Refine
Year of publication
Document Type
- Article (123)
- Postprint (4)
- Monograph/Edited Volume (1)
- Part of a Book (1)
- Doctoral Thesis (1)
Keywords
- Bioelectrocatalysis (5)
- Direct electron transfer (5)
- Biosensors (4)
- bioelectrocatalysis (4)
- Aldehyde oxidoreductase (3)
- Biosensor (3)
- Cytochrome P450 (3)
- Nanoparticles (3)
- electron transfer (3)
- hydrogen peroxide (3)
- Biofuel cell (2)
- Electron transfer (2)
- Human sulfite oxidase (2)
- cytochrome c (2)
- direct electron transfer (2)
- molecularly imprinted polymers (2)
- p-Aminophenol (2)
- self-assembled monolayer (2)
- 4-Fluoroaniline (1)
- ATP (1)
- Agrocybe aegerita peroxygenase (1)
- Alkaline phosphatase (1)
- Amperometric sensor (1)
- Aniline (1)
- Aniline biosensor (1)
- Antimony doped tin dioxide (1)
- Aromatic aldehydes (1)
- Au nanoparticles (1)
- Benzaldehyde (1)
- Bilirubin oxidase (1)
- Biocatalysis (1)
- Bioinformatic (1)
- Biomarker (1)
- Biosensor array (1)
- CNTs-based screen printed electrodes (1)
- Catalytically active molecularly imprinted polymers (1)
- Catechol (1)
- CdS quantum dots (1)
- Cellobiose dehydrogenase (1)
- Chemometrics (1)
- Cyclic voltammetry (1)
- Cytochrome c (1)
- Dehydrogenase (1)
- Direct electrochemistry (1)
- Electrochemical measurements (1)
- Electrochemical switch (1)
- Electronic tongue (1)
- Enzymatic fuel cell (1)
- Enzymatic recycling (1)
- Enzyme catalysis (1)
- Enzyme electrode (1)
- External stimuli (1)
- Gold nanoparticle (1)
- HTHP (1)
- Hexokinase (1)
- Hydrogen peroxide (1)
- Immobilization (1)
- Indium tin oxide (1)
- Indium tin oxide nanoparticles (1)
- Ionic liquid (1)
- Metalloenzymes (1)
- Microbial electrochemistry (1)
- Microperoxidase (1)
- Microperoxidase-11 (1)
- Microperoxidases (1)
- Microscale electrode (1)
- Modified electrode (1)
- Molecularly imprinted polymers (1)
- Molybdenum cofactor (1)
- Molybdoenzymes (1)
- Multi-cofactor enzymes (1)
- Multivariate data analysis (1)
- Multiwalled carbon nanotube (1)
- N-omega-hydroxy-L-arginine (1)
- Nanohybrid (1)
- Nicotinamide (1)
- Nitric oxide synthase (1)
- Optical device (1)
- Osmium (1)
- Osteoblast (1)
- Pathogenic detection (1)
- Peroxidatic activity (1)
- Personalised medicine (1)
- Personalized medicine (1)
- Phenolic compounds (1)
- Phenolic substances (1)
- Phenothiazine (1)
- Poylaniline (1)
- Probing living Staphylococcus aureus (1)
- Protein interaction (1)
- Protein voltammetry (1)
- Pyruvate kinase (1)
- Redox polymer (1)
- Screen-printed electrode (1)
- Self-powered biosensor (1)
- Solvation (1)
- Substrate binding (1)
- Sulfite biosensor (1)
- Sulfite oxidase (1)
- Sulphite oxidase (1)
- Superoxide (1)
- Tetrahydrobiopterin (1)
- Third generation sensor (1)
- Toxicity (1)
- Unspecific peroxygenase (1)
- Voltammetry (1)
- Wastewater (1)
- amperometry (1)
- bioelectrochemistry (1)
- biosensor (1)
- biosensors (1)
- cellobiose dehydrogenase (1)
- cobalt porphyrin (1)
- dendritic (1)
- device (1)
- direct electrochemistry (1)
- electrochemistry (1)
- electrode (1)
- enzyme catalysis (1)
- heme proteins (1)
- horseradish peroxidase (1)
- human sulfite oxidase (1)
- hydrogel (1)
- immobilization (1)
- impedance spectroscopy (1)
- indium tin oxide ITO (1)
- mesoporous materials (1)
- microelectrode (1)
- microfluidics (1)
- molecular modeling (1)
- monolayers (1)
- multichannel potentiostat (1)
- multilayer (1)
- oxygen reduction reaction (1)
- pH responsive hydrogel (1)
- photocurrent (1)
- polymer-modified electrode (1)
- reactive oxygen species (1)
- scanning electrochemical microscopy (1)
- spectroelectrochemistry (1)
- stem cell monitoring (1)
- sulfite (1)
- sulfite oxidase (1)
- surface-enhanced vibrational spectroscopy (1)
Phenothiazine-modified redox hydrogels were synthesized and used for the wiring of the aldehyde oxidoreductase PaoABC to electrode surfaces. The effects of the pH value and electrode surface modification on the biocatalytic activity of the layers were studied in the presence of vanillin as the substrate. The enzyme electrodes were successfully employed as bioanodes in vanillin/O-2 biofuel cells in combination with a high potential bilirubin oxidase biocathode. Open circuit voltages of around 700 mV could be obtained in a two compartment biofuel cell setup. Moreover, the use of a rather hydrophobic polymer with a high degree of crosslinking sites ensures the formation of stable polymer/enzyme films which were successfully used as bioanode in membrane-less biofuel cells. (C) 2015 Elsevier B.V. All rights reserved.
