Sugar solution makes bio-tissues transparent

03 Jul 2013

Enables novel optical scanning approach to biological analysis.

Japanese researchers at Riken University, Tokyo, have developed a new sugar and water-based solution that turns biological tissues transparent in just three days - without disrupting the shape and chemical nature of the samples.

Combined with fluorescence microscopy, this new approach has enabled them to obtain detailed optical images of a mouse brain at an unprecedented resolution.

The team from the RIKEN Center for Developmental Biology first reported their finding in the journal Nature Neuroscience.

In recent years, teams in both the USA and Japan have reported a number of new techniques to make biological samples transparent, which have enabled researchers to look deep into biological structures such as the brain [of a mouse].

“However, these clearing techniques have limitations because they induce chemical and morphological damage to the sample and require time-consuming procedures,” said Dr. Takeshi Imai, who led the RIKEN study.

Sweet success

SeeDB, an aqueous fructose solution, which Imai developed with colleagues Drs. Meng-Tsen Ke and Satoshi Fujimoto, is said to overcome these limitations.

Using SeeDB, the researchers have been able to make mouse embryos and mouse brains transparent in just three days, without damaging the fine structures of the samples, or the fluorescent dyes they had injected in them.

The researchers could then visualize the neuronal "circuitry" inside the mouse brain, at the whole-brain scale, under a customized fluorescence microscope without making mechanical sections through the brain.

They have been able to describe the detailed wiring patterns of commissural fibers connecting the right and left hemispheres of the cerebral cortex, in three dimensions, for the first time.

Dr. Imai and colleagues report that they were also able to visualize in three dimensions the wiring of mitral cells in the olfactory bulb, which is involved the detection of smells, at single-fiber resolution.

"Because SeeDB is inexpensive, quick, easy and safe to use, and requires no special equipment, it will prove useful for a broad range of studies, including the study of neuronal circuits in human samples," explain the researchers.

About the Author

Matthew Peach is a contributing editor to optics.org.