Frequently Asked Questions About Gamma-Irradiated FBS (Serum) and Other Products for Cell Culture

• What is gamma irradiation?
• Why do I need gamma-irradiated products like serum (FBS)?
• What is Ser-Tain™ processing?
• What do we mean by a 'validated process' for product irradiation?
• What is the rationale for the selection of organisms used in the irradiation-induced microbial inactivation studies?
• What effect does gamma irradiation have on serum and other product performance?
• How much radiation are these products exposed to?
• What is the conversion calculation for kilograys (kGy) to megarads (Mrad)?
• What type of documentation accompanies gamma-irradiated products?
• How are gamma-irradiated products identified?
• Does gamma irradiation provide protection against Bovine Spongiform Encephalopathy (BSE)?
• Do I need to change how I handle and use gamma-irradiated serum and other products?

What is gamma irradiation?

Like alpha and beta particle emission and X-rays, gamma rays are a type of electromagnetic radiation, but of shorter wavelengths. ‘Irradiation’ refers to the process of deliberately exposing a substance to gamma rays in order to kill bacterial contaminants by degrading bacterial DNA. Treatment of materials with gamma irradiation, a common process used in medical and pharmaceutical applications, involves exposing those materials to a radioactive Cobalt-60 source under tightly controlled conditions. The gamma rays from this source induce the formation of ultra-reactive and short-lived hydroxy radicals which inactivate most microorganisms present in a sample or substance by damaging or destroying their nucleic acids.

Why do I need gamma-irradiated products like serum (FBS)?

The use of any animal-derived material carries an inherent risk of contamination by microorganisms like bacteria, viruses, mycoplasma and fungi. Although all animal-derived materials we provide and use are rigorously pre-screened for such contaminants according to strict federal regulations, very low levels may exist that are below the threshold of detection for current test methods. The SER-TAIN™ gamma irradiation process provides greater assurance that any existing low-level of contamination by microorganisms will be reduced and that the risks associated with animal-derived components are minimized.

What is SER-TAIN^™ processing?

The SER-TAIN™ process is a comprehensively validated gamma irradiation process that provides significant reductions in the levels of relevant microbial contaminants in susceptible biological products like fetal bovine serum.

What do we mean by a 'validated process' for product irradiation?

A validated process is one for which every step is documented to ensure the consistency of methods and product integrity, as well as complete traceability. Every step in the SER-TAIN™ process, including the packaging of product by qualified employees, delivery to the irradiation facility via dedicated ground transportation, and calculation of delivered dose, has been qualified and is performed the same way every time. By controlling each step in the process, we can assure quality and consistency in every lot of gamma-irradiated product we supply.

What is the rationale for the selection of organisms used in the irradiation-induced microbial inactivation studies?

The organisms selected are naturally occurring potential contaminants from either the animals themselves or from the environment in which the collection process takes place. Organisms that are either not associated with the animal (example: MvM, Minute Virus of Mice), or are difficult to culture (example: BLV, Bovine Leukemia Virus), are chosen or substituted with consideration of relevance.

What effect does gamma irradiation have on serum and other product performance?

Gamma irradiated serum has been tested side-by-side on several cell lines against non-irradiated controls for growth promotion, plating efficiency, cloning efficiency and protein production. The irradiated serum performed at levels greater than 80% of the controls, with no evidence of significant performance differences. Trypsin products made from irradiated powder show no significant loss of dissociation activity when compared to non-irradiated controls.

How much radiation are these products exposed to?

Because of their physical characteristics, serum and trypsin products require different levels of irradiation to ensure inactivation of adventitious agents while still maintaining product integrity. Tight controls ensure that serum products are irradiated between 25 - 35 kGy, and trypsin powder receives a dosage between 43 - 56 kGy. Other dose ranges are available on a custom basis.

What is the conversion calculation for kilograys (kGy) to megarads (Mrad)?

One gray is equal to 100 rads; therefore, the dosage range of 25 - 35 kGy is equivalent to 2.5 - 3.5 Mrad.

What type of documentation accompanies gamma-irradiated products?

A Certificate of Irradiation is provided with every lot of gamma-irradiated material. This document is generated by the irradiation facility itself and provides information about when the material was processed and what dosage of radiation it received. Certificates of Analysis, which include information about country of origin, are also available for each lot.

How are gamma-irradiated products identified?

We have a unique system of identifying gamma-irradiated serum products. Prior to the irradiation procedure, a circular yellow indicator label containing catalog and lot numbers are applied to each bottle in addition to the standard labeling. Upon exposure to gamma irradiation, this indicator label changes color from yellow to red. This system provides customer assurance that each bottle is irradiated, as well as supplying important product identification information. Labels on bottles of gamma-irradiated trypsin solutions all clearly identify the product as "Gamma-Irradiated."

Does gamma irradiation provide protection against Bovine Spongiform Encephalopathy (BSE)?

Currently, there is no conclusive evidence that gamma irradiation effectively inactivates the agent responsible for BSE, which is thought to be a prion rather than a microorganism. Because there are no tests available for screening live animals, the best available assurance that bovine serum does not contain BSE is to source it from countries and/or suppliers deemed at low risk for BSE. All our bovine-sourced products originate from countries recognized as being at low risk for BSE.

Do I need to change how I handle and use serum and other gamma-irradiated products?

Irradiated products should be handled, stored and used in the same manner as non-irradiated products. The shelf life and expiration dates of these products are also unchanged. Because there is no significant effect on product performance, there is no need to alter the volume and concentration you normally use when switching from untreated serum to SER-TAIN^TM irradiated serum.