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Öğe A Strep-Tag Imprinted Polymer Platform for Heterogenous Bio(electro)catalysis(Wiley, 2024) Yarman, Aysu; Waffo, Armel F. T.; Katz, Sagie; Bernitzky, Cornelius; Kovacs, Norbert; Borrero, Paloma; Frielingsdorf, Stefan; Supala, Eszter; Dragelj, Jovan; Kurbanoğlu, SevinçMolecularly imprinted polymers (MIPs) are artificial receptors equipped with selective recognition sites for target molecules. One of the most promising strategies for protein MIPs relies on the exploitation of short surface-exposed protein fragments, termed epitopes, as templates to imprint binding sites in a polymer scaffold for a desired protein. However, the lack of highresolution structural data of flexible surface-exposed regions challenges the selection of suitable epitopes. Here, we addressed this drawback by developing a polyscopoletin-based MIP that recognizes recombinant proteins via imprinting of the widely used Strep-tag II affinity peptide (Strep-MIP). Electrochemistry, surfacesensitive IR spectroscopy, and molecular dynamics simulations were employed to ensure an utmost control of the Strep-MIP electrosynthesis. The functionality of this novel platform was verified with two Strep-tagged enzymes: an O2-tolerant [NiFe]-hydrogenase, and an alkaline phosphatase. The enzymes preserved their biocatalytic activities after multiple utilization confirming the efficiency of Strep-MIP as a general biocompatible platform to confine recombinant proteins for exploitation in biotechnology.Öğe A tale of captopril detection based on an electrochemical mip sensör(2024) Yarman, Aysu; Kurbanoğlu, SevinçAmaç: Bu çalışmada antihipertansif bir ilaç olan Kaptoprilin tespitine yönelik moleküler baskılama yöntemi ile hazırlanmış sensörler kullanılarak voltametrik bir yöntem geliştirilmesi amaçlanmıştır. Gereç ve Yöntem: Moleküler baskılama yöntemi ile camsı karbon elektroların yüzeylerinde moleküler baskınlanmış polimerler oluşturulmuş ve differansiyel puls voltammetri yöntemi ile Kaptoprilin analizi gerçekleştirilmiş, sensörün performansı incelenmiştir. Sonuç ve Tartışma: 2,62 pM teşhis sınırı değeri ile 50 pM Kaptopril seviyesine kadar doğrusal bir analiz gerçekleştirilmiştir. Seçicilik çalışmaları, Kaptoprilin, diğer girişim yapabilecek, parasetamol, askorbik asit ve L-prolin gibi maddelere göre daha yüksek elektrokimyasal cevaba sahip olduğunu göstermiştir.Öğe Au-Pt nanoparticles based molecularly imprinted nanosensor for electrochemical detection of the lipopeptide antibiotic drug Daptomycin(2020) Yarman, Aysu; Özçelikay, Göksu; Kurbanoğlu, Sevinç; Scheller, Frieder W.; Ozkan, Sibel A.In this work, a novel electrochemical molecularly imprinted polymer (MIP) sensor for the detection of the lipopeptide antibiotic Daptomycin (DAP) is presented which integrates gold decorated platinum nanoparticles (Au-Pt NPs) into the nanocomposite film. The sensor was prepared by electropolymerization of o-phenylenediamine (o-PD) in the presence of DAP using cyclic voltammetry. Cyclic voltammetry and differential pulse voltammetry were applied to follow the changes in the MIP-layer related to rebinding and removal of the target DAP by using the redox marker [Fe(CN)6] 3?/4– . Under optimized operational conditions, the MIP/Au-Pt NPs/ GCE nanosensor exhibits a linear response in the range of 1-20 pM towards DAP. The limit of detection and limit of quantification were determined to be 0.161pM ± 0.012 and 0.489pM ± 0.012, respectively. The sensitivity towards the antibiotics Vancomycin and Erythromycin and the amino acids glycine and tryptophan was below 7 percent as compared with DAP. Moreover, the nanosensor was also successfully used for the detection of DAP in deproteinated human serum samples.Öğe Öğe Öğe Determination of amino acids and other clinically significant molecules at surfactant-based electrochemical sensors and biosensors(Elsevier, 2024) Ghobadloo, Parvin Abedi; Keles, Gulsu; Yarman, Aysu; Hamidi, Samin; Kurbanoglu, SevincSurfactants (surface-active agents) are substances that, when used in very small amounts, significantly reduce the surface tension of water. Surfactants are usually organic compounds with hydrophobic groups (water repellent) that play the tail and hydrophilic groups (water absorbent) that play the role of head, so they dissolve in organic solvents and water according to their molecular structure. They can be classified as anionic, cationic, amphoteric, and nonionic. Amino acids are the primary building blocks of proteins, and extensive research has been dedicated to amino acids and biologically important compounds. Many methods have been developed for detecting amino acids and biologically important compounds based on high-performance liquid chromatography, colorimetry, fluorimetry, molecular imprinted polymer methods, capillary electrophoresis, etc. Hence, this chapter will deal with the electrochemical sensors and biosensors for detecting amino acids and biologically important compounds. © 2024 Elsevier Inc. All rights reserved.