The International Space Station (ISS) welcomes scientific guests, that is, experimental modules that have reserved berths in the ISS’s payload racks. In a sense, the ISS is a scientific cruise ship. It is extraordinarily exclusive even though the accommodations are plain, the provisions are sparse, and the attentions of the busy astronaut staff are, necessarily, fleeting.
The ISS can skimp on luxuries because it is the ultimate cruise to nowhere, circling the globe endlessly in near-zero gravity. Aboard the ISS, conditions prevail that laboratories on the Earth’s surface cannot match, conditions that give scientific guests the opportunity to generate unexpected and novel results.
To popularize ISS science cruises to the extent possible, the U.S. government inserted certain provisions into the NASA Authorization Act of 2005. One of these provisions calls for the American segment of the ISS to serve as a national laboratory with the goal of increasing its use by “other federal agencies and the private sector.” ISS partners besides NASA—the space agencies of Russia, Europe, Japan, and Canada—also promote scientific research on the ISS.
By the end of 2020, astronauts had run about 3,000 experiments on the ISS, more than 1,200 of which addressed questions in biology and biotechnology. “In microgravity,” NASA notes, “controls on the directionality and geometry of cell and tissue growth can be dramatically different to those on Earth.” By running life sciences experiments on the ISS, we may gain insights that lead to new therapies, medical devices, and manufacturing technologies.
In a microgravity environment, drug-encapsulating particles that are very, very small—as much as 1,000 times smaller than nanoparticles—can be generated in high-yield processes. These particles are called picoparticles, and they promise to be effective delivery vehicles for drugs that need to be delivered to the brain.
In 2019, an experiment on the ISS was carried out to create picoparticles meant to encapsulate Alzheimer’s drugs. The experiment was organized by Aphios Corporation, Space Technology and Advanced Research Systems (STaARS), the Louisiana State University Health Science Center, and the Center for Advancement of Science in Space (CASIS).
“The production of picoparticles in a microgravity environment will establish novel manufacturing techniques for enhanced drug delivery systems,” said Trevor P. Castor, PhD, president and CEO, Aphios Corporation. “The novel targeted picoparticles produced during this experiment have the potential to improve the delivery of drugs that can arrest progression of or cure Alzheimer’s disease.”
An account of the ISS experiment was supplied to NASA by Craig Walton, the CEO of STaARS. In this account, Walton explains that Aphios’ SuperFluids CFN (Critical Fluid Nanosomes) technology was used to manufacture phospholipid nanosomes (which Aphios calls Bryosomes) and encapsulate an Alzheimer’s drug candidate that is being developed by Aphios. According to Aphios, the drug candidate (Bryostatin-1) is neuroprotective by α-secretase activation via novel protein kinase C isoforms, downregulation of proinflammatory and angiogenic processes, and the substitution of β-amyloid for its soluble and harmless relative, s-APPα.
“The nanosomes are characterized in terms of physical size, chemical content, stability, and biological activity in terms of α-secretase production in neuroblastoma (SH-SY5Y) and human embryonic kidney (HEK-293e) cells,” Walton indicated. “These nanoparticles are then frozen at −80°C.
“Frozen CFNs are then transferred to the ISS, thawed, reconstituted, and refrozen to −96°C after specific time intervals at 37°C. After returning to Earth and thawing at room temperature (25°C), CFNs are characterized in terms of physical size, chemical content, stability, and biological activity in terms of α-secretase production in neuroblastoma (SH-SY5Y) and human embryonic kidney (HEK-293e) cells.”
The average size of the nanoparticles decreased from 88–89 nm to less than 3 nm. In addition, the nanoparticles proved to be more effective. Walton noted, “The size reduction of nanoparticles created in microgravity vastly increases surface area for uptake and delivery, reducing the required dose per treatment and increasing production value by decreasing cost per dose.”
“We want to confirm these studies and eventually manufacture the nanoparticles in a space environment or on the moon,” Castor declared. “More effective products can help humans on Earth with the aging process as well as astronauts and other space travelers.”
Forming drug-releasing gels
Tympanogen, a company that uses gel technology to develop ear, nose, and throat devices, impressed NASA so much that the agency guided the company to CASIS, which manages the ISS National Laboratory. At present, Tympanogen is focused on developing Perf-Fix, an otologic gel patch for nonsurgical ear drum repair.
