@article{ZhaoCarusoDaehneetal.2019, author = {Zhao, Shuang and Caruso, Frank and D{\"a}hne, Lars and Decher, Gero and De Geest, Bruno G. and Fan, Jinchen and Feliu, Neus and Gogotsi, Yury and Hammond, Paula T. and Hersam, Mark C. and Khademhosseini, Ali and Kotov, Nicholas and Leporatti, Stefano and Li, Yan and Lisdat, Fred and Liz-Marz{\´a}n, Luis M. and Moya, Sergio and Mulvaney, Paul and Rogach, Andrey L. and Roy, Sathi and Shchukin, Dmitry G. and Skirtach, Andre G. and Stevens, Molly M. and Sukhorukov, Gleb B. and Weiss, Paul S. and Yue, Zhao and Zhu, Dingcheng and Parak, Wolfgang J.}, title = {The Future of Layer-by-Layer Assembly: A Tribute to ACS Nano Associate Editor Helmuth M{\"o}hwald}, series = {ACS Nano}, volume = {13}, journal = {ACS Nano}, number = {6}, issn = {1936-086X}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-12356}, pages = {6151 -- 6169}, year = {2019}, abstract = {Layer-by-layer (LbL) assembly is a widely used tool for engineering materials and coatings. In this Perspective, dedicated to the memory of ACS Nano associate editor Prof. Dr. Helmuth M{\"o}hwald, we discuss the developments and applications that are to come in LbL assembly, focusing on coatings, bulk materials, membranes, nanocomposites, and delivery vehicles.}, language = {en} } @article{Lisdat2020, author = {Lisdat, Fred}, title = {Coupling biology to electrochemistry—future trends and needs}, series = {Journal of Solid State Electrochemistry}, volume = {24}, journal = {Journal of Solid State Electrochemistry}, publisher = {Springer Nature}, issn = {1433-0768}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13639}, pages = {2125 -- 2127}, year = {2020}, abstract = {The coupling of biological entities with electrodes has already quite some history and has reached a status which is not only based on phenomenological descriptions. Nowadays, we are able to effectively couple redox centres within protein molecules to electrochemical transducers. This allows the transduction of a biochemical reaction into an electrode signal with applications mainly in sensing and bioenergetics [1,2,3,4,5,6,7,8]. However, in most cases, this coupling is not direct, and shuttle molecules or side products of the reaction are used. But also for the direct coupling, significant progress has been made, and several enzymes and redox proteins can be addressed directly by electrodes [8,9,10,11,12,13]. The understanding of the functioning of developed systems is, however, in its infancy. Charge and electrostatic interactions have been mostly studied, and for small dipole molecules such as cytochrome c, the situation can be well described [14]. There is a lack of understanding for more complex enzyme molecules which brings a lot of trial and error into research.}, language = {en} } @article{GoebelTalkeAhnertetal.2019, author = {G{\"o}bel, Gero and Talke, Anja and Ahnert, Uwe and Lisdat, Fred}, title = {Electrochemical Activity Determination of Catechol-O-methyl Transferase by Selective Dopamine Detection}, series = {ChemElectroChem}, volume = {6}, journal = {ChemElectroChem}, number = {17}, publisher = {Wiley}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-13900}, pages = {4533 -- 4540}, year = {2019}, abstract = {For the treatment of Parkinson's disease, as one of the most frequent diseases of the central nervous system, several key enzymes for dopamine metabolism [e. g. catechol-O-methyl transferase (COMT)] are drug targets. For an efficient and long-lasting treatment, the activity of this enzyme should be monitored. In this study, an electrochemical approach using differential pulse voltammetry (DPV) is introduced for the activity determination. The applied electrode material, fluorine-doped tin oxide (FTO), is characterized by a clear discrimination between substrate and product of COMT, a high stability of the dopamine signal during consecutive measurements, and a linear dependency on the dopamine concentration in the range of the maximum reaction rate of COMT. Despite these advantageous results, dopamine detection in the complete activity assay is influenced by each of the added essential assay components, even though none of the added components reveal a current signal at the FTO electrode itself. After adjusting the potential range and the assay composition, these effects can be circumvented. By following the dopamine concentrations during COMT action, it can be shown that the activity of COMT can be detected by using differential pulse voltammetry (DPV) at an FTO electrode and, by analyzing different COMT amounts, quantification can be demonstrated.