Biology Reference
In-Depth Information
benznidazole, thiophene-S-oxide, and nitroderivatives of polycyclic
aromatic compounds have been investigated [38-40].
Experimental arrangement for electrochemical DNA hybridiza-
tion biosensorsincludes the following:
(a) Label-free detection of strand breaks with mercury-based DNA
biosensors. These biosensors are based on strong dependence
of accessibility of DNA bases to the transducer surface (which
is lower at intact DNA compared with damaged DNA) and DNA
conformation (and/or local perturbations). Hence, mercury-
based DNA biosensors are able to discriminate between
DNA molecules containing (e.g., ssDNA) and lacking (e.g.,
sc plasmid DNA) free chain ends when free ends produce
specific electrochemical responses under certain conditions.
Nicking of supercoiled (sc) plasmid DNA with enzymes (such
as DNase I) as well as reactive radical species that destroy the
deoxyribose moieties, some types of nucleobase lesions after
their conversion to strand breaks by specific enzymes, and
repair of the strand breaks by action of the DNA ligases were
detected as well [13].
Detection of the sb at the hanging mercury drop electrode
(HMDE) is highly sensitive. By using alternating current (AC)
voltammetry, one sb was detected among more than 2
×
10
5
nucleotides [41]. Although conventional HMDE possesses such
unique features, successful attempts have been made to replace
itbyotherelectrodesinwhichtheliquidmercurycontentwould
be minimized or eliminated. Both redox and tensammetric DNA
signals have been measured at a mercury-film-coated solid
glassy carbon electrode (MF/GCE) and at different variants of
silver solid amalgam electrodes (AgSAE). MF/GCE [42], as well
asAgSAEandMF-AgSCE[43]modifiedwithscDNA,wasapplied
to sb formation.
(b) Detection of DNA degradation at carbon-based biosensors
using redox indicators. Deep degradation of DNA during the
step of biosensor incubation for a given time (minutes to
hours) in a cleavage medium under investigation, after the
medium exchange for the follow-up electrochemical measure-
ment, results into diminution of the voltammetric response
