Researchers from the Albert Einstein College of Medicine in New York have discovered a new fluorescent protein for in vivo imaging that may significantly improve diagnostic abilities of clinicians and impact scientific research. The new protein called iRFP is derived from a bacteria’s light detecting pigment phytochrome and it is both excited by and emits light in the near-infrared light spectrum. This makes it a suitable target for whole body in vivo imaging, and does not require radiation exposure nor contrast agents.
The researchers targeted their fluorescent protein to the liver – an organ particularly difficult to visualize because of its high blood content. Adenovirus particles containing the gene for iRFP were injected into mice. Once the viruses and their gene cargoes infected liver cells, the infected cells expressed the gene and produced iRFP protein. The mice were then 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. Additional experiments showed that the iRFP fluorescent protein was nontoxic.
Abstract in Nature Biotechnology: Bright and stable near-infrared fluorescent protein for in vivo imaging