Nanomedicine - Bionanoelectronics: Bioinquiring and Bioinspired Devices - page 137

Fig. 4.14 The remote
dehybridization of DNA via a
wireless microwave field

Au

RF field

FAM

FAM

covalently linked at one end to a gold nanoparticle antenna. The dehybridization
was monitored by the hyperchromicity of DNA at 260 nm, measured by optical
absorbance. Alternatively, the controlled dehybridization process induced by the
effective temperature rise due to the RF electromagnetic field can be observed
by measuring the fluorescence signal emitted by a fluorophore FAM linked to
the other end of the DNA molecule. When the latter dehybridizes, FAM diffuses
into the supernatant and the fluorescence signal of the supernatant increases
accordingly. A simplified antenna-induced dehybridization process is displayed in
Fig. 4.14 . This controlled dehybridization process could be used to manipulate the
reversible production of specific RNA molecules. This could be possible because the
dehybridization is selective, i.e., the biological molecules or parts of them which are
not labeled with gold nanoparticles remain unchanged.
Optical antennas ( Bharadwaj et al. 2009 ) are equally important for the wireless
control of drug delivery biochips. For example, dielectrophoretically assembled
core-shell CNT structures in the form of aligned filaments exchange excitation
energy between the shell and the core. These core-shell structures consist of annular
shells of (6,5) single-walled CNTs with a bandgap of E g D 1:21 eV and (7,5) and
(8,7) single-walled CNT cores, with smaller bandgaps than the shells. The excitation
energy is spatially concentrated in the center of the core-shell structures, which
have a radial gradient of the bandgap ( Han et al. 2010 ). A strong photoemission in
the near infrared spectral region is observed in the (8,7) nanotubes as a result of
this excitation energy exchange. The photoemission of the CNTs with the smallest
bandgap is generated by illumination in a broad spectral range, which extends from
near infrared to ultraviolet. Such a miniature antenna is displayed in Fig. 4.15 .The
tip of the antenna contains only shell CNTs.
The drug delivery method based on chips is also applicable in the brain, via
electronic device interfaced with neurons. A drug delivery chip able to release
locally a neurotransmitter molecule ( L -glutamate) and to stimulate individual neu-
rons is described below ( Mernier et al. 2007 ). The neurotransmitter is filled in by a
minireservoir fabricated, or release region, via Si MEMS technologies and delivered