The increasing use of nanomaterials has raised concerns about their potential risks to human health. Recent studies have shown that nanoparticles can cross the placenta barrier in pregnant mice and cause neurotoxicity in their offspring, but a more detailed understanding of the effects of nanoparticles on pregnant animals remains elusive. Here, we show that silica and titanium dioxide nanoparticles with diameters of 70 nm and 35 nm, respectively, can cause pregnancy complications when injected intravenously into pregnant mice. The silica and titanium dioxide nanoparticles were found in the placenta, fetal liver and fetal brain. Mice treated with these nanoparticles had smaller uteri and smaller fetuses than untreated controls. Fullerene molecules and larger (300 and 1,000 nm) silica particles did not induce these complications. These detrimental effects are linked to structural and functional abnormalities in the placenta on the maternal side, and are abolished when the surfaces of the silica nanoparticles are modified with carboxyl and amine groups.

Carbon nanotubes (CNTs) have been one of the most extensively researched and developed nanomaterials. However, little concern has been placed on their safety. The biological effects of CNTs are believed to differ relative to size and shape. Thus, the relationship between the characteristics of CNTs and their safety needs to be evaluated. In this study, we examined the biological effects of different-sized multi-walled CNTs (MWCNTs) and single-walled CNTs (SWCNTs). Long and thick MWCNTs induced the strongest DNA damage while similar SWCNTs caused little effect. Comparison of inflammatory responses of various types of CNTs found that peritoneal CNT administration of long and thick MWCNTs increased the total cell number in abdominal lavage fluid in mice. These results indicate that long and thick MWCNT, but not short and thin MWCNT, cause DNA damage and severe inflammatory effects. These findings might provide useful information for constructing novel CNTs with safety.

With the increase in use of nanomaterials, there is growing concern regarding their potential health risks. However, few studies have assessed the role of the different physical characteristics of nanomaterials in allergic responses. Here, we examined whether intranasally administered silica particles of various sizes have the capacity to promote allergic immune responses in mice. We used nanosilica particles with diameters of 30 or 70 nm (nSP30 or nSP70, respectively), and conventional micro-sized silica particles with diameters of 300 or 1000 nm (nSP300 or mSP1000, respectively). Mice were intranasally exposed to ovalbumin (OVA) plus each silica particle, and the levels of OVA-specific antibodies (Abs) in the plasma were determined. Intranasal exposure to OVA plus smaller nanosilica particles tended to induce a higher level of OVA-specific immunoglobulin (Ig) E, IgG and IgG1 Abs than did exposure to OVA plus larger silica particles. Splenocytes from mice exposed to OVA plus nSP30 secreted higher levels of Th2-type cytokines than mice exposed to OVA alone. Taken together, these results indicate that nanosilica particles can induce allergen-specific Th2-type allergic immune responses in vivo. This study provides the foundations for the establishment of safe and effective forms of nanosilica particles.