Near Infrared Helps Bioimaging Go The Distance

Scientists in Japan have invented a near-infrared dye that can be used to investigate the dynamics of living organisms, tissues, cells and molecules.

AsianScientist (Sep. 5, 2018) – A team of researchers in Japan has invented a photostable fluorescent labeling agent that allows long term bioimaging in the near infrared region. Their work is published in Angewandte Chemie International Edition.

Fluorescence imaging is a technique where a specific protein or cell organelle is labeled with a fluorescent probe, making it possible to visualize processes and structures in organisms under a microscope. Although many fluorescent labeling agents, such as fluorescent proteins and small fluorescent organic molecules have been developed, most of them require illumination in the visible region of the light spectrum.

The disadvantages of using visible light arise from the high energy of these illumination sources, which may cause damage to living samples during prolonged imaging. In addition, when the samples are excited with visible light, autofluorescence from the samples themselves tend to interfere with the signals from the fluorescent probes. Furthermore, visible light does not penetrate deeply into biological tissue, limiting the depth of imaging.

To overcome these limitations, researchers at Nagoya University, RIKEN and Ehime University in Japan have developed a near infrared (NIR) emitting photostable fluorescent dye called PREX 710 (photo-resistant xanthene dye which can be excited at 710 nanometers). NIR radiation, which has a longer wavelength and thus lower energy compared to visible light, is less damaging to living tissue.

The team demonstrated that PREX 710 could be used for single molecule fluorescent imaging under physiological conditions. The high photostability of PREX 710 enables repeated imaging, and its specific light absorption/emission properties in the NIR region allows multicolor imaging when used with other fluorescent dyes.

Moreover, by linking PREX 710 NHS ester to the polysaccharide dextran, the researchers succeeded in carrying out three-dimensional deep in vivo imaging of blood vessels in mice brains. This was possible due to the high chemical stability of PREX 710 within the blood stream, as well as the ability of NIR radiation to penetrate further into biological tissue.

“We were pleased to demonstrate that PREX 710 and its derivatives are useful tools for the investigation of the dynamics of living organisms, tissues, cells and molecules,” said Associate Professor Masayasu Taki of Nagoya University.

“We are currently working on developing other NIR fluorescence probes that could be used for staining specific proteins as well as examining live structures and processes in more depth. We hope that this will lead to the visualization and elucidation of various phenomena in living systems.”

The article can be found at: Grzybowski et al. (2018) A Highly Photostable Near-infrared Labeling Agent Based on a Phospha-rhodamine Enables Long-term and Deep Imaging.


Source: Nagoya University; Photo: Pexels.
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