Tag Archives: silver nanoparticles

Pomegranates, silver nanoparticles, and Persian carpets

One of the issues with adding silver nanoparticles to textiles is that they wash off and eventually enter our water supply. According to a Dec. 14. 2015 news item on Nanotechnology Now, Iranian scientists has devised a technique for affixing silver nanoparticles,

Iranian researchers produced laboratorial samples of antibacterial woolen fabrics by using nanoparticles which are able to preserve their properties even after five times of washing.

A Dec. 12, 2015 Iran Nanotechnology Initiative Council (INIC) press release, which originated the news item, provides more detail,

Nanoparticles used in the production of fabrics have been produced through a cost-effective method and by using environmentally-friendly materials.

The aim of the research was to obtain an eco-friendly method for the production and application of silver nanoparticles in carpet weaving industry to create antibacterial properties in the final product. The interesting point in this research is the application of pomegranate skin as the reducer in the process to produce nanoparticles.

Results showed that pigment extracted from pomegranate skin is able to be used in the production of silver nanoparticles. Therefore, this method decreases the application of chemical reducers in the synthesis of these nanoparticles, and it also decreases the environmental pollution. In addition, the synthesized nanoparticles preserve their antibacterial properties after being loaded on woolen fiber samples. Therefore, carpets woven by these fibers have antibacterial properties and no bacteria will grow on them.

After carrying out complementary tests and producing the fabrics and fibers at a large scale, the products can be used in carpet weaving industries and also in production of medical devices.

Based on the results, fabrics completed with silver nanoparticles synthesized at low ratio of pigment have antibacterial properties and they do not affect the color of samples. Fabric samples also conserve their antibacterial properties even after five times of washing. The decrease in pH value and increase in temperature improves exhaustion of silver nanoparticles on the wool.

Here’s a link to and a citation for the paper,

Novel method for synthesis of silver nanoparticles and their application on wool by Majid Nasiri Boroumand, Majid Montazer, Frank Simon, Jolanta Liesiene, Zoran Šaponjic, Victoria Dutschk. Applied Surface Science Volume 346, 15 August 2015, Pages 477–483 doi:10.1016/j.apsusc.2015.04.047

This paper is behind a paywall.

Smaller (20nm vs 110nm) silver nanoparticles are more likely to absorbed by fish

An Oct. 8, 2015 news item on Nanowerk offers some context for why researchers at the University of California at Los Angeles (UCLA) are studying silver nanoparticles and their entry into the water system,

More than 2,000 consumer products today contain nanoparticles — particles so small that they are measured in billionths of a meter.

Manufacturers use nanoparticles to help sunscreen work better against the sun’s rays and to make athletic apparel better at wicking moisture away from the body, among many other purposes.

Of those products, 462 — ranging from toothpaste to yoga mats — contain nanoparticles made from silver, which are used for their ability to kill bacteria. But that benefit might be coming at a cost to the environment. In many cases, simply using the products as intended causes silver nanoparticles to wind up in rivers and other bodies of water, where they can be ingested by fish and interact with other marine life.

For scientists, a key question has been to what extent organisms retain those particles and what effects they might have.

I’d like to know where they got those numbers “… 2,000 consumer products …” and “… 462 — ranging from toothpaste to yoga mats — contain nanoparticles made from silver… .”

Getting back to the research, an Oct. 7, 2015 UCLA news release, which originated the news item, describes the work in more detail,

A new study by the University of California Center for Environmental Implications of Nanotechnology has found that smaller silver nanoparticles were more likely to enter fish’s bodies, and that they persisted longer than larger silver nanoparticles or fluid silver nitrate. The study, published online in the journal ACS Nano, was led by UCLA postdoctoral scholars Olivia Osborne and Sijie Lin, and Andre Nel, director of UCLA’s Center for Environmental Implications of Nanotechnology and associate director of the California NanoSystems Institute at UCLA.

Nel said that although it is not yet known whether silver nanoparticles are harmful, the research team wanted to first identify whether they were even being absorbed by fish. CEIN, which is funded by the National Science Foundation, is focused on studying the effects of nanotechnology on the environment.

In the study, researchers placed zebrafish in water that contained fluid silver nitrate and two sizes of silver nanoparticles — some measuring 20 nanometers in diameter and others 110 nanometers. Although the difference in size between these two particles is so minute that it can only be seen using high-powered transmission electron microscopes, the researchers found that the two sizes of particles affected the fish very differently.

