TY - JOUR A1 - Jetzschmann, Katharina J. A1 - Jagerszki, Gyula A1 - Dechtrirat, Decha A1 - Yarman, Aysu A1 - Gajovic-Eichelmann, Nenad A1 - Gilsing, Hans-Detlev A1 - Schulz, Burkhard A1 - Gyurcsanyi, Robert E. A1 - Scheller, Frieder W. T1 - Vectorially Imprinted Hybrid Nanofilm for Acetylcholinesterase Recognition JF - Advanced functional materials N2 - Effective recognition of enzymatically active tetrameric acetylcholinesterase (AChE) is accomplished by a hybrid nanofilm composed of a propidium-terminated self-assembled monolayer (Prop-SAM) which binds AChE via its peripheral anionic site (PAS) and an ultrathin electrosynthesized molecularly imprinted polymer (MIP) cover layer of a novel carboxylate-modified derivative of 3,4-propylenedioxythiophene. The rebinding of the AChE to the MIP/Prop-SAM nanofilm covered electrode is detected by measuring in situ the enzymatic activity. The oxidative current of the released thiocholine is dependent on the AChE concentration from approximate to 0.04 x 10(-6) to 0.4 x 10(-6)m. An imprinting factor of 9.9 is obtained for the hybrid MIP, which is among the best values reported for protein imprinting. The dissociation constant characterizing the strength of the MIP-AChE binding is 4.2 x 10(-7)m indicating the dominant role of the PAS-Prop-SAM interaction, while the benefit of the MIP nanofilm covering the Prop-SAM layer is the effective suppression of the cross-reactivity toward competing proteins as compared with the Prop-SAM. The threefold selectivity gain provided by i) the shape-specific MIP filter, ii) the propidium-SAM, iii) signal generation only by the AChE bound to the nanofilm shows promise for assessing AChE activity levels in cerebrospinal fluid. KW - acetylcholinesterase KW - biomimetic sensors KW - molecularly imprinted electropolymers KW - peripheral anionic site KW - propidium Y1 - 2015 U6 - https://doi.org/10.1002/adfm.201501900 SN - 1616-301X SN - 1616-3028 VL - 25 IS - 32 SP - 5178 EP - 5183 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Yarman, Aysu A1 - Schulz, Christopher A1 - Sygmund, Cristoph A1 - Ludwig, Roland A1 - Gorton, Lo A1 - Wollenberger, Ursula A1 - Scheller, Frieder W. T1 - Third generation ATP sensor with enzymatic analyte recycling JF - Electroanalysis : an international journal devoted to fundamental and practical aspects of electroanalysis N2 - 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). KW - ATP KW - Third generation sensor KW - Enzymatic recycling KW - Cellobiose dehydrogenase KW - Hexokinase KW - Pyruvate kinase Y1 - 2014 U6 - https://doi.org/10.1002/elan.201400231 SN - 1040-0397 SN - 1521-4109 VL - 26 IS - 9 SP - 2043 EP - 2048 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Yarman, Aysu A1 - Scheller, Frieder W. T1 - The first electrochemical MIP sensor for tamoxifen JF - Sensors N2 - We present an electrochemical MIP sensor for tamoxifen (TAM)-a nonsteroidal anti-estrogen-which is based on the electropolymerisation of an O-phenylenediamine. resorcinol mixture directly on the electrode surface in the presence of the template molecule. Up to now only. bulk. MIPs for TAM have been described in literature, which are applied for separation in chromatography columns. Electro-polymerisation of the monomers in the presence of TAM generated a film which completely suppressed the reduction of ferricyanide. Removal of the template gave a markedly increased ferricyanide signal, which was again suppressed after rebinding as expected for filling of the cavities by target binding. The decrease of the ferricyanide peak of the MIP electrode depended linearly on the TAM concentration between 1 and 100 nM. The TAM-imprinted electrode showed a 2.3 times higher recognition of the template molecule itself as compared to its metabolite 4-hydroxytamoxifen and no cross-reactivity with the anticancer drug doxorubucin was found. Measurements at + 1.1 V caused a fouling of the electrode surface, whilst pretreatment of TAM with peroxide in presence of HRP