Development of mammalian embryos exposed to mixed-size nanoparticles

Inhaled or ingested ultrafine nanoparticles and their effects on early pregnancy remain polemic. The objectives of the study were: (a) to determine the embryotoxic effects of nanoparticles at the 2-cell stage and (b) to localize the internalized nanoparticles in the blastocyst. Thawed mouse 2-cell embryos (no. = 128) were exposed to either mixed-size polystyrene-based nanoparticles (11 million/ml) or control G1.3 medium and assessed after 72 hours. Additionally, blastocysts (no. = 146) were exposed to nanoparticles and analyzed. The results showed that the nanoparticles did not inhibit 2-cell embryo development to the blastocyst stage (89.4 vs 96.8%; treated vs control). There were no differences in hatching (34.8 vs 43.5%), implantation (13.6 vs 24.2%) and degeneration (10.6 vs 3.2%). Delayed exposure to nanoparticles showed similar percent hatching (40.7 vs 47.3%) and implantation (17.6 vs 20.0%). Although nanoparticles were internalized, embryo development was not inhibited suggesting a lack of embryotoxicity. During hatching, the larger nanoparticles adhered to the extruding blastocyst, preferentially on trophoblasts, but interference was insignificant. Exposure to polystyrene-based nanoparticles at the concentration tested are not associated with embryonic loss.