Biomedical Engineering Reference
In-Depth Information
In the particular case of electrochemical (bio)sensors, the chemical pro-
cess is related to redox processes of the analyte and the transducer gener-
ates secondary electrical signals, like current or potential.
5.1.3
Graphene-based (bio)sensors: Generalities
As discussed in the past sections, GR is an excellent nanomaterial to be
used in the construction of electrodes and transducers in (bio)sensors.
Using enzymes as recognition agents for biosensors based on GR has
been proposed considering dif erent construction strategies, considering
that enzyme immobilization is a crucial step for the appropriate response
of biosensors. h e most important immobilization techniques are:
•
Adsorption technique
: In spite of being a simple and fast
technique, poor enzyme adsorption and reproducibility
has been reported when using this technique, although,
GR has represented a solution for some of these disadvan-
tages since it favors the adsorption of enzymes. To achieve
enzyme immobilization, GR is dispersed over conven-
tional electrodes, usually glassy carbon electrodes (GCE),
and an enzyme solution is placed in the surface and then
dried. h is adsorption technique has been employed for the
detection and quantii cation of phenols [34] and organo-
phosphates [35]
•
Covalent binding
: h is is a technique that allows direct
anchoring of the enzyme on the electrode via covalent
bonds. h is allows direct transfer of electrons to the enzyme
active site [36].
•
Electropolymerization
: In this technique, the enzyme is
mixed with a polymerizable monomer (usually pyrrole ,PPy)
and then an electrochemical technique is used for electropo-
lymerization (Figure 5.3). h e incorporation of the enzyme
in the polymer matrix is ot en achieved through electrostatic
interactions. h e advantages of this technique lie in the con-
trol when producing thin layers [37-40].
•
Layer by Layer (LBL)
: It is a regular technique employed in
the construction of biosensors. h is is based in the adsorp-
tion of counter-charge ions in the electrode's surface, where
it becomes possible the layers control. LBL in combination
with GR has demonstrated to improve de response of enzy-
matic biosensors.
