Flow Cytometry: Small, inexpensive flow cytometer automates fast tumor cell counting

Cancerous growths release circulating tumor cells (CTCs) into the bloodstream, and their number indicates the effectiveness of therapy: A decrease during treatment means success. Traditional flow cytometers can quantify tumor cells from a blood sample, but they are as large as a washer/dryer combo, can cost more than $300,000, and produce results only after several hours. By contrast, the inexpensive, shoebox-size PoCyton, by the Fraunhofer Institute for Chemical Technology (ICT-IMM; Mainz, Germany), works about 20 times faster and its automated measurements need no calibration.

Flow cytometry involves injecting fluorescent dye into the blood; the dye molecules bind to tumor cells, leaving all other cells unmarked. While adding dye to a blood sample is typically a manual process, the PoCyton automates it. Within the system, the tagged blood is funneled through a narrow focal area, causing suspended cells to pass in front of a laser spot detector one by one. The light causes the cancer cells to fluoresce, enabling the device to detect and count them. This narrow passage is the key to the PoCyton process: its geometry ensures that every object flowing past the detector is registered, and no cell is hidden behind another. This is critical because even in a severely sick patient, only five in approximately one billion suspended objects in a 10 mL sample of blood is a CTC. The researchers report that the device provides adequate sensitivity, and they are now working to create a fully functional prototype.

Besides counting of CTCs, the PoCyton could enable detection of legionella bacteria in drinking water, which can cause Legionnaire's disease.