Liver cells in the mouse contain the fluorescent protein iRFP. The mouse was exposed to near-infrared light, which has caused iRFP to emit light waves that are also near-infrared. The fluorescent near-infrared waves passed readily through the animal’s tissues to reveal its brightly glowing liver.
BRONX, US: Researchers at Albert Einstein College of Medicine of Yeshiva University have developed the first fluorescent protein that enables scientists to clearly ‘see’ the internal organs of living animals without the need for a scalpel or imaging techniques that can have side effects or increase radiation exposure.
The new probe could prove to be a breakthrough in whole-body imaging - allowing doctors, for example, to noninvasively monitor the growth of tumours in order to assess the effectiveness of anti-cancer therapies. In contrast to other body-scanning techniques, fluorescent-protein imaging does not involve radiation exposure or require the use of contrast agents. The findings are described in the July 17 online edition of Nature Biotechnology.
For the past 20 years, scientists have used a variety of coloured fluorescent proteins, derived from jellyfish and corals, to visualize cells and their organelles and molecules. But using fluorescent probes to peer inside live mammals has posed a major challenge. To overcome that roadblock, the laboratory of Vladislav Verkhusha, PhD, Associate Professor of anatomy and structural biology at Einstein and the study’s Senior Author, engineered a fluorescent protein from a bacterial phytochrome (the pigment that a species of bacteria uses to detect light). This new phytochrome-based fluorescent protein, dubbed iRFP, both absorbs and emits light in the near-infrared portion of the electromagnetic spectrum - the spectral region in which mammalian tissues are nearly transparent.
The researchers targeted their fluorescent protein to the liver - an organ particularly difficult to visualize because of its high blood content. The mice were exposed to near-infrared light and it was possible to visualize the resulting emitted fluorescent light using a whole-body imaging device. Fluorescence of the liver in the infected mice was first detected the second day after infection and reached a peak at day five and it was nontoxic.
“Our study found that iRFP was far superior to the other fluorescent proteins. iRFP produced a far brighter image. We believe it will significantly broaden the potential uses for noninvasive whole-body imaging,” said Grigory Filonov, PhD, a Postdoctoral fellow in Dr Verkhusha’s laboratory at Einstein, and the first author of the Nature Biotechnology paper.
The study, ‘Bright and stable near-infrared fluorescent protein for in vivo imaging,’ was published in the July 17 online edition. Other Einstein researchers involved in the study were Kiryl Piatkevich, Li-Min Ting, Jinghang Zhang and Kami Kim. This research was carried out at the Gruss Lipper Biophotonics Centre and supported by grants from the National Institute of General Medical Sciences of the National Institutes of Health.
(C) 2011 Albert Einstein College of Medicine, Yeshiva University News