@article{SchellerScheller1996, author = {Scheller, Frieder W. and Scheller, A.}, title = {Bi-Enzymelektrode zur Messung von Sorbitol in pharmazeutischen Produkten}, year = {1996}, language = {de} } @article{VijgenboomVijgenboomTeppneretal.2001, author = {Vijgenboom, E. and Vijgenboom, E. and Teppner, A. W. J. W. and Makower, Alexander and Scheller, Frieder W. and Canters, Gerard W. and Wollenberger, Ursula}, title = {Determination of phenolic compounds using recombinant tyrosinanse from Streptomyces antibioticus}, year = {2001}, language = {en} } @article{ButtermeyerPhilippMalletal.2002, author = {Buttermeyer, R. and Philipp, A. W. and Mall, J. W. and Ge, Bixia and Scheller, Frieder W. and Lisdat, Fred}, title = {In vivo measurement of oxygen derived free radicals during reperfusion injury}, year = {2002}, language = {en} } @article{MakWollenbergerSchelleretal.2003, author = {Mak, Karen K. W. and Wollenberger, Ursula and Scheller, Frieder W. and Renneberg, Reinhard}, title = {An amperometric bi-enzyme sensor for determination of formate using cofactor regeneration}, year = {2003}, language = {en} } @article{NiessnerBroekaertEinaxetal.2002, author = {Nießner, Reinhard and Broekaert, J. and Einax, J. W. and Scheller, Frieder W. and St{\"o}cklein, Walter F. M.}, title = {Trendbericht analytische Biochemie 2000/2001}, year = {2002}, language = {de} } @article{BauerEremenkoEhrentreichFoersteretal.1996, author = {Bauer, Christian G. and Eremenko, A. V. and Ehrentreich-F{\"o}rster, Eva and Bier, Frank Fabian and Makower, Alexander and Halsall, H. B. and Heineman, W. R. and Scheller, Frieder W.}, title = {Zeptomole-detecting biosensor for alkaline phosphatase in an electroche mical immunoassay for 2,4- dichlorophenoacetic acid}, year = {1996}, language = {en} } @article{FreaneyMacShaneKeavenyetal.1997, author = {Freaney, R. and MacShane, A. and Keaveny, T. V. and MacKenna, M. and Rabenstein, K. and Scheller, Frieder W. and Pfeiffer, Dorothea and Urban, G. and Moser, I. and Jobst, G. and Manz, A. and Verpoorte, E. and Widmer, M. W. and Diamond, D. and Dempsey, E. and deViteri, F. J. S. and Smyth, M.}, title = {Novel instrumentation for real-time monitoring using miniaturized flow systems with integrated biosensors}, year = {1997}, language = {en} } @article{WelzelKossmehlEngelmannetal.1996, author = {Welzel, H.-P. and Kossmehl, G. and Engelmann, G. and Neumann, B. and Wollenberger, Ursula and Scheller, Frieder W. and Schr{\"o}der, W.}, title = {Reactive groups on polymer covered electrodes, 4. Lactate-oxidase-biosensor based on electrodes modifies by polyphiophene}, year = {1996}, language = {en} } @phdthesis{BenkertSchellerSchoessleretal.2000, author = {Benkert, Alexander and Scheller, Frieder W. and Sch{\"o}ssler, W. and Micheel, Burkhard and Warsinke, Axel}, title = {Size exclusion redox-labeled immunoassay (SERI) : a new format for homogeneous amperometric creatinine determination}, year = {2000}, language = {en} } @article{StoeckleinBehrsingScharteetal.2000, author = {St{\"o}cklein, Walter F. M. and Behrsing, Olaf and Scharte, Gudrun and Micheel, Burkhard and Benkert, Alexander and Sch{\"o}ssler, W. and Warsinke, Axel and Scheller, Frieder W.}, title = {Enzyme kinetic assays with surface plasmon resonance (BIAcore) based on competition between enzyme and creatinine antibody}, year = {2000}, language = {en} } @article{GajovicHabermuellerWarsinkeetal.1999, author = {Gajovic, Nenad and Haberm{\"u}ller, K. and Warsinke, Axel and Schuhmann, W. and Scheller, Frieder W.}, title = {A pyruvate oxidase electrode based on an electrochemically deposited redox polymer}, year = {1999}, language = {en} } @article{JinWollenbergerKaergeletal.1997, author = {Jin, Wen and Wollenberger, Ursula and K{\"a}rgel, E. and Schunck, W.-H. and Scheller, Frieder W.}, title = {Electrochemical investigation of the intermolecular electron transfer between cytochrome c and NADPH-cytochrome P450-reductase}, year = {1997}, language = {en} } @article{NeumannGoetzWrzoleketal.2018, author = {Neumann, Bettina and G{\"o}tz, Robert and Wrzolek, Pierre and Scheller, Frieder W. and Weidinger, Inez M. and Schwalbe, Matthias and Wollenberger, Ulla}, title = {Enhancement of the Electrocatalytic Activity of Thienyl-Substituted Iron Porphyrin Electropolymers by a Hangman Effect}, series = {ChemCatChem : heterogeneous \& homogeneous \& bio- \& nano-catalysis ; a journal of ChemPubSoc Europe}, volume = {10}, journal = {ChemCatChem : heterogeneous \& homogeneous \& bio- \& nano-catalysis ; a journal of ChemPubSoc Europe}, number = {19}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1867-3880}, doi = {10.1002/cctc.201800934}, pages = {4353 -- 4361}, year = {2018}, abstract = {The thiophene-modified iron porphyrin FeT3ThP and the respective iron Hangman porphyrin FeH3ThP, incorporating a carboxylic acid hanging group in the second coordination sphere of the iron