Öğe Development of a molecularly imprinted polymer-based electrochemical sensor for tyrosinase(Scientific & Technical Research Council Turkey-TUBITAK, 2018) Yarman, AysuFor the first time a molecularly imprinted polymer (MIP)-based sensor for tyrosinase is described. This sensor is based on the electropolymerization of scopoletin or o-phenylenediamine in the presence of tyrosinase from mushrooms, which has a high homology to the human enzyme. The template was removed either by treatment with proteinase K or by alkaline treatment. The measuring signal was generated either by measuring the formation of a product by the target enzyme or by evaluation of the permeability of the redox marker ferricyanide. The o-phenylenediamine-based MIP sensor has a linear measuring range up to 50 nM of tyrosinase with a limit of detection of 3.97 nM (R-2 = 0.994) and shows good discrimination towards other proteins, e.g., bovine serum albumin and cytochrome c.Öğe Editorial(Elsevier BV, 2023) Yarman, Aysu; Lisdat, Fred; Wollenberger, UllaThis special issue on biosensors and protein electrochemistry is dedicated to Professor Frieder W. Scheller on occasion of his 80th birthday in August 2022. Frieder Scheller’s contributions to the field of bioelectrochemistry and bioanalysis, which covers the areas of protein electrochemistry, biosensors, molecular technology, and biomimetics have been influential for countless ongoing research activities. With the present collection of original articles we present a selection of current research related to Frieder’s fields of expertise spanning from the early work on bioelectrochemistry of P450 enzymes, biosensors with different recognition elements and schemes for transducer coupling and their application to his more recent activities on biomimetic biosensors for protein recognition.Öğe Electrochemical MIP sensors for environmental analysis(Springer, 2023) Yarman, Aysu; Kurbanoğlu, Sevinç; Zhang, Xiaorong; Scheller, Frieder W.[Özet yok]Öğe Electrochemical MIP-sensors for drugs(Bentham Science Publ Ltd, 2018) Yarman, Aysu; Kurbanoğlu, Sevinç; Jetzschmann, Katharina J.; Özkan, Sibel A.; Wollenberger, Ulla; Scheller, Frieder W.In order to replace bio-macromolecules by stable synthetic materials in separation techniques and bioanalysis biomimetic receptors and catalysts have been developed: Functional monomers are polymerized together with the target analyte and after template removal cavities are formed in the "molecularly imprinted polymer" (MIP) which resemble the active sites of antibodies and enzymes. Starting almost 80 years ago, around 1,100 papers on MIPs were published in 2016. Electropolymerization allows to deposit MIPs directly on voltammetric electrodes or chips for quartz crystal microbalance (QCM) and surface plasmon resonance (SPR). For the readout of MIPs for drugs amperometry, differential pulse voltammetry (DPV) and impedance spectroscopy (EIS) offer higher sensitivity as compared with QCM or SPR. Application of simple electrochemical devices allows both the reproducible preparation of MIP sensors, but also the sensitive signal generation. Electrochemical MIP-sensors for the whole arsenal of drugs, e.g. the most frequently used analgesics, antibiotics and anticancer drugs have been presented in literature and tested under laboratory conditions. These biomimetic sensors typically have measuring ranges covering the lower nano-up to millimolar concentration range and they are stable under extreme pH and in organic solvents like nonaqueous extracts.Öğe Electrochemical readout of molecularly imprinted polymers: potentials and challenges(2020) Yarman, Aysu; Özçelikay, Göksu; Kurbanoğlu, Sevinç; Peng, Lei; Söz, Çağla; Özkan, Sibel Ayşıl; Wollenberger, Ulla; Scheller, Frieder W.Molecularly imprinted polymers (MIPs) are one of the most frequently studied alternative recognition elements in chromatography and sensorics. They are prepared by polymerizing the target analyte (socalled template) and functional monomers (in the presence or absence of cross-linkers). Subsequent removal of the template from the polymer network results in the formation of cavities with a molecular memory, which is complementary in size, shape and functionality to the template.Öğe Electrochemical sensors(Elsevier, 2024) Keles, Gulsu; Oktay, Aysel; Aslan, Pakize; Yarman, Aysu; Kurbanoglu, SevincOver the past few years, electroanalytical techniques have become increasingly widespread in the analysis of various component applications. They are noticeable by their distinctive attributes, such as sensitivity, selectivity, rapid response, minimal solution volume requirements, and user-friendliness. Electrochemical techniques such as cyclic voltammetry, differential pulse voltammetry, square wave voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy are mentioned in this chapter. Polymers received specific attention and a critical role in the advancement and design of electrochemical sensors. Conducting polymers’ (CPs) polymer backbone chain is characterized by alternating single and double bond configurations, which allow CPs to conduct electricity up to a certain limit, allowing them to possess attractive intrinsic features advantageous in electronic applications. Molecular imprinting, a method that forms specific recognition sites in polymer matrices, is currently extensively utilized in the development of robust sensors in various fields such as industries, diagnostics, and environmental analysis. This chapter describes recent applications and some examples of CPs and molecularly imprinted polymers based sensors. © 2024 Elsevier Inc. All rights reserved.