Reactive Oxygen Species Suppressive Kraft Lignin-Gelatin Antioxidant Hydrogels for Chronic Wound Repair

Comparative Analysis of Antibacterial and Wound Healing Activities of Chitosan and Povidone-Iodine-Based Hydrogels

PURPOSE

This study aimed to compare the antibacterial and wound healing efficacies of chitosan hydrogel with povidone-iodine (PI) hydrogel.

METHODS

The in vitro antibacterial activities of chitosan and PI hydrogels against Staphylococcus aureus and Escherichia coli were evaluated. Nine 6- to 8-week-old male Sprague-Dawley rats were divided into plain, PI, and chitosan hydrogel groups. Each rat received two 10-mm full-thickness dorsal wounds using an excisional splinting model. Each wound was treated with 0.2 mL of gel thrice over the course of 3 postoperative weeks. Weekly observations were conducted, and at the end of the third postoperative week, the rats were killed for histopathological and quantitative polymerase chain reaction evaluations. Data analysis included both 2- and 1-way analyses of variance.

RESULTS

Chitosan hydrogel exhibited comparable in vitro antibacterial activity and a significantly enhanced in vivo wound closure rate compared with PI hydrogel. Three weeks after the surgery, the chitosan hydrogel group demonstrated marked differences in wound repair (P < 0.01). Histologically, increased collagen deposition was observed with chitosan hydrogel treatment. Immunohistochemistry for CD68 revealed a lower number of macrophages in the wounds treated with chitosan hydrogel. Quantitative polymerase chain reaction analysis indicated a superior collagen 1 to 3 ratio and reduced expression of proinflammatory cytokine mRNAs (interleukin 1b, interleukin 6, tumor necrosis factor α, and interferon γ) in the chitosan hydrogel group.

CONCLUSION

Chitosan hydrogel demonstrates the potential to serve as an effective alternative to PI hydrogel, providing enhanced wound healing capabilities while maintaining comparable antimicrobial properties.

Bio-Inspired Antioxidant Heparin-Mimetic Peptide Hydrogel for Radiation-Induced Skin Injury Repair

Radiotherapy is one of the most important means of cancer treatment, however, radiation can also cause adverse reactions and even serious injuries to the skin. Radiation-induced excess reactive oxygen species (ROS) production and inflammatory infiltration make skin wounds difficult to heal compared to normal skin injuries. Herein, an antioxidant heparin-mimetic peptide hydrogel (K16, KYKYEYEYAGEGDSS-4Sa) is designed for radiation-induced skin injury (RISI) repair. First, the K16 peptide can self-assemble into a hydrogel with a 3D mesh-like porous nanofiber structure, which can provide certain physical support for skin repair like extracellular matrix (ECM). Then, K16 hydrogel not only scavenges ROS and prevents radiation damage to cellular DNA, but also promotes cell proliferation, migration, and angiogenesis. Meanwhile, 4-sulfobenzoic acid (4Sa) modified at the N-terminal end of the K16 peptide can adsorb inflammatory cytokines, thus acting to eliminate inflammation at the wound site. In vivo experiments showed that K16 hydrogel can inhibit early wound degradation, reduce inflammatory infiltration, and promote angiogenesis and collagen deposition, thus promoting wound healing. Therefore, the K16 hydrogel designed in this study has good potential for application in the field of radiation-induced skin injury repair.

Lignins as Promising Renewable Biopolymers and Bioactive Compounds for High-Performance Materials

The recycling of biomass into high-value-added materials requires important developments in research and technology to create a sustainable circular economy. Lignin, as a component of biomass, is a multipurpose aromatic polymer with a significant potential to be used as a renewable bioresource in many fields in which it acts both as promising biopolymer and bioactive compound. This comprehensive review gives brief insights into the recent research and technological trends on the potential of lignin development and utilization. It is divided into ten main sections, starting with an outlook on its diversity; main properties and possibilities to be used as a raw material for fuels, aromatic chemicals, plastics, or thermoset substitutes; and new developments in the use of lignin as a bioactive compound and in nanoparticles, hydrogels, 3D-printing-based lignin biomaterials, new sustainable biomaterials, and energy production and storage. In each section are presented recent developments in the preparation of lignin-based biomaterials, especially the green approaches to obtaining nanoparticles, hydrogels, and multifunctional materials as blends and bio(nano)composites; most suitable lignin type for each category of the envisaged products; main properties of the obtained lignin-based materials, etc. Different application categories of lignin within various sectors, which could provide completely sustainable energy conversion, such as in agriculture and environment protection, food packaging, biomedicine, and cosmetics, are also described. The medical and therapeutic potential of lignin-derived materials is evidenced in applications such as antimicrobial, antiviral, and antitumor agents; carriers for drug delivery systems with controlled/targeting drug release; tissue engineering and wound healing; and coatings, natural sunscreen, and surfactants. Lignin is mainly used for fuel, and, recently, studies highlighted more sustainable bioenergy production technologies, such as the supercapacitor electrode, photocatalysts, and photovoltaics.

Lignin, the Lignification Process, and Advanced, Lignin-Based Materials

At a time when environmental considerations are increasingly pushing for the application of circular economy concepts in materials science, lignin stands out as an under-used but promising and environmentally benign building block. This review focuses (A) on understanding what we mean with lignin, i.e., where it can be found and how it is produced in plants, devoting particular attention to the identity of lignols (including ferulates that are instrumental for integrating lignin with cell wall polysaccharides) and to the details of their coupling reactions and (B) on providing an overview how lignin can actually be employed as a component of materials in healthcare and energy applications, finally paying specific attention to the use of lignin in the development of organic shape-memory materials.