}, language = {en} } @misc{BalkenhohlBeutlerSchaeferetal.2007, author = {Balkenhohl, Thomas and Beutler, Falko and Sch{\"a}fer, Daniel and Lisdat, Fred}, title = {Entwicklung eines impedimetrischen Biosensors f{\"u}r den Nachweis von Antigliadin Autoantik{\"o}rpern}, series = {Wissenschaftliche Beitr{\"a}ge 2007}, volume = {12}, journal = {Wissenschaftliche Beitr{\"a}ge 2007}, issn = {0949-8214}, doi = {10.15771/0949-8214_2007_1_8}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus-522}, pages = {48 -- 57}, year = {2007}, abstract = {In der vorliegenden Arbeit wurde ein Biosensor f{\"u}r den Nachweis von Antik{\"o}rpern gegen Gliadin entwickelt. Gliadine sind Bestandteile der Getreideglutene und verantwortlich f{\"u}r die Manifestation der Z{\"o}liakie (Gluten-Unvertr{\"a}glichkeit). Der Biosensor basiert auf der Immobilisierung von Gliadin auf Goldelektroden, die zuvor mit Polystyrensulfons{\"a}ure beschichtet worden waren. Die erfolgreiche Immobilisierung wurde mit Hilfe der Quarzmikrowaage dokumentiert. Die Antigen-Antik{\"o}rper-Bindung konnte durch die Inkubation mit einem Peroxidase-markierten Zweitantik{\"o}rper und der enzymatischen Oxidation von 3-Amino-9- Ethylcarbazol (AEC) verst{\"a}rkt werden. Die Zunahme in der Elektrodenisolierung durch die Bindungs- und Ablagerungsreaktion konnte durch elektrochemische Impedanzspektroskopie (EIS) in Anwesenheit des Hexacyanoferrat- Redoxsystems gemessen werden. Die Spektren wurden mit Hilfe eines Randles-Ersatzschaltbildes ausgewertet. Hierbei konnte eine Zunahme im Ladungstransferwiderstand festgestellt werden, die pro portional zur Antigliadin-Antik{\"o}rperkonzentration, im Bereich von 10-8 M bis 10-6 M, war. Mit Hilfe dieses Sensors wurden schließlich humane Seren hinsichtlich ihrer Konzentration an Gliadinantik{\"o}rpern, sowohl f{\"u}r Immunglobuline vom Typ IgG als auch IgA, untersucht.}, language = {de} } @article{KhalidGoebelHuehnetal.2011, author = {Khalid, Waqas and G{\"o}bel, Gero and H{\"u}hn, Dominik and Montenegro, Jose-Maria and Rivera-Gil, Pilar and Lisdat, Fred and Parak, Wolfgang J.}, title = {Light triggered detection of aminophenyl phosphate with a quantum dot based enzyme electrode}, series = {Journal of Nanobiotechnology}, volume = {9}, journal = {Journal of Nanobiotechnology}, number = {46}, issn = {1477-3155}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-5808}, pages = {10}, year = {2011}, abstract = {An electrochemical sensor for p-aminophenyl phosphate (p APP) is reported. It is based on the electrochemical conversion of 4-aminophenol (4AP) at a quantum dot (QD) modified electrode under illumination. Without illumination no electron transfer and thus no oxidation of 4AP can occur. p APP as substrate is converted by the enzyme alkaline phosphatase (ALP) to generate 4AP as a product. The QDs are coupled via 1,4-benzenedithiol (BDT) linkage to the surface of a gold electrode and thus allow potential-controlled photocurrent generation. The photocurrent is modified by the enzyme reaction providing access to the substrate detection. In order to develop a photobioelectrochemical sensor the enzyme is immobilized on top of the photo-switchable layer of the QDs. Immobilization of ALP is required for the potential possibility of spatially resolved measurements. Geometries with immobilized ALP are compared versus having the ALP in solution. Data indicate that functional immobilization with layer-by-layer assembly is possible. Enzymatic activity of ALP and thus the photocurrent can be described by Michaelis- Menten kinetics. p APP is detected as proof of principle investigation within the range of 25 μM - 1 mM.