Economical Voltammetric Sensor for Sensitive Rapid Determination of Ondansetron in the Presence of Opioid Antagonist Naltrexone

The electrochemical actions of ondansetron (OND) were investigated on the modified electrode with Polyvinyl Pyrollidone (PVP) and multi-walled carbon nanotube (MWCNTs). The oxidation peak current was enhanced to be doubled when compared to the bare electrode as a result of the synergistic effect of nanomaterial and cation-exchange polymer on the electron transfer rate. Following optimization of the experimental conditions, the Square Wave Voltammograms (SWV) method was employed to determine ondansetron in pharmaceutical formulations. Moreover, the modified electrode MWCNTs/PVP/CPE displayed high selectivity in the voltammetric measurements of ondansetron and co-administrated opioid antagonist drug naltrexone (NAL) with strong potential separation (422 mV). The response peak currents had a linear relationship with drug concentration in the range of (2.00–200.0 nmolL−1) with detection limits 430 pmolL−1 and 456 pmolL−1 for ondansetron and naltrexone, respectively. The electrode was successfully used to detect both medications electrochemically in human plasma samples.

Graphical abstract

Tissue-Engineered Bone Tumor as a Reproducible Human in Vitro Model for Studies of Anticancer Drugs

Studies of anticancer therapies in traditional cell culture models can demonstrate efficacy of direct-acting compounds but lack the 3-dimensional arrangement of the tumor cells and their tissue-specific microenvironments, both of which are important modulators of treatment effects in vivo. Bone cells reside in complex environments that regulate their fate and function. A bioengineered human bone-tumor model has been shown to provide a microphysiological niche for studies of cancer cell behavior. Here, we demonstrate successful transfer between 2 laboratories and utility of this model in efficacy studies using well-established chemotherapeutic agents. The bioengineered human bone-tumor model consisted of Ewing sarcoma (RD-ES) cancer cell aggregates infused into tissue-engineered bone that was grown from human mesenchymal stem cell-derived differentiated into osteoblasts within mineralized bone scaffolds. The tumor model was maintained in culture for over 5 weeks and subjected to clinically relevant doses of linsitinib, doxorubicin, cisplatin, methotrexate, vincristine, dexamethasone, or MAP (methotrexate, doxorubicin, and cisplatin combination). Drug administration cycles were designed to mimic clinical treatment regimens. The bioengineered tumors were evaluated days to weeks after the cessation of treatment to monitor the potential for relapse, using bioengineered bone and ES cell monolayers as controls. Drug binding to the scaffolds and media proteins and gene expression were also evaluated. We show that a bioengineered human bone tumor can be used as a microphysiological model for preclinical studies of anticancer drugs. We found that anticancer efficacy was achieved at concentrations approximating the human Cmax, in contrast to traditional ES cell monolayers. These studies show that the bone-tumor model can be successfully transferred between laboratories and has predictive power in preclinical studies. The effects of drugs on the bone tumors and healthy bone were studied in parallel, in support of the utility of this model for identification of new therapeutic targets.

Determination of Ondansetron by Spectrofluorimetry: Application to Forced Degradation Study, Pharmaceuticals and Human Plasma

The current manuscript describes a validated, responsive and rapid spectrofluorimetric method for quantifying ondansetron (OND) in authentic form, spiked human plasma and dosage forms. This is the first reported fluorescence study of Ondansetron in Triton X 100 system. Various variables affecting fluorescence response were studied precisely and optimised. The described method involved the fluorescence measurement in Triton X 100 system at λ_em/λ_ex 354/317 nm. The calibration plot attained linearity over concentration range of 0.2 - 2 μg/mL. The developed method has been extensively applied to degradation studies of OND as per International Conference on Harmonisation (ICH) guidelines by exposing to oxidative, thermal, photo, acidic and alkaline conditions and also the degradation pathway has been proposed.

Quantification of ondansetron, granisetron and tropisetron in goat plasma using hydrophilic interaction liquid chromatography-solid phase extraction coupled with hydrophilic interaction liquid chromatography-triple quadrupole tandem mass spectrometry

