Scientists from the US have developed a miniature flow cytometer that can analyse up to one million blood cells per second. 

Flow cytometry is a standard technique that can analyse several thousand blood cells every second. But, traditional flow cyctometers require large bench-top equipment and are not easy to use at the point of care. Now, Dino Di Carlo and colleagues at the University of California, Los Angeles, have created a microfuidic based cytometer that uses only a single pump and one camera.

Unlike normal flow cytometers which only have one channel, Di Carlo's microfluidic device has 256 channels through which cells can flow and be analysed in parallel. A fluid, known as sheath fluid, is normally used as the delivery medium in flow cytometers however the team's device allowed the cells' momentum to position the cells for analysis within the channels, eliminating the need for the extra fluid. 'By having the sheath fluid it is very difficult to have parallel focussing of cells, this is a limitation of flow cytometers- they operate in a serial manner like a one lane road. Now that you can operate in parallel you can have a highway-you can do detection in parallel and increase your throughput,' says Di Carlo.

Removing the sheath fluid also reduces the cost of consumables and allows the devices to be made more suitable for portable use and in resource limited settings.

Pushing flow cytometry to higher throughputs could also enable analysis of rare cells, such as circulating endothelial cells, progenitor cells and circulating tumour cells, explains Di Carlo. 'This could have a very important impact for diagnosis, understanding disease and follow up of patient treatment,' he adds.

Frances Ligler, an expert in microflow cytometry at the US Naval Research Laboratory, Washington DC, US, comments, 'I doubt that there is anyone who has designed or fabricated a flow cytometer that has not dreamed of a massively parallel version. This is a major breakthrough.'

Di Carlo's team now plan to combine their microflow cytometer with wide fuelled imaging techniques and electrical techniques to allow parallel cell detection.

Jennifer Newton

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