CBOSS-FDI will optimize the procedures for dispersion of cells and molecules in microgravity to enable future successes for growing cells in space. This investigation will use image analysis to assess how well the particles mix and if the size of particles causes distribution differences.Principal Investigator(s)
Wyle, Integrated Science and Engineering, Houston, TX, United States
National Aeronautics and Space Administration (NASA)Sponsoring Organization
Human Exploration and Operations Mission Directorate (HEOMD)ISS Expedition Duration:
April 2003 - September 2006
7,8,10,12,13Previous ISS Missions
CBOSS-FDI is a unique investigation to the ISS and was operated on ISS Expeditions 7, 8, 10 and 12.
The purpose of the Cellular Biotechnology Operations Support System (CBOSS) study was to support biotechnological research on board ISS by providing a stable environment in which to grow cells. The system was a multi-component cell incubator intended to grow three-dimensional clusters of cells in microgravity. A self-contained apparatus, CBOSS was designed to allow multiple experiments to be performed, thereby enabling scientists to study various types of cells operating simultaneously.
In the human body, cells normally grow within a scaffolding of protein and carbohydrate fibers that creates a three dimensional structure. But outside the body, cells tend to grow in flat sheets and are incapable of duplicating the structure they normally hold, which can make them behave differently in the laboratory than they would in the body. Past research has shown that cells grown in a microgravity environment arrange themselves into three-dimensional shapes that more closely duplicate how they would behave in the body. Cell culture in microgravity thus becomes a tool for studying cells in a state that is closer to that which occurs normally in the body.
When cells arrive for culture on ISS, they are thawed, injected into a static tissue culture module (TCM) with media (nutrition), and then additional media is added at different times while waste liquid is removed. When these cells are injected or additional media is added to the TCM, it is important that the entire contents of the TCM be uniformly distributed. If cells in one corner of the TCM are not receiving nutrients they will die, causing a leaching of waste products that can be toxic to other cells. There is also the potential for bubble formation in the semi-permeable TCM, which could be deleterious to cells in culture, so procedures are also being developed for their removal. CBOSS-FDI involves a series of experiments aimed at optimizing CBOSS fluid-mixing and bubble-removal operations while contributing to the characterization of the CBOSS stationary bioreactor vessel (the TCM) in terms of fluid dynamics in microgravity. These experiments will validate the most efficient fluid-mixing and bubble-removal techniques on orbit; these techniques are essential to conducting cellular research in microgravity and will enhance the probability of success for future investigations.
The CBOSS-FDI experiments will lead to a mixing protocol that is both optimal in providing uniform and reproducible mixing and convenient for the flight crew. In addition, these experiments will promote interactive science between the flight crew and the ground team. These goals will be accomplished by evaluating various mixing protocols using colored polystyrene microspheres, cytodex beads, and colored dyes in the TCM. Additionally, since bubble formation in the TCM can be deleterious to cells, the development of bubble removal procedures will enhance culture conditions in the TCM. Optimizing fluid mixing and bubble removal techniques on orbit is essential to conduct cellular research in microgravity.Earth Applications
These experiments will allow a better understanding of the physics of aqueous bubble-liquid interaction and the effects of gravity on surface tension.
CBOSS-FDI will use colored Polystyrene Beads to mimic cells while examining various mixing methods with those beads, such as: repeated injections/withdrawals into a TCM, mixing the contents by drawing circles on the TCM, squeezing the bag like a ketchup packet, etc. The pictures will be analyzed by ground teams by measuring Optical Density (OD) with various imaging software. The optical density profile across the TCM and the OD histogram of the entire TCM will determine how well the entire TCM is mixed. Once OD is determined, the statistical properties of OD histograms of various mixing methods will be compared to determine the best method to use with cell cultures in microgravity.Operational Protocols
After the CBOSS hardware is installed on Station, the crew will activate the experiments and monitor the status of the experiments and hardware. Crew members will use a syringe to inject fluid into the TCMs, using the TCMs' injection ports. Pictures are downloaded to the CBOSS flight control team for analysis at the Johnson Space Center's Telescience Center.
The CBOSS hardware supported six cell culture investigations with different detailed scientific objectives. There were problems in the growth and preservation of all of the cell lines grown on Expeditions 3 and 4. The PC12 and erythroleukemia cells did not survive well in long term culture, so no scientific results are expected from these experiments. It was found that there was more bubble formation than expected that may lead to cell death at the air-liquid interface. Although not well documented in this experiment, it was noted that poor mixing of cells/tissues and medium occurred in the other CBOSS payloads as well. Both the poor mixing and greater than expected bubble formation were important lessons learned that led to the addition of the CBOSS-Fluid Dynamics Investigation (CBOSS-FDI) to study mixing and bubble formation in microgravity on later Expeditions.
For CBOSS-FDI, a series of procedures was performed on Expeditions 8, 10, and 12 to optimize particle mixing and bubble removal. A mixing protocol for particles has been found that appears to be effective and time-efficient, and crew feedback has been very valuable in these studies. Two bubble removal methods were tested. Future experiments will help determine their effectiveness, and a protocol for bubble removal can be created for future tissue culture investigations. This investigation is critical for optimizing cell culture in space and ensuring the success of future investigations.