center, were electropolymerized on glassy carbon electrodes using 3,4-ethylenedioxythiophene (EDOT) as co-monomer. Scanning electron microscopy images and Resonance Raman spectra demonstrated incorporation of the porphyrin monomers into a fibrous polymer network. Porphyrin/polyEDOT films catalyzed the reduction of molecular oxygen in a four-electron reaction to water with onset potentials as high as +0.14V vs. Ag/AgCl in an aqueous solution of pH7. Further, FeT3ThP/polyEDOT films showed electrocatalytic activity towards reduction of hydrogen peroxide at highly positive potentials, which was significantly enhanced by introduction of the carboxylic acid hanging group in FeH3ThP. The second coordination sphere residue promotes formation of a highly oxidizing reaction intermediate, presumably via advantageous proton supply, as observed for peroxidases and catalases making FeH3ThP/polyEDOT films efficient mimics of heme enzymes.}, language = {en} } @article{OzcelikayKurbanogluZhangetal.2019, author = {Ozcelikay, Goksu and Kurbanoglu, Sevinc and Zhang, Xiaorong and S{\"o}z, {\c{C}}ağla Kosak and Wollenberger, Ulla and Ozkan, Sibel A. and Yarman, Aysu and Scheller, Frieder W.}, title = {Electrochemical MIP Sensor for Butyrylcholinesterase}, series = {Polymers}, volume = {11}, journal = {Polymers}, number = {12}, publisher = {MDPI}, address = {Basel}, issn = {2073-4360}, doi = {10.3390/polym11121970}, pages = {11}, year = {2019}, abstract = {Molecularly imprinted polymers (MIPs) mimic the binding sites of antibodies by substituting the amino acid-scaffold of proteins by synthetic polymers. In this work, the first MIP for the recognition of the diagnostically relevant enzyme butyrylcholinesterase (BuChE) is presented. The MIP was prepared using electropolymerization of the functional monomer o-phenylenediamine and was deposited as a thin film on a glassy carbon electrode by oxidative potentiodynamic polymerization. Rebinding and removal of the template were detected by cyclic voltammetry using ferricyanide as a redox marker. Furthermore, the enzymatic activity of BuChE rebound to the MIP was measured via the anodic oxidation of thiocholine, the reaction product of butyrylthiocholine. The response was linear between 50 pM and 2 nM concentrations of BuChE with a detection limit of 14.7 pM. In addition to the high sensitivity for BuChE, the sensor responded towards pseudo-irreversible inhibitors in the lower mM range.}, language = {en} } @misc{YarmanScheller2020, author = {Yarman, Aysu and Scheller, Frieder W.}, title = {How reliable is the electrochemical readout of MIP sensors?}, series = {Sensors}, volume = {20}, journal = {Sensors}, number = {9}, publisher = {MDPI}, address = {Basel}, issn = {1424-8220}, doi = {10.3390/s20092677}, pages = {23}, year = {2020}, abstract = {Electrochemical methods offer the simple characterization of the synthesis of molecularly imprinted polymers (MIPs) and the readouts of target binding. The binding of electroinactive analytes can be detected indirectly by their modulating effect on the diffusional permeability of a redox marker through thin MIP films. However, this process generates an overall signal, which may include nonspecific interactions with the nonimprinted surface and adsorption at the electrode surface in addition to (specific) binding to the cavities. Redox-active low-molecular-weight targets and metalloproteins enable a more specific direct quantification of their binding to MIPs by measuring the faradaic current. The in situ characterization of enzymes, MIP-based mimics of redox enzymes or enzyme-labeled targets, is based on the indication of an electroactive product. This approach allows the determination of both the activity of the bio(mimetic) catalyst and of the substrate concentration.}, language = {en} } @article{NitscheKurthDunkhorstetal.2007, author = {Nitsche, Andreas and Kurth, Andreas and Dunkhorst, Anna and P{\"a}nke, Oliver and Sielaff, Hendrik and Junge, Wolfgang and Muth, Doreen and Scheller, Frieder W. and St{\"o}cklein, Walter F. M. and Pauli, Georg and Kage, Andreas}, title = {One-step selection of vaccinia virus binding DNA-aptamers by MonoLEX}, doi = {10.1186/1472-6750-7-48}, year = {2007}, language = {en} } @article{KappBeissenhirtzGeyeretal.2006, author = {Kapp, Andreas and Beissenhirtz, Moritz Karl and Geyer, F. and Scheller, Frieder W. and Viezzoli, Maria Silvia and Lisdat, Fred}, title = {Electrochemical and sensorial behaviour of SOD mutants immobilized on gold electrodes in aqueous / organic solvent mixtures}, issn = {1040-0397}, doi = {10.1002/elan.200603620}, year = {2006}, language = {en} } @article{LiuWollenbergerKatterleetal.2006, author = {Liu, Songqin and Wollenberger, Ursula and Katterle, Martin and Scheller, Frieder W.