title: Analytical methods to determine electrochemical factors in electrotaxis setups and their implications for experimental design.
abstract: Direct current (DC) stimulation can be used to influence the orientation and migratory behavior of cells and results in cellular electrotaxis. Experimental work on such phenomena commonly relies on electrochemical dissolution of silver:silver-chloride (Ag:AgCl) electrodes to provide the stimulation via salt bridges. The strong ionic flow can be expected to influence the cell culture environment. In order to shed more light on which effects that must be considered, and possibly counter balanced, we here characterize a typical DC stimulation system. Silver migration speed was determined by stripping voltammetry. pH variability with stimulation was measured by ratiometric image analysis and conductivity alterations were quantified via two electrode impedance spectroscopy. It could be concluded that pH shifts towards more acidic values, in a linear manner with applied charge, after the buffering capability of the culture medium is exceeded. In contrast, the influence on conductivity was of negligible magnitude. Silver ions could enter the culture chamber at low concentrations long before a clear effect on the viability of the cultured cells could be observed. A design rule of 1cm salt bridge per C of stimulation charge transferred was however sufficient to ensure separation between cells and silver at all times.
authors.affiliation: BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Georges-Koehler Allee 079, 79110 Freiburg, Germany; Biomedical Microtechnology, Institute for Microsystems Technology (IMTEK), University of Freiburg, Georges-Koehler Allee 102, 79110 Freiburg, Germany. Electronic address: anika.schopf@imtek.uni-freiburg.de.
authors.forename: Anika
authors.initials: A
authors.lastname: Schopf
authors.affiliation: BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Georges-Koehler Allee 079, 79110 Freiburg, Germany; Freiburg Institute for Advanced Studies (FRIAS), University of Albert Strasse Freiburg, AlbertStrasse 19, 79104 Freiburg, Germany; Biomedical Microtechnology, Institute for Microsystems Technology (IMTEK), University of Freiburg, Georges-Koehler Allee 102, 79110 Freiburg, Germany. Electronic address: christian.boehler@imtek.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Boehler
authors.affiliation: BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Georges-Koehler Allee 079, 79110 Freiburg, Germany; Freiburg Institute for Advanced Studies (FRIAS), University of Albert Strasse Freiburg, AlbertStrasse 19, 79104 Freiburg, Germany; Biomedical Microtechnology, Institute for Microsystems Technology (IMTEK), University of Freiburg, Georges-Koehler Allee 102, 79110 Freiburg, Germany. Electronic address: maria.asplund@imtek.de.
authors.forename: Maria
authors.initials: M
authors.lastname: Asplund
mesh_terms: D000362:Agar / Q000737:chemistry; D000818:Animals; D002414:Cations, Monovalent / Q000737:chemistry; D018929:Cell Culture Techniques / Q000295:instrumentation*; D045744:Cell Line, Tumor; D002465:Cell Movement; D002470:Cell Survival; D004553:Electric Conductivity; D055664:Electrochemical Techniques / Q000295:instrumentation*; D004566:Electrodes; D004867:Equipment Design; D006863:Hydrogen-Ion Concentration; D051381:Rats; D012834:Silver / Q000737:chemistry*; D018030:Silver Compounds / Q000737:chemistry*
chemical_list: D002414:Cations, Monovalent; D018030:Silver Compounds; D012834:Silver; D000362:Agar; C037548:silver chloride
keywords: Conductivity; Electromigration; Electrotaxis; Microfluidics; Stripping voltammetry; pH