Transparent Brain Using Hydrogel Process

Combining neuroscience and chemical engineering, researchers at Stanford University have developed a process that renders a mouse brain transparent. The postmortem brain remains whole -- not sliced or sectioned in any way -- with its three-dimensional complexity of fine wiring and molecular structures completely intact and able to be measured and probed at will with visible light and chemicals.

The process, called CLARITY, ushers in an entirely new era of whole-organ imaging that stands to fundamentally change our scientific understanding of the most-important-but-least-understood of organs, the brain, and potentially other organs, as well.

The research in this study was performed primarily on a mouse brain, but the researchers have used CLARITY on zebrafish and on preserved human brain samples with similar results, establishing a path for future studies of human samples and other organisms.

This new form is created by replacing the brain's lipids with a hydrogel. The hydrogel is built from within the brain itself in a process conceptually similar to petrification, using what is initially a watery suspension of short, individual molecules known as hydrogel monomers. The intact, postmortem brain is immersed in the hydrogel solution and the monomers infuse the tissue. Then, when "thermally triggered," or heated slightly to about body temperature, the monomers begin to congeal into long molecular chains known as polymers, forming a mesh throughout the brain. This mesh holds everything together, but, importantly, it does not bind to the lipids.