The researchers used zebrafish in the study because they have some genetic similarities to humans, their embryos and larvae are transparent (which makes them easier to observe). In addition, they tend to absorb chemicals and other substances from water.

Osborne said the team focused its research on the fish’s gills and intestines because they are the organs most susceptible to silver exposure.

“The gills showed a significantly higher silver content for the 20-nanometer than the 110-nanometer particles, while the values were more similar in the intestines,” she said, adding that both sizes of the silver particles were retained in the intestines even after the fish spent seven days in clean water. “The most interesting revelation was that the difference in size of only 90 nanometers made such a striking difference in the particles’ demeanor in the gills and intestines.”

The experiment was one of the most comprehensive in vivo studies to date on silver nanoparticles, as well as the first to compare silver nanoparticle toxicity by extent of organ penetration and duration with different-sized particles, and the first to demonstrate a mechanism for the differences.

Osborne said the results seem to indicate that smaller particles penetrated deeper into the fishes’ organs and stayed there longer because they dissolve faster than the larger particles and are more readily absorbed by the fish.

Lin said the results indicate that companies using silver nanoparticles have to strike a balance that recognizes their benefits and their potential as a pollutant. Using slightly larger nanoparticles might help make them somewhat safer, for example, but it also might make the products in which they’re used less effective.

He added that data from the study could be translated to understand how other nanoparticles could be used in more environmentally sustainable ways.

Nel said the team’s next step is to determine whether silver particles are potentially harmful. “Our research will continue in earnest to determine what the long-term effects of this exposure can be,” he said.

Here’s an image illustrating the findings,

Courtesy ACS Nano

Courtesy ACS Nano

Here’s a link to and a citation for the paper,

Organ-Specific and Size-Dependent Ag Nanoparticle Toxicity in Gills and Intestines of Adult Zebrafish by Olivia J. Osborne, Sijie Lin, Chong Hyun Chang, Zhaoxia Ji, Xuechen Yu, Xiang Wang, Shuo Lin, Tian Xia, and André E. Nel. ACS Nano, Article ASAP DOI: 10.1021/acsnano.5b04583 Publication Date (Web): September 1, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

Nano-alchemy: silver nanoparticles that look like and act like gold

This work on ‘nano-alchemy’ comes out of the King Abduhllah University of Science and Technology (KAUST) according to a Sept. 22, 2015 article by Lisa Zynga for phys.org (Note: A link has been removed),

In an act of “nano-alchemy,” scientists have synthesized a silver (Ag) nanocluster that is virtually identical to a gold (Au) nanocluster. On the outside, the silver nanocluster has a golden yellow color, and on the inside, its chemical structure and properties also closely mimic those of its gold counterpart. The work shows that it may be possible to create silver nanoparticles that look and behave like gold despite underlying differences between the two elements, and could lead to creating similar analogues between other pairs of elements.

“In some aspects, this is very similar to alchemy, but we call it ‘nano-alchemy,'” Bakr [Osman Bakr, Associate Professor of Materials Science and Engineering at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia] told Phys.org. “When we first encountered the optical spectrum of the silver nanocluster, we thought that we may have inadvertently switched the chemical reagents for silver with gold, and ended up with gold nanoparticles instead. But repeated synthesis and measurements proved that the clusters were indeed silver and yet show properties akin to gold. It was really surprising to us as scientists to find not only similarities in the color and optical properties, but also the X-ray structure.”

In their study, the researchers performed tests demonstrating that the silver and gold nanoclusters have very similar optical properties. Typically, silver nanoclusters are brown or red in color, but this one looks just like gold because it emits light at almost the same wavelength (around 675 nm) as gold. The golden color can be explained by the fact that both nanoclusters have virtually identical crystal structures.

The question naturally arises: why are these silver and gold nanoclusters so similar, when individual atoms of silver and gold are very different, in terms of their optical and structural properties? As Bakr explained, the answer may have to do with the fact that, although larger in size, the nanoclusters behave like “superatoms” in the sense that their electrons orbit the entire nanocluster as if it were a single giant atom. These superatomic orbitals in the silver and gold nanoclusters are very similar, and, in general, an atom’s electron configuration contributes significantly to its properties.

