Low embryotoxicity of PEGylated single wall carbon nanotubes

Nanotechnology, the great revolution of the twenty-first century, consists in the preparation of materials, the nanoparticles (NP), having at least one of the dimensions below 100 nm (i.e. less than 10-9 meters). The drastic reduction in size confers to nanoparticles physico-chemical characteristics very different from those of the parent material, since decreasing the size, the surface to volume ratio considerably increases. This in turn determines that the majority of the atoms are distributed at the surface of the nanoparticles, thus conferring them a high chemical and biological reactivity. In the context of engineered nanoparticles, the single-walled carbon nanotubes (SWCNT) are considered one of the most promising materials for applications in both biomedical and industrial fields. There are, however, indications that the SWCNT can be potentially toxic in some biological contexts. For example, we have recently shown that certain types of SWCNT, mainly produced for industrial applications, when administered to female mice at an early stage of pregnancy are capable of inducing fetal malformations of varying severity, up to abortion, in case of administration at high concentrations.This observation raises the question about the safety of exposure to this kind of nanoparticles in the workplace during pregnancy.In this work, we report some of our subsequent results showing that the addition to the carbon nanotubes of functional groups consisting of polyethylene glycol chains (PEG-SWCNT) significantly reduces their embryotoxic effect and do not appear to cause harmful effects in maternal tissues. The functionalization with the polyethylene glycol is, in fact, one of the methods generally used to increase the biocompatibility of many types of nanoparticles. For our study two different experimental protocols were adopted: in the first protocol, a group of pregnant female mice (5.5 day of pregnancy) have been exposed to the test material with a single dose; in a second group of experiments, females at the same stageof gestation, received multiple doses up to day 15 of gestation. This second protocol was chosen in order to mimic the possible daily exposure that a pregnant woman may have in occupational setting. At the end of the experiments the effects observed both at the level of fetal development and health of the mother's tissues were evaluated for both groups. Our results showed that the functionalization is actually able to reduce the toxic effect on the fetus, however, we have observed the occasional appearance of embryos with obvious structural malf