In situ assembly of Ag nanoparticles (AgNPs) on porous silkworm cocoon-based would film: enhanced antimicrobial and wound healing activity.
ABSTRACT: 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 14?days 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.
Project description:Conventional wound dressings are difficult to apply to large total body surface area (TBSA) wounds, as they typically are prefabricated, require a layer of adhesive coating for fixation, and need frequent replacement for entrapped exudate. Large TBSA wounds as well as orthopedic trauma and low-resource surgery also have a high risk of infection. In this report, a sprayable and intrinsically adhesive wound dressing loaded with antimicrobial silver is investigated that provides personalized fabrication with minimal patient contact. The dressing is composed of adhesive and biodegradable poly(lactic-co-glycolic acid) and poly(ethylene glycol) (PLGA/PEG) blend fibers with or without silver salt (AgNO3). in vitro studies demonstrate that the PLGA/PEG/Ag dressing has antimicrobial properties and low cytotoxicity, with antimicrobial silver controllably released over 7-14?days. In a porcine partial-thickness wound model, the wounds treated with both antimicrobial and nonantimicrobial PLGA/PEG dressings heal at rates similar to those of the clinical, thin film polyurethane wound dressing, with similar scarring. However, PLGA/PEG adds a number of features beneficial for wound healing: greater exudate absorption, integration into the wound, a 25% reduction in dressing changes, and tissue regeneration with greater vascularization. There is also modest improvement in epidermis thickness compared to the control wound dressing.
Project description:Polymer hydrogels have been suggested as dressing materials for the treatment of cutaneous wounds and tissue revitalization. In this work, we report the development of a hydrogel composed of natural polymers (sodium alginate and gelatin) and silver nanoparticles (AgNPs) with recognized antimicrobial activity for healing cutaneous lesions. For the development of the hydrogel, different ratios of sodium alginate and gelatin have been tested, while different concentrations of AgNO3 precursor (1.0, 2.0, and 4.0 mM) were assayed for the production of AgNPs. The obtained AgNPs exhibited a characteristic peak between 430-450 nm in the ultraviolet-visible (UV-Vis) spectrum suggesting a spheroidal form, which was confirmed by Transmission Electron Microscopy (TEM). Fourier Transform Infra-red (FT-IR) analysis suggested the formation of strong intermolecular interactions as hydrogen bonds and electrostatic attractions between polymers, showing bands at 2920, 2852, 1500, and 1640 cm-1. Significant bactericidal activity was observed for the hydrogel, with a Minimum Inhibitory Concentration (MIC) of 0.50 µg/mL against Pseudomonas aeruginosa and 53.0 µg/mL against Staphylococcus aureus. AgNPs were shown to be non-cytotoxic against fibroblast cells. The in vivo studies in female Wister rats confirmed the capacity of the AgNP-loaded hydrogels to reduce the wound size compared to uncoated injuries promoting histological changes in the healing tissue over the time course of wound healing, as in earlier development and maturation of granulation tissue. The developed hydrogel with AgNPs has healing potential for clinical applications.
Project description:Developing effective and safe drugs is imperative for replacing antibiotics and controlling multidrug-resistant microbes. Nanoscale silicate platelet (NSP) and its nanohybrid, silver nanoparticle/NSP (AgNP/NSP), have been developed, and the nanohybrids show a strong and general antibacterial activity in vitro. Here, their efficacy for protecting Salmonella-infected chicks from fatality and septicemia was evaluated. Both orally administrated NSP and AgNP/NSP, but not AgNPs alone, effectively reduced the systemic Salmonella infection and mortality. In addition, quantitative Ag analyses demonstrated that Ag deposition from AgNP/NSP in the intestines was less than that from conventional AgNPs, indicating that the presence of NSP for immobilizing AgNPs reduced Ag accumulation in tissue and improved the safety of AgNPs. These in vivo results illustrated that both NSP and AgNP/NSP nanohybrid represent potential agents for controlling enteric bacterial infections.