}, language = {en} } @article{SternPaulyZydeketal.2016, author = {Stern, Daniel and Pauly, Diana and Zydek, Martin and Miller, Lilija and Piesker, Janett and Laue, Michael and Lisdat, Fred and Dorner, Martin B. and Dorner, Brigitte G. and Nitsche, Andreas}, title = {Development of a Genus-Specific Antigen Capture ELISA for Orthopoxviruses - Target Selection and Optimized Screening}, series = {PLoS ONE}, volume = {11}, journal = {PLoS ONE}, number = {3}, issn = {1932-6203}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-5830}, pages = {22}, year = {2016}, abstract = {Orthopoxvirus species like cowpox, vaccinia and monkeypox virus cause zoonotic infections in humans worldwide. Infections often occur in rural areas lacking proper diagnostic infrastructure as exemplified by monkeypox, which is endemic in Western and Central Africa. While PCR detection requires demanding equipment and is restricted to genome detection, the evidence of virus particles can complement or replace PCR. Therefore, an easily distributable and manageable antigen capture enzyme-linked immunosorbent assay (ELISA) for the detection of orthopoxviruses was developed to facilitate particle detection. By comparing the virus particle binding properties of polyclonal antibodies developed against surface-exposed attachment or fusion proteins, the surface protein A27 was found to be a well-bound, highly immunogenic and exposed target for antibodies aiming at virus particle detection. Subsequently, eight monoclonal anti-A27 antibodies were generated and characterized by peptide epitope mapping and surface plasmon resonance measurements. All antibodies were found to bind with high affinity to two epitopes at the heparin binding site of A27, toward either the N- or C-terminal of the crucial KKEP-segment of A27. Two antibodies recognizing different epitopes were implemented in an antigen capture ELISA. Validation showed robust detection of virus particles from 11 different orthopoxvirus isolates pathogenic to humans, with the exception of MVA, which is apathogenic to humans. Most orthopoxviruses could be detected reliably for viral loads above 1 × 103 PFU/mL. To our knowledge, this is the first solely monoclonal and therefore reproducible antibody-based antigen capture ELISA able to detect all human pathogenic orthopoxviruses including monkeypox virus, except variola virus which was not included. Therefore, the newly developed antibody-based assay represents important progress towards feasible particle detection of this important genus of viruses.}, language = {en} } @misc{VogtLisdat2004, author = {Vogt, Christian and Lisdat, Fred}, title = {BioHyTec: Biohybride Technologien in der Hauptstadtregion - Kompetenzbildung und Aufbau einer regionalen Wertsch{\"o}pfungskette}, series = {Wissenschaftliche Beitr{\"a}ge 2004}, volume = {9}, journal = {Wissenschaftliche Beitr{\"a}ge 2004}, issn = {0949-8214}, doi = {10.15771/0949-8214_2004_1_15}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-4094}, pages = {97 -- 102}, year = {2004}, abstract = {Das Bundesministerium f{\"u}r Bildung und Forschung (BMBF) startete 1999 mit dem InnoRegio-Wettbewerb eine neuartige F{\"o}rderinitiative unter der Leitidee „Innovative Impulse in den Neuen L{\"a}ndern". In zahlreichen Regionen wurden Aktivit{\"a}ten in Gang gesetzt, um neue Formen der Zusammenarbeit von Menschen aus den unterschiedlichsten Bereichen zu entwickeln und damit die Wertsch{\"o}pfung und Wettbewerbsf{\"a}higkeit in den ostdeutschen Regionen zu erh{\"o}hen. An dieser Ausschreibung nahmen in der Anfangsphase 444 Bewerberregionen teil. Nach der ersten Jury-Sitzung im Oktober 1999 wurden 50 InnoRegios ausgew{\"a}hlt, in einer Entwicklungsphase ihre Kernkompetenzen herauszufiltern und tragf{\"a}hige Innovationskonzepte zu erarbeiten. Mit der zweiten Jury-Sitzung im Herbst 2000 fiel der Startschuss zur Umsetzungsphase. Zur Zeit werden vom BMBF 23 InnoRegios in den Neuen L{\"a}ndern gef{\"o}rdert.}, language = {de} } @article{ZhaoYueZhuetal.2024, author = {Zhao, Shuang and Yue, Zhao and Zhu, Dingcheng and Harberts, Jann and Blick, Robert H. and Zierold, Robert and Lisdat, Fred and Parak, Wolfgang J.