The information about (3-glycidoxypropyl) trimethoxysilane, or 3GTMO, came to
our attention in mid-1999 via the Microscopy Listserver. It is a good example
of how the internet disseminates valuable information about new materials for
new procedures. We are grateful for those who shared their experiences with
those on the listserver.
The diamond knife thin sectioning of "hard" materials with relative smooth
surfaces, lacking the surface convolutions, or even surface porosity, that
enable good adhesion between the species being embedded and the embedding
resin. This system was designed for those working with an epoxy based system
(such as SPI-Pon™ 812) and who
were finding that their embedded samples were being "popped out" by the knife
of the microtome. People experiencing this kind of problem cover the range
of life science workers to materials science workers, from those trying to
embed smooth surfaced seeds (even weevils!) for immuno electron microscopy to
those studying uniform metal spheres, glass spheres, certain inorganic pigment
systems, just to name a few. For those wanting to search the archives of the
listserver postings, search on July 8, 1999 where a summary was posted by
Prof. Tom Phillips, University of Missouri, Columbia.
The role of 3GTMO is to serve as a "coupling agent" or "adhesion promoter"
between the epoxy and the features being embedded. Although 3GTMO was
originally developed as an agent to promote adhesion for epoxy systems, we do
not know about its efficacy for other "sister" resins such as "Epon®
/Araldite®" type systems or even acrylic based systems such as
SPI-Chem™ Low Acid GMA or
Lowicryl® resins, for example.
So far as we know, there has never been any interference with the use of 3GTMO when samples are being osmium tetroxide stained.
We believe the first publication describing the use of 3GTMO was Swab, P. & Klinger, R.E. Preparation
of multilayer optical coatings for TEM cross-sectional microanalysis by ultramicrotomy, Mat. Res. Soc.
Proceedings 115: 229-234(1988). The approach was again published by V. A. Lindley in Microscopy
Research and Technique 21, 355-360 (1992), "A New Procedure for Handling Impervious Biological Specimens".
The papers recommend a pretreatment with 3GTMO with subsequent embedding in
a Spurr epoxy formulation. The "soaking
solution" is made up of a 1% solution of 3GTMO in a 50/50 water/alcohol
solution with the treatment time being on the order of one hour. Then "dab
off" excess liquid on a filter paper or lint free wiper and embed as normal.
We feel we can safely say that the benefits of 3GTMO will be realized
with any TEM embedding epoxy including our own SPI-Pon 812 embedding resin kit.
The material, 3GTMO is quite inexpensive, however, even 25 gms is essentially
a life time supply for most researchers, therefore we have made it available
in small quantities. Upon request, we will quote on larger size bottles.
Bulk quantities available also.