Size of the nanovectors determines the transplacental passage in pregnancy: Study in rats

Objective: The objective of the study was to examine whether the size of silicon nanovectors (SNVs) inhibits their entrance into the fetal circulation. Study Design: Pregnant rats were intravenously administered with SNVs or saline. The SNVs were spherical particles with 3 escalating diameters: 519 nm, 834 nm, and 1000 nm. The maternal and fetal distribution of SNVs was assessed. Results: In animals that received 1000 or 834 nm SNV, silicon (Si) levels were significantly higher in the maternal organs vs the saline group, whereas the silicon levels in fetal tissues were similar to controls. However, in animals receiving 519 nm SNVs, fetal silicon levels were significantly higher in the SNV group compared with the saline group (5.93 ± 0.67 μg Si per organ vs 4.80 ± 0.33, P = .01). Conclusion: Larger SNVs do not cross the placenta to the fetus and, remaining within the maternal circulation, can serve as carriers for harmful medications in order to prevent fetal exposure.