By Endowing Polyglutamic Acid/Polylysine Composite Hydrogel with Super Intrinsic Characteristics to Enhance its Wound Repair Potential

Injectable antibacterial hydrogels based on oligolysines for wound healing

Generally, oligolysine has poor antibacterial effect and almost no antibacterial activity. Herein, low cost and easily available oligolysines were chosen to prepare injectable antibacterial hydrogel (PVAL-gel) for wound healing. The hydrogel network was formed by cross-linking vanillin acrylate-N, N-dimethylacrylamide copolymer P(VA-co-DMA), oligolysine and adipate dihydrazide through Schiff base bond. The obtained hydrogel PVAL-gel exhibited not only excellent self-healing capability and injectability, but also the efficient contact antibacterial ability and good inhibitory effects on E.coli and S.aureus. In vitro, 99.9 % of pathogenic bacteria was killed within 160 min. Furthermore, the injectable PVAL-gel could rapidly eradicate bacteria in infected wounds and notably enhance the healing of full-thickness skin wounds. Therefore, PVAL-gel is expected to be used as a high-end dressing for the treatment of infected skin wounds, which can promote wound healing.

A novel hydrogel with inherent antibacterial and hemostatic properties for burn wound healing

The skin is the immune system's first line of defense. Extensive skin burns can lead to tissue necrosis, sepsis, and even death. Anti-infectious care of burn wounds is a major challenge in clinical medicine. However, the extensive use of antibiotics led to the emergence of multi-drug-resistant bacteria and silver dressings with antibacterial effects are also cytotoxic. We used the natural cationic antibacterial agent ε-polylysine (EPL) to graft Epigallocatechin-3-gallate (EGCG) to synthesize EPL-EGCG. Then, we used methacrylated gelatin (GelMA) with arginine-glycine-aspartate-rich acid (RGD) sequence and EPL-EGCG form interpenetrating polymer network hydrogels with excellent swelling properties. The hydrogel's inherent antibacterial properties and photo-cross-linking properties can cover irregular burn wounds and isolate bacteria to prevent infection. In addition, we used polydopamine (PDA) to coat GelMA microspheres with excellent hemostatic efficacy and load platelet-rich plasma (PRP) to enhance the hemostatic efficacy of the microspheres and impart inflammation-regulating functions. The hydrogel showed excellent hemostatic efficacy in rat liver injury and tail vein injury models. In the rat infected burn model, the hydrogel exhibited favorable antimicrobial, pro-angiogenic, and anti-inflammatory phenotype polarization of macrophages. Our study shows that GelMA/EPL-EGCG/GM-PDA@PRP hydrogel application has excellent antibacterial, hemostatic and anti-inflammatory effects, providing a new treatment strategy for wound care before burn skin grafting.

Casein-based hydrogels: Advances and prospects

Casein-based hydrogels (Casein Gels) possess advantageous properties, including mechanical strength, stability, biocompatibility, and even adhesion, conductivity, sensing capabilities, as well as controlled-releasing behavior of drugs. These features are attributed to their gelation methods and functionalization with various polymers. Casein Gels is an important protein-based material in the food industry, in terms of dairy and functional foods, biological and medicine, in terms of carrier for bioactive and sensitive drugs, wound healing, and flexible sensors and wearable devices. Herein, this review aims to highlight the importance of the features mentioned above via a comprehensive investigation of Casein Gels through multiple directions and dimensional applications. Firstly, the composition, structure, and properties of casein, along with the gelation methods employed to create Casein Gels are elaborated, which serves as a foundation for further exploration. Then, the application progresses of Casein Gels in dairy products, functional foods, medicine, flexible sensors and wearable devices, are thoroughly discussed to provide insights into the diverse fields where Casein Gels have shown promise and utility. Lastly, the existing challenges and future research trends are highlighted from an interdisciplinary perspective. We present the latest research advances of Casein Gels and provide references for the development of multifunctional biomass-based hydrogels.

Functional hemostatic hydrogels: design based on procoagulant principles

Uncontrolled hemorrhage results in various complications and is currently the leading cause of death in the general population. Traditional hemostatic methods have drawbacks that may lead to ineffective hemostasis and even the risk of secondary injury. Therefore, there is an urgent need for more effective hemostatic techniques. Polymeric hemostatic materials, particularly hydrogels, are ideal due to their biocompatibility, flexibility, absorption, and versatility. Functional hemostatic hydrogels can enhance hemostasis by creating physical circumstances conducive to hemostasis or by directly interfering with the physiological processes of hemostasis. The procoagulant principles include increasing the concentration of localized hemostatic substances or establishing a physical barrier at the physical level and intervention in blood cells or the coagulation cascade at the physiological level. Moreover, synergistic hemostasis can combine these functions. However, some hydrogels are ineffective in promoting hemostasis or have a limited application scope. These defects have impeded the advancement of hemostatic hydrogels. To provide inspiration and resources for new designs, this review provides an overview of the procoagulant principles of hemostatic hydrogels. We also discuss the challenges in developing effective hemostatic hydrogels and provide viewpoints.