}, title = {Quantum Dot/TiO2 Nanocomposite-Based Photoelectrochemical Sensor for Enhanced H2O2 Detection Applied for Cell Monitoring and Visualization}, series = {Small}, volume = {20}, journal = {Small}, number = {45}, publisher = {Wiley}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-19642}, year = {2024}, abstract = {This work exploits the possibility of using CdSe/ZnS quantum dot (QD)-electrodes to monitor the metabolism of living cells based on photoelectrochemical (PEC) measurements. To realize that, the PEC setup is improved with respect to an enhanced photocurrent signal, better stability, and an increased signal-to-noise ratio, but also for a better biocompatibility of the sensor surface on which cells have been grown. To achieve this, a QD-TiO2 heterojunction is introduced with the help of atomic layer deposition (ALD). The heterojunction reduces the charge carrier recombination inside the semiconductor nanoparticles and improves the drift behavior. The PEC performance is carefully analyzed by adjusting the TiO2 thickness and combining this strategy with multilayer immobilizations of QDs. The optimal thickness of this coating is ≈5 nm; here, photocurrent generation can be enhanced significantly (e.g., for a single QD layer electrode by more than one order of magnitude at 0 V vs Ag/AgCl). The resulting optimized electrode is used for hydrogen peroxide (H2O2) sensing with a good sensitivity down to µmolar concentrations, reusability, stability, response rate, and repeatability. Finally, the sensing system is applied to monitor the activity of cells directly grown on top of the electrode surface.}, language = {en} } @article{GoebelDietzLisdat2009, author = {G{\"o}bel, Gero and Dietz, T. and Lisdat, Fred}, title = {Biosensor based on an oxygen reducing bilirubin oxidase electrode}, series = {Procedia Chemistry}, volume = {1}, journal = {Procedia Chemistry}, number = {1}, issn = {1876-6196}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-6237}, pages = {273 -- 276}, year = {2009}, abstract = {An oxygen reducing electrode made of bilirubin oxidase and multi-walled carbon nanotubes (BOD-MWCNT-Au electrode) is coupled to enzymes catalysing oxygen-consuming reactions such as glucose oxidase (GOD) to result in a membrane-free bienzyme electrode. The feasibility of such a molecularly assembled system stabilized by covalent linkage has been demonstrated. The electrochemical characterisation of the bienzyme electrode reveals sensitivity to the enzyme substrate. The results indicate that the BOD-electrode provides a suitable platform for sensing analytes for which oxidases of high activity are available.}, language = {en} } @article{WegerichTuranoAllegrozzietal.2009, author = {Wegerich, F. and Turano, Paola and Allegrozzi, Marco and M{\"o}hwald, H. and Lisdat, Fred}, title = {Superoxide Biosensing with Engineered Cytochrome c}, series = {Procedia Chemistry}, volume = {1}, journal = {Procedia Chemistry}, number = {1}, issn = {1876-6196}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-6523}, pages = {1287 -- 1290}, year = {2009}, abstract = {Several mutation positions have been chosen for introducing positively charged lysines in human cytochrome c (cyt c) with the aim of increasing the reaction rate with superoxide radicals (SO) and thus, the sensitivity of an electrochemical cyt c based SO biosensor. The impact of the mutations on structural and redox properties as well as on the reaction rate with SO are verified. Four mutants show a higher reaction rate with the radical compared to the wild type. These mutants are used for the construction of SO sensors based on thiol-modified gold electrodes and covalently fixed proteins. The E66K mutant electrode has a clearly higher sensitivity in comparison to the wildtype based sensor.}, language = {en} } @misc{TanneSchaeferKhalidetal.2012, author = {Tanne, Johannes and Sch{\"a}fer, Daniel and Khalid, Waqas and Parak, Wolfgang J. and Lisdat, Fred}, title = {Lichtgesteuerter bioelektrochemischer Sensor basierend auf CdSe/ZnS-Quantum Dots}, series = {Wissenschaftliche Beitr{\"a}ge 2012}, volume = {16}, journal = {Wissenschaftliche Beitr{\"a}ge 2012}, issn = {0949-8214}, doi = {10.15771/0949-8214_2012_1_2}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus-1357}, pages = {15 -- 22}, year = {2012}, abstract = {Diese Studie besch{\"a}ftigt sich mit der Untersuchung der Sauerstoffsensitivit{\"a}t von QD-Elektroden auf Basis von CdSe/ZnS-Nanopartikeln. Das Verhalten des sauerstoffabh{\"a}ngigen Photostroms wurde dabei in Abh{\"a}ngigkeit des pH-Wertes und des Potentials untersucht. Auf Grundlage dieser Sauerstoffabh{\"a}ngigkeit wurde die Enzymaktivit{\"a}t