Compiled by BioPhotonics staff
BOSTON – For the first time, a single living cell has been genetically engineered to produce
nanosecond pulses of laser light.
The “living laser,” developed by two researchers at
the Wellman Center for Photomedicine at Massachusetts General Hospital, is a single
cell genetically engineered to express green fluorescent protein – originally
found in a species of jellyfish – that amplifies photons into a visible laser
Lasers have used synthetic gain materials such as gases, crystals
and dyes to amplify photon pulses. Now the scientists are using GFP as the gain
Schematic of a living laser. When a single biological
cell genetically programmed to produce GFP is placed inside an optical resonator
consisting of two parallel mirrors separated by 20 μm, the cell can generate
green laser light.
To determine GFP’s potential for generating light, the team
assembled a device consisting of a 1-in.-long cylinder, with mirrors at each end,
filled with a solution of GFP in water. The researchers estimated the concentration
of GFP required to produce the laser effect after confirming that the solution could
amplify input energy into brief pulses of laser light. Using the information, they
developed a line of mammalian cells that express GFP at the required levels.
The cellular laser was assembled by placing the single GFP-expressing
cell, just 15 to 20 μm in size, into a microcavity that consisted of two highly
reflective mirrors spaced 20 μm apart. The scientists observed not only that
the cell-based device produced pulses of laser light but also that its spherical
shape acted as a lens, refocusing the light and inducing emissions of laser light
at lower energy levels than are required for the solution-based device. The cells
used in the lasing process survived and continued producing hundreds of laser light
pulses. The findings were reported in the June 30 issue of Nature Photonics (doi:
Microscope image of a single-cell living laser in action. The irregular internal structure
of the GFP-expressing cell causes the apparently random pattern of laser light emission.
Courtesy of Nature Photonics and Malte Gather, Wellman Center for Photomedicine,
Massachusetts General Hospital.
Offering a new way to analyze the properties of large numbers
of cells almost instantaneously, the technique could be useful for photodynamic
therapies or novel forms of imaging, the scientists noted.
They are hopeful that their findings will bring optical communications
and computing, currently done with inanimate electronic devices, into the realm
of biotechnology. Future work will include proving the technique useful for interfacing
electronics with biological organisms, as well as implanting a structure equivalent
to the mirrored chamber right into a cell.