In this paper, hollow double-shelled TiO2:x%Eu3+@SiO2:y%Tb3+ nanospheres (C1–Ti-x/Si-y) were fabricated using carbon spheres as hard template
followed
by a two-step sol–gel coating process. The results demonstrate
that there is strong interaction between the inner TiO2 layer and outer SiO2 layer, which can be characterized
by the high surface content of Ti–O–Si bonds. The strong
interaction makes it possible to achieve efficient energy transfer
from Tb3+ to Eu3+ ions through crossing the
double-shelled interface. The interfacial energy transfer (IET) efficiency
from Tb3+ to Eu3+ ions is strongly influenced
by the doping concentration of Eu3+ ions whose maximum
is determined to be 30.2%. Furthermore, the surface of inner TiO2 layer is modified by the outer SiO2 layer through
this strong interaction, which significantly enhances the emission
intensity and suppresses the concentration quenching of Eu3+ ions. Under 377 nm excitation, C1–Ti-x/Si-y simultaneously exhibits red and green emissions derived
from Eu3+ and Tb3+ ions, respectively. Moreover,
by varying the doping concentration of Tb3+ and Eu3+ ions, the luminescence color of the samples can be tuned
from green to orange and red. The characterization results show that
our proposed phosphors may provide potential applications in tissue
imaging.
Paneth cells are a group of unique intestinal epithelial cells, and they play an important role in host-microbiota interactions. At the origin of Paneth cell life, several pathways such as Wnt, Notch, and BMP signaling, affect the differentiation of Paneth cells. After lineage commitment, Paneth cells migrate downward and reside in the base of crypts, and they possess abundant granules in their apical cytoplasm. These granules contain some important substances such as antimicrobial peptides and growth factors. Antimicrobial peptides can regulate the composition of microbiota and defend against mucosal penetration by commensal and pathogenic bacteria to protect the intestinal epithelia. The growth factors derived from Paneth cells contribute to the maintenance of the normal functions of intestinal stem cells. The presence of Paneth cells ensures the sterile environment and clearance of apoptotic cells from crypts to maintain the intestinal homeostasis. At the end of their lives, Paneth cells experience different types of programmed cell death such as apoptosis and necroptosis. During intestinal injury, Paneth cells can acquire stem cell features to restore the intestinal epithelial integrity. In view of the crucial roles of Paneth cells in the intestinal homeostasis, research on Paneth cells has rapidly developed in recent years, and the existing reviews on Paneth cells have mainly focused on their functions of antimicrobial peptide secretion and intestinal stem cell support. This review aims to summarize the approaches to studying Paneth cells and introduce the whole life experience of Paneth cells from birth to death.
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