Here’s one of the images used to illustrate Zynga’s article and the paper published by the American Chemical Society,

(Left) Optical properties of the silver and gold nanoclusters, with the inset showing photographs of the actual color of the synthesized nanoclusters. The graph shows the absorption (solid lines) and normalized emission (dotted lines) spectra. (Right) Various representations of the X-ray structure of the silver nanocluster. Credit: Joshi, et al. ©2015 American Chemical Society

(Left) Optical properties of the silver and gold nanoclusters, with the inset showing photographs of the actual color of the synthesized nanoclusters. The graph shows the absorption (solid lines) and normalized emission (dotted lines) spectra. (Right) Various representations of the X-ray structure of the silver nanocluster. Credit: Joshi, et al. ©2015 American Chemical Society

I encourage you to read Zynga’s article in its entirety. For the more technically inclined, here’s a link to and a citation for the researchers’ paper,

[Ag25(SR)18]: The “Golden” Silver Nanoparticle by Chakra P. Joshi, Megalamane S. Bootharaju, Mohammad J. Alhilaly, and Osman M. Bakr.J. Am. Chem. Soc., 2015, 137 (36), pp 11578–11581 DOI: 10.1021/jacs.5b07088 Publication Date (Web): August 31, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

Wound healing with cellulose acetate nanofibres

This work on cellulose acetate nanofibres and wound healing (tested on mice) comes from Egypt according to an Aug. 10, 2015 news item on ScienceDaily,

People with diabetes mellitus often suffer from impaired wound healing. Now, scientists in Egypt have developed antibacterial nanofibres of cellulose acetate loaded with silver that could be used in a new type of dressing to promote tissue repair.

An Aug. 10, 2015 Inderscience Publishers press release on the Alpha Galileo website, which originated the news item, provides more detail about the research,

Thanaa Ibrahim Shalaby and colleagues, Nivan Mahmoud Fekry, Amal Sobhy El Sodfy, Amel Gaber El Sheredy and Maisa El Sayed Sayed Ahmed Moustafa, at Alexandria University, prepared nanofibres from cellulose acetate, an inexpensive and easily fabricated, semisynthetic polymer used in everything from photographic film to coatings for eyeglasses and even cigarette filters. It can be spun into fibres and thus used to make an absorbent and safe wound dressing. Shalaby and co-workers used various analytical techniques including scanning electron microscope (SEM) and Fourier-transform infrared (FTIR) spectroscopy to characterise their fibres in which they incorporated silver nanoparticles.

Having characterised the material the team then successfully tested its antibacterial activity against various strains of bacteria that might infect an open wound. They next used the material as a dressing on skin wounds on mice with diabetes and determined how quickly the wound healed with and without the nano dressing. The dressing absorbs fluids exuded by the wound, but also protects the wound from infectious agents while being permeable to air and moisture, the team reports. The use of this dressing also promotes collagen production as the wound heals, which helps to recreate normal skin strength and texture something that is lacking in unassisted wound healing in diabetes mellitus.

Here’s a link to and a citation for the paper,

Preparation and characterisation of antibacterial silver-containing nanofibres for wound healing in diabetic mice by Thanaa Ibrahim Shalaby; Nivan Mahmoud Fekry; Amal Sobhy El Sodfy; Amel Gaber El Sheredy; Maisa El Sayed Sayed Ahmed Moustafa. International Journal of Nanoparticles (IJNP), Vol. 8, No. 1, p. 82 2015 DOI: 10.1504/IJNP.2015.070346

This paper is behind a paywall although there are some exceptions.

Saving silver; a new kind of electrode

An Aug. 1, 2015 news item on Nanotechnology Now highlights work from Germany’s Helmholtz-Zentrum Berlin für Materialien und Energie (Helmholtz Zentrum Berlin),

The electrodes for connections on the “sunny side” of a solar cell need to be not just electrically conductive, but transparent as well. As a result, electrodes are currently made either by using thin strips of silver in the form of a coarse-meshed grid squeegeed onto a surface, or by applying a transparent layer of electrically conductive indium tin oxide (ITO) compound. Neither of these are ideal solutions, however. This is because silver is a precious metal and relatively expensive, and silver particles with nanoscale dimensions oxidise particularly rapidly; meanwhile, indium is one of the rarest elements on earth crust and probably will only continue to be available for a few more years.

Manuela Göbelt on the team of Prof. Silke Christiansen has now developed an elegant new solution using only a fraction of the silver and entirely devoid of indium to produce a technologically intriguing electrode. The doctoral student initially made a suspension of silver nanowires in ethanol using wet-chemistry techniques. She then transferred this suspension with a pipette onto a substrate, in this case a silicon solar cell. As the solvent is evaporated, the silver nanowires organise themselves into a loose mesh that remains transparent, yet dense enough to form uninterrupted current paths.

