Ales Danhel - Academia.edu (original) (raw)
Papers by Ales Danhel
Electrochimica Acta, 2014
Voltammetric behaviour of novel synthetic multi-redox DNA label N-methyl-4-hydrazino-7nitrobenzof... more Voltammetric behaviour of novel synthetic multi-redox DNA label N-methyl-4-hydrazino-7nitrobenzofurazan (NBF), a deoxycytidine monophosphate conjugate with NBF via formylthiophene linker (dC NBF MP), and NBF labeled model short double stranded DNA (dsDNA-NBF) were systematically studied at mercury meniscus modified silver solid amalgam electrode (m-AgSAE) for the first time in this work. Successful enzymatic incorporation of the NBF labeled deoxycytidine triphosphate into the DNA was confirmed and the dsDNA-NBF offered new more positive cathodic signals at −520 mV and −1160 mV, compared to the nucleic acid itself. Used modification resulted in increase of selectivity and sensitivity of the DNA voltammetric determination. Next to the pioneering voltammetric behaviour of all studied compounds at m-AgSAE, electroanalytical methods based on cyclic voltammetry, adsorptive stripping cyclic voltammetry and open circuit transfer stripping cyclic voltammetry were developed for sensitive detection of these (bio)molecules. Furthermore, utilization of variable negative vertex potential and scan rate was also observed and their appropriate selection considerably influenced registered peaks on cyclic voltammograms. These redox processes increased signal response diversity and offered utilization of signal switch on/off technique, as well. Tentative electrochemical reduction mechanisms of the NBF, dC NBF MP and dsDNA-NBF were proposed and discussed, together with possibilities and limitations of the NBF + m-AgSAE system.
Electrochimica Acta, 2014
A detailed voltammetric study of 2,4-dinitrophenylhydrazine (DNPH), a DNPH modified nucleotide (d... more A detailed voltammetric study of 2,4-dinitrophenylhydrazine (DNPH), a DNPH modified nucleotide (dC DNPH MP) and a short single stranded DNA (ssDNA-DNPH) at mercury meniscus modified silver solid amalgam electrode (m-AgSAE) is presented in this work. Electrochemical behaviour of these compounds was studied using cyclic voltammetry (CV), adsorptive stripping CV and open circuit adsorptive transfer stripping CV. Adsorptive and transfer stripping techniques offered sensitive detection of the studied compounds at submicromolar levels with low sample volume consumption (about 0.5 l), respectively. The ssDNA-DNPH gives three specific cathodic signals related to the reduction of the redox label. All these signals advantageously appear at significantly less negative potentials than unmodified nucleic acid and they may be optionally switched on/off by properly adjusted potential windows and scan rates. This opportunity increases signal response diversity and selectivity in DNA sensing. Mechanism of electrochemical reduction of the studied compounds is proposed. Thanks to a better mechanical stability, easy handling and sufficient sensitivity, the m-AgSAE appears/seems to be more potent alternative to the hanging mercury drop electrode and better suited for biosensor development. Successful incorporation of the DNPH labeled nucleoside triphosphate into the DNA structure shows that selected DNA polymerase tolerates this bulky moiety and can be used, in combination with electrochemical methods utilizing m-AgSAE, in further development of various applications.
Electroanalysis, 2010
ABSTRACT
Electroanalysis, 2009
The use of a silver solid amalgam working electrode for HPLC with electrochemical detection has b... more The use of a silver solid amalgam working electrode for HPLC with electrochemical detection has been investigated. The thin-layer and wall-jet detectors based on this electrode were constructed and applied for the determination of a mixture of nitrophenols. The optimal separation and detection conditions for the determination of 2-nitrophenol, 4nitrophenol, 2,4-dinitrophenol and 2-methoxy-5-nitrophenol in mixture were found using RP-HPLC at Nova-Pack C18 column and amperometric detection with the above mentioned detectors. It has been proved that the silver solid amalgam electrode is a suitable working electrode for HPLC-ED and provides sufficient sensitivity for determination of tested nitrophenols.
Current Organic Chemistry, 2011
Analytical Sciences, 2012
The electrochemical behavior and application of a new sensor, a silver solid amalgam paste electr... more The electrochemical behavior and application of a new sensor, a silver solid amalgam paste electrode (AgSA-PE), based on the mixture of a fine silver solid amalgam powder (60:40 (wHg/wAg)) and a suitable organic pasting liquid (Paraffin oil) in a ratio of 20:1 (w/w), was investigated in an aqueous-methanolic media (1:1). This alternative working electrode provides simple preparation and handling, adequate mechanical stability, easily renewable electrode surface, sufficiently wide cathodic potential window (up to-1200 mV within a pH range of 2.7-12.3), and sufficient sensitivity without any necessary pretreatment. The practical usability of the AgSA-PE was verified by the development of voltammetric methods for the determination of selected environmentally important pollutants (1,3-, 1,5-, and 1,8-dinitronaphthalenes) in an aqueous-methanolic media (1:1). The differential pulse voltammetric methods at AgSA-PE give linear concentration dependences in the range of 1-100 μmol l-1 with limits of detection of about 1 μmol l-1 in a mixture of Britton-Robinson buffer of appropriate pH and methanol (1:1).