von GOD {\"u}ber Photostrommessungen evaluiert. F{\"u}r die Konstruktion eines photobioelektrochemischen Sensors, der durch Beleuchtung der entsprechenden Elektrodenfl{\"a}che ausgelesen werden kann, wurden Multischichten auf die CdSe/ZnS-modifizierten Elektroden aufgetragen. Die Layer-by-Layer Deposition von GOD mit Hilfe des Polyelektrolyten PAH zeigte, dass eine Sensorkonstruktion m{\"o}glich ist. Die Sensoreigenschaften dieser Elektroden werden drastisch durch die Menge an immobilisiertem Enzym auf der Quantum Dot-Schicht beeinflusst. Durch die Pr{\"a}paration von vier Bilayern [GOD/PAH]4 an CdSe/ ZnS Elektroden kann ein schnell ansprechbarer Sensor f{\"u}r Konzentrationen zwischen 0.1 - 5 mM Glukose hergestellt werden. Dies er{\"o}ffnet neue M{\"o}glichkeiten f{\"u}r die Multianalytdetektion mit nichtstrukturierten Sensorelektroden, lokalisierten Enzymen und r{\"a}umlich aufgel{\"o}ster Auslesung durch Licht.}, language = {de} } @article{MorlockSubramanianZounietal.2023, author = {Morlock, Sascha and Subramanian, Senthil Kumar and Zouni, Athina and Lisdat, Fred}, title = {Closing the green gap of photosystem I with synthetic fluorophores for enhanced photocurrent generation in photobiocathodes}, series = {Chemical Science}, volume = {14}, journal = {Chemical Science}, publisher = {Royal Society of Chemistry (RSC)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-17022}, pages = {1696 -- 1708}, year = {2023}, abstract = {One restriction for biohybrid photovoltaics is the limited conversion of green light by most natural photoactive components. The present study aims to fill the green gap of photosystem I (PSI) with covalently linked fluorophores, ATTO 590 and ATTO 532. Photobiocathodes are prepared by combining a 20 μm thick 3D indium tin oxide (ITO) structure with these constructs to enhance the photocurrent density compared to setups based on native PSI. To this end, two electron transfer mechanisms, with and without a mediator, are studied to evaluate differences in the behavior of the constructs. Wavelength-dependent measurements confirm the influence of the additional fluorophores on the photocurrent. The performance is significantly increased for all modifications compared to native PSI when cytochrome c is present as a redox-mediator. The photocurrent almost doubles from -32.5 to up to -60.9 μA cm-2. For mediator-less photobiocathodes, interestingly, drastic differences appear between the constructs made with various dyes. While the turnover frequency (TOF) is doubled to 10 e-/PSI/s for PSI-ATTO590 on the 3D ITO compared to the reference specimen, the photocurrents are slightly smaller since the PSI-ATTO590 coverage is low. In contrast, the PSI-ATTO532 construct performs exceptionally well. The TOF increases to 31 e-/PSI/s, and a photocurrent of -47.0 μA cm-2 is obtained. This current is a factor of 6 better than the reference made with native PSI in direct electron transfer mode and sets a new record for mediator-free photobioelectrodes combining 3D electrode structures and light-converting biocomponents.}, language = {en} } @article{MorlockSubramanianZounietal.2022, author = {Morlock, Sascha and Subramanian, Senthil Kumar and Zouni, Athina and Lisdat, Fred}, title = {Bio-inorganic hybrid structures for direct electron transfer to photosystem I in photobioelectrodes}, series = {Biosensors and Bioelectronics}, volume = {204}, journal = {Biosensors and Bioelectronics}, publisher = {Elsevier}, issn = {1873-4235}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-16770}, year = {2022}, abstract = {Synthetic materials can be combined with biological components in many ways. One example that provides scientists with multiple challenges is a photobioelectrode that converts sunlight into electrons in a biohybrid approach. In the present study several key parameters are evaluated concerning their influence on the direct electron transfer from a 3D indium tin oxide (ITO) electrode material to photosystem I (PSI) as a light-harvesting biomolecule. In contrast to previous investigations, no mediating molecule is added to shuttle the electrons to the luminal side of PSI. Thus, this setup is less complex than foregoing ones. The solution composition drastically influences the interaction of PSI with the