A July 31, 2015 Helmholtz Zentrum Berlin press release (also on EurekAlert), which originated the news item, describes the work in more detail,

Subsequently, Göbelt used an atomic layer deposition technique to gradually apply a coating of a highly doped wide bandgap semiconductor known as AZO. AZO consists of zinc oxide that is doped with aluminium. It is much less expensive than ITO and just as transparent, but not quite as electrically conductive. This process caused tiny AZO crystals to form on the silver nanowires, enveloped them completely, and finally filled in the interstices. The silver nanowires, measuring about 120 nanometres in diameter, were covered with a layer of about 100 nanometres of AZO and encapsulated by this process.

Quality map calculated

Measurements of the electrical conductivity showed that the newly developed composite electrode is comparable to a conventional silver grid electrode. However, its performance depends on how well the nanowires are interconnected, which is a function of the wire lengths and the concentration of silver nanowires in the suspension. The scientists were able to specify the degree of networking in advance with computers. Using specially developed image analysis algorithms, they could evaluate images taken with a scanning electron microscope and predict the electrical conductivity of the electrodes from them.

“We are investigating where a given continuous conductive path of nanowires is interrupted to see where the network is not yet optimum”, explains Ralf Keding. Even with high-performance computers, it still initially took nearly five days to calculate a good “quality map” of the electrode. The software is now being optimised to reduce the computation time. “The image analysis has given us valuable clues about where we need to concentrate our efforts to increase the performance of the electrode, such as increased networking to improve areas of poor coverage by changing the wire lengths or the wire concentration in solution”, says Göbelt.

Practical aternative to conventional electrodes

“We have developed a practical, cost-effective alternative to conventional screen-printed grid electrodes and to the common ITO type that is threatened however by material bottlenecks”, says Christiansen, who heads the Institute of Nanoarchitectures for Energy Conversion at HZB and additionally directs a project team at the Max Planck Institute for the Science of Light (MPL).

Only a fraction of silver, nearly no shadow effects

The new electrodes can actually be made using only 0.3 grams of silver per square metre, while conventional silver grid electrodes require closer to between 15 and 20 grams of silver. In addition, the new electrode casts a considerably smaller shadow on the solar cell. “The network of silver nanowires is so fine that almost no light for solar energy conversion is lost in the cell due to the shadow”, explains Göbelt. On the contrary, she hopes “it might even be possible for the silver nanowires to scatter light into the solar cell absorbers in a controlled fashion through what are known as plasmonic effects.”

Here’s a link to and a citation for the paper,

Encapsulation of silver nanowire networks by atomic layer deposition for indium-free transparent electrodes by Manuela Göbelt, Ralf Keding, Sebastian W. Schmitt, Björn Hoffmann, Sara Jäckle, Michael Latzel, Vuk V. Radmilović, Velimir R. Radmilović,  Erdmann Spiecker, and Silke Christiansen. Nano Energy Volume 16, September 2015, Pages 196–206 doi:10.1016/j.nanoen.2015.06.027

This paper is behind a paywall.

Greening silver nanoparticles with lignin

A July 13, 2015 news item on phys.org highlights a new approach to making silver nanoparticles safer in the environment,

North Carolina State University researchers have developed an effective and environmentally benign method to combat bacteria by engineering nanoscale particles that add the antimicrobial potency of silver to a core of lignin, a ubiquitous substance found in all plant cells. The findings introduce ideas for better, greener and safer nanotechnology and could lead to enhanced efficiency of antimicrobial products used in agriculture and personal care.

A July 13, 2015 North Carolina State University (NCSU) news release (also on EurekAlert), which originated the news item, adds a bit more information,

As the nanoparticles wipe out the targeted bacteria, they become depleted of silver. The remaining particles degrade easily after disposal because of their biocompatible lignin core, limiting the risk to the environment.

“People have been interested in using silver nanoparticles for antimicrobial purposes, but there are lingering concerns about their environmental impact due to the long-term effects of the used metal nanoparticles released in the environment,” said Velev, INVISTA Professor of Chemical and Biomolecular Engineering at NC State and the paper’s corresponding author. “We show here an inexpensive and environmentally responsible method to make effective antimicrobials with biomaterial cores.”

