Gallium(III)-Mediated Dual-Cross-Linked Alginate Hydrogels with Antibacterial Properties for Promoting Infected Wound Healing

Marine-inspired near-infrared-activated multifunctional hydrogel with immunomodulatory properties for multidrug-resistant bacterial infected wound healing

Multidrug-resistant (MDR) bacterial infections in skin wounds have become a critical medical challenge due to the diminishing effectiveness of available antibiotics. Persistent bacterial infections, excessive reactive oxygen and nitrogen species (ROS/RNS), and prolonged inflammatory responses significantly impede the wound healing process. To address these challenges, we propose a marine-inspired multifunctional 3AGM hydrogel designed to provide comprehensive antibacterial action, mitigate oxidative stress, and promote wound healing throughout the treatment process. The hydrogel features a cross-linked network of acrylic acid and acrylamide, incorporating natural melanin nanoparticles (MNPs) extracted from cuttlefish ink and polydopamine nanoparticles (APDA) polymerized by l-arginine. Gallium ions (Ga3+) serve as both ionic crosslinkers and antibacterial agents. The MNPs endow the hydrogel with controllable photothermal therapeutic capabilities, and in combination with Ga3+, provide synergistic antibacterial treatment for infected wounds. The integration of APDA imparts strong antioxidant activity to 3AGM hydrogel, effectively reducing oxidative stress at the wound site and promoting sustained tissue regeneration. The 3AGM hydrogel demonstrates promising potential in promoting wound healing for skin infections caused by MDR bacteria.

Reversible Stiffening of Biopolymeric Hybrid Networks by Dynamically Switching Cross-Links In Situ

Achieving reversible stiffening of biopolymer networks in a controlled manner remains a challenging topic in materials science, especially when trying to assess the following changes in mechanical material properties in real time. To address these challenges, we here utilize a custom-made measurement setup that allows us to manipulate the cross-linking state of alginate-based hydrogels in situ while quantifying the achieved alterations in the viscoelastic response of the biopolymer networks. Interpolymer connections in the biopolymer networks are created by a combination of light-induced, covalent cross-links, ionic cross-links, and DNA-based cross-links, where the latter two can be successfully removed again by employing either chelating agents (e.g., ethylenediaminetetraacetic acid and citrate) or suitable displacement DNA strands. In part, this range of the different cross-linking options mentioned is inter alia made possible by incorporating the glycoprotein mucin into the alginate system, which also allows for a range of different starting (∼0.2-400 Pa), intermediate (∼25 Pa-1.6 kPa), and final stiffnesses (∼4 Pa-1.2 kPa) of the mixed hydrogel matrix. At the same time, the presence of mucins (1-4% (w/v)) in the biopolymer mixture enhances the properties of the cytocompatible hydrogel by improving its antibacterial characteristics. Such well-controllable alginate/mucin networks with dynamically switchable mechanical properties will likely find broad applications in cell cultivation studies or tissue engineering applications.

Rapid Gelation of Anti-Swelling, Self-Healing, and Biocompatible PEG Hydrogels Based on CBT-Cys Click Reaction under Mild Conditions

Hydrogels, essential biomaterials in bioengineering, face challenges of undesirable swelling in applications requiring stable dimensions. This study presents a novel anti-swelling hydrogel using a cyanobenzothiazole (CBT)-cysteine (Cys) click reaction, inspired by luciferin chemistry. By functionalizing 4-Arm PEG with CBT and synthesizing N-terminal cysteine-terminated ethylenediamine precursors, gels are formed under mild conditions, avoiding harsh reagents or catalysts and ensuring compatibility with physiological environments. The resulting hydrogels benefit from enhanced cross-linking density and elastic retractive force due to hydrogen bonding and π-π stacking within the network, which effectively resists polymer-water interactions. Therefore, the CBT-Cys PEG hydrogel exhibits significant anti-swelling properties in water, PBS, and extreme pH environments. Additionally, they demonstrate excellent mechanical strength, self-healing ability, and biocompatibility. This simple, scalable method offers a versatile platform for developing anti-swelling hydrogels with broad potential in biomedical engineering.

The role of bacterial metabolism in antimicrobial resistance

The relationship between bacterial metabolism and antibiotic treatment is complex. On the one hand, antibiotics leverage cell metabolism to function. On the other hand, increasing research has highlighted that the metabolic state of the cell also impacts all aspects of antibiotic biology, from drug efficacy to the evolution of antimicrobial resistance (AMR). Given that AMR is a growing threat to the current global antibiotic arsenal and ability to treat infectious diseases, understanding these relationships is key to improving both public and human health. However, quantifying the contribution of metabolism to antibiotic activity and subsequent bacterial evolution has often proven challenging. In this Review, we discuss the complex and often bidirectional relationships between metabolism and the various facets of antibiotic treatment and response. We first summarize how antibiotics leverage metabolism for their function. We then focus on the converse of this relationship by specifically delineating the unique contribution of metabolism to three distinct but related arms of antibiotic biology: antibiotic efficacy, AMR evolution and AMR mechanisms. Finally, we note the relevance of metabolism in clinical contexts and explore the future of metabolic-based strategies for personalized antimicrobial therapies. A deeper understanding of these connections is crucial for the broader scientific community to address the growing crisis of AMR and develop future effective therapeutics.

In Vitro Assessment of Gallium Nanoalloy Hydrogels for Antimicrobial and Wound Healing Applications

Chronic and recurring wounds pose a significant challenge in modern healthcare, leading to substantial morbidity. These wounds allow pathogens to colonize, potentially resulting in local and systemic infections. Current interventions need to be revised and become increasingly less reliable due to the emergence of antibiotic resistance. In the present study, we aim to address these issues by fabricating hydrogels impregnated with gallium-based nanoalloys for their antimicrobial activity. Gallium liquid metal nanoparticles (approximately 100 nm in diameter) were alloyed in different combinations with bismuth and silver ions through a galvanic replacement reaction. These multimetallic hydrogels showed favorable antibacterial activity against the Gram-positive Staphylococcus aureus and the Gram-negative Pseudomonas aeruginosa, as observed with fluorescence microscopy and inhibition assays. The multimetallic hydrogels showed no toxicity against murine macrophages or human dermal fibroblasts and enhanced in vitro wound healing. The development of these innovative gallium-based hydrogels represents a promising strategy to combat chronic wounds and their associated complications, offering an effective alternative to current antimicrobial treatments amidst rising antibiotic resistance.

