Injectable Adhesive Self-Healing Multicross-Linked Double-Network Hydrogel Facilitates Full-Thickness Skin Wound Healing

Recombinant Humanized Collagen Type XVII Promotes Oral Ulcer Healing via Anti-Inflammation and Accelerate Tissue Healing

Introduction

Recombinant humanized collagen, as a novel biomaterial, exhibits multiple excellent biological functions, such as inhibition of inflammation, promotion of cell proliferation and vascular proliferation, and promotion of tissue healing. However, there is a lack of conclusive evidence regarding the specific role of recombinant humanized collagen type 17 (rhCol 17) in oral ulcer healing. This study explored whether rhCol 17 could promote the proliferation of human gingival fibroblasts (HGFs) and inhibit its inflammation, and whether it could promote the healing of oral ulcers in rats by inhibiting inflammation and accelerating tissue healing.

Methods

At the cellular level, we investigated the effect of rhCol 17 on the proliferation of (HGFs) by CCK8; HGFs were mixed with lipopolysaccharide (LPS) to investigate the effect of rhCol 17 on HGFs in an inflammatory state. Eighteen adult male Sprague-Dawley rats were randomly distributed into three groups: blank control group, carbomer group (carbomer sprayed only), and rhCol 17 group (carbomer containing rhCol 17 sprayed), 1 time/day. The samples were collected at D3 and D5. At completion, histological staining and PCR were carried out to study its effect on the healing of oral ulcers in rats.

Results

Through cellular experiments, we found that rhCol 17 possesses good biocompatibility and anti-inflammatory properties, and can effectively promote the proliferation and migration of HGFs, as well as significantly reduce the inflammation level of the cells. The animal experimental results showed that rhCol 17 could significantly reduce the inflammation level, promote collagen deposition and angiogenesis at the ulcer site, thus effectively accelerating the healing of oral ulcers in rats.

Conclusion

In summary, the collagen sprays containing rhCol 17 have excellent anti-inflammatory effects and could accelerate tissue healing and are expected to provide a new effective treatment for patients with recurrent oral ulcers.

Overview of Dynamic Bond Based Hydrogels for Reversible Adhesion Processes

Polymeric hydrogels are soft materials with a three-dimensional (3D) hydrophilic network capable of retaining and absorbing large amounts of water or biological fluids. Due to their customizable properties, these materials are extensively studied for developing matrices for 3D cell culture scaffolds, drug delivery systems, and tissue engineering. However, conventional hydrogels still exhibit many drawbacks; thus, significant efforts have been directed towards developing dynamic hydrogels that draw inspiration from organisms' natural self-repair abilities after injury. The self-healing properties of these hydrogels are closely associated with their ability to form, break, and heal dynamic bonds in response to various stimuli. The primary objective of this review is to provide a comprehensive overview of dynamic hydrogels by examining the types of chemical bonds associated with them and the biopolymers utilized, and to elucidate the chemical nature of dynamic bonds that enable the modulation of hydrogels' properties. While dynamic bonds ensure the self-healing behavior of hydrogels, they do not inherently confer adhesive properties. Therefore, we also highlight emerging approaches that enable dynamic hydrogels to acquire adhesive properties.

Harnessing the potential of hydrogels for advanced therapeutic applications: current achievements and future directions

The applications of hydrogels have expanded significantly due to their versatile, highly tunable properties and breakthroughs in biomaterial technologies. In this review, we cover the major achievements and the potential of hydrogels in therapeutic applications, focusing primarily on two areas: emerging cell-based therapies and promising non-cell therapeutic modalities. Within the context of cell therapy, we discuss the capacity of hydrogels to overcome the existing translational challenges faced by mainstream cell therapy paradigms, provide a detailed discussion on the advantages and principal design considerations of hydrogels for boosting the efficacy of cell therapy, as well as list specific examples of their applications in different disease scenarios. We then explore the potential of hydrogels in drug delivery, physical intervention therapies, and other non-cell therapeutic areas (e.g., bioadhesives, artificial tissues, and biosensors), emphasizing their utility beyond mere delivery vehicles. Additionally, we complement our discussion on the latest progress and challenges in the clinical application of hydrogels and outline future research directions, particularly in terms of integration with advanced biomanufacturing technologies. This review aims to present a comprehensive view and critical insights into the design and selection of hydrogels for both cell therapy and non-cell therapies, tailored to meet the therapeutic requirements of diverse diseases and situations.

Facile Solvent-Free Fabrication of All-Small-Molecule Supramolecular Photothermal Bioadhesive for Sutureless Wound Closure

Achieving underwater adhesion possesses a significant challenge, primarily due to the presence of interfacial water, which restricts the potential applications of adhesives. In this study, we present a straightforward and environmentally friendly one-pot approach for synthesizing a solvent-free supramolecular TPFe bioadhesive composed of thioctic acid, proanthocyanidins, and FeCl3. The bioadhesive exhibits excellent biocompatibility and photothermal antibacterial properties and demonstrates effective adhesion on various substrates in both wet and dry environments. Importantly, the adhesive strength of this bioadhesive on steel exceeds 1.2 MPa and that on porcine skin exceeds 100 kPa, which is greater than the adhesive strength of most reported bioadhesives. In addition, the bioadhesive exhibits the ability to effectively halt bleeding, close wounds promptly, and promote wound healing in the rat skin wound model. Therefore, the TPFe bioadhesive has potential as a medical bioadhesive for halting bleeding quickly and promoting wound healing in the biomedical field. This study provides a new idea for the development of bioadhesives with firm wet adhesion.

Injectable bio-multifunctional hyaluronic acid-based hydrogels loaded with poly ADP-ribose polymerase inhibitors for ovarian cancer therapy

The recent use of PARP inhibitors (PARPi) in the maintenance treatment of ovarian tumor has significantly improved the survival rates of cancer patients. However, the current oral administration of PARP inhibitors fails to realize optimal therapeutic effects due to the low bioavailability in cancerous tissues, and often leads to a range of systemic adverse effects including hematologic toxicities, digestive system reactions, and neurotoxicities. Therefore, the demand for an advanced drug delivery system that can ensure effective drug administration while minimizing these unfavorable reactions is pressing. Injectable hydrogel emerges as a promising solution for local administration with the capability of sustainable drug release. In this study, we developed an injectable hydrogel made from aminated hyaluronic acid and aldehyde-functionalized pluronic127 via Schiff base reaction. This hydrogel exhibits excellent injectability with short gelation time and remarkable self-healing ability, and is applied to load niraparib. The drug-loaded hydrogel (HP@Nir hydrogel) releases drugs sustainably as tested in vitro as well as displays significant anti-proliferation and anti-migratory properties on human epithelial ovarian cancer cell line. Notably, HP@Nir hydrogel effectively suppresses the growth of ovarian cancer, without significant adverse reactions as demonstrated in animal studies. Additionally, the developed hydrogel is gradually degraded in vivo for around 20 d, while maintaining good biocompatibility. Overall, the injectable hydrogel loaded with niraparib provides a secure and efficient strategy for the treatment and management of ovarian cancer.

A Novel Food Bore Protein Hydrogel with Silver Ions for Promoting Burn Wound Healing

Hydrogels have emerged as a promising option for treating local scald wounds due to their unique physical and chemical properties. This study aims to evaluate the efficacy of ovalbumin/gelatin composite hydrogels in repairing deep II-degree scald wounds using a mouse dorsal skin model. Trauma tissues collected at various time points are analyzed for total protein content, hydroxyproline content, histological features, and expression of relevant markers. The results reveal that the hydrogel accelerates the healing process of scalded wounds, which is 17.27% higher than the control group. The hydrogel treatment also effectively prevents wound enlargement and redness of the edges caused by infection during the initial stage of scalding. The total protein and hydroxyproline content of the treated wounds are significantly elevated. Additionally, the hydrogel up-regulates the expression of VEGF (a crucial angiogenic factor) and down-regulates CD68 (a macrophage marker). In summary, this study provides valuable insights into the potential of multifunctional protein-based hydrogels in wound healing.

