Nanosilver concerns raised by researchers

Danish researchers said the size of the nanoparticle is a crucial feature that determines the type and magnitude of the cellular response.

Part of the explanation is that the 20 nm particles are entering human cells but the 100 nm nanoparticles mainly remain outside the cell interacting with the plasma membrane.

Target intestinal cells​

Frank Kjeldsen, associate professor, department of Biochemistry and Molecular Biology at the University of Southern Denmark, said the dose and the cells studied was their choice.

“We looked at the intestine cells as it was logical – they are the cells exposed to nanomaterials when we eat,” ​he told FoodQualityNews.com.

“Our goal was to try and get a deeper understanding on the process involved in human cells exposed to nanomaterials. ​

“They are many other studies, but this is unique because it has a more detailed view on what proteins are affected and those that are not.”​

Silver nanoparticles are used as anti-bacterial agents or nanoclay coatings in food packaging.

They have been found in supplements that can be bought in the EU and Asia and in animal feed.  

Researchers looked at 3,000 proteins and 400 changed abundances – looking at these told them how the cell is affected by nanomaterials.

Exposure and dose size​

Kjeldsen and Verano-Braga said their research is conducted on human cells in a laboratory and is not based on living people.

They also said that they do not know how large a dose of nano-silver, a person must be exposed to for the emergence of cellular changes.

Using mass spectrometry-based proteomic technologies and complementary techniques (e.g., Western blotting and confocal laser scanning microscopy), the researchers presented insights into silver nanoparticle protein interaction.

It indicates that some unique cellular processes are driven by the size.

“The 100 nm nanoparticles exerted indirect effects via serine/threonine protein kinase (PAK), mitogen-activated protein kinase (MAPK), and phosphatase 2A pathways, and the 20 nm nanoparticles induced direct effects on cellular stress, including generation of reactive oxygen species and protein carbonylation​,” they said.

Kjeldsen said the toxicology study on cells in the lab cannot estimate the exposure in the environment.

“I am not going to say nanoparticles make you sick – that would be premature, there is a hint of something we need to be aware of but we may be exposed to less [than is harmful] but less, more often, on a daily basis.​

“Nanoparticles are not something we should be using without more knowledge. We need to find out more about nanoparticles because policies allow their use to a large extent.  ​

"They have been shown to offer beneficial properties when they are used in therapy to get a drug to a particular organ.​

“The regulations are not firm and the research is still in its infancy basis but it should raise a red flag until they are tested more thoroughly.”  ​

He said further work would look at whether nanoparticles can cross the blood brain barrier and if they can, what is the extent of the damage they can cause.

Source: ACS Nano

Online ahead of print, doi: 10.1021/nn4050744​

“Insights into the Cellular ResponseTriggered by Silver Nanoparticles Using Quantitative Proteomics​”

Authors: Thiago Verano-Braga, Rona Miethling-Graff, Katarzyna Wojdyla, Adelina Rogowska-Wrzesinska, Jonathan R. Brewer, Helmut Erdmann and Frank Kjeldsen