Miniature Bioreactor System for Cell Culture

The NASA developed Micro-Organ Device (MOD) platform technology is a small, lightweight, and reproducible in vitro drug screening model that can inexpensively biomimic different mammalian tissues for a multitude of applications. The technology is automated and imposes minimal demands for resources (power, analytes, and fluids). The MOD technology uses titanium tetra(isopropoxide) to bond a microscale support to a substrate and uses biopattering and 3D tissue bioprinting on a microfluidic microchip to eliminate variations in local seeding density while minimizing selection pressure. With the MOD, pharmaceutical companies can test more candidates and concentrate on those with more promise therefore, reducing R&D overall cost. This innovation overcomes major disadvantages of conventional in vitro and in vivo experimentation for purposes of investigating effects of medicines, toxins, and possibly other foreign substances. For example, the MOD platform technology could host life-like miniature assemblies of human cells and the effects observed in tests performed could potentially be extrapolated more readily to humans than could effects observed in conventional in vitro cell cultures, making it possible to reduce or eliminate experimentation on animals. The automated NASA developed technology with minimal footprint and power requirements, micro-volumes of fluids and waste, high throughput and parallel analyses on the same chip, will advance the research and development for new drugs and materials.

The Surface-Adhering BioReactor (SABR) is a novel microbial cell cultivation platform that mimics the way vascular plants use transpiration to deliver nutrients to their cells. In this biomimetic platform, microbial cells are cultivated as immobilized cells on a porous substrate where transpiration is used to passively deliver water and nutrients as well as harvest and concentrate secreted biomolecules by the microbial cells. The SABR transports nutrients to microorganisms without using a pump. Instead, evaporation and the cohesive property of water are exploited to pull the nutrient medium through the device, with a high degree of control, on an as needed basis. It eliminates the hydrodynamic shear stress on the cells and decreases the working volume of water needed for cultivation by a factor of 25 compared to planktonic bioreactors. Furthermore, the transpiration mechanism allows for the concentration of secreted products in areas of relatively fast evaporation, thus providing a passive means of secreted product harvesting. By matching the time scales of nutrient medium delivery and product harvesting with the time scales of growth and product formation, minimal energy is wasted in bioreactor operation. Transpiration enables a passive cooling system for the cells where either externally imposed or internally generated heat due to cellular activity is mitigated, thus preventing overheating that can lead to decreased productivity or even cell death. This technology enables significant reductions in energy input for cultivating microorganisms.

Once genes for a desired material type, delivery mode, control method and affinity have been chosen, assembling the genetic components and creating the cell lines can be done with well-established synthetic biology techniques. A 3D microdeposition system is used to make a 3D array of these cells in a precise, microstructure pattern and shape. The engineered cells are suspended in a printable 'ink'. The 3D microdeposition system deposits minute droplets of the cells onto a substrates surface in a designed print pattern. Additional printer passes thicken the material. The cell array is fed nutrients and reagents to activate the engineered genes within the cells to create and deposit the desired molecules. These molecules form the designed new material. If desired, the cells may be removed by flushing. The end product is thus a 3D composite microstructure comprising the novel material. This innovation provides a fast, controlled production of natural, synthetic, and novel biomaterials with minimum resource overhead and reduced pre- and post-processing requirements.

Microorganisms are unique from the standpoint that they can be employed as self-replicating bio-factories to produce both native and engineered mission relevant bio-products. Methane (CH4) usage in In-Space Manufacturing (ISM) platforms has been discussed previously for human exploration and has been proposed to be used in physicochemical systems as a propulsion fuel, supply gas, and in fuel cells. Carbon Dioxide (CO2) is abundant on Mars and manned spacecraft. On the International Space Station (ISS), NASA reacts excess CO2 with Hydrogen (H2) to generate CH4 and Water (H2O) using the Sabatier System (Figure 1). The resulting water is recovered in the ISS, but the methane is vented to space. Recapturing this methane and using it for microbial manufacturing could provide a unique approach in development of in-space bio-manufacturing. Thus, there is a capability need for systems that convert methane into valuable materials. Methane (CH4) is a potential carbon substrate for methanotrophic microorganisms which are able to metabolize CH4 into biomass. The innovative technology from NASA Ames Research Center ports Soluble Methane Monooxygenase (sMMO) to Pichia, that is, it moves the methane metabolism into a robust microbial factory (Pichia pastoris) (Figure 2). The yeast Pichia pastoris is a refined microbial factory that is used widely by industry because it efficiently secretes products. Pichia could produce a variety of useful products in space. Pichia does not consume methane but robustly consumes methanol, which is one enzymatic step removed from methane. This novel innovation engineers Pichia to consume methane thereby creating a powerful methane-consuming microbial factory and utilizing methane in a robust and flexible synthetic biology platform.

NASA's miniaturized electrosprayer offers a new technology that may support the next generation of portable and/or of precise electrosprayers. Developed for applying water to plants in space where gravimetric methods do not apply, this sprayer may also enable the delivery of a precise liquid for terrestrial uses without relying on pressurized air. Electrospraying (aka electrostatic spraying) is a technique where droplets are charged to enhance surface adhesion and coverage efficiency. Various electrospray variants are used in a host of industries to coat auto parts, apply pesticides and nutrients to crops, and more. Commercially-available electrosprayers are generally large, air-assisted devices that traverse up to 20 feet in the air and require large amounts of liquid and electrical power. NASA's miniaturized electrosprayer system does not require compressed air, uses far less liquid, and concentrates the mist in an area less than 2 feet away. The system only needs enough power to charge the droplets at the spray nozzle, so it may use small batteries (e.g., AAA batteries). The new electrosprayer implements a unique nozzle design that imparts a high charge-to-mass ratio on the spray and increases coverage efficiency. Thus, the miniaturized electrosprayer can be placed inside a portable, handheld sprayer or be used as a stationary device for a wide range of uses, particularly when spraying expensive chemicals (e.g., plant nutrients) and when precise, efficient spraying is required (e.g., industrial coatings, disinfectants, etc.).