogels could be easily detached from the skin by ice-cooling that avoided secondary damage caused by dressing change. Remarkably, the hydrogels possessed excellent antioxidant, satisfactory biocompatibility, efficient hemostasis and antibacterial properties. The in vivo evaluation further demonstrated that the hydrogel possessed considerable wound-healing promotion effect by regulating diabetic microenvironment, attributed to that the hydrogel could significantly reduce inflammatory response, alleviate oxidative stress and regulate neovascularization. Overall, this biosafe adhesive hydrogel had great potentials for diabetic wound management.

A multifunctional thermosensitive hydrogel based on phototherapy for promoting the healing of dental extraction wounds

Post-extraction wound infections are a common complication of dental extractions. More specifically, infection in the alveolar socket after tooth extraction accelerates the resorption and destruction of the alveolar bone, and ultimately affects the final restoration results. Currently, the main clinical treatment approaches applied to the socket after tooth extraction include mechanical wound debridement, chemical rinses (e.g., chlorhexidine), filling of the extraction socket with absorbent gelatin sponges, and the systemic application of antibiotics. However, these traditional treatment modalities have some limitations and their therapeutic effects are unsatisfactory. In this study, a phototherapeutic temperature-sensitive hydrogel material was constructed for injection using a tea polyphenol (TP)-modified poly-N-isopropylacrylamide (PNIPAM) hydrogel skeleton loaded with the photosensitiser indocyanine green (ICG). The resulting PNIPAM-TP/ICG system exhibited an excellent injectability and temperature-sensitive properties. In addition, it stopped haemorrhaging and acted as a wound astringent. The hydrogel steadily released ICG into the oral environment to exert photothermal/photodynamic effects along with synergistic antibacterial and anti-inflammatory properties when combined with tea polyphenols. In vivo experiments demonstrated that the application of PNIPAM-TP/ICG to infected dental extraction wounds in rats rapidly stopped the bleeding and accelerated wound healing. Overall, this study describes a drug-loaded, temperature-sensitive hydrogel for the treatment of open wound infections, and shows promise as a reference for the treatment of tooth extraction wounds.

Continuous and Controllable Preparation of Sodium Alginate Hydrogel Tubes Guided by the Soft Cap Inspired by the Apical Growth of the Plant

Hydrogel tubes made of sodium alginate (SA) have potential applications in drug delivery, soft robots, biomimetic blood vessels, tissue stents, and other fields. However, the continuous preparation of hollow SA hydrogel tubes with good stability and size control remains a huge challenge for chemists, material scientists, and medical practitioners. Inspired by the plant apical growth strategy, a new method named soft cap-guided growth was proposed to produce SA hydrogel tubes. Due to the introduction of inert low gravity substances, such as air and heptane, into the extrusion needle in front of calcium chloride solution to form a soft cap, the SA hydrogel tubes with controllable sizes were fabricated rapidly and continuously without using a template through a negative gravitropism mechanism. The SA hydrogel tubes had good tensile strength, high burst pressure, and good cell compatibility. In addition, hydrogel tubes with complex patterns were conveniently created by controlling the motion path of a soft cap, such as a rotating SA bath or magnetic force. Our research provided a simple innovative technique to steer the growth of hydrogel tubes, which made it possible to mass produce hydrogel tubes with controllable sizes and programmable patterns.

Electrospray Nano-Micro Composite Sodium Alginate Microspheres with Shape-Adaptive, Antibacterial, and Angiogenic Abilities for Infected Wound Healing

Nonhealing infectious wounds, characterized by bacterial colonization, wound microenvironment destruction, and shape complexity, present an intractable problem in clinical practice. Inspired by LEGOs, building-block toys that can be assembled into desired shapes, we proposed the use of electrospray nano-micro composite sodium alginate (SA) microspheres with antibacterial and angiogenic properties to fill irregularly shaped wounds instantly. Specifically, porous poly(lactic-co-glycolic acid) (PLGA) microspheres (MSs) encapsulating basic fibroblast growth factor (bFGF) were produced by a water-in-oil-in-water double-emulsion method. Then, bFGF@MSs were blended with the SA solution containing ZIF-8 nanoparticles. The resultant solution was electrosprayed to obtain nano-micro composite microspheres (bFGF@MS/ZIF-8@SAMSs). The composite MSs' size could be regulated by PLGA MS mass proportion and electrospray voltage. Moreover, bFGF, a potent angiogenic agent, and ZIF-8, bactericidal nanoparticles, were found to release from bFGF@MS/ZIF-8@SAMSs in a controlled and sustainable manner, which promoted cell proliferation, migration, and tube formation and killed bacteria. Through experimentation on rat models, bFGF@MS/ZIF-8@SAMSs were revealed to adapt to wound shapes and accelerate infected wound healing because of the synergistic effects of antibacterial and angiogenic abilities. In summation, this study developed a feasible approach to prepare bioactive nano-micro MSs as building blocks that can fill irregularly shaped infected wounds and improve healing.

