Osteryoung Square Wave Voltammetry Research Articles

Study of electrochemical behavior of two chemically similar acridines: Tacrine and 9-aminoacridine on hanging mercury drop electrode

ABSTRACT. The electrochemical behavior of two chemically related acridine compounds: tacrine (TAC) and 9-aminoacridine (9-AA) was investigated on a hanging mercury drop electrode (HDME). The electrochemical study was carried out by using Osteryoung square wave voltammetry (OSWV) and cyclic voltammetry (CV) techniques in the Britton-Robinson (B-R) buffer solution at pH = 2.0–12.0, KCl (0.1/0.2/0.3 M) and methanol (0.0-50%) mixture as supporting electrolyte. TAC showed maximum current at pH 7.5 while 9-AA at pH 10, KCl (0.3M), and 10% methanol. The study of electrochemical reduction of 9-AA and TAC on the HDME by using CV resulted in a quasi-reversibility, mainly diffusion-controlled reaction. The reaction involved 1e–/1H+ reduction at nitrogen atom in the case of the 9-AA while the second process involved the 2e–/2H+ reduction of the intra-cyclic azomethine group. The reduction peak potential of structurally related acridine compounds is influenced by the pH values and percentage of the organic solvent of the supporting electrolytes. Also, the study may provide insight into the electron transfer pathways of biological reactions of the acridines and their electrochemical behavior on the electrode.
 
 KEY WORDS: Tacrine, 9-Aminoacridine, Cyclic voltammetry, Osteryoung square wave voltammetry, Hanging mercury dropping electrode
 
 Bull. Chem. Soc. Ethiop. 2021, 35(3), 639-646.
 DOI: https://dx.doi.org/10.4314/bcse.v35i3.14

Synthesis and characterization of C60 and C70 acetylacetone monoadducts and study of their photochemical properties for potential application in solar cells

We report on the synthesis of C60 and C70 monoadducts at room temperature through the Bingel reaction; employing acetylacetone as ligand; in presence of DBU (1,8-Diazabicyclo [5.4.0] undec-7-ene), carbon tetrabromide (CBr4), and o-dichlorobenzene. Diacetylmethane-[C60-Ih]-fullerene-[5,6] and diacetylmethane-[C70-D5h]-fullerene-[5,6] monoadducts were obtained with yields of 69% and 44%, respectively. The products were purified by column chromatography (CC, on silica gel, using hexane, carbon disulfide, and chloroform as eluents at room temperature) and characterized by Nuclear Magnetic Resonance (1H and 13C), Fourier-Transform Infrared (FT-IR) and UV-Visible spectroscopies, Matrix-assisted Laser Desorption/Ionization-Time of Flight (MALDI-TOF) Mass spectrometry, Cyclic Voltammetry (CV), and Osteryoung Square Wave Voltammetry (OSWV). Both compounds showed irreversible reduction peaks controlled by diffusion, with LUMO energy levels of -3.09 eV, -3.13 eV for C60, and C70 monoadducts, respectively. These values are comparable with the -3.99 eV of PC61BM. The synthetized adducts were incorporated into inverted-type perovskite solar cells and were used as electron transporting materials (ETM) obtaining power conversion efficiencies (PCE) of 8.5% and 14.0% for the C60 and C70 monoadducts, respectively. When C60 is replaced by a lower symmetrical fullerene such as C70 an improved light absorption in the visible region is observed.

