Biomedical Engineering Reference
In-Depth Information
CN T ( C TAB )
CN T (Tr i t o n X - 100 )
CN T (S D S)
O
O
O
NO
NO
NO
O
S
C
O
S
C
O
S
O
O
O
O
OH
OH
OH
FIGURE 15.13 Schematics of electrostatic interactions between surfactants adsorbed on CNTs and
negatively charged DNA molecules.
between surfactants and DNA (Fig. 15.13). The effective adsorption of DNA on the
CNT/CTAB surface is an important factor that contributes to the facile electron trans-
fer of DNA at the CNT/CTAB-modifi ed electrode.
CNT-coated electrodes can be constructed easily as long as stable CNT suspensions
are obtained. However, one needs to choose a suitable surfactant dispersant for the fab-
rication of CNT/surfactant-modifi ed electrodes with high catalytic and good selectivity
toward the analytes.
15.3.2 Improving the electroanalytical sensitivity and selectivity for
small biological and pharmic molecules with carbon nanotubes
The determination of some important analytes, especially small biological and pharmic
molecules, at CNT-modifi ed electrodes has been extensively investigated. In particu-
lar, neurotransmitters such as dopamine, epinephrine, and norepinephrine, which are
important species in the mammalian central nervous systems, have received much
interest. However, the electroanalysis of neurotransmitters on the conventional elec-
trodes has suffered from the presence of a high concentration of ascorbic acid present
in mammalian nerve and brain tissues, because neurotransmitters and the interferents
such as ascorbic acid are usually oxidized at the potentials that are close to each other.
Wang et al. have reported that a CNT-modifi ed gold electrode has favorable electro-
catalytic activity toward dopamine and norepinephrine. The electrochemical response
of norepinephrine, uric acid, and ascorbic acid can be separated on this modifi ed
electrode [74]. The selective determination of dopamine in the presence of ascorbic
acid has been studied at CNT coated and intercalated electrodes [75], CNT/Nafi on
coated GC electrodes [76], CNT-modifi ed gold electrodes [77], single carbon fi ber
microelectrodes modifi ed with CNTs and Nafi on [78], layer-by-layer assembled CNTs
[79], DNA-functionalized CNTs [80], and water-soluble CNTs prepared via non-
covalent functionalization by Congo red through a physical grinding treatment [81].
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