Facile fabrication of chitosan/hyaluronic acid hydrogel-based wound closure material Co-loaded with gold nanoparticles and fibroblast growth factor to improve anti-microbial and healing efficiency in diabetic wound healing and nursing care

Generally, diabetic wounds heal very slowly and inefficiently with an increasing risk of infections. Recent nanotechnology and biomaterial advances elaborate developed multi-functional hydrogels and nanoparticles offer promising solutions to accelerate wound healing for diabetic patients. This research work demonstrates to use of solvent diffusion method to develop hydrogel nanocomposites composed of chitosan (CS), hyaluronic acid (HA), gold (Au), and fibroblast growth factors (FGF). The biological analysis of nanocomposites exhibited enhanced wound healing efficiency by incorporating bioactive molecules like FGF and bioactive Au nanoparticles. In vitro, cell compatibility analysis (MTT assay) of prepared hydrogel nanocomposites was studied on fibroblast cell lines NIH-3T3-L1 and L929 and exhibited greater cell survival ability (>90 %), cell proliferation and migration ability, which demonstrated the suitability of nanocomposite for wound healing treatment. In vitro, anti-bacterial analyses established that FGF-Au@CS/HA has strong antibacterial effectiveness against gram-positive and gram-negative pathogens. The observation of the present research revealed that prepared FGF-Au@CS/HA hydrogel composites could be a suitable biomaterial for diabetic wound care, potentially improving its antibacterial and healing efficacies.

Composite Aerogel Scaffolds Containing Flexible Silica Nanofiber and Tricalcium Phosphate Enable Skin Regeneration

Poor hemostatic ability and less vascularization at the injury site could hinder wound healing as well as adversely affect the quality of life (QOL). An ideal wound dressing should exhibit certain characteristics: (a) good hemostatic ability, (b) rapid wound healing, and (c) skin appendage formation. This necessitates the advent of innovative dressings to facilitate skin regeneration. Therapeutic ions, such as silicon ions (Si4+) and calcium ions (Ca2+), have been shown to assist in wound repair. The Si4+ released from silica (SiO2) can upregulate the expression of proteins, including the vascular endothelial growth factor (VEGF) and alpha smooth muscle actin (α-SMA), which is conducive to vascularization; Ca2+ released from tricalcium phosphate (TCP) can promote the coagulation alongside upregulating the expression of cell migration and cell differentiation related proteins, thereby facilitating the wound repair. The overarching objective of this study was to exploit short SiO2 nanofibers along with the TCP to prepare TCPx@SSF aerogels and assess their wound healing ability. Short SiO2 nanofibers were prepared by electrospinning and blended with varying proportions of TCP to afford TCPx@SSF aerogel scaffolds. The TCPx@SSF aerogels exhibited good cytocompatibility in a subcutaneous implantation model and manifested a rapid hemostatic effect (hemostatic time 75 s) in a liver trauma model in the rabbit. These aerogel scaffolds also promoted skin regeneration and exhibited rapid wound closure, epithelial tissue regeneration, and collagen deposition. Taken together, TCPx@SSF aerogels may be valuable for wound healing.

In situ light-activated materials for skin wound healing and repair: A narrative review

Dermal wounds are a major global health burden made worse by common comorbidities such as diabetes and infection. Appropriate wound closure relies on a highly coordinated series of cellular events, ultimately bridging tissue gaps and regenerating normal physiological structures. Wound dressings are an important component of wound care management, providing a barrier against external insults while preserving the active reparative processes underway within the wound bed. The development of wound dressings with biomaterial constituents has become an attractive design strategy due to the varied functions intrinsic in biological polymers, such as cell instructiveness, growth factor binding, antimicrobial properties, and tissue integration. Using photosensitive agents to generate crosslinked or photopolymerized dressings in situ provides an opportunity to develop dressings rapidly within the wound bed, facilitating robust adhesion to the wound bed for greater barrier protection and adaptation to irregular wound shapes. Despite the popularity of this fabrication approach, relatively few experimental wound dressings have undergone preclinical translation into animal models, limiting the overall integrity of assessing their potential as effective wound dressings. Here, we provide an up-to-date narrative review of reported photoinitiator- and wavelength-guided design strategies for in situ light activation of biomaterial dressings that have been evaluated in preclinical wound healing models.

