Simultaneous determination of colistin sulfate and tigecycline in human plasma by liquid chromatography-tandem mass spectrometry method.

OBJECTIVE: To establish a high-performance liquid chromatography-tandem mass spectrometry method (HPLC-MS/MS) to simultaneously determine colistin sulfate and tigecycline in human plasma. METHODS: Polymyxin B1 internal standard (20 µL) was added into 200 µL of plasma sample. The samples were treated with methanol-5% trichloroacetic acid (50:50, V/V) solution, and the protein precipitation method was adopted for post-injection analysis. The chromatographic column was a Dikma C18 (4.6 mm × 150 mm, 5 µm). For the mobile phase, 0.1% formic acid in aqueous solution was used for phase A, 0.1% formic acid in acetonitrile solution for phase B, and gradient elution was also applied. The flow rate was 0.8 mL/min, the column temperature was 40 °C, and the injection volume was 10 µL; Electrospray ionization and multiple reaction ion monitoring were adopted and scanned by the HPLC-MS/MS positive ion mode. RESULTS: The endogenous impurities in the plasma had no interference in the determination of the analytes. There existed a good linear relationship of colistin sulfate within the range of 0.1-10 µg/mL (R2 = 0.9986), with the lower limit of quantification (LLOQ) of 0.1 µg/mL. There existed a good linear relationship of tigecycline within the range of 0.05-5 µg/ mL (R2 = 0.9987), with the LLOQ of 0.05 µg/mL. The intra- and inter-day relative standard deviations of colistin sulfate and tigecycline were both less than 15%, and the accuracy was between 88.21% and 108.24%. The extraction had good stability, the extraction recovery rate was 87.75-91.22%, and the matrix effect was 99.40-105.26%. CONCLUSION: This study successfully established a method for simultaneously detecting colistin sulfate and tigecycline plasma concentrations. The method was simple, rapid, and highly sensitive and could be applied for therapeutic medication monitoring.

Optimization of C50 Carotenoids Production by Open Fermentation of Halorubrum sp. HRM-150.

C50 carotenoids, as unique bioactive molecules, have many biological properties, including antioxidant, anticancer, and antibacterial activity, and have a wide range of potential uses in the food, cosmetic, and biomedical industries. The majority of C50 carotenoids are produced by the sterile fermentation of halophilic archaea. This study aims to look at more cost-effective and manageable ways of producing C50 carotenoids. The basic medium, carbon source supplementation, and optimal culture conditions for Halorubrum sp. HRM-150 C50 carotenoids production by open fermentation were examined in this work. The results indicated that Halorubrum sp. HRM-150 grown in natural brine medium grew faster than artificial brine medium. The addition of glucose, sucrose, and lactose (10 g/L) enhanced both biomass and carotenoids productivity, with the highest level reaching 4.53 ± 0.32 µg/mL when glucose was added. According to the findings of orthogonal studies based on the OD600 and carotenoids productivity, the best conditions for open fermentation were salinity 20-25%, rotation speed 150-200 rpm, and pH 7.0-8.2. The up-scaled open fermentation was carried out in a 7 L medium under optimum culture conditions. At 96 h, the OD600 and carotenoids productivity were 9.86 ± 0.51 (dry weight 10.40 ± 1.27 g/L) and 7.31 ± 0.65 µg/mL (701.40 ± 21.51 µg/g dry weight, respectively). When amplified with both universal bacterial primer and archaeal primer in the open fermentation, Halorubrum remained the dominating species, indicating that contamination was kept within an acceptable level. To summarize, open fermentation of Halorubrum is a promising method for producing C50 carotenoids.

Excitation Energy-Transfer Processes in the Sensitization Luminescence of Europium in a Highly Luminescent Complex.

The excitation energy transfer (EET) pathways in the sensitization luminescence of EuIII and the excitation energy migration between the different ligands in [Eu(fod)3dpbt] [where fod=6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione and dpbt=2-(N,N-diethylanilin-4-yl)-4,6-bis(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine], exhibiting well-separated fluorescence excitation and phosphorescence bands of the different ligands, were investigated by using time-resolved luminescence spectroscopy for the first time. The data clearly revealed that upon the excitation of dpbt, the sensitization luminescence of EuIII in [Eu(fod)3dpbt] was dominated by the singlet EET pathway, whereas the triplet EET pathway involving T1(dpbt) was inefficient. The energy migration from T1(dpbt) to T1(fod) in [Eu(fod)3dpbt] was not observed. Moreover, upon the excitation of fod, a singlet EET pathway for the sensitization of EuIII luminescence, including the energy migration from S1(fod) to S1(dpbt) was revealed, in addition to the triplet EET pathway involving T1(fod). Under the excitation of dpbt at 410 nm, [Eu(fod)3dpbt] exhibited an absolute quantum yield for EuIII luminescence of 0.59 at 298 K. This work provides a solid and elegant example for the concept that singlet EET pathway could dominate the sensitization luminescence of EuIII in some complexes.

Synthesis and Photophysical Properties of Chalcophenes-Embedded Cycloparaphenylenes.

[ n]Cyclo-4,4'-biphenylene-2″,5″-thienylenes ([ n]CP2T, n = 3, 4), [ n]cyclo-4,4'-biphenyl-ene-2″,5″-selenylenes ([ n]CP2S, n = 3, 4), and [ n]cyclo-4,4'-biphenylene-2″,5″-ethylenedioxythienylenes ([ n]CP2E, n = 3) were synthesized in few steps with high overall yields. These nanorings were prepared through platinum-mediated cyclooligomerization of 2,5-bis(4-pinacolboryl-phenyl)chalcophenes. The X-ray crystallographic analysis of [4]CP2S showed that it employed a cone-shaped conformation in the solid state. Furthermore, their photophysical properties were investigated by using the UV-vis absorption spectra and fluorescence spectra. In particular, selenophene and 3,4-ethylenedioxythiophene-embedded cycloparaphenylenes, which showed significant red shifts in the UV-vis absorption and fluorescence spectra compared with thiophene analogues, are reported here for the first time.