}, title = {Ferroceneboronic acid-based amperometric biosensor for glycated hemoglobin}, issn = {0925-4005}, doi = {10.1016/j.snb.2005.07.011}, year = {2006}, abstract = {An amperometric biosensor for the determination of glycated hemoglobin in human whole blood is proposed. The principle is based on the electrochemical measurement of ferroceneboronic acid (FcBA) that has been specifically bound to the glycated N-terminus. Hemoglobin is immobilized on a zirconium dioxide nanoparticle modified pyrolytic graphite electrode (PGE) in the presence of didodecyldimethylammonium bromide (DDAB). The incubation of this sensor in FcBA solution leads to the formation of an FcBA-modified surface due to the affinity interaction between boronate and the glycated sites of the hemoglobin. The binding of FcBA results in well-defined redox peaks with an E-0' of 0.299 V versus Ag/AgCl (1 M KCl). The square wave voltammetric response of the bound FcBA reflects the amount of glycated hemoglobin at the surface. This signal increases linearily with the degree of glycated hemoglobin from 6.8 to 14.0\% of total immobilized hemoglobin. The scheme was applied to the determination of the fraction of glycated hemoglobin in whole blood samples.}, language = {en} } @article{BeissenhirtzSchellerViezzolietal.2006, author = {Beissenhirtz, Moritz Karl and Scheller, Frieder W. and Viezzoli, Maria Silvia and Lisdat, Fred}, title = {Engineered superoxide dismutase monomers for superoxide biosensor applications}, issn = {0003-2700}, doi = {10.1021/Ac051465g}, year = {2006}, abstract = {Because of its high reaction rate and specificity, the enzyme superoxide dismutase (SOD) offers great potential for the sensitive quantification of superoxide radicals in electrochemical biosensors. In this work, monomeric mutants of human Cu,Zn-SOD were engineered to contain one or two additional cysteine residues, which could be used to bind the protein to gold surfaces, thus making the use of promotor molecules unnecessary. Six mutants were successfully designed, expressed, and purified. All mutants bound directly to unmodified gold surfaces via the sulfur of the cysteine residues and showed a quasireversible, direct electron transfer to the electrode. Thermodynamic and kinetic parameters of the electron transfer were characterized and showed only slight variations between the individual mutants. For one of the mutants, the interaction with the superoxide radical was studied in more detail. For both partial reactions of the dismutation, an interaction between protein and radical could be shown. In an amperometric biosensorial approach, the SOD-mutant electrode was successfully applied for the detection of superoxide radicals. In the oxidation region, the electrode surpassed the sensitivity of the commonly used cytochrome c electrodes by similar to 1 order of magnitude while not being limited by interferences, but the electrode did not fully reach the sensitivity of dimeric Cu,Zn-SOD immobilized on MPA-modified gold}, language = {en} } @article{HalamekTellerMakoweretal.2006, author = {Halamek, Jan and Teller, Carsten and Makower, Alexander and Fournier, Didier and Scheller, Frieder W.}, title = {EQCN-based cholinesterase biosensors}, issn = {0013-4686}, doi = {10.1016/j.electacta.2006.03.047}, year = {2006}, abstract = {The binding of acetylcholinesterase (AChE) to a propidium-modified piezoelectric quartz crystal and its surface enzymatic activity have been investigated. Propidium binds to a site remote to the active center of AChE - the peripheral anionic site (PAS) - which is located on the rim of the gorge to the active site. The gold electrodes of the quartz crystal were first modified with 11-mercaptoundecanoic acid to which propidium was coupled. AChE binding was monitored by a quartz crystal nanobalance (QCN), followed by amperometric activity evaluation of the AChE loaded on the sensor. Interestingly, the binding is strong but does not inhibit AChE. However, an excess of propidium in solution inhibits the immobilized enzyme. The surface enzymatic activities observed depend on the amount of enzyme and differ according to the type and species, i.e. number of enzyme subunits (Electrophorus electricus tetrameric, Drosophila melanogaster mono- and dimeric form - DmAChE). The operational stability and regeneration, effect of propidium in solution and detection limit for substrate for various AChEs were investigated amperometrically.}, language = {en} } @article{LettauWarsinkeKatterleetal.2006, author = {Lettau, Kristian and Warsinke, Axel and Katterle, Martin and Danielsson, Bengt and Scheller, Frieder W.}, title = {A bifunctional molecularly imprinted polymer (MIP): analysis of binding and catalysis by a thermistor}, doi = {10.1002/anie.200601796}, year = {2006}, abstract = {Binding or catalysis? Both can be distinguished with a molecularly imprinted polymer (MIP) by the different patterns of heat generation. The catalytically active sites, like in the corresponding enzyme, generate a steady-state temperature increase. Thus, enzyme-like catalysis and antibody-analogue binding are analyzed simultaneously in a bifunctional MIP for the first time (see scheme).