Preventing infection in a wound is sometimes a difficult process, depending of course on the depth of the wound, what caused it, and even where you got hurt (your environment). Play a role in the bacteria that may be present and lead to infection. Often times particularly bad wounds require people to take antibiotics and certainly to apply topical antibiotics to their wounds to prevent and treat infection.

Today I am going to discuss an article that may be of interest to our resident crew of silver lovers (I still don't buy the safety of colloidal silver consumption, BTW. Silver nanoparticles are also quite toxic to humans [1. Despite my take on some applications of silver there is one thing that the science unequivocally supports and that's the topical application of silver on a surface kills bacteria. Today I am going to discuss an article where the authors generated a type of a paper that employs silver coated gold nano particles to kill bacteria.

Bandage Source

Today's article of discussion was published in the journal Nature: Scientific Reports on June 9, 2017 and is titled "Antibacterial cellulose paper made with silver-coated gold nanoparticles.".

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Cellulose and Silver Nanoparticles

Cellulose a plant based sugar used to make paper and even cellophane (the plastic wrapping around foods!) has an extremely wide range of applications in our modern civilization. From how our food is packaged, to how our wounds are bandaged cellulose plays a role in things that we use every day, many times in ways you wouldn't suspect. A variety of these applications involve packaging and when it comes to packaging our food, or a wound, keeping bacteria from growing is important! [3]

The researchers of this article sought to tackle the need for increased antibacterial properties in these packaging materials through employment of Silver nanoparticles. The antibacterial properties of silver nanoparticles has been getting increasing amounts of scientific attention as of late with researchers investigating where this property comes from.

It has been found that in many cases the silver nano particles leech out silver ions (Ag⁺) which have the ability of bacteria to replicate their DNA. [4] When there is no DNA replication, there can be no cellular division, so the bacterial population can't increase.

Previous work has shown that it is possible to combine silver nano particles with cellulose. [5] So the authors here decided to take things to the next level. Use this antibacterial silver nanoparticle cellulose technology, to create antibacterial paper. Note that this technology does not come with out it's risks as silver nanoparticles have been observed to have toxic effects in a variety of human tissues and cell types including [1], [6]:

skin, liver, lung, brain, vascular system, and other organs.

The authors acknowledge this while stating that (as any good scientist should) it is just evidence of the need for further work to limit the toxicity of these compounds and create safer more useful antibiotic constructs. The technology is interesting, but as usual, more work needs to be done! Let us discuss their results:

Creation of Silver Coated Gold Nanoparticles and The Cellulose

The authors first set out to attempt to create the nanoparticle structures that they would use to create the infused paper, they created particles of a few sizes (15 and 20 nM) and varying ratios of gold to silver in their composition.

Using visible light spectroscopy, and the absorptive properties of both gold nanoparticles of the size they created (20 nm particles for example absorb strongly 520 nM light), they confirmed that the particles were created, and that they were coated with silver (they observe this through an increase in absorbance and a shifting in the wavelength of light absorbed to 500 nm. (shown in the plot below!)

They then combined these particles with cellulose paper (they literally just pipetted it on there, this isn't complicated technology, the particles are tiny and get caught in the cellulose fibers). To make sure the particles were actually attached to the paper, they soaked the paper in water (so non affixed particles would come off) then took some images with a tunneling electron-microscope:

Seeing that the particles were attached and dispersed on the cellulose paper (though not as dispersed as they had hoped) they proceeded to see whether or not these papers had antimicrobial properties.

What you are looking at here are bacteria being grown on some agarose plates, with a piece of the nanoparticle paper laid overtop while the cells grew (or not). In (a) we are looking at just gold nanoparticles.. which didn't do anything to kill the bacteria. The next image to the right (c) we are looking at nanoparticles with a low amount of the silver (thats the 1000 gold/1 silver ratio), these particles also did NOT kill the bacteria, hmm. Finally in (e) we are seeing their particles with a 10 fold greater amount of silver, and these did result in significantly reduced bacterial growth. Nice.

Conclusions

The authors here presented a novel silver coated gold nanoparticle affixed paper, with antimicrobial properties. The result is interesting however there is one HUGE caveat stated by the authors:

It will also be necessary to examine the cytotoxicity and biocompatibility of these nanomaterials toward human cells before proposing their therapeutic use in cellulose composites.

At this stage, the evidence is fairly clear that silver nanoparticles pose a threat to damaging our cells (the silver ions leech out, its a problem) and significant testing against human cells would be necessary to ensure that these papers are not going to be toxic as well. It is possible that the incorporation of the particles on the cellulose could aide in preventing or lessening toxicity (to an acceptable level), but that will not be known with out further testing.

Nevertheless, the work is interesting, and the nanoparticle paper does indeed have antimicrobial properties. If the toxicity issues are dealt with, this could become a very attractive material for the creation of bandages with the ability to kill infections with out the use of topical antibiotics.

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Sources

1. http://www.sciencedirect.com/science/article/pii/S0009898110005139?via%3Dihub
2. https://www.nature.com/articles/s41598-017-03357-w
3. http://www.sciencedirect.com/science/article/pii/S007967001500074X?via%3Dihub
4. http://pubs.acs.org/doi/abs/10.1021/bm060721b
5. https://www.ncbi.nlm.nih.gov/pubmed/27178957?dopt=Abstract
6. https://link.springer.com/article/10.1007%2Fs11051-010-9900-y

All Non Cited Images Are From Pixabay.com or Flickr.com And Are Available Under Creative Commons Licenses

Any Gifs Are From Giphy.com and Are Also Available for Use Under Creative Commons Licences

Extra Image Sourcing

Nano Particle Image Source

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