Medical research: Clearing blocked capillaries with light

A non-invasive technique to trap, or move, cells in living mice has been reported in Nature Communications this week. The method, based on infrared optical tweezers, can restore blood flow in mice by clearing blocked capillaries.

Optical tweezers are focused laser beams and are widely used for biophysical measurements of single molecules in controlled environments such as test tubes. However, they have not previously been used to manipulate cells in living animals. Yin-Mei Li and his team focus infrared lasers on subdermal capillaries in mouse ears, which allows them to stop, and release, passing red blood cells by changing the intensity of the laser. They use this technique to remove individual red blood cells from a clump that blocked a capillary so that blood flow is restored.

The authors noted that the application of these infrared optical tweezers is currently limited to subdermal capillaries due to the relatively weak tissue penetration of focussed light. Further improvements would therefore be needed in order for this approach to work with wider blood vessels or more complex blood clots.