Technology Introduction to Nanotechnology and Its Applications to Medicine Gabriel A. Silva, M.Sc., Ph.D. Departments of Bioengineering and Ophthalmology, Whitaker Institute for Biomedical Engineering and Neurosciences Program, University of California, San Diego, LaJolla, California Silva GA. Introduction to nanotechnology and its applications to medicine. Surg Neurol 2004;61:216 –20. Nanotechnology can be defined as the science and engi- neering involved in the design, synthesis, characteriza- tion, and application of materials and devices whose smallest functional organization in at least one dimension is on the nanometer scale or one billionth of a meter. At these scales, consideration of individual molecules and interacting groups of molecules in relation to the bulk macroscopic properties of the material or device be- comes important, since it is control over the fundamental molecular structure that allows control over the macro- scopic chemical and physical properties. Applications to medicine and physiology imply materials and devices designed to interact with the body at subcellular (i.e., molecular) scales with a high degree of specificity. This can potentially translate into targeted cellular and tissue- specific clinical applications designed to achieve maximal therapeutic affects with minimal side effects. In this re- view the main scientific and technical aspects of nano- technology are introduced and some of its potential clin- ical applications are discussed. © 2004 Elsevier Inc. All rights reserved. N anotechnology and nanoengineering stand to produce significant scientific and technolog- ical advances in diverse fields including medicine and physiology. In a broad sense, they can be de- fined as the science and engineering involved in the design, syntheses, characterization, and applica- tion of materials and devices whose smallest func- tional organization in at least one dimension is on the nanometer scale, ranging from a few to several hundred nanometers. A nanometer is one billionth of a meter or three orders of magnitude smaller then a micron, roughly the size scale of a molecule itself (e.g., a DNA molecule is about 2.5 nm long while a sodium atom is about 0.2 nm). To give an appreciation of just how significant an order of mag- nitude is, let alone three orders when going from micron to nanometer scales, consider that no one would ever walk from New York to San Diego, but with a single order of magnitude change in speed (the equivalent of changing speed from walking to driving), you would get to San Diego across the United States in about 2 days. Flying, which would be two orders of magnitude faster than walking, would get you across the United States in a few hours and in a supersonic plane (or three orders faster than walking), it would take you minutes. (Walking a straight line between the two cities would take about 42 days at an average speed of 3 miles per hour.) The potential impact of nanotechnology stems directly from the spatial and temporal scales being considered: Materials and devices engineered at the nanometer scale imply controlled manipulation of individual constituent molecules and atoms in how they are arranged to form the bulk macro- scopic substrate. This, in turn, means that nano- engineered substrates can be designed to exhibit very specific and controlled bulk chemical and physical properties as a result of the control over their molecular synthesis and assembly. For applications to medicine and physiology, these materials and devices can be designed to interact with cells and tissues at a molecular (i.e., subcellular) level with a high degree of functional specificity, thus allowing a degree of integration between technology and biological systems not previously attainable. It should be appreciated that nanotechnology is not in itself a single emerg- ing scientific discipline but rather a meeting of traditional sciences such as chemistry, physics, materials science, and biology to bring together the required collective expertise needed to de- velop these novel technologies. In this review, the main synthetic and assembly approaches used in nanotechnology are intro- Address reprint requests to: Dr. Gabriel A. Silva, University of California, San Diego (UCSD), Jacobs Retina Center, 0946, Room 204, 9415 Campus Point Drive, La Jolla, CA 92093-0946. Received July 27, 2003; accepted September 24, 2003. 0090-3019/04/$–see front matter © 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.surneu.2003.09.036 360 Park Avenue South, New York, NY 10010 –1710