Copper ions-photo dual-crosslinked alginate hydrogel for angiogenesis and osteogenesis

Early healing of bone defects is still a clinical challenge. Many bone-filling materials have been studied, among which photocrosslinked alginate has received significant attention due to its good biocompatibility and morphological plasticity. Although it has been confirmed that photocrosslinked alginate can be used as an extracellular matrix for 3D cell culture, it lacks osteogenesis-related biological functions. This study constructed a copper ions-photo dual-crosslinked alginate hydrogel scaffold by controlling the copper ion concentration. The scaffolds were shaped by photocrosslinking and then endowed with biological functions by copper ions crosslinking. According to in vitro research, the dual-crosslinked hydrogel increased the compressive strength and favored copper dose-dependent osteoblast differentiation and cell surface adherence of rat bone marrow mesenchymal stem cells and the expression of type I collagen (Col1), runt-related transcription factor 2 (Runx2), osteocalcin (OCN), vascular endothelial growth factor (VEGF). In addition, hydrogel scaffolds were implanted into rat skull defects, and more angiogenesis and osteogenesis could be observed in in vivo studies. The above results show that the copper-photo-crosslinked hydrogel scaffold has excellent osseointegration properties and can potentially promote angiogenesis and early healing of bone defects, providing a reference solution for bone tissue engineering materials.

Advancing burn wound treatment: exploring hydrogel as a transdermal drug delivery system

Burn injuries are prevalent and life-threatening forms that contribute significantly to mortality rates due to associated wound infections. The management of burn wounds presents substantial challenges. Hydrogel exhibits tremendous potential as an ideal alternative to traditional wound dressings such as gauze. This is primarily attributed to its three-dimensional (3D) crosslinked polymer network, which possesses a high water content, fostering a moist environment that supports effective burn wound healing. Additionally, hydrogel facilitates the penetration of loaded therapeutic agents throughout the wound surface, combating burn wound pathogens through the hydration effect and thereby enhancing the healing process. However, the presence of eschar formation on burn wounds obstructs the passive diffusion of therapeutics, impairing the efficacy of hydrogel as a wound dressing, particularly in cases of severe burns involving deeper tissue damage. This review focuses on exploring the potential of hydrogel as a carrier for transdermal drug delivery in burn wound treatment. Furthermore, strategies aimed at enhancing the transdermal delivery of therapeutic agents from hydrogel to optimize burn wound healing are also discussed.

Alginate-based hydrogels mediated biomedical applications: A review

With the development in the field of biomaterials, research on alternative biocompatible materials has been initiated, and alginate in polysaccharides has become one of the research hotspots due to its advantages of biocompatibility, biodegradability and low cost. In recent years, with the further understanding of microscopic molecular structure and properties of alginate, various physicochemical methods of cross-linking strategies, as well as organic and inorganic materials, have led to the development of different properties of alginate hydrogels for greatly expanded applications. In view of the potential application prospects of alginate-based hydrogels, this paper reviews the properties and preparation of alginate-based hydrogels and their major achievements in delivery carrier, dressings, tissue engineering and other applications are also summarized. In addition, the combination of alginate-based hydrogel and new technology such as 3D printing are also involved, which will contribute to further research and exploration.

A Hemoglobin Bionics-Based System for Combating Antibiotic Resistance in Chronic Diabetic Wounds via Iron Homeostasis Regulation

Owing to the increased tissue iron accumulation in patients with diabetes, microorganisms may activate high expression of iron-involved metabolic pathways, leading to the exacerbation of bacterial infections and disruption of systemic glucose metabolism. Therefore, an on-demand transdermal dosing approach that utilizes iron homeostasis regulation to combat antimicrobial resistance is a promising strategy to address the challenges associated with low administration bioavailability and high antibiotic resistance in treating infected diabetic wounds. Here, it is aimed to propose an effective therapy based on hemoglobin bionics to induce disturbances in bacterial iron homeostasis. The preferred "iron cargo" is synthesized by protoporphyrin IX chelated with dopamine and gallium (PDGa), and is delivered via a glucose/pH-responsive microneedle bandage (PDGa@GMB). The PDGa@GMB downregulates the expression levels of the iron uptake regulator (Fur) and the peroxide response regulator (perR) in Staphylococcus aureus, leading to iron nutrient starvation and oxidative stress, ultimately suppressing iron-dependent bacterial activities. Consequently, PDGa@GMB demonstrates insusceptibility to genetic resistance while maintaining sustainable antimicrobial effects (>90%) against resistant strains of both S. aureus and E. coli, and accelerates tissue recovery (<20 d). Overall, PDGa@GMB not only counteracts antibiotic resistance but also holds tremendous potential in mediating microbial-host crosstalk, synergistically attenuating pathogen virulence and pathogenicity.

Engineering Wet-Resistant and Osteogenic Nanocomposite Adhesive to Control Bleeding and Infection after Median Sternotomy

Median sternotomy surgery stands as one of the prevailing strategies in cardiac surgery. In this study, the cutting-edge bone adhesive is designed, inspired by the impressive adhesive properties found in mussels and sandcastle worms. This work has created an osteogenic nanocomposite coacervate adhesive by integrating a cellulose-polyphosphodopamide interpenetrating network, quaternized chitosan, and zinc, gallium-doped hydroxyapatite nanoparticles. This adhesive is characterized by robust catechol-metal coordination which effectively adheres to both hard and soft tissues with a maximum adhesive strength of 900 ± 38 kPa on the sheep sternum bone, surpassing that of commercial bone adhesives. The release of zinc and gallium cations from nanocomposite adhesives and quaternized chitosan matrix imparts remarkable antibacterial properties and promotes rapid blood coagulation, in vitro and ex vivo. It is also proved that this nanocomposite adhesive exhibits significant in vitro bioactivity, stable degradability, biocompatibility, and osteogenic ability. Furthermore, the capacity of nanocomposite coacervate to adhere to bone tissue and support osteogenesis contributes to the successful healing of a sternum bone defect in a rabbit model in vivo. In summary, these nanocomposite coacervate adhesives with promising characteristics are expected to provide solutions to clinical issues faced during median sternotomy surgery.

