By Mike May, PhD

Single-use systems for bioprocessing rely on components that must be sterilized. Currently, gamma irradiation is used, but X-rays could be a better choice.

Recently, Adam Grzelak, PhD, senior scientist of Pall Europe, and his colleagues described the sterilization challenges. When asked more about the situation, Grzelak says, “There is a lot of concern whether gamma capacity will be sufficient to meet the increasing demand for single-use and contract irradiation.” Much of the concern arises from supply-chain challenges with cobalt-60, which is used in sterilization with gamma radiation. “It takes several years and careful planning to have the right amount of cobalt-60 in the right place at the right time,” Grzelak explains. “Spikes in demand, such as experienced with COVID-19, can become difficult to manage, and geopolitical business continuity challenges with transport of radioisotopes, access to reactors, and pushback against nuclear power all need careful management.”

Grzelak points out that the ISO 10993 standard provides the requirements for sterilizing medical devices with X-rays, but he adds that “many regulators are unfamiliar with X-ray sterilization.” Plus, he points out that some radiation regulatory standards, such as EU Annex 12, do not mention the use of X-rays.

Nonetheless, X-ray irradiation offers crucial benefits. “X-ray irradiation is a highly similar photon-based technology to gamma, employing the same units of dose, and it is expected to impact and sterilize polymers via the same fundamental physics mechanisms,” Grzelak explains. “As X-ray irradiation does not rely on use of radioactive sources, expansion of current facilities or creation of new X-ray sterilization facilities should be significantly easier, and this is already observed by virtually all new contract irradiation sites and most future capacity expansion focusing on alternative sustainable ionizing irradiation technologies.”

To expand the use of X-ray sterilization, Grzelak sees several requirements, including peer-reviewed verification data. “In quality risk management for biopharmaceuticals, trust the science, but verify is key,” he says. So, he and his colleagues used the industry-aligned test approach from the Bioprocess-Systems Alliance and the requirements for ISO 11137, which is the key standard for sterilization. “Within the scope of our tests, X-ray sterilization appears to be equivalent to gamma, indicating that X-ray can be used as a safe alternative,” he says.

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