}, language = {en} } @article{BistolasWollenbergerJungetal.2005, author = {Bistolas, Nikitas and Wollenberger, Ursula and Jung, Christiane and Scheller, Frieder W.}, title = {Cytochrome P450 biosensors : a review}, year = {2005}, abstract = {Cytochrome P450 (CYP) is a large family of enzymes containing heme as the active site. Since their discovery and the elucidation of their structure, they have attracted the interest of scientist for many years, particularly due to their catalytic abilities. Since the late 1970s attempts have concentrated on the construction and development of electrochemical sensors. Although sensors based on mediated electron transfer have also been constructed, the direct electron transfer approach has attracted most of the interest. This has enabled the investigation of the electrochemical properties of the various isoforms of CYP. Furthermore, CYP utilized to construct biosensors for the determination of substrates important in environmental monitoring, pharmaceutical industry and clinical practice. (c) 2004 Elsevier B. V. All rights reserved}, language = {en} } @article{HalamekMakowerKnoescheetal.2005, author = {Halamek, Jan and Makower, Alexander and Kn{\"o}sche, Kristina and Skladal, Petr and Scheller, Frieder W.}, title = {Piezoelectric affinity sensors for cocaine and cholinesterase inhibitors}, year = {2005}, abstract = {We report here the development of piezoelectric affinity sensors for cocaine and cholinesterase inhibitors based on the formation of affinity complexes between an immobilized cocaine derivative and an anti-cocaine antibody or cholinesterase. For both binding reactions benzoylecgonine-1,8-diamino-3,4-dioxaoctane (BZE-DADOO) was immobilized on the surface of the sensor. For immobilization. pre-conjugated BZE-DADOO with 11-mercaptomonoundecanoic acid (MUA) via 2- (5-norbornen-2,3-dicarboximide)-1,1,3,3-tetramethyluronium-tetrafluoro borate (TNTU) allowed the formation of a chemisorbed monolayer on the piezosensor surface. The detection of cocaine was based oil a competitive assay. The change of frequency measured after 300 s of the binding reaction was used as the signal. The maximum binding of the antibody resulted in a frequency decrease of 35 Hz (with an imprecision 3\%, n = 3) while the presence of 100 pmol I-1 cocaine decreased the binding by 11\%. The limit of detection was consequently below 100 pmol I-1 for cocaine. The total time of one analysis was 15 min. This BZE-DADOO-modified sensor was adapted for the detection of organophosphates. BZE-DADOO - a competitive inhibitor - served as binding element for cholinesterase in a competitive assay. (C) 2004 Elsevier B.V. All rights reserved}, language = {en} } @article{BeissenhirtzSchellerStoeckleinetal.2004, author = {Beissenhirtz, Moritz Karl and Scheller, Frieder W. and St{\"o}cklein, Walter F. M. and Kurth, D. and M{\"o}hwald, Helmuth and Lisdat, Fred}, title = {Electroactive cytochrome c multilayers within a polyelectrolyte assembly}, year = {2004}, language = {en} } @article{LettauGajovicEichelmannKwaketal.2004, author = {Lettau, Kristian and Gajovic-Eichelmann, N. and Kwak, Young-Keun and Scheller, Frieder W. and Warsinke, Axel}, title = {Hydroxylasen und katalytische Polymere f{\"u}r Biochips}, year = {2004}, language = {de} } @article{KroeningSchellerWollenbergeretal.2004, author = {Kr{\"o}ning, Steffen and Scheller, Frieder W. and Wollenberger, Ursula and Lisdat, Fred}, title = {Myoglobin-Clay Electrode for Nitric Oxide (NO) Detection in Solution}, year = {2004}, language = {en} } @article{SchellerTiepnerWarsinke2004, author = {Scheller, Frieder W. and Tiepner, K. and Warsinke, Axel}, title = {Anwendung von Biosensoren in der Lebensmittelanalytik}, isbn = {3-89947-120-2}, year = {2004}, language = {de} } @article{TellerHalamekMakoweretal.2006, author = {Teller, C. and Halamek, Jan and Makower, Alexander and Fournier, Didier and Schulze, H. and Scheller, Frieder W.}, title = {A piezoelectric sensor with propidium as a recognition element for cholinesterases}, doi = {10.1016/j.snb.2005.02.053}, year = {2006}, abstract = {A piezoelectric biosensor has been developed on the basis of the reversible acetylcholinesterase (AChE) inhibitor propidium. The propidium cation was bound to a 11-mercaptoundecanoic acid monolayer on gold-coated quartz crystals. The immobilization was done via activation of carboxyl groups by 1,3-dicyclohexylcarbodiimide (DCC). Different types of cholinesterases (acetyl- and butyryl-ChE) from different origins were tested for their binding ability towards the immobilized propidium. Binding Studies were performed in a flow system, Furthermore, catalytically active and organophosphate-inhibited enzyme were compared re-aiding their binding capability. The binding constants were derived by using an one to one binding model and a refined model also including rebinding effects. It was shown that organophosphorylation of the active site hardly influences the affinity of AChE towards propidium. Furthermore the propidium-based biosensor provides equal sensitivity as compared with piezolelectric sensors with immobilized paraoxon- an active site ligand of AChE. (c) 2005 Elsevier B.V. All rights reserved}, language = {en} } @article{HalamekTellerZeraviketal.2006, author = {Halamek, Jan and Teller, Carsten and Zeravik, Jiri and Fournier, Didier and Makower, Alexander and Scheller, Frieder W.