Voltammetric Sensing of Chloride Based on a Redox-Active Complex: A Terpyridine-Co(II)-Dipyrromethene Functionalized Anion Receptor Deposited on a Gold Electrode.

A redox-active complex containing Co(II) connected to a terpyridine (TPY) and dipyrromethene functionalized anion receptor (DPM-AR) was created on a gold electrode surface. This host-guest supramolecular system based on a redox-active layer was used for voltammetric detection of chloride anions in aqueous solutions. The sensing mechanism was based on the changes in the redox activity of the complex observed upon binding of the anion to the receptor.

Silver or gold? A comparison of nanoparticle modified electrochemical genosensors based on cobalt porphyrin-DNA.

We applied a cobalt-porphyrin modified DNA as electrochemical marker, which was attached to nanoparticles, to detect specific DNA sequences. We compare the performance of gold and silver NPs in oligonucleotide sensors to determine if a change in metal will lead to either higher sensitivity or different selectivity, based on the redox behaviour of silver vs. gold.

Immunosensor incorporating half-antibody fragment for electrochemical monitoring of amyloid-β fibrils in artificial blood plasma.

In this report, an electrochemical immunosensor for the selective and sensitive monitoring of Aβ fibrils is presented. The sensing platform was prepared by the formation of a 4,4'-thiobisbenzenethiol (TBBT) self-assembled monolayer on a clean gold surface followed by the covalent entrapment of gold nanoparticles (AuNPs). The half-antibody fragments of the Anti-Amyloid Fibrils antibody were immobilized on AuNPs via S-Au covalent bonds.

Simple and Cost-effective "Turn-on" Fluorescence Sensor for the Determination of Xanthine.

A simple and selective 'turn-on' fluorescence sensor have been developed for the determination of xanthine (XA) based on glutathione (GSH) capped copper nanoclusters (CuNCs) as the fluorescent probe. The proposed sensor possess several advantages such as sensitivity, short analysis time and requires no sample pretreatment. The conditions for the performances of the sensor have been optimized and good linear relationship was obtained between concentration and relative fluorescence intensity in the concentration range 9.

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-M-terpyridine and asymmetric dipyrromethene-M-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.

Ultrasensitive electrochemical genosensor for direct detection of specific RNA sequences derived from avian influenza viruses present in biological samples.

An electrochemical genosensor based on an epoxy-phenanthroline-Fe(III)-NH2-ssDNA layer for the detection of RNA derived from Avian Influenza is presented. The biosensor preparation consists of: (I) modification of gold electrodes with aminoethanethiol, (II) modification of the self-assembled monolayer of aminoethanethiol with 5,6-epoxy-5,6-dihydro-[1,10]-phenanthroline using "click" chemistry, (III) a first step of complexation of Fe(III) by 5,6-epoxy-5,6-dihydro-[1,10]-phenanthroline, (IV) a second step of complexation of Fe(III) by 5,6-epoxy-5,6-dihydro-[1,10]-phenanthroline, (V) immobilization of the single stranded amino-DNA probe via "click" chemistry between epoxy and amino groups. The interactions between the ssDNA probe and RNA targets were explored with Osteryoung Square Wave Voltammetry.

Copper nanoclusters: an efficient fluorescence sensing platform for quinoline yellow.

Fluorescence quenching behavior of artificial food colorant quinoline yellow (QY), on interaction with l-cysteine stabilized copper nanoclusters (l-Cys-CuNCs) is investigated in this work. For this purpose, l-cysteine stabilized CuNCs were synthesized and characterized using various analytical techniques. Results demonstrated that the synthesized probe (size ~2 nm) had very promising optical features such as bright blue fluorescence, significant quantum yield and excellent photostability.

Highly sensitive electrochemical biosensor based on redox - active monolayer for detection of anti-hemagglutinin antibodies against swine-origin influenza virus H1N1 in sera of vaccinated mice.

Background: In this work, we report an electrochemical biosensor for the detection of anti-hemagglutinin antibodies against the swine virus H1N1 present in mice sera immunized with mixture of His-H1 HA in monomeric and oligomeric form. The oriented immobilization of the recombinant His-tagged hemagglutinin (His-H1 HA) consists of: (i) formation of a mixed layer of 4-mercaptobutanol (MBT) and the thiol derivative of dipyrromethene (DPM); (ii) complexation of Cu (II) by DPM; (iii) immobilization of His-H1 HA via coordination bonds between Cu (II) sites from DPM-Cu (II) complex and imidazole nitrogen atoms of a histidine tag; (iv) filling free spaces with bovine serum albumin. The interactions between recombinant His- H1 HA covalently attached to the electrode surface and the anti-hemagglutinin H1 antibodies present in mice sera were explored with Osteryoung square-wave voltammetry.

Approaching single DNA molecule detection with an ultrasensitive electrochemical genosensor based on gold nanoparticles and cobalt-porphyrin DNA conjugates.

We describe an ultrasensitive electrochemical genosensor based on gold nanoparticles and cobalt-porphyrin functionalised ssDNA probes. The sensitivity at the attomolar concentration level arises from an increased density of redox labels on the electrode surface compared to sensors without NP modification. The electrode detects as few as 23 DNA molecules, approaching single molecule detection.

Highly Sensitive Electrochemical Sensor for the Detection of Anions in Water Based on a Redox-Active Monolayer Incorporating an Anion Receptor.

