Separating live and dead leukaemia cells using an electrical technique could provide an automated system for early cancer detection, say American scientists. 

Dielectrophoresis (DEP) uses an electrical field to separate particles according to their differing electrical properties. This can be applied to live and dead cells as dead cell membranes have higher conductivity as they are more permeable than live ones and allow ions to leak out, explains Rafael Davalos at Virginia Polytechnic Institute and State University. 

But conventional DEP requires direct contact between the electrodes and sample fluid, which leads to problems such as contamination and bubble formation. Davalos has developed a new approach to the technique where the electrodes are separated from the sample by a thin barrier to avoid these problems. In contactless-DEP, the electrodes are inserted into two conductive microchambers, which are separated from the sample channel by thin insulating barriers. 

Davalos says the ability to separate cells in this way is 'incredibly useful in research and medical settings where the investigation of a specific type of cell is hindered by the presence of many other cells.' 

David Holmes, an expert in cell sorting and DEP at University College London, UK, says '[Davalos' method] avoids many of the problems associated with electrodes in contact with the fluid, and has promise in the area of cell separation.' 

Although the prototype devices have achieved high efficiency, Davalos says he believes further improvement in the design is possible and the simple and inexpensive device fabrication could make it suitable for mass production. The team say that optimising the device could allow selective separation of cells from biological fluids for cancer diagnosis and differentiation of cells at different stages of the disease. 

Erica Wise 

Enjoy this story? Spread the word using the 'tools' menu on the left or add a comment to the Chemistry World blog.