Project description:Caseous lymphadenitis (CL) is an infectious and zoonotic disease characterized by the development of granulomas in the lymph nodes and internal organs of small ruminants. The etiological agent of this disease is Corynebacterium pseudotuberculosis, a Gram-positive and facultative intracellular bacterium. The conventional treatment for CL consists of drainage and chemical cauterization of the lesions using a 10% iodine solution. However, this type of treatment is not effective, due to iodine's cytotoxic profile and low antibacterial activity. Currently, silver nanoparticles (AgNPs) can be seen as an alternative treatment for CL due to their antimicrobial activity and wound healing effects. Therefore, the present study aimed to evaluate AgNPs as a post-surgical treatment for CL. Twenty-nine goats and sheep with clinical signs of CL were selected. Surgical intervention was performed to excise the caseous lesions. To treat the lesions, an ointment formulation based on AgNP mixed with natural waxes and oils was used in the experimental group, and the conventional treatment with 10% iodine was used in the control group. Bacteria were isolated from the excised caseous material. The animals were observed for 8 weeks after the surgical treatment, and blood samples were taken weekly. The surgical wounds of sheep treated with AgNP healed faster, and the surgical wound area was smaller during the observation period; the latter effect was also observed in goats. AgNP-treated animals also had less purulent discharge and less moisture in the surgical wounds. The AgNP-treated animals had lower leukocyte counts and lower titers of anti-C. pseudotuberculosis antibodies. There was no statistically significant difference between the groups with regard to the hemogram results. The results of the susceptibility testing of C. pseudotuberculosis strains (T1, 1002, FRC41, and VD57 strains) and clinical isolates to AgNPs showed growth inhibition, even at low concentrations. It can be concluded that post-surgical treatment of CL using the AgNP-based ointment may be a promising tool in the control of CL, through faster healing, decreased wound contamination, and no apparent toxic effects.
Project description:Silver nanoparticles (AgNPs) act as antibacterials by releasing monovalent silver (Ag(+)) and are increasingly used in consumer products, thus elevating exposures in human and wildlife populations. In vitro models indicate that AgNPs are likely to be developmental neurotoxicants with actions distinct from those of Ag(+). We exposed developing zebrafish (Danio rerio) to Ag(+) or AgNPs on days 0-5 post-fertilization and evaluated hatching, morphology, survival and swim bladder inflation. Larval swimming behavior and responses to different lighting conditions were assessed 24h after the termination of exposure. Comparisons were made with AgNPs of different sizes and coatings: 10nm citrate-coated AgNP (AgNP-C), and 10 or 50nm polyvinylpyrrolidone-coated AgNPs (AgNP-PVP). Ag(+) and AgNP-C delayed hatching to a similar extent but Ag(+) was more effective in slowing swim bladder inflation, and elicited greater dysmorphology and mortality. In behavioral assessments, Ag(+) exposed fish were hyperresponsive to light changes, whereas AgNP-C exposed fish showed normal responses. Neither of the AgNP-PVPs affected survival or morphology but both evoked significant changes in swimming responses to light in ways that were distinct from Ag(+) and each other. The smaller AgNP-PVP caused overall hypoactivity whereas the larger caused hyperactivity. AgNPs are less potent than Ag(+) with respect to dysmorphology and loss of viability, but nevertheless produce neurobehavioral effects that highly depend on particle coating and size, rather than just reflecting the release of Ag(+). Different AgNP formulations are thus likely to produce distinct patterns of developmental neurotoxicity.
Project description:Bionanocomposite packaging materials have a bright future for a broad range of applications in the food and biomedical industries. Antimicrobial packaging is one of the bionanocomposite packaging materials. Silver nanoparticle (AgNP) is one of the most attractive antimicrobial agents for its broad spectrum of antimicrobial activity against microorganisms. However, the traditional method of preparing AgNPs-functionalized packaging material is cumbersome and not environmentally friendly. To develop an efficient and convenient biosynthesis method to prepare AgNPs-modified bionanocomposite material for packaging applications, we synthesized AgNPs in situ in a silk fibroin solution via the reduction of Ag⁺ by the tyrosine residue of fibroin, and then prepared AgNPs-silk/poly(vinyl alcohol) (PVA) composite film by blending with PVA. AgNPs were synthesized evenly on the surface or embedded in the interior of silk/PVA film. The prepared AgNPs-silk/PVA film exhibited excellent mechanical performance and stability, as well as good antibacterial activity against both Gram-negative and Gram-positive bacteria. AgNPs-silk/PVA film offers more choices to be potentially applied in the active packaging field.
Project description:Infected superficial wounds were traditionally controlled by topical antibiotics until the emergence of antibiotic-resistant bacteria. Silver (Ag) is a kernel for alternative antibacterial agents to fight this resistance quandary. The present study demonstrates a method for immobilizing small-sized (~5 nm) silver nanoparticles on silica matrix to form a nanosilver-silica (Ag-SiO₂) composite and shows the prolonged antibacterial effects of the composite in vitro. The composite exhibited a rapid initial Ag release after 24 h and a slower leaching after 48 and 72 h and was effective against both methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli ( E . coli ). Ultraviolet (UV)-irradiation was superior to filter-sterilization in retaining the antibacterial effects of the composite, through the higher remaining Ag concentration. A gauze, impregnated with the Ag-SiO₂ composite, showed higher antibacterial effects against MRSA and E . coli than a commercial Ag-containing dressing, indicating a potential for the management and infection control of superficial wounds. Transmission and scanning transmission electron microscope analyses of the composite-treated MRSA revealed an interaction of the released silver ions with the bacterial cytoplasmic constituents, causing ultimately the loss of bacterial membranes. The present results indicate that the Ag-SiO₂ composite, with prolonged antibacterial effects, is a promising candidate for wound dressing applications.
