August 5, 2022

Phoebe Stapleton, Ph.D., of Rutgers University, considers herself to be an applied physiologist. That is, she studies how the body works and functions and how it responds to challenges, for better or worse. A researcher in the fields of inhalation toxicology and cardiovascular physiology, she is pioneering innovative research that tracks the movement and effects of inhaled nanoparticles within the body.

Stapleton originally pursued a career in kinesiology and exercise science, noting a passion for working with people in a healthcare context. As she continued her academic journey, she began working as a post-doctoral researcher at West Virginia University (WVU) studying vascular physiology using rodents.

Through this experience she began wondering how something you inhale can move from the lungs to the rest of the body to affect the cardiovascular system.

“I became interested in exploring this movement in the context of pregnancy because of the fascinating vasculature connecting the mother to the fetus,” Stapleton said. “During pregnancy, the fetal circulatory system works differently than after birth and the placenta is a vital, transient organ.”

Tracking Nanoparticle Movement

Stapleton studies how inhaled nanoparticles move throughout mother’s circulatory system, including the placenta, potentially to the developing fetus.

She explained how the ultrafine particulate matter in air pollution falls within the nano size range, and man-made nanomaterials are increasingly used for their diverse properties which make them well suited for a wide array of applications, from pharmaceuticals to sports equipment. But relatively little is known about their effects on the environment and human health.

While others have linked inhaled particulates during pregnancy with risk of developing heart disease later in life among offspring, few studies have focused on the effect of inhaled nanoparticles.

“Monitoring nanoparticle movement between mother and fetus is like trying to find a needle in a haystack,” she explained. “We use as many tools as possible, like fluorescently tagging particles, dark-field microscopy techniques, and Raman spectrometry, which provides information about a chemical’s structure and molecular interactions.”

In one study, Stapleton tracked the movement of inhaled titanium dioxide nanoparticles through the bodies of pregnant rats. The team found that a small percentage of them escaped this initial barrier and reached the placenta, likely through the bloodstream.

Her team also reported that plastic nanoparticles can move from the maternal lung, across the placental barrier, all the way to the fetus.

“We found nanoparticles everywhere we looked in the fetus, including the fetal lung, liver, heart, kidney, and the brain,” Stapleton said. “They were at much lower concentrations than what went into the mother’s lungs, but even one particle crossing several barriers to end up in those vital developing organs seems like too many.”

Exploring Health Effects

Stapleton explained that when nanoparticles migrate from the lungs to the placenta, they can contribute to what she describes as a hostile gestational environment for the fetus.

“The nanoparticles can interfere with the exchange of nutrients and waste between the fetus and the mother, so the fetus’ needs are not being met,” she said.

In one study, her team followed offspring of pregnant rats who inhaled the titanium dioxide nanoparticles to look for potential effects later in life. They found changes in the cellular structure of the heart, alterations to coronary blood flow, and signs of inflammation and degeneration in heart tissue. According to the team, these changes may promote coronary disease in adulthood.

"We're findings nanoparticles where we didn't expect them and effects on offspring later in life, reinforcing how vital pregnancy and early development are," Stapleton said. "My goal is for our research to increase awareness and funding for this type of research so we can develop new tools to detect and track nanoparticles so we can further probe these links."

Next Generation of ONES Awardees

In 2021, Stapleton received the prestigious NIEHS Outstanding New Environmental Scientist (ONES) Award to continue exploring these questions. This grant supports scientists who intend on making a long-term commitment to research in the Environmental Health Sciences and assists them in launching an innovative research program.

“The ONES award gives me full independence and freedom for my laboratory”, explained Stapleton. “The career development aspect has allowed our team to explore new areas, and it opens the door for innovative and collaborative work. For example, we’re starting to look at pregnancy as a vulnerable timepoint for the mother and the fetus as well as the function of the placenta and interactions with nanoparticles.”