The researchers used the nanoparticles to attack E. coli, a bacterium that causes food poisoning; Pseudomonas aeruginosa, a common disease-causing bacterium; Ralstonia, a genus of bacteria containing numerous soil-borne pathogen species; and Staphylococcus epidermis, a bacterium that can cause harmful biofilms on plastics – like catheters – in the human body. The nanoparticles were effective against all the bacteria.

The method allows researchers the flexibility to change the nanoparticle recipe in order to target specific microbes. Alexander Richter, the paper’s first author and an NC State Ph.D. candidate who won a 2015 Lemelson-MIT prize, says that the particles could be the basis for reduced risk pesticide products with reduced cost and minimized environmental impact.

“We expect this method to have a broad impact,” Richter said. “We may include less of the antimicrobial ingredient without losing effectiveness while at the same time using an inexpensive technique that has a lower environmental burden. We are now working to scale up the process to synthesize the particles under continuous flow conditions.”

I don’t quite understand how the silver nanoparticles/ions are rendered greener. I gather the lignin is harmless but where do the silver nanoparticles/ions go after they’ve been stripped of their lignin cover and have killed the bacteria? I did try reading the paper’s abstract (not much use for someone with my science level),

Silver nanoparticles have antibacterial properties, but their use has been a cause for concern because they persist in the environment. Here, we show that lignin nanoparticles infused with silver ions and coated with a cationic polyelectrolyte layer form a biodegradable and green alternative to silver nanoparticles. The polyelectrolyte layer promotes the adhesion of the particles to bacterial cell membranes and, together with silver ions, can kill a broad spectrum of bacteria, including Escherichia coli, Pseudomonas aeruginosa and quaternary-amine-resistant Ralstonia sp. Ion depletion studies have shown that the bioactivity of these nanoparticles is time-limited because of the desorption of silver ions. High-throughput bioactivity screening did not reveal increased toxicity of the particles when compared to an equivalent mass of metallic silver nanoparticles or silver nitrate solution. Our results demonstrate that the application of green chemistry principles may allow the synthesis of nanoparticles with biodegradable cores that have higher antimicrobial activity and smaller environmental impact than metallic silver nanoparticles.

If you can explain what happens to the silver nanoparticles, please let me know.

Meanwhile, here’s a link to and a citation for the paper,

An environmentally benign antimicrobial nanoparticle based on a silver-infused lignin core by Alexander P. Richter, Joseph S. Brown, Bhuvnesh Bharti, Amy Wang, Sumit Gangwal, Keith Houck, Elaine A. Cohen Hubal, Vesselin N. Paunov, Simeon D. Stoyanov, & Orlin D. Velev. Nature Nanotechnology (2015) doi:10.1038/nnano.2015.141 Published online 13 July 2015

This paper is behind a paywall.

Silver nanoparticle production at room temperature

I hadn’t thought silver nanoparticles were important to electronics but it seems I was wrongish. A July 2, 2015 news item on Nanowerk describes a breakthrough in silver nanoparticle production, which could increase its possible impact on electronics,

Engineers at Oregon State University [OSU] have invented a way to fabricate silver, a highly conductive metal, for printed electronics that are produced at room temperature.

There may be broad applications in microelectronics, sensors, energy devices, low emissivity coatings and even transparent displays.

A patent has been applied for on the technology, which is now available for further commercial development. The findings were reported in Journal of Materials Chemistry C. …

A July 1, 2015 OSU news release (also on EurekAlert), which originated the news item, expands on the theme of silver nanoparticles and electronics,

Silver has long been considered for the advantages it offers in electronic devices. Because of its conductive properties, it is efficient and also stays cool. But manufacturers have often needed high temperatures in the processes they use to make the devices, adding to their cost and complexity, and making them unsuitable for use on some substrates, such as plastics that might melt or papers that might burn.

This advance may open the door to much wider use of silver and other conductors in electronics applications, researchers said.

“There’s a great deal of interest in printed electronics, because they’re fast, cheap, can be done in small volumes and changed easily,” said Chih-hung Chang, a professor in the OSU College of Engineering. “But the heat needed for most applications of silver nanoparticles has limited their use.”

OSU scientists have solved that problem by using a microreactor to create silver nanoparticles at room temperatures without any protective coating, and then immediately printing them onto almost any substrate with a continuous flow process.

“Because we could now use different substrates such as plastics, glass or even paper, these electronics could be flexible, very inexpensive and stable,” Chang said. “This could be quite important and allow us to use silver in many more types of electronic applications.”

