Deep Space Drug Shielding

Space medications help prevent astronauts from being ill and provide acute treatment in medical emergency situation for them to fulfill the primary goal of a successful long duration space mission: maintaining astronauts’ health in a unique, isolated, and extreme space environment. However, recently, National Aeronautics and Space Administration (NASA) have reported a shorter shelf life of space medications caused by chronic ionizing radiation and space medications’ long-term efficacy in space became questionable. Hence, to help extend the space medications’ stability and protect pharmaceuticals from the indirect radiation damage, Trolox, free radical scavenging antioxidant, were bio-conjugated with PLL (Poly-l-lysine) on the surface of drug encapsulated PLGA (Poly-lactic-co-glycolic acid) nanoparticles (NPs) using carbodiimide crosslinking chemistry. In this study, Melatonin, a sleep aid medication used in ISS, was chosen as a model drug. Radiation induced hydroxyl radicals, highly reactive free radicals, will be oxidized by Trolox before it could react with the pharmaceuticals in PLGA-PLL-Trolox composites’ core. The mean size of PLGA-PLL-Trolox composites were 491.3 ± 33.09 nm with zeta potential value of 26.4 ± 10.18 mV. A successful conjugation of PLL-Trolox on the surface of melatonin encapsulated PLGA NPs were determined by FT-IR and H¹-NMR analysis. Hydroxyl radical scavenging capacity assay (HOSC) was performed to test Trolox's free radical quenching ability. These results suggest a new molecular approach to shield pharmaceuticals from indirect radiation damage using antioxidant conjugated biocompatible polymer.