}, title = {Characterization of binding of cholinesterases to surface immobilized ligands}, issn = {0003-2719}, doi = {10.1080/00032710600713107}, year = {2006}, abstract = {We summarize here the development of various piezoelectric biosensors utilizing cholinesterase (ChE) as the recognition element. In our work we studied the interaction between cholinesterase and its ligands (propidium, carnitine, benzylgonine-1,8-diamino-3,4-dioxaoctane (BZE-DADOO) and paraoxon). The sensor modification was based on a self-assembled monolayer (SAM) of a thiol compound (11-mercaptoundecanoic acid) on the gold electrode and the subsequent covalent coupling of the cholinesterase ligand to this SAM. The ligand-modified piezoelectric sensors were placed in a flow system to allow the on-line monitoring of cholinesterase binding and the enzymatic activity quantification by amperometry. Cholinesterases from different species-acetylcholinesterase (AChE) from Electrophorus electricus , AChE from Drosophila melanogaster , and butyrylcholinesterase (BChE) of human origin-were tested on the various immobilized ligands. Our research allowed the development of a competitive assay for the detection of organophosphates in river water samples using the BZE-DADOO-modified piezosensor. Another direction of research was pointed on the characterization of the interactions between ChE and its ligands. The kinetic binding constants were derived using a one- to-one binding model}, language = {en} } @article{SchellerLisdatWollenberger2005, author = {Scheller, Frieder W. and Lisdat, Fred and Wollenberger, Ursula}, title = {Application of electrically contacted enzymes for biosensors}, isbn = {3-527- 30690-0}, year = {2005}, language = {en} } @article{SchellerBistolasLiuetal.2005, author = {Scheller, Frieder W. and Bistolas, Nikitas and Liu, Songqin and J{\"a}nchen, Michael and Katterle, Martin and Wollenberger, Ursula}, title = {Thirty years of haemoglobin electrochemistry}, year = {2005}, abstract = {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}, language = {en} } @article{LiuWollenbergerHalameketal.2005, author = {Liu, Songqin and Wollenberger, Ursula and Halamek, Jan and Leupold, Eik and St{\"o}cklein, Walter F. M. and Warsinke, Axel and Scheller, Frieder W.}, title = {Affinity interaction betwen phenylboronic acid-carrying self-assembled monolayers and FAD or HRP}, year = {2005}, abstract = {A method is provided for the recognition of glycated molecules based on their binding affinities to boronate- carrying monolayers. The affinity interaction of flavin adenine dinucleotide (FAD) and horseradish peroxidase (HRP) with phenylboronic acid monolayers on gold was investigated by using voltammetric and microgravimetric methods. Conjugates of 3-aminopherrylboronic acid and 3,3'-dithiodipropionic acid di(N-hydroxysuccinimide ester) or 11-mercaptoundecanoic acid were prepared and self-assembled on gold surfaces to generate monolayers. FAD is bound to this modified sur-face and recognized by a pair of redox peaks with a formal potential of -0.433 V in a 0.1 m phosphate buffer solution, pH 6.5. Upon addition of a sugar to the buffer, the bound FAD could be replaced, indicating that the binding is reversible. Voltammetric, mass measurements, and photometric activity assays show that the HRP can also be bound to the interface. This binding is reversible, and HRP can be replaced by sorbitol or removed in acidic solution. The effects of pH, incubation time, and concentration of H2O2 were studied by comparing the catalytic reduction of H2O2 in the presence of the electron-donor thionine. The catalytic current of the HRP-loaded electrode was proportional to HRP concentrations in the incubation solution in the range between 5 mu g mL(-1) and 0.4 mg mL(-1) with a linear slope of 3.34 mu A mL mg(-1) and a correlation coefficient of 0.9945}, language = {en} } @article{MakCheungTrauetal.2005, author = {Mak, Wing Cheung and Cheung, Kwan Yee and Trau, Dieter and Warsinke, Axel and Scheller, Frieder W. and Renneberg, Reinhard}, title = {Electrochemical bioassay utilizing encapsulated electrochemical active microcrystal biolabels}, issn = {0003-2700}, year = {2005}, abstract = {A new approach