Development and validation of an LC-MS/MS method for the simultaneous quantification of milbemycin oxime and praziquantel in plasma: application to a pharmacokinetic study in cats.

Introduction: Milbemycin oxime (MBO) and praziquantel (PZQ) have a broad spectrum of biological activity and are commonly used to treat the parasitic infection in the veterinary clinic. In this study, a fast and efficient LC-MS/MS method was established and validated for the simultaneous determination of MBO, PZQ, cis-4-hydroxylated-PZQ (C-4-OH-PZQ) and trans-4-hydroxylated-PZQ (T-4-OH-PZQ) and in cat plasma. Methods: Extraction of analytes and internal standards from cat plasma by acetonitrile protein precipitation, allows rapid processing of large batches of samples. MBO, PZQ, C-4-OH-PZQ, T-4-OH-PZQ, and internal standard (IS) were eluted for 13.5 min on a C18 column with a 0.1% formic acid water/acetonitrile mixture as the mobile phase. Results: Results showed that the method had good precision, accuracy, recovery, and linearity. The linearity range was 2.5-250 ng/mL for MBO, and 10-1000 ng/mL for PZQ, C-4-OH-PZQ, and T-4-OH-PZQ. The intra-day and inter-day precision CV values of the tested components were within 15%. The extraction recoveries of the four components ranged from 98.09% to 107.46%. The analytes in plasma remained stable for 6 h at room temperature, 26 h in the autosampler (4 °C), after freeze-thaw (-20°C) cycles, and 60 days in a -20°C freezer. Method sensitivity sufficed for assessing pharmacokinetic parameters of MBO, PZQ, C-4-OH-PZQ, and T-4-OH-PZQ in plasma samples with LLOQ of 2.5 ng/mL for MBO and 10 ng/mL for PZQ, C-4-OH-PZQ, and T-4-OH-PZQ. Conclusion: In this study, a selective and sensitive LC-MS/MS method for the simultaneous quantification of MBO, PZQ, C-4-OH-PZQ, and T-4-OH-PZQ in cat plasma was developed and validated.This method had been successfully applied to evaluate the pharmacokinetics of MBO, PZQ, C-4-OH-PZQ, and T-4-OH-PZQ after a single oral administration of 8 mg MBO and 20 mg PZQ in cats.

Spherical Fe7S8@rGO nanoflowers as electrodes with high electrocatalytic performance in dye-sensitized solar cells.

Dye-sensitized solar cells (DSSCs) can directly convert solar energy into electricity, and have aroused great research interest from researchers. Here, the spherical Fe7S8@rGO nanocomposites were expediently fabricated by facile methods, and applied in DSSCs as counter electrodes (CEs). The morphological features show the porous structure of Fe7S8@rGO, and it is beneficial to enhance the permeability of ions. Reduced graphene oxide (rGO) has a large specific surface area and good electrical conductivity, shortening the electron transfer path. The presence of rGO promotes the catalytic reduction of I3- ions to I- ions and reduces the charge transfer resistance (Rct). The experimental findings show that the power conversion efficiency (PCE) of Fe7S8@rGO as CEs for DSSCs can reach 8.40% (20 wt% for rGO), significantly higher than Fe7S8 (7.60%) and Pt (7.69%). Therefore, Fe7S8@rGO nanocomposite is expected to be an efficient and cost-effective CE material for DSSCs.

Opto Field-Effect Transistors for Detecting Quercetin-Cu2+ Complex.

In this study, we explored the potential of applying biosensors based on silicon nanowire field-effect transistors (bio-NWFETs) as molecular absorption sensors. Using quercetin and Copper (Cu2+) ion as an example, we demonstrated the use of an opto-FET approach for the detection of molecular interactions. We found that photons with wavelengths of 450 nm were absorbed by the molecular complex, with the absorbance level depending on the Cu2+ concentration. Quantitative detection of the molecular absorption of metal complexes was performed for Cu2+ concentrations ranging between 0.1 µM and 100 µM, in which the photon response increased linearly with the copper concentration under optimized bias parameters. Our opto-FET approach showed an improved absorbance compared with that of a commercial ultraviolet-visible spectrophotometry.

[Seasonal Variations in PM10 and Associated Chemical Species in Jiuxian Mountain in Fujian Province].

PM10 samples were collected at the top of Jiuxian Mountain in Fujian Province from March 2011 to January 2012 and were analyzed for inorganic water-soluble ions and dicarboxylic acids to investigate their seasonal variations and sources. The results showed that PM10 and its associated species exhibited much higher levels in the spring than those in other seasons but the total contribution of the nine species of dicarboxylic acids to PM10 (0.51%±0.41%) was significantly lower than that of the water-soluble ions (18.07%±8.73%). The water-soluble ions were characterized by the highest concentrations of SO42- and NO3-, followed by Na+ and NH4+. Significant positive correlations were observed between cation and anion equivalents, as well as between NH4+ and SO42- or NO3- equivalents. Individual dicarboxylic acid showed a monotonically decreasing trend with increasing carbon number in which oxalic acid accounted for approximately 75% of the total dicarboxylic acids. Characteristic ratios of malonic acid to succinic acid and adipic acid to azelaic acid, MODIS fire spots, and backward trajectories showed that dicarboxylic acids mainly originated from secondary reactions in the atmosphere and that the direct contributions of open biomass burning to dicarboxylic acid concentrations were negligible.

Effect of Temperature on the Growth of Silver Nanoparticles Using Plasmon-Mediated Method under the Irradiation of Green LEDs.

Plasmon-mediated shape conversion of spherical silver nanoparticles (NPs) to nanostructures with other shapes under the irradiation of green LEDs (520 ± 20 nm, 35 mw/cm²) at various temperatures (60, 40, 20, 10, 5, and 0 °C) was performed in this study. It was found that the bath temperature used in the reaction can influence the reaction rates, i.e., the times needed for the shape transformation process were 5, 11.5, 25, 45, 72, and 100 h at 60, 40, 20, 10, 5, and 0 °C, respectively. In addition, the bath temperature can also alter the morphologies of the final products. The major products are silver nanoplates at 60, 40 and 20 °C. However, they became decahedral silver NPs at 5 and 0 °C. The percentages of decahedral silver NPs synthesized at 60, 40, 20, 10, 5, and 0 °C are 0%, 1%, 5%, 45%, 73%, and 89%, respectively. Measuring the surface-enhanced Raman spectroscopy (SERS) spectra of the probe molecule R6G in the presence of KBr showed that both silver nanoplate colloids synthesized at 60 °C and decahedral silver NP colloids synthesized at 0 °C in the absence of PVP had good SERS activities.