Distinguished Professor Takeshi Imai In a paper published in Nature Methods on March 12, a research team led by Kyushu University introduces a new reagent called SeeDB-Live. It uses albumin\u2014a common protein in blood serum\u2014to clear tissue while preserving cellular function. The technique allows scientists to see deeper, brighter structures in both brain slices in a dish and living mice, reaching neural activity that was previously out of sight.<\/p>\n \u201cThis is the first time tissue clearing has been achieved without altering its biology,\u201d says Takeshi Imai, Distinguished Professor at Kyushu University’s Faculty of Medical Sciences and the study\u2019s senior author.<\/p>\n \u201cSeeDB-Live can pave the way for deep-tissue live imaging, both ex vivo and in vivo,\u201d adds the study\u2019s first author, Assistant Professor Shigenori Inagaki of the same faculty.<\/p>\n How to see deeper into the living brain?<\/b><\/p>\n Complex functions like memory and thought arise from real-time communication between cells deep in the brain. Although slices preserve some activity, understanding normal brain dynamics requires imaging the living brain.<\/p>\n Making the opaque brain transparent is one solution, and it begins with optics.<\/p>\n Consider glass marbles: clearly visible in air but nearly disappear in oil. This is because light refracts and scatters when passing between materials with different refractive indices, and brain tissue behaves the same way. Lipids and other cellular components create tiny mismatches, scattering light, hiding deeper structures. Reduce them, and light travels uniformly.<\/p>\n Through systematic experiments, Imai\u2019s team found that living cells become most transparent when the refractive index of the extracellular solution is adjusted to 1.36\u20131.37.<\/p>\n With a precise target in hand, the team needed a non-toxic way to reach it while maintaining osmotic balance, so that cells neither swell nor shrink. They previously tried natural substances such as sugar, but these required high concentrations that increased osmotic pressure and dehydrated cells.<\/p>\n As osmotic pressure depends on the number of molecules, the team turned to large spherical polymers. Their greater size means fewer are required to raise the refractive index, which adjusts optical performance without overwhelming the cells. However, despite screening nearly 100 compounds, the answer refused to come.<\/p>\n A blood protein is the surprising key to brain transparency<\/b><\/p>\n The turning point came unexpectedly.<\/p>\n Late one night, Inagaki returned to a simple idea: proteins are polymers. He grabbed a bottle of bovine serum albumin (BSA), a common blood-derived laboratory reagent, which, to his surprise, showed the lowest osmotic pressure at the desired refractive index.<\/p>\n \u201cI tested it three or four times before I believed it,\u201d Inagaki recalled. Alone in the lab that night, he let out a shout of excitement. \u201cOf all things, we never expected it would come down to this.\u201d<\/p>\n By adding albumin to the culture medium to match the refractive index inside cells, the team developed a live-tissue clearing solution, which they named SeeDB-Live.<\/p>\n \u201cDuring the development of SeeDB-Live, we found that neurons are extremely sensitive to ion concentrations, and it took us enormous effort to get the formulation right. Thanks to that fortunate night alone in the lab, I helped myself to an expensive, high-purity BSA I wouldn’t normally dare use,” Inagaki adds with a laugh.<\/p>\n SeeDB-Live renders mouse brain slices transparent within one hour of immersion. When combined with a calcium indicator, the normal neuronal firing deep inside the tissue was illuminated in the transparent brain slice. When applied to living mouse brains, fluorescence signals from deep neurons became three times brighter.<\/p>\n This opens up clear views of layer 5 of the cerebral cortex, where richly branched neurons help reveal how the brain processes information and translates neural activity into action. Before SeeDB-Live, crisp images at this depth were difficult to obtain with conventional strategies.<\/p>\n Moreover, as the extracellular fluid washes out SeeDB-Live within hours, the tissue transparency returns to its original state. Because the method causes no permanent changes, the same mouse can be imaged repeatedly to track brain activity over time.<\/p>\n \u201cAlbumin is abundant in blood and highly soluble, which makes it well-suited for clearing,\u201d notes Imai. \u201cIt was an accidental discovery, but looking back, it feels almost natural. What evolution has shaped over millions of years is truly impressive.<\/p>\n A decade after saying \u201cimpossible\u201d<\/b><\/p>\n SeeDB-Live demonstrates the first non-invasive optical clearing that greatly increases imaging depth and enables observation of tissue-wide dynamics.<\/p>\n Researchers expect it to enhance deep fluorescence imaging for understanding brain integrative functions. It may also help evaluate 3D tissues and brain organoids for drug discovery research.<\/p>\n The team notes that although SeeDB-Live works well for brain tissue, biological barriers limit delivery to other organs, and accessing the brain still requires a surgical window that can cause stress and reduce efficiency.<\/p>\n \u201cI feel we have not yet fully materialized its potential,\u201d Inagaki says, adding that future efforts will focus on less invasive delivery methods to improve penetration for deeper imaging and better functional analysis of brain activity.<\/p>\n For Imai, the achievement marks the culmination of more than a decade of work. After developing SeeDB in 2013 and SeeDB2 in 2016 for fixed tissue, he was repeatedly asked whether live tissue clearing was possible.<\/p>\n \u201cThat question came to me about a hundred times, and each time I answered \u2018impossible,\u2019\u201d Imai reflects. \u201cBut ten years later, here we are. When something seems unachievable, if you keep thinking about it, you may eventually find a way.<\/p>\n Takeshi Imai, Distinguished Professor <\/a>
\nFaculty of Medical Sciences<\/span><\/strong>
\nFukuoka, Japan\u2014Making a living brain transparent and watching its neurons fire without disturbing their function\u2014sounds like science fiction, doesn’t it? Yet the solution may already exist within our own bodies.<\/p>\nResearch-related inquiries<\/h4>\n
\nFaculty of Medical Sciences<\/a>
\nContact information can also be found in the full release<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"Researchers at Kyushu University have developed a new tissue-clearing reagent, SeeDB-Live, which enables repeated, reversible, and real-time imaging of the living brain at greater depth and clarity Distinguished Professor Takeshi Imai Faculty of Medical Sciences Fukuoka, Japan\u2014Making a living brain transparent and watching its neurons fire without disturbing their function\u2014sounds like science fiction, doesn’t it? […]","protected":false},"author":7,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[23],"tags":[43],"acf":[],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/sdgs.kyushu-u.ac.jp\/en\/wp-json\/wp\/v2\/posts\/30632"}],"collection":[{"href":"https:\/\/sdgs.kyushu-u.ac.jp\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/sdgs.kyushu-u.ac.jp\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/sdgs.kyushu-u.ac.jp\/en\/wp-json\/wp\/v2\/users\/7"}],"replies":[{"embeddable":true,"href":"https:\/\/sdgs.kyushu-u.ac.jp\/en\/wp-json\/wp\/v2\/comments?post=30632"}],"version-history":[{"count":5,"href":"https:\/\/sdgs.kyushu-u.ac.jp\/en\/wp-json\/wp\/v2\/posts\/30632\/revisions"}],"predecessor-version":[{"id":30892,"href":"https:\/\/sdgs.kyushu-u.ac.jp\/en\/wp-json\/wp\/v2\/posts\/30632\/revisions\/30892"}],"wp:attachment":[{"href":"https:\/\/sdgs.kyushu-u.ac.jp\/en\/wp-json\/wp\/v2\/media?parent=30632"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/sdgs.kyushu-u.ac.jp\/en\/wp-json\/wp\/v2\/categories?post=30632"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/sdgs.kyushu-u.ac.jp\/en\/wp-json\/wp\/v2\/tags?post=30632"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}