During long duration missions, the space crew must be provided with safe and effective pharmaceuticals. The stability of the medications is key to ensure the safety of astronauts. Outside of low-Earth orbit, astronauts are exposed to radiation from galactic cosmic rays (GCR) and solar particle events (SPEs) as they exit the Earth’s protective atmosphere. GCR consist of high-energy charged particles, fully ionized, coming from outside the solar system; while SPEs consist of low-medium energy electrons, protons, alpha particles and heavier particles originating from the sun. Without the earth’s protective atmosphere, radiation damage to the space crew increases, resulting in a higher risk of cancer, damage to the nervous system, radiation sickness, and degenerative tissue diseases. Though these are consequences of space flight, fortunately most of these effects can be mitigated thought the administration of appropriate medications. However, medicines also react in the space environment to these same environmental inputs, often becoming less effective, thus, they need to be protected.
Silk is a biocompatible and safe protein approved by the US Food and Drug Administration (FDA) for some medical products and used widely in consumer goods. There is a long history of the use of silk protein matrices to stabilize bioactive compounds. We have also shown previously that silk composite materials provided useful protection against the effects of environmental radiation when present in the form of silica composites during 18 months onboard the International Space Station. These earlier findings provide the foundation to exploit silk-based composites as a radiation shielding biomaterial to protect medications from environmental stresses – not only radiation but also variances in temperature and humidity onboard spacecraft. In the present study, films consisting of silk proteins in composite formats with inorganic particles and antioxidants are being pursued to demonstrate the breadth and nature of protection provided for a range of drugs during exposure to environmental extremes. Methods include accelerated testing with temperature and humidity, radiation exposures, molecular modeling for mechanistic insight, and functional assessments of the matrix and drug stabilities. Computational models and density functional theory (DFT) calculations are performed to understand the fundamental mechanisms of material susceptibility to radiation, and associated protection or degradation of the medicines. The biomaterial systems are evaluated against elevated temperatures and humidity, as well as the different type of radiation such as GCR and SPE. The best formulations will be chosen for further studies in space.
This work is supported by the Translational Research Institute through NASA Cooperative Agreement NNX16AO69A.
understand structure and function of silk protein matrices
gain insight into methods used to assess stabilization of therapeutics in silk matrices
identify the value added by combining computational and experimental approches to the problem