We introduce a novel scanning electron microscopy (SEM) method which yields powder electron diffraction patterns. The only requirement is that the SEM microscope must be equipped with a pixelated detector of transmitted electrons. The pixelated detectors for SEM have been commercialized recently. They can be used routinely to collect a high number of electron diffraction patterns from individual nanocrystals and/or locations (this is called four-dimensional scanning transmission electron microscopy (4D-STEM), as we obtain two-dimensional (2D) information for each pixel of the 2D scanning array). Nevertheless, the individual 4D-STEM diffractograms are difficult to analyze due to the random orientation of nanocrystalline material. In our method, all individual diffractograms (showing randomly oriented diffraction spots from a few nanocrystals) are combined into one composite diffraction pattern (showing diffraction rings typical of polycrystalline/powder materials). The final powder diffraction pattern can be analyzed by means of standard programs for TEM/SAED (Selected-Area Electron Diffraction). We called our new method 4D-STEM/PNBD (Powder NanoBeam Diffraction) and applied it to three different systems: Au nano-islands (well diffracting nanocrystals with size ~20 nm), small TbF3 nanocrystals (size < 5 nm), and large NaYF4 nanocrystals (size > 100 nm). In all three cases, the STEM/PNBD results were comparable to those obtained from TEM/SAED. Therefore, the 4D-STEM/PNBD method enables fast and simple analysis of nanocrystalline materials, which opens quite new possibilities in the field of SEM.
Nanodiamonds (ND), especially fluorescent
NDs, represent potentially
applicable drug and probe carriers for in vitro/in vivo applications.
The main purpose of this study was to relate physical–chemical
properties of carboxylated NDs to their intracellular distribution
and impact on membranes and cell immunityactivation of inflammasome
in the in vitro THP-1 cell line model. Dynamic light scattering, nanoparticle
tracking analysis, and microscopic methods were used to characterize
ND particles and their intracellular distribution. Fluorescent NDs
penetrated the cell membranes by both macropinocytosis and mechanical
cutting through cell membranes. We proved accumulation of fluorescent
NDs in lysosomes. In this case, lysosomes were destabilized and cathepsin
B was released into the cytoplasm and triggered pathways leading to
activation of inflammasome NLRP3, as detected in THP-1 cells. Activation
of inflammasome by NDs represents an important event that could underlie
the described toxicological effects in vivo induced by NDs. According
to our knowledge, this is the first in vitro study demonstrating direct
activation of inflammasome by NDs. These findings are important for
understanding the mechanism(s) of action of ND complexes and explain
the ambiguity of the existing toxicological data.
Transformation of nutrients to their nano-form, such as selenium (Se) engineered nanonutrients (Se-ENNs), is expected to enhance the absorption of the nutrients into fish and increase the efficiency of the feed.
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