Two people Malte Gather (Harvard Medical School) and Seok Hyun Yun (MIT) are now making biological cells to emit. Yes, they have demonstrated LASER from biological cells. In the paper published on 12 June 2011 in the journal of Nature Photonics, titled “Single Cell Biological Lasers”, they inform us about the discovery in the following words.
” … lasing has so far relied on artificial or engineered optical gain materials, such as doped crystals, semiconductors, synthetic dyes and purified gases. Here, we show that fluorescent proteins in cells are a viable gain medium for optical amplification, and report the first successful realization of biological cell lasers based on green fluorescent protein (GFP). We demonstrate in vitro protein lasers using recombinant GFP solutions and introduce a laser based on single live cells expressing GFP. On optical pumping with nanojoule/nanosecond pulses, individual cells in a high-Q microcavity produce bright, directional and narrowband laser emission, with characteristic longitudinal and transverse modes. Lasing cells remained alive even after prolonged lasing action. Light amplification and lasing from and within biological systems pave the way to new forms of intracellular sensing, cytometry and imaging.”
We are aware of the difference between a generic light and a laser. It’s just like a crowd of generic people and a crowd of clones. The photons making up a laser are identical copies of each other having same color, direction and phase, thereby producing a monochromatic, directional and coherent beam of light. The phenomenon of stimulated emission is necessary for the production of laser. When a molecule is in excited state, it has some extra energy. The molecule can relax by emitting the extra energy in the form of photon which further excites the interacting molecules. These excited molecules relax, omitting more photons and the process carries on till a heavy population of such photons is achieved. These photons are kept in between two mirrors to build up the desired laser beam.
Gather and Yun employed Green Fluorescent Protein (GFP), a specific protein produced in some cells, to demonstrate lasing effect. GFP is excitable by light and can be used to produce single cell laser. It was discovered in 1962 in a species of bio-luminescent jellyfish and it was after thirty years that scientist found out to use GFP to image cellular structures by genetically modifying the cells. The beautiful images of the cellular anatomy we have today, are courtesy to this GFP. It is the same protein which resulted in Nobel Prize in Chemistry in 2008.
The following demonstration of the first bionic laser represents the shrinking of the gap between the biological and physical communities. Interesting questions arise after this discovery. If lasers can be generated inside a body, it would possibly change the current method of medical diagnosis and treatment. Plasmonic nanoparticles and nano-antennas with tailored optical properties may provide the required cavity for the lasers. The environment sensitive nature of these lasers may result in obtaining more accurate knowledge about the performance, functioning and structure of cells and proteins. It also revealed and interesting fact that the lasers cannot be just optoelectronic based devices. These may be integrated into any living organism.
1) Gather, Malte C., and Seok Hyun Yun. “Single-cell biological lasers.” Nature Photonics 5, no. 7 (2011): 406-410
2)”Bionic Lasers” in Optics and Photonics Focus published in September 2011