Questions and answers

Tomorrow I am going to Birmingham to take part in a citizens’ jury on the use of nanotechnology in consumer products, run by the consumer organisation Which? They are running a feature on nanotechnology in consumer products in the New Year, and in advance of this they asked me, and a number of other people, a number of questions. Here are my answers.

How are nanomaterials created?

A wide variety of ways. A key distinction to make is between engineered nanoparticles and self-assembled nanostructures. Engineered nanoparticles are hard, covalently bonded clusters of atoms which, fundamentally, can be made in two ways. You can break down bigger particles by milling them, or you can make the particles by a chemical reaction which precipitates them, either from solution or from a vapour (a bit like making smoke with very fine particles). Examples of engineered nanoparticles are the nanoscale titanium dioxide particles used for some sunscreens, and the fullerenes, forms of carbon nanoparticles that can be thought of as well-bred soot. Because nanoparticles have such a huge surface area relative to their mass, it’s often very important to control the properties of their surfaces (if for no other reason than that most nanoparticles have a very strong tendency to want to stick together, thus stopping being nanoparticles and losing the properties you were presumably interested in them having in the first place). So, it would be very common to make the nanoparticle with an outer coating of molecules that might make it less chemically reactive.

Self-assembly, on the other hand, is a process by which rather soft and mutable nano-structures are formed by particular types of molecules sticking together in small clusters. The classic example of this is soap. Soap molecules have a tail that is repelled from water, and a head that is soluble in water. In a dilute solution in water they make the best of these conflicting tendencies by arranging themselves in clusters of maybe 50 or so molecules, with the headgroups on the outside and the tails shielded from the water in the middle. These nanoparticles are called micelles. Biology relies extensively on self-assembly to construct the nanostructures that all living organisms are made of, including ourselves. For this reason, most food is naturally nanostructured. For example, in milk protein molecules called caseins form self-assembled nanoparticles, and traditional operations like cheese-making involve making these nanoparticles stick together to make something more solid. Of course, we don’t call cooking nanotechnology, because we don’t intentionally manipulate the nanostructure of the foods, even if this is what happens without us knowing about it, but, armed with modern techniques for studying the nanoscale structure of matter, people are increasingly seeking to make artificial nanostructures for applications in food and health. An example of an artificial self-assembled nanostructure that’s becoming important in medicine is the liposome (small ones are sometimes called nanosomes) – here one has soap-like molecules that arrange themselves into sheets exactly two molecules thick (a common material would be the phospholipid lecithin, obtained from soya beans, that is currently widely used as a food emulsifier, for example being an important ingredient of chocolate. If one can arrange the sheet to fold round onto itself you get a micro- or nano- scale bag that you can fill with molecules that you want to protect from the environment (or vice versa).

Can you tell us about the existing and expected applications of developments in nanotechnology in the areas of food and health (including medical applications)?

In food applications, the line separating conventional food processing to change the structure and properties of food and nanotechnology is rather blurred. For example, it was reported that an ice cream company was using nanotechnology to make low fat ice cream; this probably involved a manipulation of the size of the natural fat particles in the ice cream. This really isn’t very different from conventional food processing, the only difference being that modern instrumentation makes it possible for the food scientists involved to see what they are doing to the nanoscale structure. This sort of activity will, I’m sure, increase in the future, driven largely by the perceived market demand for more satisfying low fat food.

One area that is very important in health, and may become important in food, is the idea of wrapping up and delivering particular types of molecules. In medicine, some drugs, particularly the anti-cancer drugs used in chemotherapy, are actually quite toxic and lead to serious side-effects. If the molecules could be wrapped up and only released at the point at which they were needed – the tumour, in the case of an anticancer drug, then the side effects would be much reduced and the drug would be much more effective. This is beginning to happen, with drugs being wrapped up in liposomes for delivery. Another way in which nanotechnology can help in medicine is for drugs which can’t easily be dissolved, and thus can’t be easily introduced into the body. These can be prepared as nanoparticles, in which form the molecules can be absorbed by the body (a new anti-breast-cancer drug – Abraxane – is in this category). In food, in the future additives which are believed to be good for the health (so-called nutriceuticals) may be added to food in this way.

Other applications in health are in fast diagnostic tests. The idea here is that, instead of a GP having to send off a patient’s blood sample for a test to detect certain bacteria or biochemical abnormalities, and having to wait a week or so for the result to come back, nanotechnology would make possible a simple and reliable test that could be done on the spot. Looking further ahead, it’s possible to imagine a device that automatically tested for some abnormality, and then if it detected it automatically released a drug to correct it (for example, a diabetic might have a device implanted under their skin that automatically tested blood sugar levels and released the right amount of insulin in response).

Another area that is in tissue engineering – the growing of artificial tissues and organs to replace those damaged by disease or injury. Here it’s important to have a “scaffold” on which to grow human cells (ideally the patient’s own cells) in a way that they make a working organ. Currently growing replacement skin for burn victims is an a fairly advanced state of development.

Are manufacturers required to disclose the presence of nanomaterials on their labelling?

Currently, no.

What are the risks or concerns about using manufactured nanomaterials in health or food products?

There are concerns that some engineered nanoparticles might be more toxic than the same chemical material present in larger particles, both because the increased surface area might make them more reactive, and because they might be able to penetrate into tissues and cells more easily than larger particles.

Are some nanomaterials more risky than others?

This is very likely. Engineered nanoparticles, made from covalently bonded inorganic materials, seem the most likely to cause concern, but even among these it is important to consider each type of nanoparticle individually. Moreover, it may well be that the dangers posed by nanoparticles might be altered by the surface coatings they are given.

Are some applications of nanotechnology more risky than others?

Yes. In my opinion the biggest risk is in the use of engineered nanoparticles in situations in which they could be ingested or breathed in. The control of naturally occurring nanostructure in foods, the use of self-assembled objects like liposomes, and the kind of nanotechnology that is likely to be used in diagnostic devices, should present few if any risks.

In your opinion, should consumers be concerned about the use of manufactured nanomaterials in health or food products?

Somewhat, but not very. The key dangers come from the potential use of engineered nanoparticles without adequate information about their toxicity. In principle food additive regulations don’t generally discriminate by size. For example, a material like titanium dioxide, that is a permitted food additive (E171), could be used in a nanoscale form without additional testing. In principle it is possible to specify permitted size ranges for particles – this is done for microcrystalline cellulose – so this measure should be extended to other materials that could be used in the form of engineered nanoparticles on the basis of testing that discriminates between particles of different sizes.

If any, what protections need to be put in place?

The government should act on the recommendations of the March 2007 report by the Council of Science and Technology