@article{ZhangCasertaYarmanetal.2021,
  author    = {Zhang, Xiaorong and Caserta, Giorgio and Yarman, Aysu and Supala, Eszter and Tadjoung Waffo, Armel Franklin and Wollenberger, Ulla and Gyurcsanyi, Robert E. and Zebger, Ingo and Scheller, Frieder W.},
  title     = {"Out of Pocket" protein binding},
  series = {Chemosensors},
  volume    = {9},
  journal   = {Chemosensors},
  number    = {6},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2227-9040},
  doi       = {10.3390/chemosensors9060128},
  pages     = {13},
  year      = {2021},
  abstract  = {The 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.},
  language  = {en}
}
@article{TadjoungWaffoYesildagCasertaetal.2018,
  author    = {Tadjoung Waffo, Armel Franklin and Yesildag, Cigdem and Caserta, Giorgio and Katz, Sagie and Zebger, Ingo and Lensen, Marga C. and Wollenberger, Ulla and Scheller, Frieder W. and Altintas, Zeynep},
  title     = {Fully electrochemical MIP sensor for artemisinin},
  series = {Sensors and actuators : B, Chemical},
  volume    = {275},
  journal   = {Sensors and actuators : B, Chemical},
  publisher = {Elsevier},
  address   = {Lausanne},
  issn      = {0925-4005},
  doi       = {10.1016/j.snb.2018.08.018},
  pages     = {163 -- 173},
  year      = {2018},
  abstract  = {This study aims to develop a rapid, sensitive and cost-effective biomimetic electrochemical sensor for artemisinin determination in plant extracts and for pharmacokinetic studies. A novel molecularly imprinted polymer (MIP)based electrochemical sensor was developed by electropolymerization of o-phenylenediamine (o-PD) in the presence of artemisinin on gold wire surface for sensitive detection of artemisinin. The experimental parameters, including selection of functional monomer, polymerization conditions, template extraction after polymerization, influence of pH and buffer were all optimized. Every step of imprinted film synthesis were evaluated by employing voltammetry techniques, surface-enhanced infrared absorption spectroscopy (SEIRAS) and atomic force microscopy (AFM). The specificity was further evaluated by investigating non-specific artemisinin binding on non-imprinted polymer (NIP) surfaces and an imprinting factor of 6.8 was achieved. The artemisinin imprinted polymers using o-PD as functional monomer have provided highly stable and effective binding cavities for artemisinin. Cross-reactivity studies with drug molecules showed that the MIPs are highly specific for artemisinin. The influence of matrix effect was further investigated both in artificial plant matrix and diluted human serum. The results revealed a high affinity of artemisinin-MIP with dissociation constant of 7.3 x 10(-9) M and with a detection limit of 0.01 mu M and 0.02 mu M in buffer and plant matrix, respectively.},
  language  = {en}
}
@article{TadjoungWaffoMitrovaTiedemannetal.2021,
  author    = {Tadjoung Waffo, Armel Franklin and Mitrova, Biljana and Tiedemann, Kim and Iobbi-Nivol, Chantal and Leimk{\"u}hler, Silke and Wollenberger, Ulla},
  title     = {Electrochemical trimethylamine n-oxide biosensor with enzyme-based oxygen-scavenging membrane for long-term operation under ambient air},
  series = {Biosensors : open access journal},
  volume    = {11},
  journal   = {Biosensors : open access journal},
  number    = {4},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2079-6374},
  doi       = {10.3390/bios11040098},
  pages     = {17},
  year      = {2021},
  abstract  = {An amperometric trimethylamine N-oxide (TMAO) biosensor is reported, where TMAO reductase (TorA) and glucose oxidase (GOD) and catalase (Cat) were immobilized on the electrode surface, enabling measurements of mediated enzymatic TMAO reduction at low potential under ambient air conditions. The oxygen anti-interference membrane composed of GOD, Cat and polyvinyl alcohol (PVA) hydrogel, together with glucose concentration, was optimized until the O-2 reduction current of a Clark-type electrode was completely suppressed for at least 3 h. For the preparation of the TMAO biosensor, Escherichia coli TorA was purified under anaerobic conditions and immobilized on the surface of a carbon electrode and covered by the optimized O-2 scavenging membrane. The TMAO sensor operates at a potential of -0.8 V vs. Ag/AgCl (1 M KCl), where the reduction of methylviologen (MV) is recorded. The sensor signal depends linearly on TMAO concentrations between 2 mu M and 15 mM, with a sensitivity of 2.75 +/- 1.7 mu A/mM. The developed biosensor is characterized by a response time of about 33 s and an operational stability over 3 weeks. Furthermore, measurements of TMAO concentration were performed in 10\% human serum, where the lowest detectable concentration is of 10 mu M TMAO.},
  language  = {en}
}
@article{MitrovaTadjoungWaffoKaufmannetal.2018,
  author    = {Mitrova, Biljana and Tadjoung Waffo, Armel Franklin and Kaufmann, Paul and Iobbi-Nivol, Chantal and Leimk{\"u}hler, Silke and Wollenberger, Ulla},
  title     = {Trimethylamine N-Oxide Electrochemical Biosensor with a Chimeric Enzyme},
  series = {ChemElectroChem},
  volume    = {6},
  journal   = {ChemElectroChem},
  number    = {6},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {2196-0216},
  doi       = {10.1002/celc.201801422},
  pages     = {1732 -- 1737},
  year      = {2018},
  abstract  = {For the first time, an enzyme-based electrochemical biosensor system for determination of trimethylamine N-oxide (TMAO) is described. It employs an active chimeric variant of TorA in combination with an enzymatically deoxygenating system and a low-potential mediator for effective regeneration of the enzyme and cathodic current generation. TMAO reductase (TorA) is a molybdoenzyme found in marine and most enterobacteria that specifically catalyzes the reduction of TMAO to trimethylamine (TMA). The chimeric TorA, named TorA-FDH, corresponds to the apoform of TorA from Escherichia coli reconstituted with the molybdenum cofactor from formate dehydrogenase (FDH). Each enzyme, TorA and TorA-FDH, was immobilized on the surface of a carbon electrode and protected with a dialysis membrane. The biosensor operates at an applied potential of -0.8V [vs. Ag/AgCl (1M KCl)] under ambient air conditions thanks to an additional enzymatic O-2-scavenger system. A comparison between the two enzymatic sensors revealed a much higher sensitivity for the biosensor with immobilized TorA-FDH. This biosensor exhibits a sensitivity of 14.16nA/M TMAO in a useful measuring range of 2-110M with a detection limit of LOD=2.96nM (S/N=3), and was similar for TMAO in buffer and in spiked serum samples. With a response time of 16 +/- 2 s, the biosensor is stable over prolonged daily measurements (n=20). This electrochemical biosensor provides suitable applications in detecting TMAO levels in human serum.},
  language  = {en}
}