Erythrocyte membrane-camouflaged nanoworms with on-demand antibiotic release for eradicating biofilms using near-infrared irradiation.

The increase in the number of resistant bacteria caused by the abuse of antibiotics and the emergence of biofilms significantly reduce the effectiveness of antibiotics. Bacterial infections are detrimental to our life and health. To reduce the abuse of antibiotics and treat biofilm-related bacterial infections, a biomimetic nano-antibacterial system, RBCM-NW-G namely, that controls the release of antibiotics through near infrared was prepared. The hollow porous structure and the high surface activity of nanoworms are used to realize antibiotic loading, and then, biomimetics are applied with red blood cell membranes (RBCM). RBCM-NW-G, which retains the performance of RBCM, shows enhanced permeability and retention effects. Fluorescence imaging in mice showed the effective accumulation of RBCM-NW-G at the site of infection. In addition, the biomimetic nanoparticles showed a longer blood circulation time and good biocompatibility. Anti-biofilm test results showed damage to biofilms due to a photothermal effect and a highly efficient antibacterial performance under the synergy of the photothermal effect, silver iron, and antibiotics. Finally, by constructing a mouse infection model, the great potential of RBCM-NW-G in the treatment of in vivo infections was confirmed.

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 FSHPs­silver 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.

An injectable self-healing hydrogel with adhesive and antibacterial properties effectively promotes wound healing.

Hydrogels with self-healing capacity can undergo self-repair, establishing safer and longer-lasting products. Hydrogel wound dressings showing self-healing capacity can prolong the lifespan of the material and provide better wound protection. Therefore, in this study, Schiff base reactions (reversible imine linkages) were utilized to design injectable self-healing hydrogels with chitosan and konjac glucomannan. Oxidized konjac glucomannan was used to react with chitosan to form hydrogel. In addition to injectable, self-healing properties, the hydrogels also had adhesive and antibacterial properties, were biocompatible, and promoted wound healing. The inhibition rates of hydrogels against Staphylococcus aureus and Escherichia coli were 96% and 98%, respectively. In addition, microscopy and rheological analyses showed that the hydrogels healed within 4 h without additional exogenous stimulation. Finally, the developed hydrogels were injectable and significantly shortened wound recovery time in a full-thickness skin defect model. Thus, our findings established a novel hydrogel material that may have applications in wound healing.

Self-assembly of natural protein and imidazole molecules on gold nanoparticles: Applications in wound healing against multi-drug resistant bacteria.

Developing highly active and green antibacterial agents for pathogens, especially multidrug-resistant superbugs, is vital for solving the problem of serious antibiotic resistance. Herein, we report a unique system of gold nanoparticles coated with chicken egg white (CEW) and 2-mercapto-1-methylimidazole (MMT) as a novel antibacterial agent. The CEW was used to prepare the gold nanoparticles as a commercially available reducing and stabilizing agent, and then the MMT self-assembled on the surface of nanoparticles. The resulting Au@CEW/MMT was found to be a highly efficient antibacterial agent, and the activity is mainly attributed to the synergistic effects of MMT and Au@CEW in undermining the bacterial membrane. Meanwhile, the studies of antibacterial activities and biocompatibility of Au@CEW/MMT with different ratios of MMT conjugation to Au@CEW confirmed that Au@CEW/MMT3 (MMT:HAuCl4 = 1:50) can maintain a balance between antibacterial properties and biocompatibility. Furthermore, in an in-vivo study using the rabbit model, gauze loaded with Au@CEW/MMT3 can effectively accelerate the healing of wounds infected with methicillin-resistant S. aureus and promote the formation of collagen. Therefore, this work illustrated a promising material with broad-spectrum antibacterial activities for preclinical applications in treating wound infections.

Imidazole-molecule-capped chitosan-gold nanocomposites with enhanced antimicrobial activity for treating biofilm-related infections.

Biofilms that are widely associated with persistent bacterial infections impose a heavy burden on patients primarily due to their formidable resistance to conventional antiseptic drugs and local immune defense. Here, we successfully synthesized functional gold nanocomposites (CS-Au@MMT) by reducing chloroauric acid in the presence of biocompatible chitosan polymers with cationic amine and the small molecule 2-mercapto-1-methylimidazole (MMT). The cationic amine allowed transport of the CS-Au@MMT to the negatively charged sites at the surface of bacterial cells though electrostatic adhesion, with synergistic effects from the gold nanoparticles and MMT then exerting a strong bactericidal effect to inhibit biofilm formation. For established mature biofilms, CS-Au@MMT was able to adhere to the biofilm surface to render nearby bacterial cells inactive, resulting in biofilm rupture. This allowed CS-Au@MMT to penetrate through the biofilm, leading to sustained damage and achieving biofilm elimination. Furthermore, the nanocomposites efficiently inhibited infections induced by mature biofilm in vivo. These findings indicated that the CS-Au@MMT nanocomposites provide ease of synthesis and fabrication, high bactericidal effect, and low toxicity; thus, they show potential as biofilm-disrupting agents for biomedical and industrial applications.

A novel wound dressing based on a Konjac glucomannan/silver nanoparticle composite sponge effectively kills bacteria and accelerates wound healing.

A novel Konjac glucomannan/silver nanoparticle (KGM/AgNP) composite sponge was successfully prepared via a simple 2-step method for biomedical applications as wound-healing materials. First, AgNPs were prepared with green deoxidizer egg white. Then, KGM powder was added to the AgNP solution and stirred vigorously, and the composite sponge was obtained by freeze-drying. The KGM/AgNP composite sponge showed excellent water absorption and water retention, and considerable mechanical properties. KGM/AgNP composite sponges displayed good antibacterial activity against test microorganisms. In vitro cytocompatibility testing showed that L929 cells could survive well in the presence of KGM/AgNPs, indicating that KGM/AgNPs have good cytocompatibility. Animal models showed that the KGM/AgNP composite sponges effectively accelerated wound healing, and histological findings showed that they promoted fibroblast growth and accelerated epithelialization. The experimental results showed that KGM/AgNP composite sponges have great potential in promoting wound healing.