26 May 2015

Nanosilver and the future of antibiotics

Precious metals like silver and gold have biomedical properties that have been used for centuries, but how do these materials effectively combat the likes of cancer and bacteria without contaminating the patient and the environment?

These are the questions that researchers from Dalhousie University and the Canadian Light Source are trying to find out.

“Gold and silver are both exciting materials,” said Peng Zhang, Associate Professor of Chemistry at Dalhousie. “We can use gold to either detect or kill cancer cells. Silver is also excited and a very promising material as an antibacterial agents.”

Zhang said that if you compare silver to current antibiotics, silver does not show drug-resistant behaviour. “But with silver, so far, we are not finding that,” he added.

Finding out why silver is such a great antibacterial agent is the focus of Zhang’s research, recently published in the journal Langmuir.

“We want to understand the relationship between the atomic structure and bioactivity of nanosilver as to why it is so efficient at inhibiting bacterial activity. It’s a big puzzle.”

Zhang said it is very hard to understand what is happening at the atomic level. Using small nanosilver particles is the most effective way, because when you make silver small, you can expect higher activity because of the increased surface area.

This poses another problem however, as the nanosilver needs to be stabilized with a coating or the silver particles will bond together forming large pieces of silver that do not efficiently interact with the bacteria.

Zhang’s group used two different coatings to compare the effectiveness of the silver as an antibacterial agent. The first was a small amino acid coating and the other was a larger polymer coating. And after testing the interactions between the nanosilver and the bacteria, and looking at the atomic structure of nanosilver using the CLS and the Advanced Photon Source, the researchers were surprised to find that the thicker, larger polymer coating actually created a better delivery method for sliver to inhibit the bacteria.

“We proposed that the small amino acid coating would bind so tightly to the silver surface that it would be difficult for  the silver atoms to interact with the bacteria, whereas the polymers are actually very good at staying in place and still releasing sufficient amount of silver with the bacteria.”

Zhang said the next steps will be to find out if the nanosilver is actually attacking good cells in living systems before they can make any further progress on determining whether nanosilver is an effective and efficient antibactieral agent that could be used to cure human and animal diseases.

The atomic structure of nanosilver, revealed by synchrotron X-ray spectroscopy, is proving to be a determinant of silver’s antibacterial activity.
Padmos, J. Daniel, et al. "Impact of Protecting Ligands on Surface Structure and Antibacterial Activity of Silver Nanoparticles." Langmuir 31.12 (2015): 3745-3752.

About the CLS

About the Canadian Light Source Inc.: 
The CLS is the brightest light in Canada—millions of times brighter than even the sun—used by scientists to get incredibly detailed information about the structural and chemical properties of materials at the molecular level, with work ranging from mine tailing remediation to cancer research and cutting-edge materials development.

The CLS has hosted over 2,500 researchers from academic institutions, government, and industry from 10 provinces and 2 territories; delivered over 40,000 experimental shifts; received over 10,000 user visits; and provided a scientific service critical in over 1,500 scientific publications, since beginning operations in 2005. The CLS has over 200 full-time employees.

CLS operations are funded by Canada Foundation for Innovation, Natural Sciences and Engineering Research Council, Western Economic Diversification Canada, National Research Council of Canada, Canadian Institutes of Health Research, the Government of Saskatchewan and the University of Saskatchewan.

For more information visit the CLS website or contact: 

Mark Ferguson 
Communications Coordinator 
1 (306) 657-3739
mark.ferguson@lightsource.ca

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