“Nanosized Voltmeter” Enables Cellular-Wide Electric Field Mapping

Author: Katherine M. Tyner *† Raoul Kopelman † and Martin A. Philbert *
*Toxicology Program and †Chemistry Department, University of Michigan, Ann Arbor, Michigan Address reprint requests to Raoul Kopelman, Dept. of Chemistry, University of Michigan, 930 N. University, Ann Arbor, MI 48105. Tel.: 734-764-7541; Fax: 734-936-2778; E-mail: kopelman@umich.edu.
Conference/Journal: Biophysical Journal
Date published: 2007 Aug 15
Other: Volume ID: 93 , Issue ID: 4 , Pages: 1163-1174 , Special Notes: doi: 10.1529/biophysj.106.092452 , Word Count: 158

Previously, all biological measurements of intracellular electric fields (E fields), using voltage dyes or patch/voltage clamps, were confined to cellular membranes, which account for <0.1% of the total cellular volume. These membrane-dependent techniques also frequently require lengthy calibration steps for each cell or cell type measured. A new 30-nm “photonic voltmeter”, 1000-fold smaller than existing voltmeters, enables, to our knowledge, the first complete three-dimensional E field profiling throughout the entire volume of living cells. These nanodevices are calibrated externally and then applied for E field determinations inside any live cell or cellular compartment, with no further calibration steps. The results indicate that the E fields from the mitochondrial membranes penetrate much deeper into the cytosol than previously estimated, indicating that, electrically, the cytoplasm cannot be described as a simple homogeneous solution, as often approximated, but should rather be thought of as a complex, heterogeneous hydrogel, with distinct microdomains.