Refine
Year of publication
Document Type
- Article (118)
- Postprint (2)
- Monograph/Edited Volume (1)
- Doctoral Thesis (1)
Is part of the Bibliography
- yes (122)
Keywords
- Direct electron transfer (4)
- Aldehyde oxidoreductase (3)
- Bioelectrocatalysis (3)
- Biosensors (3)
- bioelectrocatalysis (3)
- electron transfer (3)
- hydrogen peroxide (3)
- Biofuel cell (2)
- Biosensor (2)
- Cytochrome P450 (2)
- Electron transfer (2)
- Human sulfite oxidase (2)
- Nanoparticles (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)
- 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)
- Catechol (1)
- CdS quantum dots (1)
- Cellobiose dehydrogenase (1)
- Chemometrics (1)
- Cyclic voltammetry (1)
- Cytochrome c (1)
- Dehydrogenase (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)
- Immobilization (1)
- Indium tin oxide (1)
- Indium tin oxide nanoparticles (1)
- Ionic liquid (1)
- Metalloenzymes (1)
- Microbial electrochemistry (1)
- Microperoxidase-11 (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)
- 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)
- Sulphite oxidase (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)
- cytochrome c (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)
- 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)
- surface-enhanced vibrational spectroscopy (1)
Institute
- Institut für Biochemie und Biologie (122) (remove)
The control of bioelectrocatalytic processes by external stimuli for the indirect detection of non-redox active species was achieved using an esterase and a redox enzyme both integrated within a redox hydrogel. The poly( vinyl) imidazole Os(bpy)(2)Cl hydrogel displays pH-responsive properties. The esterase catalysed reaction leads to a local pH decrease causing protonation of imidazole moieties thus increasing hydrogel solvation and mobility of the tethered Os-complexes. This is the key step to enable improved electron transfer between an aldehyde oxidoreductase and the polymer-bound Os-complexes. The off-on switch is further integrated in a biofuel cell system for self-powered signal generation.
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 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.
An electrochemical assay for the indication of the activity of the cell bound differentiation marker alkaline phosphatase (ALP) is proposed using voltammetry on an in-vitro cell culture. The basis of the assay is cultivation of cells on gold microelectrodes in wells of a microplate, catalytic hydrolysis of p-aminophenyl phosphate by ALP and indication of p-aminophenol oxidation by square wave voltammetry (SWV) with the sensors onto which the cells attached. The morphology of the bone marrow stromal cell line (MBA-15) on the electrode surface was investigated and it exhibited in vitro osteogenic characteristics. Since ALP is expressed on the cell surface in early differentiation stage of osteoblastic cells, its activity was followed after different culture times over a period of 144 h by recording repetitive voltammograms at different time points upon addition of the substrate p-aminophenyl phosphate. The ALP activity was estimated from the signal increase related to formation rate of p-aminophenol and the number of cells. The highest value was measured at 120 h, when the cells reached confluence. The results of the electrochemical activity assay are consistent with the colorimetric acquired value from p-nitrophenol formation rate.
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.
The bioelectrocatalytic sulfite oxidation by human sulfite oxidase (hSO) on indium tin oxide (ITO) is reported, which is facilitated by functionalizing of the electrode surface with polyethylenimine (PEI)-entrapped CdS nanoparticles and enzyme. hSO was assembled onto the electrode with a high surface loading of electroactive enzyme. In the presence of sulfite but without additional mediators, a high bioelectrocatalytic current was generated. Reference experiments with only PEI showed direct electron transfer and catalytic activity of hSO, but these were less pronounced. The application of the polyelectrolyte-entrapped quantum dots (QDs) on ITO electrodes provides a compatible surface for enzyme binding with promotion of electron transfer. Variations of the buffer solution conditions, e.g., ionic strength, pH, viscosity, and the effect of oxygen, were studied in order to understand intramolecular and heterogeneous electron transfer from hSO to the electrode. The results are consistent with a model derived for the enzyme by using flash photolysis in solution and spectroelectrochemistry and molecular dynamic simulations of hSO on monolayer-modified gold electrodes. Moreover, for the first time a photoelectrochemical electrode involving immobilized hSO is demonstrated where photoexcitation of the CdS/hSO-modified electrode lead to an enhanced generation of bioelectrocatalytic currents upon sulfite addition. Oxidation starts already at the redox potential of the electron transfer domain of hSO and is greatly increased by application of a small overpotential to the CdS/hSO-modified ITO.