Photothermal hydrogels for infection control and tissue regeneration

In this review, we report investigating photothermal hydrogels, innovative biomedical materials designed for infection control and tissue regeneration. These hydrogels exhibit responsiveness to near-infrared (NIR) stimulation, altering their structure and properties, which is pivotal for medical applications. Photothermal hydrogels have emerged as a significant advancement in medical materials, harnessing photothermal agents (PTAs) to respond to NIR light. This responsiveness is crucial for controlling infections and promoting tissue healing. We discuss three construction methods for preparing photothermal hydrogels, emphasizing their design and synthesis, which incorporate PTAs to achieve the desired photothermal effects. The application of these hydrogels demonstrates enhanced infection control and tissue regeneration, supported by their unique photothermal properties. Although research progress in photothermal hydrogels is promising, challenges remain. We address these issues and explore future directions to enhance their therapeutic potential.

Hydrogel Loaded with Peptide-Containing Nanocomplexes: Symphonic Cooperation of Photothermal Antimicrobial Nanoparticles and Prohealing Peptides for the Treatment of Infected Wounds

Current treatment for chronic infectious wounds is limited due to severe drug resistance in certain bacteria. Therefore, the development of new composite hydrogels with nonantibiotic antibacterial and pro-wound repair is important. Here, we present a photothermal antibacterial composite hydrogel fabricated with a coating of Fe2+ cross-linked carboxymethyl chitosan (FeCMCS) following the incorporation of melanin nanoparticles (MNPs) and the CyRL-QN15 peptide. Various physical and photothermal properties of the hydrogel were characterized. Cell proliferation, migration, cycle, and free-radical scavenging activity were assessed, and the antimicrobial properties of the hydrogel were probed by photothermal therapy. The effects of the hydrogel were validated in a model of methicillin-resistant Staphylococcus aureus (MRSA) infection with full-thickness injury. This effect was further confirmed by changes in cytokines associated with inflammation, re-epithelialization, and angiogenesis on the seventh day after wound formation. The MNPs demonstrated robust photothermal conversion capabilities. The composite hydrogel (MNPs/CyRL-QN15/FeCMCS) promoted keratinocyte and fibroblast proliferation and migration while exhibiting high antibacterial efficacy, effectively killing more than 95% of Gram-positive and Gram-negative bacteria. In vivo study using an MRSA-infected full-thickness injury model demonstrated good therapeutic efficacy of the hydrogel in promoting regeneration and remodeling of chronically infected wounds by alleviating inflammatory response and accelerating re-epithelialization and collagen deposition. The MNPs/CyRL-QN15/FeCMCS hydrogel showed excellent antibacterial and prohealing effects on infected wounds, indicating potential as a promising candidate for wound healing promotion.

MgO@polydopamine Nanoparticle-Loaded Photothermal Microneedle Patches Combined with Chitosan Gel Dressings for the Treatment of Infectious Wounds

As for wound drug delivery, microneedles (MNs) have attracted wide attention. However, while effective at increasing the depth of drug delivery, traditional MNs often have limited drug loads and have difficulty penetrating scabs on wounds. Herein, we develop a drug delivery system combining MgO@polydopamine (MgO@PDA) nanoparticle-loaded photothermal MN patches and chitosan (CS) gel to inhibit the formation of scabs and deliver sufficient drugs into deep tissue. When inserted into the wound, the MN system can keep the wound bed moist and weakly acidic to inhibit the formation of scabs and accelerate wound closure. The released MgO@PDA nanoparticles from both the tips and the backing layer, which immensely increase the drug load, continuously release Mg2+ in the moist, weakly acidic wound bed, promoting tissue migration and the formation of microvessels. MgO@PDA nanoparticles show excellent antibacterial activity under near-infrared irradiation synergized with the CS gel, and the PDA coating can also overcome the adverse effects of oxidative stress. Through in vitro and in vivo experiments, the MN system showed remarkable antibacterial, antioxidant, anti-inflammatory, and pro-angiogenic effects, indicating its potential in the treatment of infectious wounds.

