GFP helps turn single cell into “living laser”

Compiled by BioPhotonics staff

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 beam.

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 material.

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: 10.1038/nphoton.2011.122).

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.