Synthesis of Poly-γ-Glutamic Acid and Its Application in Biomedical Materials

Poly-γ-glutamic acid (γ-PGA) is a natural polymer composed of glutamic acid monomer and it has garnered substantial attention in both the fields of material science and biomedicine. Its remarkable cell compatibility, degradability, and other advantageous characteristics have made it a vital component in the medical field. In this comprehensive review, we delve into the production methods, primary application forms, and medical applications of γ-PGA, drawing from numerous prior studies. Among the four production methods for PGA, microbial fermentation currently stands as the most widely employed. This method has seen various optimization strategies, which we summarize here. From drug delivery systems to tissue engineering and wound healing, γ-PGA's versatility and unique properties have facilitated its successful integration into diverse medical applications, underlining its potential to enhance healthcare outcomes. The objective of this review is to establish a foundational knowledge base for further research in this field.

Bioadhesives with Antimicrobial Properties

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

Advances in preparation and application of antibacterial hydrogels

Bacterial infections, especially those caused by drug-resistant bacteria, have seriously threatened human life and health. There is urgent to develop new antibacterial agents to reduce the problem of antibiotics. Biomedical materials with good antimicrobial properties have been widely used in antibacterial applications. Among them, hydrogels have become the focus of research in the field of biomedical materials due to their unique three-dimensional network structure, high hydrophilicity, and good biocompatibility. In this review, the latest research progresses about hydrogels in recent years were summarized, mainly including the preparation methods of hydrogels and their antibacterial applications. According to their different antibacterial mechanisms, several representative antibacterial hydrogels were introduced, such as antibiotics loaded hydrogels, antibiotic-free hydrogels including metal-based hydrogels, antibacterial peptide and antibacterial polymers, stimuli-responsive smart hydrogels, and light-mediated hydrogels. In addition, we also discussed the applications and challenges of antibacterial hydrogels in biomedicine, which are expected to provide new directions and ideas for the application of hydrogels in clinical antibacterial therapy.

High-strength, antibacterial, antioxidant, hemostatic, and biocompatible chitin/PEGDE-tannic acid hydrogels for wound healing

Natural polymer hydrogels are widely used in various aspects of biomedical engineering, such as wound repair, owing to their abundance and biosafety. However, the low strength and the lack of function restricted their development and application scope. Herein, we fabricated novel multifunctional chitin/PEGDE-tannic acid (CPT) hydrogels through chemical- and physical-crosslinking strategies, using chitin as the base material, polyethylene glycol diglycidyl ether (PEGDE) and tannic acid (TA) as crosslinking agents, and 90 % ethanol as the regenerative bath. CPT hydrogels maintained a stable three-dimensional porous structure with suitable water contents and excellent biocompatibility. The mechanical properties of hydrogels were greatly improved (tensile stress up to 5.43 ± 1.14 MPa). Moreover, CPT hydrogels had good antibacterial, antioxidant, and hemostatic activities and could substantially promote wound healing in a rat model of full-thickness skin defect by regulating inflammatory responses and promoting collagen deposition and blood vessel formation. Therefore, this work provides a useful strategy to fabricate novel multifunctional CPT hydrogels with excellent mechanical, antibacterial, antioxidant, hemostatic, and biocompatible properties. CPT hydrogels could be promising candidates for wound healing.

In situ forming injectable γ-poly(glutamic acid)/PEG adhesive hydrogels for hemorrhage control

Rapidly in situ forming adhesive hydrogels are promising candidates for efficient hemostasis due to their easy administration and minimal invasion. However, development of biocompatible and high-performance hemostatic hydrogels without any additional toxic agents remains a challenge. Herein, a series of novel injectable adhesive hydrogels based on N-hydroxysuccinimide (NHS) modified γ-poly(glutamic acid) (γPGA-NHS) and tetra-armed poly(ethylene glycol) amine (Tetra-PEG-NH₂) were developed. Among all samples, PGA₁₀-PEG₁₅ and PGA₁₀-PEG₂₀ hydrogels with higher PEG contents exhibited rapid gelation time (<20 s), strong mechanical strength (compression modulus up to ∼75 kPa), good adhesive properties (∼15 kPa), and satisfactory burst pressure (∼18-20 kPa). As a result, PGA₁₀-PEG₁₅ and PGA₁₀-PEG₂₀ hydrogels showed a remarkable reduction in hemostasis time and blood loss compared with gauze and fibrin glue. More importantly, the PGA₁₀-PEG₂₀ hydrogel was also successfully used to seal femoral arterial trauma. Subcutaneous implantation experiments indicated a good biocompatibility of the hydrogels in vivo. All these results strongly support that the developed PGA-PEG hydrogels could serve as promising hemostatic agents in emergency and clinical situations.