to perform electrochemical immunoassay based on the utilization of encapsulated microcrystal was developed. The microcrystal labels create a "supernova effect" upon exposure to a desired releasing agent. The microcrystal cores dissolve, and large amounts of signal-generating molecules diffuse across the capsule wall into the outer environment. Layer-by-Layer (LbL) technology was employed for the encapsulation of electrochemical signal- generating microcrystals (ferrocene microcrystals). The encapsulated microcrystals were conjugated with antibody molecules through the adsorption process. The biofunctionalized microcrystals were utilized as a probe for immunoassays. The microcrystal-based label system provided a high-signal molecule to antibody (SIP) ratio of 10(4)-10(5). Microcrystal biolabels with different antibody surface coverage (1.60-5.05 mg m(-2)) were subjected to a solid-phase immunoassay for the detection of mouse immunoglobulin G (M-IgG) molecules. The microcrystal-based immunoassay for the detection of M-IgG performed with microcrystals having antibody surface coverage of 5.05 mg m(-2) showed a sensitivity of 3.93 nA g(- 1) L-1 with a detection limit of 2.82 g L-1}, language = {en} } @article{SchellerWagener2004, author = {Scheller, Frieder W. and Wagener, C.}, title = {From gene to life}, year = {2004}, language = {en} } @article{KleuserStoeckleinPieperFuerstetal.2004, author = {Kleuser, U. and St{\"o}cklein, Walter F. M. and Pieper-F{\"u}rst, U. and Scheller, Frieder W.}, title = {Partikelverst{\"a}rkte Oberfl{\"a}chenplasmonresonanz f{\"u}r die Quantifizierung von Matrix Metalloproteinase-2}, year = {2004}, language = {de} } @article{WollenbergerBistolasJungetal.2004, author = {Wollenberger, Ursula and Bistolas, Nikitas and Jung, Christiane and Shumyantseva, V. V. and Ruzgas, T. and Scheller, Frieder W.}, title = {Elektroden-Design f{\"u}r elektronische Wechselwirkung mit Monooxygenasen}, isbn = {3-8047-2132-x}, year = {2004}, language = {de} } @article{SchellerWarsinkePfeifferetal.2004, author = {Scheller, Frieder W. and Warsinke, Axel and Pfeiffer, Dorothea and Czeponik, J.}, title = {Biosensorik / Bioanalytik}, isbn = {3-87081-372-5}, year = {2004}, language = {de} } @article{KrylovBeissenhirtzAdamzigetal.2004, author = {Krylov, Andrey V. and Beissenhirtz, Moritz Karl and Adamzig, Holger and Scheller, Frieder W. and Lisdat, Fred}, title = {Thick-film electrodes for measurement of superoxide and hydrogen peroxide based on direct protein-electrode contacts}, year = {2004}, abstract = {Cytochrome c was immobilized on screen-printed thick-film gold electrodes by a self-assembly approach using mixed monolayers of mercaptoundecanoic acid and mercaptoundecanol. Cyclic voltammetry revealed quasi-reversible electrochemical behavior of the covalently fixed protein with a formal potential of +10 mV vs. Ag/AgCl. Polarized at +150 mV vs. Ag/AgCl the electrode was found to be sensitive to superoxide radicals in the range 300-1200 nmol L-1. Compared with metal needle electrodes sensitivity and reproducibility could be improved and combined with the easiness of preparation. This allows the fabrication of disposable sensors for nanomolar superoxide concentrations. By changing the electrode potential the sensor can be switched from response to superoxide radicals to hydrogen peroxide-another reactive oxygen species. H2O2 sensitivity can be provided in the range 10-1000 mumol L-1 which makes the electrode suitable for oxidative stress studies}, language = {en} } @article{BeissenhirtzKwanKoetal.2004, author = {Beissenhirtz, Moritz Karl and Kwan, R. C. H. and Ko, K. M. and Renneberg, Reinhard and Scheller, Frieder W. and Lisdat, Fred}, title = {Comparing in vitro electrochemical measurement of superoxide scavenging activity with an in vivo assessment of antioxidant potential in Chinese tonifying herbs}, year = {2004}, abstract = {The in vitro superoxide scavenging activity (as determined by electrochemical measurement) and the in vivo antioxidant potential (as determined by a mouse model of carbon tetrachloride (CCl4) hepatotoxicity) of methanolic extracts prepared from 10 Chinese tonifying herbs were compared. Electrochemical measurement using a cytochrome c (Cyt. c) sensor showed that all of the tested herbal extracts exhibited a medium superoxide scavenging activity of different potency, as indicated by their IC50 values. The in vivo measurement demonstrated that 80\% of the herbal extracts displayed in vivo antioxidant potential, as assessed by the percentage of protection of the activity of plasma alanine aminotransferases and the hepatic glutathione regeneration capacity under CCl4-intoxicated condition. Although the in vitro antioxidant activity did not correlate quantitatively with the in vivo antioxidant potential, for 8 out of 10 samples a similar tendency was found. The rapid amperometric assessment of