Among those, he said, could be solar cells, printed circuit boards, low-emissivity coatings, or transparent electronics. A microchannel applicator used in the system will allow the creation of smaller, more complex electronics features.

Here’s a link to and a citation for the paper,

Room temperature fabrication and patterning of highly conductive silver features using in situ reactive inks by microreactor-assisted printing by Chang-Ho Choi, Elizabeth Allan-Cole, and Chih-hung Chang. J. Mater. Chem. C, 2015, Advance Article DOI: 10.1039/C5TC00947B First published online 26 May 2015

I believe this paper is behind a paywall.

Silver nanoparticles and wormwood tackle plant-killing fungus

I’m back in Florida (US), so to speak. Last mentioned here in an April 7, 2015 post about citrus canker and zinkicide, a story about a disease which endangers citrus production in the US, this latest story concerns a possible solution to the problem of a fungus, which attacks ornamental horticultural plants in Florida. From a May 5, 2015 news item on Azonano,

Deep in the soil, underneath more than 400 plant and tree species, lurks a lethal fungus threatening Florida’s $15 billion a year ornamental horticulture industry.

But University of Florida plant pathologist G. Shad Ali has found an economical and eco-friendly way to combat the plant destroyer known as phytophthora before it attacks the leaves and roots of everything from tomato plants to oak trees.

Ali and a team of researchers with UF’s Institute of Food and Agricultural Sciences, along with the University of Central Florida and the New Jersey Institute of Technology, have found that silver nanoparticles produced with an extract of wormwood, an herb with strong antioxidant properties, can stop several strains of the deadly fungus.

A May 4, 2015 University of Florida news release, which originated the news item, describes the work in more detail,

“The silver nanoparticles are extremely effective in eliminating the fungus in all stages of its life cycle,” Ali said. “In addition, it has no adverse effects on plant growth.” [emphasis mine]

The silver nanoparticles measure 5 to 100 nanometers in diameter – about one one-thousandth the width of a human hair. Once the nanoparticles are sprayed onto a plant, they shield it from fungus. Since the nanoparticles display multiple ways of inhibiting fungus growth, the chances of pathogens developing resistance to them are minimized, Ali said. Because of that, they may be used for controlling fungicide-resistant plant pathogens more effectively.

That’s good news for the horticulture industry. Worldwide crop losses due to phytophthora fungus diseases are estimated to be in the multibillion dollar range, with $6.7 billion in losses in potato crops due to late blight – the cause of the Irish Potato Famine in the mid-1800s when more than 1 million people died – and $1 billion to $2 billion in soybean loss.

Silver nanoparticles are being investigated for applications in various industries, including medicine, diagnostics, cosmetics and food processing.  They already are used in wound dressings, food packaging and in consumer products such as textiles and footwear for fighting odor-causing microorganisms.

Other members of the UF research team were Mohammad Ali, a visiting doctoral student from the Quaid-i-Azam University, Islamabad, Pakistan; David Norman and Mary Brennan with the University of Florida’s Plant Pathology-Mid Florida Research and Education Center; Bosung Kim with the University of Central Florida’s chemistry department; Kevin Belfield with the College of Science and Liberal Arts at the New Jersey Institute of Technology and the University of Central Florida’s chemistry department.

Ali’s comment about silver nanoparticles not having any adverse effects on plant growth is in contrast to findings by Mark Wiesner and other researchers at  Duke University (North Carolina, US). From my Feb. 28, 2013 posting (which also features a Finnish-Estonia study showing no adverse effects from silver nanoparticles  in crustaceans),

… there’s a study from Duke University suggests that silver nanoparticles in wastewater which is later put to agricultural use may cause problems. From the Feb. 27, 2013 news release on EurekAlert,

In experiments mimicking a natural environment, Duke University researchers have demonstrated that the silver nanoparticles used in many consumer products can have an adverse effect on plants and microorganisms.

The main route by which these particles enter the environment is as a by-product of water and sewage treatment plants. [emphasis] The nanoparticles are too small to be filtered out, so they and other materials end up in the resulting “sludge,” which is then spread on the land surface as a fertilizer.

The researchers found that one of the plants studied, a common annual grass known as Microstegium vimeneum, had 32 percent less biomass in the mesocosms treated with the nanoparticles. Microbes were also affected by the nanoparticles, Colman [Benjamin Colman, a post-doctoral fellow in Duke’s biology department and a member of the Center for the Environmental Implications of Nanotechnology (CEINT)] said. One enzyme associated with helping microbes deal with external stresses was 52 percent less active, while another enzyme that helps regulate processes within the cell was 27 percent less active. The overall biomass of the microbes was also 35 percent lower, he said.

