Measuring the force of cells

Researchers in Jena and Bremen have developed a sensor to measure the force with which migrating cells push themselves away from an underlying surface.

Force analysis devices like these could one day help to identify specific cell types more reliably than conventional methods.

The sensor itself consists of a smooth surface that is studded with 250,000 tiny plastic columns measuring only five microns in diameter.

The columns are made of elastic polyurethane plastic. When a cell glides across them, it bends them sideways, and the deflection is registered by a digital camera and analysed by a software program.

'Analysis of cell locomotion is important for numerous applications,' said project manager Dr Norbert Danz. 'It could be used to check whether bone cells are successfully populating an implant, or how well a wound is healing.'

For his part in the research effort, Dr Danz, from the Fraunhofer Institute for Applied Optics and Precision Engineering in Jena, had the task of adapting a microscope so that it could deliver exactly the right cell magnification for the application.

Developing the so-called ‘cellforce’ sensor was no easy undertaking either. For one thing, the columns had to be coated in such a way that living cells were happy to move across their tips. The cells would otherwise avoid the tips and continue their journey lower down between the columns. In that case, there would be no deflection at all.

Building the delicate column structure was the job of researchers at the Fraunhofer Institute for Manufacturing Engineering and Applied Materials Research in Bremen.

To do so, they pressed liquid plastic at a pressure of 2000 bar into a negative mould and allow it to harden. It is a challenge even to manufacture the required mould, with its 250,000 micron-sized holes.

To allow cost-effective production of the cellforce sensor in the future, the researchers plan to use commercially available plastics and well-established techniques from chip manufacture.

The first ‘cellforce’ prototype is expected to be ready in a year’s time.