Nanomedicine, Volume I: Basic Capabilities
© 1999 Robert A. Freitas Jr. All Rights Reserved.
Robert A. Freitas Jr., Nanomedicine, Volume I: Basic Capabilities, Landes Bioscience, Georgetown, TX, 1999
1.1 A Noble Enterprise
The history of disease is vastly older than that of humankind itself. Indeed, disease and parasitism have been inseparable companions to life since the dawn of life on Earth. Fossilized bacteria similar to those responsible for many infections that afflict people today have been found in geological formations that are 500 million years old. Fossil shells dating from an era almost equally remote show clear evidence of disturbance by injury and parasites. Examination of the skeletons of long-extinct dinosaurs and other great reptiles show that these creatures suffered from fractures, bone tumors, arthritis, osteomyelitis, dental caries and other diseases that still plague us in the 20th century. While available fossil evidence is largely limited to changes observable in bones and teeth, it is probably safe to assume that disease processes were equally prevalent in the soft organs and tissues that have not been geologically preserved, and that the general pattern of disease has not changed in its essentials during the hundreds of millions of years that animal life has existed on this planet.2158
Since its first appearance on the prehistoric stage millions of years ago, the human body has also been constantly subject to assault and injury, invasion by parasites, extremes of heat and cold, and infections. Early man probably suffered from a number of diseases due to nutritional factors and body chemistry disorders. For example, the poor condition of the teeth of an 18-year old Australopithecus who lived 1.75 million years ago, found at Olduvai Gorge by Louis Leakey2187,2188 in 1959, suggests that the hominid had a disease that lasted for many months -- most likely gastro-enteritis due to malnutrition -- with three major attacks of the disease at the ages of two, four, and four and a half.2186 Diseases that may date back more than 25 million years to the ape ancestors of modern apes and man2190,2191 are amoebic dysentery, malaria,2189 pinworm infections, syphilis, yaws,2199 and yellow fever. Diseases which may have appeared and evolved with man2198 include leprosy and typhoid; certain modern diseases such as cholera, measles,2196,2197 mumps, smallpox, whooping cough, and the common cold require large concentrated populations to support them, thus probably could not have existed in the prehistoric era.2186,2191-2195
As for cancer, Java man, first discovered by Dutch anatomist Eugene Dubois in 1891 and considered to be half a million years old, had a morbid growth on his femur. It is likely that bone cancer and other forms of cancer have existed from the earliest times. The remains of Neanderthal, a competing species to Homo sapiens that roamed through Europe, Africa, and the Near East during the last glacial period ~75,000 years ago, show clear evidence of arthritis, tooth loss, and suppurative bone disease. (The high rate of broken bones and early death suggests that Neanderthals engaged in more close-quarter combat with large animals than did modern humans, who had figured out safer strategies.2329) Human bones unearthed from the New Stone Age period reveal that Neolithic man suffered from arthritis, congenital dislocations and fractures, sinusitis, tuberculosis of the spine, and tumors.2158
In considering the question of how our earliest ancestors dealt with these conditions, we are on somewhat uncertain ground, since little direct evidence has been preserved. Anthropologists point out that in pre-Neanderthal hunter-gatherer tribes, a sick or lame person is a serious handicap to a group on the move. In the event of major illness or mortal wounds, sufferers may either leave the group, be abandoned, or, as with lepers in medieval Europe, may be ritually expelled, becoming "culturally dead" before they are biologically dead. Early hunter-gatherer hominid bands were more likely to abandon their seriously sick than to succor them,2204 although Cro-Magnons and Neanderthals evidently were the first to care for their wounded and disabled, and to bury their dead.2341-2343
But moderate wounds, bruises, fractures, or foreign bodies such as arrowheads or thorns are tangible things that demand attention. Thus the art of surgery must first have originated as a response to immediate crises. The first and most obvious course of action of a wounded man would be to protect the site of injury from the influence of external forces or agents. For this there was, and remains to this day, only one means -- the application of a dressing. Many observations were made and many substances tried, and in time a body of experience was accumulated and passed on orally to others for use in similar emergencies, eventually creating a considerable sum of inherited empirical knowledge. It is believed that the art of dressing wounds long constituted the whole of medicine -- the use of internal remedies or herbs, and use of the knife or fire, came much later.2158