Ultrasensitive biosensors
(1996)
Electrochemical investigations of the blood oxygen carrier protein include both mediated and direct electron transfer. The reaction of haemoglobin (Hb) with typical mediators, e.g., ferricyanide, can be quantified by measuring the produced ferrocyanide which is equivalent to the Hb concentration. Immobilization of the mediator within the electrode body allows reagentless electrochemical measuring of Hb. On the other hand, entrapment of the protein within layers of polyclectrolytes, lipids, nanoparticles of clay or gold leads to a fast heterogeneous electron exchange of the partially denatured Hb. (c) 2005 Elsevier B.V. All rights reserved
For the first time the direct electron transfer of an enzyme - cellobiose dehydrogenase, CDH - has been coupled with the hexokinase catalyzed competition for glucose in a sensor for ATP. To enhance the signal output for ATP, pyruvate kinase was coimmobilized to recycle ADP by the phosphoenolpyruvate driven reaction. The new sensor overcomes the limit of 1:1 stoichiometry of the sequential or competitive conversion of ATP by effective enzymatic recycling of the analyte. The anodic oxidation of the glucose converting CDH proceeds at electrode potentials below 0 mV vs. Ag vertical bar AgCl thus potentially interfering substances like ascorbic acid or catecholamines do not influence the measuring signal. The combination of direct electron transfer of CDH with the enzymatic recycling results in an interference-free and oxygen-independent measurement of ATP in the lower mu molar concentration range with a lower limit of detection of 63.3 nM (S/N=3).
The Electrically Wired Molybdenum Domain of Human Sulfite Oxidase is Bioelectrocatalytically Active
(2015)
We report electron transfer between the catalytic molybdenum cofactor (Moco) domain of human sulfite oxidase (hSO) and electrodes through a poly(vinylpyridine)-bound [osmium(N,N'-methyl-2,2'-biimidazole)(3)](2+/3+) complex as the electron-transfer mediator. The biocatalyst was immobilized in this low-potential redox polymer on a carbon electrode. Upon the addition of sulfite to the immobilized separate Moco domain, the generation of a significant catalytic current demonstrated that the catalytic center is effectively wired and active. The bioelectrocatalytic current of the wired separate catalytic domain reached 25% of the signal of the wired full molybdoheme enzyme hSO, in which the heme b(5) is involved in the electron-transfer pathway. This is the first report on a catalytically active wired molybdenum cofactor domain. The formal potential of this electrochemical mediator is between the potentials of the two cofactors of hSO, and as hSO can occupy several conformations in the polymer matrix, it is imaginable that electron transfer from the catalytic site to the electrode through the osmium center occurs for the hSO molecules in which the Moco domain is sufficiently accessible. The observation of catalytic oxidation currents at low potentials is favorable for applications in bioelectronic devices.
