Silver nanoparticles as a new generation of antimicrobials.

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Antimicrobial effects of silver nanoparticles

Here, we present a review of the antibacterial effects of silver nanomaterials, including proposed antibacterial mechanisms and possible toxicity to higher organisms. For purpose of this review, silver nanomaterials include silver nanoparticles, stabilized silver salts, silver–dendrimer, polymer and metal oxide composites, and silver-impregnated zeolite and activated carbon materials. While there is some evidence that silver nanoparticles can directly damage bacteria cell membranes, silver nanomaterials appear to exert bacteriocidal activity predominantly through release of silver ions followed (individually or in combination) by increased membrane permeability, loss of the proton motive force, inducing de-energization of the cells and efflux of phosphate, leakage of cellular content, and disruption DNA replication. Eukaryotic cells could be similarly impacted by most of these mechanisms and, indeed, a small but growing body of literature supports this concern. Most antimicrobial studies are performed in simple aquatic media or cell culture media without proper characterization of silver nanomaterial stability (aggregation, dissolution, and re-precipitation). Silver nanoparticle stability is governed by particle size, shape, and capping agents as well as solution pH, ionic strength, specific ions and ligands, and organic macromolecules—all of which influence silver nanoparticle stability and bioavailability. Although none of the studies reviewed definitively proved any immediate impacts to human health or the environment by a silver nanomaterial containing product, the entirety of the science reviewed suggests some caution and further research are warranted given the already widespread and rapidly growing use of silver nanomaterials.

https://link.springer.com/content/pdf/10.1007%2Fs11051-010-9900-y.pdf

A review of the antibacterial effects of silver nanomaterials and potential implications for human health and the environment

The antibacterial action of silver is utilized in numerous consumer products and medical devices. Metallic silver, silver salts, and also silver nanoparticles are used for this purpose. The state of research on the effect of silver on bacteria, cells, and higher organisms is summarized. It can be concluded that the therapeutic window for silver is narrower than often assumed. However, the risks for humans and the environment are probably limited.

Silver as Antibacterial Agent: Ion, Nanoparticle, and Metal

In this article, several applications of nanomaterials in food packaging and food safety are reviewed, including: polymer/clay nanocomposites as high barrier packaging materials, silver nanoparticles as potent antimicrobial agents, and nanosensors and nanomaterial-based assays for the detection of food-relevant analytes (gasses, small organic molecules and food-borne pathogens). In addition to covering the technical aspects of these topics, the current commercial status and understanding of health implications of these technologies are also discussed. These applications were chosen because they do not involve direct addition of nanoparticles to consumed foods, and thus are more likely to be marketed to the public in the short term.

Applications of nanotechnology in food packaging and food safety: Barrier materials, antimicrobials and sensors

Methods: After impregnation the nature of the impregnation was determined by transmission electron microscopy. Two series of polymer discs were then tested, one washed in deionized water and the other unwashed. In each series, half of the discs were coated with a plasma protein conditioning film. The serial plate transfer test was used as a screen for persisting activity. Bacterial adherence to the polymers and the rate of kill, and effect on planktonic bacteria were measured by chemiluminescence and viable counts. Release rates of silver ions from the polymers in the presence and absence of plasma was measured using inductively coupled plasma mass spectrometry (ICP-MS). Results: Tests for antimicrobial activity under various conditions showed mixed results, explained by the modes and rates of release of silver ions. While washing removed much of the initial activity there was continued release of silver ions. Unexpectedly, this was not blocked by conditioning film. Conclusions: The methodology allows for the first time silver impregnation (as opposed to coating) of medical polymers and promises to lead to an antimicrobial biomaterial whose activity is not restricted by increasing antibiotic resistance.

Silver nanoparticles and polymeric medical devices: a new approach to prevention of infection?

In this paper we present the synthesis of gold nanoparticles supported on silica using supercritical carbon dioxide (scCO 2 ). Average gold particle sizes ranged from 3.7 to 6.6 nm. We also demonstrate the flexibility of this supercritical fluid processing technique by successfully incorporating gold nanoparticles into polyamide, polypropylene and poly(tetrafluoroethylene) (PTFE). Under the conditions employed, it was found that dimethylacetylacetonato gold(III) (Au(acac)Me 2 ) produced samples with sufficiently high metal loadings which allowed in-depth sample analysis. Surprisingly, the fluorinated analogue, dimethylhexafluoroacetylacetonato gold(III) (Au(hfac)Me 2 ) did not yield samples suitable for characterisation. X-ray diffraction (XRD), transmission electron microscopy (TEM) and solid-state UV–vis were applied to determine average particle sizes and to confirm the nature of the metallic particles obtained. To date, scCO 2 processing is the only method known to us capable of both depositing and impregnating a wide range of substrates with gold nanoparticles.

Ben Wong

Papers

Silver nanoparticles and polymeric medical devices: a new approach to prevention of infection?

The preparation of gold nanoparticle composites using supercritical carbon dioxide

Plasticization and spraying of poly (DL‐lactic acid) using supercritical carbon dioxide: control of particle size