We have been working on the design, synthesis, and application of a universal, wireless, nano-optical voltmeter (NOV) to measure E fields arising from biological and non-biological systems. The measurement of electric fields in biology is largely limited to membrane-bound methods. Optical determination of the magnitude of intracellular and extracellular electric fields relies upon the use of fluorescent, luminescent, or UV-active molecules that directly interact with membranes or through translocation of charged molecules across the lipid bilayer. None of these techniques are optimal for determining electric fields throughout an entire cell. In addition, the response of the voltage dyes to changing E fields varies from cell to cell, resulting in the need to calibrate the dyes’ response to individual cells and even cell subdomains or membranes. Previously, there was no technique that allowed for the simultaneous measurement of electric fields in membranes and non-membranous (open) regions of the cell.  

The NOVs have overcome many of the obstacles current methods face. The NOV is a nano-device that is not confined to exploitation of the properties of lipid bilayers during changes in E fields. These NOVs are universal in the sense that they are calibrated prior to use, and the calibrated nano-particles then may be used in any cell, cellular compartment, or external region  (including non-cellular systems), with no further calibration steps. We have used the particles to examine changes in the mitochondrial membrane potential and the surrounding cytosol potential. These nano-devices should greatly enhance the detection and measurement of open E fields in cells and allow for cytosolic and three dimensional imaging, as well as other biomedical or technological applications.