A hyaluronic acid hydrogel as a mild photothermal antibacterial, antioxidant, and nitric oxide release platform for diabetic wound healing

Hyaluronic acid (HA)-based biopolymer hydrogels are promising therapeutic dressings for various wounds but still underperform in treating diabetic wounds. These wounds are extremely difficult to heal and undergo a prolonged and severe inflammatory process due to bacterial infection, overexpression of reactive oxygen species (ROS), and insufficient synthesis of NO. In this study, a dynamic crosslinked hyaluronic acid (HA) hydrogel dressing (Gel-HAB) loaded with allomelanin (AMNP)-N, N'-dis-sec-butyl-N, N'-dinitroso-1, 4-phenylenediamine (BNN6) nanoparticles (AMNP-BNN6) was developed for healing diabetic wounds. The dynamic acylhydrazone bond formed between hydrazide-modified HA (HA-ADH) and oxidized HA (OHA) makes the hydrogel injectable, self-healing, and biocompatible. The hydrogel, loaded with AMNP-BNN6 nanoparticles, exhibits promising ROS scavenging ability and on-demand release of nitric oxide (NO) under near-infrared (NIR) laser irradiation to achieve mild photothermal antibacterial therapy (PTAT) (∼ 48 °C). Notably, the Gel-HAB hydrogel effectively reduced the oxidative stress level, controlled infections, accelerated vascular regeneration, and promoted angiogenesis, thereby achieving rapid healing of diabetic wounds. The injectable self-healing nanocomposite hydrogel could serve as a mild photothermal-enhanced antibacterial, antioxidant, and nitric oxide release platform for the treatment of diabetic wounds.

Multifunctional polypeptide-based hydrogel bio-adhesives with pro-healing activities and their working principles

Wound healing is a complex physiological process involving hemostasis, inflammation, proliferation, and tissue remodeling. Therefore, there is an urgent need for suitable wound dressings for effective and systematical wound management. Polypeptide-based hydrogel bio-adhesives offer unique advantages and are ideal candidates. However, comprehensive reviews on polypeptide-based hydrogel bio-adhesives for wound healing are still lacking. In this review, the physiological mechanisms and evaluation parameters of wound healing were first described in detail. Then, the working principles of hydrogel bio-adhesives were summarized. Recent advances made in multifunctional polypeptide-based hydrogel bio-adhesives involving gelatin, silk fibroin, fibrin, keratin, poly-γ-glutamic acid, ɛ-poly-lysine, serum albumin, and elastin with pro-healing activities in wound healing and tissue repair were reviewed. Finally, the current status, challenges, developments, and future trends of polypeptide-based hydrogel bio-adhesives were discussed, hoping that further developments would be stimulated to meet the growing needs of their clinical applications.

Facile synthesis of 2-hydroxy-β-cyclodextrin/polyacrylamide/carbazole hydrogel and its application for the treatment of infected wounds in a murine model

This work aimed to synthesize hydrogels by combining carbazole (Carb) with 2-hydroxy, β-cyclodextrin (HPβCD)/polyacrylamide (PAA) hybrid complexes. The hydrogels were then evaluated for their potential use in treating infected wounds. The physicochemical structures of the preparations were evaluated using several characterization methods including FTIR, FESEM, EDX, XRD, pH sensitivity, and TGA. Moreover, In vitro release, toxicity, antibacterial activity and in vivo infected wound healing activity were evaluated. Physicochemical testing verified the effective synthesis of the preparations and the timely release of Carb. The P(AA-co-AM)/HPβCD material exhibited an open structure characterized by macroscopic voids, whereas the hydrogels displayed surfaces that were not uniform. The FTIR analysis revealed the creation of a novel polymeric hydrogel composed of HPβCD as the main polymer structure. The hydrogels exhibited good reversible swelling and recoverable deformation, with an optimal swelling ratio of 30.12 achieved at pH 7.4. The antibacterial and safety of the formulations were validated by in vitro studies. β.Dex/PAA/Carb hydrogels have been shown to effectively expedite the healing of infected wounds by promoting the production of CD31, FGF-2, and COL1A, while reducing the levels of ROS, CD68, COX-2, and NF-κB. Overall, the combination of Carb, β.Dex, and PAA molecules had a synergistic impact on the healing process of infected wounds.

Thermoresponsive in situ forming and self-healing double-network hydrogels as injectable dressings for silymarin/levofloxacin delivery for treatment of third-degree burn wounds

Our study aimed to introduce a novel double-cross-linked and thermoresponsive hydrogel with remarkable potential for accelerating third-degree burn wound healing. Burn injuries are recognized as challenging, critical wounds. Especially in third-degree burns, treatment is demanding due to extended wounds, irregular shapes, significant exudation, and intense pain during dressing changes. In this work, hydrogels made of zwitterionic chitosan and dialdehyde starch (ZCS and ZDAS) were created to deliver silymarine (SM) and levofloxacin (LEV). The hydrogels were effortlessly produced using dynamic Schiff base linkages and ionic interactions between ZCS and ZDAS at appropriate times. The pore uniformity, gel fraction, and commendable swelling properties can imply a suitable degree of Schiff base cross-link. The hydrogel demonstrated outstanding shape retention, and significant self-healing and flexibility abilities, enabling it to uphold its form even during bodily movements. After injecting biocompatible hydrogel on the wound, a notable acceleration in wound closure was observed on day 21 (98.1 ± 1.10 %) compared to the control group (75.1 ± 6.13 %), and histopathological analysis revealed a reduction of inflammation that can be linked to remarkable antioxidant and antibiotic properties. The results demonstrate the hydrogel's efficacy in promoting burn wound healing, making it a promising candidate for medical applications.

A Multifunctional Herb-Derived Glycopeptide Hydrogel for Chronic Wound Healing

Chronic wounds constitute an increasingly prevalent global healthcare issue, characterized by recurring bacterial infections, pronounced oxidative stress, compromised functionality of immune cells, unrelenting inflammatory reactions, and deficits in angiogenesis. In response to these multifaceted challenges, the study introduced a stimulus-responsive glycopeptide hydrogel constructed by oxidized Bletilla striata polysaccharide (OBSP), gallic acid-grafted ε-Polylysine (PLY-GA), and paeoniflorin-loaded micelles (MIC@Pae), called OBPG&MP. The hydrogel emulates the structure of glycoprotein fibers of the extracellular matrix (ECM), exhibiting exceptional injectability, self-healing, and biocompatibility. It adapts responsively to the inflammatory microenvironment of chronic wounds, sequentially releasing therapeutic agents to eradicate bacterial infection, neutralize reactive oxygen species (ROS), modulate macrophage polarization, suppress inflammation, and encourage vascular regeneration and ECM remodeling, playing a critical role across the inflammatory, proliferative, and remodeling phases of wound healing. Both in vitro and in vivo studies confirmed the efficacy of OBPG&MP hydrogel in regulating the wound microenvironment and enhancing the regeneration and remodeling of chronic wound skin tissue. This research supports the vast potential for herb-derived multifunctional hydrogels in tissue engineering and regenerative medicine.

Tough, self-healing and injectable dynamic nanocomposite hydrogel based on gelatin and sodium alginate

Biomacromolecules based injectable and self-healing hydrogels possessing high mechanical properties have widespread potential in biomedical field. However, dynamic features are usually inversely proportional to toughness. It is challenging to simultaneously endow these properties to the dynamic hydrogels. Here, we fabricated an injectable nanocomposite hydrogel (CS-NPs@OSA-l-Gtn) stimultaneously possessing excellent autonomous self-healing performance and high mechanical strength by doping chitosan nanoparticles (CS-NPs) into dynamic polymer networks of oxidized sodium alginate (OSA) and gelatin (Gtn) in the presence of borax. The synergistic effect of the multiple reversible interactions combining dynamic covalent bonds (i.e., imine bond and borate ester bond) and noncovalent interactions (i.e., electrostatic interaction and hydrogen bond) provide effective energy dissipation to endure high fatigue resistance and cyclic loading. The dynamic hydrogel exhibited excellent mechanical properties like maximum 2.43 MPa compressive strength, 493.91 % fracture strain, and 89.54 kJ/m3 toughness. Moreover, the integrated hydrogel after injection and self-healing could withstand 150 successive compressive cycles. Besides, the bovine serum albumin embedded in CS-NPs could be sustainably released from the nanocomposite hydrogel for 12 days. This study proposes a novel strategy to synthesize an injectable and self-healing hydrogel combined with excellent mechanical properties for designing high-strength natural carriers with sustained protein delivery.

