A simple, sensitive and cost-effective HPLC-UV bioanalytical method for determination of lopinavir (LPV) in rat and human plasma was developed and validated. The plasma sample preparation procedure includes a combination of protein precipitation using cold acetonitrile and liquid–liquid extraction with n-hexane–ethyl acetate (7:3, v/v). A good chromatographic separation was achieved with a Phenomenex Gemini column (C18, 150 mm × 2.0 mm, 5 μm) at 40°C with gradient elution, at 211 nm. Calibration curves were linear in the range 10–10,000 ng/mL, with a lower limit of quantification of 10 ng/mL using 100 μL of plasma. The accuracy and precision in all validation experiments were within the criteria range set by the guidelines of the Food and Drug Administration. This method was successfully applied to a preliminary pharmacokinetic study in rats following an intravenous bolus administration of LPV. Moreover, the method was subsequently fully validated for human plasma, allowing its use in therapeutic drug monitoring (TDM). In conclusion, this novel, simple and cost-efficient bioanalytical method for determination of LPV is useful for pharmacokinetic and drug delivery studies in rats, as well as TDM in human patients. 相似文献
In order to lower brittleness of biobased polylactic acid (PLA), its blending with polycarbonate and nanosilica is aimed. In this line, to increase compatibility of the ingredients, dicumyl peroxide (DCP) and Cobalt (II) acetylacetonate (Co) were used as grafting and transesterification catalysts, respectively. The X‐ray diffraction (XRD) spectra demonstrated high compatibility of the ingredients by broadening of the PLA characteristic peaks and, also, good dispersion of nanosilica particles, especially in PLA/PC/Silica/Co sample. The EDX maps confirmed good nanosilica dispersion, too. The silica nanoparticle size was ranged from 20 to 100 nm in transmission electron microscopy (TEM) pictures. All nanocomposites showed improved thermal stability in thermogravimetric analysis (TGA). Differential scanning calorimetry (DSC) results demonstrated lower Tg, Tm, and crystallinity values for the fabricated nanocomposites. Notably, the dynamic mechanical thermal analysis (DMTA) curves confirmed the Tg, Tm, and Tcc trend obtained in DSC; moreover, much higher surface under tan δ peak for PLA/PC/Silica/Co sample was obtained, which implies its higher toughness. The precise tensile study of the samples confirmed significantly higher elongation at break of the nanocomposites, more considerably in PLA/PC/Silica/Co sample, with nearly negligible defect on tensile strength and modulus. In a concise, the obtained results confirmed the higher efficiency of Co catalyst, which leads to the sample with improved characteristics compared with DCP. 相似文献
The relative activity coefficients of MnSO4 and Mn(ClO4)2 were measured downto about 5×10–5 mol-kg–1 by means of cells with ion-exchange liquid membranes.The measurements at high dilution provide an answer to the age-old problem ofabsolute values of the activity coefficients for MnSO4. They also lead to acorrection of the activity coefficients for Mn(ClO4)2, whose literature values arefound to be biased by ca. 6.5%. Like other bivalent metal sulfates, MnSO4does not obey the Debye—Hückel law inasmuch as negative instead of positivedeviations from the limiting law are observed in the dilute regions. The possibilityfor this kind of behavior to denote ion association is discussed. The best-fitparameters of Pitzer's equation, able to provide accurate values of the activityand osmotic coefficients of the two salts for any concentration, are reported. 相似文献
The authors describe enzyme based nanobiosensors for continuous monitoring of glucose, with the long term goal of using them as smart diagnostic tattoos. The method is founded on two main features: (1) The fluorescence intensity and decay times of glucose oxidase (GOx) and of GOx labeled with fluorescein (FS) or a ruthenium chelate (Ru) reversibly change during interaction with glucose; (2) The (labeled) enzyme is linked to magnetite magnetic nanoparticles (MNPs) which permits the MNPs to be physically manipulated. It is found that a stable link between MNPs and GOx is only accomplished if the number of amino groups on the GOX is artificially enlarged (to form GOxsam). Fluorescence decay data are best acquired with 8-nm MNPs where scattering is marginal; The activity of GOx is found not to be affected by immobilization on the MNPs. The various immobilized enzymes (GOxsam, GOxsam-FS and GOxsam-Ru; all on MNPs) differ only slightly in terms of linear response to glucose which ranged from 0.5 mM to at least 3.5 mM. The RSDs are about 5% (for n = 5), the detection limits are at ～50 μM, and the sensor lifetimes are >1 week.