ITO surface. Here, the application of higher buffer concentrations and the addition of salts are advantageous, whereas the nature of the buffer ions plays a minor role. The artificial electrode material's thickness is adjustable since a spin-coating procedure is used for preparation. With a 30 μm thick structure and immobilized PSI cathodic photocurrents up to 10.1 μA cm-2 are obtained at 100 mW cm-2 illumination intensity and an applied potential of -0.1V vs. Ag/AgCl. Over a period of three days the photobioelectrodes are illuminated for a total of 90 min and stored between the measurements at ambient temperature. The stability of the setup is noteworthy as still about 90\% of the photocurrent is retained. The photocathode described here offers many positive features, including a high onset potential for the photocurrent starting sligthly above the redox potentail of P700, and applicability in a wide pH range from pH 5 to 8.}, language = {en} } @article{HeinsohnNiedlAnielskietal.2022, author = {Heinsohn, Natascha Katharina and Niedl, Robert Raimund and Anielski, Alexander and Lisdat, Fred and Beta, Carsten}, title = {Electrophoretic µPAD for Purification and Analysis of DNA Samples}, series = {Biosensors}, volume = {12}, journal = {Biosensors}, number = {2}, publisher = {MDPI}, issn = {2079-6374}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-15763}, year = {2022}, abstract = {In this work, the fabrication and characterization of a simple, inexpensive, and effective microfluidic paper analytic device (µPAD) for monitoring DNA samples is reported. The glass microfiber-based chip has been fabricated by a new wax-based transfer-printing technique and an electrode printing process. It is capable of moving DNA effectively in a time-dependent fashion. The nucleic acid sample is not damaged by this process and is accumulated in front of the anode, but not directly on the electrode. Thus, further DNA processing is feasible. The system allows the DNA to be purified by separating it from other components in sample mixtures such as proteins. Furthermore, it is demonstrated that DNA can be moved through several layers of the glass fiber material. This proof of concept will provide the basis for the development of rapid test systems, e.g., for the detection of pathogens in water samples.}, language = {en} } @article{KallabisBeyerleinLisdat2024, author = {Kallabis, Conrad and Beyerlein, Peter and Lisdat, Fred}, title = {Quantitative determination of dopamine in the presence of interfering substances supported by machine learning tools}, series = {Bioelectrochemistry}, volume = {157}, journal = {Bioelectrochemistry}, number = {108667}, issn = {1567-5394}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-19277}, year = {2024}, abstract = {In the field of neuroscience as well as in the clinical setting, the neurotransmitter dopamine (DA) is an analyte which is important for research as well as medical purposes. There are plenty of methods available to measure dopamine quantitatively, with voltammetric ones such as differential pulse voltammetry (DPV) being among the most convenient and simple ones. However, dopamine often occurs, either naturally or because of the requirements of involved enzymatic systems, alongside substances that can influence the signal it produces upon electrochemical conversion. An example for such substances is the magnesium ion, which itself is not electrochemically active in the potential range needed for DA oxidation, but influences the dopamine signal. We have characterized the properties of DPV signals subject to the interaction between DA and Mg2+ and show that, although these properties are changing in a nonlinear fashion when both concentrations are varying, relatively simple linear mathematical models can be used to determine dopamine concentrations quantitatively in the presence of magnesium ions. The focus of this study is thus, the mathematical treatment of experimental data in order to overcome an analytical problem and not the investigation of the chemical background of DA-Mg2+ interaction.