@misc{LauxBierHoelzel2018,
  author    = {Laux, Eva-Maria and Bier, Frank Fabian and H{\"o}lzel, Ralph},
  title     = {Electrode-based AC electrokinetics of proteins},
  series = {Bioelectrochemistry : official journal of the Bioelectrochemical Society ; an international journal devoted to electrochemical aspects of biology and biological aspects of electrochemistry},
  volume    = {120},
  journal   = {Bioelectrochemistry : official journal of the Bioelectrochemical Society ; an international journal devoted to electrochemical aspects of biology and biological aspects of electrochemistry},
  publisher = {Elsevier B.V.},
  address   = {Amsterdam},
  issn      = {1567-5394},
  doi       = {10.1016/j.bioelechem.2017.11.010},
  pages     = {76 -- 82},
  year      = {2018},
  abstract  = {Employing electric phenomena for the spatial manipulation of bioparticles from whole cells down to dissolved molecules has become a useful tool in biotechnology and analytics. AC electrokinetic effects like dielectrophoresis and AC electroosmosis are increasingly used to concentrate, separate and immobilize DNA and proteins. With the advance of photolithographical micro- and nanofabrication methods, novel or improved bioanalytical applications benefit from concentrating analytes, signal enhancement and locally controlled immobilization by AC electrokinetic effects. In this review of AC electrokinetics of proteins, the respective studies are classified according to their different electrode geometries: individual electrode pairs, interdigitated electrodes, quadrupole electrodes, and 3D configurations of electrode arrays. Known advantages and disadvantages of each layout are discussed.},
  language  = {en}
}
@article{PrueferWengerBieretal.2022,
  author    = {Pr{\"u}fer, Mareike and Wenger, Christian and Bier, Frank Fabian and Laux, Eva-Maria and H{\"o}lzel, Ralph},
  title     = {Activity of AC electrokinetically immobilized horseradish peroxidase},
  series = {Electrophoresis : microfluidics, nanoanalysis \& proteomics},
  journal   = {Electrophoresis : microfluidics, nanoanalysis \& proteomics},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {0173-0835},
  doi       = {10.1002/elps.202200073},
  pages     = {1920 -- 1933},
  year      = {2022},
  abstract  = {Dielectrophoresis (DEP) is an AC electrokinetic effect mainly used to manipulate cells. Smaller particles, like virions, antibodies, enzymes, and even dye molecules can be immobilized by DEP as well. In principle, it was shown that enzymes are active after immobilization by DEP, but no quantification of the retained activity was reported so far. In this study, the activity of the enzyme horseradish peroxidase (HRP) is quantified after immobilization by DEP. For this, HRP is immobilized on regular arrays of titanium nitride ring electrodes of 500 nm diameter and 20 nm widths. The activity of HRP on the electrode chip is measured with a limit of detection of 60 fg HRP by observing the enzymatic turnover of Amplex Red and H2O2 to fluorescent resorufin by fluorescence microscopy. The initial activity of the permanently immobilized HRP equals up to 45\% of the activity that can be expected for an ideal monolayer of HRP molecules on all electrodes of the array. Localization of the immobilizate on the electrodes is accomplished by staining with the fluorescent product of the enzyme reaction. The high residual activity of enzymes after AC field induced immobilization shows the method's suitability for biosensing and research applications.},
  language  = {en}
}
@article{LauxWengerBieretal.2020,
  author    = {Laux, Eva-Maria and Wenger, Christian and Bier, Frank Fabian and Hoelzel, Ralph},
  title     = {AC electrokinetic immobilization of organic dye molecules},
  series = {Analytical and bioanalytical chemistry : a merger of Fresenius' journal of analytical chemistry and Analusis},
  volume    = {412},
  journal   = {Analytical and bioanalytical chemistry : a merger of Fresenius' journal of analytical chemistry and Analusis},
  number    = {16},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {1618-2642},
  doi       = {10.1007/s00216-020-02480-4},
  pages     = {3859 -- 3870},
  year      = {2020},
  abstract  = {The application of inhomogeneous AC electric fields for molecular immobilization is a very fast and simple method that does not require any adaptions to the molecule's functional groups or charges. Here, the method is applied to a completely new category of molecules: small organic fluorescence dyes, whose dimensions amount to only 1 nm or even less. The presented setup and the electric field parameters used allow immobilization of dye molecules on the whole electrode surface as opposed to pure dielectrophoretic applications, where molecules are attracted only to regions of high electric field gradients, i.e., to the electrode tips and edges. In addition to dielectrophoresis and AC electrokinetic flow, molecular scale interactions and electrophoresis at short time scales are discussed as further mechanisms leading to migration and immobilization of the molecules.},
  language  = {en}
}
@article{StankeWengerBieretal.2022,
  author    = {Stanke, Sandra and Wenger, Christian and Bier, Frank Fabian and H{\"o}lzel, Ralph},
  title     = {AC electrokinetic immobilization of influenza virus},
  series = {Electrophoresis : microfluids \& proteomics},
  volume    = {43},
  journal   = {Electrophoresis : microfluids \& proteomics},
  number    = {12},
  publisher = {Wiley-Blackwell},
  address   = {Weinheim},
  issn      = {0173-0835},
  doi       = {10.1002/elps.202100324},
  pages     = {1309 -- 1321},
  year      = {2022},
  abstract  = {The use of alternating current (AC) electrokinetic forces, like dielectrophoresis and AC electroosmosis, as a simple and fast method to immobilize sub-micrometer objects onto nanoelectrode arrays is presented. Due to its medical relevance, the influenza virus is chosen as a model organism. One of the outstanding features is that the immobilization of viral material to the electrodes can be achieved permanently, allowing subsequent handling independently from the electrical setup. Thus, by using merely electric fields, we demonstrate that the need of prior chemical surface modification could become obsolete. The accumulation of viral material over time is observed by fluorescence microscopy. The influences of side effects like electrothermal fluid flow, causing a fluid motion above the electrodes and causing an intensity gradient within the electrode array, are discussed. Due to the improved resolution by combining fluorescence microscopy with deconvolution, it is shown that the viral material is mainly drawn to the electrode edge and to a lesser extent to the electrode surface. Finally, areas of application for this functionalization technique are presented.},
  language  = {en}
}