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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 sensor for butyrylcholinesterase(Mdpi, 2019) Özçelikay, Göksu; Kurbanoğlu, Sevinç; Zhang, Xiaorong; Söz, Çağla; Wollenberger, Ulla; Özkan, Sibel Ayşıl; Scheller, Frieder W.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.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 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 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]Öğe “Out of pocket” protein binding—A dilemma of epitope imprinted polymers revealed for human hemoglobin(2021) Zhang, Xiaorong; Caserta, Giorgio; Supala, Eszter; Wollenberger, Ulla; Gyurcsányi, Róbert E.; Zebger, Ingo; Scheller, Frieder W.; Yarman, AysuThe epitope imprinting approach applies exposed peptides as templates to synthesize Molecularly Imprinted Polymers (MIPs) for the recognition of the parent protein. While generally the template protein binding to such MIPs is considered to occur via the epitope-shaped cavities, unspecific interactions of the analyte with non-imprinted polymer as well as the detection method used may add to the complexity and interpretation of the target rebinding. To get new insights on the effects governing the rebinding of analytes, we electrosynthesized two epitope-imprinted polymers using the N-terminal pentapeptide VHLTP-amide of human hemoglobin (HbA) as the template. MIPs were prepared either by single-step electrosynthesis of scopoletin/pentapeptide mixtures or electropolymerization was performed after chemisorption of the cysteine extended VHLTP peptide. Rebinding of the target peptide and the parent HbA protein to the MIP nanofilms was quantified by square wave voltammetry using a redox probe gating, surface enhanced infrared absorption spectroscopy, and atomic force microscopy. While binding of the pentapeptide shows large influence of the amino acid sequence, all three methods revealed strong non-specific binding of HbA to both polyscopoletin-based MIPs with even higher affinities than the target peptides.