Insect chitosan/pullulan/gallium photo-crosslinking hydrogels with multiple bioactivities promote MRSA-infected wound healing

Methicillin-resistant Staphylococcus aureus (MRSA) and other drug-resistant bacteria have become more common in recent years, which has made it extremely difficult to treat and heal many different kinds of wounds and caused enormous financial losses. Because of its unique "Trojan horse" function, Ga3+ has been recognized as a new possible candidate for inhibiting and eradicating drug-resistant bacteria. Furthermore, natural polysaccharide materials with outstanding biological characteristics, such as insect chitosan (CS) and pullulan (PUL), have attracted significant interest. In this study, we used quaternized-catechol chitosan (QDCS-PA), methacrylate-dialdehyde pullulan (DPUL-GMA), and gallium ion (Ga) to create a multi-crosslinked photo-enhanced hydrogel (Q-D/Ga/UV) with antimicrobial, hemostatic, self-healing, and injectable properties for promoting MRSA-infected wound healing. In vitro, the Q-D/Ga/UV hydrogels demonstrated good mechanical properties, antioxidant capabilities, biocompatibility, hemostatic properties, and antibacterial activity. The addition of gallium ions enhanced the hydrogels' mechanical properties, hemostatic capabilities, antibacterial activity, and ability to induce wound healing. Q-D/Ga/UV hydrogel significantly promoted wound contraction, collagen deposition, and angiogenesis while also suppressing inflammation in a whole-skin wound model of MRSA-infected rats. In conclusion, Q-D/Ga/UV hydrogels demonstrate significant promise for healing wounds infected with drug-resistant bacteria.

Immunotherapeutic hydrogel for co-delivery of STAT3 siRNA liposomes and lidocaine hydrochloride for postoperative comprehensive management of NSCLC in a single application

Despite standard treatment for non-small cell lung cancer (NSCLC) being surgical resection, cancer recurrence and complications, such as induction of malignant pleural effusion (MPE) and significant postoperative pain, usually result in treatment failure. In this study, an alginate-based hybrid hydrogel (SOG) is developed that can be injected into the resection surface of the lungs during surgery. Briefly, endoplasmic reticulum-modified liposomes (MSLs) pre-loaded with the signal transducer and activator of transcription 3 (STAT3) small interfering RNA and lidocaine hydrochloride are encapsulated in SOG. Once applied, MSLs strongly downregulated STAT3 expression in the tumor microenvironment, resulting in the apoptosis of lung cancer cells and polarization of tumor-associated macrophages towards the M1-like phenotype. Meanwhile, the release of lidocaine hydrochloride (LID) was beneficial for pain relief and natural killer cell activation. Our data demonstrated MSL@LID@SOG not only efficiently inhibited tumor growth but also potently improved the quality of life, including reduced MPE volume and pain relief in orthotopic NSCLC mouse models, even with a single administration. MSL@LID@SOG shows potential for comprehensive clinical management upon tumor resection in NSCLC, and may alter the treatment paradigms for other cancers.

A win-win platform: Stabilized black phosphorous nanosheets loading gallium ions for enhancing the healing of bacterial-infected wounds through synergistic antibacterial approaches

Bacterial infection is the most common complication in wound healing, highlighting an urgent need for the development of innovative antibacterial technologies and treatments to address the growing threats posed by bacterial infections. Black phosphorus nanosheets (BPNSs), as a promising two-dimensional nanomaterial, have been utilized in treating infected wounds. However, BP's limited stability restricts its application. In this study, we enhance BP's stability and its antibacterial properties by anchoring gallium ions (Ga3+) onto BP's surface, creating a novel antibacterial platform. This modification reduces BP's electron density and enhances its antibacterial capabilities through a synergistic effect. Under near-infrared (NIR) irradiation, the BP/Ga3+ combination exerts antibacterial effects via photothermal therapy (PTT) and photodynamic therapy (PDT), while also releasing Ga3+. The Ga3+ employ a 'Trojan horse strategy' to disrupt iron metabolism, significantly boosting the antibacterial efficacy of the complex. This innovative material offers a viable alternative to antibiotics and holds significant promise for treating infected wounds and aiding skin reconstruction.

Metal Cross-Linked Supramolecular Gel Noodles: Structural Insights and Antibacterial Assessment

Achieving precise control over gelator alignment and morphology is crucial for crafting tailored materials and supramolecular structures with distinct properties. We successfully aligned the self-assembled micelles formed by a functionalized dipeptide 2NapFF into long 1-D "gel noodles" by cross-linking with divalent metal chlorides. We identify the most effective cross-linker for alignment, enhancing mechanical stability, and imparting functional properties. Our study shows that Group 2 metal ions are particularly suited for creating mechanically robust yet flexible gel noodles because of their ionic and nondirectional bonding with carboxylate groups. In contrast, the covalent nature and high directional bonds of d-block metal ions with carboxylates tend to disrupt the self-assembly of 2NapFF. Furthermore, the 2NapFF-Cu noodles demonstrated selective antibacterial activity, indicating that the potent antibacterial property of the copper(II) ion is preserved within the cross-linked system. By merging insights into molecular alignment, gel extrusion processing, and integrating specific functionalities, we illustrate how the versatility of dipeptide-based gels can be utilized in creating next-generation soft materials.

Tailoring Biomaterials Ameliorate Inflammatory Bone Loss

Inflammatory diseases, such as rheumatoid arthritis, periodontitis, chronic obstructive pulmonary disease, and celiac disease, disrupt the delicate balance between bone resorption and formation, leading to inflammatory bone loss. Conventional approaches to tackle this issue encompass pharmaceutical interventions and surgical procedures. Nevertheless, pharmaceutical interventions exhibit limited efficacy, while surgical treatments impose trauma and significant financial burden upon patients. Biomaterials show outstanding spatiotemporal controllability, possess a remarkable specific surface area, and demonstrate exceptional reactivity. In the present era, the advancement of emerging biomaterials has bestowed upon more efficacious solutions for combatting the detrimental consequences of inflammatory bone loss. In this review, the advances of biomaterials for ameliorating inflammatory bone loss are listed. Additionally, the advantages and disadvantages of various biomaterials-mediated strategies are summarized. Finally, the challenges and perspectives of biomaterials are analyzed. This review aims to provide new possibilities for developing more advanced biomaterials toward inflammatory bone loss.

Self-healing and durable antifouling zwitterionic hydrogels based on functionalized liquid metal microgels

Hydrogels are a promising new class of antifouling materials. But their utility is constrained by low mechanical strength and unsatisfactory antifouling performance over the long term. Herein, we successfully prepared zwitterionic polymer PEIS cross-linked gallium-based liquid metal microgels-based (PEIS-Gel@PMPC-GLM) hydrogels via UV-curing and amidation reaction. The as-prepared hydrogels showed preferable mechanical properties and superior hydrophilicity to the original hydrogels. The PEIS-Gel@PMPC-GLM hydrogels could prevent the adhesion of more than 90 % of microalgae and nearly 100 % of bacteria in a short-term antifouling test. PEIS-Gel@PMPC-GLM hydrogels also performed exceptionally well in the high concentration antibacterial test and the long-term antifouling test (remove more than 90 % bacteria and 80 % microalgae). In addition to releasing a high concentration of gallium ions, as shown by the ICP-OES test, PEIS-Gel@PMPC-GLM hydrogels also exhibitedexcellent lubrication performance, as demonstrated by the friction test (coefficient of friction as low as 0.023). Therefore, the antifouling effect of gallium ions combined with the strong hydration ability of the surfaces endowed the hydrogels remarkable antibacterial and antifouling properties. As a result of the exposed gallium atoms inducing further crosslinking of residual vinyl monomer in hydrogels, PEIS-Gel@PMPC-GLM hydrogels revealed certain self-healing performance.