Öğe Electrosynthesized MIPs for transferrin: Plastibodies or nano-filters?(Elsevier Advanced Technology, 2018) Zhang, Xiaorong; Yarman, Aysu; Erdossy, Julia; Katz, Sagie; Zebger, Ingo; Jetzschmann, Katharina J.; Scheller, Frieder W.Molecularly imprinted polymer (MP) nanofilrns for transferrin (Trf) have been synthesized on gold surfaces by electro-polymerizing the functional monomer scopoletin in the presence of the protein target or around pre-adsorbed Trf. As determined by atomic force microscopy (AFM) the film thickness was comparable with the molecular dimension of the target. The target (re)binding properties of the electro-synthesized MIP films was evaluated by cyclic voltammetry (CV) and square wave voltammetry (SWV) through the target-binding induced permeability changes of the MIP nanofilms to the ferricyanide redox marker, as well as by surface plasmon resonance (SPR) and surface enhanced infrared absorption spectroscopy (SEIRAS) of the immobilized protein molecules. For Trf a linear concentration dependence in the lower micromolar range and an imprinting factor of similar to 5 was obtained by SWV and SPR. Furthermore, non-target proteins including the iron-free apo-Trf were discriminated by pronounced size and shape specificity. Whilst it is generally assumed that the rebinding of the target or of cross-reacting proteins exclusively takes place at the polymer here we considered also the interaction of the protein molecules with the underlying gold transducers. We demonstrate by SWV that adsorption of proteins suppresses the signal of the redox marker even at the bare gold surface and by SEIRAS that the treatment of the MIP with proteinase K or NaOH only partially removes the target protein. Therefore, we conclude that when interpreting binding of proteins to directly MIP-covered gold electrodes the interactions between the protein and the gold surface should also be considered.Öğe Electrosynthesized molecularly imprinted polymer for laccase using the inactivated enzyme as the target(Wiley-V C H Verlag Gmbh, 2018) Yarman, AysuThe first molecularly imprinted polymer (MIP) for the recognition of the copper-enzyme laccase was successfully prepared by electropolymerizing scopoletin in the presence of alkaline-inactivated enzyme. Laccase-MIP and the control polymer without laccase (nonimprinted polymer, NIP) were characterized by voltammetry using the redox marker ferricyanide. After electropolymerization, the signals for ferricyanide for both the MIP and the NIP were almost completely suppressed and increased after removal of the target from the polymer layer. Rebinding of both inactivated and active laccase decreased the ferricyanide peak currents to almost equal extent. The relative decrease of signal suppression approached saturation above 10 nM. Furthermore, the surface activity of rebound laccase toward the oxidation of catechol was investigated. The surface activity approached saturation above 10 nM, a value close to the value of the measurements with ferricyanide. Interaction of NIP with laccase brought about a six times smaller signal of catechol oxidation.Öğe Enzymes as tools in MIP-Sensors(Mdpi, 2017) Yarman, Aysu; Jetzschmann, Katharina J.; Neumann, Bettina; Zhang, Xiaorong; Wollenberger, Ulla; Cordin, Aude; Scheller, Frieder W.Molecularly imprinted polymers (MIPs) have the potential to complement antibodies in bioanalysis, are more stable under harsh conditions, and are potentially cheaper to produce. However, the affinity and especially the selectivity of MIPs are in general lower than those of their biological pendants. Enzymes are useful tools for the preparation of MIPs for both low and high-molecular weight targets: As a green alternative to the well-established methods of chemical polymerization, enzyme-initiated polymerization has been introduced and the removal of protein templates by proteases has been successfully applied. Furthermore, MIPs have been coupled with enzymes in order to enhance the analytical performance of biomimetic sensors: Enzymes have been used in MIP-sensors as tracers for the generation and amplification of the measuring signal. In addition, enzymatic pretreatment of an analyte can extend the analyte spectrum and eliminate interferences.