The aromatic peroxygenase (APO; EC 1.11.2.1) from the agraric basidomycete Marasmius rotula (MroAPO) immobilized at the chitosan-capped gold-nanoparticle-modified glassy carbon electrode displayed a pair of redox peaks with a midpoint potential of -278.5 mV vs. AgCl/AgCl (1 M KCl) for the Fe(2+)/Fe(3+) redox couple of the heme-thiolate-containing protein. MroAPO oxidizes aromatic substrates such as aniline, p-aminophenol, hydroquinone, resorcinol, catechol, and paracetamol by means of hydrogen peroxide. The substrate spectrum overlaps with those of cytochrome P450s and plant peroxidases which are relevant in environmental analysis and drug monitoring. In M. rotula peroxygenase-based enzyme electrodes, the signal is generated by the reduction of electrode-active reaction products (e.g., p-benzoquinone and p-quinoneimine) with electro-enzymatic recycling of the analyte. In these enzyme electrodes, the signal reflects the conversion of all substrates thus representing an overall parameter in complex media. The performance of these sensors and their further development are discussed.
Surface-Tuned Electron Transfer and Electrocatalysis of Hexameric Tyrosine-Coordinated Heme Protein
(2015)
Molecular modeling, electrochemical methods, and quartz crystal microbalance were used to characterize immobilized hexameric tyrosine-coordinated heme protein (HTHP) on bare carbon or on gold electrodes modified with positively and negatively charged self-assembled monolayers (SAMs), respectively. HTHP binds to the positively charged surface but no direct electron transfer (DET) is found due to the long distance of the active sites from the electrode surfaces. At carboxyl-terminated surfaces, the neutrally charged bottom of HTHP can bind to the SAM. For this "disc" orientation all six hemes are close to the electrode and their direct electron transfer should be efficient. HTHP on all negatively charged SAMs showed a quasi-reversible redox behavior with rate constant k(s) values between 0.93 and 2.86 s(-1) and apparent formal potentials E-app(0)' between -131.1 and -249.1 mV. On the MUA/MU-modified electrode, the maximum surface concentration corresponds to a complete monolayer of the hexameric HTHP in the disc orientation. HTHP electrostatically immobilized on negatively charged SAMs shows electrocatalysis of peroxide reduction and enzymatic oxidation of NADH.
Surface modification with thermoresponsive polymer brushes for a switchable electrochemical sensor
(2014)
Elaboration of switchable surfaces represents an interesting way for the development of a new generation of electrochemical sensors. In this paper, a method for growing thermoresponsive polymer brushes from a gold surface pre-modified with polyethyleneimine (PEI), subsequent layer-by-layer polyelectrolyte assembly and adsorption of a charged macroinitiator is described. We propose an easy method for monitoring the coil-to-globule phase transition of the polymer brush using an electrochemical quartz crystal microbalance with dissipation (E-QCM-D). The surface of these polymer modified electrodes shows reversible switching from the swollen to the collapsed state with temperature. As demonstrated from E-QCM-D measurements using an original signal processing method, the switch is operating in three reversible steps related to different interfacial viscosities. Moreover, it is shown that the one electron oxidation of ferrocene carboxylic acid is dramatically affected by the change from the swollen to the collapsed state of the polymer brush, showing a spectacular 86% decrease of the charge transfer resistance between the two states.
Surface modification with thermoresponsive polymer brushes for a switchable electrochemical sensor
(2014)
Elaboration of switchable surfaces represents an interesting way for the development of a new generation of electrochemical sensors. In this paper, a method for growing thermoresponsive polymer brushes from a gold surface pre-modified with polyethyleneimine (PEI), subsequent layer-by-layer polyelectrolyte assembly and adsorption of a charged macroinitiator is described. We propose an easy method for monitoring the coil-to-globule phase transition of the polymer brush using an electrochemical quartz crystal microbalance with dissipation (E-QCM-D). The surface of these polymer modified electrodes shows reversible switching from the swollen to the collapsed state with temperature. As demonstrated from E-QCM-D measurements using an original signal processing method, the switch is operating in three reversible steps related to different interfacial viscosities. Moreover, it is shown that the one electron oxidation of ferrocene carboxylic acid is dramatically affected by the change from the swollen to the collapsed state of the polymer brush, showing a spectacular 86% decrease of the charge transfer resistance between the two states.
