In situ reduction of silver nanoparticles by gelatin to obtain porous silver nanoparticle/chitosan composites with enhanced antimicrobial and wound-healing activity.

The identification of materials with beneficial properties for wound healing is a major research goal. In this study, gelatin was used as a reducing agent and stabilizer to restore silver nanoparticles (AgNPs) in situ, which were mixed with chitosan (CS), crosslinked with tannic acid, and then freeze-dried to obtain a new composite Gelatin/CS/Ag. Gelatin/CS/Ag has a dense pore structure with a pore size of about 100-250 μm. The pores were interconnected. The existence of AgNPs was proven by UV visible spectrophotometry, XRD, and electron microscopy. Gelatin/CS/Ag exhibited good mechanical properties, water absorption, and moisture retention. The material was evaluated in antibacterial experiments, and a good inhibitory effect of Gelatin/CS/Ag was observed. Gelatin/CS/Ag co-cultured with L929 cells did not show cytotoxicity. Finally, Gelatin/CS/Ag promoted wound healing and showed good biocompatibility. In summary, Gelatin/CS/Ag has promising antibacterial and wound healing properties.

Ye H ，Cheng J ，Yu K 《-》

Silver nanoparticles in situ synthesized by polysaccharides from Sanghuangporus sanghuang and composites with chitosan to prepare scaffolds for the regeneration of infected full-thickness skin defects.

In recent years, silver nanoparticles have widely been used in antibacterial dressings to solve antibiotic resistance problems. However, traditional methods for reducing silver nanoparticles are usually toxic. To overcome this problem, Sanghuangporus sanghuang polysaccharides (FSHPs) were used as a green reducing agent to prepare silver nanoparticles (AgNPs) with a size of 3-35 nm. The FSHPs‑silver nanoparticles (FSHPs-Ag) composite with chitosan solution were then freeze-dried to obtain a porous sponge dressing of chitosan-FSHPs-Ag (CS-FSHPs-Ag). The internal pores of CS-FSHPs-Ag were between 50 and 100 μm and had good swelling and water retention properties, which could provide a moist environment for wounds. Based on the experimental results, the appropriate concentration of AgNPs required for CS-FSHPs-Ag to inhibit Escherichia coli and Staphylococcus aureus was determined. Moreover, there was no statistically significant difference between the material treatment and the blank control group, indicating that the material almost showed no toxicity to L929 cells. Finally, this material was used for dressing animal wounds. The results showed that the CS-FSHPs-Ag promoted wound contraction and internal tissue growth better than the wounds treated with Aquacel® Ag, which indicated that the CS-FSHPs-Ag has a great potential as an ideal wound dressing material.

Ran L ，Zou Y ，Cheng J ，Lu F ... -  《-》

Silver nanoparticle impregnated chitosan-PEG hydrogel enhances wound healing in diabetes induced rabbits.

Non-healing wounds are among the serious complications of type-2-diabetes around the globe, associated with high incidence of bacterial infection, chronic nerve and blood vessel damage, and eventually repeated amputation of limbs and organs. Silver nanoparticles offer strong wound healing potential due to their well-known antibacterial activities. The present study reports the development of silver nanoparticle impregnated chitosan-poly ethylene glycol (PEG) hydrogel to accelerate wound healing in diabetic patients. The aim of the study was to formulate a sustained and slow release of silver nanoparticle using chitosan-PEG-Silver Nitrate based hydrogel for the treatment of chronic diabetic wounds. The silver nanoparticle containing chitosan-PEG pre-polymer solution was synthesized by reducing silver nitrate with PEG and chitosan solution, thereby, transforming the silver ions into silver nanoparticles. The resulted pre-polymer solution was then crosslinked using glutaraldehyde to form the desired hydrogel. The developed silver nanoparticle impregnated chitosan hydrogel was characterized using ultra-violet (UV) visible spectrophotometry, Fourier Transform-infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) followed by the determination of porosity, and swelling properties. The release of AgNPs from hydrogel was determined by UV-vis spectroscopy followed by antimicrobial and antioxidant assays. The wound healing efficacy of the synthesized hydrogel was evaluated in diabetic rabbits. The results demonstrated a higher porosity, higher degree of swelling and higher water vapor transition rate (WVTR) for silver nanoparticle impregnated hydrogel compared to bare chitosan-PEG hydrogel as well as improved antimicrobial and antioxidant properties in-vitro and enhanced wound healing capability in-vivo in diabetic rabbits. The hydrogel showed a slow and sustained release of AgNPs over a period of at least seven days manifesting the slow biodegradation of developed hydrogels. The improved antimicrobial, antioxidant and wound healing results indicate that the silver nanoparticle impregnated chitosan-PEG hydrogel can be a promising material for wound healing dressing for chronic diabetic wounds.

Masood N ，Ahmed R ，Tariq M ，Ahmed Z ，Masoud MS ，Ali I ，Asghar R ，Andleeb A ，Hasan A ... -  《-》

Study and evaluation of a gelatin- silver oxide nanoparticles releasing nitric oxide production of wound healing dressing for diabetic ulcer.

