Nanocellulose does not infiltrate cells

Nanocellulose is cellulose which has been chipped into tiny particles. Unlike many other nanomaterials, it cannot infiltrate cells and is thus safer.

The term nanomaterial refers to materials and substances which are formed by tiny particles, less than a hundred nanometres in size. They have special chemical and physical properties, and so they can be used in completely new ways.

Finnish forest industries are researching nanocellulose with great interest. Cellulose is the substance of which plants cell walls are made. For a hundred years, it has been used to produce first pulp and then paper and paperboard.

In these products, the cellulose in present as fibres with a length calculated in millimetres. In nanocellulose, the length of the particles can be 50 nanometres, which equals 0.00005 millimetres. Nanocellulose can be used to make paper with extraordinary strength, for example.

The safety of nanomaterials is causing concern in researchers, as nanomaterials are so small that they can infiltrate human cells. Nanomaterials are also new and thus all their properties are not known as yet.

Size does not always correlate with danger

Mr. Ali Harlin, Research Professor at the VTT Technical Research Centre, says that not all nanomaterials are dangerous. “Some are, some are not, just like in some cases the size of ten metres is dangerous, while in others it is not.”

To date, humankind has had bad experiences with new substances that have had unexpected side effects. “Therefore it is easy to demonize new things,” Harlin says.

Harlin stresses that the properties of cellulose are extremely well known. It is a biological substance and not toxic under any circumstances, for example.

The reason why nanomaterials can be dangerous is their tiny size. The Academy of Finland’s research news say that the environmental effects of nanomaterials are as yet unknown, since there is so little knowledge available about their safety.

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Mr. Ali Harlin, Research Professor at the VTT Technical Research Centre, says that not all nanomaterials are dangerous. “Some are, some are not. We have proved that nanocellulose is safe to use for the kind of purposes that have been envisaged for it.” Photo: Saku Ruusila

Some nanomaterials really are dangerous

Some nanomaterials really are dangerous. Many function as catalysts, causing other substances to react and oxidize other materials, for example.

A well-known example is titanium oxide. Nano-sized, it can cause lung inflammation. In the same way, nano-sized carbon is dangerous. That’s why chimney sweeps, for example, have traditionally been prone to cancer: coal dust contains nano-sized particles which can enter lung cells.

”So we may have a problem if any nanomaterial is spread into air as dust”, Harlin says. Inhaled substances can cause problems if the lungs cannot get rid of them.

As airborne dust, nanocellulose could catch fire. On the other hand, this is unlikely, as it is transported as paste; it also absorbs humidity very easily and is then transformed into a kind of gel.

It has been suggested that nanocellulose, because of its size, could be a health-risk like asbestos. However, asbestos fibres have a small hook with which they catch hold of lung tissue.

”Asbestos fibres are a bit like a longline used in fishing. Nanocellulose fibres do not have these hooks. If they end up in our lungs, the lung cilia will get rid of them with the help of mucus,” Harlin says.

Nanocellulose is researched and safe

No toxic compounds have been found in nanocellulose. Unlike nano carbon materials, nanocellulose cannot infiltrate cells. As it cannot get into cells, it cannot affect the genes inside the cells and thus cause hereditary changes.

Nanocellulose does not affect the reproduction of animals living in water, either. “People have tried to cause mutations in fish with nanocellulose, but none have occurred.”

It is often said about new products that they have not been thoroughly researched. “This is not the case with nanocellulose. We have thought about its safety since the first laboratory tests were made,” Harlin says.

The researchers involved in the studies have been medically monitored during the ten or so years since the work was started. There has been no indication so far that nanocellulose would be dangerous.

Open research creates trust

Harlin is especially happy that all nanocellulose studies have been open from the beginning. Any researches anywhere can report their own observations and compare them with the methods and results in other studies.

Currently, an international standard is being drafted for nano-scaled materials. It would define what they are and include, and what should be evaluated and verified in regard to nano technology. “This is a prerequisite for the categorization of nano products”, Harlin says.

Nanocellulose is already being used. Pharmaceutical industry compresses it into pills with the effective substance added,” Harlin says and continues: ”Obviously, it could not be used if it weren’t safe.”

”Paints and self-cleaning window glasses contain nanomaterials. Silicates used as additives in concrete are also nano-sized,” Harlin says.

In the treatment of asthma, inhalers are used to intentionally produce a mist of nano-sized particles. Otherwise the medication could not bring relief. Cigarettes have the opposite effect: they also cause nanoparticles to travel to the lungs, but the result is not beneficial.

Research and monitoring continues

Nanocellulose and its properties continue to be researched and evaluated. No one can say that it will be safe always and in all possible uses and forms.

Problems would be caused if several unexpected properties should emerge. This, of course, applies to all new materials and substances.

”We have proved that nanocellulose is safe to use for the kind of purposes that have been envisaged for it,” Harlin says.

Author

Krista Kimmo

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