The Bioelectric Cell
Every living cell has a membrane potential (of about -70mV), with the inside of the cell being negative relative to its external surface. The cell membrane potential is strongly linked to the cell membrane transport mechanisms in that much of the material that passes across the membrane is ionic (charged particles), thus if the movement of charged particles changes, then it will influence the membrane potential. Conversely, if the membrane potential changes, it will influence the movement of ions.

Relative to the size of the cell, the membrane potential is massive. The membrane is, on average 7-10 nm thick (a nanometre is a thousandth of a millionth of a metre). The
equivalent voltage is somewhere in the order of 10 million volts per metre (which is reasonably impressive!).

Lightning Bolts within Cells

Using novel voltage-sensitive nanoparticles, researchers have found electric fields inside cells as strong as those produced in lightning bolts. Previously, it has only been possible to measure electric fields across cell membranes, not within the main bulk of cells. It's not clear what causes these strong fields or what they might mean. But now that it's possible to measure them, researchers hope to learn about disease states such as cancer by studying these electric fields.

University of Michigan researchers led by chemistry professor Raoul Kopelman encapsulated voltage-sensitive dyes in polymer spheres just 30 nanometers in diameter. When illuminated with blue light, the voltage-sensitive dyes emit a mixture of red and green light; the exact frequency of light emitted is influenced by the strength of local electric fields, allowing the researchers to measure those fields. Testing these nanoparticles in the internal fluid of brain-cancer cells, Kopelman found electric fields as strong as 15 million volts per meter, perhaps five times stronger than the field found in a lightning bolt.