Biomedical Engineering Reference
In-Depth Information
nanomaterials have been reported to label DNA oligonucleotides in order to
achieve signii cant signal amplii cation [81-83]. In impedimetric genosens-
ing, nanomaterials have also been utilized with a second purpose: to study
and develop new sensing platforms with the aim of improving the analytical
response [15, 84, 85]. h e nanomaterials mostly used in impedimetric geno-
sensors have been essentially nanostructured carbon, nanostructured gold
and dif erent kinds of quantum dots. Dendritic structures have also recently
applied for impedimetric DNA sensing. ssDNA probes were immobilized on
cysteine aminoacid dendritic structures, that formed a monolayer on a gold
electrode [86]. h e specially generated 3D structures alowed for an increas-
ing amount o immobilized ssDNA probe, which also permitted a remarkable
sensitivity. In a similar work, third generation poly(amidoamine) (PAMAM)
dendrimer functionalized GaN nanowires were used as immobilization
platforms for ssDNA probes, achieving in this case aM labeless LOD [87].
Specii c sections are dedicated below to the description of the use of these
materials for DNA detection using electrochemical impedance spectroscopy.
4.3
Nanostructured Carbon Used in Impedimetric
Genosensors
4.3.1
Carbon Nanotubes and Nanostructured Diamond
In the past few years, carbon nanotubes (CNTs) have attracted the increas-
ing interest of many researchers due to their remarkable tensile strength,
high resistance, l exibility and other unique structural, mechanical, elec-
trical and physicochemical features [88, 89]. Besides these excellent
properties, their high specii c surface area and the possibility to directly
functionalize them with dif erent biomolecules [15] also make CNTs
extremely attractive for electrochemical sensing [90, 91].
Carbon nanotubes have been recently used as transducers for enhanced
electrical detection of DNA hybridization [80, 92]. In impedimetric geno-
sensors, numerous platforms employing dif erent kinds of CNTs, either
alone or combined in a composite with dif erent polymer or nanoparticles,
were lately fabricated, characterized, and employed for the detection of
DNA sequences [5].
Bonanni
et al.
employed commercial screen-printed carbon electrodes
modii ed with carboxyl acid-functionalized multiwalled carbon nanotubes
(MWCNTs-COOH) for the covalent immobilization of amino-modii ed
DNA probes by EDC-NHS chemistry. h e platform was then employed for
the impedimetric detection of oligonucleotide sequences specii c for either a
transgenic insect resistant Bt maize [85] or correlated to the H1N1 inl uenza A
virus gene [93]. Caliskan
et al.
[94] employed carboxylic acid-functionalized
