Colour enhanced transmission electron micrograph of lysosomes.

A cellular lysosome (green; artificially coloured). A miniature device can measure the voltage difference across the outer membranes of lysosomes and other components of cells. Credit: SCIENCE SOURCE/SPL

Nanoscience and technology

A DNA voltmeter exposes a cell’s electric inner life

Armed with a DNA core, a sensor can sneak into a cell and read out the voltage differences of the organelles inside.

From the beating of the heart to the workings of the brain, many biological processes rely on cells that use electricity to send signals. Researchers have now built a DNA-based tool that can measure the voltage differences between the insides and the outsides of membrane-wrapped structures called organelles, which are found in the cells of animals and other organisms.

Yamuna Krishnan at the University of Chicago in Illinois and her colleagues developed a sensor made of two DNA strands linked to molecules of two types of fluorescent dye, one of which responds to voltage fluctuations by changing its brightness. The DNA binds to specific proteins on a cell’s surface, allowing the sensor to enter the cell.

The sensors could measure the ‘membrane potential’ — the voltage difference across the membrane — of several types of organelle, including lysosomes, which destroy worn-out cell parts. The team even found membrane potentials in some organelles that were thought not to have them.

The sensor could help to reveal how organelles exploit electricity to regulate their function, the researchers say.