'Milestone' discovery may unlock the true biomedical might of natural containers called exosomes

The Gourdie laboratory had a problem of its own making.

The lab at the Fralin Biomedical Research Institute at VTC has spent years exploring how microscopic containers naturally found in raw cow’s milk — called exosomes — can be used to carry medicine through the body. 

Professor Robert Gourdie and his team improved the process for extracting them from milk so dramatically that they suddenly had a new problem: how to store the huge quantities they were producing.

Freezing worked for only a few days, and it damaged the exosomes.

“Ice crystals are like a woodchipper on anything biological,” said Gourdie, Heywood Fralin professor and director of the research institute’s Center for Vascular and Heart Research.

Now, the researchers have found a solution by improving a freeze-drying process that keeps exosomes stable for up to a year at room temperature. It’s a game-changer, allowing them to be consumed in capsule form and shipped without a costly cold-supply chain. It could vastly expand their use in drug delivery, including by Tiny Cargo Co., the startup Gourdie’s lab launched for that purpose.

The discovery is described in a recent article in the Journal of Biological Engineering. 

“This is a milestone toward harnessing exosomes for real-world biomedical use, especially in targeted drug delivery and next-generation diagnostics,” Gourdie said.

Exosomes are released by many cell types. They measure just 30 to 150 nanometers in diameter, and a single quart of raw milk contains trillions. These biological delivery vehicles have shown promise for protecting drugs from degradation or targeting by the body’s hostile gut environment or blood borne immune response, respectively until they reach diseased or damaged areas.

Gourdie’s lab, in search of a way to deliver its lab-developed, wound-healing peptide, created a sophisticated filtration-based process to extract exosomes from milk. Where previous methods based on cultured cells produce only trace amounts, Gourdie’s methods produce them from milk by the pound.

He launched Tiny Cargo to bring the technology to patients.

The team stored the exosomes at minus 80 degrees Fahrenheit, but that process was limiting. If they shipped a batch to Gourdie’s native New Zealand, for example, collaborators there had maybe three days to use them.

Alan Dogan, a Virginia Tech Carilion School of Medicine student working in the lab and the paper’s first author, proposed stabilized exosomes as a research project.

Other labs had tried freeze-drying, technically known as lyophilization, but with limited success. Dogan found that a binder improved stability. After discussion within the lab about the high tryptophan content in colostrum, the first breast milk produced by nursing mothers, and the potential importance of this amino acid to adhesion of exosomes with milk proteins, Dogan tested the amino acid. 

It worked, producing a powdery product that remained stable at room temperature for long periods.

“We think what happens is maybe the tryptophan decorates the outside of the exosomes, prevents them from aggregating together, and also maybe even gives them a little suit of armor,” Gourdie said.

The process not only solves the lab’s storage problem, but alleviates an industrial bottleneck by allowing exosome production and warehousing at scale.

“What this allows for commercial implementation is running through the whole process, putting it on a shelf, and when a customer wants to buy some or to do a project, it's right there,” said Spencer Marsh, chief scientific officer for Tiny Cargo and a research scientist in the Gourdie Lab. 

The company is preparing to supply exosomes loaded with wound-healing compounds to treat radiation exposure in defense and industrial settings and to reduce radiation therapy side-effects in cancer patients.

Without the new process, the exosomes had to be either loaded and frozen in hopes of quick use or produced on demand, requiring frozen shipping.

Now, they can be shipped inexpensively at room temperature and packed into capsules for oral use.

The exosomes, which have rejuvenating properties even without the peptide, can also be stored for use in pharmaceutical cosmetics, such as skin-tightening creams.

“Long term, this discovery goes far beyond the indications Tiny Cargo is working on, and into a massive area that currently relies on cold storage and a cold supply chain,” Marsh said. “This potentially gets rid of that expensive and challenging need for a lot of drugs.”

This work was supported in part by a grant from the National Heart, Lung, and Blood Institute of the National Institutes of Health and a Virginia Catalyst grant designed to facilitate life science projects that advance Virginia’s economy and address major unmet needs for improving human health. It was also supported by a grant supporting cancer research from the Red Gates Foundation.

Gourdie and Marsh are company officers and shareholders at the Tiny Cargo Company Inc., which has licensed technology from Virginia Tech.

News release by Matt Chittum/Virginia Tech