Lowicryl HM20 Non-Polar Embedding Resin Kit, Hydrophobic, 805g Total Kit
HM kits are non-polar four component kits and are used to produce high contrast images of completely unstained thin sections by atomic number contrast only. Also these HM kits are particularly suitable for dark field observations because of their relatively low electron density.
HM20 Non-Polar Embedding Resin Kit
System is hydrophobic and designed for use down to -70°C with polymerization being done with UV exposure. The HM20 kit has been the subject of some discussion on the Microscopy Listserver. After polymerization, the block sometimes turns to a light pink or pink/red color. This seems to be quite normal and should not be a cause for concern.
Kit contents (805 grams total)
675 gms = Monomer
E130 gms = Crosslinker
D4.8 gms = Initiator C
These ready-to-use kits are provided as highly purified, three-component systems, precision formulated to enable their use at temperatures as low as -80°C using long wavelength (360 nm) UV and photopolymerization kinetics. Others might describe the Lowicryl resins as being methacrylate-based low temperature UV curing resins. And all kits are useful for freeze-substituted samples. The low viscosity permits better retention of cellular ultrastructure, improved preservation of antigenicity and significantly lower background labeling. Lowicryl can also be used at room temperature and to produce high contrast TEM images of unstained thin sections. These resin kits were developed some years ago at the University of Basel in Switzerland and were originally produced by the Chemische Lowiwerke GmbH in Germany.
From the standpoint if "why they work so well", there is a general perception that sections, both thin and thick, have rougher surfaces than epoxy embedments yielding more surface area, thereby exposing more antigenic sites per unit projected area of the section, and at the same time, increasing the sensitivity of detection.
Complete instructions are included with each kit. If you are a first time user, or just want to know more about what has been published previously by others, we offer a list of useful references on the use of the various Lowicryl resins in various applications.
Polymerization time at low temperature:
There are probably as many protocols for the polymerization as there are people using Lowicryl. A typical protocol might call for a UV polymerization -20° C for 2-3 days and then a further 1-2 days at room temperature, which, apparently, at least in most instances, does not affect immuno labeling sensitivity, even at the TEM level. This additional room temperature curing does seem to make the block easier to section.
Keep in mind that these kits involve the use of methacrylic acid ester preparations and the toxicological properties of these products are not fully known. Some users have reported the development of allergies and/or sensitivities to these materials. One should keep these facts in mind when handling these particular resin systems and at times, when making the decision to even use them if you have had previous experience with sensitivities to methacrylate resins. Good laboratory quality vinyl gloves are recommend for the use and handling of all Lowicryl products.
Low temperature polymerization:
Keep in mind that these resins were developed for use at low temperature using a UV cure. SPI offers an easy-to-use low temperature UV curing chamber for this type of embedding.