Team:UofC Calgary/Design
Through conversations with our targeted audience of astronauts, we learned that radiation shielding for astronauts is a complex engineering problem. Current proposed solutions such as lead coating on spaceships, carbon nanotubes filled with boron, or generation of a radioprotective magnetic field using nuclear reactors are too expensive due to the additional cost in weight during launch and transport to deep space. Our delivery system outlines a more cost effective and practical way for astronauts to be shielded against ionizing radiation, which is currently a large factor preventing longer space flights.
In order to develop a sophisticated solution for the administration of our radioprotective peptide mBBI, a biotherapeutic transdermal patch was considered. The patch will house bacteria (B. subtilis) which are engineered to produce our radioprotective peptide mBBI, which will diffuse to the bloodstream through our patch system, giving radioprotection to the whole body. Through simulations, mBBI has a half-life of four hours. A typical mode of administration, such as intravenous injections or oral administration, would have been ineffective at maintaining a constant dose of peptide, as the peptide would be degraded by the body. After a period of time, mBBI would have to be readministered to maintain an effective dosage concentration, resembling a sinusoidal wave in drug administration. Our transdermal patch design allows us to maintain a stable concentration of mBBI in the blood. The peptide is constantly produced inside the patch by Bacillus subtilis and continuously delivered into the body via diffusion. In addition, the application procedure is noninvasive.
To better integrate our project into existing infrastructure and for future space missions, we designed our delivery system for long-term use and portability. Our patch design included four small pockets attached to one main large pocket. One pocket of the patch contains dry B. subtilis endospores. When pressure is applied, the pocket will release the spores into the main compartment, where the spores will be rehydrated and activated to their vegetative state. This allows our patch to be stored for long periods of time (as B. subtilis spores are resistant to desiccation and radiation) when not in use. To extend the lifetime of the bacteria in the patch, the other three pockets include super-rich media, which can be added when the initial nutrients are depleted. These design considerations will help extend the shelf-life as well as lifetime of individual patches, reduce the total number of patches needed for a mission and reducing overall waste. The total weight of one of our patches checks in at about 15g, and the overall dimensions are 7cmx7cmx0.29cm. These specifications underly the portability aspect of our design, making our design the preferred form of radioprotection in terms of storage-space and weight.
To ensure the durability of our patch during accidents such as punctures, tears, or the patch falling off the user, we researched materials used for transdermal delivery. Companies specializing in transdermal delivery were contacted for design, material, and manufacturing advice. We designed small-scale prototypes using SOLIDWORKS, and printed them in 3D to better understand the patch to scale. Finally, we prototyped our design using the researched materials. These materials were also tested in our laboratory for their ability to allow mBBI to diffuse through while retaining bacterial cells. To determine if our design was cost effective, we also looked into large-scale manufacture and the level of difficulty to manufacture multiple patches. This led us to develop a user’s manual for our patch and project design, where all information related to our applied design can be found. This user manual can be found below.
