Abstract
Ionizing radiation is widely used to inactivate pathogens. It mainly acts by destroying nucleic acids but causes less damage to structural components like proteins. It is therefore highly suited for the sterilization of biological samples or the generation of inactivated vaccines. However, inactivation of viruses or bacteria requires relatively high doses and substantial amounts of radiation energy. Consequently, irradiation is restricted to shielded facilities—protecting personnel and the environment. We have previously shown that low energy electron irradiation (LEEI) has the same capacity to inactivate pathogens in liquids as current irradiation methods, but generates much less secondary X-ray radiation, which enables the use in normal laboratories by self-shielded irradiation equipment. Here, we present concepts for automated LEEI of liquids, in disposable bags or as a continuous process. As the electrons have a limited penetration depth, the liquid is transformed into a thin film. High concentrations of viruses (Influenza, Zika virus and Respiratory Syncytial Virus), bacteria (E. coli, B. cereus) and eukaryotic cells (NK-92 cell line) are efficiently inactivated by LEEI in a throughput suitable for various applications such as sterilization, vaccine manufacturing or cell therapy. Our results validate the premise that for pathogen and cell inactivation in liquids, LEEI represents a suitable and versatile irradiation method for standard biological research and production laboratories.
Highlights
Ionizing radiation is widely used to inactivate pathogens
As low energy electron irradiation (LEEI) has a low penetration depth, we developed two separate strategies for the transformation of liquids into fluid films, which are thin enough to be completely penetrated by the electron beam while automatically moving through the irradiation area
We show that automated LEEI can be used to inactivate various organisms in liquid solution by delivering exact doses in a wide range, which renders the method suitable for numerous fields within biotechnology
Summary
Ionizing radiation is widely used to inactivate pathogens. It mainly acts by destroying nucleic acids but causes less damage to structural components like proteins. Few inactivation technologies leave the structural components largely intact, so that the material can be used e.g. as vaccines, in diagnostics or in therapeutic strategies[1,2,3] Ionizing radiation, such as gamma-, X-rays or high energy electrons, has been used for decades for the inactivation of pathogens, e.g. in sterilizing food or packaging[4,5,6]. Ionizing irradiation facilities require a separated irradiation compartment surrounded by a combination of heavy lead shielding and/or thick concrete walls and cannot be placed inside or even close to biological production or research laboratories[15,16] This drawback has so far prevented ionizing irradiation-based inactivation processes in many biological and medical applications. The only exception is ultraviolet (UV) light of short wavelength, considered ionizing irradiation, which does not generate such secondary high-energy photons, but can cause substantial damage to the biological material, e.g. due to photoadducts, and generates less efficient vaccines compared to gamma-irradiation[17,18,19]
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