Progress of polysaccharide-based tissue adhesives

Recently, polymer-based tissue adhesives (TAs) have gained the attention of scientists and industries as alternatives to sutures for sealing and closing wounds or incisions because of their ease of use, low cost, minimal tissue damage, and short application time. However, poor mechanical properties and weak adhesion strength limit the application of TAs, although numerous studies have attempted to develop new TAs with enhanced performance. Therefore, next-generation TAs with improved multifunctional properties are required. In this review, we address the requirements of polymeric TAs, adhesive characteristics, adhesion strength assessment methods, adhesion mechanisms, applications, advantages and disadvantages, and commercial products of polysaccharide (PS)-based TAs, including chitosan (CS), alginate (AL), dextran (DE), and hyaluronic acid (HA). Additionally, future perspectives are discussed.

Atomically dispersed nanozyme-based synergistic mild photothermal/nanocatalytic therapy for eradicating multidrug-resistant bacteria and accelerating infected wound healing

Constructing a synergistic multiple-modal antibacterial platform for multi-drug-resistant (MDR) bacterial eradication and effective treatment of infected wounds remains an important and challenging goal. Herein, we developed a multifunctional Cu/Mn dual single-atom nanozyme (Cu/Mn-DSAzymes)-based synergistic mild photothermal/nanocatalytic-therapy for a MDR bacterium-infected wound. Cu/Mn-DSAzymes with collaborative effects exhibit remarkable dual CAT-like and OXD-like enzyme activities and could efficiently catalyze cascade enzymatic reactions with a low level of H2O2 as an initial reactant to produce reparative O2 and lethal ˙O2-. Moreover, a black N-doped carbon nanosheet supports of Cu/Mn-DSAzymes show superior NIR-II-triggered photothermal performance, endowing them with photothermal-enhanced dual enzyme catalysis. In addition, such enhanced dual enzyme catalysis likely improves the susceptibility and lethality of photothermal effects on MDR bacteria. In vitro and in vivo studies demonstrate that Cu/Mn-DSAzyme-mediated synergistic nanocatalytic and photothermal effects possess dramatic antibacterial outcomes against MDR bacteria and evidently reduced inflammation at wound sites. Moreover, the combined photothermal effect and O2 release mediated by Cu/Mn-DSAzymes promotes macrophage polarization to reparative M2 phenotype, collagen deposition, and angiogenesis, considerably accelerating wound healing. Therefore, Cu/Mn-DSAzyme-based synergetic dual-modal antibacterial therapy is a promising strategy for MDR bacterium-infected wound treatment, owing to their excellent antibacterial ability and significant tissue remodeling effects.

Construction methods and biomedical applications of PVA-based hydrogels

Polyvinyl alcohol (PVA) hydrogel is favored by researchers due to its good biocompatibility, high mechanical strength, low friction coefficient, and suitable water content. The widely distributed hydroxyl side chains on the PVA molecule allow the hydrogels to be branched with various functional groups. By improving the synthesis method and changing the hydrogel structure, PVA-based hydrogels can obtain excellent cytocompatibility, flexibility, electrical conductivity, viscoelasticity, and antimicrobial properties, representing a good candidate for articular cartilage restoration, electronic skin, wound dressing, and other fields. This review introduces various preparation methods of PVA-based hydrogels and their wide applications in the biomedical field.

Recent Development and Applications of Polydopamine in Tissue Repair and Regeneration Biomaterials

The various tissue damages are a severe problem to human health. The limited human tissue regenerate ability requires suitable biomaterials to help damage tissue repair and regeneration. Therefore, many researchers devoted themselves to exploring biomaterials suitable for tissue repair and regeneration. Polydopamine (PDA) as a natural and multifunctional material which is inspired by mussel has been widely applied in different biomaterials. The excellent properties of PDA, such as strong adhesion, photothermal and high drug-loaded capacity, seem to be born for tissue repair and regeneration. Furthermore, PDA combined with different materials can exert unexpected effects. Thus, to inspire researchers, this review summarizes the recent and representative development of PDA biomaterials in tissue repair and regeneration. This article focuses on why apply PDA in these biomaterials and what PDA can do in different tissue injuries.