Analytica Chimica Acta, 1997
Abstract The polarographic behaviour of anthraquinone dye Ostacetate Blue P3R in a mixed water–et... more Abstract The polarographic behaviour of anthraquinone dye Ostacetate Blue P3R in a mixed water–ethanol (1 : 9) medium was investigated, and optimal conditions were found for its determination by DC tast polarography in the 20–700 μmol l −1 concentration range, by differential pulse polarography at a dropping mercury electrode in the 1–70 μmol l −1 concentration range, as well as by differential pulse voltammetry at a hanging mercury drop electrode in the 0.2–1 μmol l −1 concentration range. The sensitivity of the determination can be further improved through adsorptive accumulation of the test substance on the surface of the hanging mercury drop electrode; five minutes accumulation in unstirred solution allows determination in the 0.02–1 μmol l −1 concentration range. Practical applicability of the newly developed methods in river water was demonstrated.
Different types of silver amalgam electrodes have been introduced as modern and promising replace... more Different types of silver amalgam electrodes have been introduced as modern and promising replacements for traditional mercury electrodes. Advantages and possibilities of these novel electrode materials were highlighted and demonstrated at a number of sensitive voltammetric and amperometric (HPLC, flow injection analysis) methods developed in our UNESCO Laboratory of Environmental Electrochemistry in the last five years. The determined analytes were hazardous organic chemical carcinogens and genotoxic environmental pollutants, pesticides, antitumor, antibiotic and antivirotic drugs, and explosives containing electrochemically reducible nitro, nitroso, azido, and oxo groups.
Chemicke Listy, May 1, 2010
Sensors and Actuators B: Chemical
Electrodeposition of silver amalgam particles (AgAPs) on various substrates offers perspective to... more Electrodeposition of silver amalgam particles (AgAPs) on various substrates offers perspective tool in development of novel electrochemical detection system applicable even in direct bioelectrochemistry of nucleic acids or proteins. Herein, a double pulse chronoamperometric deposition of AgAPs on in-house fabricated screen-printed silver electrodes (SPAgE) has been optimized using voltammetric signal of model electrochemically reducible organic nitro-compound, 4-nitrophenol, and scanning electron microscopy with energy dispersive X-ray spectrometer. This compact sensor including graphite counter and Ag|AgCl pseudo-reference electrode was design for highly effective analysis of electrochemically reducible compounds in 96-well plate with about 150-µl sample volume per well. The SPAgE-AgAP offers detection of 4-NP down to 5 µmol.l−1 using cyclic voltammetry in acetate buffer pH 5.0. Advantageously, differential pulse voltammetry at SPAgE-AgAP allows highly sensitive detection system of...
Journal of Electroanalytical Chemistry
Bioelectrochemistry
Catalytic properties and high adsorption affinity of nucleic acids and proteins to silver amalgam... more Catalytic properties and high adsorption affinity of nucleic acids and proteins to silver amalgam electrode surface make this kind of electrified interface perspective for bioanalytical and biomedical applications. For the first time, a basal-plane pyrolytic graphite electrode (bPGE) has been used as a substrate for electrodeposition of silver amalgam particles (AgAPs). Optimization of the resulting composition, surface morphology and electrochemical properties of the AgAPs was done by scanning electron microscopy with energy disperse X-ray spectroscopy, image processing software and voltammetric detection of electrochemically reducible model organic nitro compound, 4-nitrophenol. Spectro-electrochemical applicability of bPGE-AgAP has been demonstrated by electrolysis of 4-nitrophenol. Simultaneous UV-Vis-chronoamperometry provided information on the number of exchange electrons and the reduction rate constants. Preferential adsorption of the fluorescently labelled calf thymus DNA and the green fluorescent protein (GFP) on the surface of AgAPs was observed by fluorescence microscopy. In contrast to previously studied indium-tin oxide and vapour-deposited gold decorated by AgAPs, herein the presented bPGE-AgAP has provided sufficiently wide negative potential window allowing direct electroanalysis of non-labelled DNA and GFP using intrinsic electrochemical signals independently of the fluorescent labelling. The bPGE-AgAP can thus be expected to find application opportunities in protein electrochemistry, (bio)sensor development or in-situ spectro-electrochemical studies.