generated an oxidation product which was reducible at 0 mV, thus circumventing the polymer formation and electrochemical interferences. KW - molecularly imprinted polymers KW - anticancer drug KW - tamoxifen KW - electropolymerisation Y1 - 2014 U6 - https://doi.org/10.3390/s140507647 SN - 1424-8220 VL - 14 IS - 5 SP - 7647 EP - 7654 PB - MDPI CY - Basel ER - TY - GEN A1 - Yarman, Aysu A1 - Scheller, Frieder W. T1 - The first electrochemical MIP sensor for tamoxifen T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - We present an electrochemical MIP sensor for tamoxifen (TAM)-a nonsteroidal anti-estrogen-which is based on the electropolymerisation of an O-phenylenediamine. resorcinol mixture directly on the electrode surface in the presence of the template molecule. Up to now only. bulk. MIPs for TAM have been described in literature, which are applied for separation in chromatography columns. Electro-polymerisation of the monomers in the presence of TAM generated a film which completely suppressed the reduction of ferricyanide. Removal of the template gave a markedly increased ferricyanide signal, which was again suppressed after rebinding as expected for filling of the cavities by target binding. The decrease of the ferricyanide peak of the MIP electrode depended linearly on the TAM concentration between 1 and 100 nM. The TAM-imprinted electrode showed a 2.3 times higher recognition of the template molecule itself as compared to its metabolite 4-hydroxytamoxifen and no cross-reactivity with the anticancer drug doxorubucin was found. Measurements at + 1.1 V caused a fouling of the electrode surface, whilst pretreatment of TAM with peroxide in presence of HRP generated an oxidation product which was reducible at 0 mV, thus circumventing the polymer formation and electrochemical interferences. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1046 KW - molecularly imprinted polymers KW - anticancer drug KW - tamoxifen KW - electropolymerisation Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-476173 SN - 1866-8372 IS - 1046 ER - TY - JOUR A1 - Yarman, Aysu A1 - Gröbe, Glenn A1 - Neumann, Bettina A1 - Kinne, Mathias A1 - Gajovic-Eichelmann, Nenad A1 - Wollenberger, Ursula A1 - Hofrichter, Martin A1 - Ullrich, Rene A1 - Scheibner, Katrin A1 - Scheller, Frieder W. T1 - The aromatic peroxygenase from Marasmius rutola-a new enzyme for biosensor applications JF - Analytical & bioanalytical chemistry N2 - 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. KW - Unspecific peroxygenase KW - Cytochrome P450 KW - Biosensors KW - Phenolic substances Y1 - 2012 U6 - https://doi.org/10.1007/s00216-011-5497-y SN - 1618-2642 VL - 402 IS - 1 SP - 405 EP - 412 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Peng, Lei A1 - Utesch, Tillmann A1 - Yarman, Aysu A1 - Jeoung, Jae-Hun A1 - Steinborn, Silke A1 - Dobbek, Holger A1 - Mroginski, Maria Andrea A1 - Tanne, Johannes A1 - Wollenberger, Ursula A1 - Scheller, Frieder W. T1 - Surface-Tuned Electron Transfer and Electrocatalysis of Hexameric Tyrosine-Coordinated Heme Protein JF - Chemistry - a European journal N2 - 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. KW - electrochemistry KW - electron transfer KW - heme proteins KW - molecular modeling KW - monolayers Y1 - 2015 U6 - https://doi.org/10.1002/chem.201405932 SN - 0947-6539 SN - 1521-3765 VL - 21 IS - 20 SP - 7596 EP - 7602 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Kurbanoglu, Sevinc A1 - Yarman, Aysu T1 - Simultaneous determination of hydrochlorothiazide and irbesartan from pharmaceutical dosage forms with RP-HPLC T1 - Farmasötik Dozaj Formlarında TF-YPSK ile Hidroklorotiyazid ve İrbesartanın Eş Zamanlı Tayini JF - Turkish journal of pharmaceutical sciences N2 - Objectives: In this work, a simple and rapid liquid chromatographic method for the simultaneous determination of irbesartan (IRBE) and hydrochlorothiazide (HCT) was developed and validated by reverse phase high performance liquid chromatography (RP-HPLC).