antioxidant potential by Cyt. c sensor may offer a convenient and direct method for screening as well as the quality control of herbal products. Copyright (C) 2004 John Wiley Sons, Ltd}, language = {en} } @article{BeissenhirtzSchellerLisdat2004, author = {Beissenhirtz, Moritz Karl and Scheller, Frieder W. and Lisdat, Fred}, title = {A superoxide sensor based on a multilayer cytochrome c electrode}, issn = {0003-2700}, year = {2004}, abstract = {A novel multilayer cytochrome c electrode for the quantification of superoxide radical concentrations is introduced. The electrode consists of alternating layers of cytochrome c and poly(aniline(sulfonic acid)) on a gold wire electrode. The formation of multilayer structures was proven by SPR experiments. Assemblies with 2-15 protein layers showed electrochemical communication with the gold electrode. For every additional layer, a substantial increase in electrochemically active cytochrome c (cyt. c) was found. For electrodes of more than 10 layers, the increase was more than 1 order of magnitude as compared to monolayer electrode systems. Thermodynamic and kinetic parameters of the electrodes were characterized. The mechanism of electron transfer within the multilayer assembly was studied, with results suggesting a protein-protein electron-transfer model. Electrodes of 2-15 layers were applied to the in vitro quantification of enzymatically generated superoxide, showing superior sensitivity as compared to a monolayer-based sensor. An electrode with 6 cyt. c/PASA layers showed the highest sensitivity of the systems studied, giving an increase in sensitivity of half an order of magnitude versus the that of the monolayer electrode. The stability of the system was optimized using thermal treatment, resulting in no loss in sensor signal or protein loading after 10 successive measurements or 2 days of storage}, language = {en} } @article{BistolasChristensonRuzgasetal.2004, author = {Bistolas, Nikitas and Christenson, A. and Ruzgas, T. and Jung, Christiane and Scheller, Frieder W. and Wollenberger, Ursula}, title = {Spectroelectrochemistry of cytochrome P450cam}, year = {2004}, abstract = {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}, language = {en} } @article{KulysKrikstopaitisSchelleretal.2004, author = {Kulys, J. and Krikstopaitis, K. and Scheller, Frieder W. and Wollenberger, Ursula}, title = {Electrochemical parameters of phenoxazine derivatives in solution and at monolayer-modified gold electrodes}, year = {2004}, abstract = {Electrochemical properties of beta-(10-phenoxazinyl) propylamine (APPX) and beta-(10-phenoxazinyl) propionic acid (PPX) have been studied in solution, and in immobilized state on gold electrodes modified with monolayers of cystamine and mercaptoundecanoic acid. A reversible diffusion-controlled process of APPX and PPX was observed at a bare gold electrode. The electrochemical conversion of both compounds at modified gold electrodes was a quasireversible diffusion-controlled process. The redox potential of immobilized APPX (443 mV) was similar to the potential in solution, while the value of the immobilized PPX was 131 mV higher than in solution. The immobilized mediators were electrocatalytically active in the fungal peroxidase-catalyzed hydrogen peroxide reduction}, language = {en} } @article{LettauWarsinkeLaschewskyetal.2004, author = {Lettau, Kristian and Warsinke, Axel and Laschewsky, Andr{\´e} and Mosbach, K. and Yilmaz, E. and Scheller, Frieder W.}, title = {An esterolytic imprinted polymer prepared via a silica-supported transition state analogue}, year = {2004}, abstract = {In this work we describe a new preparation method for an esterolytic imprinted polymer with catalytic sites on the surface. A template was prepared by immobilizing a transition state analogue (phosphoramidic acid derivative) of an esterolytic reaction within porous silica particles. Polymerization within the pores was carried out using 4- vinylimidazole as a functional monomer and divinylbenzene as a cross-linker. The polymer was released by dissolution of the silica support with hydrofluoric acid and catalytic properties were studied by incubation with three different 4- nitrophenylesters and spectrophotometric determination of the released 4-nitrophenol. For 4-nitrophenyl acetate an activity of 211 nmol min(-1) mg(-1) and a K-m value of 2.2 mmol L-1 was obtained}, language = {en} } @article{PieperFuerstKleuserStoeckleinetal.2004, author = {Pieper-F{\"u}rst, U. and Kleuser, U. and St{\"o}cklein, Walter F. M. and Warsinke, Axel and Scheller, Frieder W.