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Nanoparticles Affect the Immune System of Digestive Tract

Over the past 50 years, the anticaking agent E551 silicon dioxide or silica, has been extensively used in the food industry, and was believed to be safe for a long time. However, Researchers currently working on the National Research Programme “Opportunities and Risks of Nanomaterials” have learnt that these nanoparticles are capable of affecting the immune system of the digestive tract.

Credit: Swiss National Science Foundation (SNSF)

It guarantees that dry foods such as instant coffee, spice powder and instant soup retain good flow properties. “Synthetic amorphous silica”, the ultrafine powder obtained from quartz and bearing the E number E551, has been utilized for almost a century with no obvious cause for concern. “Previously it was assumed that these nanoparticles are completely inert,” explains Hanspeter Nägeli from the Institute for Pharmacology and Toxicology at the University of Zurich.

Awakening the self-defense mechanism

Recently, Nägeli and his colleagues working on the National Research Programme “Opportunities and Risks of Nanomaterials” (NRP 64) have discovered that these particles can activate specific certain immune cells.

We have demonstrated that inactive dendritic cells are stimulated in response to contact with nanosilica, triggering a reaction similar in nature to an inflammation.

Hanspeter Nägeli, the Institute for Pharmacology and Toxicology, the University of Zurich

Their findings are gaining interest since dendritic cells have a vital role to play in the immune system of the gut: They help in maintaining a dynamic balance between tolerance and defense reactions. Dendritic cells play a crucial role in the immune system’s fight against pathogens and toxins. They also coordinate the body’s favorable response to food agents or components of normal gut flora.

Through tests conducted with mouse cell cultures, the Researchers have demonstrated that dendritic cells ingest nanosilica into their cell interior. By doing this, they are awakened from their slumber and begin to release a signal molecule that causes an inflammation. The Researchers are not sure if these processes could cause the immunological balance of the human gut to incline towards increased defense responses. However, their findings could elucidate the observation that inflammatory gut illnesses appear to spread when instant products are consumed by more people.

It is not a case of triggering fear. Inflammatory gut illnesses are dependent on a range of factors.

Hanspeter Nägeli, the Institute for Pharmacology and Toxicology, the University of Zurich

The existence of nanosilica in food is considered to be no more than a tiny piece in the big jigsaw puzzle that makes up these complex illnesses. However, Nägeli indeed believes that his findings should enable individuals to be extra careful on how to use these particles in food,“Their mass use needs to be rethought,” write the Researchers in their article.

Improving risk evaluation

In a further publication, Nägeli directs criticism towards the existing safety assessment of nanosilica, “The toxicology analyses list no immunological criteria.” Additionally, tests dealing with the addition of particles to rat food have resulted in liver damage in the highest dosages, even though this was not considered in the risk evaluation. Although no link with nanosilica has in fact been established, one cannot be excluded, given the existing knowledge. “For this reason, we ask a principle of caution to be exercised, and for the tolerance level in food to be reexamined,” says Nägeli.

The research was performed at the University of Zurich and in association with EMPA, ETH Zurich and Bavarian Nordic.


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