}, language = {en} } @article{GoebelMuellerTalkeetal.2024, author = {G{\"o}bel, Gero and M{\"u}ller, Florian and Talke, Anja and Ahnert, Uwe and Lisdat, Fred}, title = {Qualitative and quantitative protease activity tests based on protein degradation in three-dimensional structures}, series = {Bioelectrochemistry}, volume = {160}, journal = {Bioelectrochemistry}, issn = {1567-5394}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-19294}, year = {2024}, abstract = {The pattern of the activity of proteases is related to distinct physiological states of living organisms. Often activity changes of a certain protease can be assigned to a specific disease. Hence, they are useful biomarkers and a simple and fast determination method of their activity could be a valuable tool for the efficient monitoring of numerous diseases. Here, two different methods for the qualitative and quantitative determination of protease activity are demonstrated using the model system of proteinase K. The first test system is based on a protein-modified and colored 3D silica structure that changes color when exposed to the enzyme. This method has also been used for the detection of matrix metallo-protease 2 (MMP2) with gelatine as protease substrate on the plates. The second detection system uses the decrease in the voltammetric signal of a cytochrome c/DNA multilayer electrode after incubation with a protease to quantitatively determine its proteolytic activity. While activities down to 0.15 U/ml can be detected with the first method, the second one provides detection limits of about 0.03 U/ml (for proteinase K.) The functionality of both systems can be demonstrated and ways for further enhancement of sensitivity have been elucidated.}, language = {en} } @article{MorlockSubramanianZounietal.2021, author = {Morlock, Sascha and Subramanian, Senthil Kumar and Zouni, Athina and Lisdat, Fred}, title = {Scalable Three-Dimensional Photobioelectrodes Made of Reduced Graphene Oxide Combined with Photosystem I}, series = {ACS Applied Materials \& Interfaces}, volume = {13}, journal = {ACS Applied Materials \& Interfaces}, number = {9}, publisher = {American Chemical Society (ACS)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-16760}, pages = {11237 -- 11246}, year = {2021}, abstract = {Photobioelectrodes represent one of the examples where artificial materials are combined with biological entities to undertake semi-artificial photosynthesis. Here, an approach is described that uses reduced graphene oxide (rGO) as an electrode material. This classical 2D material is used to construct a three-dimensional structure by a template-based approach combined with a simple spin-coating process during preparation. Inspired by this novel material and photosystem I (PSI), a biophotovoltaic electrode is being designed and investigated. Both direct electron transfer to PSI and mediated electron transfer via cytochrome c from horse heart as redox protein can be confirmed. Electrode preparation and protein immobilization have been optimized. The performance can be upscaled by adjusting the thickness of the 3D electrode using different numbers of spin-coating steps during preparation. Thus, photocurrents up to ∼14 μA/cm2 are measured for 12 spin-coated layers of rGO corresponding to a turnover frequency of 30 e- PSI-1 s-1 and external quantum efficiency (EQE) of 0.07\% at a thickness of about 15 μm. Operational stability has been analyzed for several days. Particularly, the performance at low illumination intensities is very promising (1.39 μA/cm2 at 0.1 mW/cm2 and -0.15 V vs Ag/AgCl; EQE 6.8\%).}, language = {en} } @misc{LisdatBeissenhirtzSchelleretal.2006, author = {Lisdat, Fred and Beissenhirtz, Moritz K. and Scheller, Frieder W. and Viezzoli, Maria S.}, title = {Cystein-Mutanten der Cu,Zn-Superoxiddismutase und ihre Anwendung in Proteinelektroden f{\"u}r die Detektion von freien Sauerstoffradikalen}, series = {Wissenschaftliche Beitr{\"a}ge 2006}, volume = {11}, journal = {Wissenschaftliche Beitr{\"a}ge 2006}, issn = {0949-8214}, doi = {10.15771/0949-8214_2006_1_1}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus-216}, pages = {7 -- 11}, year = {2006}, abstract = {Das Enzym Superoxiddismutase (SOD) bietet wegen seiner hohen Reaktionsrate und seiner extrem hohen Substratspezifi t{\"a}t große Vorteile f{\"u}r eine Anwendung als Superoxidbiosensor. In dieser Arbeit wurden durch molekularbiologische Methoden Mutanten der humanen