Photophysical and Electrochemical Properties of a Zinc(II) [2×2] Metallogrid and its Bis(hydrazone) Ditopic Ligand

AbstractHerein we describe the synthesis and structural characterization of a [2x2] metallogrid of Zinc(II) and its ditopic bis(hydrazone) ligand, as well as the evaluation of their photo‐physical and electrochemical properties. The synthesis of the bis(hydrazone) involves an aromatic nucleophilic substitution followed by a condensation. Then, through complexation with Zinc(II) ions the [2x2] metallogrid was obtained. The bis(hydrazone) was subjected to UV light‐induced E/Z isomerization determining its kinetic constants through Nuclear Magnetic Resonance (NMR). A clear effect of the metal and the structure was observed on the redox potentials of the metallogrid and its ligand when studied by Cyclic Voltammetry (CV) and Osteryoung Square Wave Voltammetry (OSWV). All compounds were also studied through UV‐Vis and Fluorescence spectroscopy, observing, in some cases, a pronounced pH‐effect. Our results indicate that the photophysical properties of metallogrid can be tuned through the elimination of the acidic protons from the bis(hydrazone) ligands and, together with their electrochemical properties can be used as molecular switches.

Redox-Active Monolayers Self-Assembled on Gold Electrodes-Effect of Their Structures on Electrochemical Parameters and DNA Sensing Ability.

The background: The monolayers self-assembled on the gold electrode incorporated transition metal complexes can act both as receptor (“host” molecules) immobilization sites, as well as transducer for interface recognitions of “guest” molecules present in the aqueous solutions. Their electrochemical parameters influencing the sensing properties strongly depend on the transition metal complex structures. The objectives: The electrochemical characterization of the symmetric terpyridine–M2+–terpyridine and asymmetric dipyrromethene–M2+–terpyridine complexes modified with ssDNA probe covalently attached to the gold electrodes and exploring their ssDNA sensing ability were the main aims of the research presented. The methods: Two transition metal cations have been selected: Cu2+ and Co2+ for creation of redox-active monolayers. The electron transfer coefficients indicating the reversibility and electron transfer rate constant measuring kinetic of redox reactions have been determined for all SAMs studied using: Cyclic Voltammetry, Osteryoung Square-Wave Voltammetry, and Differential Pulse Voltammetry. All redox-active platforms have been applied for immobilization of ssDNA probe. Next, their sensing properties towards complementary DNA target have been explored electrochemically. The results: All SAMs studied were stable displaying quasi-reversible redox activity. The linear relationships between cathodic and anodic current vs. san rate were obtained for both symmetric and asymmetric SAMs incorporating Co2+ and Cu2+, indicating that oxidized and reduced redox sites are adsorbed on the electrode surface. The ssDNA sensing ability were observed in the fM concentration range. The low responses towards non-complementary ssDNA sequences provided evidences for sensors good selectivity. The conclusions: All redox-active SAMs modified with a ssDNA probe were suitable for sensing of ssDNA target, with very good sensitivity in fM range and very good selectivity. The detection limits obtained for SAMs incorporating Cu2+, both symmetric and asymmetric, were better in comparison to SAMs incorporating Co2+. Thus, selection of the right transition metal cation has stronger influence on ssDNA sensing ability, than complex structures.

Ion-channel mimetic sensor incorporating an anion-binding cyclopeptide designed for sulfate determination in dilute aqueous solutions

A sensor designed for anion detection in water based on an ion-channel mimetic system is described. This sensor consists of a gold electrode modified with an anion-binding cyclopeptide CP that mediates the recognition of sulfate. The number of CP molecules covalently attached to the gold electrode via AuS bonds was controlled by using 6-mercapto-1-hexanol (MCH) as “diluent” molecule. The optimal molar ratio CP/MCH (10−6 M/10−6 M) in the solution used for electrode modification was determined experimentally. The presence of CP molecules as well as their orientation on the gold surface was studied by using voltammetry techniques, contact angle measurements, and atomic force microscopy. The electrolyte composition as well as the appropriate pH suitable for anion recognition was also determined. Anion detection was explored by using cyclic voltammetry (CV) and Osteryoung Square wave voltammetry (OSWV). The developed sensor was shown to allow detection of sulfate in highly dilute aqueous media with a 0.25 pM detection limit. Chloride, phosphate and acetate anions generated substantially lower responses.