Graphical abstract Nanobiosensors consisting of Fe3O4 magnetic nanoparticles linked to glucose oxidase, previously enriched with amino groups (GOxsam) and containing fluorescein (FS) or a ruthenium derivative (Ru), are presented as a new kind of smart tattoos for glucose monitoring.
In this study, a novel, sensitive electrochemical enzyme-based biosensor for urea detection was presented. This biosensor combines a three-electrode system consisting of a classic Glassy Carbon Electrode (GCE) as the working electrode, a platinum counter electrode, and Ag/AgCl as the reference electrode. To construct this urea platform, a GCE was modified with a polyaniline (PANi) film. Then, bacterial urease from Proteus mirabilis was immobilized on the modified GCE (Pm-Urease-PANi-GCE). For the characterization of surface modification, Cyclic Voltammetry (CV) and Scanning Electron Microscope (SEM) were applied, while the Square Wave Voltammetry (SWV) technique was performed for urea detection. The main analytical characteristics of the Pm-Urease-PANi-GCE biosensor showed a good linear range from 0.1 to 10 mM of urea, a limit of detection (LOD) of 0.1 mM, a Michaelis-Menten Km of 0.23 mM, and a sensitivity value 46 μA/mM/cm2. This biosensor allows the detection of urea in solutions, and it could be improved for further medical, environmental, or engineering applications. 相似文献
Four highly porous covalent organic frameworks (COFs) containing pyrene units were prepared and explored for photocatalytic H2O2 production. The experimental studies are complemented by density functional theory calculations, proving that the pyrene unit is more active for H2O2 production than the bipyridine and (diarylamino)benzene units reported previously. H2O2 decomposition experiments verified that the distribution of pyrene units over a large surface area of COFs plays an important role in catalytic performance. The Py-Py-COF though contains more pyrene units than other COFs which induces a high H2O2 decomposition due to a dense concentration of pyrene in close proximity over a limited surface area. Therefore, a two-phase reaction system (water-benzyl alcohol) was employed to inhibit H2O2 decomposition. This is the first report on applying pyrene-based COFs in a two-phase system for photocatalytic H2O2 generation. 相似文献
Here, we report a general approach to the synthesis of the difluoroalkyl bicycloalkanes (CF2-BCAs), as structural surrogates of aryl ketones and ethers. The chemistry is driven by a dihydrobenzoacridine photocatalyst, that engages in a catalytic electron-donor acceptor (EDA) complex, or directly reduces the fluorinated substrate. These two convergent manifolds lead to the generation of the R-CF2 radical, that reacts with the [1.1.1]- or [3.1.1.]-propellane. The method is extremely general, and extendable to complex bioactive molecules (30 examples, up to 87 % yield). The structural features of the CF2-BCP hybrid bioisostere were investigated by single crystal X-ray. Finally, we synthesised a CF2-BCP analogue of a Leukotriene A4 hydrolase inhibitor, replacing the original aryl ether motif. In silico docking studies indicated that this new analogue maintains the same arrangement within the enzyme pocket, profiling the use of the CF2-BCA hybrid bioisostere in medicinal chemistry settings. 相似文献
The production of η mesons has been observed at high momentum transfer in the reaction π−p → nη. The ratio between this cross-section and that for backward charge exchange yields a value for the relative couplings g2ηNN/g2πNN. 相似文献
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