6-Aza-2-Thiothymine-Capped Gold Nanoclusters as Robust Antimicrobial Nanoagents for Eradicating Multidrug-Resistant Escherichia coli Infection

Multidrug-resistant bacterial infections, especially those caused by multidrug-resistant Escherichia coli (E. coli) bacteria, are an ever-growing threat because of the shrinking arsenal of efficacious antibiotics. Therefore, it is urgently needed to develop a kind of novel, long-term antibacterial agent effectively overcome resistant bacteria. Herein, we present a novel designed antibacterial agent-6-Aza-2-thiothymine-capped gold nanoclusters (ATT-AuNCs), which show excellent antibacterial activity against multidrug-resistant E. coli bacteria. The prepared AuNCs could permeabilize into the bacterial cell membrane via binding with a bivalent cation (e.g., Ca2+), followed by the generation of reactive oxygen species (e.g., •OH and •O2-), ultimately resulting in protein leakage from compromised cell membranes, inducing DNA damage and upregulating pro-oxidative genes intracellular. The AuNCs also speed up the wound healing process without noticeable hemolytic activity or cytotoxicity to erythrocytes and mammalian tissue. Altogether, the results indicate the great promise of ATT-AuNCs for treating multidrug-resistant E. coli bacterial infection.

Multifunctional and theranostic hydrogels for wound healing acceleration: An emphasis on diabetic-related chronic wounds

Hydrogels represent intricate three-dimensional polymeric structures, renowned for their compatibility with living systems and their ability to naturally degrade. These networks stand as promising and viable foundations for a range of biomedical uses. The practical feasibility of employing hydrogels in clinical trials has been well-demonstrated. Among the prevalent biomedical uses of hydrogels, a significant application arises in the context of wound healing. This intricate progression involves distinct phases of inflammation, proliferation, and remodeling, often triggered by trauma, skin injuries, and various diseases. Metabolic conditions like diabetes have the potential to give rise to persistent wounds, leading to delayed healing processes. This current review consolidates a collection of experiments focused on the utilization of hydrogels to expedite the recovery of wounds. Hydrogels have the capacity to improve the inflammatory conditions at the wound site, and they achieve this by diminishing levels of reactive oxygen species (ROS), thereby exhibiting antioxidant effects. Hydrogels have the potential to enhance the growth of fibroblasts and keratinocytes at the wound site. They also possess the capability to inhibit both Gram-positive and Gram-negative bacteria, effectively managing wounds infected by drug-resistant bacteria. Hydrogels can trigger angiogenesis and neovascularization processes, while also promoting the M2 polarization of macrophages, which in turn mitigates inflammation at the wound site. Intelligent and versatile hydrogels, encompassing features such as pH sensitivity, reactivity to reactive oxygen species (ROS), and responsiveness to light and temperature, have proven advantageous in expediting wound healing. Furthermore, hydrogels synthesized using environmentally friendly methods, characterized by high levels of biocompatibility and biodegradability, hold the potential for enhancing the wound healing process. Hydrogels can facilitate the controlled discharge of bioactive substances. More recently, there has been progress in the creation of conductive hydrogels, which, when subjected to electrical stimulation, contribute to the enhancement of wound healing. Diabetes mellitus, a metabolic disorder, leads to a slowdown in the wound healing process, often resulting in the formation of persistent wounds. Hydrogels have the capability to expedite the healing of diabetic wounds, facilitating the transition from the inflammatory phase to the proliferative stage. The current review sheds light on the biological functionalities of hydrogels, encompassing their role in modulating diverse mechanisms and cell types, including inflammation, oxidative stress, macrophages, and bacteriology. Additionally, this review emphasizes the significance of smart hydrogels with responsiveness to external stimuli, as well as conductive hydrogels for promoting wound healing. Lastly, the discussion delves into the advancement of environmentally friendly hydrogels with high biocompatibility, aimed at accelerating the wound healing process.

Layer-by-layer microneedle patch with antibacterial and antioxidant dual activities for accelerating bacterial-infected wound healing

Bacterial-infected wound healing has always been a huge challenge to humans. Owing to the appearance of antibiotic resistance, there is an emergency need to design antibiotic-free wound dressings to treat such wounds. Herein, a novel antibiotic-free microneedle patch was designed, which its backing layer with antioxidant effect was coated with sodium carboxymethyl cellulose, 2-O-α-D-glucopyranosyl-L-ascorbic acid (GLAA), and 2-hydroxypropyltrimethyl ammonium chloride chitosan through electrostatic interaction based on layer-by-layer self-assembly technique, and its tips consisted of gelatin and tannic acid (TA) via hydrogen bonding interaction (CGH/GTA MN patch). The obtained CGH/GTA MN patch could effectively puncture the skin, and exhibit properties of pH-responsive TA and GLAA release. In vitro experiments showed that the obtained CGH/GTA MN patch has excellent antioxidative (scavenging DPPH efficacy is above 80 %, and scavenging ABTS efficiency reaches about 100 %), antibacterial (antibacterial rates of nearly 100 % for both Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli)), biodegradable, and biocompatible properties. In the S. aureus-infected rat wounds, the CGH/GTA MN patch could efficiently accelerate infected-wound healing by eliminating S. aureus infection, inhibiting inflammation, promoting angiogenesis, and accelerating epidermal regeneration. Thus, this study will provide a promising strategy to heal bacterial-infected wounds.

