4th EucheMs chemistry congress

Monday, 27-Aug 2012
s598
chem. Listy 106, s587–s1425 (2012)
Analytical chemistry Electrochemistry, Analysis, sample manipulation
Electroanalytical methods - iii
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eLeCtroAnALytiCAL deteCtion of
CyAnoBACteriAL hePAtotoxinS
MiCroCyStin-Lr And noduLArin And
their interACtion with dnA
A. M. oLiveirA-Brett 1 , i. C. LoPeS 1 , P. v. f. SAntoS 1 ,
v. C. diCuLeSCu 1
1 University of Coimbra, Department of Chemistry, Coimbra,
Portugal
Microcystin-LR (MC-LR) and nodularin (NOD) are among
the most commonly reported cyclic heptapeptides produced by
certain strains of freshwater cyanobacteria (blue-green algae),
hepatotoxic for humans and animals. These hepatotoxins act
mainly through the binding and consequent inhibition of
serine/threonine protein phosphatases inside the liver cells.
Beyond protein inhibition, other adverse toxicological effects
have been reported concerning MC-LR and NOD exposure, such
as intracellular glutathione alteration, reactive oxygen species
production and lipid peroxidation.
The electroanalytical behaviour of MC-LR and nodularin
NOD at a glassy carbon electrode was investigated using cyclic,
square-wave and differential pulse voltammetry. The oxidation of
MC-LR and NOD is an irreversible, diffusion-controlled and
pH-independent process that occurs with the transfer of only one
electron. Chemical degradation of MC-LR and NOD, upon
incubation in different pH electrolytes, was electrochemically
detected by the appearance of a new oxidation peak at a lower
potential, mainly in mild acid media. The MC-LR and NOD
chemical degradation product, formed homogenously in the buffer
solution, undergoes an irreversible pH-dependent oxidation.
The electrochemical study showed that oxidation and
cyanotoxins chemical degradation in aqueous media follow a
complex redox mechanism, and their electroanalytical
determination with a detection limit of one microgram per litre is
foreseen, which will provide very important and useful data for
toxicity evaluation.
The evaluation of the dsDNA interaction with MC-LR and
NOD was undertaken using a dsDNA-electrochemical biosensor
immersed in MC-LR or NOD solutions during different periods
of time. The in situ evaluation of the MC-LR and NOD interaction
with dsDNA using a DNA-electrochemical biosensor showed that
both MC-LR and NOD caused dsDNA structural modifications
in a time-dependent manner, adding more data to the studies of
genotoxicity and carcinogenic potential associated to these toxins.
Keywords: Microcystin-LR; nodularin; electroanalysis;
cyanobacterial hepatotoxins; DNA interaction;
Electroanalytical methods - iii
4 th EucheMs chemistry congress
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SiMuLtAneouS neurotrAnSMitterS AnALySiS
uSinG MiCroeLeCtrodeS BASed on
PorPhyrinS
r. i. StefAn-vAn StAden 1 , i. MoLdoveAnu 1 ,
J. f. vAn StAden1 1INCDEMC Timisoara Timus Romania, Laboratory of
Electrochemistry and PATLAB Bucharest, Bucharest, Romania
Email: iustinavanstaden@yahoo.com
Determination of neurotransmitters had an essential role in
assessment of neurological diseases. Maps of brain can be drawn
using the determination of the content of dopamine in different
parts of brain tissue. Therefore it is very important to develop
reliable and fast/real time methods of analysis for the
simultaneous assay of neurotransmitters such as dopamine,
epinephrine and norepinephrine. New amperometric
microelectrodes were designed and used for the simultaneous
assay of neurotransmitters. The microelectrodes used were based
on porphyrins immobilized in diamond paste. The optimization
of working conditions was done using cyclic voltammetry, for
different electrolyte solutions (e.g., KCl, NaCl, KNO ) at different
3
pH values. Response characteristics for the proposed
microelectrodes were determined for optimized working
conditions using differential pulse voltammetry. The
microelectrodes were used to determine the neurotransmitters
from biological fluids, such as urine samples. The performances
of the proposed microsensors were compared with the
performance obtained using a graphite paste based
microelectrode.
Acknowledgments: The present work was supported by
the European Commission through the DENAMIC project
(Contract-No. 282957).
Keywords: elecroanalysis; neurotransmitters; microelectrode;
AUGUst 26–30, 2012, PrAGUE, cZEcH rEPUbLIc