Silicone grease in live imaging/3D Printed imaging chambers

I’ve been putting together some 3D-printed coverslip holders as alternatives for labs who don’t want to (or cannot afford to) shell out for Mat-tek dishes. I’m mostly focusing on square coverslips because they are extremely easy to source, and circular coverslips are more expensive, and have had a longer lead time in the past. I’m printing using an SLA printer, rather than an FDM, and I’ve been reasonably happy with the results so far!

I’m struggling to come up with a way to seal the interfaces between coverslips and the 3D printed structure, however. Commercial alternatives use little silicone/rubber gaskets or o-rings, that are squeezed into the structure by magnets in the main body. This isn’t necessarily a problem for round coverslips, as circular gaskets are ten a penny, but square gaskets are more problematic! Maybe I’ll end up cutting my own.

I need to ask if anyone has any knowledge of Silicone grease being toxic to live cells in regular cell culture media? Given that it’s practically non-soluble in water, I would assume that it’s not, at least over the short term (0-5h). I would love it if anyone had any direct knowledge one way or another, as using vacuum grease is really easy to do as a temporary fix for missing gaskets!

Hi @CMCI ,

Vacuum grease should be fine.

I (and many others) have used vacuum grease to keep 5mm coverslips attached to the metal sample holder for a Betzig / 3i lattice light sheet microscope.

Have you considered using PDMS as a sealant as described in the “Chamber Assembly” methods section from "Customizable Live-Cell Imaging Chambers for Multimodal and Multiplex Fluorescence Microscopy"?

Cheers,
Will

Hi Will,

Thanks for the quick response! I hadn’t seen that paper previously, but it looks interesting. For PDMS sealing, it’s not ideal, as I’m looking to switch coverslips in and out throughout the day as if I were using one of these; for replacing expensive multiwell products though, that’s a nice solution. I guess I could actually just make PDMS gaskets!

Chris

Ah, of course.

Are you finding any toxicity from your resin (after treatment)?

I myself will be trying Mod3D’s designs for chamber + holder as soon as chambers finish printing.

I like that cell culture can happen within the chamber and that swapping coverslips should be as simple as lifting the chamber up and replacing it with another.

Mod3D pre-print

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Hi @CMCI,

I am trying similar with SLA printed baths. I’ve attached an image of a first attempt using soft polyurethane foam ( 4790-92-12039-04 P, from the website Parafix). The coverslip is sandwiched between the foam and a printed washer that get screwed in place (although magnets are a good idea). I’ve done limited testing but it seems to be watertight without needing grease. Ultimately this design didn’t work for me because the washer was too thick for the working distance of my objective which limited the FOV. I’m going to remake the washer in a square shape (easier to cut and machine) out of thin aluminium.

Cheers,
Ewan

Grace Biolabs can custom cut sterile silicone rubber sheets to stick the halves together. Any shape, you just send them a drawing.

I don’t like the idea of vacuum grease as it stinks, and if I were a cell I wouldn’t enjoy growing near the stuff. My plant biologists use plain old vaseline for screening work on Arabidopsis seedlings, or pure lanolin (sheep wool grease). I don’t know what the biocompatibility is with mammalian cells, but enfeebled mutant Arabidopsis didn’t mind vaseline at all, and the lanolin was used with very fast growing pollen tubes, which were also quite happy.

When I made a fully functional disposable system for 48 seedlings on a multiwell plate lid footprint, it worked fine, but cost of goods prevented adoption. PIs are extremely sensitive to price, and $25 for 48 samples proved too high compared to the labor of squeezing 10 strips of vaseline onto a slide, and slapping on a long cover slip. You are competing with round rubber gaskets, on square cover slips; or re-used Lab-Tek frames. Tricky.

I think the cost of MatTek and LabTek is often justified by surface treatment for better cell growth and certified sterility. Also tricky in a home grown design. We found our gaskets could be re-used for mutant screens, but chemical screening would carry-over active drugs, and ethanol sterilization leached into the silicone and slowed growth of the next round. Not accepted.