Label-free Electrochemical Immunosensors for Viruses and Antibodies Detection-Review

This article reviews the electrochemical immunosensors de-veloped by the successive modification of gold as well as glassy car-bon electrodes. Antibody or antigen fragments have been applied as the sensing elements. The complex between virions and specific anti-body adsorbing on a surface of an electrode forms an insulating layer. This phenomenon, which is a base of ion – channel mimetic type of immunosensors, can be monitored by Osteryoung square-wave vol-tammetry (OSWV) and electrochemical impedance spectroscopy (EIS) in the presence of [Fe(CN)6]3-/4- as a redox marker. Another type of immunosensors are based on redox active layers incorporated di-pyrromethene -Cu(II) or phenanthroline – Epoxy - Fe(III) complex-es. Changes of electrochemical parameters of redox centres upon tar-get analyte binding are the basis of analytical signal generation. Both type of immunosensors displayed better sensitivity in comparison to ELISA as well as being very selective. The matrix has no influence on the immunosensors performance. These devices could be recommend-ed for the direct electrochemical detection of viruses as well as anti-bodies in physiological samples.

Cathodic Stripping Voltammetric Determination of Cerium Using Indium Tin Oxide (ITO)

AbstractDue to its numerous applications in the field of metallurgy and its role as an alloying element for slowing down the biodegradation of pure magnesium typically known to have very low corrosion resistance, the need to develop simple and inexpensive methods for determination of cerium is important. Ce3+ was determined by cathodic stripping voltammetry (CSV) using Osteryoung square‐wave voltammetry (OSWV) for the stripping step. Indium tin oxide (ITO) was used as the working electrode because of its very good positive potential range with smooth background current. Under optimized conditions, the calibration plot was linear in the concentration range of 100 nM to 700 nM Ce3+. A calculated detection limit of 5.8 nM was found for a 5 min deposition time at ITO based on the 3σ method. Interference from selected metal ions was also examined, and no significant interferences were observed. The good selectivity of this sensor makes it a good candidate for practical applications such as monitoring Ce3+ released into solution during the biodegradation of Mg−Ce alloys being developed for resorbable biomedical implants.

Electrochemical Molecular Recognition System Utilizing Current Amplification of Metal Complexes Assembled on Gold Nanoparticles