Injectable hydrogels doped with PDA nanoparticles for photothermal bacterial inhibition and rapid wound healing in vitro

The difficulty of wound healing due to skin defects has been a great challenge due to the complex inflammatory microenvironment. Delayed wound healing severely affects the quality of life of patients and represents a significant economic burden for public health systems worldwide. Therefore, there is an urgent need for the development of novel wound dressings that can efficiently resist drug-resistant bacteria and have superior wound repair capabilities in clinical applications. In this study, we designed an adhesive antimicrobial hydrogel dressing (GMH) based on methacrylic-anhydride-modified gelatin and oxidized hyaluronic acid formed by Schiff base and UV-induced double cross-linking for infected wound repair. By inserting PDA nanoparticles into the hydrogel (GMH/PDA), the hydrogel has the capability of photothermal conversion and exhibits good photothermal antimicrobial properties under near-infrared (NIR) light irradiation, which helps to reduce the inflammatory response and avoid bacterial infections during the wound healing process. In addition, GMH/PDA hydrogel exhibits excellent injectability, allowing the hydrogel dressings to be adapted to complex wound surfaces, making them promising candidates for wound therapy. In conclusion, the multifunctional injectable GMH/PDA hydrogel possesses high antimicrobial efficiency, antioxidant properties and good biocompatibility, making them promising candidates for the treatment of infected skin wounds.

Fabrication and characterization of new levan@CBD biocomposite sponges as potential materials in natural, non-toxic wound dressing applications

Wound healing is a complex process; therefore, new dressings are frequently required to facilitate it. In this study, porous bacterial levan-based sponges containing cannabis oil (Lev@CBDs) were prepared and fully characterized. The sponges exhibited a suitable swelling ratio, proper water vapor transmission rate, sufficient thermal stability, desired mechanical properties, and good antioxidant and anti-inflammatory properties. The obtained Lev@CBD materials were evaluated in terms of their interaction with proteins, human serum albumin and fibrinogen, of which fibrinogen revealed the highest binding effect. Moreover, the obtained biomaterials exhibited antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa, as well as being non-hemolytic material as indicated by hemolysis tests. Furthermore, the sponges were non-toxic and compatible with L929 mouse fibroblasts and HDF cells. Most significantly, the levan sponge with the highest content of cannabis oil, in comparison to others, retained its non-hemolytic, anti-inflammatory, and antimicrobial properties after prolonged storage in a climate chamber at a constant temperature and relative humidity. The designed sponges have conclusively proven their beneficial physicochemical properties and, at the preliminary stage, biocompatibility as well, and therefore can be considered a promising material for wound dressings in future in vivo applications.

Bioadhesives with Antimicrobial Properties

Bioadhesives with antimicrobial properties enable easier and safer treatment of wounds as compared to the traditional methods such as suturing and stapling. Composed of natural or synthetic polymers, these bioadhesives seal wounds and facilitate healing while preventing infections through the activity of locally released antimicrobial drugs, nanocomponents, or inherently antimicrobial polers. Although many different materials and strategies are employed to develop antimicrobial bioadhesives, the design of these biomaterials necessitates a prudent approach as achieving all the required properties including optimal adhesive and cohesive properties, biocompatibility, and antimicrobial activity can be challenging. Designing antimicrobial bioadhesives with tunable physical, chemical, and biological properties will shed light on the path for future advancement of bioadhesives with antimicrobial properties. In this review, the requirements and commonly used strategies for developing bioadhesives with antimicrobial properties are discussed. In particular, different methods for their synthesis and their experimental and clinical applications on a variety of organs are reviewed. Advances in the design of bioadhesives with antimicrobial properties will pave the way for a better management of wounds to increase positive clinical outcomes.

Antibacterial conductive self-healing hydrogel wound dressing with dual dynamic bonds promotes infected wound healing

In clinical applications, there is a lack of wound dressings that combine efficient resistance to drug-resistant bacteria with good self-healing properties. In this study, a series of adhesive self-healing conductive antibacterial hydrogel dressings based on oxidized sodium alginate-grafted dopamine/carboxymethyl chitosan/Fe3+ (OSD/CMC/Fe hydrogel)/polydopamine-encapsulated poly(thiophene-3-acetic acid) (OSD/CMC/Fe/PA hydrogel) were prepared for the repair of infected wound. The Schiff base and Fe3+ coordination bonds of the hydrogel structure are dynamic bonds that can be repaired automatically after the hydrogel network is disrupted. Macroscopically, the hydrogel exhibits self-healing properties, allowing the hydrogel dressing to adapt to complex wound surfaces. The OSD/CMC/Fe/PA hydrogel showed good conductivity and photothermal antibacterial properties under near-infrared (NIR) light irradiation. In addition, the hydrogels exhibit tunable rheological properties, suitable mechanical properties, antioxidant properties, tissue adhesion properties and hemostatic properties. Furthermore, all hydrogel dressings improved wound healing in the infected full-thickness defect skin wound repair test in mice. The wound size repaired by OSD/CMC/Fe/PA3 hydrogel + NIR was much smaller (12%) than the control group treated with Tegaderm™ film after 14 days. In conclusion, the hydrogels have high antibacterial efficiency, suitable conductivity, great self-healing properties, good biocompatibility, hemostasis and antioxidant properties, making them promising candidates for wound healing dressings for the treatment of infected skin wounds.