Materials and Methods: Experimental conditions such as different buffer solutions, various pH values, temperature, composition of the mobile phase, and the effect of flow rate were optimized.
Results: The developed RP-HPLC method for these antihypertensive agents was wholly validated and IRBE was detected in the linear range of 0.1-25 mu g mL(-1) and HCT was detected in the linear range of 0.25-25 mu g mL(-1). Moreover, the suggested chromatographic technique was successfully applied for the determination of the drugs in human serum and pharmaceutical dosage forms with limit of detection values of 0.008 mu g mL(-1) for IRBE and 0.012 mu g mL(-1) for HCT.
Conclusion: The proposed rapid analysis method of these antihypertensive drugs can be easily used and applied by pharmaceutical companies for which the analysis time is important. N2 - Amaç: Bu çalışmada, irbesartan (IRBE) ve hidroklorotiyazidin (HCT) eşzamanlı tayini için basit ve hızlı bir ters fazlı yüksek performanslı sıvı kromatografisi (TF-YPSK) yöntemi geliştirilmiş ve validasyon çalışmaları yapılmıştır. Gereç ve Yöntemler: Deneysel koşullar; farklı tampon çözeltileri, çeşitli pH değerleri, sıcaklık, mobil fazın bileşimi, akış hızının etkisi gibi parametrelerin üzerinden optimize edildi. Bulgular: Bu antihipertansif ajanlar için geliştirilen TF-YPSK yönteminin tüm validasyon parametrelerine ilişkin çalışmalar yapılmış, ve IRBE 0,1-25 μg mL-1 doğrusal aralığında ve HCT 0,25-25 μg mL-1 doğrusal aralığında tespit edilmiştir. Ayrıca önerilen TF-YPSK yöntemi ile IRBE için 0,008 μg mL-1 ve HCT için 0,012 μg mL-1 tayin alt sınır değerleri bulunmuştur. Geliştirilen yöntem, insan serumunda ve farmasötik dozaj formlarında bulunan IRBE ve HCT’nin belirlenmesi için başarıyla uygulanmıştır. Sonuç: Bu antihipertansif ilaçların miktar tayininde önerilen YPSK analiz yönteminin, analiz süresinin önemli olduğu ilaç firmalarında rahatlıkla kullanılabileceği ve uygulanabileceği düşünülmektedir. KW - HPLC KW - irbesartan KW - hydrochlorothiazide KW - pharmaceutical dosage forms Y1 - 2020 U6 - https://doi.org/10.4274/tjps.galenos.2019.76094 SN - 1304-530X VL - 17 IS - 5 SP - 523 EP - 527 PB - Turkish Pharmacists Association CY - Çankaya-Ankara ER - TY - JOUR A1 - Yarman, Aysu A1 - Kurbanoğlu, Sevinç A1 - Zebger, Ingo A1 - Scheller, Frieder W. T1 - Simple and robust BT - the claims of protein sensing by molecularly imprinted polymers JF - Sensors and actuators : B, Chemical : an international journal devoted to research and development of chemical transducers N2 - A spectrum of 7562 publications on Molecularly Imprinted Polymers (MIPs) has been presented in literature within the last ten years (Scopus, September 7, 2020). Around 10 % of the papers published on MIPs describe the recognition of proteins. The straightforward synthesis of MIPs is a significant advantage as compared with the preparation of enzymes or antibodies. MIPs have been synthesized from only one up to six functional monomers while proteins are made up of 20 natural amino acids. Furthermore, they can be synthesized against structures of low immunogenicity and allow multi-analyte measurements via multi-target synthesis. Electrochemical methods allow simple polymer synthesis, removal of the template and readout. Among