Introduction Because gold nanoparticles (GNP) have a characteristic color and the color changes by their aggregation, the optical molecular recognitions are widely investigated by using a color change. However, we reported that the electrochemical sugar recognition system using tris(acetylacetonato)ruthenium complex and boronic acid assembled on the GNP showed a glucose-selectivity and higher sensitivity in 10-6 M order than optical recognition.1) It is considered that one of the reasons of high sensitivity may be the amplification of the reduction current of tris(acetylacetonato)ruthenium complex by assembly on the GNP. This electrochemical molecular recognition system has a great advantage that the molecular recognition site can exchange to others according to the target molecules. Furthermore, the metal complex can also change to the others according to avoid the disturbance from coexistent redox active species. That is, the redox potential can select by changing the redox active complex. Purpose For the purpose of the verification of the current amplification and the utility of this electrochemical molecular recognition system using the GNP, in this work, ferrocene (Fc), tris(acetylacetonato)ruthenium ([Ru(acac)3]), bis(acetylacetonato)ruthenium ([Ru(acac)(BP)2], BP = pyridine boronic acid), and bipylidine ruthenium ([Ru(py)(bpy)(trpy)]) were assembled on the GNP as electroactive site. Boronic acid (BA) for recognition of sugar, dipicolilamine (DPY) for recognition of phosphate derivatives (ADP, ATP, etc.), succinimide (SCI) for recognition of dopamine (DA), and crown ether (CE) for recognition of cesium ion were assembled on the GNP. Thus, the six kinds of GNP complexes (GNP/[Ru(acac)(BP)2]/BA, GNP/Fc/BA, GNP/[Ru(py)(bpy)(trpy)]/BA, GNP/[Ru(acac)3]/DPY, GNP/[Ru(acac)3]/CE), and GNP/[Ru(acac)3]/SCI) prepared and investigated molecular recognition functions. Osteryoung square wave voltammetry (OSWV) or differential pulse voltammetry (DPV) were used for the electrochemical measurements. Results 1. Current Amplification: In order to confirm the current amplification, the concentration dependence of the reduction current of the [Ru(acac)3] and of GNP/[Ru(acac)3] were measured and their slopes were compared. The slope for GNP/[Ru(acac)3] was ca. 29 times larger than that for [Ru(acac)3]. For oxidation current of ferrocene, the slope for GNP/Fc was ca. 7 times larger than that for Fc. In the silver nanoparticle system, further current amplification was observed, so it is considered that the kind of nanoparticle seem to affect the current amplification. The mechanism of the current amplification is not yet clear, but the electron tunneling due to the electron conductivity of the GNP may be considered as main factor of the current amplification mechanism.2. Molecular Recognition: In the electrochemical measurement, the current values decreased by adding the target molecules. In the case of sugar recognition by BA, GNP/[Ru(acac)3]/BA showed highest sensitivity among three types of GNP complexes (GNP/[Ru(acac)3]/BA, GNP/Fc/BA, and GNP/[Ru(py)(bpy)(trpy)]/BA). Sensitivity of [Ru(py)(bpy)(trpy)] was slightly less than two metal complexes. Each complex showed different selectivity for three kinds of sugars. For GNP/[Ru(acac)(BP)2]/BAsystem (recognition site (BP) is on the Ru complex), sensitivity is higher than that of GNP/[Ru(acac)3]/BA, although the selectivity did not show for three kinds of sugar. GNP/[Ru(acac)3]/(DPY+Zn2+) could be recognized phosphate derivatives such as AMP, ADP, and ATP with high sensitivity (10-6 M order) in the presence of Zn2+. Furthermore, slight ATP selectivity was obtained. GNP/[Ru(acac)3]/CE showed an excellent sensitivity for cesium ion (10-9 M order). In this case, it was consider that the aggregation caused by CE ring sandwiching for cesium ion increased the sensitivity, because the CE (18-crown-6) ring size was smaller than cesium ion diameter. In this case, two types of GNP (type A and type B) complexes were prepared. In type A, CE probe has longer alkyl chain than [Ru(acac)3] probe, and in type B CE probe has same length as [Ru(acac)3] probe. Type A may aggregate more than type B, because there is no steric obstruction by [Ru(acac)3]. As a result, the detection limit of the type A is 0.4 nM and 10 times as sensitive as type B. For the recognition of dopamine, the aggregation of GNP is brought about by the complexation of dopamine in the presence of Fe3+. As a result, high sensitivity was attained (LOD = 3 nmol dm-3).By using this electrochemical molecular recognition system, target molecules could be recognized with high sensitivity of mM – nM. The sensitivity and selectivity was depending on the kind of electroactive metal complex. Thus, it was verified the utility of this electrochemical molecular recognition system using metal complexes assembled on gold nanoparticles. 1) A.Endo, M. Kimura, T. Hashimoto, and T. Hayashita, Anal. Methods, 2014, 6(22), 8874-8877. Figure 1

Study of Ion Transfer Coupling with Electron Transfer by Hydrophilic Droplet Electrodes.

In a hydrophilic droplet three-electrode system, electroactive species within the droplet play very important roles in the electron-transfer (ET) process on the solid/electrolyte interface, which can then induce an ion-transfer (IT) reaction at the liquid/liquid interface. In this work, several redox couples and electroactive species are chosen to study ET-IT coupling processes at the water/1,2-dichloroethane (W/DCE) interface by cyclic voltammetry (CV) and Osteryoung square wave voltammetry (OSWV). Among them, the redox couple Ru(NH3)6(3+/2+) has been found to have the widest useful potential window of about 1.2 V. A hydrophilic droplet three-electrode system using a single electroactive molecule instead of a redox couple has been confirmed to be stable and has similar functionality to a redox couple. In addition, the lipophilicity of antiplatelet drug clopidogrel at the W/DCE interface is investigated and its ionic partition diagram has been constructed. Protonated clopidogrel is detected in a linear concentration range of 5.0-50 μM and the limit of detection (LOD) is calculated to be 3.0 μM by using the hydrophilic droplet system Ru(NH3)6(3+/2+) and OSWV.