A nanohybrid consisting of poly(3-aminobenzenesulfonic acid-co-aniline) and multiwalled carbon nanotubes [MWCNT-P(ABS-A)]) on a gold electrode was used to immobilize the hexameric tyrosine-coordinated heme protein (HTHP). The enzyme showed direct electron transfer between the heme group of the protein and the nanostructured surface. Desorption of the noncovalently bound heme from the protein could be excluded by control measurements with adsorbed hemin on aminohexanthiol-modified electrodes. The nanostructuring and the optimised charge characteristics resulted in a higher protein coverage as compared with MUA/MU modified electrodes. The adsorbed enzyme shows catalytic activity for the cathodic H2O2 reduction and oxidation of NADH.
Biosensors representing the technological counterpart of living senses have found routine application in amperometric enzyme electrodes for decentralized blood glucose measurement, interaction analysis by surface plasmon resonance in drug development, and to some extent DNA chips for expression analysis and enzyme polymorphisms. These technologies have already reached a highly advanced level and need minor improvement at most. The dream of the "100-dollar' personal genome may come true in the next few years provided that the technological hurdles of nanopore technology or of polymerase-based single molecule sequencing can be overcome. Tailor-made recognition elements for biosensors including membrane-bound enzymes and receptors will be prepared by cell-free protein synthesis. As alternatives for biological recognition elements, molecularly imprinted polymers (MIPs) have been created. They have the potential to substitute antibodies in biosensors and biochips for the measurement of low-molecular-weight substances, proteins, viruses, and living cells. They are more stable than proteins and can be produced in large amounts by chemical synthesis. Integration of nanomaterials, especially of graphene, could lead to new miniaturized biosensors with high sensitivity and ultrafast response. In the future individual therapy will include genetic profiling of isoenzymes and polymorphic forms of drug-metabolizing enzymes especially of the cytochrome P450 family. For defining the pharmacokinetics including the clearance of a given genotype enzyme electrodes will be a useful tool. For decentralized online patient control or the integration into everyday "consumables' such as drinking water, foods, hygienic articles, clothing, or for control of air conditioners in buildings and cars and swimming pools, a new generation of "autonomous' biosensors will emerge.
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).
Downscaling of microfluidic cell culture and detection devices for electrochemical monitoring has mostly focused on miniaturization of the microfluidic chips which are often designed for specific applications and therefore lack functional flexibility. We present a compact microfluidic cell culture and electrochemical analysis platform with in-built fluid handling and detection, enabling complete cell based assays comprising on-line electrode cleaning, sterilization, surface functionalization, cell seeding, cultivation and electrochemical real-time monitoring of cellular dynamics. To demonstrate the versatility and multifunctionality of the platform, we explored amperometric monitoring of intracellular redox activity in yeast (Saccharomyces cerevisiae) and detection of exocytotically released dopamine from rat pheochromocytoma cells (PC12). Electrochemical impedance spectroscopy was used in both applications for monitoring cell sedimentation and adhesion as well as proliferation in the case of PC12 cells. The influence of flow rate on the signal amplitude in the detection of redox metabolism as well as the effect of mechanical stimulation on dopamine release were demonstrated using the programmable fluid handling capability. The here presented platform is aimed at applications utilizing cell based assays, ranging from e.g. monitoring of drug effects in pharmacological studies, characterization of neural stem cell differentiation, and screening of genetically modified microorganisms to environmental monitoring.