The company’s long-term goal is to develop medical devices that achieve the targeted delivery of therapeutics. Besides expediting healing at wound sites, therapeutics released from gels could regulate certain physiological activities.
“We received a grant from CASIS to look at gel formation and drug-releasing properties in microgravity conditions,” said Elaine Horn-Ranney, PhD, co-founder and CEO, Tympanogen. “This was an interesting project for both of us because there are no published data on this topic.”
Tympanogen’s implementation partner, Nanoracks, owns a plate reader on the ISS that was used to quantify drug release from the gel over a two-week period. Experiments were run concurrently onboard the ISS and on the ground in Houston.
The first experiment looked at how the gel formed in microgravity. Plates were used that had two wells connected by an openable channel. One well contained the gel material; the other well, the material that initiates gel formation. The second experiment evaluated the release of an antibiotic and a large protein from the gel into a water-filled well.
“During video calls, the scientists did a countdown,” Horn-Ranney recalled. “Both locations opened up the channels at the same time in both experiments, and plate readings were taken simultaneously so that we could directly compare the results from the ISS versus Earth.”
The two sets of gravity conditions produced very different results. Physical characteristics of diffusion change in microgravity conditions, but Horn-Ranney was not sure how that was going to manifest in space. Results are being prepared for publication.
“After getting our first project launched, we have a better idea of [how our] next set of experiments” should be prepared, Horn-Ranney noted. “It is hard for someone inexperienced to appreciate the amount of work that goes into preparing a very simple experiment for launch.”
Developing portable medical devices
“As you miniaturize a device, gravity
has a diminishing impact,” explained Luc Gervais, PhD, founder and CEO, 1Drop
Diagnostics. The company ran ISS experiments that measured the flow of liquids driven only by capillary forces, without the influence of gravity, through the channels of a microfluidic device. The channels were exceptionally small—smaller than any previously used to support capillary flow in space.
Experiments were performed at 1Drop and repeated at the NASA Glenn Research Center, which then helped 1Drop prepare the experiments for transport to the ISS. By ensuring that the experimental setups on the Earth and on the ISS were identical, the research partners hoped to simplify comparisons of the results from the Earth-bound and space-borne experiments.
“Our device materials had to be safe for use on the ISS and also robust enough to withstand acceleration with forces up to 5–10 g,” Gervais pointed out. “We undertook a redesign and replaced glass components with shatterproof plastics and thermoplastics.”
The experiments, which were designed to evaluate fluid dynamics, flow control, particle separation and focusing, and biochemical reactions, generated results demonstrating that microgravity did not impact performance. The experiments also led to improved mathematical models of microfluidic flow control, models that could allow for any environment or any orientation.
“Thanks to these space experiments, we have improved particle separation and focusing, sample filtering, and microfluidic flow control,” Gervais asserted. He suggested that better flow control would lead to next-generation medical diagnostics that could be performed anywhere while saving time, reducing costs, and improving health outcomes.
Previously, 1Drop had worked with the Translational Research Institute for Space Health, a consortium led by Baylor College of Medicine’s Center for Space Medicine, on projects to develop devices to support long-duration space flights such as missions to Mars. Devices that can survive a two-year mission are needed to test travelers for high-priority analytes, such as those that could warn of organ function decline, bone demineralization, and radiation damage.
“Everything that we have developed for NASA has benefitted us and improved the end product,” Gervais declared. “It has been very stimulating, and it is a relationship we value.”
MicroQuin, a biotechnology company that develops drugs to treat breast cancer, launched a project called Microgravity Crystals. The project was designed to reveal the structure of Bax inhibitor 1 (BI-1), an elusive drug target that regulates multiple pathways and is associated with several cancers as well as with many other diseases, including liver diseases, autoimmune diseases, neurodegenerative disorders, diabetes, and viral infections.
Cancerous cells undergo spontaneous cell death upon BI-1 knockdown or loss of function. To exploit this finding, MicroQuin is working to target BI-1 with cell-penetrating peptides/peptidomimetics (CPPs) and protein-based drugs. The CPPs, which can be conjugated with existing drugs, can be custom designed for uptake by specific cells and used as a delivery mechanism.
“BI-1 is very difficult to express or purify, and it is almost impossible to crystallize on Earth, which is why we went to space,” said Scott Robinson, PhD, CSO, MicroQuin. “We invested considerable resources and time into identifying the soluble expression conditions and purification strategy—without success on crystallization.