Electrochemical label-free and reagentless genosensor based on an ion barrier switch-off system for DNA sequence-specific detection of the avian influenza virus.

This paper concerns the development of genosensors based on redox-active monolayers incorporating (dipyrromethene)2Cu(II) and (dipyrromethene)2Co(II) complexes formed step by step on a gold electrode surface. They were applied for electrochemical determination of oligonucleotide sequences related to avian influenza virus (AIV) type H5N1. A 20-mer probe (NH2-NC3) was covalently attached to the gold electrode surface via a reaction performed in the presence of ethyl(dimethylaminopropyl)carbodiimide / N-hydroxysuccinimide (EDC/NHS) between the amine group present in the probe and carboxylic groups present on the surface of the redox-active layer. Each modification step has been controlled with Osteryoung square-wave voltammetry. The genosensor incorporating the (dipyrromethene)2Cu(II) complex was able to detect a fully complementary single-stranded DNA target with a detection limit of 1.39 pM. A linear dynamic range was observed from 1 to 10 pM. This genosensor displays good discrimination between three single-stranded DNA targets studied: fully complementary, partially complementary (with only six complementary bases), and totally noncomplementary to the probe. When the (dipyrromethene)2Co(II) complex was applied, a detection limit of 1.28 pM for the fully complementary target was obtained. However, this genosensor was not able to discriminate partially complementary and totally noncomplementary oligonucleotide sequences to the probe. Electrochemical measurements, using both types of genosensors in the presence of different supporting electrolytes, were performed in order to elaborate a new mechanism of analytical signal generation based on an ion barrier "switch-off" system.

New redox-active layer create via epoxy–amine reaction – The base of genosensor for the detection of specific DNA and RNA sequences of avian influenza virus H5N1

This paper concerns the development of a redox-active monolayer and its application for the construction of an electrochemical genosensor designed for the detection of specific DNA and RNA oligonucleotide sequences related to the avian influenza virus (AIV) type H5N1. This new redox layer was created on a gold electrode surface step by step. Cyclic Voltammetry, Osteryoung Square-Wave Voltammetry and Differential Pulse Voltammetry were used for its characterization. This new redox-active layer was applied for the construction of the DNA biosensor. The NH2-NC3 probe (20-mer) was covalently attached to the gold electrode surface via a “click” reaction between the amine and an epoxide group. The hybridization process was monitored using the Osteryoung Square-Wave Voltammetry. The 20-mer DNA and ca. 280-mer RNA oligonucleotides were used as the targets. The constructed genosensor was capable to determine complementary oligonucleotide sequences with a detection limit in the pM range. It is able to distinguish the different position of the part RNA complementary to the DNA probe. The genosensor was very selective. The 20-mer DNA as well as the 280-mer RNA oligonucleotides without a complementary sequence generated a weak signal.

Graphene nanodots-encaged porous gold electrode fabricated via ion beam sputtering deposition for electrochemical analysis of heavy metal ions

A graphene nanodots-encaged porous gold electrode via ion beam sputtering deposition (IBSD) for electrochemical sensing is presented. The electrodes were fabricated using Au target, and a composite target of Al and graphene, which were simultaneously sputtered onto glass substrates by Ar ion beam, followed with hydrochloric acid corrosion. The as-prepared graphene nanodots-encaged porous gold electrodes were then used for the analysis of heavy metal ions, e.g. Cu2+ and Pb2+ by Osteryoung square wave voltammetry (OSWV). These porous electrodes exhibited enhanced detection range for the heavy metal ions due to the entrapped graphene nanodots in 3-D porous structure. In addition, it was also found that when the thickness of porous electrode reached 40nm the detection sensitivity came into saturation. The linear detection range is 0.009–4μM for Cu2+ and 0.006–2.5μM for Pb2+. Good reusability and repeatability were also observed. The formation mechanism and 3-D structure of the porous electrode were also investigated using scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectra (XPS). This graphene entrapped 3-D porous structure may envision promising applications in sensing devices.