Transplantation of active nucleus pulposus cells with a keep-charging hydrogel microsphere system to rescue intervertebral disc degeneration

BACKGROUND

Cell transplantation has been demonstrated as a promising approach in tissue regeneration. However, the reactive oxygen species (ROS) accumulation and inflammation condition establish a harsh microenvironment in degenerated tissue, which makes the transplanted cells difficult to survive.

METHODS

In this study, we constructed a keep-charging hydrogel microsphere system to enable cells actively proliferate and function in the degenerated intervertebral disc. Specifically, we combined Mg2+ to histidine-functionalized hyaluronic acid (HA-His-Mg2+) through coordination reaction, which was further intercrossed with GelMA to construct a double-network hydrogel microsphere (GelMA/HA-His-Mg2+, GHHM) with microfluidic methods. In vitro, the GHHM loaded with nucleus pulposus cells (GHHM@NPCs) was further tested for its ability to promote NPCs proliferation and anti-inflammatory properties. In vivo, the ability of GHHM@NPCs to promote regeneration of NP tissue and rescue intervertebral disc degeneration (IVDD) was evaluated by the rat intervertebral disc acupuncture model.

RESULTS

The GHHM significantly enhanced NPCs adhesion and proliferation, providing an ideal platform for the NPCs to grow on. The loaded NPCs were kept active in the degenerative intervertebral disc microenvironment as charged by the Mg2+ in GHHM microspheres to effectively support the loaded NPCs to reply against the ROS-induced inflammation and senescence. Moreover, we observed that GHHM@NPCs effectively alleviated nucleus pulposus degeneration and promoted its regeneration in the rat IVDD model.

CONCLUSION

In conclusion, we constructed a keep charging system with a double-network hydrogel microsphere as a framework and Mg2+ as a cell activity enhancer, which effectively maintains NPCs active to fight against the harsh microenvironment in the degenerative intervertebral disc. The GHHM@NPCs system provides a promising approach for IVDD management.

Injectable spontaneously formed asymmetric adhesive hydrogel with controllable removal for wound healing

Healing large-scale wounds has been a long-standing challenge in the field of biomedicine. Herein, we propose an injectable oxidated sodium alginate/gelatin/3,3'-dithiobis(propionic hydrazide)-aurum (Alg-CHO/gelatin/DTPH-Au) hydrogel filler with asymmetric adhesion ability and removability, which is formed by the Schiff-base reaction between aldehyde-based sodium alginate and multi-amino crosslinkers (gelatin and DTPH), combined with the coordination interaction between Au nanoparticles and disulfide bond of DTPH. Consequently, the prepared Alg-CHO/gelatin/DTPH-Au hydrogel exhibits high mechanical properties and injectable behaviors owing to its multiple-crosslinked interactions. Moreover, because various types of interaction bonding form on the contact side with the tissue, denser crosslinking of the upper layer relative to the lower layer occurs. Combined with the temperature difference between the upper and lower surfaces, this results in asymmetric adhesive properties. Owing to the photothermal effect, the reversible coordination interaction between Au nanoparticles and DTPH and the change in the triple helix structure of gelatin to a coil structure impart the filler-phased removability and antibacterial ability. The choice of all natural polymers also allows for favorable degradability of the wound filler and outstanding biocompatibility. Based on these features, this versatile wound filler can achieve a wide range of applications in the field of all-skin wound repair.

Injectable and photothermal antibacterial bacterial cellulose cryogel for rapid hemostasis and repair of irregular and deep skin wounds

For irregular and deep skin wounds, it's difficult for wound dressing to reach the injured site to achieve rapid hemostasis and provide wound protection. Bacterial cellulose (BC) has high strength and natural three-dimensional pore structure, which endows it shape recovery ability after absorbing blood when injected to the wound. Therefore, in the study, an injectable aldehyde bacterial cellulose/polydopamine (DBC/PDA) photothermal cryogel was prepared by oxidation polymerization method for hemostasis and repair of irregular and deep skin wounds. BC was oxidized by NaIO4 to form DBC and dopamine (DA) was introduced into DBC by reacting with the aldehyde group in DBC through Schiff base reaction. Under oxidation effect of NaIO4 and with freezing condition, water crystallization led to local aggregation of DA and DBC, and at the same time DA was oxidized to PDA and polymerized with DA on DBC. After the melting process, the porous cryogel was obtained. The introduction of PDA enhances the photothermal properties of DBC/PDA cryogel. DBC/PDA cryogel can kill most bacteria and provide wound protection under near-infrared light. In vitro and in vivo hemostatic tests show that the DBC/PDA cryogel can quickly absorb blood and stop bleeding. Combined with its good injectable, DBC/PDA cryogel can provide rapid hemostatic and protection in the face of irregular and deep skin wounds.