Silver-infused lysine crosslinked hydrogel with oxidized regenerated cellulose for prospective advanced wound dressings

The study aimed to develop a multifunctional wound dressing with enhanced antibacterial properties and wound healing promotion. The synthesis process involved preparing oxidized regenerated cellulose (ORC) following a modified procedure, synthesizing chitosan/silver nanoparticles (CS/Ag NPs) via an in-situ reduction method, and subsequently preparing ORC/CS/Lys@Ag NPs hydrogels. Characterization techniques including FTIR, XRD, SEM, and EDS were employed to analyze functional groups, lattice structure, morphology, and elemental composition. Gelation time, swelling behavior, water retention, mechanical properties, viscosity, self-healing capacity, rheological behavior, oxygen permeability, in vitro degradation, release of Ag+, and antibacterial properties were evaluated using various experimental methods. Results indicated that the novel wound dressing has the capability to evenly distribute Ag NPs to effectively counteract bacteria. It can maintain moist conditions for 86 h, resist a sturdy mechanical pressure of 11.3 KPa, and degrade by 11.045 % ± 0.429 within 8 h. Combining its efficient gas exchange abilities, self-repairing function, and biocompatibility, almost full recovery was observed in injured mouse skin within 13 days, highlighting its promising clinical utility.

Advancements and Challenges in Self-Healing Hydrogels for Wound Care

This manuscript explores self-healing hydrogels as innovative solutions for diverse wound management challenges. Addressing antibiotic resistance and tailored wound care, these hydrogels exhibit promising outcomes, including accelerated wound closure and tissue regeneration. Advancements in multifunctional hydrogels with controlled drug release, antimicrobial properties, and real-time wound assessment capabilities signal a significant leap toward patient-centered treatments. However, challenges such as scalability, long-term safety evaluation, and variability in clinical outcomes persist. Future directions emphasize personalized medicine, manufacturing innovation, rigorous evaluation through clinical trials, and interdisciplinary collaboration. This manuscript features the ongoing pursuit of effective, adaptable, and comprehensive wound care solutions to transform medical treatments and improve patient outcomes.

Flexible Organic Photovoltaic-Powered Hydrogel Bioelectronic Dressing With Biomimetic Electrical Stimulation for Healing Infected Diabetic Wounds

Electrical stimulation (ES) is proposed as a therapeutic solution for managing chronic wounds. However, its widespread clinical adoption is limited by the requirement of additional extracorporeal devices to power ES-based wound dressings. In this study, a novel sandwich-structured photovoltaic microcurrent hydrogel dressing (PMH dressing) is designed for treating diabetic wounds. This innovative dressing comprises flexible organic photovoltaic (OPV) cells, a flexible micro-electro-mechanical systems (MEMS) electrode, and a multifunctional hydrogel serving as an electrode-tissue interface. The PMH dressing is engineered to administer ES, mimicking the physiological injury current occurring naturally in wounds when exposed to light; thus, facilitating wound healing. In vitro experiments are performed to validate the PMH dressing's exceptional biocompatibility and robust antibacterial properties. In vivo experiments and proteomic analysis reveal that the proposed PMH dressing significantly accelerates the healing of infected diabetic wounds by enhancing extracellular matrix regeneration, eliminating bacteria, regulating inflammatory responses, and modulating vascular functions. Therefore, the PMH dressing is a potent, versatile, and effective solution for diabetic wound care, paving the way for advancements in wireless ES wound dressings.

Multifunctional chitosan-based hydrogel wound dressing loaded with Acanthopanax senticosus and Osmundastrum cinnamomeum: Preparation, characterization and coagulation mechanism

Considerable potential exists for the development of natural polymer hydrogels that possess notable antibacterial and anti-inflammatory properties, along with excellent biocompatibility and mechanical attributes, to expedite the healing of skin wounds. Recent endeavors have focused on formulating an optimal hydrogel dressing for wound hemostasis and repair. In this pursuit, we have crafted a composite hydrogel using carboxymethyl chitosan and alginic acid, cross-linked with EDC/NHS, and enriched with extracts from Acanthopanax senticosus and Osmundastrum cinnamomeum. This synthesized hydrogel showcases commendable features, including significant swelling capacity (135 ± 3.6%), proficient water retention (94.421 ± 0.154%), and effective water vapor permeability (5845.011 ± 467.799 g/m2/d). Moreover, our drug-loaded hydrogels (CMCS/SA/AS/OC) have demonstrated remarkable efficacy in accelerating wound healing in both in vivo and in vitro models. On the 7th day, the wound healing rate reached 94.905% ± 0.498%, and by the 14th day, the wound was nearly fully healed (98.08% ± 0.323%) with the emergence of hair coverage. Furthermore, these hydrogels exhibited remarkable hemostatic properties, the platelet activity was 89.37% ± 1.29% and the platelet adhesion rate was 66.36% ± 1.42%. In order to elucidate the coagulation mechanism of the Acanthopanax senticosus and Osmundastrum cinnamomeum extracts, a network pharmacology approach was carried out. 41 active compounds and 107 potential therapeutic targets associated with these extracts were identified, revealing a total of 132 coagulation pathways. Platelet activation and complement and coagulation cascades pathways showed the highest levels of enrichment by KEGG analysis, serving as potential mechanisms through which the active components in AS/OC may facilitate coagulation by targeting relevant factors. In summary, our study has successfully developed an innovative drug-loaded hydrogel that not only enhances wound hemostasis and healing but also provides insights into the underlying mechanisms through network pharmacology. This work establishes a robust theoretical foundation for the medical application of our hydrogel.

Photopolymerized multifunctional sodium alginate-based hydrogel for antibacterial and coagulation dressings

Trauma caused by tissue damage in clinical applications has posed a serious threat to public safety. Dressings with a single function cannot meet the needs of wound healing, but multifunctional dressings are difficult to achieve and obtain. To address this issue, this research designed a facile one-pot photo-crosslinking method to prepare multifunctional sodium alginate-based hydrogel dressings for effective wound healing. According to irregular wounds, sodium alginate-based hydrogel dressings can be quickly prepared anytime and anywhere. The structure and physicochemical properties of hydrogels are regulated by modulating the proportion of main components sodium alginate and acrylamide. The results showed the sodium alginate-based composite hydrogel as a candidate multifunctional dressing that exhibits excellent stretchability and compressibility, viscoelasticity, and suitable tissue-like adhesion. In vitro drug release and antibacterial experiments indicated that the hydrogel has effective antibacterial properties against S. aureus and P. aeruginosa. Furthermore, the haemostatic behaviour of the hydrogel was demonstrated using the coagulation activation test, whole blood-clotting test, and blood cell and platelet adhesion experiments. All these results demonstrated that the sodium alginate-based hydrogel had high application potential as a multifunctional medical dressing for wound healing.

Pluronic F127-Lipoic Acid Adhesive Nanohydrogel Combining with Ce3+/Tannic Acid/Ulinastatin Nanoparticles for Promoting Wound Healing

Developing strong anti-inflammatory wound dressings is of great significance for protecting inflammatory cutaneous wounds and promoting wound healing. The present study develops a nanocomposite Pluronic F127 (F127)-based hydrogel dressing with injectable, tissue adhesive, and anti-inflammatory performance. Briefly, Ce3+/tannic acid/ulinastatin nanoparticles (Ce3+/TA/UTI NPs) are fabricated. Meanwhile, α-lipoic acid is bonded to the ends of F127 to prepare F127-lipoic acid (F127LA) and its nanomicelles. Due to the gradual viscosity change instead of mutation during phase transition, the mixed Ce3+/TA/UTI NPs and F127LA nanomicelles show well-performed injectability at 37 °C and can form a semisolid composite nanohydrogel that can tightly attach to the skin at 37 °C. Furthermore, ultraviolet (UV) irradiation without a photoinitiator transforms the semisolid hydrogel into a solid hydrogel with well-performed elasticity and toughness. The UV-cured composite nanohydrogel acts as a bioadhesive that can firmly adhere to tissues. Due to the limited swelling property, the hydrogel can firmly adhere to tissues in a wet environment, which can seal wounds and provide a reliable physical barrier for the wounds. Ce3+/TA/UTI NPs in the hydrogel exhibit lipopolysaccharide (LPS)-scavenging ability and reactive oxygen species (ROS)-scavenging ability and significantly reduce the expression of inflammatory factors in wounds at the early stage, accelerating LPS-induced wound healing.