Voltammetric detection of S100B protein using His-tagged receptor domains for advanced glycation end products (RAGE) immobilized onto a gold electrode surface.

In this work we report on an electrochemical biosensor for the determination of the S100B protein. The His-tagged VC1 domains of Receptors for Advanced Glycation End (RAGE) products used as analytically active molecules were covalently immobilized on a monolayer of a thiol derivative of pentetic acid (DPTA) complex with Cu(II) deposited on a gold electrode surface. The recognition processes between the RAGE VC1 domain and the S100B protein results in changes in the redox activity of the DPTA-Cu(II) centres which were measured by Osteryoung square-wave voltammetry (OSWV). In order to verify whether the observed analytical signal originates from the recognition process between the His6–RAGE VC1 domains and the S100B protein, the electrode modified with the His6–RAGE C2 and His6–RAGE VC1 deleted domains which have no ability to bind S100B peptides were applied. The proposed biosensor was quite sensitive, with a detection limit of 0.52 pM recorded in the buffer solution. The presence of diluted human plasma and 10 nM Aβ1-40 have no influence on the biosensor performance.

Nitrilotriacetic Acid–Copper(II) Monolayer Deposited on a Gold Electrode for the Immobilization of Histidine Tagged V Domain of Receptor for Advanced Glycation End Products–The Basis of Amyloid–Beta Peptide Sensing

The preparation and application of biosensors for the determination of amyloid-beta16–23′ peptide are described. The redox active nitrilotriacetic acidsingle-copper(II)-histidine6-receptor for advanced glycation end products V domain and redox active nitrilotriacetic aciddouble-Cu(II)-histidine6-receptor for advanced glycation end products V domain complexes were employed as an analytically active layer of biosensors. The preparation procedure consists of three steps: creation of a mixed layer composed of N-acetylocysteamine and thiol derivatives of nitrilotriacetic acid, complexation of Cu(II) on the N-acetylocysteamine-nitrilotriacetic acid layer, and immobilization of histidine-tagged V domains, natural or mutant on the surface of a gold electrode modified with a N-acetylocysteamine-nitrilotriacetic acid layer. The biosensors were used for the study of the interactions between the histidine-tagged V domains of receptor for advanced glycation end products and amyloid-beta16–23′ peptide. Each step was controlled by cyclic voltammetry, Osteryoung square-wave voltammetry, and atomic force microscopy. Comparisons of the electrochemical parameters of biosensors, incorporating single as well as double nitrilotriacetic acid molecules, were investigated. Both types of biosensors were used for determination of amyloid-beta16–23′ peptide, and the mechanism of electroanalytical signals generation is reported.

On the Oxidation of the Three‐Dimensional Aromatics [B12X12]2− (X=F, Cl, Br, I)

