UV sterilizing technology

Ultraviolet (UV) radiation is widely used to sterilize water, air and surgical materials.

UV radiation is subdivided into UV-A (wavelength 315-400 nm), UV-B (280-315 nm), and UV-C (40-280 nm).

UV-C is the most energetic portion of ultraviolet radiation; it can cause electronic excitation leading to the breaking of chemical bonds and the formation of unpaired electron species, known as radicals, that are highly reactive and can damage DNA and cell replication deactivating all kinds of microorganisms from viruses to fungi. The technology to generate UV-C is based on a bulb that contains gaseous mercury which, when subjected to electricity, emits an ultraviolet radiation, 95% of which is at 253.7 nanometers. This wavelength is in the region of maximum germicidal effectiveness and is highly lethal to virus, bacteria and mold spores.

We use this technology in an apparatus specifically designed for the sterilization of LN. Because LN evaporates very rapidly when subjected to UV irradiation, in the NTERILIZER apparatus we have used a specifically designed ASIC to deliver the minimum amount of irradiation sufficient to inactivate the most resistant microorganism known.

The amount of UV radiation required to deactivate a specific microorganism is known as dose. Doses for virtually all known microorganisms, from viruses to fungi, are available in the literature; for instance, the Hepatitis virus requires an 8,000 UV dose wheras A. niger requires a 330,000 UV dose. Because Aspergillus is the most UV-resistant microorganism known, the NTERILIZER apparatus has been calibrated to deliver a dose 50% higher than that required to deactivate Aspergillus and proportional to the amount of LN present and to the geometrical configuration of the vessel where the LN is contained.

The rate at which the microorganisms are deactivated depends also on the efficiency of the UV irradiation system, which, for UV lamps that use the Hg technology (as opposed to UV lamps that use LED technology), is inversely proportional to the temperature at which the irradiation system operates. Therefore, NTERILIZER also takes into account the temperature of the lamp in order to calculate its relative UV output given the cooling effect induced by the evaporation of the LN.

The efficacy of UV radiation for the sterilization of LN was investigated in a study by Parmegiani et al. In this study the authors used S. maltophilia, P. aeruginosa, E. coli, and A. niger because these microorganisms were previously detected by Bielanski al both in LN and in cryostored semen and embryos. Contamination by S. maltophilia seems to be particularly relevant for assisted reproductive technologies because this is a ubiquitous environmental prokaryote that can affect sperm motility and may suppress embryonic development. Pseudomonas aeruginosa and E. coli had already been used in a study on experimental contamination of LN vapor shipper dewars.

The study showed that decontamination of LN with UV irradiation is feasible and simple and that UV radiation deactivated the growth of all the microorganisms tested.

Quality Control

Cryotanks require periodic decontamination using an efficient disinfectant to decrease the risk of cross-contamination. The procedure requires emptying the cryotank, cleaning it and then shipping it out to a contractor that specialises in the process of sanitization of cryotanks. This proceure is cumbersome, logistically demanding and costly.

Regular implementation of the cleaning procedure of cryotanks using NTERILIZER (as described in the page STORAGE on this website, can reduce or eliminate altogether the sanitization procedure.

However, frequency of decontamination and servicing of LN dewars depends on their volume, the presence of infectious samples, the number of stored embryos (straws, vials), the frequency of LN refilling and moving germplasm in and out. It should be kept in mind that non-sterile LN, common air pollutants, and microorganisms attached to the outside of embryo containers will contribute to the accumulation of contaminants in a dewar over time. Therefore, the IVF practitioners must take into account the above factors to determine appropriate intervals between periodic decontaminations of LN dewars.

NTERILIZER now offers a quick and reliable service to check periodically the sterility status of the cryotanks. To enquire about the availability of the service in your country, please contact us.