Survivability of immunoassay reagents exposed to the space radiation environment on board the ESA BIOPAN-6 platform as a prelude to performing immunoassays on Mars.

The Life Marker Chip (LMC) instrument is an immunoassay-based sensor that will attempt to detect signatures of life in the subsurface of Mars. The molecular reagents at the core of the LMC have no heritage of interplanetary mission use; therefore, the design of such an instrument must take into account a number of risk factors, including the radiation environment that will be encountered during a mission to Mars. To study the effects of space radiation on immunoassay reagents, primarily antibodies, a space study was performed on the European Space Agency's 2007 BIOPAN-6 low-Earth orbit (LEO) space exposure platform to complement a set of ground-based radiation studies. Two antibodies were used in the study, which were lyophilized and packaged in the intended LMC format and loaded into a custom-made sample holder unit that was mounted on the BIOPAN-6 platform. The BIOPAN mission went into LEO for 12 days, after which all samples were recovered and the antibody binding performance was measured via enzyme-linked immunosorbent assays (ELISA). The factors expected to affect antibody performance were the physical conditions of a space mission and the exposure to space conditions, primarily the radiation environment in LEO. Both antibodies survived inactivation by these factors, as concluded from the comparison between the flight samples and a number of shipping and storage controls. This work, in combination with the ground-based radiation tests on representative LMC antibodies, has helped to reduce the risk of using antibodies in a planetary exploration mission context.