Cu,Zn-SOD gewonnen, welche ein oder zwei zus{\"a}tzliche Cystein-Reste enthielten, die eine einfache Immobilisierung des Proteins durch Bindung des Cystein-Schwefels auf Goldelektroden erm{\"o}glichten. Sechs solcher Mutanten wurden entworfen, exprimiert, aufgereinigt und elektrochemisch charakterisiert. Alle Mutanten konnten durch einen einfachen Inkubationsschritt auf Goldelektroden gebunden werden und zeigten ein quasi-reversibles elektrochemisches Ansprechen. F{\"u}r eine Mutante wurde die Anwendung als Superoxidsensor genauer untersucht und f{\"u}r beide Teilreaktionen der Dismutation ein Ansprechen des Sensors auf das Radikal gefunden. Bei Verwendung einer Teilreaktion konnte die Empfindlichkeit herk{\"o}mmlicher Monoschichtsensoren um etwa eine Gr{\"o}ßenordnung {\"u}bertroffen werden.}, language = {de} } @misc{SchubartGoebelLisdat2013, author = {Schubart, Ivo and G{\"o}bel, Gero and Lisdat, Fred}, title = {Direkte Kontaktierung des Enzyms (PQQ)-GDH und Elektroden mit Hilfe von polymermodifizierten Nanor{\"o}hren f{\"u}r die Anwendung in Biobrennstoffzellen}, series = {Wissenschaftliche Beitr{\"a}ge 2013}, volume = {17}, journal = {Wissenschaftliche Beitr{\"a}ge 2013}, issn = {0949-8214}, doi = {10.15771/0949-8214_2013_1_3}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-3127}, pages = {17 -- 22}, year = {2013}, abstract = {In dieser Studie pr{\"a}sentieren wir eine Enzymelektrode, bei der ein direkter Elektronentransfer (DET) zwischen der Pyrrolochinolinchinon-abh{\"a}ngigen Glukosedehydrogenase (PQQ)-GDH und einer Elektrode realisiert werden konnte. Hierf{\"u}r wird eine Goldelektrode mit mehrwandigen Kohlenstoffnanor{\"o}hren [engl. multi-walled carbon nanotubes (MWCNT)] modifiziert, anschließend mit einem Copolymer aus Anilinderivaten {\"u}berzogen und dann die (PQQ)-GDH (Acinetobacter calcoaceticus) kovalent immobilisiert. Die gepulste Polymersynthese wird hinsichtlich der Effektivit{\"a}t der bioelektrokatalytischen Umsetzung von Glukose optimiert. Die Glukoseoxidation startet bei einem Potential von -0,1 V vs. Ag/AgCl (1 M KCl) und Stromdichten von bis zu 500 μA/cm² (+0,1 V) k{\"o}nnen erreicht werden. Der Messbereich f{\"u}r Glukose liegt bei 0,1-5 mM (+0,1 V vs. Ag/AgCl). Der dynamische Bereich ist bei h{\"o}herem Potential auf bis zu 100 mM (+0,4 V vs Ag/AgCl) erweitert. Die Elektrode wird als Anode in einer Biobrennstoffzelle (BBZ) mit einer Bilirubinoxidase-modifizierten MWCNT/Gold-Kathode eingesetzt. Beide Elektroden basieren auf einem DET. Das Zellpotential der BBZ betr{\"a}gt 680 ±20 mV und sie erreicht eine maximale Leistungsdichte von 65 μW/cm² (bei einer Zellspannung von 350 mV).}, language = {de} } @misc{BuetowPaenkeKafkaetal.2008, author = {B{\"u}tow, Sandra M. and P{\"a}nke, Oliver and Kafka, Jan and Lisdat, Fred}, title = {Goldchipelektroden zur elektrochemischen DNA-Detektion}, series = {Wissenschaftliche Beitr{\"a}ge 2008}, volume = {13}, journal = {Wissenschaftliche Beitr{\"a}ge 2008}, issn = {0949-8214}, doi = {10.15771/0949-8214_2008_1_4}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus-653}, pages = {25 -- 34}, year = {2008}, abstract = {Im folgenden Artikel werden einfache DNA-Sensoren vorgestellt, mit deren Hilfe es durch voltammetrische und impedimetrische Messmethoden m{\"o}glich ist, schnell, sensitiv und kosteng{\"u}nstig Einzelstrang-DNA (ssDNA) nachzuweisen. Beide Messprinzipien lassen neben der spezifischen Detektion auch die Quantifizierung von DNA-Sequenzen sowie den Nachweis von einzelnen Basenfehlpaarungen innerhalb dieser Sequenzen zu. F{\"a}nger- DNA wurde zu diesem Zweck mit dem 5'-Ende auf einer Goldoberfl{\"a}che immobilisiert. Die Hybridisierung mit einem Methylenblau (MB) markierten oder unmarkierten Probenstrang konnte dann mit Hilfe der Differenzpulsvoltammetrie DPV oder der elektrochemischen Impedanzspektroskopie nachgewiesen werden. Die voltammetrische Quantifizierung erfolgte in einem direkten und kompetitiven Ansatz, mit einem Detektionslimit von 30 nM bzw. 3 nM (bei Einsatz von 0,1 μM Kompetitor- DNA). Das Detektionslimit beim impedimetrischen Nachweis lag bei 100 nM DNA. Die hier vorgestellten Sensoren sind zum einen regenerierbar und k{\"o}nnen zum anderen {\"u}ber einen Zeitraum von zwei Monaten gelagert werden.}, language = {de} }