This technique involved radiation dry heat, moisture, boiling water, steam at 100ºC, and steam under pressure.
Radiation: This method involved the used electromagnetive radiation in the microbiology laboratory to achieve this sterilization goal. In these techniques, the source of electromagnetive radiation used for the sterilization, are ultra violet light and gama rays. With advance of scientist it has been discovered that exposing microorganism on a sunlight for a long time directly eliminate the organism. These phenomenon’s take place because ultra violet ray (uv) exists in high limit of spectrum. The mechanism behind this, is that the light is generated in the laboratory by using Hot-cathode or low pressure mercury dapour lamp, this have bacterial cidal effect at a higher wavelength between 250 to 260nm. In a living cells, there is a molecule called nucleotide, the molecule absorb ultraviolet light, by engaging the molecule on a high concentration of light, it gain extra energy that is sufficient to break the weak intermolecular bond joining hydrogen bond of double stranded dioxide nucleic acid (DNA) helical structure, this cause intermolecular change that lead to the killing of the organism cells. But some genes are sensitive than the other to this damage, i.e some of the organism that have double or multiple cell copies will require a higher of the light before accomplishing the same result, compared to that observed when a single important gene is detected.
Sine this technique kill bacteria slowly, it means that it has a poor penetrating power, in such case will reduce the used of the technique in many laboratory. For example when the technique is apply on thin cover slip glass as barrier, it prevent the killing of bacteria under it surfaces completely. Also a drop of aerosols will help protect bacteria in between them. The area of application of uv light sterilization is of that air inoculating cabinet and sterilization of room which will permit the light to be left over a long period of time between the manipulations. In term of gama ray, these techniques has more energetic radiation compared to that of ultraviolet ray. It is an ionization energy that has the power to break the peripheral electrons out from their obit around the atomic nucleic to produce ion pairs.
They highly active in terms of ion H+, OH- are produce when an interaction take place inside the cellular of water, because of the production of this ion, it give power to the molecular for cell reaction. Furthermore, when this kind of ionization in the DNA take place, it cause damage to the cell of which it will not be able to be repaired. Gama ray has a very high penetrating power, in such case make it perfectly ok for sterilization of prepare disposable material, such as syringe, needle, and transport media. In as much as chemical change affect the media performance and these sterilization make use of ionization, care must be taken after sterilization, the media should be confirm either the is still working perfectly.
On no occasion, these techniques should be used for sterilization of pharmaceutical materials and food product, because the ionization causes the alteration of the product themselves.
Do to the hazardous effect of these technique, precaution and special material are require before commencing the sterilization. But those material used is very heavy and expensive in these case they are mostly used by large scale manufacturers compare to microbiology laboratory. The radiation source used here are cobalt or cesium and the does are measure by kilo Gray (KGy), 25KGy give a perfect sterilization.Sterilization Techniques in medical Laboratory