Plants Could Serve as Miniature Drug Factories for Astronauts on Deep-Space Missions, UC San Diego Study Shows

Engineers at the University of California San DiegoView company profile have demonstrated a streamlined method for producing pharmaceuticals from plants under space-like conditions, offering a potential solution to one of the most pressing challenges in long-duration spaceflight: maintaining a reliable supply of effective medications.

The findings, published on June 5 in npj Science of Plants, describe a technique that allows researchers to grow and repeatedly harvest therapeutic compounds from plants without destroying them or generating large amounts of waste. The method could also enable low-cost pharmaceutical production in resource-limited areas on Earth.

"With plants, you can grow complex therapeutic compounds using light, water and soil," said study senior author Nicole Steinmetz, the Leo and Trude Szilard Chancellor's Endowed Chair in the Aiiso Yufeng Li Family Department of Chemical and Nano Engineering at the UC San Diego Jacobs School of Engineering. "That's a big advantage over current pharmaceutical manufacturing systems that require giant tanks and sterile environments."

The Medication Expiration Problem in Space

Keeping astronauts supplied with safe, effective medications remains a major obstacle for deep-space exploration. Many drugs degrade more quickly in the space environment. Even aboard the International Space Station, more than half of the medications stocked there have been found to expire within three years. For a round-trip mission to Mars, which can take approximately 200 days each way, this timeline is barely adequate. Regularly resupplying medications is not feasible when crews are millions of miles from Earth.

Plants offer a promising solution because they can act as miniature factories for pharmaceuticals while also helping recycle air and water aboard spacecraft—functions they already serve in space-based cultivation systems.

Producing an Experimental Cancer (search)Search disease Immunotherapy

Steinmetz and her colleagues demonstrated their approach using an experimental therapeutic compound they have studied for more than a decade: cowpea mosaic virus (search)Search drug (CPMV). While CPMV is commonly known for infecting legumes, Steinmetz's team has focused on its ability to stimulate the immune system to attack cancer (search)Search disease cells. CPMV has shown strong anti-tumor effects in preclinical mouse models and in clinical studies in canine cancer patients.

To produce CPMV, the team uses Nicotiana benthamiana (search)Search target and black-eyed pea plants. "Growing the compound in these plants is simple," said study first author Patrick Opdensteinen, a postdoctoral researcher in Steinmetz's lab. "They can produce a whole lot of biomass in a short amount of time, and more biomass equals more product. The main difficulty now is figuring out how to get the product out of the plants."

A Streamlined Extraction Process

Traditional extraction of pharmaceutical products from plants involves picking leaves and grinding them in a blender. "You end up with something that looks like a smoothie, and you can imagine getting your product out of that smoothie is challenging," Opdensteinen said. "The equipment that we use to do this fills our entire lab. You can't fit all that on a spacecraft."

The team turned to a pharmaceutical manufacturing approach known as product secretion, commonly used with bacterial and mammalian cells. Plants naturally secrete products into a compartment inside the leaves called the apoplast, a network of interconnected spaces outside the plasma membrane.

The researchers found they could draw CPMV out of the apoplast while keeping leaves intact. The process involves submerging leaves in a buffer solution inside a sealed vessel, applying vacuum to flood the apoplast with fluid, then gently centrifuging the saturated leaves to draw out the CPMV-rich liquid. The resulting solution is purified through a filter that separates the larger CPMV particles from smaller, unwanted plant material.

The method proved easy to scale: researchers harvested and purified CPMV particles from more than 50 plants in under two hours. Because the leaves remain intact, the plants can continue to grow and potentially be harvested repeatedly.

Simulating Space Conditions

To test the method under space-like conditions, the team collaborated with Professor Maziar Ghazinejad and his lab technicians from the Department of Mechanical and Aerospace Engineering at UCSD. They created a custom-built random positioning machine that continuously rotated the plants to effectively counteract gravity, simulating microgravity.

The plants were also exposed to temperature fluctuations and oxidative stress to mimic the effects of space radiation. In some cases, these stressors slightly increased CPMV yields. The researchers hypothesize this effect may be linked to CPMV's nature as a plant virus. "Plants become more susceptible to disease when stressed, which is usually a disadvantage," Opdensteinen said. "But since our product is derived from a plant virus, we can use that stress response to increase yields."

Next Steps Toward Spaceflight Testing

The team's ultimate goal is to have their method tested on actual space missions. Before that can happen, they will continue studying how space conditions affect plant processes such as water and nutrient uptake. They will also work with the Rocket Propulsion Laboratory at UC San Diego to test how rocket launches affect plant seeds and the genetic materials used in the process.

The research was supported in part by the National Institutes of Health (grant R01CA274640) and the Translational Research Institute for Space Health (TRISH) through NASA Cooperative Agreement NNX16AO69A.