Schematic representation of the experimental design for the evaluation of PEG-SWCNT embryotoxic potential and biodistribution. Upper panel: Animals were divided into two groups, A and B. Group A received a single administration of either 0.1 (5 females), 10 (10 females) or 30 (10 females) μg/mouse PEG-SWCNTs or PBS (18 females), at 5.5 dpc; group B received three administrations of 10 μg/mouse PEG-SWCNTs (10 females) or PBS (10 females), at different times of gestation. Animals were sacrificed at day 15.5 of gestation and maternal tissues, placentas and fetuses were analyzed. Lower panels: For biodistribution studies, PEG-SWCNT-750 were administered either at 5.5 dpc (5 females) or 14.5 dpc (5 females) and isolated organs studied either at 6.5 dpc or 15.5 dpc, respectively.