Present-day primitive and folk medicines provide additional clues to early medical practice. For example, many early peoples developed effective methods to control bleeding -- the use of cobwebs is an ancient folk remedy, as is the application of tourniquets, packing with absorbent materials, the laying on of snow or, at the other temperature extreme, the application of cautery by hot knife or spear.2158,2204 The Masai and Akamba tribes treated sword wounds by slapping on a poultice of cow dung and dust. The suturing of wounds is practiced by some primitive peoples and may have been known to prehistoric man. Bone needles furnished with an eye have been found in paleolithic deposits in France and England, and some Indian tribes suture with threads of sinew or bone needles (the needles are left in and the thread is twisted around them). One of the strangest suturing techniques, observed among primitive tribal cultures in such widely separated places as India, East Africa and Brazil, is the sealing of wounds, especially abdominal wounds, using termites or ants. The edges of the wound are drawn closely together and the insect is allowed to bite through them both, firmly securing the flesh on two sides. Once attached, the insect's body is severed, allowing only the jaws to remain in place, holding the wound shut.2158
While able to deal with wounds, early man did not admit the existence of disease from "natural causes". Internal diseases were generally ascribed to malevolent influences exercised by a supernatural entity or a human enemy. As centuries passed, many internal diseases were eventually recognized and simple treatments empirically established -- for example, Celsus (ca. 30 AD), a Roman medical writer, described ligature (tying off blood vessels), suturing the large intestine, eye operations such as couching for cataract, tonsillectomy, and bladder surgery to remove stones.2200 But the rational basis for internal medicine awaited basic physiological knowledge such as the circulation of the blood, finally proven by William Harvey (1578-1657) in 1628, and the discovery and acceptance of the theory of infection by microorganisms in the 1800s. Throughout most of human history, life has been short indeed -- Table 1.1 shows the average age of death for a sampling of persons buried in Roman times. (Some variation may represent regional differences in burial practices.) Even by the 17th century, more than half of all children never lived past the age of ten, often succumbing to diseases such as cholera, diphtheria, scarlet fever, or whooping cough, or being scarred for life by smallpox. It was a common and widely accepted fact of life that people would die at all ages, although wealthy families could leave town every year during the cholera season.1724
One of the constant missions of human civilization has been the avoidance and elimination of animals that prey on humans. Cave-dwelling carnivorous saber-toothed tigers, having occupied the upper echelons of the food chain for 30-35 million years, finally became extinct not more than about ten thousand years ago, most likely at the hands of newly-arrived human hunters crossing the Siberian land bridge into post-Pleistocene North America.2186 As late as medieval times, wolves ranged freely over Europe, remaining abundant in France through 1500 AD -- in winter, audacious wolf packs would enter Paris and eat children, dogs, and even adults who were alone on the streets.1724 With technological advances, extant tiger and wolf species are now largely confined to artificial habitats or isolated nature preserves and no longer pose any serious threat to human health. People in most places are not eaten by wolves; indeed today, a few venturesome individuals actually keep and breed wolves with dogs, as pets.
Bacteria are among the last remaining "wild animals" on Earth that threaten man. As our instrumentalities continue to progress from the macroscale to the microscale, and finally to the molecular or nanoscale, all of the remaining natural "wild things" that endanger human life and health -- whether viruses, bacteria, protozoa, metazoan parasites,3253,3254 or even our own pathological native cells -- will be confined and tamed, reconstructed or eliminated. Using smaller tools, we hunt smaller prey. As with sabertooths in the post-Neolithic era, and with wolves in post-medieval times, people of the 21st century will no longer fear or need suffer predation by wild microbes or tumor cells run amok.
Humanity is poised at the brink of completion of one of its greatest and most noble enterprises. Early in the 21st century, our growing abilities to swiftly repair most traumatic physical injuries, eliminate pathogens, and alleviate suffering using molecular tools will begin to coalesce in a new medical paradigm called nanomedicine. Nanomedicine may be broadly defined as the comprehensive monitoring, control, construction, repair, defense, and improvement of all human biological systems, working from the molecular level, using engineered nanodevices and nanostructures.
In this book we shall explore in preliminary fashion a few of the technical details, specific requirements, and physical limitations of these engineered nanodevices, and the meaning of nanomedicine within the context of the traditional healing arts. Since at this writing these nanodevices cannot yet be built, our subject matter is of necessity somewhat speculative, albeit thoroughly grounded in the best scientific and engineering knowledge currently available. Medical philosopher Edmond A. Murphy notes that "to the physician, the more remote the area of speculation from the welfare of the patient, the more clearly [this speculation] must be shown to give promise of ultimate benefit".2228 The author believes that nanomedicine clearly meets, indeed vastly exceeds, this stringent requirement for relevance and utility.
After the manner of many contemporary medical school programs, the present trilogy progresses from a general emphasis on basic science and engineering capabilities in Volume I, to nanomedical tools and systems in Volume II, leading finally to a sharp focus on clinical nanomedicine in Volume III.
Last updated on 5 February 2003