A biosensor, based on a redoxactive osmium polymer and sulfite oxidase on screen-printed electrodes, is presented here as a promising method for the detection of sulfite. A catalytic oxidative current was generated when a sample containing sulfite was pumped over the carbon screen-printed electrode modified with osmium redox polymer wired sulfite oxidase. A stationary value was reached after approximately 50 s and a complete measurement lasted no more than 3 min. The electrode polarized at -0.1 V (vs. Ag vertical bar AgCl 1M KCl) permits minimizing the influence of interfering substances, since these compounds can be unspecific oxidized at higher potentials. Because of the good stability of the protein film on the electrode surface, a well functioning biosensor-flow system was possible to construct. The working stability and reproducibility were further enhanced by the addition of bovine serum albumin generating a more long-term stable and biocompatible protein environment. The optimized biosensor showed a stable signal for more than a week of operation and a coefficient of variation of 4.8% for 12 successive measurements. The lower limit of detection of the sensor was 0.5 mu M sulfite and the response was linear until 100 mu M. The high sensitivity permitted a 1:500 dilution of wine samples. The immobilization procedure and the operational conditions granted minimized interferences. Additionally, repeating the immobilization procedure to form several layers of wired SO further increased the sensitivity of such a sensor. Finally. the applicability of the developed sulfite biosensor was tested on real samples, such as white and red wines.
Cellobiose dehydrogenase catalyzes the oxidation of various carbohydrates and is considered as a possible anode catalyst in biofuel cells. It has been shown that the catalytic performance of this enzyme immobilized on electrodes can be increased by presence of calcium ions. To get insight into the Ca2+-induced changes in the immobilized enzyme we employ surface-enhanced vibrational (SERR and SEIRA) spectroscopy together with electrochemistry. Upon addition of Ca2+ ions electrochemical measurements show a shift of the catalytic turnover signal to more negative potentials while SERR measurements reveal an offset between the potential of heme reduction and catalytic current. Comparing SERR and SEIRA data we propose that binding of Ca2+ to the heme induces protein reorientation in a way that the electron transfer pathway of the catalytic FAD center to the electrode can bypass the heme cofactor, resulting in catalytic activity at more negative potentials.
The spectroelectrochemistry of camphor-bound cytochrome P450cam (P450cam) using gold electrodes is described. The electrodes were modified with either 4,4'-dithiodipyridin or sodium dithionite. Electrolysis of P450cam was carried out when the enzyme was in solution, while at the same time UV visible absorption spectra were recorded. Reversible oxidation and reduction could be observed with both 4,4'-dithiodipyridin and dithionite modified electrodes. A formal potential (E-0') of -373 mV vs Ag/AgCl 1 M KCl was determined. The spectra of P450cam complexed with either carbon monoxide or metyrapone, both being inhibitors of P450 catalysis, clearly indicated that the protein retained its native state in the electrochemical cell during electrolysis. (C) 2003 Elsevier Inc. All rights reserved
A novel electrochemical immunoassay based on the multiple affinity labeling of the indicator antibody with an electro-active tag is presented. The concept is illustrated for the determination of the glycated hemoglobin HbA1c in hemoglobin samples. Hemoglobin is adsorbed to the surfactant-modified surface of a piezoelectric quartz crystal. Whereas the quartz crystal nanobalance is used to validate the total Hb binding, the HbA1c on the sensor surface is recognized by an antibody and quantified electrochemically after the sugar moieties of the antibody have been labeled in-situ with ferroceneboronic acid. The sensitivity of this sensor is about threefold higher than the sensitivity of a hemoglobin sensor, where the ferroceneboronic acid is bound directly to HbA1c.
Cytochrome P450 enzymes (CYPs) act on more than 90 percent of all drugs currently on the market. The catalytic cycle requires electron supply to the heme iron in the presence of oxygen. Electrochemistry allows to characterise the reaction mechanism of these redox enzymes by observing the electron transfer in real time. According to the number of publications on protein electrochemistry CYP has the third position after glucose oxidase and cytochrome c. CYP based enzyme electrodes for the quantification of drugs, metabolites or pesticides have been developed using different iso-enzymes. A crucial step in the sensor development is the efficiency of coupling the biocatalytic systems with the electrode is. In the 1970s the direct electron transfer of heme and heme peptides called microperoxidases (MPs) was used as model of oxidoreductases. They exhibit a broad substrate spectrum including hydroxylation of selected aromatic substrates, demethylation and epoxidation by means of hydrogen peroxide. It overlaps with that of P450 making heme and MPs to alternate recognition elements in biosensors for the detection of typical CYP substrates. In these enzyme electrodes the signal is generated by the conversion of all substrates thus representing in complex media an overall parameter. By combining the biocatalytic substrate conversion with selective binding to a molecularly imprinted polymer layer the specificity has been improved. Here we discuss different approaches of biosensors based on CYP, microperoxidases and catalytically active MIPs and discuss their potential as recognition elements in biosensors. The performance of these sensors and their further development are discussed. (C) 2013 Elsevier Ltd. All rights reserved.