June 13, 2011

Single Cell Is The Basis Of Living Laser

Two researchers working for Wellman Center for Photomedicine at Massachusetts General Hospital have developed a laser from a single living cell, by engineering it to produce a light-emitting protein that was first obtained from glowing jellyfish.

The development, set to appear in the journal Nature Photonics, was worked on by researchers Malte Gather, PhD, and Seok Hyun Yun, PhD. They described that flooding the genetically engineered cells with weak blue light caused them to emit directed, green laser light.

The work could improve microscopic imaging and light-based therapies.

Differing from normal light, laser light uses a narrow band of colors, with the light waves all oscillating together in synchrony. Most modern forms of laser light use carefully engineered solid materials to produce lasers in everything from supermarket scanners to DVD players. But this is the first time laser light has been produced in a living cell.

"Since they were first developed some 50 years ago, lasers have used synthetic materials such as crystals, dyes and purified gases as optical gain media, within which photon pulses are amplified as they bounces back and forth between two mirrors," said Yun, co-author of the report. "Ours is the first report of a successful biological laser based on a single, living cell."

The researchers used green fluorescent protein (GFP) as the laser's "gain medium," where light amplification takes place. Cells derived from human kidney cells were genetically engineered to produce GFP. The cells were then placed one at a time between two tiny mirrors, just 20 millionths of a meter across, which acted as the "laser cavity" in which light could bounce many times through the cell.

Upon bathing the cells with blue light, they could be seen to emit directed and intense green laser light. The cells remained alive throughout and after the process. The authors noted in an interview with BBC News that the living system is a "self-healing" laser, adding that if the light-emitting proteins are destroyed in the process, the cell will simply produce more.

"In cellular sensing, we may be able to detect intracellular processes with unprecedented sensitivity," the authors said. "For light-based therapeutics, diagnosis and imaging, people think about how to deliver emission from an external laser source deep into tissue. Now we can approach this problem in another way: by amplifying light in the tissue (itself)."

"Part of the motivation of this project was basic scientific curiosity. In addition to realizing that biological substances had not played a major role in lasers, we wondered whether there was a fundamental reason why laser light, as far as we know, does not occur in nature or if we could find a way to achieve lasing in biological substances or living organisms," said Gather, lead author in the study.

"One of our long-term goals will be finding ways to bring optical communications and computing, currently done with inanimate electronic devices, into the realm of biotechnology," said Gather.

That could be particularly useful in projects requiring the interfacing of electronics with biological organisms. We also hope to be able to implant a structure equivalent to the mirrored chamber right into a cell, which would the next milestone in this research," he noted.

The study was supported by grants from the National Science Foundation and the Korea National Research Foundation.


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