ε-Polylysine-Based Macromolecules with Catalase-Like Activity to Accelerate Wound Healing by Clearing Bacteria and Attenuating Inflammatory Response

A Poly-γ-Glutamic Acid/ε-Polylysine Hydrogel: Synthesis, Characterization, and Its Role in Accelerated Wound Healing

Wound healing is a complex biological process involving inflammation, proliferation, and remodeling phases. Effective healing is essential for maintaining skin integrity, driving the need for advanced materials like hydrogels, known for their high water retention and tunable mechanical properties. In this study, we synthesized a biocompatible composite hydrogel composed of γ-polyglutamic acid (γ-PGA) and ε-polylysine (ε-PL) through a Schiff base reaction, forming a stable crosslinked network. Its physicochemical properties, including rheological behavior and swelling capacity, were systematically evaluated. Biocompatibility was assessed via in vitro hemolysis and cytotoxicity assays, and in vivo testing was performed using a full-thickness skin defect model in Sprague Dawley (SD) rats to evaluate wound-healing efficacy. The PGA-PL hydrogel demonstrated excellent physicochemical properties, with a maximum swelling ratio of 65.6%, and biocompatibility as evidenced by low hemolysis rates (<5%) and high cell viability (>80%). It promoted wound healing by inhibiting the inflammatory response, reducing levels of the inflammatory cytokine IL-6, enhancing angiogenesis, and accelerating collagen deposition. The hydrogel showed complete biodegradation within 21 days in vivo without inducing a significant inflammatory response and significantly accelerated wound healing, achieving an 86% healing rate within 7 days compared to 67% in the control group. The PGA-PL composite hydrogel exhibits excellent mechanical strength and biocompatibility, and its effective wound-healing capabilities lay the groundwork for future development and optimization in various tissue engineering applications.

Biodegradable Oxygen-Generating Microneedle Patches for Regenerative Medicine Applications

Upon injury, regenerating skin is metabolically active and requires oxygen for physiological processes related to wound healing. Such processes can be halted in hypoxic conditions common in chronic wounds. Microneedle arrays (MNAs) have been demonstrated to improve therapeutic delivery and wound healing. Recently, few studies have explored the use of oxygen-releasing MNAs; however, they involve complex manufacturing and handling and fail to eliminate cytotoxic byproducts. To address these challenges, biodegradable and mechanically robust gelatin methacryloyl-based MNAs are developed that can penetrate the tissue and release oxygen upon exposure to interstitial fluid and wound exudates. The oxygen release rate and biocompatibility of the developed MNAs with different compositions are evaluated and optimized. Interestingly, in vitro studies demonstrate that the optimized compositions can release oxygen at therapeutic levels and significantly increase viability of chronically hypoxic cells to match that of normoxic cells. In vivo studies further confirm that the optimized oxygen-generating MNAs do not cause any harm or impair healing in a murine model of acute skin injury. Additionally, transcriptomic analysis reveals upregulation of key pathways related to fibroblast motility, lipid metabolism, and a marked reduction in inflammatory signaling, all of which contribute to improved wound healing. The developed strategy can introduce new opportunities in elimination of hypoxia and therefore treatment of chronic wounds.

Composite Hydrogels with Rapid Self-Healing, Stretchable, Moldable and Antibacterial Properties Based on PVA/ε-Poly-l-lysine/Hyaluronic Acid

Self-healing, stretchable, and moldable hydrogels have a great potential application in tissue engineering and soft robotics. Despite great success in reported hydrogels, it is still a great challenge to construct the moldable hydrogels with an ultrafast self-healing performance. Herein, the composite hydrogels (PBLH) with ultrafast self-healing, stretchable, and moldable properties were successfully constructed by poly (vinyl alcohol) (PVA), borate (B), ε-poly-l-lysine (EPL), and hyaluronic acid (HA) based on an efficient one-pot method. Fourier transform infrared spectroscopy, X-ray diffraction, and rheological measurements confirmed the formation of a dynamic network among PVA, B, EPL, and HA through the cross-linking of dynamic borate bonds, electrostatic interaction, and hydrogen bonding. Having fabricated the dynamic network structure, the damage gap of the composite hydrogels can heal within 1 min, presenting an excellent self-healing ability. Simultaneously, the composite hydrogels can be molded into various shapes, and the length of the composite hydrogels can be stretched to 15 times their original length. In addition, the composite hydrogels exhibited an excellent antibacterial property against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Our results illustrated that the composite hydrogels not only retain the advantages of traditional hydrogels but also possess ultrafast self-healing, outstanding stretchable and antibacterial properties, presenting a prospective candidate for constructing biomedical materials.