This study aimed to develop a novel Gelatin silver oxide material for releasing nitric oxide bionanocomposite wound dressing with enhanced mechanical, chemical, and antibacterial properties for the treatment of diabetic wounds. The gelatin- silver oxide nanoparticles (Ag2O-NP) bio nanocomposite was prepared using chitosan and gelatin polymers incorporated with silver oxide nanoparticles through the freeze-drying method. The samples were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. Results showed that the Ag2O-NP nanoparticles increased porosity, decreased pore size, and improved elastic modulus. The Ag2O-NP wound dressing exhibited the most effective antibacterial properties against Staphylococcus aureus and Escherichia coli. Among the samples, the wound dressing containing silver oxide nanoparticles demonstrated superior physical and mechanical properties, with 48% porosity, a tensile strength of 3.2 MPa, and an elastic modulus of 51.7 MPa. The fabricated wound dressings had a volume ratio of empty space to total volume ranging from 40% to 60%. In parallel, considering the complications of diabetes and its impact on the vascular system, another aspect of the research focused on developing a per2mediated wound dressing capable of releasing nitric oxide gas to regenerate damaged vessels and accelerate diabetic wound healing. Chitosan, a biocompatible and biodegradable polymer, was selected as the substrate for the wound dressing, and beta-glycerophosphate (GPβ), tripolyphosphate (TPP), and per2mediated alginate (AL) were used as crosslinkers. The chitosan-alginate (CS-AL) wound dressing exhibited optimal characteristics in terms of hole count and uniformity in the scanning electron microscope test. It also demonstrated superior water absorption (3854%) and minimal air permeability. Furthermore, the CS-AL sample exhibited an 80% degradation rate after 14 days, indicating its suitability as a wound dressing. The wound dressing was loaded with S-nitrosoglutathione (GSNO) powder, and the successful release of nitric oxide gas was confirmed through the grease test, showing a peak at a wavelength of 540 nm. Subsequent investigations revealed that the treatment of human umbilical vein endothelial cells (HUVECs) with high glucose led to a decrease in the expression of PER2 and SIRT1, while the expression of PER2 increased, which may subsequently enhance the expression of SIRT1 and promote cell proliferation activity. However, upon treatment of the cells with the modified materials, an increase in the expression of PER2 and SIRT1 was observed, resulting in a partial restoration of cell proliferative activity. This comprehensive study successfully developed per2-mediated bio-nanocomposite wound dressings with improved physical, mechanical, chemical, and antibacterial properties. The incorporation of silver oxide nanoparticles enhanced the antimicrobial activity, while the released nitric oxide gas from the dressing demonstrated the ability to mitigate vascular endothelial cell damage induced by high glucose levels. These advancements show promising potential for facilitating the healing process of diabetic wounds by addressing complications associated with diabetes and enhancing overall wound healing.

Li X ，Jiang X ，Gao F ，Zhou L ，Wang G ，Li B ，Gu S ，Huang W ，Duan H ... -  《-》

A novel antibacterial acellular porcine dermal matrix cross-linked with oxidized chitosan oligosaccharide and modified by in situ synthesis of silver nanoparticles for wound healing applications.

Not only are the physicochemical properties and biocompatibility of biomaterials important considerations, but also their antibacterial properties. In this study, a novel chemically-cross-linked antibacterial porcine acellular dermal matrix (pADM) scaffold was fabricated according to a two-step method. A naturally-derived oxidized chitosan oligosaccharide (OCOS) was used to cross-linked pADM (termed OCOS-pADM) to improve its physicochemical properties. Residual aldehyde groups within the OCOS-pADM were used in a redox reaction with Ag ions to produce Ag nanoparticles (AgNPs) in situ. As the AgNPs were tightly adhered onto the scaffold fibrils (termed OCOS-AgNPs-pADM), this effectively functionalized scaffold with antibacterial properties. The generated AgNPs were characterized by UV-Vis diffuse reflectance spectroscopy, XPS and SEM. The results of DSC, TG and enzymatic degradation demonstrated that OCOS-AgNPs-pADM possessed improved thermal stability and resistance to enzymatic degradation compared with pADM scaffolds. The kinetic experiment of the release of silver showed that silver was released in a controllable way. After introducing AgNPs into scaffolds, the OCOS-AgNPs-pADM possessed wide-spectrum antibacterial activity against Escherichia coli and Staphylococcus aureus. Furthermore, MTT assay and CLSM showed that the scaffolds had good biocompatibility. Pieces of OCOS-AgNPs-pADM were implanted into Sprague-Dawley rats to characterize their ability to repair full-thickness skin wounds. And results showed that the OCOS-AgNPs-pADM could accelerate the wound healing process. Overall, this work contributes new insight into the chemical cross-linking and functionalization of pADM scaffolds. In addition, as novel antibacterial scaffolds, OCOS-AgNPs-pADMs have the potential for development as wound dressing materials.

Chen Y ，Dan N ，Dan W ，Liu X ，Cong L ... -  《-》