Biomedical Engineering Reference
In-Depth Information
(e)
(g)
2µm
(b)
(a)
(f)
Z(nm)
- 30
- 20
- 10
0
200
400
Distance (nm)
600
800
Z(nm)
- 8
- 4
0
200
400
Distance (nm)
600
800
(c)
(d)
Fig. 7.14. Example of electrical contacts assembled using the AFM as a manipulator. Left: carbon
nanotube manoeuvred to connect two gold electrodes. Right: nanoparticles assembled into a nano-
wire. Reprinted with permission from [522] and [527].
[270, 523, 524]. Many other types of nanostructures have also been manipulated in similar
ways, particularly various types of nanoparticles and nanorods [270, 498, 525-531]. In
addition, various biological nanostructures (e.g. DNA, chromosomes, etc.) have been
manipulated using AFM probes [532, 533]. It should be mentioned that advanced control
interfaces make the assembly of complicated devices more convenient, but nanomanipu-
lation is possible using any AFM.
Examples of structures that can be manufactured in this way include wires, transistors
[523] and electrical contacts. For example, small gold nanoparticles can be aligned into
particle chains by AFM pushing on a surface, and then used as seeds for further gold
deposition in order to form a fully connected gold nanowire [527]. Some images showing
the process and the resulting wire are shown in Figure 7.14.
7.2.4 Nanoparticle-DNA interactions
One of the most important areas of nanoscience is nanobioscience, which can be defined as
using a nanotechnological approach to solve biological problems. Within nanobioscience,
probably the most widely applied technology in the medical biosciences is that of
nanoparticles, which have been used and proposed for a variety of diagnostic [534],
imaging [535] and treatment strategies [536, 537]. One reason why nanoparticles have
achieved such broad application is that they approximate the sizes of viruses or even of
individual proteins, and thus may interact with the targets as would proteins and viruses.
These targets include biomolecules such as proteins and nucleic acids (RNA and DNA),
and such targets may be reached in vitro , but nanoparticles are also capable of entering
cells (as viruses may do) to find their targets [538]. Another reason why nanoparticles are
so useful for these sort of applications is that they can be engineered to have multiple
properties (such as optical, magnetic, targeting properties) in a facile way [538].
AFM is the ideal technique to observe directly the interaction of nanoparticles (which
are usually based on a metal or crystalline semiconductor) with their biomolecule targets;
 
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