Angiogenesis, hemocompatibility and bactericidal effect of bioactive natural polymer-based bilayer adhesive skin substitute for infected burned wound healing

Thermal wounds are complex and lethal with irregular shapes, risk of infection, slow healing, and large surface area. The mortality rate in patients with infected burns is twice that of non-infected burns. Developing multifunctional skin substitutes to augment the healing rate of infected burns is vital. Herein, we 3D printed a hydrogel scaffold comprising carboxymethyl chitosan (CMCs) and oxidized alginate grafted catechol (O-AlgCat) on a hydrophobic electrospun layer, forming a bilayer skin substitute (BSS). The functional layer (FL) was fabricated by physiochemical crosslinking to ensure favorable biodegradability. The gallium-containing hydrophobic electrospun layer or backing layer (BL) could mimic the epidermis of skin, avoiding fluid penetration and offering antibacterial activity. 3D printed FL contains catechol, gallium, and biologically active platelet rich fibrin (PRF) to adhere to both tissue and BL, show antibacterial activity, encourage angiogenesis, cell growth, and migration. The fabricated bioactive BSS exhibited noticeable adhesive properties (P ≤ 0.05), significant antibacterial activity (P ≤ 0.05), faster clot formation, and the potential to promote proliferation (P ≤ 0.05) and migration (P ≤ 0.05) of L929 cells. Furthermore, the angiogenesis was significantly higher (P ≤ 0.05) when evaluated in vivo and in ovo. The BSS-covered wounds healed faster due to low inflammation and high collagen density. Based on the obtained results, the fabricated bioactive BSS could be an effective treatment for infected burn wounds.

Wound Healing Performance in a Moist Environment of Crystalline Glucose/Mannose Film as a New Dressing Material Using a Rat Model: Comparing with Medical-Grade Wound Dressing and Alginate

Although medical wound dressings produced using hydrocolloids and alginate were effective in wound healing, adhesion at the wound site and the resulting delayed healing have been a problem. As a new wound dressing material, crystalline wound dressings produced from glucose/mannose were used in this study, which aimed to clarify the properties, adhesion reduction, and wound healing performance of a new wound dressing. Crystalline glucose/mannose films were obtained via alkali treatment using the solution casting method. The structure of the crystalline glucose/mannose films was analogous to the cellulose II polymorph, and the crystallinity decreased with time in hydrated conditions. The crystalline glucose/mannose films had adequate water absorption of 34 × 10-4 g/mm3 for 5 min. These allowed crystalline glucose/mannose films to remove excess wound exudates while maintaining a moist wound healing condition. This in vivo study demonstrated the healing effects of three groups, which were crystalline glucose/mannose group > alginate group > hydrocolloid group. At 1 week, the crystalline glucose/mannose group was also found to be non-adhesive to the portion of wound healing. This was evidenced by the earlier onset of the healing process, which assisted in re-epithelization and promotion of collagen formation and maturation. These results implied that crystalline glucose/mannose films were a promising candidate that could accelerate the wound healing process, compared with medical-grade wound dressing and alginate.

TiB2-Derived Nanosheets Enhance the Tensile Strength and Controlled Drug Release of Biopolymeric Films Used in Wound Healing

Wound healing using an alginate-based biopolymeric film is one of the most preferred treatments. However, these films lack mechanical strength (elasticity and tensile strength), show higher initial burst release, and exhibit high vapor permeability. The present study reports the development of nanosheets derived from titanium diboride (10 nm) (NTB)-incorporated biopolymeric films (0.025, 0.05, and 0.1% w/v) using sodium alginate (SA) and carboxymethyl cellulose (CMC) to overcome the shortfalls. The surface properties of the film, nanosheet distribution within the film, and possible interactions with the film are explored by using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), Fourier transform infrared (FTIR), and X-ray diffraction (XRD). These analyses confirm that nanosheets are uniformly distributed in the film and introduce unevenness on the film's surface. The tensile strength of the nanosheet-incorporated film (0.1% NTB film) using UTM is found to be 24.30 MPa (six times higher compared to the blank film), equivalent to human skin. The water vapor transmission rate of the film is also found to be in the desired range (i.e., 2000-2500 g/m2 day). The biocompatibility of the NTB film is confirmed by the MTT assay test using NIH/3T3 cells and HEK 293 cells. Furthermore, the scratch assay shows that the developed films promote cell migration and proliferation. The antibacterial activity of the film is also demonstrated using a model drug, tetracycline hydrochloride (TCl). Besides, the film exhibits the sustained release of TCl and follows the Korsmeyer-Peppas model for drug release. Overall, the 0.1% w/v NTB film is easy to fabricate, biocompatible and shows superior mechanical properties.

Versatile Liquid Metal/Alginate Composite Fibers with Enhanced Flame Retardancy and Triboelectric Performance for Smart Wearable Textiles

Liquid metal (LM) shows the superiority in smart wearable devices due to its biocompatibility and electromagnetic interference (EMI) shielding. However, LM based fibers that can achieve multifunctional integrated applications with biodegradability remain a daunting challenge. Herein, versatile LM based fibers are fabricated first by sonication in alginate solution to obtain LM micro/nano droplets and then wet-spinning into LM/alginate composite fibers. By mixing with high-concentration alginate solution (4-6 wt.%), the LM micro/nano droplets stability (colloidal stability for > 30 d and chemical stability for > 45 d) are not only improved, but also facilitate its spinning into fibers through bimetallic ions (e.g., Ga3+ and Ca2+ ) chelation strategy. These resultant fibers can be woven into smart textiles with excellent flexibility, air permeability, water/salt resistance, and high temperature tolerance (-196-150 °C). In addition, inhibition of smoldering result from the LM droplets and bimetallic ions is achieved to enhance flame retardancy. Furthermore, these fibers combine the exceptional properties of LM droplets (e.g., photo-thermal effect and EMI shielding) and alginate fibers (e.g., biocompatibility and biodegradability), applicable in wearable heating devices, wireless communication, and triboelectric nanogenerator, making it a promising candidate for flexible smart textiles.

Cartilage-inspired terpolymer hydrogel with excellent mechanical properties and superior lubricating ability

Osteoarthritis (OA), the most common degenerative joint disorder, seriously affects patients' daily activities. Recently, hydrogels, due to their similar structure to articular cartilage, have shown great potential as cartilage-repairing materials. In the present work, we developed a simple process for fabricating terpolymer [P(acrylamide-co-acrylic acid-co-2-acrylamido-2-methyl-1-propanesulfonic acid)/Fe3+] hydrogel [P(AAm-co-AAc-co-AMPS)/Fe3+]. The content of AMPS was found to show a crucial effect on the mechanical and tribological performance of the terpolymer hydrogel. When the content of AMPS was 0.45 mol L-1, the compressive strength, modulus, and friction coefficient of the terpolymer hydrogel were 66.60 ± 1.79 MPa, 2.10 ± 0.16 MPa, and 0.032, respectively. In addition, the hydrogel showed high wear durability and the friction coefficient was as low as 0.038 after 3.6 × 105 sliding cycles.