The perhalogenated closo-dodecaborate dianions [B12 X12 ](2-) (X=H, F, Cl, Br, I) are three-dimensional counterparts to the two-dimensional aromatics C6 X6 (X=H, F, Cl, Br, I). Whereas oxidation of the parent compounds [B12 H12 ](2-) and benzene does not lead to isolable radicals, the perhalogenated analogues can be oxidized by chemical or electrochemical methods to give stable radicals. The chemical oxidation of the closo-dodecaborate dianions [B12 X12 ](2-) with the strong oxidizer AsF5 in liquid sulfur dioxide (lSO2 ) yielded the corresponding radical anions [B12 X12 ](⋅-) (X=F, Cl, Br). The presence of radical ions was proven by EPR and UV/Vis spectroscopy and supported by quantum chemical calculations. Use of an excess amount of the oxidizing agent allowed the synthesis of the neutral perhalogenated hypercloso-boranes B12 X12 (X=Cl, Br). These compounds were characterized by single-crystal X-ray diffraction of dark blue B12 Cl12 and [Na(SO2 )6 ][B12 Br12 ]⋅B12 Br12 . Sublimation of the crude reaction products that contained B12 X12 (X=Cl, Br) resulted in pure dark blue B12 Cl12 or decomposition to red B9 Br9 , respectively. The energetics of the oxidation processes in the gas phase were calculated by DFT methods at the PBE0/def2-TZVPP level of theory. They revealed the trend of increasing ionization potentials of the [B12 X12 ](2-) dianions by going from fluorine to bromine as halogen substituent. The oxidation of all [B12 X12 ](2-) dianions was also studied in the gas phase by mass spectrometry in an ion trap. The electrochemical oxidation of the closo-dodecaborate dianions [B12 X12 ](2-) (X=F, Cl, Br, I) by cyclic and Osteryoung square-wave voltammetry in liquid sulfur dioxide or acetonitrile showed very good agreement with quantum chemical calculations in the gas phase. For [B12 X12 ](2-) (X=F, Cl, Br) the first and second oxidation processes are detected. Whereas the first process is quasi-reversible (with oxidation potentials in the range between +1.68 and +2.29 V (lSO2 , versus ferrocene/ferrocenium (Fc(0/+) ))), the second process is irreversible (with oxidation potentials ranging from +2.63 to +2.71 V (lSO2 , versus Fc(0/+) )). [B12 I12 ](2-) showed a complex oxidation behavior in cyclic voltammetry experiments, presumably owing to decomposition of the cluster anion under release of iodide, which also explains the failure to isolate the respective radical by chemical oxidation.

Single Electrode Genosensor for Simultaneous Determination of Sequences Encoding Hemagglutinin and Neuraminidase of Avian Influenza Virus Type H5N1

The duo-genosensor consisting of two different oligonucleotide probes immobilized covalently on the surface of one gold electrode via Au-S bond formation was used for simultaneous determination of two different oligonucleotide targets. One of the probes, decorated on its 5'-end with ferrocene (SH-ssDNA-Fc), is complementary to the cDNA representing a sequence encoding part of H5 hemagglutinin from H5N1 virus. The second probe, decorated on its 5'-end with methylene blue (SH-ssDNA-MB), is complementary to cDNA representing the fragment of N1 neuraminidase from the same virus. The presence of both probes on the surface of gold electrodes was confirmed with Osteryoung square-wave voltammetry (OSWV). The changes in redox activity of both redox active complexes before and after the hybridization process were used as analytical signal. The peak at +400 ± 2 mV was observed in the presence of 40 nM ssDNA used as a target for SH-ssDNA-Fc probe. This peak increased with the increase of concentration of target ssDNA. It indicates the "signal on" mode of analytical signal generation. The peak at -250 ± 4 mV, characteristic for SH-ssDNA-MB probe, was decreasing with the increase of the concentration of the complementary ssDNA target starting from 8 to 100 nM. This indicates the generation of electrochemical signal according to the "signal off" mode. The proposed duo-genosensor is capable of simultaneous, specific, and good sensitivity probing for the sequences derived from genes encoding two main markers of the influenza virus, hemagglutinin and neuraminidase.

Oriented Immobilization of His-Tagged Protein on a Redox Active Thiol Derivative of DPTA-Cu(II) Layer Deposited on a Gold Electrode—The Base of Electrochemical Biosensors