Antibacterial-Antioxidative Thiolated Gelatin/Methacrylated Silk Fibroin Hydrogels with Nitric Oxide Release Catalyzed by Metal-Polyphenol Nanoparticles for MRSA-Infected Wound Healing

Chronic wound infection often leads to irregular tissue closure and accompanies delayed healing and economy issues. Developing an ideal wound dressing that can control the occurrence of antibacterial infections and biological responses is highly desirable. In this study, a multifunctional hybrid hydrogel (GS@EG-Cu-CA NPs) containing synthesized thiolated gelatin, methacrylated silk fibroin, and (-)-epigallocatechin gallate-copper ionic-carrageenan nanoparticles (EG-Cu-CA NPs) was engineered by a thio-ene click reaction. The metal-polyphenol EG-Cu-CA NPs were encapsulated with kappa-carrageenan to enhance its aqueous-soluble, mechanical, and bioactive properties and endowed the hydrogel dressing with fascinating antibacterial, antioxidation, and nitric oxide (NO) generation by catalyzing. The hybrid hydrogels also illustrated a favorable cytocompatibility. Benefiting from the thio-ene click reaction, the hybrid hydrogels were injected and photocured rapidly in situ to cover an irregular wound. In an SD rat full-thickness skin-wound-infected model, the methicillin-resistant Staphylococcus aureus-infected wound covered with GS@EG-Cu-CA NPs was almost completely healed after 10 days. This study presents a facile design of hydrogel dressing incorporating metal-polyphenol nanoparticles, which demonstrates a promising potential way for dealing with effective wound infection management and other complicated wound healings.

Photothermal antibacterial materials to promote wound healing

Wound healing is a crucial process that restores the integrity and function of the skin and other tissues after injury. However, external factors, such as infection and inflammation, can impair wound healing and cause severe tissue damage. Therefore, developing new drugs or methods to promote wound healing is of great significance. Photothermal therapy (PTT) is a promising technique that uses photothermal agents (PTAs) to convert near-infrared radiation into heat, which can eliminate bacteria and stimulate tissue regeneration. PTT has the advantages of high efficiency, controllability, and low drug resistance. Hence, nanomaterial-based PTT and its related strategies have been widely explored for wound healing applications. However, a comprehensive review of PTT-related strategies for wound healing is still lacking. In this review, we introduce the physiological mechanisms and influencing factors of wound healing, and summarize the types of PTAs commonly used for wound healing. Then, we discuss the strategies for designing nanocomposites for multimodal combination treatment of wounds. Moreover, we review methods to improve the therapeutic efficacy of PTT for wound healing, such as selecting the appropriate wound dressing form, controlling drug release, and changing the infrared irradiation window. Finally, we address the challenges of PTT in wound healing and suggest future directions.

Double-Layer Hydrogel with Glucose-Activated Two-Stage ROS Regulating Properties for Programmed Diabetic Wound Healing

Slow healing of wounds induces great pain in diabetic patients. However, developing new approaches to promote diabetic wound healing is still one of the toughest challenges in the medical field. Here, we constructed a new double-layer hydrogel to effectively regulate reactive oxygen species (ROS) on the wound and promote diabetic wound healing. The inner layer contains glucose oxidase (Gox), ferrocene-modified quaternary ammonium chitosan (Fc-QCs), and poly(β-cyclodextrin) (Pβ-CD), which is used to generate hydroxyl radicals (•OH) for antibacterial in the early stage of wound healing and collapses gradually. The outer layer is composed of gelatin and dopamine. In the later stage of wound healing, the outer layer contacts the skin, which is beneficial for ROS clearance on the wound. Antibacterial, ROS scavenging, and wound healing experiments have shown that the double-layer hydrogel possesses two-stage ROS regulating properties for programmed diabetic wound healing. In conclusion, it will be one of the most potential dressings for treating diabetic wounds in the future.