An Injectable Composite Hydrogel of Verteporfin-Bonded Carboxymethyl Chitosan and Oxidized Sodium Alginate Facilitates Scarless Full-Thickness Skin Regeneration

Full-thickness skin defect has always been a major challenge in clinics due to fibrous hyperplasia in the repair process. Hydrogel composite dressings loaded with anti-fibrotic drugs have been considered as a promising strategy for scarless skin regeneration. In this work, a hydrogel composite (VP-CMCS-OSA) of carboxymethyl chitosan (CMCS) and oxidized sodium alginate (OSA), with loading anti-fibrotic drug verteporfin (VP), is developed based on two-step chemical reactions. Verteporfin is bonded with carboxymethyl chitosan through EDC/NHS treatment to form VP-CMCS, and then VP-CMCS is crosslinked with oxidized sodium alginate by Schiff base reaction to form VP-CMCS-OSA hydrogel. The characterization by SEM, FTIR, and UV-Vis shows the microstructure and chemical bonding of VP-CMCS-OSA. VP-CMCS-OSA hydrogel demonstrates the properties of high tissue adhesion, strong self-healing, and tensile ability. In the full-thickness skin defect model, the VP-CMCS-OSA composite hydrogels hasten wound healing due to the synergistic effects of hydrogels and verteporfin administration. The histological examination reveals the regular collagen arrangement and more skin appendages after VP-CMCS-OSA composite hydrogel treatment, indicating the full-thickness skin regeneration without potential scar formation. The outcomes suggest that the verteporfin-loaded composite hydrogel could be a potential method for scarless skin regeneration.

A tissue-adhesive F127 hydrogel delivers antioxidative copper-selenide nanoparticles for the treatment of dry eye disease

Dry eye disease (DED) is currently the most prevalent condition seen in ophthalmology outpatient clinics, representing a significant public health issue. The onset and progression of DED are closely associated with oxidative stress-induced inflammation and damage. To address this, an aldehyde-functionalized F127 (AF127) hydrogel eye drop delivering multifunctional antioxidant Cu2-xSe nanoparticles (Cu2-xSe NPs) was designed. The research findings revealed that the Cu2-xSe nanoparticles exhibit unexpected capabilities in acting as superoxide dismutase and glutathione peroxidase. Additionally, Cu2-xSe NPs possess remarkable efficacy in scavenging reactive oxygen species (ROS) and mitigating oxidative damage. Cu2-xSe NPs displayed promising therapeutic effects in a mouse model of dry eye. Detailed investigation revealed that the nanoparticles exert antioxidant, anti-apoptotic, and inflammation-mitigating effects by modulating the NRF2 and p38 MAPK signalling pathways. The AF127 hydrogel eye drops exhibit good adherence to the ocular surface through the formation of Schiff-base bonds. These findings suggest that incorporating antioxidant Cu2-xSe nanoparticles into a tissue-adhesive hydrogel could present a highly effective therapeutic strategy for treating dry eye disease and other disorders associated with reactive oxygen species. STATEMENT OF SIGNIFICANCE: A new formulation for therapeutic eye drops to be used in the treatment of dry eye disease (DED) was developed. The formulation combines copper-selenium nanoparticles (Cu2-xSe NPs) with aldehyde-functionalized Pluronic F127 (AF127). This is the first study to directly examine the effects of Cu2-xSe NPs in ophthalmology. The NPs exhibited antioxidant capabilities and enzyme-like properties. They effectively eliminated reactive oxygen species (ROS) and inhibited apoptosis through the NRF2 and p38 MAPK signalling pathways. Additionally, the AF127 hydrogel enhanced tissue adhesion by forming Schiff-base links. In mouse model of DED, the Cu2-xSe NPs@AF127 eye drops demonstrated remarkable efficacy in alleviating symptoms of DED. These findings indicate the potential of Cu2-xSe NPs as a readily available and user-friendly medication for the management of DED.

Tissue adhesives based on chitosan for skin wound healing: Where do we stand in this era? A review

Chitosan has been commonly used as an adhesive dressing material due to its excellent biocompatibility, degradability, and renewability. Tissue adhesives are outstanding among wound dressings because they can close the wound, absorb excess tissue exudate from the wound site, provide a moist environment, and act as a carrier for loading various bioactive molecules. They have been widely used in both preclinical and clinical treatment of skin wounds. This review summarizes recent research progresses in the application of chitosan and its derivatives for tissue adhesives. We also introduce their biomedical effects on wound adhesion, contamination isolation, antibacterial, immune regulation, and wound healing, and the strategies to achieve these functions when used as wound dressings. Finally, challenges and future perspectives of chitosan-based tissue adhesives are discussed for wound healing.

Hemicellulose-based nanoaggregate-incorporated biocompatible hydrogels with enhanced mechanical properties and sustained controlled curcumin release behaviors

Local drug delivery has generated considerable interest due to its controlled and sustained drug release at the target site on demand. Nanoaggregate-incorporated composite hydrogels are desirable as local drug delivery systems; however, it is difficult to achieve sustained and controlled hydrophobic drug release and superior mechanical properties in one system. Herein, a "smart" composite hydrogel was synthesized by incorporating hemicellulose-based nanoaggregates into a double network consisting of alginate/Ca2+ and polyacrylic acid-co-dimethylaminoethyl methacrylate [P(AA-co-DMAEMA)]. Hemicellulose-based nanoaggregates were assembled from xylan-rich hemicellulose laurate methacrylate (XH-LA-MA) polymers and entrapped into the hydrogel framework via chemical fixation. Another composite hydrogel with physically embedded hemicellulose laurate (XH-LA) nanoaggregates was prepared as a comparison. Accordingly, covalently cross-linked XH-LA-MA nanoaggregates in hydrogels resulted in a denser pore structure and reinforced mechanical properties. Nanoaggregate diffusion analysis revealed that covalent bonding between the nanoaggregates and the hydrogel framework contributed to prolonged diffusion behavior. Curcumin (Cur)-loaded XH-LA-MA composite hydrogels enabled sustained Cur release in simulated body fluid and showed stimulus responsiveness toward ethylenediaminetetraacetic acid (EDTA) and/or glutathione (GSH). All the composite hydrogels were biocompatible, as verified by Cell Counting Kit-8 (CCK-8) assay against NIH/3T3 cells. These composite hydrogels hold great potential as a promising dosage form for biomedical applications.

Caffeic acid-grafted chitosan/sodium alginate/nanoclay-based multifunctional 3D-printed hybrid scaffolds for local drug release therapy after breast cancer surgery

Breast cancer is one of the most common malignant tumors in women all over the world. Mastectomy is the most effective treatment, but there are serious problems such as high tumor recurrence rate and side effects of chemotherapy. Therefore, there is an urgent need for a therapeutic strategy that can effectively promote postoperative wound healing and inhibit local tumor recurrence. In this study, a 3D printing scaffold based on carbon dots-curcumin nano-drug release (CCNPs) was developed as a local drug delivery platform (named CCNACA using CCNPs, Sodium alginate, Nanoclay and Caffeic Acid grafted Chitosan as raw materials), which has the ability to visualize drug release. The 14-day drug release test in vitro showed that the tumor inhibition rate of CCNACA scaffolds on breast cancer cells (MCF-7) was 73.77 ± 1.68 %. And the CCNACA scaffolds had good long-term antibacterial (Escherichia coli and Staphylococcus aureus) activity. Animal experiments have shown that implanting CCNACA scaffolds into surgical defects can inhibit postoperative residual cancer cells, reduce inflammation, promote angiogenesis, and repair tissue defects caused by surgery. In summary, the local drug delivery system of this manuscript has great potential in wound healing and prevention of tumor recurrence after breast cancer surgery.

Effect of injectable calcium alginate-amelogenin hydrogel on macrophage polarization and promotion of jawbone osteogenesis

Due to persistent inflammation and limited osteogenesis, jawbone defects present a considerable challenge in regenerative medicine. Amelogenin, a major protein constituent of the developing enamel matrix, demonstrates promising capabilities in inducing regeneration of periodontal supporting tissues and exerting immunomodulatory effects. These properties render it a potential therapeutic agent for enhancing jawbone osteogenesis. Nevertheless, its clinical application is hindered by the limitations of monotherapy and its rapid release characteristics, which compromise its efficacy and delivery efficiency. In this context, calcium alginate hydrogel, recognized for its superior physicochemical properties and biocompatibility, emerges as a candidate for developing a synergistic bioengineered drug delivery system. This study describes the synthesis of an injectable calcium amelogenin/calcium alginate hydrogel using calcium alginate loaded with amelogenin. We comprehensively investigated its physical properties, its role in modulating the immunological environment conducive to bone healing, and its osteogenic efficacy in areas of jawbone defects. Our experimental findings indicate that this synthesized composite hydrogel possesses desirable mechanical properties such as injectability, biocompatibility, and biodegradability. Furthermore, it facilitates jawbone formation by regulating the bone-healing microenvironment and directly inducing osteogenesis. This research provides novel insights into the development of bone-tissue regeneration materials, potentially advancing their clinical application.

