How much does one living cell weigh, and how does that weight vary in real time? A newly-developed scale will let you know. Developed by researchers from ETH Zurich, the University of Basel and University College London, it's reportedly the first-ever device to be capable of such measurements.

Here's how it works …

Guided by a user watching through a fluorescence microscope, a microscopic weighing arm is lowered down into a cell culture chamber. That arm takes the form of a cantilever – meaning that it's fixed at one end, but is free to move at the other – and is made from transparent silicon coated with collagen or fibronectin.

When the arm reaches the floor of the chamber, it picks up a cell, which sticks to the underside of its free end. A pulsing blue laser is then shined on its fixed end, causing the whole arm to oscillate. Another laser, an infrared one, measures those oscillations at the free end, where the cell is hanging. By comparing the extent of the oscillations, first without and then with the cell on the arm, it's possible to calculate its weight to within trillionths of a gram.

That data is displayed on the screen of a linked computer, as a curve that shows how the weight is changing over time – the amount of time can range from milliseconds to days, depending on what's being studied. Users might wish to analyze how a cell's weight changes during the cell cycle and cell division, for example, or they might be interested in knowing how its weight is affected when it's infected by a virus.

Already, the technology has allowed the scientists to make an interesting discovery. "We established that the weight of living cells fluctuates continuously by about one to four percent as they regulate their total weight," says ETH's David Martínez-Martín, main inventor of the scale.

The technology is described in a paper recently published in the journal Nature, and is being commercialized by Swiss company Nanosurf AG.

Source: ETH Zurich

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