Plastination – A favourable Approach to Preserve Biological Specimens
Divya Gupta
Assistant Professor, Department of Veterinary Anatomy, DGCN COVAS, CSKHPKV,
Palampur-176062
*Corresponding Author:dolly.19gupta88@gmail.com
Abstract:
The fixation and preservation are the integral parts to prevent the biological tissues from decomposition and deterioration. Also these are essential to make the specimens firm and in a specific life like state. The formalin is a most common preservative used since decades due to its properties. But still it bears some drawbacks which leads to need of other alternatives for preservation of specimens. Plastination is a novel method to preserve the specimens in dry and odourless state invented by Dr. Gunther Von Hagens in 1977. This process has been proved to be very beneficial in anatomy both for educational and research purpose.
Key words: Preservation, Specimen, Polymer, Anatomy, Teaching
Introduction:
The organ preservation is an important aspect of Anatomy laboratory because organs have tendency to get degenerate if left without any preservative. This can be achieved by the fixation of specimen which aims to stop autolysis and preserve tissue in its original state. 10% formalin has been used as most common preservative since decades and it is a very effective preservative. Despite of its preservative qualities, it has lots of harmful side effects on human body like it causes irritation in eyes, tears, nose burning and hypersensitivity reaction. It is harsh to smell and in worst cases can lead to nasopharyngeal cancer. Also the preservation of specimens in formalin made them brittle and difficult to transport due to its spillage. To overcome these drawbacks a technique known as Plastination has been discovered by Dr. Gunther Von Hagens in 1977 in Germany. He developed the Silicone (S10) technique and it has been considered as the gold standard for plastination. Thus plastination is defined as a method for the preservation of biological specimens for long term by using specific polymers. This technique produces dry, clean, non smelly, durable and non toxic specimens. The specimens like whole organs, whole body or sections of organs like brain can be preserved with minimum aftercare.
Principle of Plastination:
This technique is based on the principle that the molecules of polymer replaces the molecules of biological fluid in a specimen. Here a curable polymer penetrate inside the tissue of a specimen under the vacuum conditions. The forceful impregnation of polymer in tissues makes them stable and less prone for degeneration.
Types:
Basically this technique has been categorized mainly into two types i.e Silicone plastination and Sheet plastination. The basic steps involve in the process are common in both methods and the difference exists in the type of polymer used.
- Silicone plastination: This method is used when we have to make plastinate of whole specimen or thick sections of specimens. The specimen resulted will be more flexible. e.g. S10
- Sheet palstination: This method is used for usually thin organ slices usually of 2-5mm in thickness. Epoxy and polyester resins are particularly used in this method. Plastinates resulted through epoxy resins are transparent and generally used for research purpose e.g. E12. The opaque brain slices can be prepared by using polyester resin. e.g. P35
Procedure:
It involves the following steps:
- Fixation: It is usually done in 10% formalin to stabilize the tissue in its original state as much as possible. However formalin can be used in concentration varying 5% to 20%. Old specimens that have been kept since many years in the laboratory can also be plastinate.
- Dehydration: It is usually done in Ethanol or acetone after rinsing the specimens in running tap water. Ethanol is least preferred because it takes longer time and leads to more shrinkage of tissue. Acetone has been considered as best solvent for plastination as it readily mix with different types of resins. It also acts as defatting solvent. The volume of acetone used is about 5-10 times more than that of specimen and the specimen should immersed in it at least for 3 weeks at room temperature. The cost of acetone is an important factor in this process. Thus the acetone distillation plant installation for this process is of much importance so that acetone can be reused.
- Force Impregnation: In this process, the space occupied by water and lipids has been filled with curable polymers. The dehydrated specimen has been put in liquid resin solution under vacuum condition that draws out acetone and infiltrate polymer inside. Generally the polymers used are silicone and Epoxy resins. To overcome the cost of resins, some indigenous methods also have been developed e.g. the use of quick fix along with amylacetate in equal parts prove to be ideal to preserve whole visceral organ. The technique develops by them proved to be very simple and cost effective.
- Hardening: It is also known as curing. The specimens can be cured by using gas, heat, UV light, or resins. Once the specimens get hardened, they will be ready to use.
An alternate indigenous plastination technique has been developed by Ramakrishna and Prasad in 2007 using environmental pollutants like plastic tea cups and thermocol. In this technique the need of expensive equipments has been minimized as all steps have been carried under room temperature. Thus this technique proved to be low cost technique in which the whole process took around 8-10 weeks to complete. The plastinate resulted by this indigenous plastination technique were very economically affordable and serve as a good teaching aid.
- Finishing and Storage: The unwanted area and the polymer can be trimmed out with scalpel. The specimens can be easily clean with a lubricant and store in plastic bags or Perspex stand at room temperature.
Advantages:
The foremost advantage is that plastinated specimens are easy to store and require low maintenance. These specimens are more durable and can be store for a longer period. These specimens are resistant to fungal growth and decay. These specimens have been accepted as best for teaching in comparison to formalin preserved specimens. Also they served as great synthetic models because of their better vision of anatomical variations. They may be easily handled by those are allergic to formaldehyde. The process of fixation with formalin leads to inhalation of toxic compound which produce significant health hazard and the use of plastinated specimens solve this issue by preventing excessive exposure to staff and students to this toxic substance. These specimens can be examined from all angles and make detailed study more appropriate. Further the palatinate specimens can be used for histology purpose. They served as a great tool for gross anatomy and cross sectional anatomy.
Disadvantages:
This technique is comparatively more expansive than other conventional preservative methods. The main cost is for purchasing the instruments but the further cost can be reduced by establishing the acetone distillation plant through which the acetone can be reused again and again. The resins used in this process are also expansive. It is also quite time consuming process and required much more technical skills. To achieve perfectly displayed specimens, it requires lot of work even after the completion of curing process. The superficial structures cannot be manipulated to see the deep structures. Also it involves little shrinkage of specimen and thus specimens appears to be little smaller than usual.
Conclusion:
Plastinated specimens are proving more beneficial for preservation of biological specimens in laboratory. They serve as excellent tools in teaching anatomy as compared to formalin preserved specimens. Also they proved to be wonderful artistic museum specimens. Generally students face lot of difficulty in handling the formalin preserved specimens during practical class and self learning. Also due to ethical issue, animal sacrifice has become very difficult and thus there is scarcity of animal samples in laboratory for anatomy teaching. These drawbacks can be overcome by using this technique for preservation as the resulted plastinates appears more lifelike and without surface morphological modifications. The indigenous trials to modify this technique make it comparatively cheaper and affordable in India. Due to its advantages, it is gaining popularity and thus it is a recommended method of preservation of specimens especially for teaching and research purpose.
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