Multifunctional Hydrogels for the Healing of Diabetic Wounds

The healing of diabetic wounds is hindered by various factors, including bacterial infection, macrophage dysfunction, excess proinflammatory cytokines, high levels of reactive oxygen species, and sustained hypoxia. These factors collectively impede cellular behaviors and the healing process. Consequently, this review presents intelligent hydrogels equipped with multifunctional capacities, which enable them to dynamically respond to the microenvironment and accelerate wound healing in various ways, including stimuli -responsiveness, injectable self-healing, shape -memory, and conductive and real-time monitoring properties. The relationship between the multiple functions and wound healing is also discussed. Based on the microenvironment of diabetic wounds, antibacterial, anti-inflammatory, immunomodulatory, antioxidant, and pro-angiogenic strategies are combined with multifunctional hydrogels. The application of multifunctional hydrogels in the repair of diabetic wounds is systematically discussed, aiming to provide guidelines for fabricating hydrogels for diabetic wound healing and exploring the role of intelligent hydrogels in the therapeutic processes.

A hyaluronic acid / chitosan composite functionalized hydrogel based on enzyme-catalyzed and Schiff base reaction for promoting wound healing

The healing of full-thickness skin defect has been a clinical challenge. Hydrogels with multiple functions inspired by extracellular matrix are expected to be used as wound dressing. In this paper, dopamine-grafted oxidized hyaluronic acid was blended with quaternary ammonium chitosan to form a composite functionalized hydrogel by enzyme-catalyzed cross-linking and Schiff base reaction. The hydrogel has convenient preparation, good biocompatibility, antibacterial and antioxidant, high adhesion and self-healing properties. The results in vivo show that the hydrogel can effectively close the wound and accelerate the speed of wound healing by up-regulating the expression of angiogenic protein and promoting the distribution of collagen deposition more uniform and regular. It is expected that this composite functionalized hydrogel dressing has great potential in wound regeneration.

Low-adhesion and low-swelling hydrogel based on alginate and carbonated water to prevent temporary dilation of wound sites

Hydrogel-based wound dressings have been developed for rapid wound healing; however, their adhesive properties have not been adequately investigated. Excessive adhesion to the skin causes wound expansion and pain when hydrogels absorb exudates and swell at wound sites. Herein, we developed a low-adhesion and low-swelling hydrogel dressing using alginate, which is non-adhesive to cells and skin tissue, CaCO3, and carbonated water. The alginate/CaCO3 solution rapidly formed a hydrogel upon the addition of carbonated water, and the CO2 in the hydrogel diffused into the atmosphere, preventing acidification and obtaining a pH value suitable for wound healing. Remarkably, the skin adhesion and swelling of the hydrogel were 11.9- to 16.5-fold and 1.9-fold lower, respectively, than those of clinical low-adhesion hydrogel dressings. In vivo wound-healing tests in mice demonstrated its therapeutic efficacy, and the prepared hydrogel prevented temporary wound dilation during early healing. These results illustrate the importance of controlling skin adhesion and swelling in wound dressings and demonstrate the potential clinical applications of this wound-friendly hydrogel dressing.

Self-healing hydrogels based on biological macromolecules in wound healing: A review

The complete healing of skin wounds has been a challenge in clinical treatment. Self-healing hydrogels are special hydrogels formed by distinctive physicochemically reversible bonds, and they are considered promising biomaterials in the biomedical field owing to their inherently good drug-carrying capacity as well as self-healing and repair abilities. Moreover, natural polymeric materials have received considerable attention in skin tissue engineering owing to their low cytotoxicity, low immunogenicity, and excellent biodegradation rates. In this paper, we review recent advances in the design of self-healing hydrogels based on natural polymers for skin-wound healing applications. First, we outline a variety of natural polymers that can be used to construct self-healing hydrogel systems and highlight the advantages and disadvantages of different natural polymers. We then describe the principle of self-healing hydrogels in terms of two different crosslinking mechanisms-physical and chemical-and dissect their performance characteristics based on the practical needs of skin-trauma applications. Next, we outline the biological mechanisms involved in the healing of skin wounds and describe the current application strategies for self-healing hydrogels based on these mechanisms. Finally, we analyze and summarize the challenges and prospects of natural-material-based self-healing hydrogels for skin applications.

A novel antibacterial hydrogel based on thiolated ovalbumin/gelatin with silver ions to promote wound healing in mice

Hydrogels could be used as wound dressings, but most protein-based hydrogels lack anti-bacterial effects. Here, we successfully prepared a silver ion cross-linked thiolated protein hydrogel (thiolated Ovalbumin and Gelatin, O3G7). The wound photographs showed that the healing rate (96.23 %) of hydrogel-treated mice was higher than the control group. Meanwhile, the hydrogel increased the granulation tissue's total protein content. Furthermore, it significantly increased the collagen content, consistent with the results of Masson's trichrome (MT) staining and immunohistochemical analysis of type I collagen (ColI). The results of hematoxylin and eosin (H&E) staining showed the growth and proliferation of inflammatory cells, granulation tissue, fibroblasts, blood vessels and hair follicles in acute wounds. O3G7 hydrogel had fewer inflammatory cells and more neovascularization, and hair follicle tissue and intact epidermis could be observed. The results of immunofluorescence and immunohistochemistry showed that the O3G7 group reduced the expression of tumor necrosis factor (TNF)-α (56.87 % of the control group) and upregulated the expression of transforming growth factor (TGF)-β (1.29 times of the control group). These results suggest that O3G7 hydrogel significantly affects the healing of acute wounds. This study demonstrates that hydrogels prepared from food-derived proteins will be promising and bio-safe candidates in bioengineering.

Recent advances in double network hydrogels based on naturally-derived polymers: synthesis, properties, and biological applications

Hydrogels composed of naturally-derived biopolymers have garnered significant research interest due to the bioavailability and biocompatibility of starting materials. However, translating these advantages to practical use is challenged by limitations of mechanical properties and stability of the resulting materials. The development of double network (DN) hydrogels has led to greatly enhanced mechanical properties and shows promise toward broadening the applications of conventional synthetic or natural hydrogels. This review highlights recently developed protein-based and polysaccharide-based DN hydrogels. For each biopolymer, we focus on a subset of DN hydrogels centered around a theme related to synthetic design or applications. Network structures and crosslinking mechanisms that endow enhanced mechanical properties and performance to the materials are discussed. Important applications, including tissue engineering, drug delivery, bioadhesives, wound healing, and wearable sensors, that arise from the inherent properties of the natural polymer or its combination with other materials are also emphasized. Finally, we discuss ongoing challenges to stimulate the discovery of new design principles for the future of DN hydrogels based on naturally-derived polymers for biological applications.

Antibacterial, antioxidant and injectable hydrogels constructed using CuS and curcumin co-loaded micelles for NIR-enhanced infected wound healing

Constructing antibacterial and antioxidant hydrogels is critical for treating infected full-thickness skin wounds. Herein, we report a co-encapsulation strategy to load CuS nanoparticles and hydrophobic antioxidant curcumin (cur) in aldehyde-terminated F127 micelles, which are then cross-linked with carboxymethyl chitosan through a Schiff base reaction to form a functional composite hydrogel (CF-CuS-cur). Apart from its suitable swelling and degradation behavior, good biocompatibility, and injectability for treating irregular wounds, the CF-CuS-cur hydrogel displayed excellent photothermal antibacterial ability under 1064 nm NIR laser irradiation, and antioxidant activity to protect cells from excessive oxidative stress. Using a full-thickness infected wound model, we demonstrated that the CF-CuS-cur hydrogel accelerated the wound healing process by effective sterilization and decreased inflammation, under synergistic action from CuS, curcumin and NIR irradiation. Histological and immunohistochemistry analysis further revealed the promoted skin attachments and regeneration, collagen deposition, neovascularization, and early transition to anti-inflammatory M2 macrophages, when the wounds were treated with the CF-CuS-cur hydrogel. This work demonstrates a facile strategy to construct functional hydrogels with NIR-enhanced antibacterial and antioxidant properties, which can be potentially applied as wound dressings for treating chronic wounds.

