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ferroelectricity, ferromagnetism, piezoelectricity, and semiconduc-
tivity [38].
Recently, nanostructured TiO 2 particle (TiO 2 -NP) preparation
and their applications in photovoltaic studies, photocatalysis, and
environmental studies have attracted much attention mostly in the
emerging sensor technology based on nanoparticles and nanocom-
posites with chemical and biological molecules [33]. In protein-
based biosensors the e cient electrical communication between
redox proteins and solid electrode surfaces is still an important
request, and many methods have been tried in order to obtain
direct electrochemical responses of proteins embedded in surface
modifier films. An example for the latter is the work presented
by Zhou et al. [39] where the photovoltaic effect of TiO 2 -NPs,
inducedbyultravioletlight,cangreatlyimprovethecatalyticactivity
of hemoglobin as a peroxidase with increased sensitivity when
compared to the catalytic reactions in the dark, which indicates a
possible method to tune the properties of proteins for development
of photocontrolled protein-based biosensors. The method claims an
enhancement in the catalytic activity of hemoglobin, by a specific
interaction with 35 nm TiO 2 -NP, toward the H 2 O 2 reduction. This
catalytic effect was not observed by other comparative experiments
withfilms containingnanostructured CdS or ZnO 2 .
The advances in hybrid nanotechnology involving nucleic acids
are mostly linked with sequence-specific nucleic acid interactions.
TiO 2 -oligonucleotide nanocomposites retain the intrinsic photocat-
alyticcapacityofTiO 2 aswellasthebioactivityoftheoligonucleotide
DNA; therefore, the developments in this area have been oriented
toward cellular imaging and protein or DNA sensor microarrays
[38].
Lo et al . [38] reported a nanocomposite biosensor for the
amperometric detection of H 2 O 2 based on thionin incorporated
bilayer of DNA/nano-TiO 2 film-modified electrode. Furthermore,
thissystemshowedelectrocatalyticactivitytowardtheO 2 andH 2 O 2
reduction in physiologicalconditions.
Anano-TiO 2 substrate in combination with Au-NP-modified
DNA probe was used by Lu et al. [40] to develop a novel
photoelectrochemical method for quantitative detection of the
linear DNA hybridization. In the detection process schematized in
 
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