BIOMEDICAL APPLICATIONS II: INFLUENCE OF CARBON NANOTUBES IN CANCER THERAPY - Carbon Nanotubes: From Bench Chemistry to Promising Biomedical Applications - page 70

Table 3.1 Protein NSB on differently treated CNTs a

Functionalisation SA Avidin BSA GCD SpA
CNTs as pristine √ √ √ √ √
Tween 20-treated X X X X X
Pluronic P103-treated X X X X X
Triton X-100-treated X √ √ √ X
Dextran-treated √ √ √ √ √
Note : SA = streptavidin, BSA = bovin serum albumin, GCD = α -glucosidase, SPA =
staphylococcal protein A; √ = non-speciic binding; X = no binding detected.

Adapted from Chen et al. 78

a

The polyethylene oxide approach seems to be promising in the ield of
non-speciic recognition, and it follows the principle of rendering CNTs'
surface hydrophilic, while the linkage of an antibody is strongly recommended
to improve the biosensor's speciicity and sensitivity. 76 This preparation is
based on covalent functionalisation of CNTs with the formation of amide
bonds between proteins and CNT surfaces.
There are two main types of immunosensors, the already cited CNT-based
ield effect transistors (FETs) and the electrochemical immunosensors.
FETs are used for weak-signal ampliication, and they are made of a
source electrode, a drain electrode and, in between, a channel with a deined
physical diameter where a current low passes along a semiconductor path
(Fig. 3.14). A voltage is applied to the gate electrode, and as it varies, the
electrical diameter of the channel changes: the conductivity depends on this
diameter. FETs amplify signals on the basis of small changes in gate voltage,
since they cause a large variation in the current from source to drain. This
great sensitivity renders them particularly suitable for immunobiosensor
applications.

Figure 3.14 Schematic representation of an immunobiosensor.