Visikol HISTO Product Information
What is Visikol HISTO?
Visikol® HISTO™ is a novel tissue clearing approach for the 3D visualization of tissues that is non-destructive, rapid, and easy-to-use. Unlike many other clearing agents, Visikol HISTO does not require the removal of cell-membrane lipids, and as such, preserves innate cellular structures. This allows the clearing effect to be reversed, and the tissue to be used in downstream assays. Visikol HISTO does not require embedding into polyacrylamide gel as in CLARITY and related methods, does not require perfusion of the animal tissue, or the use of special fixatives. We have developed an accompanying immunolabeling procedure that is carried out prior to clearing with Visikol HISTO.
How does Visikol HISTO work?
Visikol HISTO renders tissues transparent because the chemical formula allows the reagent to penetrate cell-membranes, permeating the cytosolic and intercellular space. Through this process, the refractive index of the cytosolic and intercellular space is increased to match the refractive index of cell-membranes and proteins (at an RI of 1.47 to 1.51), and when equilibrated, tissues become transparent. Because Visikol HISTO has been carefully optimized to penetrate cellular structure without damaging cells, tissues cleared with Visikol HISTO can be restored to their initial state, allowing follow up assays and histology on three-dimensionally imaged tissues.
Detailed product information can be found for each one of our Visikol HISTO products.
Frequently Asked Questions
1. Does Visikol HISTO quench fluorescent proteins?
Visikol HISTO will significantly reduce FP fluorescence over time, depending upon the specific fluorescent protein, tissue sample, and tissue processing conditions. However, in many cases, clearing is achieved before substantial degradation of the fluorescence signal occurs. A Visikol formula that does not degrade fluorescent proteins is currently under development.
2. Is Visikol HISTO compatible with immunolabeling?
Yes. Unlike other clearing techniques which embed tissue in gel, antibody penetration is rapid, achieving labeling in 1 mm thick brain tissue sections with overnight incubation. See our protocols.
3. Do your protocols facilitate antibody penetration?
Yes, we have adapted the iDISCO antibody penetration techniques for our Visikol HISTO immunolabeling protocols.
4. How does Visikol HISTO compare to other clearing techniques? Is Visikol HISTO just a refractive index matching solution?
This question is often due to a confusion in terms. Methods like CLARITY use a refractive index matching solution (FocusClear, TDE) after processing tissues in order to match the refractive index between the proteins embedded in the gel, with a refractive index at 1.47, and the hydrogel, which has a refractive index closer to water. Visikol HISTO is not intended for this purpose.
Instead, Visikol HISTO is more similar to SeeDB, BABB and 3DISCO/iDISCO, which penetrate tissues and increase the refractive index of the interstitial spaces to match the refractive index of the protein and lipids.
5. How does the toxicity of Visikol HISTO compare to other clearing techniques?
The MSDS for Visikol HISTO can be found here. Visikol HISTO has a similar toxicity profile to commonly used laboratory reagents (e.g. methanol).
6. How do we image samples that have been processed with Visikol HISTO?
The refractive index of Visikol HISTO is in the range of many oil immersion objectives, but since immersion objectives typically have a very short working distance, they are not practical for getting the most out of cleared whole-mount specimens. We have found that just about any 10x-20x air lens will work fine for Visikol HISTO specimens, provided they are mounted in Visikol HISTO-1 or Visikol HISTO-2. Since Visikol HISTO has a refractive index very similar to glass, any lens that is typically used to image cover-slipped specimens will be useful to image Visikol HISTO cleared specimens. As such, most confocal microscopes already are equipped for adequate visualization of tissue cleared using our technique. For optimal results, we suggest utilizing glycerol-matched air lenses.
7. How does Visikol HISTO affect whole tissue?
Tissue samples cleared with Visikol HISTO retain their mechanical strength, and expansion and contraction is less than 5% in whole organs and sections.