Preservation by Plastination

The study of biological specimens is significantly impeded by processes of decay. Thus, for centuries, people have been looking for appropriate methods of preservation. Thanks to the method of plastination, biological specimens can be prepared for research, teaching, and demonstration purposes in a lifelike and durable manner. To this end, in a vacuum process, specimens are impregnated with special reactive polymers. The mechanical (flexible or rigid) and optical (translucent or opaque) properties of the polymers used determine the characteristics of the preserved objects. Plastinated specimens are dry and odorless; they maintain their original surface relief and are identical to their state prior to preservation, down to the cellular level. Even histological studies can be performed on them.

The method of plastination is based on replacing the water and fat contained in tissues with a reactive polymer such as silicone rubber, epoxy, or polyester resins: In a solvent bath, initially the tissue water is replaced by freeze substitution, and later, at room temperature, the tissue fats are gradually replaced by acetone. The dehydrated and degreased specimen subsequently is placed into the polymer solution. Under vacuum conditions, the solvent, in its gaseous state, is then continuously extracted from the specimen, creating a negative pressure that causes the polymer to gradually enter into the tissue. Following this process of "forced impregnation", the specimen is cured with gas, light, or heat, depending on the polymer used.

A special variation of plastination is "sheet plastination". With this method, specimens such as individual organs or entire bodies, mostly in a deep frozen state, first are cut or sawed into slices of 2 mm to 8 mm (about 1/12 inch to 1/3 inch) thickness. These slices, placed between polymer nettings, are then dehydrated, degreased, and eventually impregnated with polymer under vacuum conditions. In order to give the specimens a smooth surface, the impregnated slices are either cured between foil or in a flat chamber are casted with additional resin. The refractive index of the resin used determines the optical properties of the plastinated body slices: Epoxy resin yields translucency and good coloration of the various tissues; polyester resin, which is used for plastinating brain slices, allows for particularly good discrimination between white and gray brain matter.

Plastinated slices of organs and bodies constitute excellent teaching materials in cross-sectional anatomy, a field of ever increasing importance, and they correlate well with radiographic images. Serial sections of translucent body slices are useful in various scientific research approaches. In addition, they are a suitable diagnostic aid in pathology because they allow for quick macroscopic-diagnostic screening of entire organs and organ specimens. Pathologically modified tissue areas can then be selectively analyzed with conventional histological methods.

Plastination was invented at the Anatomical Institute of Heidelberg University by Gunther von Hagens in 1977 and has been further refined since. By now, it has been generally recognized as a valid method of preservation and is practiced at more than 400 institutions in 40 countries. The main reasons for this wide-spread popularity of the method are the toughness, the durability, and the lifelikeness of the plastinates and the associated high teaching value.

 

Literature:
G. von Hagens, K. Tiedemann, W. Kriz: “The Current Potential of Plastination”, Anatomy and Embryology (1987) 175: 411-421.
G. von Hagens: Heidelberger Plastinationshefter, 1985 (Cat.-Nr. HA00-1 or HA00-2)