Engineered nanoparticles offer the chance to improve drug transport and delivery through biological barriers, exploiting the possibility to leave the blood circulation and traverse the endothelial vascular bed, blood-brain barrier (BBB) included, to reach their target. It is known that nanoparticles gather molecules on their surface upon contact with biological fluids, forming the "protein corona", which can affect their fate and therapeutic/diagnostic performance, yet no information on the corona's evolution across the barrier has been gathered so far. Using a cellular model of the BBB and gold nanoparticles, we show that the composition of the corona undergoes dramatic quantitative and qualitative molecular modifications during passage from the "blood" to the "brain" side, while it is stable once beyond the BBB. Thus, we demonstrate that the nanoparticle corona dynamically and drastically evolves upon crossing the BBB and that its initial composition is not predictive of nanoparticle fate and performance once beyond the barrier at the target organ.

Purpose Mesoporous silica nanoparticles (MSNPs) are excellent candidates for biomedical applications and drug delivery to different human body areas, the brain included. Although toxicity at cellular level has been investigated, we are still far from using MSNPs in the clinic, because the mechanisms involved in the cellular responses activated by MSNPs have not yet been elucidated. Materials and methods This study used an in vitro multiparametric approach to clarify relationships among size, dose, and time of exposure of MSNPs (0.05–1 mg/mL dose range), and cellular responses by analyzing the morphology, viability, and functionality of human vascular endothelial cells and neurons. Results The results showed that 24 hours of exposure of endothelial cells to 250 nm MSNPs exerted higher toxicity in terms of mitochondrial activity and membrane integrity than 30 nm MSN at the same dose. This was due to induced cell autophagy (in particular mitophagy), probably consequent to MSNP cellular uptake (>20%). Interestingly, after 24 hours of treatment with 30 nm MSNPs, very low MSNP uptake (<1%) and an increase in nitric oxide production (30%, P <0.01) were measured. This suggests that MSNPs were able to affect endothelial functionality from outside the cells. These differences could be attributed to the different protein-corona composition of the MSNPs used, as suggested by sodium dodecyl sulfate polyacrylamide-gel electrophoresis analysis of the plasma proteins covering the MSNP surface. Moreover, doses of MSNPs up to 0.25 mg/mL perturbed network activity by increasing excitability, as detected by multielectrode-array technology, without affecting neuronal cell viability. Conclusion These results suggest that MSNPs may be low-risk if prepared with a diameter <30 nm and if they reach human tissues at doses <0.25 mg/mL. These important advances could help the rational design of NPs intended for biomedical uses, demonstrating that careful toxicity evaluation is necessary before using MSNPs in patients.

This study explored the comet assay as a possible tool to assess genotoxicity in erythrocytes of Columba livia to detect genotoxic effects induced by exposure to urban air pollution. Fieldwork was conducted between June 2004 and June 2005 in the city of Milan, Italy, by sampling pigeons in different areas almost twice a week. Six air contaminants-CO, PM10, NO(2), O(3) (ozone), SO(2), and C6H6-plus polycyclic aromatic hydrocarbons (PAHs) in fine particles, temperature, and ultraviolet index, were considered. Genotoxicity levels, expressed as %DNA migrated, tail moment, and damage index (DI), were always higher in wild pigeons than in pigeons living indoors (controls). Animals exposed to urban air showed significant differences from season to season, and the genotoxic parameters presented the highest values in summer (45.30% +/- 1.40% %DNA migrated, 12.73 +/- 0.80 tail moment, and 22.30 +/- 0.15 x DI x 10(-1)); regression analyses showed a positive relation between DI and O(3) concentrations (P < 0.001). The use of the comet assay DI parameter as a rapid assessment of incipient genotoxic risk by pollution, as measured in C. livia living in urban areas, is also discussed.

The study has explored two conservative biomarkers, porphyrin pattern in guano and methemoglobin levels in blood of Columba livia, in order to assay their potential use for monitoring toxic effects induced by exposure to urban air pollution. Fieldwork was conducted between October 2003 and June 2005 in the city of Milan, Italy, by sampling the pigeons in different areas almost twice a week. Six air contaminants, CO, PM10, NO(2), O(3), SO(2), and C(6)H(6), plus polycyclic aromatic hydrocarbons (PAHs) in fine particles, temperature, and UV index, were considered. Protoporphyrins from pigeon excreta sampled outdoors were always higher than in indoor animals, particularly in winter. A positive correlation (p < 0.001) of protoporphyrin with PAHs was observed. In terms of the values of methemoglobinemia, animals exposed to urban air showed significant differences from season to season but only in summer and autumn did the outdoor pigeons show higher values than indoor animals. In summer, a regression model with a positive correlation between O(3) and benzene was determined (p < 0.01). The use of Columba livia as a sentinel for urban air pollution as well as for detecting complex interactions between contaminants in the urban air pollutant mixture was discussed.

Epidemiological data have related cadmium exposure to neurotoxicity. The combination of multi-level and complementary approaches provides a comprehensive view of mechanistic processes in neurotoxicity.