“Our field studies show adverse responses of plants and microorganisms following a single low dose of silver nanoparticles applied by a sewage biosolid,” Colman said. “An estimated 60 percent of the average 5.6 million tons of biosolids produced each year is applied to the land for various reasons, and this practice represents an important and understudied route of exposure of natural ecosystems to engineered nanoparticles.”

“Our results show that silver nanoparticles in the biosolids, added at concentrations that would be expected, caused ecosystem-level impacts,” Colman said. “Specifically, the nanoparticles led to an increase in nitrous oxide fluxes, changes in microbial community composition, biomass, and extracellular enzyme activity, as well as species-specific effects on the above-ground vegetation.”

Getting back to Florida, you can find Ali’s abstract here,

Inhibition of Phytophthora parasitica and P. capsici by silver nanoparticles synthesized using aqueous extract of Artemisia absinthium by Mohammad Ali, Bosung Kim, Kevin Belfield, David J. Norman, Mary Brennan, & Gul Shad Ali. Phytopathology  http://dx.doi.org/10.1094/PHYTO-01-15-0006-R Published online April 14, 2015

This paper is behind a paywall.

For anyone who recognized that wormwood is a constituent of Absinthe, a liquor that is banned in many parts of the world due to possible side effects associated with the wormwood, here’s more about it from the Wormwood overview page on WebMD (Note: Links have been removed),

Wormwood is an herb. The above-ground plant parts and oil are used for medicine.

Wormwood is used in some alcoholic beverages. Vermouth, for example, is a wine beverage flavored with extracts of wormwood. Absinthe is another well-known alcoholic beverage made with wormwood. It is an emerald-green alcoholic drink that is prepared from wormwood oil, often along with other dried herbs such as anise and fennel. Absinthe was popularized by famous artists and writers such as Toulouse-Lautrec, Degas, Manet, van Gogh, Picasso, Hemingway, and Oscar Wilde. It is now banned in many countries, including the U.S. But it is still allowed in European Union countries as long as the thujone content is less than 35 mg/kg. Thujone is a potentially poisonous chemical found in wormwood. Distilling wormwood in alcohol increases the thujone concentration.

Returning to the matter at hand, as I’ve noted previously elsewhere, research into the toxic effects associated with nanomaterials (e.g. silver nanoparticles) is a complex process.

MMA (mixed martial arts) and nano silver wound dressings

I had never, ever expected to mention mixed martial arts (MMA) here but that’s one of the delightful aspects of writing about nanotechnology; you never know where it will take you. A March 9, 2015 news item on Azonano describes the wound situation for athletes and a new product,


As an MMA Champion athlete, Rich Franklin knows all too well about germs and how easily they spread. During training he dealt with them on a regular basis, but it wasn’t until the first time he had staph, did he realize these infections could cost him a victory. Now, working in a global setting, Franklin trains in locations around the world which leaves him exposed to a plethora of bacteria and fungi. So he teamed up with American Biotech Labs (ABL) to develop Armor Gel, nano silver-based, wound dressing gel that can stay active on the skin for up to seventy-two hours (3 days). Using patented nano silver technology, Armor Gel has been scientifically tested to reduce the levels of bacteria and other pathogens, while forming a protective barrier “armor” over the wound. By shielding the body from external bacterial, the body’s natural healing process can be expedited. Its use is recommended by doctors, trainers, coaches, and athletes alike.

A March 6, 2015 ABL news release on BusinessWire, which originated the news item, provides a little more detail about Armor Gel,

Engineered for today’s modern athletes, Armor Gel is safe, nontoxic and provides a personal first line of defense. Already proven to reduce the levels of MRSA, VRE, pseudomonas aeruginosa, E. coli, A. niger and Candida albicans, Armor Gel is formulated using a unique and patented 24 SilverSol Technology®.

American Biotech Labs (ABL) was started in 2002 as a nano silver biotech company with the goal of creating a more stable and powerful silver technology for consumer products. …

I am providing a link to the product website (neither the link nor this post are endorsements), you can find out more about Armor Gel here.

Armor Gel was announced previously in a Sept. 16, 2014 ABL news release on PR Newswire, At the time no mention was made of Rich Franklin, their MMA athlete,

American Biotech Labs, LLC, is pleased to announce the availability of three new silver hydrogel wound-dressing products.  The new products will allow American Biotech Labs (ABL) to market in the wound-care market focusing on ultimate sports and fitness, spa and health, and animal markets.