Gases and gas-releasing materials for the treatment of chronic diabetic wounds

Chronic non-healing wounds are a common consequence of skin ulceration in diabetic patients, with severe cases such as diabetic foot even leading to amputations. The interplay between pathological factors like hypoxia-ischemia, chronic inflammation, bacterial infection, impaired angiogenesis, and accumulation of advanced glycosylation end products (AGEs), resulting from the dysregulation of the immune microenvironment caused by hyperglycemia, establishes an unending cycle that hampers wound healing. However, there remains a dearth of sufficient and effective approaches to break this vicious cycle within the complex immune microenvironment. Consequently, numerous scholars have directed their research efforts towards addressing chronic diabetic wound repair. In recent years, gases including Oxygen (O2), Nitric oxide (NO), Hydrogen (H2), Hydrogen sulfide (H2S), Ozone (O3), Carbon monoxide (CO) and Nitrous oxide (N2O), along with gas-releasing materials associated with them have emerged as promising therapeutic solutions due to their ability to regulate angiogenesis, intracellular oxygenation levels, exhibit antibacterial and anti-inflammatory effects while effectively minimizing drug residue-induced damage and circumventing drug resistance issues. In this review, we discuss the latest advances in the mechanisms of action and treatment of these gases and related gas-releasing materials in diabetic wound repair. We hope that this review can provide different ideas for the future design and application of gas therapy for chronic diabetic wounds.

Glucose Oxidase Energized Osmium with Dual-Active Centers and Triple Enzyme Activities for Infected Diabetic Wound Management

Diabetic wounds are susceptible to bacterial infections, largely linked to high blood glucose levels (hyperglycemia). To treat such wounds, enzymes like glucose oxidase (GOx) can be combined with nanozymes (nanomaterials mimic enzymes) to use glucose effectively for purposes. However, there is still room for improvement in these systems, particularly in terms of process simplification, enzyme activity regulation, and treatment effects. Herein, the approach utilizes GOx to directly facilitate the biomineralized growth of osmium (Os) nanozyme (GOx-OsNCs), leading to dual-active centers and remarkable triple enzyme activities. Initially, GOx-OsNCs use vicinal dual-active centers, enabling a self-cascaded mechanism that significantly enhances glucose sensing performance compared to step-by-step reactions, surpassing the capabilities of other metal sources such as gold and platinum. In addition, GOx-OsNCs are integrated into a glucose-sensing gel, enabling instantaneous visual feedback. In the treatment of infected diabetic wounds, GOx-OsNCs exhibit multifaceted benefits by lowering blood glucose levels and exhibiting antibacterial properties through the generation of hydroxyl free radicals, thereby expediting healing by fostering a favorable microenvironment. Furthermore, the catalase-like activity of GOx-OsNCs aids in reducing oxidative stress, inflammation, and hypoxia, culminating in improved healing outcomes. Overall, this synergistic enzyme-nanozyme blend is user-friendly and holds considerable promise for diverse applications.

Antibacterial, ROS scavenging and angiogenesis promotingϵ-Polylysine/gelatin based hydrogel containing CTLP to regulate macrophages for pressure ulcer healing

Pressure ulcers (PUs) have emerged as a substantial burden on individuals and society. The introduction of innovative dressings that facilitate the healing of pressure ulcer wounds represents a cost-effective alternative for treatment. In this study, the emphasis is on the preparation of Carthamus tinctorius L. polysaccharide (CTLP) as hydrogel microspheres (MPs), which are then encapsulated within a hydrogel matrix crosslinked with phenylboronic acid gelatin (Gelatin-PBA) andϵ-polylysine-grafted catechol (ϵ-PL-Cat) to enable sustained release for promoting pressure ulcer healing. The presented Gelatin-PBA/ϵ-PL-Cat (GPL)/CTLP-MPs hydrogel demonstrated outstanding self-healing properties. In addition,in vitroexperiments revealed that the hydrogel exhibited remarkable antibacterial activity, excellent biocompatibility. And it showed the capacity to promote vascular formation, effectively scavenge reactive oxygen species, and facilitate macrophage polarization from the M1 to M2 phenotype.In vivowound healing of mice PUs indicated that the prepared GPL/CTLP-MPs hydrogel effectively accelerated the formation of granulation tissue and facilitated the healing of the wounds. In summary,in vivoandin vitroexperiments consistently highlight the therapeutic potential of GPL/CTLP-MPs hydrogel in facilitating the healing process of PUs.