Smart Nanotubes for Biotechnology and Biocatalysis
Read full article onlineFull Article
Nanoscience is one of the most important research and development frontiers in modern science. Nano is a Greek word meaning dwarf, and the nanometer (nm, 10− 9 m) defines the length scale that is used to measure systems being studied in nanoscience. In the most simplistic sense, nanoscience is the science of small particles of materials. Such small particles are of interest from a fundamental viewpoint because all properties of a material (e.g., melting point, electronic properties, and optical properties) change when the size of the particles that make up the material becomes nanoscopic. With new properties comes new opportunities for technological and commercial development, and the applications of nanoparticles have been demonstrated or proposed in areas as diverse as microelectronics, coatings and paints, and biotechnology.
For example, one application that is currently in the commercial marketplace entails using gold nanoparticles as visual indicators in over-the-counter medical diagnostic kits. This application illustrates nicely how the unique properties of a nanoparticle can lead to technological opportunities. Macroscopic samples of pure gold have only one color—gold—but nanoparticles of gold can show essentially all the colors of the rainbow, depending on the size and the shape of the nanoparticle. Furthermore, the intensity of the optical absorption of gold nanoparticles is extraordinarily strong, which means that when suspended in a solution or deposited on a surface, the naked eye can detect a very small quantity of these particles. These properties make gold nanoparticles ideally suited as visual indicators.
Other applications of microparticles and nanoparticles in the biomedical sciences and biotechnology include the use as vehicles for enzyme encapsulation, DNA transfection, biosensors, and drug delivery. For example, drugs can be incorporated into nanospheres composed of a biodegradable polymer, and this allows for timed release of the drug as the nanospheres degrade. The circumstances that cause the particle to degrade can be adjusted by varying the nature of the chemical bonding within the particle. For example, when acid-labile bonds are used, the particles degrade in acidic microenvironments such as would-be extant in tumor cells or around a site of inflammation. This allows for site-specific drug delivery. In another recent study, polymeric nanoparticles were labeled on their outer surfaces with a viral peptide sequence that promotes permeation of substances through cell membranes. These peptide-derivatized nanoparticles passed through cell membranes, and got incorporated into living cells, at much higher levels than nanoparticles without the surface-bound peptide.