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.

Titanium dioxide (TiO₂) is widely used in pharmaceuticals preparations, cosmetics and as a food additive (E171). It contains microparticles and a fraction of nanoparticles (NPs) which can be absorbed systemically by humans after ingestion. Increasing concern has been aroused about the impact of oral exposure to TiO₂ NPs from dietary and non-dietary sources on human health. In spite of several toxicological studies conducted in recent years, a solid risk assessment of oral exposure to E171 has not been satisfactorily achieved. We investigated whether repeated oral administration of E171 to mice at a dose level (5 mg/kg body weight for 3 days/week for 3 weeks) comparable to estimated human dietary exposure, results in TiO₂ deposition in the digestive system and internal organs, and in molecular and cellular alterations associated with an inflammatory response. To reproduce the first phase of digestion, a new administration approach involving the dripping of the E171 suspension into the mouth of mice was applied. Significant accumulation of titanium was observed in the liver and intestine of E171-fed mice; in the latter a three-fold increase in the number of TiO₂ particles was also measured. Titanium accumulation in liver was associated with necroinflammatory foci containing tissue monocytes/macrophages. Three days after the last dose, increased superoxide production and inflammation were observed in the stomach and intestine. Overall, the present study indicates that the risk for human health associated with dietary exposure to E171 needs to be carefully considered.

Objectives: To define the features of human amniotic mesenchymal stromal cell secretome and its protective properties in experimental models of acute brain injury.Design: Prospective experimental study.Setting: Laboratory research.Subjects: C57Bl/6 mice.Interventions: Mice subjected to sham or traumatic brain injury by controlled cortical impact received human amniotic mesenchymal stromal cells or phosphate-buffered saline infused intracerebroventricularly or intravenously 24 hours after injury. Organotypic cortical brain slices exposed to ischemic injury by oxygen-glucose deprivation were treated with human amniotic mesenchymal stromal cells or with their secretome (conditioned medium) in a transwell system.Measurements and Main Results: Traumatic brain injured mice receiving human amniotic mesenchymal stromal cells intravenously or intracerebroventricularly showed early and lasting functional and anatomical brain protection. cortical slices injured by oxigen-glucose deprivation and treated with human amniotic mesenchymal stromal cells or conditioned medium showed comparable protective effects (neuronal rescue, promotion of M2 microglia polarization, induction of trophic factors) indicating that the exposure of human amniotic mesenchymal stromal cells to the injured tissue is not necessary for the release of bioactive factors. Using sequential size-exclusion and gel-filtration chromatography, we identified a conditioned medium subfraction, which specifically displays these highly protective properties and we found that this fraction was rich in bioactive molecules with molecular weight smaller than 700 Da. Quantitative RNA analysis and mass spectrometry-based peptidomics showed that the active factors are not proteins or RNAs. The metabolomic profiling of six metabolic classes identified a list of molecules whose abundance was selectively elevated in the active conditioned medium fraction.Conclusions: Human amniotic mesenchymal stromal cell-secreted factors protect the brain after acute injury. Importantly, a fraction rich in metabolites, and containing neither proteic nor ribonucleic molecules was protective. This study indicates the profiling of protective factors that could be useful in cell-free therapeutic approaches for acute brain injury.

Gold nanoparticles’ tropism towards the liver is affected by their size and aspect ratio, being co-localised inside the lysosomes of hepatic cells, without changes in their morphology or arising liver toxicity after 47 days of administration.