title: Dielectrophoretic immobilization of proteins: Quantification by atomic force microscopy.
abstract: The combination of alternating electric fields with nanometer-sized electrodes allows the permanent immobilization of proteins by dielectrophoretic force. Here, atomic force microscopy is introduced as a quantification method, and results are compared with fluorescence microscopy. Experimental parameters, for example the applied voltage and duration of field application, are varied systematically, and the influence on the amount of immobilized proteins is investigated. A linear correlation to the duration of field application was found by atomic force microscopy, and both microscopical methods yield a square dependence of the amount of immobilized proteins on the applied voltage. While fluorescence microscopy allows real-time imaging, atomic force microscopy reveals immobilized proteins obscured in fluorescence images due to low S/N. Furthermore, the higher spatial resolution of the atomic force microscope enables the visualization of the protein distribution on single nanoelectrodes. The electric field distribution is calculated and compared to experimental results with very good agreement to atomic force microscopy measurements.
authors.affiliation: Fraunhofer Institute for Cell Therapy and Immunology, Branch Bioanalytics and Bioprocesses (IZI-BB), Potsdam-Golm, Germany.
authors.forename: Eva-Maria
authors.initials: EM
authors.lastname: Laux
authors.affiliation: Fraunhofer Institute for Cell Therapy and Immunology, Branch Bioanalytics and Bioprocesses (IZI-BB), Potsdam-Golm, Germany.
authors.forename: Xenia
authors.initials: X
authors.lastname: Knigge
authors.affiliation: Fraunhofer Institute for Cell Therapy and Immunology, Branch Bioanalytics and Bioprocesses (IZI-BB), Potsdam-Golm, Germany.
authors.forename: Frank F
authors.initials: FF
authors.lastname: Bier
authors.affiliation: IHP GmbH-Leibniz Institute for Innovative Microelectronics, Frankfurt (Oder), Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Wenger
authors.affiliation: Fraunhofer Institute for Cell Therapy and Immunology, Branch Bioanalytics and Bioprocesses (IZI-BB), Potsdam-Golm, Germany.
authors.forename: Ralph
authors.initials: R
authors.lastname: Hölzel
mesh_terms: D003198:Computer Simulation; D004574:Electromagnetic Fields; D055767:Immobilized Proteins / Q000032:analysis* / Q000737:chemistry; D018625:Microscopy, Atomic Force
chemical_list: D055767:Immobilized Proteins
keywords: Atomic force microscopy; Dielectrophoresis; Electric field simulation; Immobilization; Protein