More than one in 10 babies in the United States are born at least three weeks before their due date. For these families, what should be a time of joy can instead lead to deep anxiety and a sense of helplessness. The economic consequences are enormous, too: the annual medical and associated costs of these preterm births add up to a staggering $25 billion in the United States alone. 

Even worse, progress on the problem has stalled: Accelerated FDA approval for a progesterone-based injection used to prevent preterm birth was withdrawn in late 2023 because it was not shown to be effective. Today, there is not a single FDA-approved treatment available.

Hannah Zierden, an assistant professor of chemical and biomolecular engineering at the University of Maryland (UMD) and member of the UMD Center of Excellence in Microbiome Sciences, hopes to create one. 

Zierden is currently testing the use of tiny particles known as bacterial extracellular vesicles (bEVs), which are produced by vaginal microbes, as a drug delivery mechanism. These particles, which are released by bacteria, function something like biological “mail” by delivering biological materials and communications from the cell to other parts of the body. Zierden says they could also be loaded with drugs or other materials and targeted to specific cells or tissues.

These bEVs hold particular promise not only because they can move drugs through vaginal mucus, a biological barrier that has proven to be a formidable challenge for scientists in the past, but because they can deliver drugs more precisely than injections, which can get diluted in circulation.

Currently, she is teaming up with fellow chemical and biomolecular engineering assistant professor Po-Yen Chen on a machine learning and AI project to help her identify bEV formulations that can be manufactured at scale and have the greatest potential for success.

Zierden says that advances in bEV drug delivery could re-open the door to the use of progesterone to prevent preterm birth. “When you can deliver drugs directly to the female reproductive tract, you can increase the payload to target tissues while decreasing off-target side effects,” she says.

—Story by Erin Peterson, Engineering at Maryland magazine

Photograph by Maximilian Franz