Fabrication of Biosensors - Biosensors and Biosensor Kinetics - page 48

glucose biosensor. They report that a simple water-organic Nafion solution cast with a high
(85 wt%) content of organic solvent may be used to prepare the glucose biosensor. The addi-
tion of the graphite nanoplatelets greatly enhanced the redox peak current of ferrocyanide
solution. It also lowered the over potential for monitoring enzymatically produced hydrogen
peroxide.

3.2.10 Fabricaton of a Zinc Oxide Nanoparticle/Glucose Oxidase Biosensor
( Ren et al., 2009 )

Ren et al. (2009) have recently fabricated a biosensor using zinc oxide (ZnO) nanoparticles/
glucose oxidase. These authors report that enzymatic biosensors exhibit high sensitivity and
quick response times to different substrates; thus, they have been the subject of much
research. They further point out that different types of advanced materials have been used
to increase the sensitivity of enzyme electrodes ( Gerard et al., 2002; Xiao et al., 2003; Yang
et al., 2004; Ren et al., 2005; Salimi et al., 2007 ). They concede, however, that there is a
drawback in the sense that there is still inefficient electrical communication between the
enzyme's redox center and the solid electrode surfaces ( Zhou et al., 2005 ). This they opine
is because the enzyme active site is deeply buried in the protein shell.

Ren et al. (2009) indicate that semiconductor colloids exhibit unique electrical and optical
properties, and have been used in a variety of optoelectronic applications ( Alivisatos,
2004 ). Ren et al. (2009) point out that ZnO is an n-type semiconductor, which exhibits both
photoconductivity and photocatalytic activity and has been used in biosensor applications
( Liu et al., 2001 ). In essence, Ren et al. (2009) report that the photophysical properties of
semiconductor particles have been used to develop biosensor systems ( Curri et al., 2002;
Pardo-Yissar et al., 2003; Huang et al., 2005; Zhao et al., 2007; Umar et al., 2008 ). Ren
et al. (2009) have developed and characterized the performance of a glucose biosensor based
on ZnO particles.

Their results show that the ZnO nanoparticles significantly enhance the sensitivity of the GO x
enzyme electrode. They emphasize that their fabrication method of making a glucose biosen-
sor is simple and effective.

Ren et al. (2009) have recently used glucose oxidase (GO x )/ZnO as a model system to deter-
mine the photovoltaic effect of nanoparticles on the enzyme electrode. They noted that the
structure of the GO x was preserved after conjugation with ZnO particles. Also, the current
response increased with ZnO particles. The current response increased by 30%, and the
detecton limit was lowered by two orders of magnitude upon irradiating the enzyme electrode
for 2 h with UV light.

These authors used glucose oxidase (130 U/mg) E.C.1.1.3.4 from Aspergillus niger , and
b - D ( þ )-glucose oxidase. They synthesized the ZnO nanoparticles by precipitation from