Scientists at Fraunhofer Institute for Applied Optics and Precision Engineering have developed an optical sensor that can quantify the force that a cell exerts on a special surface as it moves across it, which should allow for creating somatic cell sorting machines and single cell diagnostic devices. The project is a part of the European Information Society Technologies initiative.
It consists of a smooth surface that is studded with 250,000 tiny plastic columns measuring only five microns in diameter, rather like a fakir’s bed of nails. These columns are made of elastic polyurethane plastic. When a cell glides across them, it bends them very slightly sideways. This deflection is registered by a digital camera and analyzed by a special software program. The researchers working with project manager Dr. Norbert Danz of the Fraunhofer Institute for Applied Optics and Precision Engineering IOF in Jena have already shown that their ‘Cellforce’ sensor works. It will be the task of initial biological tests to show how different cell types behave. “Analysis of cell locomotion is important for numerous applications,” says Danz. “It could be used to check whether bone cells are successfully populating an implant, or how well a wound is healing.”
Developing the sensor was no easy undertaking. For one thing, the columns have to be coated in such a way that living cells are 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. Danz had the task of adapting the microscope required for cell magnification to make it exactly right for the application. Building the delicate column structure developed by researchers at the Fraunhofer Institute for Manufacturing Engineering and Applied Materials Research IFAM in Bremen is no less tricky: The researchers press liquid plastic at a pressure of 2000 bar into a negative mold and allow it to harden. It is a challenge even to manufacture the required mold, with its 250,000 micron-sized holes. To allow cost-effective production of the ‘Cellforce’ sensor in future, the researchers utilize commercially available plastics and well-established techniques from chip manufacture. The first ‘Cellforce’ prototype is expected to be ready in a year’s time.