Nanotechnology: the Science of the Very Small

A Nanoscience and nanotechnology have become very fashionable in recent times. Their prominence has inspired science fiction and raised a lot of hope and hype about the possibilities. But what exactly is nanotechnology? Most definitions agree that it is the manufacture of structures that measure up to 100 nanometres (nm). The diameter of an atom is typically 0.1 or two or three tenths of a nanometre while that of the human hair is around 1,000,000 nm. Essentially, we are now able to make new structures from atoms and molecules as if we were using the bricks of a children’s construction toy.

B Most of the electronic consumer goods that we use today contain components that measure less than 100 nm. The lasers in our CD and DVD players make use of the properties of semiconductor layers that are just a few atoms in thickness, so we clearly are in the nanotechnology age. There are many other everyday items that we take for granted that have nanoparticles in them. One of these is sunscreen. In the 1990s there were safety issues with many of the sunscreen products available, so scientists at Oxford University set about finding a solution. The product they developed uses nanoparticles of titanium dioxide that are doped with the element manganese. This reduces the hazard of potentially skin-damaging agents known as free radicals. The product is almost transparent to the eye when spread on the skin, and it is effective for much longer than many of the traditional preparations. In this case, we see an example of nanotechnology providing a solution to an existing problem rather than opening up new product areas.

C The technique of using nanotechnology to adapt existing products can also be applied to garments, upholstery, paint and plastics, to improve their longevity. Bearing this in mind, it is interesting to ask whether nanotechnology can help with some of the world’s major current issues. The recent growth in climate change awareness calls a range of things into question. Can we use energy more effectively? Can we reduce the carbon dioxide in the atmosphere? Can we use and purify water more effectively? Can healthcare be improved? Nanotechnology may very well provide the solutions. There are few times in history when the application of science to improving the human condition has been so apparent.

D We are already making new types of solar cells and batteries by using our newfound ability to manipulate matter at the atomic and molecular scale. If we can capture some of the huge quantities of energy that arrive at the Earth’s surface from the Sun, and store it effectively, we can reduce the need for fossil fuel-based power stations.We are already using nanoparticles and nanoporous materials to capture harmful greenhouse gases, and we may possibly convert some of them back into fuel. There are, however, many technical problems involved, and it will be another decade or so before some of these ideas are deployed. Water purification is increasingly challenging and many believe that water, which we take for granted, is going to become more valuable than oil. Currently we do not use water efficiently, and many industrial and food processes leave contamination in water that is potentially toxic and difficult to remove. Nanofiltration may provide the solution to these problems, and may also offer new routes to the desalination of brackish water and groundwater in some parts of the world.

E Water purification is increasingly challenging and many believe that water, which we take for granted, is going to become more valuable than oil. Currently we do not use water efficiently, and many industrial and food processes leave contamination in water that is potentially toxic and difficult to remove. Nanofiltration may provide the solution to these problems, and may also offer new routes to the desalination of brackish water and groundwater in some parts of the world.

F Food production and processing are becoming more important as the world’s population increases. There are concerns that potentially harmful nano-products might enter the body via the gut. Such concerns are being addressed, but it is even more important to ask questions about how nanotechnology might increase the nutritious yield of food and be adapted to help preserve and package food. There is already evidence to show that it can also be helpful in the primary production of raw food materials, by way of better delivery of pesticides to the field and better extraction of protein and carbohydrates.

G Healthcare is an area where the application of nanotechnology is already exceeding the expectations of ten years ago. It is happening across several fronts: better appreciation of what the ‘natural’ nanoparticles circulating in body fluid do; better methods of delivering drugs to the body via nanoparticles that target the diseased body part; improvements to the diagnostic imaging techniques of ultrasound, magnetic resonance imaging and X-ray computerised tomography. We are now at the threshold of a new subject, ‘theranostics’, whereby nanoparticles will first deliver the diagnostic information to the clinician and then, using the same particle, deliver a form of therapy.

H Nanotechnology is a life-changing technology, making the quality of life better, enabling us to make use of our resources more effectively, thereby protecting our environment, and creating new business opportunities. There are many other examples in the world of ‘new materials’ that also make use of nanotechnology. The possibilities may well be limitless.