}, title = {Detection of subicomolar concentrations of human matrix metalloproteinase-2 by an optical biosensor}, year = {2004}, abstract = {We describe in this paper the development of a one-step sandwich assay for the highly sensitive and fast detection of human matrix metalloproteinase (MMP)-2 (EC 3.4.24.24), using surface plasmon resonance (SPR). For the assay, two ligands were selected: monoclonal anti-MMP-2 antibody Ab-2 and the tissue inhibitor of metalloproteinases (TIMP)-2. They were chosen on the basis of (1) their affinities to MMP-2, (2) the efficiency of immobilization to the sensor chip, (3) the efficiency of adsorption to colloidal gold, and (4) the stability of these protein-coated gold particles. The assay included mixing of MMP-2 with antibody Ab-2 adsorbed to colloidal gold with a diameter of about 20 rim and injection into the flowcell of the SPR instrument containing immobilized TIMP-2. By using colloidal gold particles an amplification factor of 114 and a detection limit of 0.5 pM for MMP-2 were obtained. The precision of the assay was high even at low analyte concentrations, the standard deviation being 8.3\% for five determinations of 1 pM MMP- 2. No significant binding was observed with the structurally related MMP-9. The assay is far more sensitive and faster than commonly used methods for MMP-2 detection. As TIMP-bound MMP-2 is not detected by this method, the assay can be applied for measuring free MMP-2, reflecting the imbalance of free and inhibitor-bound enzyme in various pathological situations. (C) 2004 Elsevier Inc. All rights reserved}, language = {en} } @article{LoewSchellerWollenberger2004, author = {Loew, Noya and Scheller, Frieder W. and Wollenberger, Ursula}, title = {Characterization of self-assembling of glucose dehydrogenase in mono- and multilayers on gold electrodes}, year = {2004}, abstract = {Glucose dehydrogenase (GDH) was assembled electrostatically onto QCM-gold electrodes by their sequential deposition with anionic polyelectrolytes such as PSS and PASA. For the layer-by-layer arrangements both the microgravimetric and the electrochemical sensor signal were followed. Increasing amounts of GDH were deposited by stepwise formation of alternating layers of GDH and PSS or PASA. The mass increase was about 1.88 mug/cm(2) for one GDH/ PASA bilayer and 2.4 mug/cm(2) for a GDH/PSS bilayer. The addition of phenolic compounds resulted in an oxidation current, which could be catalytically increased by the GDH catalysed reaction in the presence of glucose. The system functions as glucose sensor when quinones are present in nonlimiting amount. The amperometric response was already diffusion limited when a single layer of GDH was adsorbed. The sensor sensitivity increased by a factor of 10 when MSA was used instead of MUA as initial electrode modifier}, language = {en} } @article{GeSchellerLisdat2003, author = {Ge, Bixia and Scheller, Frieder W. and Lisdat, Fred}, title = {Electrochemistry of immobilized CuZnSOD and FeSOD and their interaction with superoxide radicals}, year = {2003}, abstract = {Copper, zinc superoxide dismutase (CuZnSOD) from bovine erythrocytes and iron superoxide dismutase from Escherichia coli (FeSOD) were immobilized on 3-mercaptopropionic acid (MPA)-modified gold electrodes, respectively. The characterization of the SOD electrodes showed a quasi-reversible, electrochemical redox behavior with a formal potential of 47 {\~n} 4 mV and -154 {\~n} 5 mV (vs. Ag/AgCl, 1 M KCl) for surface adsorbed CuZnSOD and FeSOD, respectively. The heterogeneous electron transfer rate constants were determined to be about 65 and 35/s, respectively. Covalent fixation of both SODs was also feasible with only slight changes in the formal potential. The interaction of superoxide radicals (O2-) with the SOD electrode was investigated. No catalytic current could be observed. However, due to the fast cyclic reaction of SOD with superoxide, the communication of the protein with the electrode was strongly influenced. The amperometric detection of superoxide radicals is discussed.}, language = {en} } @article{SchellerWollenberger2003, author = {Scheller, Frieder W. and Wollenberger, Ursula}, title = {Enzyme Electrodes}, isbn = {3-527-30401-0}, year = {2003}, language = {en} } @article{BeissenhirtzSchellerLisdat2003, author = {Beissenhirtz, Moritz Karl and Scheller, Frieder W. and Lisdat, Fred}, title = {Immobilized cytochrome c sensor in organic / aqueous media for the characterization of hydrophilic and hydrophobic antioxidants}, year = {2003}, language = {en} } @article{MakowerHalamekSkladaletal.2003, author = {Makower, Alexander and Hal{\´a}mek, Jan and Skl{\´a}dal, Petr and Kernchen, Frank and Scheller, Frieder W.}, title = {New principle of direct real-time monitoring of the interaction of cholinesterase and its inhibitors by piezoelectric biosensor}, year = {2003}, language = {en} } @article{KnoescheHalamekMakoweretal.2003, author = {Kn{\"o}sche, Kristina and Hal{\´a}mek, Jan and Makower, Alexander and Fournier, Didier and Scheller, Frieder W.}, title = {Molecular recognition of cocaine by acetylcholinesterases for affinity purification and bio-sensing}, year = {2003}, language = {en} }