Scientists Have Succeeded in Weighing a Single Living Cell

It's like weighing a dream. Or a thought. Only that it's material. But researchers have succeeded in weighing a single living cell.

Previous attempts resulted ineffective as any sample had to be dried, killing the cells. The new method allows for the weighing of samples as light as 1/1,000,000,000,000,000 g (one femtogram) while still on the fluid.

"The most precise mass measurements done today, down to the zeptogram (1/1, 000,000,000,000,000,000,000), require that objects are weighed in a vacuum. But so far, we haven't been able to do this for living biological samples. So, the team decided to re-examine these ultra-accurate systems - called micromechanical resonators - to see if they could be modified to measure materials in fluid." said co-author Thomas Burg, an author of the study from the department of biological engineering at the Massachusetts Institute of Technology (MIT).

Micromechanical resonators employ a tiny silicon slab, called resonator, to which the sample is bound within a vacuum and a vibration is induced. Objects vibrate differently according to their mass, so this way their mass can be estimated.

"But if fluid is then added to the vacuum, the sensitivity of the measurement is diminished. So, we turned the problem inside out. We decided to make a hollow resonator, within which you could put the fluid sample. The resonator is still surrounded by a vacuum, but the fluid is inside of it. So you 'ping' it, it vibrates, and you can then look at the frequency to determine the mass." said Burg.

This innovation permitted the researchers to weigh living cells and samples that must be kept in fluid to a much higher degree of accuracy. Further improvement could allow the technique to weigh lighter objects and this could be applied in many fields of the cell and molecular biology.