A handheld device which could offer point-of-care blood cell analysis is being developed by scientists in the UK. Team members David Holmes and Hywel Morgan, from the University of Southampton, suggest their system could find a range of applications in diagnostics.

Holmes explains that the microfluidic set-up uses electrodes to measure each blood cell's electrical properties as blood flows through the device's channels. From these measurements it is possible to distinguish and count the different types of cell, providing information used in the diagnosis, and in monitoring the treatment, of numerous diseases.  

Blood cells are identified as they flow through a microfluidic device

To verify their results the researchers fabricated the device on glass and mounted it onto a fluorescence microscope. This allowed them to observe the cells optically and confirm that the electrical data correlated with the correct identification of each cell. The system can identify three types of white blood cells: T lymphocytes, monocytes and neutrophils. 

Currently routine blood analysis uses flow cytometry which requires expensive reagents and fluorescent antibodies as well as bulky and fragile equipment. It is also very time consuming. In comparison, Holmes and Morgan's method requires only that the red blood cells are removed from the sample, which takes just 8 seconds. This step has the added benefit of enhancing the discrimination between the white cells. 

Yuri Feldman, head of the Dielectric Spectroscopy Laboratory at the Hebrew University of Jerusalem, Israel, points out that the group's combination of microfluidics, optics and impedance spectroscopy implemented on the single cell level is unique. 'It opens new avenues for effective use in modern medical diagnostics,' he says.

The next step for the team, particularly the collaborators at Philips Research Laboratories, Cambridge, UK, is to integrate the red blood cell removal step into the device. Further down the line they plan to develop power-free microfluidics, using capillary forces to pull the blood, or other samples, through the system. 'There is a lot of opportunity for developing the system further,' says Holmes.

The team's eventual aim is to produce a handheld device which would be available for around £1000 which would use disposable chips costing a few pence each. They say that uses for the device would not be restricted to blood cell analysis but could range from cancer and HIV monitoring to the examination of drinking water.

Jennifer Newton

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