Glycol methacrylate (GMA), otherwise known as 2-hydroxyethyl
methacrylate, is the embedment of choice for both TEM and LM
applications, particularly for hydrated specimens with sensitive
A "one size fits all" approach does not work so well for GMA embedding
because for TEM applications, one needs thin sections, and therefore a
"harder" block is needed, but for LM, one needs thicker sections, and
therefore, the need for a "softer" block. Therefore instead of offering
a single kit with an intermediate hardness (leaving no one with the
optimum hardness), SPI offers two different kits, one specifically
optimized for TEM (to yield a harder block) and another one optimized for
LM (to yield a softer block).
Furthermore, there are a number of advantages of using "low acid" instead
of the more common and lower cost "technical grade" GMA that is
generally provided in kits not specifically being labelled as "low
acid". For example, at the LM level, the use of "low acid" GMA results
in significantly lower background staining. And at the TEM level,
the absence of the acid derivative of the monomer results in less
interaction and problems with curing when high lipids levels are
For TEM applications, the SPI-Chem Low Acid embedding kits can be used to
infiltrate biological tissue and preserve and observe fine structure not
previously subjected to solvent dehydrations. The LM, GMA far
outdistances paraffin or other embedding methods for resolution, clarity,
and contrast in observing thin sections.
For immunogold work, especially in the case of sensitive antigenic sites,
the ability to avoid an alcohol dehydration step altogether represents a
major advantage. The monomer acts as its "own dehydrator", and in fact
won't even work at all if at least some water is present. Often times,
one gets superior results when the sample is not subjected to any alcohol
So far as we know, the SPI-Chem Low Acid GMA kits are compatible with all
reported staining methods and procedures. However, the first time
user should also recognize that the learning curve for using GMA is probably
a bit longer than for other resin systems. Because of that, we are
accumulating a listing of "Frequently Asked Questions" (FAQ's) about the use of low acid GMA.
Infiltration of tissue and monomer can be performed at room temperature
or down to -16° C. The GMA monomer has a viscosity like that
of water, so there are some applications where GMA is the embedment of
choice because it is the only monomer with low enough viscosity to
infiltrate difficult to infiltrate samples. For immunogold work, the
resulting GMA polymer can be "etched" and there are published techniques for doing this.
Even materials science researchers have found unique applications for
SPI-Chem Low Acid GMA when wet polymeric systems, such as for work on
reverse osmosis membranes is being done, because no other system seems to
be able to resolve the pores in the membranes. This unique yet versatile
resin system also has found applicability with biomaterials researchers,
especially in conjunction with implant retrieval studies.
The SPI-Chem Brand GMA monomer is supplied with the methacrylic acid
originally present substantially removed but with small amounts of
inhibitors present, to inhibit spontaneous polymerization during synthesis
and storage. This inhibitor need not be removed before use. The benzoyl
peroxide catalyst as supplied is provided in granular form.
We are addressing now the cured block, something that to most people is about as
inert of a material as one will find. But the standard practice in many laboratories
is to use a small jeweler's (or even a small hack) saw to cut the block down to the
right size, sometimes even to shape it.
We want to address the dust that is generated and how its exposure can and should be minimized.
SPI#02630-AA, denoted with ,
is shipped with nine 30 ml bottles of n-butyl methacrylate instead of one 250 ml bottle.
Storage conditions: Store "low acid" GMA under refrigeration, other components
can be stored at room temperature.