Strontium-doped mesoporous bioglass nanoparticles for enhanced wound healing with rapid vascularization

Tissue engineered skin and its substitutes have a promising future in wound healing. However, enabling fast formation of blood vessels during the wound healing process is still a huge challenge to the currently available wound substitutes. In this work, active mesoporous bioglass nanoparticles with a high specific surface area and doped with strontium (Sr) were fabricated for rapid microvascularization and wound healing. The as-prepared bioglass nanoparticles with Sr ions significantly promoted the proliferation of fibroblasts and microvascularization of human umbilical vein endothelial cells in vitro. Silk fibroin sponges encapsulating the nanoparticles accelerated wound healing by promoting the formation of blood vessels and epithelium in vivo. This work provides a strategy for the design and development of active biomaterials for enhancing wound healing by rapid vascularization and epithelial reconstruction.

A Review of Metal Nanoparticles Embedded in Hydrogel Scaffolds for Wound Healing In Vivo

An evolving field, nanotechnology has made its mark in the fields of nanoscience, nanoparticles, nanomaterials, and nanomedicine. Specifically, metal nanoparticles have garnered attention for their diverse use and applicability to dressings for wound healing due to their antimicrobial properties. Given their convenient integration into wound dressings, there has been increasing focus dedicated to investigating the physical, mechanical, and biological characteristics of these nanoparticles as well as their incorporation into biocomposite materials, such as hydrogel scaffolds for use in lieu of antibiotics as well as to accelerate and ameliorate healing. Though rigorously tested and applied in both medical and non-medical applications, further investigations have not been carried out to bring metal nanoparticle-hydrogel composites into clinical practice. In this review, we provide an up-to-date, comprehensive review of advancements in the field, with emphasis on implications on wound healing in in vivo experiments.

A DFT study of the gallium ion-binding capacity of mature Pseudomonas aeruginosa biofilm extracellular polysaccharide

Intravenous gallium therapy is a non-antibiotic approach to limit Pseudomonas aeruginosa biofilm proliferation, by outcompeting iron for siderophore binding. Gallium therapy represents a viable therapeutic strategy for cystic fibrosis (CF) patients harbouring mucoid P. aeruginosa biofilm lung infections. Siderophore deficient P. aeruginosa isolates still demonstrate a hindered biofilm proliferation when exposed to gallium but it is currently unknown whether exogenous gallium has any disruptive influence on the exopolysaccharide (EPS), the major mucoid P. aeruginosa CF lung biofilm matrix component. To that end, Density-Functional Theory (DFT) was deployed to assess whether gallium (Ga3+) could be substituted into the mature mucoid EPS scaffold in preference of calcium (Ca2+)-the native EPS cross-linking ion. Removal of the stable, bound native calcium ions offers a large enthalpic barrier to the substitution and the mature EPS fails to accommodate exogenous gallium. This suggests that gallium, perhaps, is utilising a novel, possibly unknown, ferric uptake system to gain entry to siderophore deficient cells.

Regenerated silk fibroin and alginate composite hydrogel dressings loaded with curcumin nanoparticles for bacterial-infected wound closure

It is important to treat a bacterial-infected wound with a hydrogel dressing due to its excellent biocompatibility and extracellular matrix mimicking structure. In this work, the antibacterial curcumin nanoparticles (Cur-NPs) loaded silk fibroin and sodium alginate (SF/SA) composite hydrogels have been developed as dressings for bacterial-infected wound closure. The as-prepared composite hydrogel dressings exhibited excellent biocompatibility and antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in vitro. In addition, the composite hydrogel dressings showed good tissue adhesive strength because of their high viscosity and abundance of amino groups distributed on SF, which can form multi-aldehyde polysaccharides with the tissue surface. The porous 3D structure of the composite hydrogel dressings facilitated the absorption of exudate from the wound site and promoted the fusion of cellular nutrients and metabolites. In the full-thickness skin defect model with and without bacterial infection, the Cur-NPs loaded SF/SA composite hydrogel dressings prominently improves the closure of bacterial-infected wounds by improving cell proliferation, anti-inflammatory properties, vascular remodeling, and collagen deposition.

An adhesive gelatin-coated small intestinal submucosa composite hydrogel dressing aids wound healing

It is a challenging clinical task to determine how to repair large-area skin defects better. Traditional wound dressings (e.g., cotton and gauze) can only be used as a dressing; consequently, there is an increasing demand for wound dressings with additional properties (i.e., antibacterial and pro-repair) in clinical practice. In this study, a composite hydrogel with o-nitrobenzene-modified gelatin-coated decellularized small intestinal submucosa (GelNB@SIS) was designed for the repair of skin injuries. SIS is a natural extracellular matrix with a 3D microporous structure and also contains high levels of growth factors and collagen. GelNB provides this material photo-triggering tissue adhesive property. The structure, tissue adhesion, cytotoxicity, and bioactivity to cells were investigated. Based on in vivo study and histological analysis, we found the combination of GelNB and SIS improved the healing process by promoting vascular renewal, dermal remodeling, and epidermal regeneration. Based on our findings, GelNB@SIS is a promising candidate for tissue repair applications.

Facile wound dressing replacement: Carbon dots for dissolving alginate hydrogels via competitive complexation

Dissolvable hydrogels have shown great potentials in removing the exudes and alleviating pain during wound dressing replacement. Herein, a series of carbon dots (CDs) composing high complexation ability with Cu²⁺ were prepared for capturing Cu²⁺ from Cu²⁺-alginate hydrogels. CDs were prepared using biocompatible lysine as the main starting material, while ethylenediamine was chosen as the other starting material for its extremely high complexation ability with Cu²⁺. The complexation ability increased with the increasing amount of ethylenediamine, while the cell viability decreased. When the mass ratio of ethylenediamine to lysine in CDs was above 1/4, six-coordinate copper centers could be formed. CD_1/4 at the concentration of 90 mg/mL could dissolve Cu²⁺-alginate hydrogels within 16 min, which was about twice faster than lysine. In vivo results showed the replaced hydrogels could ameliorate hypoxic conditions, alleviate local inflammatory reactions and promote the healing speed of burn wounds. Thus, the above results suggested the competitive complexation of CDs with Cu²⁺ could effectively dissolve Cu²⁺-alginate hydrogels, which have much potential in realizing facile wound dressing replacement.

A dual functional Ti-Ga alloy: inhibiting biofilm formation and osteoclastogenesis differentiation via disturbing iron metabolism

BACKGROUND

Although biomedical implants have been widely used in orthopedic treatments, two major clinical challenges remain to be solved, one is the bacterial infection resulting in biofilm formation, and the other is aseptic loosening during implantation due to over-activated osteoclastogenesis. These factors can cause many clinical issues and even lead to implant failure. Thus, it is necessary to endow implants with antibiofilm and aseptic loosening-prevention properties, to facilitate the integration between implants and bone tissues for successful implantation. To achieve this goal, this study aimed to develop a biocompatible titanium alloy with antibiofilm and anti-aseptic loosening dual function by utilizing gallium (Ga) as a component.