This paper concerns the development of an electrochemical biosensor for the determination of Aβ16–23′ and Aβ1–40 peptides. The His-tagged V and VC1 domains of Receptor for Advanced Glycation end Products (RAGE) immobilized on a gold electrode surface were used as analytically active molecules. The immobilization of His6–RAGE domains consists of: (i) formation of a mixed layer of N-acetylcysteamine (NAC) and the thiol derivative of pentetic acid (DPTA); (ii) complexation of Cu(II) by DPTA; (iii) oriented immobilization of His6–RAGE domains via coordination bonds between Cu(II) sites from DPTA–Cu(II) complex and imidazole nitrogen atoms of a histidine tag. Each modification step was controlled by cyclic voltammetry (CV), Osteryoung square-wave voltammetry (OSWV), and atomic force microscopy (AFM). The applicability of the proposed biosensor was tested in the presence of human plasma, which had no influence on its performance. The detection limits for Aβ1–40 determination were 1.06 nM and 0.80 nM, in the presence of buffer and human plasma, respectively. These values reach the concentration level of Aβ1–40 which is relevant for determination of its soluble form in human plasma, as well as in brain. This indicates the promising future application of biosensor presented for early diagnosis of neurodegenerative diseases.

DNA probe modified with 3-iron bis(dicarbollide) for electrochemical determination of DNA sequence of Avian Influenza Virus H5N1

In this work, we report on oligonucleotide probes bearing metallacarborane [3-iron bis(dicarbollide)] redox label, deposited on gold electrode for electrochemical determination of DNA sequence derived from Avian Influenza Virus (AIV), type H5N1. The oligonucleotide probes containing 5'-terminal NH2 group were covalently attached to the electrode, via NHS/EDC coupling to 3-mercaptopropionic acid SAM, previously deposited on the surface of gold. The changes in redox activity of Fe(III) centre of the metallacarborane complex before and after hybridization process was used as analytical signal. The signals generated upon hybridization with targets such as complementary or non-complementary 20-mer ssDNA or various PCR products consisting of 180–190bp (dsDNA) were recorded by Osteryoung square-wave voltammetry (OSWV). The developed system was very sensitive towards targets containing sequence complementary to the probe with the detection limit estimated as 0.03fM (S/N=3.0) and 0.08fM (S/N=3.0) for 20-mer ssDNA and for dsDNA (PCR product), respectively. The non-complementary targets generated very weak responses. Furthermore, the proposed genosensor was suitable for discrimination of PCR products with different location of the complementarity region.

Redox Active DipyrrometheneCu(II) Monolayer for Oriented Immobilization of His‐Tagged RAGE Domains – the Base of Electrochemical Biosensor for Determination of Aβ16–23′

AbstractThe new system which consists of the thiol derivative of dipyrromethene–Cu(II) complex created on the surface of a gold electrode was applied for the first time for oriented immobilization of selected His‐tagged domains of a receptor for advanced glycation endproducts (RAGE). Cyclic voltammetry (CV), Osteryoung square‐wave voltammetry (OSWV), electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM) were used for characterization of the redox active sensing layer. The biosensor proposed was applied for determination of Aβ16–23′ peptide. In its presence, a decrease of the maximum Cu(II) redox current was observed. These values correlated linearly with the Aβ16–23′ concentration in the range 0.001–1.000 µM. The presence of diluted human plasma has no influence on the sensor responses.

Electrochemical detection of C60−4 and C60−5 species coordinated to Vaska's catalyst

Abstract The tetraanionic [60]fulleride– and pentaanionic [60]fulleride–Vaska's complexes, detected electrochemically in acetonitrile/toluene solutions, are produced after the appearance of C60's forth reduction wave in cyclic voltammetry (CV) and Osteryoung square wave voltammetry (OSWV) experiments. The observation that C60's forth reduction wave becomes quasi irreversible suggests that tetraanionic [60]fulleride/CH3CN exchange on acetonitrile–Vaska's complex partially depletes the [60]fulleride tetraanion. Whether the pentaanionic [60]fulleride–Vaska's complex is produced from tetraanion-C60/CH3CN and/or pentaanion-C60/tetraanion-C60 exchange on CH3CN Vaska's complex and tetraanion-[60]fulleride–Vaska's complex, respectively, or by electrochemical reduction of the tetraanion-[60]fulleride–Vaska's complex is a query that will be addressed in a future investigation.