On a long journey to Mars, astronauts face a problem that has no easy fix: their medicines are slowly becoming useless. More than half the medications stored aboard the International Space Station expire within three years—hardly sufficient for a roundtrip voyage that takes about 200 days each way. Resupplying from Earth, millions of miles away, simply isn't an option. But engineers at UC San Diego have found an answer hiding in plain sight: plants.
The research team, led by 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, has developed a method to grow pharmaceuticals directly from plants in space-like conditions. The work, published June 5 in npj Science of Plants, demonstrates that astronauts could one day produce fresh medicines on demand during long missions—transforming plants into compact pharmaceutical factories that require only light, water, and soil.
The advantages of this approach run deep. Traditional pharmaceutical manufacturing relies on giant tanks and sterile laboratory environments. Plants offer something far more elegant: they already thrive in space, help recycle air and water aboard spacecraft, and can be engineered to produce complex therapeutic compounds with remarkable efficiency. "With plants, you can grow complex therapeutic compounds using light, water and soil," Steinmetz explained. The simplicity of this system stands in sharp contrast to the industrial infrastructure that earthbound drug production demands.
To prove the concept, Steinmetz's team worked with an experimental compound they have studied for more than a decade: cowpea mosaic virus, or CPMV. While the virus naturally infects legumes, the researchers have discovered its remarkable ability to stimulate the immune system to attack cancer cells. CPMV has already shown strong antitumor effects in preclinical mouse models and in clinical trials involving canine cancer patients. The team grows CPMV using Nicotiana benthamiana and black-eyed pea plants, which generate large amounts of biomass in remarkably short timeframes.
The true innovation lies in extraction. Normally, harvesting pharmaceuticals from plants means picking leaves, grinding them in a blender, and processing the resulting "smoothie" through equipment that fills an entire laboratory—equipment that could never fit on a spacecraft. The UC San Diego team solved this by mimicking a technique used with bacterial and mammalian cells: product secretion. Plants naturally secrete compounds into a compartment within leaves called the apoplast, a network of spaces outside the plasma membrane. The researchers discovered they could draw CPMV from this compartment while leaving the leaves completely intact.
The process is elegant and simple. Leaves are submerged in buffer solution inside a sealed vessel, then vacuum is applied to flood the apoplast with fluid. The saturated leaves are spun gently in a centrifuge to extract the liquid containing CPMV particles, which are then purified through a fine filter. The entire procedure is remarkably efficient: researchers harvested and purified CPMV from more than 50 plants in under two hours. Because the leaves remain unharmed, the same plants can be harvested repeatedly, again and again.
The implications extend far beyond space exploration. This method could bring affordable pharmaceutical production to resource-limited communities on Earth, democratizing access to life-saving medicines. As astronauts prepare for the long journey to Mars, they may carry something unexpected in their cargo: gardens that heal.