It’s a timely question. As smoke poured from the Buncefield oil depot fire recently there were dire predictions about the health effects it might have, an issue that investigators are addressing. Of the many potentially toxic constituents of the huge grey cloud, nanoparticles were singled out for special concern. What if they were to enter our bodies? Yet a new report by the European Science Foundation has also emphasised the extraordinary potential of nanomedicine — the use of nanoparticles to treat disease. It has left most of us confused. Should we be worried about nanoparticles or excited? For a start, using the word “particle” isn’t helpful, says Ken Donaldson, a professor of respiratory toxicology at the University of Edinburgh. “It’s a bit like using the word drink when the drink might be milk or whisky.”

Take three examples: a nanoparticle could be a bit of carbon in the exhaust gases of a lorry, but it might also be an antibody, which helps your body to fight infection, or an allergen that makes you sneeze.

What is nanomedicine?

Nano is the science of the teeny-tiny. The word comes from the Greek word nanos, meaning dwarf, and the so-called nanoscale covers things that are between 1 and 100 nanometres in size. A nanometre (nm) is a billionth of metre. By comparison, a human hair is 80,000nm wide, DNA is about 2nm wide, whereas individual atoms are less than a nanometre. “A nanoparticle to your body is on the same scale as a tennis ball to the moon,” says Ruth Dunca,n of the University of Cardiff.

Each of the trillions of cells in your body is a processing plant, turning out nanosize particles. Medicine already exploits these. For instance, Herceptin, the breast cancer drug, is a nanosized antibody that has an exquisite ability to latch on to the HER2 receptors of tumour cells and stop them receiving the signals that tell them to grow.

Benefits

The term nanomedicine tends to be reserved for nano-conglomerates, clusters of particles that incorporate a medicine and a tiny detecting unit designed to seek out a specific target; or a cluster that includes a particle with a carrying unit and a treatment bit. This has meant that potent drugs normally too toxic for human beings can be used to treat cancers because they can be targeted so specifically. The first nanomedicine of this sort was the anti-leukaemia drug Mylotarg. Many more are either on the market or completing clinical trials.

Miniature drug-delivery systems that have been developed include: “stealth liposomes”, which are nano-sized fatty balls; many- branched devices that look like tumbleweeds (more properly called dendrimers); and “buckyballs”, a hollow spherical form of carbon (see picture right) that can be filled with a medicine. Buckyballs are also being considered as agents to deliver materials to organs that will make them show up more sharply in MRI scans.

There are two other burgeoning areas of nanomedicine. One is diagnostics. It is now possible to measure the workings of hundreds of genes at the same time on a tiny chip. And, on a more homely level, for your GP to use a low- cost “lab on a strip” to do several tests at the same time on the same spot of blood, which would normally involve sending many samples off to a laboratory.

The other area is in tissue engineering, where nanomaterials are being developed for reconstruction after trauma or illness. What there won’t be is nanobots patrolling your bloodstream, but there are plans — the field is called theranostics, a combination of therapeutics and diagnostics — for nanosized bio-responsive systems which can diagnose and then deliver drugs or prompt tissue repair.

Possible risks

This all sounds marvellous, so where’s the health problem? Potentially, there are several. The first is the very nature of nanoparticles. Even in the Middle Ages, it was known that size mattered. Depending on how fine the gold particles used in glass-making, the glass was either blue, red or gold. As the medieval glassmakers demonstrated so conclusively, the usual chemical and physical properties of elements can change completely with particle size, especially in the nanoscale, which means that what’s already known about the effects of an element on the body may not hold true when it is present in tiny particles.

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