An identical copy of this information also exists here for internal FreeSurfer and LCN staff: https://partnershealthcare.sharepoint.com/sites/LCN/SitePages/Fomblin.aspx
This page is meant to be a collection of notes on Fomblin with regard to the LCN's standard operating protocol for ex vivo samples.
Background: Fomblin is a name brand fluoropolymer produced by Solvay Specialty Polymers S.p.A. that has been used since 1998 (Huang, G. Y., et al., 1998) as an immersion solution to improve MR-imaging SNR in tissue samples. The fluoropolymer uniquely lack's any MR-signal but has magnetic susceptibility similar to that of tissue, which results in MR-images with high SNR & CNR between the Fomblin and any suspended tissue. Since the use of Fomblin in MR-imaging is still quite young, the impact of the solution on tissue properties is unknown. We are maintaining this wiki page to document the following 5 levels of ex vivo processing with Fomblin to record any personal and literature-based experiences with the solution.
5 levels of the ex vivo procedure where Fomblin can impact tissue:
- Tissue storage
From email archive of Ani Varjabedian (01/05/15): We have been packing brains in Fomblin (specifically fomblin 06/6). Some time before 2012/2013, the lab used a different kind of Fomblin called LC08. It was discontinued, and the RA who was in charge of ordering supplies was advised by the seller & another lab that 06/6 was our best alternative moving forward. Allison Stevens found that the 06/6 had a molecular weight (and therefore and a higher density) of almost 3x as much as LC08. This could be one of the reasons why packing is so much more difficult now.
- All PFPE lubricants have the same basic molecular formula, but differences in branching structure or molecule chain length affect fluidity, temperature range, and weight
Ani spoke to a professional at the company where we buy our Fomblin (Kurt J. Lesker), and found an alternative PFPE lubricant that is very similar to LC08 called Galden HT200 (Galden is just the brand name, like Fomblin). Here is the spec sheets for LC08, HT200 and 06/6.
4kg (4 bottles @ 1kg each)
From email correspondence with Scott Brady from Lesker (12/22/14): He suggests we use Galden HT270 (Part #: HT270-7KG) which they provide to several facilities involved in the similar applications. He attached this informational document on Galden products. Ani from LCN asked why this product was recommended given that (1) The molecular weight of HT270 is 1500 and the stats are much closer to 06/6 than LC08 and (2) the papers Scott attached (including those from Jenn McNab's lab) all cited LC08 as the Fomblin used. To the best of my knowledge (Bram), there was no reply from Lesker.
From email correspondence with Brain Edlow (03/28/17): We were initially using Fomblin LC08 from Solvay Solexis. Solvay Solexis stopped selling Fomblin LC08 a few years ago, so we transitioned to using Kurt J. Lesker products. Initially we used Fomblin 06/6 from Kurt J. Lesker. However, the specific gravity of Fomblin 06/6 was slightly higher than that of LC08, and as a result it was more technically challenging to pack whole brains in this fluid within an air-tight plastic bag for ex vivo MRI. We therefore transitioned to Galden HT200 (Galden is just a brand name of a Fomblin product) because of its lower specific gravity, which has made the brain packing process go more smoothly. I don't believe that anyone in our lab has noticed any differences in the quality of the imaging data acquired with these three slightly different fomblin solutions.
Fomblin could be making the sealer not usable. Make sure to wipe down the sealer strip after every Fomblin packing session.
- Use approx. 1.5kg solution for Lilla's brains
Some studies (Hales, PW et al., 2011) have found that as little as 48-hours of contact with Fomblin has long-lasting effects on tissue properties such as T1 relaxation times.
From Allison Steven's email archive (12/05/14): The Fomblin that we are using has a lot of stuff in it because it was made to work as an industrial grease for vacuum pumps. There is an unrelated part of Fomblin that causes the absence of MR signal. It may be possible for a chemist to start with the fundamentals and make something that works better for brain bag packing.
Hyare et al., 2008
Hyare et al., 2008 found that storing tissue in Fomblin for 2 days prior to MRI had no effect on scan or histology results when compared to matched samples stored in 10% formol-saline.
Synopsis: Formalin-fixed mouse brain tissue placed in Fomblin for 2 days prior to T1, T2, DWI, and MTR scans @ 9.4T produced the same results as formalin-fixed controls placed in 10% formol-saline solution 2 days prior to scanning. Both were scanned in Fomblin. They compared ROI-based quantitative MR measures, anatomical & cellular histology, and immunohistochemical staining.
- Fluorinert has been used in a number of studies. A quick search came back with +5 exvivo studies since 2004 using Fluorinert as an in-scan solution - typically Flourinert FC-77, not FC-3283.
3M Fluorinert Electronic Liquids for Electronics: https://www.3m.com/3M/en_US/company-us/all-3m-products/~/All-3M-Products/Electronics/Chemicals/Chemicals/Fluorinert-Electronic-Liquids/?N=5002385+8709318+8710710+8711017+8736409+8745514+3294857497&rt=r3
Studies using Flourinert: Noristani et al., 2015, Colon-Perez et al., 2015, Kovačević et al., 2004, etc..
The effects of Fomblin on histology were discussed in an email conversation between Nancy Kanwisher, Bruce Fischl, Allison Stevens, and Jean Augustinack (Bram Diamond was also cc'ed) on July 10th, 2018 with regard to Nancy's very important I54 brain.
Jean has found that Fomblin is okay for Nissl and basic histochemistry (myelin, thioflavines, etc). She also mentioned that it works for tau immunohistochemistry but may not work if one's antigen is covered or difficult to get to. That said, washing with a mild detergent (Dawn) after removing the majority of Fomblin has worked well to fix this issue in the past.
To clarify, Jean said that although Fomblin can be helpful for "pretty imaging", sticking with the fixative, typically Formalin, all the way would make less variables.
With regard to Clarity, Kwanghun noted that their lab had not yet investigated "how fomblin incubation affects tissue clearing and other downstream histological analysis" and added that he thinks "it'd be safe to not expose the brain to fomblin considering the importance of the brain".
The history of Perfluorocarbons and MRI: Here is an article that talks a bit about the history of perfluorocarbons in MR: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3051284/
The history of Perfluoropolyethers (Fomblin) and MRI: Here is an ISMRM abstract from a few years ago that talks about fomblin as we know it (perfluoropolyethers): http://cds.ismrm.org/ismrm-2008/files/01719.pdf