Electrochimica Acta, 2014
Voltammetric behaviour of novel synthetic multi-redox DNA label N-methyl-4-hydrazino-7nitrobenzof... more Voltammetric behaviour of novel synthetic multi-redox DNA label N-methyl-4-hydrazino-7nitrobenzofurazan (NBF), a deoxycytidine monophosphate conjugate with NBF via formylthiophene linker (dC NBF MP), and NBF labeled model short double stranded DNA (dsDNA-NBF) were systematically studied at mercury meniscus modified silver solid amalgam electrode (m-AgSAE) for the first time in this work. Successful enzymatic incorporation of the NBF labeled deoxycytidine triphosphate into the DNA was confirmed and the dsDNA-NBF offered new more positive cathodic signals at −520 mV and −1160 mV, compared to the nucleic acid itself. Used modification resulted in increase of selectivity and sensitivity of the DNA voltammetric determination. Next to the pioneering voltammetric behaviour of all studied compounds at m-AgSAE, electroanalytical methods based on cyclic voltammetry, adsorptive stripping cyclic voltammetry and open circuit transfer stripping cyclic voltammetry were developed for sensitive detection of these (bio)molecules. Furthermore, utilization of variable negative vertex potential and scan rate was also observed and their appropriate selection considerably influenced registered peaks on cyclic voltammograms. These redox processes increased signal response diversity and offered utilization of signal switch on/off technique, as well. Tentative electrochemical reduction mechanisms of the NBF, dC NBF MP and dsDNA-NBF were proposed and discussed, together with possibilities and limitations of the NBF + m-AgSAE system.
Electrochimica Acta, 2014
A detailed voltammetric study of 2,4-dinitrophenylhydrazine (DNPH), a DNPH modified nucleotide (d... more A detailed voltammetric study of 2,4-dinitrophenylhydrazine (DNPH), a DNPH modified nucleotide (dC DNPH MP) and a short single stranded DNA (ssDNA-DNPH) at mercury meniscus modified silver solid amalgam electrode (m-AgSAE) is presented in this work. Electrochemical behaviour of these compounds was studied using cyclic voltammetry (CV), adsorptive stripping CV and open circuit adsorptive transfer stripping CV. Adsorptive and transfer stripping techniques offered sensitive detection of the studied compounds at submicromolar levels with low sample volume consumption (about 0.5 l), respectively. The ssDNA-DNPH gives three specific cathodic signals related to the reduction of the redox label. All these signals advantageously appear at significantly less negative potentials than unmodified nucleic acid and they may be optionally switched on/off by properly adjusted potential windows and scan rates. This opportunity increases signal response diversity and selectivity in DNA sensing. Mechanism of electrochemical reduction of the studied compounds is proposed. Thanks to a better mechanical stability, easy handling and sufficient sensitivity, the m-AgSAE appears/seems to be more potent alternative to the hanging mercury drop electrode and better suited for biosensor development. Successful incorporation of the DNPH labeled nucleoside triphosphate into the DNA structure shows that selected DNA polymerase tolerates this bulky moiety and can be used, in combination with electrochemical methods utilizing m-AgSAE, in further development of various applications.
Electroanalysis, 2010
ABSTRACT
Electroanalysis, 2009
The use of a silver solid amalgam working electrode for HPLC with electrochemical detection has b... more The use of a silver solid amalgam working electrode for HPLC with electrochemical detection has been investigated. The thin-layer and wall-jet detectors based on this electrode were constructed and applied for the determination of a mixture of nitrophenols. The optimal separation and detection conditions for the determination of 2-nitrophenol, 4nitrophenol, 2,4-dinitrophenol and 2-methoxy-5-nitrophenol in mixture were found using RP-HPLC at Nova-Pack C18 column and amperometric detection with the above mentioned detectors. It has been proved that the silver solid amalgam electrode is a suitable working electrode for HPLC-ED and provides sufficient sensitivity for determination of tested nitrophenols.
Current Organic Chemistry, 2011
Analytical Sciences, 2012
The electrochemical behavior and application of a new sensor, a silver solid amalgam paste electr... more The electrochemical behavior and application of a new sensor, a silver solid amalgam paste electrode (AgSA-PE), based on the mixture of a fine silver solid amalgam powder (60:40 (wHg/wAg)) and a suitable organic pasting liquid (Paraffin oil) in a ratio of 20:1 (w/w), was investigated in an aqueous-methanolic media (1:1). This alternative working electrode provides simple preparation and handling, adequate mechanical stability, easily renewable electrode surface, sufficiently wide cathodic potential window (up to-1200 mV within a pH range of 2.7-12.3), and sufficient sensitivity without any necessary pretreatment. The practical usability of the AgSA-PE was verified by the development of voltammetric methods for the determination of selected environmentally important pollutants (1,3-, 1,5-, and 1,8-dinitronaphthalenes) in an aqueous-methanolic media (1:1). The differential pulse voltammetric methods at AgSA-PE give linear concentration dependences in the range of 1-100 μmol l-1 with limits of detection of about 1 μmol l-1 in a mixture of Britton-Robinson buffer of appropriate pH and methanol (1:1).
