We studied sensor application of a graphene oxide and hematite (α‐Fe2O3/GO) composite electrode well‐characterized by the SEM and XRD. Through differential pulse voltammetry (DPV), oxidation of dexamethasone sodium phosphate (DSP) was studied at the surface of a glassy carbon electrode (GCE) modified with graphene oxide nanosheets (GO) and the α‐Fe2O3/GO composite. The values of the transfer coefficient (α) and the diffusion coefficient (D) of DSP were 0.5961 and 4.71×10?5 cm2 s?1 respectively. In the linear range of 0.1–50 μM, the detection limit (DL) was 0.076 μM. In the second step, a GCE was modified with α‐Fe2O3/GO composite and the DSP measurement step was repeated to analyzed and compare the effects of hematite nanoparticles present on graphene oxide surfaces. According to the results, α and D were 0.52 and 2.406×10?4 cm2 s?1 respectively and the DL was 0.046 μM in the linear range of 0.1–10.0 μM. The sensor is simple, inexpensive and uses blood serum. 相似文献
Dexamethasone, betamethasone and prednisolone are synthetic glucocorticosteroids authorised for therapeutic use in bovine animals within the European Union. Dexamethasone and betamethasone are used mainly for the treatment of metabolic and inflammatory diseases. Prednisolone is used to treat bovine mastitis. Maximum residue limits (MRLs) of 0.3 μg kg−1 for both dexamethasone and betamethasone and 6.0 μg kg−1 for prednisolone in bovine milk have been established. 6α-Methylprednisolone and flumethasone are not authorised for use in bovine animals and are completely banned in bovine milk. The proposed method is based on deprotenisation of milk using 20% (w/v) trichloroacetic acid. Samples are filtered using glass microfibre filters and subject to clean-up using OASIS HLB solid phase extraction. Separation was achieved on a Hypercarb 100 mm × 2.1 mm × 5 μm column. Mobile phase was: 90/10 acetonitrile/0.1% formic acid in water; flow rate was 600 μL min−1. The method allowed the rapid identification and confirmation of the five glucocorticosteroids according to the criteria laid down in Commission Decision 2002/657/EC. Matrix calibration curves for all compounds were linear in the interval 0.0 MRL to 2.0 MRL with a correlation coefficient (r2) higher than 0.96. Relative recoveries ranged from 97% for betamethasone to 111% for prednisolone. Precision at the MRL ranged from 3.8% for prednisolone to 13.8% for betamethasone. Decision limits, CCα, and detection capability, CCβ have been calculated for all compounds. 相似文献
Studies into the interactions between drugs and human serum albumin (HSA) are extremely important for drug discovery, since
HSA behaves as a carrier for external drugs and internal biological molecules. In this paper, to evaluate the pharmacokinetic
and pharmacodynamic properties of dexamethasone (DXM), the interaction between DXM and HSA was studied by capillary electrophoresis–frontal
analysis (CE-FA). According to the Klotz equation, four binding sites between DXM and HSA were obtained, and the average binding
constant was 1.05 × 103 M−1. Furthermore, according to multiple equilibrium theory, based on the assumption that there are two types of binding site,
the binding constant at one site was calculated to be 3.539 × 103 M−1, and the average of the other three was 1.234 × 103 M−1. In addition, to obtain the detailed binding information at each binding site, new equations were deduced by multivariate
regression. The four binding constants of DXM and HSA were calculated to be 5.558 × 101 M−1, 2.158 × 104 M−1, 7.312 × 103 M−1 and 2.043 × 103 M−1, respectively, which is helpful for detailed studies into the interactions between drugs and proteins with multiple binding
sites.
Figure Electropherograms of DXM sodium phosphate and HAS mixtures for different protein to drug concentration ratios, obtained by
CE-FA 相似文献
A simple, sensitive and reliable analytical method for the rapid simultaneous determination of dexamethasone and betamethasone in milk by high performance liquid chromatography–negative electrospray ionization tandem mass spectrometry (HPLC–NESI-MS/MS) with isotope dilution was developed. Samples were directly purified through C18 cartridge. Then the eluate was dried under nitrogen and residues were dissolved in mobile phase. Samples were analyzed by HPLC–MS/MS on a Hypercarb graphite column with a mixture of acetonitrile–water–formic acid as mobile phase. The samples were quantified using dexamethasone-D4 as an internal standard. The procedure was validated according to the European Union regulation 2002/657/EC determining specificity, decision limit (CCα), detection capability (CCβ), trueness, precision, linearity and stability. The method is demonstrated to be suitable for the determination of dexamethasone and betamethasone in milk. The total time required for the analysis of one sample was about 35 min. 相似文献
An electrically controlled drug release (ECDR) system based on sponge-like nanostructured conducting polymer (CP) polypyrrole (PPy) film was developed. The nanostructured PPy film was composed of template-synthesized nanoporous PPy covered with a thin protective PPy layer. The proposed controlled release system can load drug molecules in the polymer backbones and inside the nanoholes respectively. Electrical stimulation can release drugs from both the polymer backbones and the nanoholes, which significantly improves the drug load and release efficiency. Furthermore, with one drug incorporated in the polymer backbone during electrochemical polymerization, the nanoholes inside the polymer can act as containers to store a different drug, and simultaneous electrically triggered release of different drugs can be realized with this system. 相似文献
The present experiments were conducted to determine the effects of dexamethasone mediated changes in tumor water distribution on proton relaxation times (T1, T2) in a murine pancreatic adenocarcinoma (Panc02). Spin lattice (T1) and spin-spin (T2) relaxation times were determined by ex vivo methods (10MHz) and by in vivo imaging techniques (6.25 MHz) at various intervals after single or multiple dexamethasone treatments. In complementary studies, dexamethasone mediated changes in tumor capillary permeability, tumor water distribution, relative tumor blood flow and tumor cell proliferation were also determined.
Proton spin lattice (T1) and spin-spin (T2 relaxation times for Panc02 tumors shortened within two hours of a single dexamethasone treatment. The time course and magnitude of this response was dexamethasone dose dependent. The time dependent changes in T1 and T2 after dexamethasone were similar at 10 MHz (ex vivo) and 6.25 MHz (in vivo imaging). Although dexamethasone produced little or no change in total tumor water content and tumor cell proliferation, transient changes in the physiologic distribution of tumor water were clearly demonstrated.
The data supports the idea that dexamethasone induced changes in the distribution of tumor water were mediated by changes in capillary permeability and tumor blood flow. These physiologic responses produced serial changes in tumor extracellular extravascular water content that were consistent with the observed changes in tumor T1 and T2. The results from these experiments might imply that therapy associated changes in tumor proton relaxation times may not only reflect changes in tissue water content, but may also reflect physiologic responses which alter the distribution of tissue water and solute. 相似文献
The effects of temperature, organic modifier and the type of acid on the retention factor, the resolution and peak shape of betamethasone and dexamethasone are described. The study is performed using narrow bore porous graphitic carbon (PGC) columns online with diode-array detector (DAD) and ESI MS/MS. The results show that temperature affects the retention behaviour of the two compounds and ACN yields the best separation while no effect is obtained by changing the type of organic acid. The developed method is applied for the confirmation of dexamethasone and betamethasone in human urine. 相似文献