Fetal brain vulnerability to SARS-CoV-2 infection.

Whether or not SARS-CoV-2 can cross from mother to fetus during a prenatal infection has been controversial; however, recent evidence such as viral RNA detection in umbilical cord blood and amniotic fluid, as well as the discovery of additional entry receptors in fetal tissues suggests a potential for viral transmission to and infection of the fetus. Furthermore, neonates exposed to maternal COVID-19 during later development have displayed neurodevelopmental and motor skill deficiencies, suggesting the potential for consequential neurological infection or inflammation in utero. Thus, we investigated transmission potential of SARS-CoV-2 and the consequences of infection on the developing brain using human ACE2 knock-in mice. In this model, we found that viral transmission to the fetal tissues, including the brain, occurred at later developmental stages, and that infection primarily targeted male fetuses. In the brain, SARS-CoV-2 infection largely occurred within the vasculature, but also within other cells such as neurons, glia, and choroid plexus cells; however, viral replication and increased cell death were not observed in fetal tissues. Interestingly, early gross developmental differences were observed between infected and mock-infected offspring, and high levels of gliosis were seen in the infected brains 7 days post initial infection despite viral clearance at this time point. In the pregnant mice, we also observed more severe COVID-19 infections, with greater weight loss and viral dissemination to the brain, compared to non-pregnant mice. Surprisingly, we did not observe an increase in maternal inflammation or the antiviral IFN response in these infected mice, despite showing clinical signs of disease. Overall, these findings have concerning implications regarding neurodevelopment and pregnancy complications of the mother following prenatal COVID-19 exposure.

Improved Charge Extraction Beyond Diffusion Length by Layer-by-Layer Multistacking Intercalation of Graphene Layers inside Quantum Dots Films.

Charge collection is critical in any photodetector or photovoltaic device. Novel materials such as quantum dots (QDs) have extraordinary light absorption properties, but their poor mobility and short diffusion length limit efficient charge collection using conventional top/bottom contacts. In this work, a novel architecture based on multiple intercalated chemical vapor deposition graphene monolayers distributed in an orderly manner inside a QD film is studied. The intercalated graphene layers ensure that at any point in the absorbing material, photocarriers will be efficiently collected and transported. The devices with intercalated graphene layers have superior quantum efficiency over single-bottom graphene/QD devices, overcoming the known restriction that the diffusion length imposes on film thickness. QD film with increased thickness shows efficient charge collection over the entire λ ≈ 500-1000 nm spectrum. This architecture could be applied to boost the performance of other low-cost materials with poor mobility, allowing efficient collection for films thicker than their diffusion length.