Analytica Chimica Acta, 1997
Abstract The polarographic behaviour of anthraquinone dye Ostacetate Blue P3R in a mixed water–et... more Abstract The polarographic behaviour of anthraquinone dye Ostacetate Blue P3R in a mixed water–ethanol (1 : 9) medium was investigated, and optimal conditions were found for its determination by DC tast polarography in the 20–700 μmol l −1 concentration range, by differential pulse polarography at a dropping mercury electrode in the 1–70 μmol l −1 concentration range, as well as by differential pulse voltammetry at a hanging mercury drop electrode in the 0.2–1 μmol l −1 concentration range. The sensitivity of the determination can be further improved through adsorptive accumulation of the test substance on the surface of the hanging mercury drop electrode; five minutes accumulation in unstirred solution allows determination in the 0.02–1 μmol l −1 concentration range. Practical applicability of the newly developed methods in river water was demonstrated.
Different types of silver amalgam electrodes have been introduced as modern and promising replace... more Different types of silver amalgam electrodes have been introduced as modern and promising replacements for traditional mercury electrodes. Advantages and possibilities of these novel electrode materials were highlighted and demonstrated at a number of sensitive voltammetric and amperometric (HPLC, flow injection analysis) methods developed in our UNESCO Laboratory of Environmental Electrochemistry in the last five years. The determined analytes were hazardous organic chemical carcinogens and genotoxic environmental pollutants, pesticides, antitumor, antibiotic and antivirotic drugs, and explosives containing electrochemically reducible nitro, nitroso, azido, and oxo groups.
Chemicke Listy, May 1, 2010
Sensors and Actuators B: Chemical
Electrodeposition of silver amalgam particles (AgAPs) on various substrates offers perspective to... more Electrodeposition of silver amalgam particles (AgAPs) on various substrates offers perspective tool in development of novel electrochemical detection system applicable even in direct bioelectrochemistry of nucleic acids or proteins. Herein, a double pulse chronoamperometric deposition of AgAPs on in-house fabricated screen-printed silver electrodes (SPAgE) has been optimized using voltammetric signal of model electrochemically reducible organic nitro-compound, 4-nitrophenol, and scanning electron microscopy with energy dispersive X-ray spectrometer. This compact sensor including graphite counter and Ag|AgCl pseudo-reference electrode was design for highly effective analysis of electrochemically reducible compounds in 96-well plate with about 150-µl sample volume per well. The SPAgE-AgAP offers detection of 4-NP down to 5 µmol.l−1 using cyclic voltammetry in acetate buffer pH 5.0. Advantageously, differential pulse voltammetry at SPAgE-AgAP allows highly sensitive detection system of...
Journal of Electroanalytical Chemistry
Bioelectrochemistry
Catalytic properties and high adsorption affinity of nucleic acids and proteins to silver amalgam... more Catalytic properties and high adsorption affinity of nucleic acids and proteins to silver amalgam electrode surface make this kind of electrified interface perspective for bioanalytical and biomedical applications. For the first time, a basal-plane pyrolytic graphite electrode (bPGE) has been used as a substrate for electrodeposition of silver amalgam particles (AgAPs). Optimization of the resulting composition, surface morphology and electrochemical properties of the AgAPs was done by scanning electron microscopy with energy disperse X-ray spectroscopy, image processing software and voltammetric detection of electrochemically reducible model organic nitro compound, 4-nitrophenol. Spectro-electrochemical applicability of bPGE-AgAP has been demonstrated by electrolysis of 4-nitrophenol. Simultaneous UV-Vis-chronoamperometry provided information on the number of exchange electrons and the reduction rate constants. Preferential adsorption of the fluorescently labelled calf thymus DNA and the green fluorescent protein (GFP) on the surface of AgAPs was observed by fluorescence microscopy. In contrast to previously studied indium-tin oxide and vapour-deposited gold decorated by AgAPs, herein the presented bPGE-AgAP has provided sufficiently wide negative potential window allowing direct electroanalysis of non-labelled DNA and GFP using intrinsic electrochemical signals independently of the fluorescent labelling. The bPGE-AgAP can thus be expected to find application opportunities in protein electrochemistry, (bio)sensor development or in-situ spectro-electrochemical studies.