ABSTRACT
Chemical tissue clearing agents can be coarsely grouped into lipophilic solvents and water-based clearing cocktails. Focus Clear was first mentioned in a publication dealing with the mapping of brain neuropils in the cockroach Diploptera punctata and was soon patented under the United States patent number 6,472,216 B1. A setup for CLARITY comprises a specimen chamber containing the sample to be cleared and two platinum electrodes for electric field generation, a reservoir for the sodium dodecyl sulphate (SDS)-buffer solution, and a pump for circulating the SDS lipid extraction buffer in a closed circuit. Chemical tissue clearing is a field of research which is presently undergoing a fast evolution. Lipophilic clearing agents usually penetrate biological tissues more easily than hydrophilic clearing substances, since they solubilize the lipids forming the cell membranes. Therefore, the clearing process with these substances is generally fast, rarely taking more than a few days even with large samples, e.g. entire brains from rats.
