Researchers from Harvard University have made advances in microscopy that for the first time allows the capture of motion of proteins, lipids and water within cells - without the need of attaching them to fluorescent probes. The technique can be used to create videos of molecular motion in living animals, and could one day transform medical imaging - even allowing surgeons to see specific molecules in tumours as they operate.

The new technique is based upon stimulated Raman scattering (SRS) microscopy - and has been a focus of X. Sunney Xie's research for more than a decade. The research is published in the December 3rd Edition of the journal Science.

Because SRS microscopy works by detecting molecules through the characteristic vibrations of their chemical bonds, it does not require fluorescent labeling - whose bulk often interferes with the molecules natural movements and biological function. However, previous incarnations of SRS were limited by slow imaging times - with a rate of about one image per minute, it was far too slow for use in a live animal.

The groups current work greatly improves detection of signals — backscattered by tissues in the body — by rearranging photodetectors to surround a small aperture through which a beam of light is directed at the tissue being examined. Using this approach, the scientists were able to collect and analyze almost 30 percent of the laser light directed at a biological sample, a more than 30-fold increase over previous SRS microscopy.

“We were able to speed the collection of data by more than three orders of magnitude, attaining video-rate imaging,” said Xie.

Click here to view SRS video capture of real-time blood flow.

"When we started this project 11 years ago, we never imagined we’d have an amazing result like this,” says Xie, professor of chemistry and chemical biology at Harvard. “It took MRI more than 30 years to reach patients, but we’re already looking forward with great anticipation to applications of SRS microscopy in hospitals. It’s now clear that stimulated Raman scattering will play an important role in the future of biological imaging and medical diagnostics.”

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