Plastic nanoparticles can move from mom to baby through placenta.

Mar 29, 2010

Wick, P, A Malek, P Manser, D Meili, X Maeder-Althaus, L Diener, P Diener, A Zisch, H Krug and U von Mandach. 2010. Barrier capacity of human placenta for nanosized materials. Environmental Health Perspectives 118(3): 432-436.

Synopsis by Thea M. Edwards

Research shows for the first time that plastic nanoparticles can cross the human placenta, possibly exposing the developing fetus to the tiny materials that are increasingly used in medicines, vaccines and personal care products.

Plastic nanoparticles can quickly traverse the human placenta from the mother's side to the developing fetus' side, according to new laboratory research that confirms prior findings from animal studies.

The results confirm that smaller sizes of the manufactured materials are able to cross the placenta at a time toward the end of pregnancy when the membrane barrier between mom and fetus is thinner. The growing brain and other organs may be exposed to the particles, for which health effects are unknown. Researchers suggest more research on the toxic effects of nanoparticles is needed to understand if the fetus is at risk.

Nanomaterials are tiny particles, crafted from atoms of metals, plastics and a variety of other materials. They are increasingly used in engineering applications, as well as medicine and personal care products where their small size helps move drugs and ingredients through the body. At less than 100 nanometers – that's smaller than the diameter of a hair – they behave differently – are more potent and can penetrate deeper – than their larger counterparts.

While not much is known about their toxicity, animal and laboratory studies find the airborne materials can pass into the blood from the lungs and into the brain from the nose. So far, lab studies have found the very small materials can affect brain cells, DNA and lung function. Animal studies point to reproductive changes, embryo death and brain and nerve damage.

The placenta connects a mother to her baby during pregnancy. It acts as both a pipeline – carrying nutrients and waste products from one to the other – and a protective barrier – preventing certain substances from passing through to the fetus. A special cell border, or membrane, that changes during pregnancy separates the mother's side from the fetal side.

The study's authors collected placentas from consenting women immediately after their full-term babies were born. The maternal side of each placenta was injected with a single dose of a solution containing polystyrene nanoparticles. Polystyrene is a widely used plastic that is used to make products like packing peanuts, disposable coffee cups, #6 plastic food packaging and hard plastic items like disposable cutlery and CD cases.

The researchers used polystyrene nanoparticles that were fluorescent so that their migration could be tracked. They tested four different sizes with diameters of 50, 80, 240 or 500 nanometers and used at least four placentas for each nanoparticle size.

The smaller nanoparticles (50, 80, and 240 nm) appeared on the fetal side  of the placenta within 15 minutes after injection, while the larger particles (500 nm) stayed on the maternal side for the six-hour duration of the study.

A one-time exposure, like that evaluated in this study, would mimic a maternal injection rather than an environmental exposure. However, the study clearly illustrates that some nanoparticles are able to pass through the placental membrane from mother to fetus.