Photochemistry on the Space Station—Antibody Resistance to Space Conditions after Exposure Outside the International Space Station

International audienceAntibody-based analytical instruments are under development to detect signatures of life on planetary bodies.Antibodies are molecular recognition reagents able to detect their target at sub-nanomolar concentrations, withhigh affinity and specificity. Studying antibody binding performances under space conditions is mandatory toconvince space agencies of the adequacy of this promising tool for planetary exploration.To complement previous ground-based experiments on antibody resistance to simulated irradiation, weevaluate in this paper the effects of antibody exposure to real space conditions during the EXPOSE-R2 missionoutside the International Space Station. The absorbed dose of ionizing radiation recorded during the 588 days ofthis mission (220 mGy) corresponded to the absorbed dose expected during a mission to Mars. Moreover,samples faced, at the same time as irradiation, thermal cycles, launch constraints, and long-term storage. Amodel biochip was used in this study with antibodies in freeze-dried form and under two formats: free orcovalently grafted to a solid surface.We found that antibody-binding performances were not significantly affected by cosmic radiation, and morethan 40% of the exposed antibody, independent of its format, was still functional during all this experiment. Weconclude that antibody-based instruments are well suited for in situ analysis on planetary bodies. Key Words:Astrobiology—Cosmic rays—Biochip—Antibody—Planetary exploration. Astrobiology 19, 1053–1062