Biomedical Engineering Reference
In-Depth Information
GOx
Antibody
Antigen
HN
HN
C=O
C=O
Source
Drain
FIGURE 13.5
Field-effect transistors for the detection of glucose (left) or antigen-antibody interaction (right).
the CNTFET. The CNTFET relied on the U1A antigen (a 33-KDa protein) covalently
attached to the detergent molecule, which was irreversibly adsorbed on the CNT walls.
The antigen-specific 10E3 mABs antibody was then bound to the antigen-functionalized
CNTs. The binding process was monitored by CNTFET electrical conductance measure-
ments as shown in Figure 13.5 (right). The binding of antibody to antigen-functionalized
CNTs resulted in a decrease in the conductance of CNTFET. The conductance measure-
ments of CNTFET device can analyze a specific response up to 1 nM of the 10E3 antibody,
whereas a much higher concentration of polyclonal IgG (1
M) was not detected. The
CNTFET device exhibited the electrical detection of the antibody-antigen interactions at a
100-fold higher sensitivity than the quartz-crystal microbalance measurements. The
decrease in the conductivity of the CNT resulting from the antigen-antibody binding in
CNTs is at present not fully understood theoretically.
Similarly, Boussaad et al. [51] reported on the in situ detection of a small number of pro-
tein adsorption onto individual SWCNT transistors based on the changes in the electron
transport properties of the CNTFET. The adsorption of cytochrome
c
onto CNTFET led to
a decrease in the conductance of SWCNT. The CNTFET device can detect as low as 20 of
cytochrome
c
molecules.
13.6
Conclusions and Future Perspectives
This chapter summarizes recent advances in the rapidly developing CNT-based electro-
chemical biosensors. Owing to the attractive properties of CNT, recent results have
demonstrated the advantages of CNT for the construction of a wide range of electro-
chemical enzyme-based biosensors, immunosensors, and DNA sensors. The remarkable
electrocatalytic activity toward hydrogen peroxide and NADH permits the fabrication of
low-potential amperometric biosensors. The electrical contacting of redox enzymes and
electrode through CNT electrical wires offers great promise for the development of medi-
ator-free biosensor. The use of CNTs offers enhanced electrocatalytic activity toward