the different sensor configurations electrochemical MIP-sensors provide the broadest spectrum of protein analytes. The sensitivity of MIP-sensors is sufficiently high for biomarkers in the sub-nanomolar region, nevertheless the cross-reactivity of highly abundant proteins in human serum is still a challenge. MIPs for proteins offer innovative tools not only for clinical and environmental analysis, but also for bioimaging, therapy and protein engineering. KW - Molecularly imprinted polymer KW - Plastibodies KW - Functional scaffolds KW - Biomimetic sensors KW - Proteins Y1 - 2021 U6 - https://doi.org/10.1016/j.snb.2020.129369 SN - 0925-4005 SN - 1873-3077 VL - 330 PB - Elsevier Science CY - Amsterdam [u.a.] ER - TY - JOUR A1 - Yarman, Aysu A1 - Wollenberger, Ursula A1 - Scheller, Frieder W. T1 - Sensors based on cytochrome P450 and CYP mimicking systems JF - ELECTROCHIMICA ACTA N2 - 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. KW - Cytochrome P450 KW - Microperoxidases KW - Catalytically active molecularly imprinted polymers KW - Biosensors KW - Personalised medicine Y1 - 2013 U6 - https://doi.org/10.1016/j.electacta.2013.03.154 SN - 0013-4686 SN - 1873-3859 VL - 110 SP - 63 EP - 72 PB - PERGAMON-ELSEVIER SCIENCE LTD CY - OXFORD ER - TY - JOUR A1 - Bognár, Zsófia A1 - Supala, Eszter A1 - Yarman, Aysu A1 - Zhang, Xiaorong A1 - Bier, Frank Fabian A1 - Scheller, Frieder W. A1 - Gyurcsanyi, Róbert E. T1 - Peptide epitope-imprinted polymer microarrays for selective protein recognition BT - application for SARS-CoV-2 RBD protein JF - Chemical science / RSC, Royal Society of Chemistry N2 - We introduce a practically generic approach for the generation of epitope-imprinted polymer-based microarrays for protein recognition on surface plasmon resonance imaging (SPRi) chips. The SPRi platform allows the subsequent rapid screening of target binding kinetics in a multiplexed and label-free manner. The versatility of such microarrays, both as synthetic and screening platform, is demonstrated through developing highly affine molecularly imprinted polymers (MIPs) for the recognition of the receptor binding domain (RBD) of SARS-CoV-2 spike protein. A characteristic nonapeptide GFNCYFPLQ from the RBD and other control peptides were microspotted onto gold SPRi chips followed by the electrosynthesis of a polyscopoletin nanofilm to generate in one step MIP arrays. A single chip screening of essential synthesis parameters, including the surface density of the template peptide and its sequence led to MIPs with dissociation constants (K-D) in the lower nanomolar range for RBD, which exceeds the affinity of RBD for its natural target, angiotensin-convertase 2 enzyme. Remarkably, the same MIPs bound SARS-CoV-2 virus like particles with even higher affinity along with excellent discrimination of influenza A (H3N2) virus. While MIPs prepared with a truncated heptapeptide template GFNCYFP showed only a slightly decreased affinity for RBD, a single mismatch in the amino acid sequence of the template, i.e. the substitution of the central cysteine with a serine, fully suppressed the RBD binding. Y1 - 2021 U6 - https://doi.org/10.1039/d1sc04502d SN - 2041-6539 VL - 13 IS - 5 SP - 1263 EP - 1269 PB - Royal Society of Chemistry CY - Cambridge ER -