“Ultimately, the negative data allowed the identification of appropriate strategies to achieve nucleation on the ISS. We got some amazing crystals on the ISS, which we utilized for structural analysis. BI-1 structure will increase our ability to make therapeutics to combat the world’s top diseases.”
MicroQuin is preparing for another experiment on the ISS this year that will assess essential pathways involved in tumorigenesis. Cancer cells act differently in microgravity conditions and turn off certain signaling pathways that can affect cellular function.
“We want to identify what pathways are affected, and how, to allow us to develop better therapeutics to help patients recover quicker and also reduce the toxicity associated with cancer treatment,” Robinson explained. Additional space projects are being proposed that will investigate how latent viruses reactivate in astronauts in space and test how microgravity and associated cellular changes affect both lysogenic reactivation and lytic phages’ life cycle and dissemination.
Biomanufacturing in remote environments
Space projects have been launched to identify biomanufacturing improvements that could address critical supply chain issues and on-demand resource needs in remote and extreme locations. By showing how biological systems change within a microgravity environment, these projects could give biomanufacturers ideas for predicting production output, mitigating negative outcomes, and increasing the likelihood of positive outcomes.
A recent biomanufacturing-related space project was a collaboration between Rhodium Scientific and Clemson University. The project was designed to determine whether microgravity exposure can provide advantages in bioengineered systems for the production of chemical products—with a focus on biomanufacturing biodegradable, 3D printer-compatible polyhydroxyalkonoates, materials that may one day replace plastic packaging.
The project was built around Rhodium Science Chambers, spaceflight hardware that Rhodium developed to control incubation conditions for microbes. “We plan to use our initial space project as the start of a full biomanufacturing program to further develop and refine this technology,” said Olivia Holzhaus, founder and CEO, Rhodium Scientific.
Preflight tests are conducted in the hardware to establish baseline growth capacities prior to sending an experiment to the ISS. Ground experiments are run in parallel on Earth so that when samples return, variations resulting from growth in the microgravity environment can be identified.
For a space science mission, biological samples are loaded into the hardware, delivered to the ISS in a preserved state, and then kept in a sort of holding pattern. The samples wait until the predetermined start time for an experiment arrives. Then incubation proceeds for a predetermined amount of time in orbit. Not many terrestrial science investigations face the challenge of being prepped then paused for nearly a week before an experiment begins. This delay requires specific testing and sometimes creative problem solving to maintain cell viability and functionality.
“Earth’s gravity has biased our fundamental understanding of how biology behaves,” Holzhaus added. “In space, we are relearning many truths once thought to be constants, such as growth and metabolic rates.”
“In our space-based experiments on the ISS, we will explore a strategy for producing recombinant therapeutic proteins for human use during long-range space exploration,” said Albert Schmelzer, PhD, director, Biopharmaceutical Development, R&D, AstraZeneca.
“Our first studies aim to understand the effect of microgravity on therapeutic proteins and the genetic and phenotypic stability of cell lines that make those proteins,” Schmelzer noted. “To date, no systematic understanding exists of how proteins can be manufactured in space using synthetic or cell culture–based techniques, such as the commonly used Chinese hamster ovary (CHO) cells.”
One of the studies to be conducted on the ISS will focus on antibody therapeutic stability and degradation mechanisms. Cells of three different CHO cell types will be loaded, along with cell culture medium, into experimental modules of the Multi-use Variable-g Platform (MVP) system. Each CHO cell type will have been engineered to express a different therapeutic protein.
During the study, half of the modules will spin at 1 g (to simulate Earth’s gravity), and half will stay under microgravity conditions. The MVP system will control carbon dioxide, oxygen, humidity, and temperature within each module to keep cells healthy. A recirculating pump will keep the cells in suspension and adequately aerated. On a regular basis, the cells will be fed fresh medium and diluted to keep them in a healthy, exponentially growing state.
Over the course of the 60-day experiment—the longest study planned on the ISS to date—a portion of the cells will be periodically extracted and cryogenically preserved to allow an assessment of the genetic and phenotypic changes over time. These results will be compared to the “twin” Earth-based control cultures.
“The studies are still in the planning phase,” Schmelzer pointed out. “We hope to launch in late 2021 to early 2022. The ISS provides a unique scientific platform to understand phenomena that would be impossible on Earth.”