Research team achieves first 2-color STED microscopy of living cells

WASHINGTON, Aug. 17–Researchers are able to achieve extremely high-resolution microscopy through a process known as stimulated emission depletion (STED) microscopy. This cutting-edge imaging system has pushed the performance of microscopes significantly past the classical limit, enabling them to image features that are even smaller than the wavelength of light used to study them. They are able to achieve this extreme vision by using a single-color fluorescent dye that absorbs and releases energy, revealing cells and cellular components (such as proteins) in unprecedented detail.

Current applications of STED microscopy have been limited to single color imaging of living cells and multicolor imaging in “fixed” or preserved cells. However, to study active processes, such as protein interactions, a two-color STED imaging technique is needed in living cells.

Live cell two-color STED time series of HEK293 cells labeled with EGF-CLIPf-ATTO647N (magenta) and EGFR-SNAPf-Chromeo494 (green). Data has been normalized to correct for bleaching. The shown images have been cropped from the original raw data. Scale bar = 1 ¼m. (Credit: Pellett et al., Biomed. Opt. Express 2, 2364-2371 (2011).)

This was achieved for the first time by a team of researchers from Yale University, as reported in the August issue of the Optical Society’s (OSA) open-access journal Biomedical Optics Express. The key to their success was in overcoming the challenges in labeling target proteins in living cells with dyes optimal for two-color STED microscopy. By incorporating fusion proteins, the researchers were able to improve the targeting between the protein and the dye, effectively bridging the gap. This allowed the researchers to achieve resolutions of 78 nanometers and 82 nanometers for 22 sequential two-color scans of two proteins – epidermal growth factor and epidermal growth factor receptor – in living cells.

The researchers expect that using this and other novel approaches will expand live cell STED microscopy to three and more colors, enabling 3-D imaging.

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Paper: “Two-color STED microscopy in living cells,” Biomedical Optics Express, Pellett et al., Volume 2, Issue 8, pp. 2364-2371. www.opticsinfobase.org/boe/abstract.cfm?URI=boe-2-8-2364

About Biomedical Optics Express

Biomedical Optics Express is OSA’s principal outlet for serving the biomedical optics community with rapid, open-access, peer-reviewed papers related to optics, photonics and imaging in the life sciences. The journal scope encompasses theoretical modeling and simulations, technology development, and biomedical studies and clinical applications. It is published by the Optical Society and edited by Joseph A. Izatt of Duke University. Biomedical Optics Express is an open-access journal and is available at no cost to readers online at www.OpticsInfoBase.org/BOE

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Uniting more than 106,000 professionals from 134 countries, the Optical Society (OSA) brings together the global optics community through its programs and initiatives. Since 1916 OSA has worked to advance the common interests of the field, providing educational resources to the scientists, engineers and business leaders who work in the field by promoting the science of light and the advanced technologies made possible by optics and photonics. OSA publications, events, technical groups and programs foster optics knowledge and scientific collaboration among all those with an interest in optics and photonics. For more information, visit www.osa.org.

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