Nanosilver Embedded in a Magnetosome Nanoflower to Enhance Antibacterial Activity for Wound Dressing Applications

The natural biofilm on magnetosomes obtained from the biomineralization of magnetotactic bacteria, which replaced a complex chemical modification process on the surface of Fe3O4, can be used as the organic component and copper(II) ions as the inorganic component to form organic-inorganic nanoflowers in phosphate systems. Characterization by scanning electron microscopy, Fourier transform infrared spectroscopy, and vibrating-sample magnetometry proved that magnetic nanoflowers loaded with silver ions (Ag/MN-Cu×NFs) were successfully fabricated. In vitro antibacterial experiments demonstrated that Ag/MN-Cu×NFs displayed strong antibacterial effects against Escherichia coli and Staphylococcus aureus, with minimum inhibitory concentrations of 10 and 80 μg/mL, respectively. Ag/MN-Cu×NFs, which possessed good biocompatibility as confirmed by cytotoxicity and hemolysis tests, were able to promote wound healing in the face of bacterial infection in vivo without causing toxicity to major organs. Therefore, magnetosomes as a natural carrier have great application potential in the synthesis of multifunctional magnetosomes by direct hybridization with a target substance.

An injectable bioactive dressing based on platelet-rich plasma and nanoclay: Sustained release of deferoxamine to accelerate chronic wound healing

Delayed diabetic wound healing has placed an enormous burden on society. The key factors limiting wound healing include unresolved inflammation and impaired angiogenesis. Platelet-rich plasma (PRP) gel, a popular biomaterial in the field of regeneration, has limited applications due to its non-injectable properties and rapid release and degradation of growth factors. Here, we prepared an injectable hydrogel (DPLG) based on PRP and laponite by a simple one-step mixing method. Taking advantages of the non-covalent interactions, DPLG could overcome the limitations of PRP gels, which is injectable to fill irregular injures and could serve as a local drug reservoir to achieve the sustained release of growth factors in PRP and deferoxamine (an angiogenesis promoter). DPLG has an excellent ability in accelerating wound healing by promoting macrophage polarization and angiogenesis in a full-thickness skin defect model in type I diabetic rats and normal rats. Taken together, this study may provide the ingenious and simple bioactive wound dressing with a superior ability to promote wound healing.

Microenvironment-responsive Cu-phenolic networks coated nanofibrous dressing with timely macrophage phenotype transition for chronic MRSA infected wound healing

Methicillin-resistant Staphylococcus aureus (MRSA) infection is a pressing clinical issue that impedes wound healing. Pro-inflammatory M1 macrophages is required to clear bacteria and recruit various cell types during the initial phase of wound healing, but timing of this process is crucial. Herein, a microenvironment-responsive nanofibrous dressing capable of timely macrophage phenotype transition in vivo is constructed by coating copper ions (Cu2+)-polydopamine (PDA) networks on poly (ε-caprolactone) fiber (PCL-fiber) membrane. During the initial post-implantation period, the nanofibrous dressing show pH-sensitive Cu2+ release in the acidic infection microenvironment. The release Cu2+ have a direct killing effect on MRSA, and promote the proinflammatory M1 phenotype of macrophages to enhance the antibacterial macrophage response. Later, PDA to become a reactive oxygen species (ROS) scavenger when in microenvironments with elevated ROS levels, which conferred the dressing with an immunomodulatory activity that convert M1 macrophages into M2 macrophages. In vivo examination in an MRSA infected full-thickness skin wounds of rat model demonstrates that this dressing significantly facilitated infection eradication and wound healing through modulating local inflammatory phenotype. Overall, this study offers a simple and effective approach for timely manipulation of inflammation progression to promote infected wound healing.

Nanosized Silk-Magnesium Complexes for Tissue Regeneration

Metal ions provide multifunctional signals for cell and tissue functions, including regeneration. Inspired by metal-organic frameworks (MOFs), nanosized silk protein aggregates with a high negative charge density are used to form stable silk-magnesium ion complexes. Magnesium ions (Mg ions) are added directly to silk nanoparticle solutions, inducing gelation through the formation of silk-Mg coordination complexes. The Mg ions are released slowly from the nanoparticles through diffusion, with sustained release via tuning the degradation or dissolution of the nanosized silk aggregates. Studies in vitro reveal a dose-dependent influence of Mg ions on angiogenic and anti-inflammatory functions. Silk-Mg ion complexes in the form of hydrogels also stimulate tissue regeneration with a reduced formation of scar tissue in vivo, suggesting potential utility in tissue regeneration.