Öğe How an ACE2 mimicking epitope-MIP nanofilm recognizes template-related peptides and the receptor binding domain of SARS-CoV-2(Royal Society of Chemistry, 2022) Zhang, Xiaorong; Waffo, Armel T.; Yarman, Aysu; Kovacs, Norbert; Bognar, Zsofia; Wollenberger, Ulla; El-Sherbiny, Ibrahim M.; Hassan, Rabeay Y. A.; Bier, Frank F.; Gyurcsanyi, Robert E; Zebger, Ingo; Scheller, Frieder W.Here we aim to gain a mechanistic understanding of the formation of epitope-imprinted polymer nanofilms using a non-terminal peptide sequence, i.e. the peptide GFNCYFP (G485 to P491) of the SARS-CoV-2 receptor binding domain (RBD). This epitope is chemisorbed on the gold surface through the central cysteine 488 followed by the electrosynthesis of a similar to 5 nm thick polyscopoletin film around the surface confined templates. The interaction of peptides and the parent RBD and spike protein with the imprinted polyscopoletin nanofilm was followed by electrochemical redox marker gating, surface enhanced infrared absorption spectroscopy and conductive AFM. Because the use of non-terminal epitopes is especially intricate, here we characterize the binding pockets through their interaction with 5 peptides rationally derived from the template sequence, i.e. implementing central single amino acid mismatch as well as elongations and truncations at its C- and N- termini. Already a single amino acid mismatch, i.e. the central Cys488 substituted by a serine, results in ca. 15-fold lower affinity. Further truncation of the peptides to tetrapeptide (EGFN) and hexapeptide (YFPLQS) results also in a significantly lower affinity. We concluded that the affinity towards the different peptides is mainly determined by the four amino acid motif CYFP present in the sequence of the template peptide. A higher affinity than that for the peptides is found for the parent proteins RBD and spike protein, which seems to be due to out of cavity effects caused by their larger footprint on the nanofilm surface.Öğe How reliable is the electrochemical readout of MIP sensors?(Sensors,, 2020) Yarman, Aysu; Scheller, Frieder W.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.Öğe Imprinted Polymers on the Route to Plastibodies for Biomacromolecules (MIPs), Viruses (VIPs), and Cells (CIPs)(Springer, 2024) Yarman, Aysu; Zhang, Xiaorong; Bagheri, Mandien; El-Sherbiny, Ibrahim M.; Hassan, Rabeay Y. A.; Kurbanoğlu, Sevinç; Waffo, Armel Franklin Tadjoung; Zebger, Ingo; Karabulut, Tutku Ceren; Bier, Frank F.; Lieberzeit, Peter; Scheller, Frieder W.Around 30% of the scientific papers published on imprinted polymers describe the recognition of proteins, nucleic acids, viruses, and cells. The straightforward synthesis from only one up to six functional monomers and the simple integration into a sensor are significant advantages as compared with enzymes or antibodies. Furthermore, they can be synthesized against toxic substances and structures of low immunogenicity and allow multi-analyte measurements via multi-template synthesis. The affinity is sufficiently high for protein biomarkers, DNA, viruses, and cells. However, the cross-reactivity of highly abundant proteins is still a challenge.Öğe Insights in electrosynthesis, target binding, and stability of peptide-imprinted polymer nanofilms(2021) Yarman, Aysu; Caserta, Giorgio; Gyurcsányi, Róbert E.; Wollenberger, Ulla; Zhang, Xiaorong; Zebger, Ingo; Supala, Eszter; Scheller, Frieder W.Molecularly imprinted polymer (MIP) nanofilms have been successfully implemented for the recognition of different target molecules: however, the underlying mechanistic details remained vague. This paper provides new insights in the preparation and binding mechanism of electrosynthesized peptide-imprinted polymer nanofilms for selective recognition of the terminal pentapeptides of the ß-chains of human adult hemoglobin, HbA, and its glycated form HbA1c. To differentiate between peptides differing solely in a glucose adduct MIP nanofilms were prepared by a two-step hierarchical electrosynthesis that involves first the chemisorption of a cysteinyl derivative of the pentapeptide followed by electropolymerization of scopoletin. This approach was compared with a random single-step electrosynthesis using scopoletin/pentapeptide mixtures. Electrochemical monitoring of the peptide binding to the MIP nanofilms by means of redox probe gating revealed a superior affinity of the hierarchical approach with a Kd value of 64.6 nM towards the related target. Changes in the electrosynthesized non-imprinted polymer and MIP nanofilms during chemical, electrochemical template removal and rebinding were substantiated in situ by monitoring the characteristic bands of both target peptides and polymer with surface enhanced infrared absorption spectroscopy. This rational approach led to MIPs with excellent selectivity and provided key mechanistic insights with respect to electrosynthesis, rebinding and stability of the formed MIPsÖğe Label-Free MIP sensors for protein biomarkers(Springer, 2017) Zhang, Xiaorong; Jetzschmann, Katharina; Yarman, Aysu; Scheller, Frieder W.; Wollenberger, Ulla[Özet yok]
