Biomedical Engineering Reference
In-Depth Information
such as hexane was also confirmed. This is important for the automation and
economization of the dioxin removal treatment.
In addition [103, 104], a new type of composite that combines DNA with
silica components via a sol-gel method was described. The DNA-silica hybrid
material is advantageous with respect to its mechanical and chemical stabil-
ity in both aqueous and organic solvents. Similar to the previously described
hybrids, the specific functions of the DNA molecules were retained and main-
tained: the DNA-silica hybrid materials adsorb DNA-interactive chemicals
from diluted aqueous solution. In another series of reports [105-109], DNA-
loaded PSf microspheres were fabricated by means of a liquid-liquid phase
separation technique. The release rate of DNA from the microspheres can be
controlled by manipulating the microsphere structure. Increasing the poly-
mer concentration causes lower porosity and smaller pores on the outer
surface of the microspheres, and leads to a low release rate of DNA from
the microspheres. The DNA-loaded PSf microspheres could effectively accu-
mulate harmful DNA-intercalating pollutants and endocrine disruptors, as
described in previous reports.
Beside these environmental applications, the intercalation of planar chem-
icals has been utilized to immobilize DNA. Shimomura et al. succeeded in
immobilizing DNA on a Langmuir-Blodgett monolayer using an amphiphilic
intercalator, octadecyl acridine orange, at the air-water interface [110]. In
a following work, Nakamura and coworkers reported a protocol on the immo-
bilization of DNA molecules onto monolayers containing anthryl groups [111].
Maeda et al. used vinyl derivatives of DNA intercalator to immobilize dsDNA
in hydrogels [112, 113]. Recently, Kelley et al. [114] described a DNA-surface
immobilization achieved through an ethidium derivative linker on the film sur-
face. The highly conjugated linkage resulted in more efficient electron transfer
relative to systems utilizing conventional insulating tethers. The DNA linkers
applied in these studies have a similar character, a linear molecule terminated
by intercalator and a functional group with high affinity to the solid.
DNA is polymorphic and exists in a variety of distinct conformations. Du-
plex DNA can adopt a variety of sequence-dependent secondary structures
that range from the canonical right-handed B-form through the left-handed Z
conformation. Consequently, using DNA as a template for synthesis of supra-
molecular polymers may give multifarious helical materials. A descriptive
example of this approach was published by Armitage et al. [115]. They used
an assemblage of symmetrical cationic cyanine dyes bound in the minor
groove to produce a helical supramolecular structure.
DNA is chiral by virtue of the asymmetric centers in the ribose units and
as a result of the twist of the helix axis. Because of its inherent chirality, DNA
is an attractive scaffold for enantioselection, which is of crucial importance
in various fields such as drug and food analysis, biochemistry, or clinical
pharmacology. Chaires et al. [116] reported a dramatic experiment demon-
strating structural selectivity in DNA binding for the naturally occurring
