Biomedical Engineering Reference
In-Depth Information
is more efficient than traditional antibiotics because it is extremely active in small quantities, as little
as one part per billion of silver may be effective in preventing cell growth.
21.4.4.9 Nanospheres
Nanospheres are hollow nanoscale structures made of polymers. These nanospheres can be loaded
with special molecules like anticancer drugs. Injectable nanospheres have important potential applica-
tions such as site-specific delivery and medical imaging.
21.5 CONTRIBUTION OF MICROBIOLOGY TO NANOTECHNOLOGY
Considering microbiology in general, nanoscience could be used both to understand and control proc-
esses at the molecular assembly level. Just as bacteria were the first models to understand genetics
and biochemistry that were later applied to eukaryotic systems, the same is true for the processes of
function, recognition, and assembly. Micro (Greek) meaning very small, usually smaller than 1 mm,
denotes 10 6 , so a micrometer is one millionth of a meter. Nano (Greek) dwarf—goes from small
to tiny; the word “nano” means 10 9 . So a nanometer is one billionth of a meter. If it is micro it is
almost nano; however, going down from the micro- to the nanoscale is not a simple matter of size
reduction. The transition between the “small” and the “tiny” involves a radical change in the scientific
concepts applicable. The laws of physics that govern the macroscopic world of our everyday experi-
ence can be readily used to understand microscopic objects. However, they break down completely in
the nanoworld because of the radically different length-scale hierarchies and the underlying quantum
mechanical behavior of individual atoms, electrons, or photons.
The term “microbiology” generally describes the study of those organisms invisible to the
human eye, in particular yeast, bacteria, and viruses. However, these three types of organisms are
significantly different from each other. Yeast and bacteria are different cell types (eukaryotic and
prokaryotic, respectively), whereas a virus is not strictly a living organism, being an obligate intracel-
lular parasite. The tools to conduct research in microbiology can be separated into two main fields—
microscopy, which is required for visualization, and molecular biology, which has been used to
characterize (in some cases comprehensively) the genetic and proteomic makeup of these organisms.
The initial steps in opening the field of microbiology came with the advent of the first microscopes.
Bacteria were first visualized by Antony van Leeuwenhoek, using a simple, self-built microscope,
around 1676. The microscopes built by Leeuwenhoek were not compound microscopes, relying
instead on a single lens, more like a very powerful magnifying glass. One of his first descriptions of
bacteria (referred to as animalcules) was from samples scraped from the teeth of van Leeuwenhoek
himself.
Advancements made in light microscopy by the combined work of Ernst Abbe and Carl Zeiss
in the 1880s further extended the research of the microbiological world. However, as Abbe himself
had described, there is a limit to the resolution of light microscopy, dependent on the wavelength
of the illuminating light and the numerical aperture of the lens. In reality, the resolution of light
microscopy is limited to half the wavelength of light, or around 250 nm. As such, the study of the
structure of viruses had to waft for the advent of the electron microscope in 1931 by Ernst Ruska
and the subsequent crystallization of the tobacco mosaic virus (TMV) in 1935 by Wendell Stanley
( Figure 21.8 ).
 
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