Project description:To eliminate the microbial infection from an injury site, various modalities have been developed such as dressings and human skin substitutes. However, the high amount of reactive oxygen species, microbial infection, and damaging extracellular matrix remain as the main challenges for the wound healing process. In this study, for the first time, green synthesized silver nanoparticles (AgNPs) using Teucrium polium extract were embedded in poly lactic acid/poly ethylene glycol (PLA/PEG) film to provide absorbable wound dressing, with antioxidant and antibacterial features. The physicochemical analysis demonstrated, production of AgNPs with size approximately 32.2?nm and confirmed the presence of phytoconstituents on their surface. The antibacterial assessments exhibited a concentration-dependent sensitivity of Staphylococcus aureus and Pseudomonas aeruginosa toward biosynthesized AgNPs, which showed a suitable safety profile in human macrophage cells. Furthermore, oxidant scavenging assays demonstrated exploitation of plant extract as a reducing agent, endows antioxidant activity to biogenic AgNPs. The formation of PLA/PEG nanofilm and entrapment of AgNPs into their matrix were clearly confirmed by scanning electron microscopy. More importantly, antibacterial examination demonstrated that the introduction of biogenic AgNPs into PLA/PEG nanofibers led to complete growth inhibition of P. aeruginosa and S. aureus. In summary, the simultaneous antioxidant activity and antimicrobial activity of the novel biogenic AgNPs/PLA/PEG nanofilm showed its potential for application as wound dressing.
Project description:Silver nanoparticles (AgNPs) have been used as antimicrobials in a number of applications, including topical wound dressings and coatings for consumer products and biomedical devices. Ingestion is a relevant route of exposure for AgNPs, whether occurring unintentionally via Ag dissolution from consumer products, or intentionally from dietary supplements. AgNP have also been proposed as substitutes for antibiotics in animal feeds. While oral antibiotics are known to have significant effects on gut bacteria, the antimicrobial effects of ingested AgNPs on the indigenous microbiome or on gut pathogens are unknown. In addition, AgNP size and coating have been postulated as significantly influential towards their biochemical properties and the influence of these properties on antimicrobial efficacy is unknown. We evaluated murine gut microbial communities using culture-independent sequencing of 16S rRNA gene fragments following 28 days of repeated oral dosing of well-characterized AgNPs of two different sizes (20 and 110?nm) and coatings (PVP and Citrate). Irrespective of size or coating, oral administration of AgNPs at 10?mg/kg body weight/day did not alter the membership, structure or diversity of the murine gut microbiome. Thus, in contrast to effects of broad-spectrum antibiotics, repeat dosing of AgNP, at doses equivalent to 2000 times the oral reference dose and 100-400 times the effective in vitro anti-microbial concentration, does not affect the indigenous murine gut microbiome.
Project description:The increasing commercial production of engineered nanoparticles (ENPs) has led to concerns over the potential adverse impacts of these ENPs on biota in natural environments. Silver nanoparticles (AgNPs) are one of the most widely used ENPs and are expected to enter natural ecosystems. Here we examined the effects of AgNPs on germination and growth of eleven species of common wetland plants. We examined plant responses to AgNP exposure in simple pure culture experiments (direct exposure) and for seeds planted in homogenized field soils in a greenhouse experiment (soil exposure). We compared the effects of two AgNPs-20-nm polyvinylpyrrolidine-coated silver nanoparticles (PVP-AgNPs) and 6-nm gum arabic coated silver nanoparticles (GA-AgNPs)-to the effects of AgNO(3) exposure added at equivalent Ag concentrations (1, 10 or 40 mg Ag L(-1)). In the direct exposure experiments, PVP-AgNP had no effect on germination while 40 mg Ag L(-1) GA-AgNP exposure significantly reduced the germination rate of three species and enhanced the germination rate of one species. In contrast, 40 mg Ag L(-1) AgNO(3) enhanced the germination rate of five species. In general root growth was much more affected by Ag exposure than was leaf growth. The magnitude of inhibition was always greater for GA-AgNPs than for AgNO(3) and PVP-AgNPs. In the soil exposure experiment, germination effects were less pronounced. The plant growth response differed by taxa with Lolium multiflorum growing more rapidly under both AgNO(3) and GA-AgNP exposures and all other taxa having significantly reduced growth under GA-AgNP exposure. AgNO(3) did not reduce the growth of any species while PVP-AgNPs significantly inhibited the growth of only one species. Our findings suggest important new avenues of research for understanding the fate and transport of NPs in natural media, the interactions between NPs and plants, and indirect and direct effects of NPs in mixed plant communities.