In DepthBiophysics

Tiny built-in lasers light up living cells

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Science  31 Jul 2015:
Vol. 349, Issue 6247, pp. 460-461
DOI: 10.1126/science.349.6247.460

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Two groups of researchers have independently fashioned tiny lasers within living cells. They may sound like weapons for Ant-Man's next nemesis, but the microscopic lasers could greatly improve biologists' ability to track the movement of individual cells. The lasers consist of spheres of plastic several micrometers in diameter that are doped with a fluorescent dye and that the cells absorb through a process called endocytosis—although one group also used injected droplets of dyed oil and naturally occurring fat globules. When the fluorescent molecules are excited, a sphere rings with light of specific wavelengths, just as an organ pipe rings with sound at a fundamental frequency and its overtones. If the intensity of the light exceeds a certain threshold, the light itself stimulates the dye to radiate far more intensely, creating a laser. Because each bead shines distinctive wavelengths, the built-in lasers can be used to identify and track individual cells. They might be put to use right away to track cultures of immune cells as they migrate in response to chemical stimuli. If they can be used in living tissue, they might eventually track cells in developing embryos, the immune system, or cancerous tumors.