An assay method to quantify ondansetron (OND), granisetron (GRA) and tropisetron (TRO) in goat plasma has been successfully developed and validated. This method procedure for the analysis of OND, GRA and TRO was involved of extracting samples with hydrophilic interaction liquid chromatography (HILIC) solid phase extraction (SPE) and determination by liquid chromatography coupled to tandem mass spectroscopy. An SPE method for the simultaneous extraction of OND, GRA and TRO with high efficiency and selectivity was developed. Prior to HPLC-MS/MS analysis, most of the sources of interference present in the supernatant after protein precipitation of plasma proteins was efficiently removed from the samples by the HILIC SPE treatment. For the quantification of OND, GRA and TRO in the samples, tandem mass spectrometry operating in positive electrospray ionization mode with multiple reaction monitoring was used. The calibration curve was performed in the range of 0.2-20 ng/mL for the target OND, GRA and TRO in goat plasma samples. The precision of the intra- and inter-day assay for OND, GRA and TRO were 1.84-6.23% and 3.89-5.31%, 2.63-6.29% and 3.76-5.31%, 1.99-5.67% and 2.64-4.70%, respectively. The accuracy of the intra- and inter-day assay for OND, GRA and TRO were 89.15-97.39% and 89.46-95.17%, 91.08-100.82% and 91.24-99.47%, 92.30-100.74% and 94.21-97.90%, respectively. For the determination of OND, GRA and TRO in plasma samples, no significant matrix effects were observed. The mean absolute recoveries were 103-150%, 115-121%, and 98-141% for OND, GRA and TRO, respectively. Furthermore, the mean process efficiency values of silica SPE were 98-135%, 92-124%, and 72-109% for OND, GRA and TRO, respectively.

Analytical methods for determination of benzodiazepines. A short review

Benzodiazepines (BDZs) are generally commonly used as anxiolytic and/or hypnotic drugs as a ligand of the GABAA-benzodiazepine receptor. Moreover, some of benzodiazepines are widely used as an anti-depressive and sedative drugs, and also as anti-epileptic drugs and in some cases can be useful as an adjunct treatment in refractory epilepsies or anti-alcoholic therapy. High-performance liquid chromatography (HPLC) methods, thin-layer chromatography (TLC) methods, gas chromatography (GC) methods, capillary electrophoresis (CE) methods and some of spectrophotometric and spectrofluorometric methods were developed and have been extensively applied to the analysis of number of benzodiazepine derivative drugs (BDZs) providing reliable and accurate results. The available chemical methods for the determination of BDZs in biological materials and pharmaceutical formulations are reviewed in this work.

Voltammetric and amperometric determination of metoclopramide on boron-doped diamond film electrode

New methods for the determination of metoclopramide, antiemetic and gastroprokinetic pharmaceutical, were developed, using differential pulse voltammetry (DPV) and flow injection analysis (FIA) with amperometric detection on a boron-doped diamond film electrode. Electrode pretreatment necessary to ensure the stable results was investigated and it was found, that while DPV requires frequent electrode cleaning, FIA with a sufficiently high flow rate can maintain a stable signal with no signs of electrode passivation. The calculated quantification limits of the DPV and FIA with amperometric detection were 0.13 μmol L−1 and 0.015 mmol L−1, respectively. The applicability of the new methods was verified by the determination of metoclopramide in a pharmaceutical preparation. FIA with amperometic detection proved to be sensitive, accurate and, due to the resistance of the electrode to the passivation, also simple to handle.

Voltammetric and amperometric determination of doxorubicin using carbon paste electrodes

Direct current voltammetric (DCV) and differential pulse voltammetric (DPV) determination of antineoplastic agent doxorubicin (DOX) at a carbon paste electrode (CPE) was developed. Britton–Robinson buffer (pH 7.0) was used as a supporting electrolyte. The limits of detection are 8 × 10–7 mol l–1 (DCV) and 6 × 10–8 mol l–1 (DPV). The accumulation of DOX at the electrode surface was used to decrease the limits of detection down to 2.2 × 10–7 mol l–1 for adsorptive stripping DC voltammetry (DCAdSV) and 2.8 × 10–9 mol l–1 for adsorptive stripping differential pulse voltammetry (DPAdSV) at CPE. The results of the voltammetric methods were utilized for the development of a new determination of doxorubicin using HPLC with amperometric detection on CPE based on spherical microparticles of glassy carbon in a wall-jet configuration. A column with chemically bonded C18 stationary phase and a mobile phase containing 0.01 M phosphate buffer (pH 5.0)–methanol 25:75 (v/v) were used. The limit of detection is 4 × 10–7 mol l–1 (HPLC with electrochemical detection (ED)).

The use of recently described ionisation techniques for the rapid analysis of some common drugs and samples of biological origin

Three ionisation techniques that require no sample preparation or extraction prior to mass analysis have been used for the rapid analysis of pharmaceutical tablets and ointments. These methods were (i) the novel direct analysis in real time (DART), (ii) desorption electrospray ionisation (DESI), and (iii) desorption atmospheric pressure chemical ionisation (DAPCI). The performance of the three techniques was investigated for a number of common drugs. Significant differences between these approaches were observed. For compounds of moderate to low polarity DAPCI produced more effective ionisation. Accurate DESI and DAPCI tandem mass spectra were obtained and these greatly enhance the selectivity and information content of the experiment. The detection from human skin of the active ingredients from ointments is reported together with the detection of ibuprofen metabolites in human urine.