El MIT crea imágenes en 3D de células vivasContributed by: Anonymous · Views: 1,226
Contributed by: Anonymous · August 14, 2007 @ 08:30 PM MDT · Views: 1,226
MIT creates 3D images of living cellAnne Trafton, News Office
A new imaging technique developed at MIT has allowed scientists to create the first 3D images of a living cell, using a method similar to the X-ray CT scans doctors use to see inside the body.
Photo / Donna Coveney
From left: Kamran Badizadegan, principal research scientist; Wonshik Choi, postdoc; and Michael Feld, physics professor and director of the MIT Spectroscopy Lab. The three have found a way to create 3D images of the inner workings of cells, as illustrated on monitor in front of them.
Rotating, 3D view of a cervical cancer cell
The technique, described in a paper published in the Aug. 12 online edition of Nature Methods, could be used to produce the most detailed images yet of what goes on inside a living cell without the help of fluorescent markers or other externally added contrast agents, said Michael Feld, director of MIT's George R. Harrison Spectroscopy Laboratory and a professor of physics.
"Accomplishing this has been my dream, and a goal of our laboratory, for several years," said Feld, senior author of the paper. "For the first time the functional activities of living cells can be studied in their native state."
Using the new technique, his team has created three-dimensional images of cervical cancer cells, showing internal cell structures. They've also imaged C. elegans, a small worm, as well as several other cell types.
Image / Michael Feld laboratory, MIT
Images of a cervical cancer cell taken using a new imaging technique developed at MIT. Figures a and b show 3D images of the cell. The green structures represent the nucleolus. The nucleus, not visible in these images, surrounds the nucleolus. The red areas are unidentified cell organelles. Figures c through h show the 2D images from which the 3D images were generated. In these images, each color represents a different range of refractive index.
"You can reconstruct a 3D representation of an object from multiple images taken from multiple directions," said Wonshik Choi, lead author of the paper and a Spectroscopy Laboratory postdoctoral associate.
Cells don't absorb much visible light, so the researchers instead created their images by taking advantage of a property known as refractive index. Every material has a well-defined refractive index, which is a measure of how much the speed of light is reduced as it passes through the material. The higher the index, the slower the light travels.
The researchers made their measurements using a technique known as interferometry, in which a light wave passing through a cell is compared with a reference wave that doesn't pass through it. A 2D image containing information about refractive index is thus obtained.
To create a 3D image, the researchers combined 100 two-dimensional images taken from different angles. The resulting images are essentially 3D maps of the refractive index of the cell's organelles. The entire process took about 10 seconds, but the researchers recently reduced this time to 0.1 seconds.
The team's image of a cervical cancer cell reveals the cell nucleus, the nucleolus and a number of smaller organelles in the cytoplasm. The researchers are currently in the process of better characterizing these organelles by combining the technique with fluorescence microscopy and other techniques.
Image / Michael Feld laboratory, MIT
A 3D image of the nematode C. elegans, taken using a new imaging technique developed at MIT. The scale bar (lower left) is 50 micrometers.
"When you fix the cells, you can't look at their movements, and when you add external contrast agents you can never be sure that you haven't somehow interfered with normal cellular function," said Badizadegan.
The current resolution of the new technique is about 500 nanometers, or billionths of a meter, but the team is working on improving the resolution. "We are confident that we can attain 150 nanometers, and perhaps higher resolution is possible," Feld said. "We expect this new technique to serve as a complement to electron microscopy, which has a resolution of approximately 10 nanometers."
Other authors on the paper are Christopher Fang-Yen, a former postdoctoral associate; graduate students Seungeun Oh and Niyom Lue; and Ramachandra Dasari, principal research scientist at the Spectroscopy Laboratory.
The research was conducted at MIT's Laser Biomedical Research Center and funded by the National Institutes of Health and Hamamatsu Corporation.
Courtesy: MIT news office