We are going to buy a liquid nitrogen tank for our cell culture room. One choice is to buy a second hand one, which have been used to import animal sperms before. I do not have any idea about the type of contamination it may contain. Are there any reliable strategies to sterilize such cryogenics?
The nature of the vessel dictates the choice of sterliant.
If it is stainless steel (304L?) then a warm bleach solution should be more then sufficient. If it is Nalgene, or if you are concerned about chlorine in your area, then hydrogen peroxide (>3% conc) should do the trick.
Wash and rinse repeatedly, and follow up with a visual inspection to ensure that any solid matter (!) has been shifted.
Hi James
Thanks for your kind guidance. As another question I would like to know whether these strategies suppress probable microorganism contaminations (like different viruses and bacteria) as well or not.
thanks in advance
hi Somaye,
In addition to rinsing as James prescribed, heat the vessel to minimum 45 deg Celsius to kill all bacteria and create a vacuum. Thereafter, purge the vessel with Nitrogen gas. Repeat vacuum and purging for couple of times. Fill nitrogen gas and seal the cap. This is generally done in pharma for normal applications.
Abhay,
I'd caution against relying only on vacuum and modest heat. Prions survive those conditions (I believe) and I know from experience that some bacterial spores survive desiccation to micro bar pressures of water vapour and prolonged temperatures in excess of 70deg C.
Chemical attack is guaranteed, if the vessel`s materials can tolerate it.
For utter certainty, exposure to an oxidising plasma (H2O2 at low pressures) is also viable - but neither cheap nor practicable for an LN2 vessel or Dewar.
Hi James,
Thanks for information. Your concern is valid.
Regards
Abhay
I would agree with the first answer, swab,soak and rinse with Hydrogen Peroxide or Virkon (corrosive) solution depending on the material it is made from.
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