METHODS

A series of Ti-Ga alloys were prepared. We examined the Ga content, Ga distribution, hardness, tensile strength, biocompatibility, and anti-biofilm performance in vitro and in vivo. We also explored how Ga³⁺ ions inhibited the biofilm formation of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) and osteoclast differentiation.

RESULTS

The alloy exhibited outstanding antibiofilm properties against both S. aureus and E. coli in vitro and decent antibiofilm performance against S. aureus in vivo. The proteomics results demonstrated that Ga³⁺ ions could disturb the bacterial Fe metabolism of both S. aureus and E. coli, inhibiting bacterial biofilm formation. In addition, Ti-Ga alloys could inhibit receptor activator of nuclear factor-κB ligand (RANKL)-dependent osteoclast differentiation and function by targeting iron metabolism, then suppressing the activation of the NF-κB signaling pathway, thus, showing their potential to prevent aseptic loosening.

CONCLUSION

This study provides an advanced Ti-Ga alloy that can be used as a promising orthopedic implant raw material for various clinical scenarios. This work also revealed that iron metabolism is the common target of Ga³⁺ ions to inhibit biofilm formation and osteoclast differentiation.

Iron Acquisition and Metabolism as a Promising Target for Antimicrobials (Bottlenecks and Opportunities): Where Do We Stand?

The emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) infections is one of the most crucial challenges currently faced by the scientific community. Developments in the fundamental understanding of their underlying mechanisms may open new perspectives in drug discovery. In this review, we conducted a systematic literature search in PubMed, Web of Science, and Scopus, to collect information on innovative strategies to hinder iron acquisition in bacteria. In detail, we discussed the most interesting targets from iron uptake and metabolism pathways, and examined the main chemical entities that exhibit anti-infective activities by interfering with their function. The mechanism of action of each drug candidate was also reviewed, together with its pharmacodynamic, pharmacokinetic, and toxicological properties. The comprehensive knowledge of such an impactful area of research will hopefully reflect in the discovery of newer antibiotics able to effectively tackle the antimicrobial resistance issue.

A review on the synthesis and development of alginate hydrogels for wound therapy

Convenient and low-cost dressings can reduce the difficulty of wound treatment. Alginate gel dressings have the advantages of low cost and safe usage, and they have obvious potential for development in biomedical materials. Alginate gel dressings are currently a research area of great interest owing to their versatility, intelligent, and their application attempts in treating complex wounds. We present a detailed summary of the preparation of alginate hydrogels and a study of their performance improvement. Herein, we summarize the various applications of alginate hydrogels. The research focuses in this area mainly include designing multifunctional dressings for the treatment of various wounds and fabricating specialized dressings to assist physicians in the treatment of complex wounds (TOC). This review gives an outlook for future directions in the field of alginate hydrogel dressings. We hope to attract more research interest and studies in alginate hydrogel dressings, thus contributing to the creation of low-cost and highly effective wound treatment materials.

Polysaccharide-Based Multifunctional Hydrogel Bio-Adhesives for Wound Healing: A Review

Wound healing is a long-term and complex biological process that involves multiple hemostasis, inflammation, proliferation, and remodeling stages. In order to realize comprehensive and systematic wound management, appropriate wound treatment bio-adhesives are urgently needed. Hydrogel bio-adhesives have excellent properties and show unique and remarkable advantages in the field of wound management. This review begins with a detailed description of the design criteria and functionalities of ideal hydrogel bio-adhesives for wound healing. Then, recent advances in polysaccharide-based multifunctional hydrogel bio-adhesives, which involve chitosan, hyaluronic acid, alginate, cellulose, dextran, konjac glucomannan, chondroitin sulfate, and other polysaccharides, are comprehensively discussed. Finally, the current challenges and future research directions of polysaccharide-based hydrogel bio-adhesives for wound healing are proposed to stimulate further exploration by researchers.

Self-assembled hyaluronic acid-coated nanocomplexes for targeted delivery of curcumin alleviate acute kidney injury

Acute kidney injury (AKI) is a pathological process with high morbidity, and drug resistance is easy to occur due to untargeted drug therapy. Curcumin can repair acute kidney injury. The expression of the CD44 receptor in renal tubular epithelial cells is abnormally elevated during AKI, and hyaluronic acid (HA) has the ability to bind specifically to the CD44 receptor. In this study, we developed a hyaluronic acid-coated liposome (HALP) nanocomplexes that targeted renal epithelial cells and its effect of relieving AKI was investigated. HALP was formed by self-assembly through the electrostatic interaction of curcumin-loaded cationic liposomes (LP) with hyaluronic acid and responds to the release of curcumin in the acidic microenvironment of lesions to treat AKI. HALP had good stability and biocompatibility. The in vitro results showed that compared to LP, HALP exhibited higher antioxidant, anti-inflammatory, and anti-apoptotic capacities. The AKI model suggested that HALP could not only target and accumulate in the injured kidney but also had an excellent ability to reduce the inflammatory response, which decreased tubular necrosis and restored kidney function.

Gallium-modified gelatin nanoparticles loaded with quercetin promote skin wound healing via the regulation of bacterial proliferation and macrophage polarization

Background: Wound healing is a complicated process involving multiple cell components and can help the re-establishment of the skin's barrier function. Previous studies have pointed out that bacterial infection and sustained inflammatory reactions are the main causes of the delay of wound closure and scar formation during wound healing. The effect of current approaches for scar-free wound repair still faces many challenges, and alternative therapeutic methods are urgently needed to be established. Methods: The basic characteristics of the new-designed nanoparticles were clarified through the characterization of the material. The biocompatibility of the nanoparticles, as well as its effect on fibroblast function, anti-bacterial capacity, inflammation suppressive role, and the underlying mechanism were further verified by a panel of biochemical assays in vitro. Ultimately, pre-clinical rat model was employed to testify its role in wound healing and scar formation in vivo. Results: Firstly, gallium-modified gelatin nanoparticles loaded with quercetin was successfully established, displaying good biocompatibility and facilitative effect on fibroblast function. In addition, the nanoparticles showed prominent anti-bacterial and inflammation-suppressive effects. What's more important, the nanoparticles could also induce the polarization of macrophages from M1 to M2 phenotype to exert its inflammatory inhibitory role through TGF-β/Smad signaling pathway. Ultimately, in vivo experiment showed that the nanoparticles could effectively promote wound repair and inhibit scar formation during the process of wound healing. Conclusion: Taken together, the new nanoparticles have good anti-bacterial and anti-scar formation effects and great potential in the field of skin wound repair, which provides a promising therapeutic strategy for wound treatment.

