Biomedical Engineering Reference
In-Depth Information
demonstrate the promising feasibility of using the anionic DNA molecule to
create precisely ordered materials with various functions.
2.1
DNA and Inorganic Matters
In contrast to other familiar anionic polymers, the anionic dsDNA is distin-
guished by the double-helical conformation and the existence of the pairing
bases. These characteristics make the interaction between the DNA molecule
and various metal ions more complex. A recent investigation indicated that
the character of the DNA-metal ion complex strongly depends on the ion
type [2]. Al
3+
,Cr
3+
,Fe
2+
,Fe
3+
,Cu
2+
,Zn
2+
,Y
3+
,La
3+
,In
2+
,andCd
2+
metal
ions at 1 M concentration immediately form a water-insoluble gel from highly
concentrated solutions of DNA (10 mg
mL)viaaioncross-linking.Onthe
other hand, alkali earth metal ion solutions did not yield gels. The SEM
images taken from the surface of the DNA-ion complex suggest that the struc-
ture of the DNA-Al
3+
complex is more regular than the DNA-Cu
2+
complex
(Fig. 2). However, the results from CD and infrared spectra indicated that
Cu
2+
not only strongly binds to the phosphate group by electrostatic inter-
action but also changes the DNA base pairs, leading to destruction of the
B-DNA structure and to a decrease of flexibility of the DNA molecule.
Since current top-down lithography techniques faced a serious problem for
electronic technologies, interest in the bottom-up approach has risen sharply
in recent years. Among many candidate materials for the bottom-up strate-
gies, DNA attracted a lot of attention since it has a small diameter of about
2 nm, is flexible, and can be targeted uniquely at each end. One application for
DNA being explored is “nanowires” for interconnecting quantum dots with
each other and for linking them to macroscopic electrodes or other devices.
Since a DNA molecule in aqueous solution is usually randomly structured as
a result of thermal fluctuations, the individual DNA molecules must be sep-
arated and stretched prior to serving as templates for nanowire fabrication.
/
Fig. 2
SEMimagesofDNA-metalionfiberofDNA-Cu
2+
fiber and DNA-Al
3+
complex.
The structure of the DNA-Al
3+
complex is more regular than that of DNA-Cu
2+
complex
