Methods and Applications in Fluorescence
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Published By Iop Publishing

2050-6120

Author(s):  
Mara Heckmann ◽  
Gerald Klanert ◽  
Georg Sandner ◽  
Peter Lanzerstorfer ◽  
Manfred Auer ◽  
...  

Abstract Postprandial insulin-stimulated glucose uptake into target tissue is crucial for the maintenance of normal blood glucose homeostasis. This step is rate-limited by the number of facilitative glucose transporters type 4 (GLUT4) present in the plasma membrane. Since insulin resistance and impaired GLUT4 translocation are associated with the development of metabolic disorders such as type 2 diabetes, this transporter has become an important target of antidiabetic drug research. The application of screening approaches that are based on the analysis of GLUT4 translocation to the plasma membrane to identify substances with insulinomimetic properties has gained global research interest in recent years. Here, we review methods that have been implemented to quantitate the translocation of GLUT4 to the plasma membrane. These methods can be broadly divided into two sections: microscopy-based technologies (e.g., immunoelectron, confocal or total internal reflection fluorescence microscopy) and biochemical and spectrometric approaches (e.g., membrane fractionation, photoaffinity labeling or flow cytometry). In this review, we discuss the most relevant approaches applied to GLUT4 thus far, highlighting the advantages and disadvantages of these approaches, and we provide a critical discussion and outlook into new methodological opportunities.


Author(s):  
Sylwia Ryszczyńska ◽  
Tomasz Grzyb

Abstract Recently, the up-converting (UC) materials, containing lanthanide (Ln3+) ions have attracted considerable attention because of the multitude of their potential applications. The most frequently investigated are UC systems based on the absorption of near-infrared (NIR) radiation by Yb3+ ions at around 975-980 nm and emission of co-dopants, usually Ho3+, Er3+ or Tm3+ ions. UC can be observed also upon excitation with irradiation with a wavelength different than 975-980 nm. The most often studied systems capable of UC without the use of Yb3+ ion are those based on the properties of Er3+ ions, which show luminescence resulting from the excitation at 808 or 1532 nm. However, also other Ln3+ ions are worth attention. Herein, we focus on the investigation of the UC phenomenon in the materials doped with Ho3+ ions, which reveal unique optical properties upon the NIR irradiation. The SrF2 NPs doped with Ho3+ ions in concentrations from 4.9% to 22.5%, were synthesized by using the hydrothermal method. The structural and optical characteristics of the obtained SrF2:Ho3+ NPs are presented. The prepared samples had crystalline structure, were built of NPs of round shapes and their sizes ranged from 16.4 to 82.3 nm. The NPs formed stable colloids in water. Under 1156 nm excitation, SrF2:Ho3+ NPs showed intense UC emission, wherein the brightest luminescence was recorded for the SrF2:10.0%Ho3+ compound. The analysis of the measured lifetime profiles and dependencies of the integral luminescence intensities on the laser energy allowed proposing the mechanism, responsible for the observed UC emission. It is worth mentioning that the described SrF2:Ho3+ samples are one of the first materials for which the UC luminescence induced by 1156 nm excitation was obtained.


2021 ◽  
Vol 10 (1) ◽  
pp. 010401
Author(s):  
David J S Birch ◽  
Marcia Levitus ◽  
Yves Mély

Author(s):  
Darja Lisjak ◽  
Maša Vozlič ◽  
Uliana Kostiv ◽  
Daniel Horak ◽  
Boris Majaron ◽  
...  

Abstract The increasing interest in upconverting nanoparticles (UCNPs) in biodiagnostics and therapy fuels the development of biocompatible UCNPs platforms. UCNPs are typically nanocrystallites of rare-earth fluorides codoped with Yb3+ and Er3+ or Tm3+. The most studied UCNPs are based on NaYF4 but are not chemically stable in water. They dissolve significantly in the presence of phosphates. To prevent any adverse effects on the UCNPs induced by cellular phosphates, the surfaces of UCNPs must be made chemically inert and stable by suitable coatings. We studied the effect of various phosphonate coatings on chemical stability and in vitro cytotoxicity of the Yb3+,Er3+-codoped NaYF4 UCNPs in human endothelial cells obtained from cellular line Ea.hy926. Cell viability of endothelial cells was determined using the resazurin-based assay after the short-term (15 min), and long-term (24 h and 48 h) incubations with UCNPs dispersed in the cell-culture medium. The coatings were obtained from tertaphosphonic acid (EDTMP), sodium alendronate, and poly(ethylene glycol)-neridronate. Regardless of the coating conditions, 1−2 nm-thick amorphous surface layers were observed on the UCNPs with transmission electron microscopy. The upconversion fluorescence was measured in the dispersions of all synthesized UCNPs. Surface quenching in aqueous suspensions of the UCNPs was reduced by the coatings. The dissolution degree of the UCNPs was determined from the concentration of dissolved fluoride measured with ion-selective electrode after the aging of UCNPs in water, physiological buffer (i.e., phosphate-buffered saline – PBS), and cell-culture medium. The phosphonate coatings prepared at 80 °C significantly suppressed the dissolution of UCNPs in PBS, while only minor dissolution of bare and coated UCNPs was measured in water and cell-culture medium. The viability of human endothelial cells was significantly reduced when incubated with UCNPs, but it increased with the improved chemical stability of UCNPs by the phosphonate coatings with negligible cytotoxicity when coated with EDTMP at 80 °C.


Author(s):  
Muhammad Farooq Saleem Khan ◽  
Mona Akbar ◽  
Jing Wu ◽  
Zhou Xu

Abstract In recent years, the application of fluorescence spectroscopy has been widely recognized in water environment studies. The sensitiveness, simplicity, and efficiency of fluorescence spectroscopy are proved to be a promising tool for effective monitoring of water and wastewater. The fluorescence excitation-emission matrix (EEMs) and synchronous fluorescence spectra have been widely used analysis techniques of fluorescence measurement. The presence of organic matter in water and wastewater defines the degree and type of pollution in water. The application of fluorescence spectroscopy to characterize dissolved organic matter (DOM) has made the water quality assessment simple and easy. With the recent advances in this technology, components of DOM are identified by employing parallel factor analysis (PARAFAC), a mathematical trilinear data modeling with EEMs. The majority of wastewater studies indicated that the fluorescence peak of EX/EM at 275nm/340nm is referred to tryptophan region (Peak T1). However, some researchers identified another fluorescence peak in the region of EX/EM at 225-237nm/340-381nm, which described the tryptophan region and labeled it as Peak T2. Generally, peak T is a protein-like component in the water sample, where T1 and T2 signals were derived from the <0.20µm fraction of pollution. Therefore, a more advanced approach, such as an online fluorescence spectrofluorometer, can be used for the online monitoring of water. The results of various waters studied by fluorescence spectroscopy indicate that changes in peak T intensity could be used for real-time wastewater quality assessment and process control of wastewater treatment works. Finally, due to its effective use in water quality assessment, the fluorescence technique is proved to be a surrogate online monitoring tool and early warning equipment.


Author(s):  
Juan M. Bujjamer ◽  
Marcos Illescas ◽  
M. Claudia Marchi ◽  
Hernan Edgardo Grecco ◽  
Beatriz C Barja

Author(s):  
Jutta Pauli ◽  
Alejandra. Ramírez ◽  
Claudia Crasselt ◽  
Wolfram Schmidt ◽  
Ute Resch-Genger

Author(s):  
Bartosz Eugeniusz Krajnik ◽  
Lukasz Golacki ◽  
Ewelina Fiedorczyk ◽  
Mateusz Bański ◽  
Agnieszka Noculak ◽  
...  

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