Adhesive injectable cellulose-based hydrogels with rapid self-healing and sustained drug release capability for promoting wound healing

Injectable biocompatible hydrogels with multiple functions, including self-healing, adhesion, antibacterial activity, and suitable mechanical properties, are highly desirable for enhancing wound healing. In this study, a new class of multi-functional injectable self-healing cellulose-based hydrogels was synthesised using dynamic covalent acylhydrazone linkages for wound dressing. The carboxymethyl cellulose-graft-adipic dihydrazide (CMC-ADH)/4-Formylbenzoic acid-terminated poly(ethylene glycol) (PEG-FBA) (CMC-ADH/PEG-FBA) hydrogels have adjustable gelation time and excellent self-healing ability. In addition, drug release and in vitro antibacterial activities against Gram-positive and Gram-negative bacteria confirmed the sustained drug-release capacity of the hydrogels. Moreover, haemostasis and wound-healing effects were investigated using an in vivo haemorrhaging liver mouse model and a full-thickness skin defect model, and the results indicated that they not only promoted the wound-healing process but also presented excellent haemostatic effects. The CMC-ADH/PEG-FBA gels also exhibited good adhesion to irregular wounds and significantly enhanced angiogenic ability in vivo. This excellent wound-healing performance occurs because hydrogels can quickly stop bleeding, provide a moist and closed environment for the wound to prevent bacterial invasion, release ciprofloxacin (CIP), reduce inflammatory reactions, and promote wound tissue regeneration. In summary, the synthesised multi-functional gels are ideal candidates for treating haemorrhages and irregular wounds.

Cu(II)@MXene based photothermal hydrogel with antioxidative and antibacterial properties for the infected wounds

The regeneration of skin tissue is often impeded by bacterial infection seriously. At the same time, reactive oxygen species (ROS) are often overexpressed in infected skin wounds, causing persistent inflammation that further hinders the skin repair process. All of these make the treatment of infected wounds is still a great challenge in clinic. In this study, we fabricate Cu(II)@MXene photothermal complex based on electrostatic self-assembly between Cu2+ and MXene, which are then introduced into a hyaluronic acid (HA) hydrogel to form an antibacterial dressing. The rapid adhesion, self-healing, and injectability of the dressing allows the hydrogel to be easily applied to different wound shapes and to provide long-term wound protection. More importantly, this easily prepared Cu(II)@MXene complex can act as a photothermal antibacterial barrier, ROS scavenger and angiogenesis promoter simultaneously to accelerate the healing rate of infected wounds. Our in vivo experiments strongly proved that the inflammatory condition, collagen deposition, vessel formation, and the final wound closure area were all improved by the application of Cu(II)@MXene photothermal hydrogel dressing.

Platelet Rich Plasma Loaded Multifunctional Hydrogel Accelerates Diabetic Wound Healing via Regulating the Continuously Abnormal Microenvironments

Continuous oxidative stress and cellular dysfunction caused by hyperglycemia are distinguishing features of diabetic wounds. It has been a great challenge to develop a smart dressing that can accelerate diabetic wound healing through regulating abnormal microenvironments. In this study, a platelet rich plasma (PRP) loaded multifunctional hydrogel with reactive oxygen species (ROS) and glucose dual-responsive property is reported. It can be conveniently prepared with PRP, dopamine (DA) grafted alginate (Alg-DA), and 6-aminobenzo[c][1,2]oxaborol-1(3H)-ol (ABO) conjugated hyaluronic acid (HA-ABO) through ionic crosslinks, hydrogen-bond interactions, and boronate ester bonds. The hydrogel possesses injectability, moldability, tissue adhesion, self-healing, low hemolysis, and hemostasis performances. Its excellent antioxidant property can create a low oxidative stress microenvironment for other biological events. Under an oxidative stress and/or hyperglycemia state, the hydrogel can degrade at an accelerated rate to release a variety of cytokines derived from activated blood platelets. The result is a series of positive changes that are favorable for diabetic wound healing, including fast anti-inflammation, activated macrophage polarization toward M2 phenotype, promoted migration and proliferation of fibroblasts, as well as expedited angiogenesis. This work provides an efficient strategy for chronic diabetic wound management and offers an alternative for developing a new-type PRP-based bioactive wound dressing.

Physical dynamic double-network hydrogels as dressings to facilitate tissue repair

Double-network hydrogels can be tuned to have high mechanical strength, stability, elasticity and bioresponsive properties, which can be combined to create self-healing, adhesive and antibacterial wound dressings. Compared with single-network hydrogel, double-network hydrogel shows stronger mechanical properties and better stability. In comparison with chemical bonds, the cross-linking in double networks makes them more flexible than single-network hydrogels and capable of self-healing following mechanical damage. Here, we present the stepwise synthesis of physical double-network hydrogels where hydrogen bonds and coordination reactions provide self-healing, pH-responsive, tissue-adhesive, antioxidant, photothermal and antibacterial properties, and can be removed on demand. We then explain how to carry out physical, chemical and biological characterizations of the hydrogels for use as wound dressings, yet the double-network hydrogels could also be used in different applications such as tissue engineering scaffolds, cell/drug delivery systems, hemostatic agents or in flexible wearable devices for monitoring physiological and pathological parameters. We also outline how to use the double-network hydrogels in vivo as wound dressings or hemostatic agents. The synthesis of the ureido-pyrimidinone-modified gelatin, catechol-modified polymers and the hydrogels requires 84 h, 48 h and 1 h, respectively, whereas the in vivo assays require 3.5 weeks. The procedure is suitable for users with expertise in biomedical polymer materials.

Hydrogel Tissue Bioengineered Scaffolds in Bone Repair: A Review

Large bone defects due to trauma, infections, and tumors are difficult to heal spontaneously by the body's repair mechanisms and have become a major hindrance to people's daily lives and economic development. However, autologous and allogeneic bone grafts, with their lack of donors, more invasive surgery, immune rejection, and potential viral transmission, hinder the development of bone repair. Hydrogel tissue bioengineered scaffolds have gained widespread attention in the field of bone repair due to their good biocompatibility and three-dimensional network structure that facilitates cell adhesion and proliferation. In addition, loading natural products with nanoparticles and incorporating them into hydrogel tissue bioengineered scaffolds is one of the most effective strategies to promote bone repair due to the good bioactivity and limitations of natural products. Therefore, this paper presents a brief review of the application of hydrogels with different gel-forming properties, hydrogels with different matrices, and nanoparticle-loaded natural products loaded and incorporated into hydrogels for bone defect repair in recent years.

Double network hydrogels: Design, fabrication, and application in biomedicines and foods

Research on the design, fabrication, and application of double network (DN) hydrogels, assembled from pairs of polymers, has grown recently due to their unique structural, physicochemical, and functional properties. DN hydrogels can be designed to exhibit a broader range of functional attributes than single network (SN) ones, which extends their applications in various fields. There has been strong interest in the development of biopolymer DN hydrogels because of their environmental, sustainability, and safety benefits. However, there is limited knowledge on the formation and application of these novel materials. This article reviews the principles underlying the design and fabrication of hydrogels using different crosslinking approaches, including covalent and/or non-covalent bonding, and the formation mechanisms, network structures, and functional attributes of different DN hydrogels. The impact of polymer composition, structural organization, and bonding on the mechanical and functional properties of DN hydrogels is reviewed. Potential applications of these hydrogels are highlighted, including in tissue engineering, biomedicines, and foods. The functional attributes of DN hydrogels can be tailored to each of these applications by careful selection of the biopolymers and crosslinking mechanisms used to assemble them. Finally, areas where further research are needed to overcome the current limitations of DN hydrogels are highlighted.

Design and fabrication of gelatin-based hydrogel loaded with modified amniotic extracellular matrix for enhanced wound healing

Trauma can damage the structural integrity of skin leading to its function being affected. There is an urgent clinical need for innovative therapeutic wound dressings. However, several challenges persist despite the current demands. The development and application of functional dressings offer a novel approach to address skin and subcutaneous soft tissue defects. Amniotic membrane as an ideal biological multifunctional material covering wound surface has been reported in clinic. However, current clinical applications of amniotic membrane still have limitations, such as thinness and mechanically weak. In this paper, we employed decellularized human amniotic membrane (dHAM) as a bioactive extracellular matrix (ECM) and modified it through methacrylate (MA) grafting for engineering purposes, resulting in the photosensitive dECMMA. Subsequently, we utilized a photosensitizer to achieve photopolymerization of dECMMA with GelMA hydrogel, successfully creating a novel composite hydrogel termed dECMMA/GelMA. This composite hydrogel not only inherits the favorable physicochemical properties of hydrogels but also maintains comparable levels of bioactivity to dHAM itself, supporting cell proliferation, migration, angiogenesis, and retaining significant anti-inflammatory capacity. Additionally, we evaluated the reparative effect of the designed dECMMA/GelMA composite hydrogel on rabbit wound defects. We demonstrated that the dECMMA/GelMA promoted wound healing and re-epithelization. These findings highlight the substantial benefits and therapeutic potential of the dECMMA/GelMA composite hydrogel as a practical solution for clinical applications in the treatment of soft tissue damage. Furthermore, this research provides a new strategy for designing and manufacturing bioactive dressings with exceptional clinical efficacy in the future.