A Dual-Crosslinked Hydrogel Based on Gelatin Methacryloyl and Sulfhydrylated Chitosan for Promoting Wound Healing

The skin is the largest organ of the human body. Skin injuries, especially full-thickness injuries, are a major treatment challenge in clinical practice. Therefore, wound dressing materials with therapeutic effects have great practical significance in healthcare. This study used photocrosslinkable gelatin methacryloyl (GelMA) and sulfhydrylated chitosan (CS-SH) to design a double-crosslinked hydrogel for wound dressing. When crosslinked together, the resulting hydrogels showed a highly porous inner structure, and enhanced mechanical properties and moisture retention capacity. The compression modulus of the GelMA/CS-SH hydrogel (GCH) reached up to about 40 kPa and was much higher than that of pure GelMA hydrogel, and the compression modulus was increased with the amount of CS-SH. In vitro study showed no cytotoxicity of obtained hydrogels. Interestingly, a higher concentration of CS-SH slightly promoted the proliferation of cells. Moreover, the double-crosslinked hydrogel exhibited antibacterial properties because of the presence of chitosan. In vivo study based on rats showed that full-thickness skin defects healed on the 15th day. Histological results indicate that the hydrogel accelerated the repair of hair follicles and encouraged the orderly growth of collagen fibers in the wound. Furthermore, better blood vessel formation and a higher expression of VEGFR were observed in the hydrogel group when compared with the untreated control group. Based on our findings, GCH could be a promising candidate for full-thickness wound dressing.

Supramolecular Hydrogel Dressing: Effect of Lignin on the Self-Healing, Antibacterial, Antioxidant, and Biological Activity Improvement

The functionalization and performance improvement of supramolecular hydrogels are very important for their application in the wound dressing field. Inspired by the role of lignin in plant cell walls, sulfonated lignin is introduced into the supramolecular hydrogel to improve functionality, mechanical strength, and biological activity. According to the chemical structure characteristics of the sulfonated lignin and the requirements for wound dressing, a novel polymer system is designed and successfully synthesized to cooperate with the sulfonated lignin to form the supramolecular hydrogel dressings. The introduction of the sulfonated lignin can effectively improve the mechanical strength, self-healing property, antioxidant activity, and biological activity of the obtained supramolecular hydrogel dressings. In the rat wound healing model experiment, the supramolecular hydrogel dressings can maintain the moist environment on the wound surface, clean up the excretion of wound tissue, promote wound healing, and reduce the occurrence of inflammation. This supramolecular hydrogel dressing shows obvious potential for wound management and treatment by a facile and effective approach and has great promise for long-term application of wound dressings. This strategy for designing polymers according to the chemical structure characteristics of the sulfonated lignin and the application requirements has reference value for further development of biomass-based compound materials.

Mechanobactericidal, Gold Nanostar Hydrogel-Based Bandage for Bacteria-Infected Skin Wound Healing

The emergence of multidrug resistant (MDR) microorganisms has led to the development of alternative approaches for providing relief from microbial attacks. The mechano-bactericidal action as a substitute for antimicrobials has become the focus of intensive research. In this work, nanostructure-conjugated hydrogel are explored as a flexible dressing against Staphylococcus aureus (S. aureus)-infected skin wounds. Herein gold nanostars (AuNst) with spike lengths reaching 120 nm are probed for antibacterial action. The bacterial killing of >95% is observed for Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli), while up to 60% for Gram-positive S. aureus. AuNst conjugated hydrogel (AuNst₁₂₀@H) reduced >80% colonies of P. aeruginosa and E. coli. In comparison, around 35.4% reduction of colonies are obtained for S. aureus. The viability assay confirmed the presence of about 85% of living NIH-3T3 cells when grown with hydrogels. An animal wound model is also developed to assess the efficiency of AuNst₁₂₀@H. A significant reduction in wound size is observed on the 10th day in AuNst₁₂₀@H treated animals with fully formed epidermal layers, hair follicles, new blood vessels, and arrector muscles. These findings suggest that novel dressing materials can be developed with antimicrobial nanotextured surfaces.

Effects and Progress of Photo-Crosslinking Hydrogels in Wound Healing Improvement

Wound healing is a dynamic physiological process, including three stages: inflammation, tissue formation, and remodeling. The quality of wound healing is affected by many topical and systemic factors, while any small factor may affect the process. Therefore, improving the quality of wound healing is a complex and arduous challenge. Photo-crosslinking reaction using visible light irradiation is a novel method for hydrogel preparation. Photo-crosslinking hydrogels can be controlled in time and space, and are not interfered by temperature conditions, which have been widely used in the fields of medicine and engineering. This review aims to summarize the application of photo-crosslinking hydrogels in improving the quality of wound healing, mainly including the material design, application mechanism, and effect of photo-crosslinking hydrogels applied in wound healing, followed by the applicable animal models for experimental research. Finally, this review analyzes the clinical application prospects of photo-crosslinking hydrogels in the field of wound healing.

Calcium alginate/PNIPAAm hydrogel with body temperature response and great biocompatibility: Application as burn wound dressing

Deep burns often do not heal easily, because the dermis of the skin is severely damaged, leading to severe inflammation and bacterial infection. Therefore, it is of great clinical significance to develop a dressing that promotes the healing process of deep burn wound. In this study, we used N-isopropyl acrylamide, sodium alginate and calcium chloride as the main materials, a series of calcium alginate/ poly (N-isopropyl acrylamide)(NIPAAm) hydrogel (CAPH) with different component ratios were synthesized. Its swelling properties, temperature response properties, rheological properties, biocompatibility properties, and in vitro drug release properties were investigated. Based on the above conditions, the CAPH(sodium alginate:NIPAAm = 2:15) with the best comprehensive performance was selected, which has a good biocompatibility. In addition, 0.02 % (w/v) mupirocin was loaded in CAPH. The temperature-responsive property of PNIPAAm in CAPH at 34 °C not only allowed the CAPH to rapidly release the drug under to prevent infection, but also to assist in wound contraction. Application of CAPH to localized wounds of deep second-degree burns in mice showed a faster healing rate and tissue regeneration. At the same time, collagen recovery was enhanced, collagen bundles were arranged in an orderly manner, and the scarring was not obvious after 16 days. Therefore, this research prepared a new safe and effective biomaterial.