In the present work, gold electrodes were modified using a redox-active layer based on dipyrromethene complexes with Cu(II) or Co(II) and a dipodal anion receptor functionalized with dipyrromethene. These modified gold electrodes were then applied for the electrochemical detection of anions (Cl, SO, and Br) in a highly diluted water solution (in the picomolar range). The results showed that both systems, incorporating Cu(II) as well as Co(II) redox centers, exhibited highest sensitivity toward Cl.

Gold Electrodes Modified with Calix[4]arene for Electrochemical Determination of Dopamine in the Presence of Selected Neurotransmitters.

Here, we present an electrochemical sensor based on gold electrodes modified with calix[4]arene functionalized with carboxypiperidino groups at the upper rim. It has been demonstrated that these groups are involved in a complex formation with dopamine (DA) on the surface of gold electrodes. The supramolecular complex calix[4]arene-DA created on the gold electrode surface has been characterized electrochemically and the measuring conditions have been optimized.

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.

A biosensor based on electroactive dipyrromethene-Cu(II) layer deposited onto gold electrodes for the detection of antibodies against avian influenza virus type H5N1 in hen sera.

This paper describes the development of a biosensor for the detection of anti-hemagglutinin antibodies against the influenza virus hemagglutinin. The steps of biosensor fabrications are as follows: (i) creation of a mixed layer containing the thiol derivative of dipyrromethene and 4-mercapto-1-butanol, (ii) complexation of Cu(II) ions, (iii) oriented immobilization of the recombinant histidine-tagged hemagglutinin, and (iv) filling free spaces with bovine serum albumin. The interactions between recombinants hemagglutinin from the highly pathogenic avian influenza virus type H5N1 and anti-hemagglutinin H5 monoclonal antibodies were explored with Osteryoung square-wave voltammetry.

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.

Ion-channel genosensor for the detection of specific DNA sequences derived from Plum Pox Virus in plant extracts.

A DNA biosensor for detection of specific oligonucleotides sequences of Plum Pox Virus (PPV) in plant extracts and buffer is proposed. The working principles of a genosensor are based on the ion-channel mechanism. The NH2-ssDNA probe was deposited onto a glassy carbon electrode surface to form an amide bond between the carboxyl group of oxidized electrode surface and amino group from ssDNA probe.

Electrochemical biosensors for detection of avian influenza virus--current status and future trends.

Electrochemical biosensors have emerged as reliable analytical devices suitable for pathogen detection. Low cost, small sample requirement and possibility of miniaturization justifies their increasing development. Thus, we report in this review on the state of the art of avian influenza virus detection with genosensors and immunosensors working by an electrochemical mode.

Immobilization of His-tagged kinase JAK2 onto the surface of a plasmon resonance gold disc modified with different copper (II) complexes.

New surface plasmon resonance (SPR) sensing platforms which consists of copper (II) complexes of a pentetic acid thiol ligand (DPTA-Cu(II)) and of a thiol derivative of dipyrromethene (DPM-Cu(II) created on the surface of gold SPR disc were applied to oriented immobilization of His-tagged Janus kinase 2 (GST-His6-JAK2). This method is based on the covalent bond formation between histidine from a His-tag chain of a protein and Cu(II) centres from the complexes. The kinetic and thermodynamic parameters of the oriented immobilization of GST-His6-JAK2 protein to DPTA-Cu(II) and DPM-Cu(II) complexes attached to the Au surface of a SPR disc were discussed.

An immunosensor based on antibody binding fragments attached to gold nanoparticles for the detection of peptides derived from avian influenza hemagglutinin H5.

This paper concerns the development of an immunosensor for detection of peptides derived from avian influenza hemagglutinin H5. Its preparation consists of successive gold electrode modification steps: (i) modification with 1,6-hexanedithiol and gold colloidal nanoparticles; (ii) immobilization of antibody-binding fragments (Fab') of anti-hemagglutinin H5 monoclonal antibodies Mab 6-9-1 via S-Au covalent bonds; and (iii) covering the remaining free space on the electrode surfaces with bovine serum albumin. The interactions between Fab' fragments and hemagglutinin (HA) variants have been explored with electrochemical impedance spectroscopy (EIS) in the presence of [Fe(CN)6](3-/4-) as an electroactive marker.

A highly sensitive electrochemical genosensor based on Co-porphyrin-labelled DNA.

We report the use of Co-porphyrins as electrochemical tags for a highly sensitive and selective genosensor. An avian influenza virus-based DNA sequence characteristic of H5N1 was detected at femtomolar levels from competing non-complementary sequences through hybridisation with the labeled DNA.

Electrochemical immunosensor for detection of antibodies against influenza A virus H5N1 in hen serum.

This paper describes the development of an immunosensor for detection of anti-hemagglutinin antibodies. Its preparation consists of successive modification steps of glassy carbon electrodes: (i) creation of COOH groups, (ii) covalent immobilization of protein A with EDC/NHS coupling reaction, (iii) covering with anti-His IgG monoclonal antibody, (iv) immobilization of the recombinant His-tagged hemagglutinin (His6-H5 HA), (v) filling free space with BSA. The interactions between two variants of recombinant HA (short and long) from highly pathogenic avian influenza virus H5N1 and the anti-H5 HA monoclonal antibody (Mab 6-9-1) have been explored with electrochemical impedance spectroscopy (EIS).

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.

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 Aβ(16-23') and A(β1-40) 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.