Injectable multifunctional carboxymethyl chitosan/hyaluronic acid hydrogel for drug delivery systems

Injectable hydrogels with notable mechanical properties and self-healing ability are promising carriers for use as a drug delivery system. Here, adipic acid dihydrazide (ADH) and calcium ions (Ca2+) were introduced into quaternary ammonium carboxymethyl chitosan and aldehyde-modified hyaluronic acid hydrogels (QCS + OHA). The hydrogels were synthesized through the interaction of the Schiff bases (imine bonds, acylhydrazone bonds) and coordination bonds via a facile one-step approach. The gelation time (∼54 s) ensured excellent injectability. The QCS + OHA + ADH + Ca2+ hydrogel had notable mechanical properties (compressive stress up to 896.30 KPa), good self-healing ability (up to 94 %), good pH responsiveness, and excellent antibacterial properties. In addition, the QCS + OHA + ADH + Ca2+ hydrogel had a high drug loading capacity (121.3 mg/g) and sustained drug release behaviour (≥120 h). The results of cytotoxicity tests showed a high cell proliferation rate (up to 98 %) and good cytocompatibility. In summary, this work presents an injectable and self-healing pH-responsive hydrogel that can be used as a carrier for drug delivery systems.

Injectable, self-healing hydrogel adhesives with firm tissue adhesion and on-demand biodegradation for sutureless wound closure

Tissue adhesives have garnered extensive interest as alternatives and supplements to sutures, whereas major challenges still remain, including weak tissue adhesion, inadequate biocompatibility, and uncontrolled biodegradation. Here, injectable and biocompatible hydrogel adhesives are developed via catalyst-free o-phthalaldehyde/amine (hydrazide) cross-linking reaction. The hydrogels demonstrate rapid and firm adhesion to various tissues, and an o-phthalaldehyde-mediated tissue adhesion mechanism is established. The hydrogel adhesives show controlled degradation profiles of 6 to 22 weeks in vivo through the incorporation of disulfide bonds into hydrogel network. In liver and blood vessel injury, the hydrogels effectively seal the incisions and rapidly stop bleeding. In rat and rabbit models of full-thickness skin incision, the hydrogel adhesives quickly close the incisions and accelerate wound healing, which exhibit efficacies superior to those of commercially available fibrin glue and cyanoacrylate glue. Thus, the hydrogel adhesives show great potential for sutureless wound closure, hemostasis sealing, and prevention of leakage in surgical applications.

Mussel-inspired self-healing hydrogel form pectin and cellulose for hemostasis and diabetic wound repairing

Diabetic wound is considered as a kind of chronic wound prone to infection and difficult to repair due to high glucose level in the blood of patients. In this research, a biodegradable self-healing hydrogel with mussel inspired bioadhesion and anti-oxidation properties is fabricated based on Schiff-base cross-linking. The hydrogel was designed from dopamine coupled pectin hydrazide (Pec-DH) and oxidized carboxymethyl cellulose (DCMC) for mEGF loading as a diabetic wound repair dressing. The Pectin and CMC as natural feedstock endowed the hydrogel with biodegradability to avoid possible side effects, while the coupled catechol structure could enhance the tissue adhesion of the hydrogel for hemostasis. The results showed the Pec-DH/DCMC hydrogel formed fast and can cover irregular wounds with good sealing effect. The catechol structure also improved the reactive oxygen species (ROS) scavenging ability of the hydrogel, which can eliminate the negative effect of ROS during wound healing. The in vivo diabetic wound healing experiment revealed the hydrogel as mEGF loading vehicle greatly enhanced the diabetic wound repairing rate in mice model. As a result, the Pec-DH/DCMC hydrogel could show advantages as EGF carrier in wound healing applications.

Progress in Pluronic F127 Derivatives for Application in Wound Healing and Repair

Pluronic F127 hydrogel biomaterial has garnered considerable attention in wound healing and repair due to its remarkable properties including temperature sensitivity, injectability, biodegradability, and maintain a moist wound environment. This comprehensive review provides an in-depth exploration of the recent advancements in Pluronic F127-derived hydrogels, such as F127-CHO, F127-NH2, and F127-DA, focusing on their applications in the treatment of various types of wounds, ranging from burns and acute wounds to infected wounds, diabetic wounds, cutaneous tumor wounds, and uterine scars. Furthermore, the review meticulously examines the intricate interaction mechanisms employed by these hydrogels within the wound microenvironment. By elucidating the underlying mechanisms, discussing the strengths and weaknesses of Pluronic F127, analyzing the current state of wound healing development, and expanding on the trend of targeting mitochondria and cells with F127 as a nanomaterial. The review enhances our understanding of the therapeutic effects of these hydrogels aims to foster the development of effective and safe wound-healing modalities. The valuable insights provided this review have the potential to inspire novel ideas for clinical treatment and facilitate the advancement of innovative wound management approaches.

Ultrasound-triggered piezocatalytic composite hydrogels for promoting bacterial-infected wound healing

Wound healing has become one of the basic issues faced by the medical community because of the susceptibility of skin wounds to bacterial infection. As such, it is highly desired to design a nanocomposite hydrogel with excellent antibacterial activity to achieve high wound closure effectiveness. Here, based on ultrasound-triggered piezocatalytic therapy, a multifunctional hydrogel is designed to promote bacteria-infected wound healing. Under ultrasonic vibration, the surface of barium titanate (BaTiO3, BT) nanoparticles embedded in the hydrogel rapidly generate reactive oxygen species (ROS) owing to the established strong built-in electric field, endowing the hydrogel with superior antibacterial efficacy. This modality shows intriguing advantages over conventional photodynamic therapy, such as prominent soft tissue penetration ability and the avoidance of serious skin phototoxicity after systemic administration of photosensitizers. Moreover, the hydrogel based on N-[tris(hydroxymethyl)methyl]acrylamide (THM), N-(3-aminopropyl)methacrylamide hydrochloride (APMH) and oxidized hyaluronic acid (OHA) exhibits outstanding self-healing and bioadhesive properties able to accelerate full-thickness skin wound healing. Notably, compared with the widely reported mussel-inspired adhesive hydrogels, OHA/THM-APMH hydrogel due to the multiple hydrogen bonds from unique tri-hydroxyl structure overcomes the shortage that catechol groups are easily oxidized, giving it long-term and repeatable adhesion performance. Importantly, this hybrid hydrogel confines BT nanoparticles to wound area and locally induced piezoelectric catalysis under ultrasound to eradicate bacteria, markedly improving the therapeutic biosafety and exhibits great potential for harmless treatment of bacteria-infected tissues.

Colorimetric pH-responsive and hemostatic hydrogel-based bioadhesives containing functionalized silver nanoparticles

Here we develop and characterize a dual-cross-linked pH-responsive hydrogel based on the carboxyethyl chitosan-oxidized sodium alginate (CAO) containing silver nanoparticles (Ag NPs) functionalized with tannic acid/red cabbage (ATR). This hybrid hydrogel is formed via covalent and non-covalent cross-linking. The adhesive strength measured in contact with cow skin and compression strength is measured more than 3 times higher than that of CAO. Importantly, the incorporation of 1 ​wt% ATR into CAO significantly enhances the compression strength of CAO from 35.1 ​± ​2.1 ​kPa to 97.5 ​± ​2.9 ​kPa. Moreover, the cyclic compression tests confirm significantly higher elastic behavior of CAO after the addition of ATR-functionalized NPs to CAO. The CAO/ATR hydrogel is pH-sensitive and indicated remarkable color changes in different buffer solutions. The CAO/ATR also shows improved hemostatic properties and reduced clotting time compared to the clotting time of blood in contact with CAO hydrogel. In addition, while CAO/ATR is effective in inhibiting the growth of both Gram-positive and Gram-negative bacteria, CAO is only effective in inhibiting the growth of Gram-positive bacteria. Finally, the CAO/ATR hydrogel is cytocompatible with L929 fibroblasts. In summary, the resulting CAO/ATR hydrogel shows promising results in designing and constructing smart wound bioadhesives with high cytocompatibility, antibacterial properties, blood coagulation ability, and fast self-healing properties.

