@article{FrascaRichtervonGrabergetal.2011,
  author    = {Frasca, Stefano and Richter, Claudia and von Graberg, Till and Smarsly, Bernd M. and Wollenberger, Ursula},
  title     = {Electrochemical switchable protein-based optical device},
  series = {Engineering in life sciences : Industry, Environment, Plant, Food},
  volume    = {11},
  journal   = {Engineering in life sciences : Industry, Environment, Plant, Food},
  number    = {6},
  publisher = {Wiley-Blackwell},
  address   = {Malden},
  issn      = {1618-0240},
  doi       = {10.1002/elsc.201100079},
  pages     = {554 -- 558},
  year      = {2011},
  abstract  = {The present work contributes to the development of reusable sensing systems with a visual evaluation of the detection process related to an analyte. An electrochemical switchable protein-based optical device was designed with the core part composed of cytochrome c immobilized in a mesoporous indium tin oxide film. A color-developing redox-sensitive dye was used as switchable component of the system. The cytochrome c-catalyzed oxidation of the dye by hydrogen peroxide is spectroscopically investigated. When the dye is co-immobilized with the protein, its redox state is easily controlled by application of an electrical potential at the supporting material. This enables to electrochemically reset the system to the initial state and repetitive signal generation. The implemented reset function of the color forming reaction will make calibration of small test devices possible. The principle can be extended to other color forming redox reactions and to coupled enzyme systems, such as rapid food testing and indication of critical concentrations of metabolites for health care.},
  language  = {en}
}
@article{SpricigoRichterLeimkuehleretal.2010,
  author    = {Spricigo, Roberto and Richter, Claudia and Leimk{\"u}hler, Silke and Gorton, Lo and Scheller, Frieder W. and Wollenberger, Ursula},
  title     = {Sulfite biosensor based on osmium redox polymer wired sulfite oxidase},
  issn      = {0927-7757},
  doi       = {10.1016/j.colsurfa.2009.09.001},
  year      = {2010},
  abstract  = {A biosensor, based on a redoxactive osmium polymer and sulfite oxidase on screen-printed electrodes, is presented here as a promising method for the detection of sulfite. A catalytic oxidative current was generated when a sample containing sulfite was pumped over the carbon screen-printed electrode modified with osmium redox polymer wired sulfite oxidase. A stationary value was reached after approximately 50 s and a complete measurement lasted no more than 3 min. The electrode polarized at -0.1 V (vs. Ag vertical bar AgCl 1M KCl) permits minimizing the influence of interfering substances, since these compounds can be unspecific oxidized at higher potentials. Because of the good stability of the protein film on the electrode surface, a well functioning biosensor-flow system was possible to construct. The working stability and reproducibility were further enhanced by the addition of bovine serum albumin generating a more long-term stable and biocompatible protein environment. The optimized biosensor showed a stable signal for more than a week of operation and a coefficient of variation of 4.8\% for 12 successive measurements. The lower limit of detection of the sensor was 0.5 mu M sulfite and the response was linear until 100 mu M. The high sensitivity permitted a 1:500 dilution of wine samples. The immobilization procedure and the operational conditions granted minimized interferences. Additionally, repeating the immobilization procedure to form several layers of wired SO further increased the sensitivity of such a sensor. Finally. the applicability of the developed sulfite biosensor was tested on real samples, such as white and red wines.},
  language  = {en}
}