Biomedical Engineering Reference
In-Depth Information
could be substantially stronger and lighter than conventional equivalents
currently used in hospitals or point-of-care approaches.
For a wider acceptance of these genosensors, further research should be
mainly focused on the improvement of their reproducibility and stability.
Scientists should also increase ef orts to optimize the proposed electrode
assemblies for use in real clinical samples, overcoming all problems asso-
ciated with the complexity of clinical matrices. h e future application in
this i eld, together with the successful commercialization of a device, may
depend on improvements in several dif erent areas, including minimiza-
tion of the ef ects of nonspecii c adsorption. Recently, the implementation
of impedimetric DNA biosensors on a disposable paper with inkjet-printed
gold electrodes has been described [161]. h e work belongs to the current
and laudable trend of developing low cost of diagnostic tools that could be
implemented in developing countries [162].
It is clear that electrochemical impedance sensors are particularly
promising for portable, on-site applications, in combination with simpli-
i ed discrete-frequency instruments. In addition, the impedance technique
is fully compatible with multiplexed detections in electrically addressable
DNA chips, which will be one of the clear demands in genosensing in the
following years. Some of the DNA sensor technology described in this
chapter could be transferred from single analyte devices to electrochemical
methods, of ering the possibility of simultaneous measurements of a panel
of targets. h e multiplex detection only needs electrochemical addressing
of a number of electrochemical cells, which may be prepared, for example,
on a silicon chip. But, the modern sensing strategies, when coupled with
the rich information contained in impedance spectra, can deduct the pres-
ence of more than one gene from the signal generated by a single sensing
platform. In the work of Bonanni
et al.
[163], two dif erent genes were
immobilized on a single electrode, hybridization experiments were car-
ried out and impedance spectra were treated with a purposely trained arti-
i cial neural network, which was capable of deducting the presence of one
gene target, the other, both or none, illustrating the potentialities that can
be extracted, in this case, from intelligent sensor array devices.
To conclude, it must be mentioned that most of the principles shown are
also extensible to specii c detection of proteins, in this case taking advan-
tage of the DNA-protein interaction exploited by aptamer sensors [164],
even to the detection of metal ions, if DNAzymes are employed [165],
where in analogy to the protocols previously described, electrochemical
impedance spectroscopy can also be employed as the key transduction
principle. As mentioned above, the unique and attractive properties of
nanostructured materials may present new opportunities for the design
of highly sophisticated electroanalytical nanobiosensing devices. Due to
