Malte Gather / Nature Photonics
A human kidney cell produces green laser light inside a resonator.
Physicists and molecular biologists have created the world's first biological laser, with live, glowing kidney cells at its core.
At the heart of a laser is a substance that can absorb, amplify and emit light in a single focused beam. This role has been played by a string of characters over the years: semiconductors, crystals, dyes and even gases. Until now, living cells weren't part of that cast lineup. There's a good reason for that: Most living things, with the exception of some bioluminescent jellyfish, don't naturally trap or emit light.
But recently, other organisms have acquired the ability to shine. The researchers behind these glow-in-the-dark animals owe their thanks to Osamu Shimomura, who extracted the green fluorescence protein and the genes that make GFP from the glowing guts of those jellyfish. (Coincidentally, he started work on the bioluminescent crystal jellyfish in 1960 — the same year that the laser was invented.)
Since then, molecular biologists have gone gaga over the GFP gene and other fluorescence genes. They use them as visual signals indicating that the other genes they study have been successfully transferred into different organisms (such as cats and dogs). The ever-expanding popularity of fluorescence genes among molecular biologists earned its discoverers a shiny Nobel in 2008. Now the GFP gene itself is stealing the spotlight.
"Almost any organism, from bacteria to higher mammalians, can be programmed to synthesize such luminescent proteins, so we wondered if GFP could be used to amplify light and build biological lasers," Malte Gather and Seok Hyun Yun, the two physicists behind the "biolaser," wrote in a Q&A interview with Nature Photonics. The journal published their paper online on Sunday.
Malte Gather and Seok Hyun Yun are the inventors of the biological laser.
The researchers reprogrammed a line of human embryonic kidney cells with an enhanced version of the GFP gene. Then they sandwiched those cells between highly reflective mirrors and pulsed a blue light through the chamber.
In their optically active compartment, the cells absorbed and re-emitted a laser-worthy green light for several minutes. The mirrors amplified the light to create a coherent beam, just as they do in non-biological lasers.
The cells survived for a few hours after the lasing ordeal, and seemed to be actively producing and reabsorbing the green fluorescence protein. This could mean that, unlike regular lasers which wear out with use, "the laser can self-heal," they told Nature Photonics.
The two physicists are now working on ways to tweak the setup so that it can be used as a living imaging tool. Such lasers may shed new light, so to speak, on biological processes within the cell, Gather told me: "The pattern of the laser light seems to carry information about the insides of the cell."
Biolasers could also have medical applications. Some treatments, such as photodynamic therapy for cancer patients, use external lasers to stimulate drugs to be released close to a tumor. "You have a drug that attacks a tumor when you apply light," Gather said. "Using a laser light force from the inside would make this more efficient."
Ultimately, the researchers want to free the lasing cell from its optical chamber, and somehow include tiny reflective mirrors within the cell itself. "For medical applications, that would be crucial," Gather said.
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