Nanoparticles in nature: Toxic or harmless?

Andy Booth, SINTEF scientist and environmental chemist is interested in what nanotechnology is doing to the marine environment. A couple of years ago, he began to be interested in whether nanoparticles could be hazardous.

Now, Booth is leading a project called “The environmental fate and effects of SINTEF-produced nanoparticles”. The scientists will study both how the particles behave and how they affect organisms when they are released into the marine environment.

One of the goals of the project is to find out whether nanoparticles are toxic to marine organisms such as small crustaceans and animal plankton. Further down the road, the ability of cod larvae and other large organisms to tolerate nanoparticles will also be studied.

“Our experiments will tell us whether these tiny particles will be excreted or remain inside organisms, and if they do, how they will behave there,” explains Booth, who wants to make it clear that not all nanoparticles are necessarily dangerous. Many types of nanoparticles occur naturally in the environment, and have existed ever since the Earth was formed. For example, ash is a material that contains nanoparticles.

“What is new is that we are now capable of designing nanoparticles with a wide range of different properties. Such particles can be different from those that already occur in nature, and they are intended to perform specific tasks at our command, so we do not know how they will behave in nature. “This could potentially – and I say “potentially” because this topic is so new to science – indicate that these particles could be toxic under certain conditions. However, this depends on a number of factors, including their concentration and the combination of particles,” emphasises Booth.

“Has industry good enough tests to ensure that the nanoproducts that it releases in the market are good enough?”

“In the field of chemical analysis, we have standard tests that tell us whether or not a material is toxic. Today, there are no such tests of nanoparticles that are 100% accurate, so this is something that scientists are currently working on at international level,” says Booth, adding that he believes that it is extremely difficult to put products that are a danger to health on the market.

Survey of millions is essential

The nanoparticle concept is general, and includes many more than one type. There are millions of potential variants, Today, it is impossible to obtain an overview of how many there actually are, and some of them will be toxic, while others are harmless, just like other chemicals.

This is why Andy Booth and his 12-strong team at SINTEF have just launched their painstaking efforts. One of the biggest challenges they have faced so far is that of identifying scientific methods that will enable them to discover how these tiny particles behave in nature, and how they might affect natural processes.

Industrial breakthrough

Booth’s colleague Christian Simon and his research department at SINTEF Materials and Chemistry, has recently made the most important industrial breakthrough ever in nanoparticle technology, and in this case it looks as though nanosubstances could be environmentally friendly alternatives to chemicals.

One of Norway’s leading manufacturer of powders and paints, has started production of a new type of paint containing nanoparticles, and it has been developed by SINTEF.

The particles possess fluid characteristics that make the paint easy to apply. This means that a higher proportion of dry matter can be used, with correspondingly less solvent. Furthermore, the paint will dry rapidly and be more wear-resistant than normal paint.

“What is new is that we combine inorganic, tough, hard materials with organic, flexible, and formable materials when we create our nanoparticles. This gives us a new class of materials with improved properties; what are known as hybrid solutions. For example, we can make polymers with improved light stability that will also withstand scratches,” says Simon.

When a hollow nanoparticle is created, it is called a nanocapsule. The cavity can be filled with another material for subsequent release for any of a wide range of purposes. The SINTEF scientists have not come as far with nanocapsules as they have with nanoparticles, but they have developed a technology that can be used in several applications and they can produce nanocapsules on a large scale.

“For example, we can improve the durability of coatings for aircraft, ships and cars,” says Simon. “The components consist of substances that can close up cracks and scratches. Just think of vehicle bodywork. When gravel hits its surface, the enamel cracks and gets damaged. But simultaneously, the capsules inside the enamel burst and the material they contain will repair the damage.

“But what happens when materials painted with nanoparticles are demolished, chopped up or burnt? Will hazardous components escape to the environment?

“The particles have been produced in such a way that they create chemical bonds to the other components of the paint. When the paint is fully cured, therefore, the nanoparticles no longer exist, so they cannot separate from the polymer matrix when whatever has been painted is torn down, chopped up or burnt,” answers Christian Simon.

“Surgical” medical treatment

Hollow nanocapsules can also be used in medical treatments with almost “surgical” effects. They can be sent directly into the sick cells. Ruth Baumberger Schmidt and her team are working on this topic.

The scientists fill nanocapsules with medication, and steer them to wherever they want their contents to end up. They do this by binding special molecules to the coating. The capsule’s shell is broken when its immediate environment is right in terms of the selected trigger, such as temperature or acidity. According to how the capsule has been concocted, its contents can be allowed to leak out gradually over time, or at a higher rate at first and gradually less as time goes by.

At the moment, Ruth Schmidt and a group of SINTEF chemists are concentrating on medicines to fight cancer, a long-term project that offers important challenges. The use of nanocapsules inside the body makes serious demands of the materials used. The particles that are being developed for medical purposes must be non-toxic and need to be broken down into non-hazardous components that the body can excrete, for example via the urine. The capsules also need to head for the right site of action and to liberate their contents, without being discovered by “watchdogs” such as T cells and natural killer cells.

“In this case these capsules are a plus because here we want the capsules to pass through the cell membrane and do their work locally. Other types of nanoparticles can pass the membrane and become a danger to the body. The risk of nanotechnology is that sometimes they are not supposed to pass, or that they accumulate in large quantities over a period of time, instead of disappearing.

We don’t use nanotubes or nanofibres, because we believe that they are less safe than particles. But a lot of research is being done in this field.”

Uncertainty

So there is great potential, but also a high degree of uncertainty, is the conclusion. Can it be that nanotechnology was oversold when the subject emerged during the nineties? Were we simply blinded by its potential, with the result that we forgot to look out for its potential disadvantages?

Andy Booth and his colleagues carry on tirelessly with their experiments.

“When nanoparticles are released into rivers and lakes, it is a rather complicated matter to study how they will behave. Chemistry is different at nanometre level, and nanoparticles do not behave like normal particles,” says Booth.

“These particles also behave differently in fresh- and salt-water. Finding methods that will enable us to study their behaviour is essential,” says the environmental chemist. “We can add a fluorescent marker to the particles. When we test the sample in a spectroscopic camera, the marker will light up and distinguish such particles from other particles.”

“The big question now is to find out how high concentrations we need to test in order to be on the safe side. It is not worth taking chances with nature,” concludes Andy Booth.

Christina Benjaminsen Winge has been a regular contributor to the science magazine Gemini for 11 years. She was educated at Volda University College and the Norwegian University of Science and Technology, where she studied media and journalism.

Posted by Christina B. Winge and Åse Dragland

Åse Dragland is the editor of GEMINI magazine, and has been a science journalist for 20 years. She was educated at the University in Tromsø and Trondheim, where she studied Nordic literature, pedagocics and social science.