Bioinspired Polyacrylic Acid-Based Dressing: Wet Adhesive, Self-Healing, and Multi-Biofunctional Coacervate Hydrogel Accelerates Wound Healing

Polyacrylic acid (PAA) and its derivatives are commonly used as essential matrices in wound dressings, but their weak wet adhesion restricts the clinical application. To address this issue, a PAA-based coacervate hydrogel with strong wet adhesion capability is fabricated through a facile mixture of PAA copolymers with isoprenyl oxy poly(ethylene glycol) ether and tannic acid (TA). The poly(ethylene glycol) segments on PAA prevent the electrostatic repulsion among the ionized carboxyl groups and absorbed TA to form coacervates. The absorbed TA provides solid adhesion to dry and wet substrates via multifarious interactions, which endows the coacervate with an adhesive strength to skin of 23.4 kPa and 70% adhesion underwater. This coacervate achieves desirable self-healing and extensible properties suitable for frequently moving joints. These investigations prove that the coacervate has strong antibacterial activity, facilitates fibroblast migration, and modulates M1/M2 polarization of macrophages. In vivo hemorrhage experiments further confirm that the coacervate dramatically shortens the hemostatic time from hundreds to tens of seconds. In addition, full-thickness skin defect experiments demonstrate that the coacervate achieves the best therapeutic effect by significantly promoting collagen deposition, angiogenesis, and epithelialization. These results demonstrate that a PAA-based coacervate hydrogel is a promising wound dressing for medical translation.

Recent advances of Pluronic-based copolymers functionalization in biomedical applications

The design of polymeric biocompatible nanomaterials for biological and medical applications has received special attention in recent years. Among different polymers, the triblock type copolymers (EO)_x(PO)_y(EO)_x or Pluronics® stand out due its favorable characteristics such as biocompatibility, low tissue adhesion, thermosensitivity, and structural capacity to produce different types of macro and nanostructures, e.g. micelles, vesicles, nanocapsules, nanospheres, and hydrogels. However, Pluronic itself is not the "magic bullet" and its functionalization via chemical synthesis following biologically oriented design rules is usually required aiming to improve its properties. Therefore, this paper presents some of the main publications on new methodologies for synthetic modifications and applications of Pluronic-based nanoconstructs in the biomedical field in the last 15 years. In general, the polymer modifications aim to improve physical-chemical properties related to the micellization process or physical entrapment of drug cargo, responsive stimuli, active targeting, thermosensitivity, gelling ability, and hydrogel formation. Among these applications, it can be highlighted the treatment of malignant neoplasms, infectious diseases, wound healing, cellular regeneration, and tissue engineering. Functionalized Pluronic has also been used for various purposes, including medical diagnosis, medical imaging, and even miniaturization, such as the creation of lab-on-a-chip devices. In this context, this review discusses the main scientific contributions to the designing, optimization, and improvement of covalently functionalized Pluronics aiming at new strategies focused on the multiple areas of the biomedical field.

Rapidly degrading and mussel-inspired multifunctional carboxymethyl chitosan/montmorillonite hydrogel for wound hemostasis

The conventional method of using montmorillonite hemostatic materials affects the hemostatic effect due to easy dislodgement on the wound surface. In this paper, a multifunctional bio-hemostatic hydrogel (CODM) was prepared based on hydrogen bonding and Schiff base bonding using modified alginate, polyvinylpyrrolidone (PVP), and carboxymethyl chitosan. The amino group-modified montmorillonite was uniformly dispersed in the hydrogel by its amido bond formation with the carboxyl groups of carboxymethyl chitosan and oxidized alginate. The catechol group, -CHO, and PVP can form hydrogen bonds with the tissue surface to afford the firm tissue adhesion to afford the wound hemostatic. The addition of montmorillonite-NH₂ further improves the hemostatic ability, making it even better than commercial hemostatic materials. Moreover, the photothermal conversion ability (derived from the polydopamine) was synergized with the phenolic hydroxyl group, quinone group, and the protonated amino group to effectively kill the bacteria in vitro and in vivo. Based on its in vitro and in vivo biosafety and satisfactory degradation ratio anti-inflammatory, antibacterial, and hemostatic properties, the CODM hydrogel holds promising potential for emergency hemostasis and intelligent wound management.

Functionalization of hyaluronic acid for development of self-healing hydrogels for biomedical applications: A review

Materials that are capable of undergoing self-repair following any physical damage or rupture due to external stimuli are identified as self-healing materials. Such materials are engineered by crosslinking the polymer backbone chains typically through reversible linkages. These reversible linkages include imines, metal-ligand coordination, polyelectrolyte interaction, disulfide, etc. These bonds are reversibly responsive to changes in various stimuli. Newer self-healing materials are now being developed in the field of biomedicine. Chitosan, cellulose, starch etc. are a few examples of polysaccharides that are generally used to synthesize such materials. Hyaluronic acid has been a very recent addition to the list of polysaccharides that are being investigated for construction of self-healing materials. It is non-toxic, non-immunogenic, has good gelation property and good injectability. Hyaluronic acid based self-healing materials are particularly employed for targeted drug delivery, protein and cell delivery, electronics, biosensors and many such biomedical applications. This review critically focuses on the functionalization of hyaluronic acid to fabricate self-healing hydrogels for biomedical applications. It also explores and sums up the mechanical data as well as self-healing efficiency of the hydrogels across wide range of interactions as discussed in the review below.

Injectable, In Situ Self-cross-linking, Self-healing Poly(l-glutamic acid)/Polyethylene Glycol Hydrogels for Cartilage Tissue Engineering

Injectable hydrogels have drawn much attention in the field of tissue engineering because of advantages such as simple operation, strong plasticity, and good biocompatibility and biodegradability. Herein, we propose the novel design of injectable hydrogels via a Schiff base cross-linking reaction between adipic dihydrazide (ADH)-modified poly(l-glutamic acid) (PLGA-ADH) and benzaldehyde-terminated poly(ethylene glycol) (PEG-CHO). The effects of the mass fraction and the molar ratio of -CHO/-NH₂ on the gelation time, mechanical properties, equilibrium swelling, and in vitro degradation of the hydrogels were examined. The PLGA/PEG hydrogels cross-linked by dynamic Schiff base linkages exhibited good self-healing ability. Additionally, the PLGA/PEG hydrogels had good biocompatibility with bone marrow-derived mesenchymal stem cells (BMSCs) and could effectively support BMSC proliferation and deposition of glycosaminoglycans and upregulate the expression of cartilage-specific genes. In a rat cartilage defect model, PLGA/PEG hydrogels significantly promoted new cartilage formation. The results suggest the prospect of the PLGA/PEG hydrogels in cartilage tissue engineering.

Salvianolic-Acid-B-Loaded HA Self-Healing Hydrogel Promotes Diabetic Wound Healing through Promotion of Anti-Inflammation and Angiogenesis

Inflammatory dysfunction and angiogenesis inhibition are two main factors leading to the delayed healing of diabetic wounds. Hydrogels with anti-inflammatory and angiogenesis-promoting effects have been considered as promising wound care materials. Herein, a salvianolic acid B (SAB)-loaded hyaluronic acid (HA) self-healing hydrogel (HA/SAB) with anti-inflammatory and pro-angiogenesis capacities for diabetic wound healing is reported. The HA hydrogel was prepared via the covalent cross-linking of aldehyde groups in oxidized HA (OHA) and hydrazide groups in adipic dihydrazide (ADH)-modified HA (HA-ADH) with the formation of reversible acylhydrazone bonds. The obtained HA hydrogel exhibited multiple favorable properties such as porous structures, excellent self-healing properties, a sustainable release capacity of SAB, as well as excellent cytocompatibility. In addition, the effects of the SAB-loaded HA self-healing hydrogel were investigated via a full-thickness skin defect model using diabetic rats. The HA/SAB hydrogel showed enhanced skin regeneration effects with accelerated wound closure, shorter remaining dermal space length, thicker granulation tissue formation, and more collagen deposition. Furthermore, reduced inflammatory response and enhanced vascularization were found with HA/SAB2.5 hydrogel-treated wounds, indicating that the hydrogel promotes diabetic wound healing through the promotion of anti-inflammation and angiogenesis. Our results suggest that the fabricated SAB-loaded HA self-healing hydrogel is promising as a wound dressing for the treatment of diabetic wounds.