In this work, we report a simple strategy to obtain ultrasensitive SERS nanostructures by self-assembly of Au nanospheres (NSs). This novel protocol allow us to obtain in a reproducible manner Au NS dimers using cucurbit[6]uril (CB[6]) molecules as linkers. The resulting dimers are stable in colloidal dispersion over several days, generating in this way nanostructures with highly reproducible hot spots. This feature is due to the precise subnanometric control of the molecules that generates interparticle distance and, at the same time, of the capability of placing analyte molecules just within these junctions of ultrahigh field enhancement due to the host−guest properties of the CB[6] molecule. The dimer formation is based on the modification of the metal surface with cysteamine molecules (Cys) previous incubation with CB [6] molecules. The cysteamine-functionalized NSs (Cys/ NSs) are positive charged due to the protonation of the amine groups of the Cys molecule at the working pH. These positive groups interact through H-bonds with the carbonyls groups at the portal of the CB[6] molecules. The dimer formation is based on the stoichiometric control between Cys/NPs and CB[6] (ratio 2:1), generating a gap of 1.8 nm and giving rise to SERS enhancements of around 10 8 . The host−guest properties of the CB [6] molecule are used to detect the average SERS enhancement produced by adding methyl viologen (MV) as plasmonic probe. It was found that the average analytical enhancement factor (AEF) for MV is as good as that obtained for the CB[6] itself (around 10 8 ).
In this work, we have developed a controlled method of functionalization of colloidal nanoparticles in solution based in using rigid molecules as linkers (Cucurbituril molecules) which allow us to obtain reproducible hot spots in gold nanoparticle dimers, due to the control of the gap size between the plasmonic structures with subnanometer precision, and at the same time enables placing analyte molecules precisely within these junctions of ultrahigh field enhancement. This novel protocol allows to obtain dimers of Au NPs using cucurbit[6]uril as linker in a reproducible manner that are stable over several days. The sensing performance of these dimeric structures, is by far superior to previous work using supramolecular interactions, as demonstrated by measuring the SERS response of this system using cucurbituril linker as the host and methyl viologen as the guest molecule.
Cholesterol is crucial for the proper functioning of eukaryotic cells, especially neurons, which rely on cholesterol to maintain their complex structure and facilitate synaptic transmission. However, brain cells are isolated from peripheral cholesterol by the blood-brain barrier and mature neurons primarily uptake the cholesterol synthesized by astrocytes for proper function. This study aimed to investigate the effect of aging on cholesterol trafficking in astrocytes and its delivery to neurons. Using in vitro and in vivo models of aging, we found that aged astrocytes accumulated high levels of cholesterol in the lysosomal compartment, and this cholesterol buildup can be attributed to the simultaneous occurrence of two events: decreased levels of the ABCA1 transporter which impairs ApoE-cholesterol export from astrocytes, and reduced expression of NPC1, which hinders cholesterol release from lysosomes. We show that these two events are accompanied by increased microR33 in aged astrocytes, which is known to downregulate ABCA1 and NPC1. In addition, we demonstrate that the microR33 increase is triggered by oxidative stress, one of the hallmarks of aging. By co-culture experiments we also show that aging in vitro impairs the cholesterol delivery from astrocytes to neurons. Remarkably, we found that this altered transport of cholesterol could be alleviated through treatment with endocannabinoids as well as cannabidiol or CBD. Given that reduced neuronal cholesterol affects synaptic plasticity, the ability of cannabinoids to restore cholesterol transport from aged astrocytes to neurons holds significant implications in the field of aging.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.