INSTITUTE OF FOOD AND RADIATION BIOLOGY

Background

Institute of Food and Radiation Biology has a Gamma irradiation facility. This is a relatively small unit primarily designed for research , however is also used for irradiation services. Though initially designed as 50 KCi ( fifty thousand Curie ) Source, the current strength is about 17 thousand Curie with planned replenishment very shortly to 68 Kci. Gamma sterilization is very effective for sterilizing wide variety of medical and other products and more amore are being added every year a few of which are mentioned below.

• Cellulosic medical products: Absorbent cotton wool, boric cotton wool, mixed bandage, maternity towel, surgical guaze, swab surgical mask, surgical towel.
• Plastic medical products: Blood transfusion set, dropper, eye drop containers intravenous blood transfusion set, nasal drop containers, plastic examination gloves, plastics hypodermic needle, plastic hypodermic syringe, plastic petridish, plastic sculpt.
• Combination medical products: Delivery kit. Emergency kit, maternity kit, Tubectomy, vasectomy kits, dialysis unit, first aid dressing, paraffin dressing.
• Miscellaneous medical products: Acrylic powder, arterial prothesis, bio compatible materials, cannulae, endocardial tube, lap sponge, orthopaedic mixing bowl, packing material, pathological sample, preparation razor, surgical nylon suture.
• Pharmaceuticals : Alkaloids, hormones, ophthalmic drops, steroid, vitamin

Other products: The gamma source can be utilized semi commercially for de contamination of the spices spirulina, enzymes, antibiotics, peat soil and pharmaceutical products .

Methods of Sterilization

Five main methods are used for sterilization . The method used will depend on the size, amount and composition of the products.

1. Heat Method: In this method, high temperatures are used ( above 100^o C ) in controlled conditions . Dry heat sterilization is carried out by maintaining the product at 150^o C for one hour or at 160^o C - 170^o C for not less than 2 hours. This method is suitable for heat resistant products like glassware, metal ware some chemicals, oils etc
2. Moist heat sterilization is carried out air free with saturated steam under pressure at not less than 121^o C for a minimum holding time of 15 minutes . Other temperature time combination may be employed depending upon the stability of the product.
3. ETO ( Ethylene Oxide sterilization ) is carried out with pure gas or that mixed with suitable inert gas like CO₂, or halogenated hydrocarbon. This process is used for heat and radiation sensitive materials
4. Filtration method: Can be applied to certain products and is costly
5. Sterilant Chemical method: Has limitation in use and chemicals can be harmful to for the products.
6. Sterilization By Radiation: Sterilization of medical products and other pharmaceuticals with radiation has now become an acceptable practice all over the world .
7. The advantages of radiation sterilization:
   1. Is more reliable and has a high degree of sterilization quality
   2. This is a cold method , and there is no temperature rise , therefore can be used for temperature sensitive material.
   3. The gamma ray penetrates any final packing material , therefore the product gets sterilized within the package and the sterility is retained indefinitely
   4. The penetration during radiation sterilization is uniform..
   5. It does not require post sterilization microbiological quality control.

Disadvantage

Some glass on irradiation may undergo colour change. Some formulations of plastics may undergo chemical changes

Developments

A semi commercial project is also under construction at AERE , Savar . With an estimated start date of March- April 2009. this facility will have a source strength of 350 KCi, which will allow volume sterilization and much faster.

Others

• The radiation dose required for the destruction of fungi and majority of bacteria varies from 0.5 to 1.5 M rad Usually bacterial spores are more resistant than vegetative forms . A dose of 2.5 M rad is the officially accepted dose in many countries.
  
• Many products including radiation sensitive ones , having low or susceptible bio burden can be sterilized effectively at lower absorbed dose level. If lower doses are used additional micro biological monitoring of the product before and after irradiation would be necessary in order to assess the adequacy of the procedure.
• Currently more than 30 pharmaceutical and other companies , take our services to sterilize their products.