Dayang Wu

In situ reduction of silver nanoparticles by chitosan-l-glutamic acid/hyaluronic acid: enhancing antimicrobial and wound-healing activity

Spongy composites with silver nanoparticles (AgNPs) were synthesized by freeze-drying a mixture of silver nitrate (AgNO3) and chitosan-l-glutamic acid (CG) derivative loaded with hyaluronic acid (HA) solution. CG/AgNP spongy composites had an interconnected porous structure and rough surfaces. When AgNPs (5-20nm) were immobilized on these spongy composites, AgNP aggregation was dependent on AgNO3 concentration. The spongy composites exhibited good mechanical properties, swelling, and water retention capacity. In vitro antibacterial activity showed that the CG/AgNP spongy composites effectively inhibited bacterial (Escherichia coli and Staphylococcus aureus) growth and penetration. Spongy composites containing low concentrations of AgNP were non-toxic to L929 cells, while CG/HA/AgNP spongy composites promoted wound healing, as determined by in vivo tests, wound contraction ratio, average healing time, and histological examination. These results indicate that the spongy composites can serve as effective antibacterial wound dressings.

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.

In situ assembly of Ag nanoparticles (AgNPs) on porous silkworm cocoon-based would film: enhanced antimicrobial and wound healing activity

Preventing wound infection and retaining an appropriate level of moisture around wounds represent the most critical issues in wound treatment. Towards these ends, special focus has been placed on Bombyx mori cocoons because the protective function of the silkworm cocoon resembles the manner in which the skin protects the human body. We have designed a facile technique to develop a novel silkworm cocoon-based wound film (SCWF) wound dressing utilizing a CaCl2-ethanol-H2O solution. To improve the anti-bacterial performance of SCWF, we have incorporated the ability of silk sericin to act as a reducing agent for the conversion of Ag+ to Ag, yielding nanoparticles (AgNPs) linked together by peptide bonds of silkworm cocoon wound film (SCWF-AgNPs). SCWF-AgNP dressing exhibited excellent biocompatibility, anti-bacterial performance, and good extensibility. Furthermore, in vivo experiments indicated that SCWF-AgNP dressing was able to significantly accelerate the healing rate of infected wounds in New Zealand White rabbits and histological examination revealed that it aided in the successful reconstruction of intact and thickened epidermis during 14u2009days of healing of impaired wound tissue. These results demonstrate that the present approach might shed new light on the design of anti-bacterial materials such as SCWF-AgNPs with promising applications in wound dressing.

Evaluation of artificial skin made from silkworm cocoons

The protective characteristics of silkworm cocoons are the result of thousands of years of evolution. In this study, we attempted to combine the cocoon’s protective characteristics with the function of human skin to explore the possibility of using silkworm cocoons in the field of artificial skin application. We retained the natural structure of the cocoon shells and softened it by a degumming process. This process was performed so that the mechanical and permeation properties of the cocoon material meet the criteria of artificial skin with respect to tension and suturing; the cocoon material was also found to have strong antibacterial activity and cell compatibility. These properties of the cocoon suggest that it has a high potential to be used as an artificial skin. Overall, we expect the silkworm cocoon to be a type of biological material with extensive possibilities of application as artificial skin.

Author Correction: In situ assembly of Ag nanoparticles (AgNPs) on porous silkworm cocoon-based wound film: enhanced antimicrobial and wound healing activity

A correction to this article has been published and is linked from the HTML version of this paper. The error has been fixed in the paper.

Thermal bonded cocoon laminates via simple hot-press treatment

The thin silkworm cocoon is potential for producing lightweight and tough engineering applications. In this paper, cocoon laminates were prepared by a simple hot pressing method, which are thermally bonded by its own sericin. After being hot pressed at 130xa0°C for 30xa0s, cocoon pieces get tightly compressed with a high fiber volume fraction of 64.4%, leading to tensile strength of the cocoon pieces enhancing from 32 to 111xa0MPa. Besides, mechanical properties of the cocoon laminate are improved for strong sericin bonding between cocoon pieces by increasing hot pressing time from 30 to 90xa0s. The resulting cocoon laminate exhibits the maximum stress of 70xa0MPa at 11.3% strain. The failure ascribes to the debonding rather than the fracture of cocoon overlaps. Importantly, the tensile toughness is better than that of the high-volume-fraction silk fabric-reinforced epoxy composite. Our study may show a bright prospect in developing lightweight and tough cocoon laminates for natural precursor materials.

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.

Dissolution behavior of silk fibroin in a low concentration CaCl 2 -methanol solvent: From morphology to nanostructure

Regenerated Silk biomaterials are usually pre-formed from silk fibroin solutions. However, the dissolution of silk fibroin in proper solvents by a simple and low cost way is still a challenge. Here, we employed a CaCl2-methanol solvent system with a very low CaCl2 concentration of 6wt% to dissolve silk fibroin. During the dissolution process, the evaporation of methanol cause the changing of solvation sheath of ions in the solvent. The remaining solvent with the incomplete solvation sheath is absorbed by the silk fiber and interacts with fibroin chains to complete the solvation sheath, which accounts for the dissolution of silk fibroin. Silk fibroin dissolution stops as all the solvation sheaths are complete. The final CaCl2 concentration is ca. 26% and silk fibroin is completely dissolved with a yield of about 90%. Silk fibroin is dissolved into multi-scale nanofibrils solution which is potential for producing regenerated silk fibroin materials for functional applications.

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:HAuCl4u202f=u202f1:50) 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.