The Tuatara -- Past and Future

The New Zealand species of lizard, the tuatara, is firmly embedded in the national psyche: an icon for today which dates from the age of dinosaurs; an ancient reptile commemorated on the back of the five cent coin. New Zealanders feel an affinity with the tuatara, and accept that active conservation management is required to ensure it will be among the legacies left to future generations.

When European explorers reached New Zealand in 1769 they found two large islands, which together they called the ‘mainland’, and many tiny offshore islands around the coast. The naturalists who came with the explorers disregarded the tuatara, though it is improbable none were seen. Only several decades later did a tuatara specimen reach the British Museum, where it was eventually classified as just another type of lizard.

One of the first scientists who realized that aspects of tuatara anatomy were odd -- unchanged for tens of thousands of years -- was Albert Gunther in 1876. Gunther believed the tuatara was one of the most valuable objects in zoological anatomical collections, and also noted, in passing, the reptile was likely to become extinct. From today’s perspective, it is striking that Gunther expressed no concern about the probable demise of the tuatara. He and his contemporaries were products of their age, strongly influenced by Charles Darwin’s theory, which had only recently been published. Their views were something like this: "Extinction is a natural process. It is sad that species disappear, but that is part of nature."

There is a second important aspect of Gunther’s work. He recorded, correctly, that some of the mammals introduced by Europeans were predators of the tuatara -- particularly rats. But what he did not realize was that New Zealand has two species of rat, both introduced, both with an appetite for tuatara: the ship’s rat came with European explorers and settlers; but the kiore rat had already been in the country for hundreds of years, brought by Polynesians from the Pacific Islands. Gunther failed to recognise the distinction, believing all rats to be a relatively recent introduction.

Little further research was conducted until Ian Crook of the NZ Wildlife Service published his findings in 1973, which can be summarised as follows. Tuatara thrive on offshore islands with no rats. Tuatara never survived on islands with ship’s rats. On a few islands, small and declining populations of tuatara occur with the kiore. This should not be seen, however, as evidence that tuatara and kiore can coexist. Rather, Crook proposed, kiore probably only arrived recently on such islands, and thus the small populations represent extinctions in progress.

Throughout the 1990s, Richard Holdaway and his colleagues at Victoria University in Wellington documented the surprising discovery that kiore probably arrived about 1800 years ago, although the human population of New Zealand is thought to be no older than 800 years. How is this possible? Presumably, Holdaway argued, the kiore were brought by Polynesian explorers who visited the country but did not settle. Thereafter, the rats were agents of ecological warfare, exterminating perhaps 1000-- 3000 species. Thus, tuatara and many other species were already rare or extinct when permanent human inhabitants -- the Maori -- arrived around 1300. This hypothesis is still being debated, but the evidence continues to accumulate in its favour.

Conservation practice has changed dramatically since Crook’s findings were published in 1973. Eradication of rats from any given environment was believed to be virtually impossible until about 1980, but since then has become routine. Enormous conservation benefits are accruing as newly rat-free offshore islands are providing sanctuaries for the country’s rarest species. In 1995, for example, Nicola Nelson of the Department of Conservation established 68 tuatara on Titi Island. Since then, four more populations of tuatara have been established elsewhere under similar conditions. Today, numbers of tuatara are still a fraction of what they once were, but for the first time in 1800 years the decline has been reversed.

While the recovery of rare species is itself a good thing, the truly significant outcome of this research is that it liberates the imagination. If we can remove predatory introduced mammals from islands, why not from the mainland too? Perhaps the questions we ask should demonstrate even more visionary ambition. Can non- mammalian pests also be removed from the mainland? Our rivers, for example, are full of surrogate rats, in the form of introduced species of fish called trout. Some day more people will understand that trout have replaced a whole native fauna in our waterways, just as rats replaced tuatara on the mainland. Will such knowledge lead to the creation of mainland ‘aquatic islands’ where we can once again establish those species of indigenous fish that used to live in our rivers? Similarly, can bellbirds and tuis replace birds like starlings and mynahs?

The answers to such questions are uncertain, and opposing sides will doubtless be fiercely debated. But the role of scientific knowledge in illuminating the past will be crucial. Just as we now no longer tolerate extinction, in the future we may no longer accept a mainland devoid of the biological wonders of our past such as tuatara. Conservation is thus not primarily about the past but about imagining and then creating the future we wish for our children and ourselves. For 80 million years until humans arrived, tuatara occurred throughout New Zealand -- might they do so again?