Attenuation correction of L-shell X-ray fluorescence computed tomography imaging * LIU Long( ) 1,2 HUANG Yang( ) 1,2 XU Qing( ) 1 YAN Ling-Tong( ) 1 LI Li() 1 FENG Song-Lin( ) 1 FENG Xiang-Qian( ) 1;1)
Chiral metal-organic framework materials, as a new type of porous materials, have attracted much attention in the field of chiral separation. In this paper, a homochiral MOF [Cu(S-mal)(bpy)] n with 3D chiral networks was synthesized by the reaction of ligands (S-malic acid and 4,4'-bipyridine) with copper acetate via a solvothermal method. A packed chiral column for high performance liquid chromatography was fabricated using [Cu(S-mal)(bpy)] n as stationary phase. Before the packing, the MOF crystals was crushed in ethanol applying soft pressure and then the MOF with suitable particle size (5~10 μm) was obtained via solvent suspension. A 4.2 g mass of prepared MOF was suspended in a mixture of hexane and isopropanol. In order to control the packing quality, the suspension of MOF was packed into a stainless steel empty column (25 cm long×4.6 mm i.d.) under 40 MPa using hexane/isopropanol (9∶1, V/V) as the slurry solvent according to a conventional high pressure slurry packing procedure. To investigate the chiral recognition ability of this stationary phase, a series of racemic compounds were separated on the chiral MOF column using different ratio of n-hexane/isopropanol as mobile phase. The results showed that the chiral column exhibited good resolving ability towards 17 racemates, including alcohols, ketones, flavonoids, phenols and amines. For instance, the resolution value of 1-(1-naphthyl)ethanol could reach 4.5. Compared with three kinds of homochiral MOFs columns previously reported by our group, this column showed better chiral recognition ability and higher resolution toward racemates, and has a good complementary for chiral separation. The [Cu(S-mal)(bpy)] n possesses cavities with average dimensions (5 Å×5 Å×6 Å), which were interconnected by narrow windows with diameter ≤3 Å. Therefore, the chiral recognition mostly depends on the surface of the MOF crystal in which the steric fit between the chiral networks and conformation of the solute molecule is the main interactive force. Besides, many other interactions such as the hydrogen-bondings, dispersion forces, dipole-dipole interaction, and π-π interactions which come from the solutes, chiral stationary phase and the mobile phase may also play some role. The reproducibility and stability of the chiral column were evaluated. The results showed that the chiral column showed good reproducibility and stability for enantioseparation. Keywords metal-organic framework; high performance liquid chromatography; S-malic acid; chiral separation
Cysteine (Cys) is a crucial biological thiol that has a vital function in preserving redox homeostasis in organisms. Studies have shown that Cys is closely related to the development of cancer. Thus, it is necessary to design an efficient method to detect Cys for an effective cancer diagnosis. In this work, a novel tumor-targeting probe (Bio-Cy-S) for dualmodal (NIR fluorescence and photoacoustic) Cys detection is designed. The probe exhibits high selectivity and sensitivity toward Cys. After reaction with Cys, both NIR fluorescence and photoacoustic signals are activated. Bio-Cy-S has been applied for the dual-modal detection of Cys levels in living cells, and it can be used to distinguish normal cells from cancer cells by different Cys levels. In addition, the probe is capable of facilitating dual-modal imaging for monitoring changes in Cys levels in tumor-bearing mice. More importantly, the excellent tumor-targeting ability of the probe greatly improves the signal-to-noise ratio of imaging. To the best of our knowledge, this is the first Cys probe to combine targeting and dual-modal imaging performance for cancer diagnosis.
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