Established Methods of Resin Histology

Established methods of resin histology

In our laboratory we have established a wide range of processing with resin embedded samples. Whether bones, teeth, cartilage, calcified structures or hard to slice soft tissue: we offer a suitable resin embedding for all requirements.

Embedding in resin is necessary if paraffin is not hard or stable enough to give the sample uniform good cutting properties. Various resins are then used to embed the material. A few resins can be considered to provide further embedding for the sample. 

 

Methyl methacrylates / MMA's (Technovit® 9100)

Methyl methacrylate (abbreviated MMA) is a colorless liquid with a characteristic odor that is used in the production of acrylic glass. Due to its small molecule size, it has very good impregnation properties and is therefore suitable for embedding tissues and their subsequent histological processing.

MMAs from different manufacturers are available on the market. For histological embeddings, however, only the MMA's of the Technovit® polymerisation systems from Kulzer have been able to establish themselves. Technovit® 9100 is a 5-component system suitable for embedding soft and hard (non-decalcified samples) and has very good cutting and sawing properties due to its coherent polymer chains.

The embedding is carried out via an alcoholic dewatering series with two xylene steps and a Technovit® xylene step before the pure MMA solution is used for tissue infiltration.

Hydroxy-methyl methacrylates / HEMA's (Technovit 7100, Technovit 8100) & glycol methacrylates / GMA (Technovit 7200)

Hydroxy-methyl methacrylate (2-hydroxyethyl methacrylate (HEMA) or glycol methacrylate (GMA)) is a resin that can be used for embedding lime-free or decalcified tissues. Polymers of largely pure HEMA / GMA become very hard and brittle and are therefore not cuttable; small amounts of n-butyl methacrylate are added as plasticisers.

The polymerisation of HEMA / GMA can be stimulated by barbituric acid derivatives in combination with chloride ions and benzoyl peroxide or by UV light. The catalyst system required for this purpose does not contain any aromatic amines, which is an advantage over other systems based on peroxides and aromatic amines.

The Technovit® 7100 and 8100 polymerisation system polymerises in soft form. Embedded samples can be prepared with common microtomes, which have a retraction in 1-2 µm thin sections, which can be drawn on standard object carriers and processed in different colours. The Technovit® 7100/8100 system consists of largely non-toxic components. The resulting plastic blocks are transparent and uniformly cured throughout and do not discolour even after prolonged storage. Polymerization takes place independently of or is not influenced by atmospheric oxygen, nor by atmospheric humidity and no temperatures above 40 °C occur during the polymerization process.

Technovit® 7200 is a light-curing, substantially harder polymerising variant of HEMA / GMA and is therefore suitable for embedding very hard material, which can then be processed into microscopic specimens using diamond band saws (cutting grinding techniques).

The embedding is carried out by means of ascending alcohol series or water-GMA mixtures before being carried over into a pure Technovit® solution. 

Epoxy resins (Araldit, Epon, LR-White, SPURR)

Epoxy resins have been used for embedding tissue samples since about 1956, in particular for the production of semi-thin sections and for electron microscopy. They show a low shrinkage and uniform curing and their hardness can be adjusted by different substances.

The basis of epoxy resins two epoxy groups, which are converted (polymerized) with the anhydrite of a dicarboxylic acid as hardener to a polyester alcohol by opening the epoxy rings. Tertiary amines are used as accelerators. 

Infiltration is carried out in several stages by means of an alcohol series and propylene oxide, until it is then infiltrated in the pure epoxy solutions or the polymerisable embedding oils which can be mixed in, and finally poured in.

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