The new over-the-counter (OTC) products will have wound-dressing claims for minor cuts, lacerations, abrasions, 1st and 2nd degree burns, and skin irritations.  The products also have pathogen-inhibiting barrier claims against pathogens, such as Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, MRSA and VRE, as well as fungi, such as Candida albicans and Aspergillus niger.  These new gels can provide a barrier that will help protect wounds for 24 to 72 hours.

The new products will be found under the names of Armor Gel™ (for the ultimate sports and fitness market), ASAP OTC™ (for the spa and health markets), and ASAP Pet Shield® (for the animal market).

Along with the release of these new products, ABL has formed a strategic alliance with Stuart Evey, founder and former chairman of ESPN, and Gary Bernstein, marketing executive and professional photographer and film maker.  ABL will utilize these talented individuals to help introduce these revolutionary new products to high-profile organizations in sports, pet stores, fashion and beauty, medical, and direct-marketing areas, etc.

Said Keith Moeller, ABL Director, “We are very grateful to the numerous top scientists, labs and universities that have helped move this amazing, patented, silver technology forward.  We believe that these products have the ability to impact the future of wound management worldwide.”

Note: Any statements released by American Biotech Labs, LLC that are forward looking are made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995.  Editors and investors are cautioned that forward looking statements invoke risk and uncertainties that may affect the company’s business prospects and performance.

You can find out more about ABL and its entire product line here.

Silver nanoparticle reference materials

When comparing silver nanoparticle toxicity studies, it would be good to know that the studies are all looking at the same type of nanoparticle. Happily, the US National Institute of Standards and Technology (NIST) has developed a silver nanoparticle reference material for just that purpose. From a March 5, 2015 news item on Azonano,

The National Institute of Standards and Technology (NIST) has issued a new silver nanoparticle reference material to support researchers studying potential environmental, health and safety risks associated with the nanoparticles, which are being incorporated in a growing number of consumer and industrial products for their antimicrobial properties. The new NIST test material is believed to be the first of its kind to stabilize the highly reactive silver particles in a freeze-dried, polymer coated, nanoparticle cake for long-term storage.

Nanoparticulate silver is a highly effective bactericide. It is, by some estimates, the most widely used nanomaterial in consumer products. These include socks and shoe liners (it combats foot odor), stain-resistant fabrics, coatings for handrails and keyboards, and a plethora of other applications.

The explosion of “nanosilver” products has driven a like expansion of research to better understand what happens to the material in the environment. “Silver nanoparticles transform, dissolve and precipitate back into nanoparticles again, combine or react with other materials—our understanding of these processes is limited,” says NIST chemist Vince Hackley. “However, in order to study their biological and environmental behavior and fate, one needs to know one is starting with the same material and not some modified or oxidized version. This new reference material targets a broad range of research applications.” [emphasis mine]

A March 3, 2015 NIST news release, which originated the news item, elaborates,

Silver nanoparticles are highly reactive. In the presence of oxygen or moisture they rapidly oxidize, subsequently releasing silver ions. This is the basis for their antimicrobial properties, but it also makes it difficult to create a standardized silver nanoparticle suspension with a long shelf life as a basis for doing comparative environmental studies. The new NIST product is the first to be stabilized by coating and freeze-drying—a technique commonly used in the pharmaceutical industry to preserve blood products and protein-based drugs. The NIST material uses polyvinylpyrrolidone (PVP), a polymer approved by the Food and Drug Administration for many uses, including as a food additive. The freeze-dried PVP-nanosilver cakes are flushed with an inert gas and sealed under a vacuum. Mixing the cake with water reconstitutes the original suspension.

NIST reference materials are designed to be homogeneous and stable. NIST provides the best available estimates for key properties of reference materials. In this case those include the mean silver particle size measured by four different methods, the total silver mass per vial, and the percentage distribution of nanoparticle sizes. The particles have a nominal diameter of 75 nanometers. NIST expects the material to be stable indefinitely when properly stored and handled, but will continue to monitor it for substantive changes in the reported values.

More information on NIST RM 8017, “Polyvinylpyrrolidone Coated Silver Nanoparticles” is available at https://www-s.nist.gov/srmors/view_report.cfm?srm=8017.

Given this development, I’m beginning to question all of the silver studies I’ve seen previously.