MIT Scientists Levitate Cells for Sorting

A new cell sorting method announced by MIT researchers Tuesday involves pushing cells around with a kind of laser beam acting as a "fire hose". The result is a faster, cheaper and easier method of sorting sample cells. The new system could open up types of research that was previously impossible.

The new system could have applications in genetic screening and cloning, clinical testing and diagnosis, disciplines which require selection of cells with specific features for their testing. Up to 10,000 cells on a typical glass slide can be sorted at once. Compared to current methods, the laser beam method offers more precise sorting based on how structures inside the cell respond differently and how quickly to stimulus such as flourescent light.

The system will be featured as the cover story in the December 15 issue of Analytical Chemistry. It was developed by Joel Voldman, an associate professor in MIT's Department of Electrical Engineering and Computer Science, and Joseph Kovac, a graduate student in the department.

"We've been interested in looking at things inside the cell that either change over time, or are in specific places," Voldman said. Separating out cells with such characteristics "can't be done with traditional cell sorting."

The new system can quickly sort cells based on how fast or slowly they respond to flourescent light, whereas before they were sorted first on if they responded at all.

The new system uses a transparent silicone layer containing tiny cavities bonded to the glass slide. The cells settle into these cavities after being dropped onto the slide in a solution. A technician or computerized system can then check the cells in each cavity with the flourescent light. If the right part of the cell responds at the right time it is the type being sorted for and is noted by the computer. Once all the cells have been cheked and their position noted, an the pressure of an inexpensive laser levitates them out of their traps. The solution then flows them off the slide and into a resevoir A flowing fluid then sweeps the selected cells off to a separate reservoir.