Fabrication of Biosensors - Biosensors and Biosensor Kinetics - page 37

and highly sensitive for the amperometric detection of glucose. They further emphasize that
the electrode surface could be easily and reproducibly renewed by polishing lightly with a
smooth paper.

The electrocatalyitc activity of their modified electrode is described by the following reaction
( Zhao et al., 2007 ):

OH ! Ni ð OH Þ 2 þ NiO ð OH Þþ e

ð 3 : 1 Þ

NiO ð OH Þþ glucose ! Ni ð OH Þ 2 þ glucolactone

They indicate that Ni 2 þ /Ni 3 þ species on the electrode surface acts as a catalyst for the oxida-
tion of glucose. Furthermore, Safavi et al. (2008) emphasize that the shape and morphology
of the nanoscale materials significantly affects their catalytic behavior.

Safavi et al. (2009) report that their biosensor is stable as it exhibits 95% of its initial
response value after 100 days. They also emphasize that their biosensor produces reproduc-
ible results in that a modified electrode yields results with an RSD (relative standard devia-
tion) of 3.4% from six successive amperometric measurements with a 2 mM glucose solution.
Finally, the use of their ionic binder not only increased the sensitivity of their biosensor, but
also increased its resistance toward electrode fouling significantly ( Zhao et al., 2007 ).

3.2.2 A Potentiometric Protein Sensor Using Surface Molecular Imprinting Method
( Wang et al., 2008)

Wang et al. (2008) report that the molecular imprinting (MI) method is a fast developing
technology, and has been used in biosensing applications ( Viatakis et al., 1993; Shea,
1994; Wulff, 1995; Bowma et al., 1998; Yano and Karube, 1999; Sellergren, 2000; Haupt,
2003; Hayden et al., 2003; Guo et al., 2004 ). Wang et al. (2008) point out that the traditional
MI recognition mechanism depends mainly on the precise spatial arrangement of functional
groups in the matrix to ensure selective recognition of target molecules. These authors have
fabricated a biosensor built with surface molecular imprinting of thiol SAMs (self-assembled
monolayers). These SAMs have the capacity to detect complex molecules with parts per mil-
lion accuracy. These authors demonstrate that their biosensor can detect globular proteins
such as myoglobin and hemoglobin with good sensitivity and selectivity. Wang et al.
(2008) report that the (a) attraction forces between the protein molecule and the gold surface,
(b) the hydrogen bonds between the hydrophilic groups of the protein surfaces and the -OH
groups at the thiol end, and (c) the specific arrangement of these interactions in shape and
orientation is responsible for the recognition and selectivity of their biosensor ( Shi et al.,
1999; Kaufmann et al., 2007 ).

The Wang et al. (2008) fabrication technique is described briefly. A gold-coated silicon chip
was used after cleaning with de-ionized water and dried with pure nitrogen gas. The authors