Microbial colonization and development of infections in wounds is a sign of chronicity. The prevailing approach to manage and treat these wounds involves dressings. However, these often fail in effectively addressing infections, as they struggle to both absorb exudates and maintain optimal local moisture. The system here presented was conceptualized with a three-layer design: the outer layer made of a fibrous polycaprolactone (PCL) film, to act as a barrier for preventing microorganisms and impurities from reaching the wound; the intermediate layer formed of a sodium alginate (SA) hydrogel loaded with ampicillin (Amp) for fighting infections; and the inner layer comprised of a fibrous film of PCL and polyethylene glycol (PEG) for facilitating cell recognition and preventing wound adhesion. Thermal evaluations, degradation, wettability and release behavior testing confirmed the system resistance overtime. The sandwich demonstrated the capability for absorbing exudates (≈70 %) and exhibited a controlled release of Amp for up to 24 h. Antimicrobial testing was performed against Staphylococcus aureus and Escherichia coli, as representatives of Gram-positive and Gram-negative bacteria: >99 % elimination of bacteria. Cell cytotoxicity assessments showed high cytocompatibility levels, confirming the safety of the proposed sandwich system. Adhesion assays confirmed the system ease of detaching without mechanical effort (0.37 N). Data established the efficiency of the sandwich-like system, suggesting promising applications in infected wound care.

As promising biomaterials, hydrogels are widely used in the medical engineering field, especially in wound repairing. Compared with traditional wound dressings, such as gauze and bandage, hydrogel could absorb and retain more water without dissolving or losing its three-dimensional structure, thus avoiding secondary injury and promoting wound healing. Chitosan and its derivatives have become hot research topics for hydrogel wound dressing production due to their unique molecular structure and diverse biological activities. In this review, the mechanism of wound healing was introduced systematically. The mechanism of action of chitosan in the first three stages of wound repair (hemostasis, antimicrobial properties and progranulation), the effect of chitosan deacetylation and the molecular weight on its performance are analyzed. Additionally, the recent progress in intelligent and drug-loaded chitosan-based hydrogels and the features and advantages of chitosan were discussed. Finally, the challenges and prospects for the future development of chitosan-based hydrogels were discussed.

Stable cartilage regeneration in immunocompetent animals remains a huge challenge, mainly ascribing to the in vivo implantation of tissue-engineered cartilage inevitably arousing inflammatory reactions, resulting in cartilage-specific extracellular matrix erosion, chondrogenic niche destruction, and chondrocyte deterioration. Herein, we developed an anti-inflammatory platform, namely, Cur/GelMA hydrogel, by loading a potent anti-inflammatory drug of curcumin (Cur) into gelatin methacryloyl (GelMA) hydrogel. The Cur/GelMA hydrogel exhibited satisfactory Cur release kinetics in vitro and exerted favorable anti-inflammatory effects when cocultured with lipopolysaccharide-induced RAW264.7 macrophages in vitro. Furthermore, the Cur/GelMA hydrogel showed gratifying biocompatibility and supported cartilage regeneration in vitro when colonized with rabbit- and goat-derived chondrocytes. In addition, the in vitro engineered cartilages in the Cur/GelMA hydrogel were able to maintain a cartilaginous phenotype and achieved stable cartilage regeneration when subcutaneously implanted in autologous rabbits and goats for 2 and 4 weeks compared to the GelMA hydrogel. Furthermore, our data revealed that the in vivo-generated cartilage in the Cur/GelMA group apparently alleviated the inflammatory reaction compared to its GelMA counterpart, suggesting that the locally released Cur endowed the Cur/GelMA hydrogel with potent anti-inflammatory capacity. This study provides a reliable anti-inflammatory platform for stable cartilage regeneration in immunocompetent animals, significantly advancing the clinical application of tissue-engineered cartilage.

Natural polymer gels with sensitivity to near-infrared (NIR) light have attracted the attention of scientists working on intelligent drug delivery systems. Compared to ultraviolet or visible light, NIR light has the advantages of strong trigger levels, deep penetration through affected tissues, and fewer side effects. Herein, we present a topical photothermal hydrogel for NIR-controlled drug delivery. The proposed DexIEM-GM-Laponite hydrogel was prepared through free radical polymerization of vinyl-functionalized dextran (DexIEM), vinyl-modified graphene oxide (GM), and Laponite; thereafter, the hydrogel was loaded with ciprofloxacin (CIP, an antibacterial drug) as a model drug. With the Laponite content increased, the density of crosslinking in the hydrogel increased, and its mechanical properties improved noticeably. Under NIR irradiation, the DexIEM-GM-Laponite hydrogel exhibited a photothermal property, where the surface temperature increased from 26.8 to 55.5 °C. The simulation of subcutaneous drug delivery experiments ex vivo showed that under the specified pork tissue thickness (2, 4, and 6 mm), the CIP release remained NIR-controllable. Additionally, the results of the antibacterial performance tests indicated the excellent antibacterial effect of the hydrogel, and the blood hemolysis ratio of the hydrogel was less than 5%, signifying good blood compatibility. This work will provide an avenue for the application of NIR light-responsive materials in antimicrobial therapy.