High-throughput pharmacokinetic method: cassette dosing in mice associated with minuscule serial bleedings and LC/MS/MS analysis

A method for pharmacokinetic studies using cassette dosing associated with serial bleeding in mice is described. PK profiles of four soluble epoxide hydrolase inhibitors were determined following oral, subcutaneous or intraperitoneal administration individually or in cassette dosing. Parent analyses were performed on only 5 μL of whole blood from serial bleeds (up to 10 per animal), by LC/MS/MS. An accuracy (88-100%) and precision (<10% RSD) were observed, leading to reliable datum points for PK calculation. PK profiles, T_max, C_max and half-life values after cassette dosing were similar to the individual PK results. This method dramatically increases speed of data collection while dramatically reducing cost and animal usage. The results presented here clearly indicate that this proposed method could be applicable to high-throughput PK studies.     

Heat capacity of α-glycylglycine in a temperature range of 6 to 440 K

Heat capacity of α-glycylglycine was measured using adiabatic calorimetry (6 to 304 K) and DSC (264 to 443 K), and then thermodynamic functions were calculated. Heat capacity has no anomalies. The molecular crystal melts at 493 K (enthalpy of melting is about 62 kJ mol^–1). The melting is accompanied by decomposition. C _P(T) function for glycylglycine is very similar to those of three glycine polymorphs. The ‘universal’ curve consists of two parts: low-temperature Debye-like function (from 0 to about 120 K) and a straight line (up to the melting point). At very low temperatures rigid molecules oscillate as a whole, and the Debye temperature is proportional to the molecular mass to the power of 3/2.     

An effective and economical method for the storage of plasma samples using a novel freeze-drying device

Biological samples, especially plasma samples, are conventionally stored under freezing conditions to maintain sample integrity prior to the detections of analytes. However, the storage of samples in a low-temperature environment is electric energy consuming, and the preparation of samples prior to analytes detection may be complicated. In this work, an effective and economical method was proposed to freeze-dry the samples using a novel device to allow subsequent storage of samples at ambient temperature. The sample preparations integrated in the new method are simple and easy to follow. Analytes were directly extracted with the extraction agent before sample injections. This new method was validated with quality control (QC) samples of levetiracetam and mycophenolic acid (MPA), and it was also applied to the pharmacokinetic (PK) studies of both drugs in healthy volunteers. When QC samples were stored and prepared with the new method, the detections of analytes were accurate and repeatable, and the analytes maintained stability for a long time. The PK studies of levetiracetam and MPA in healthy volunteers showed that the PK parameters of analytes stored with the new method were consistent with those stored with the conventional method. In conclusion, this effective and economical method is a practical option in reality and can play a big role in clinical and scientific drug researches.     

Optimizing hollow-fiber-based pharmacokinetic assay via chemical stability study to account for inaccurate simulated drug clearance of rifampicin

With increasing multidrug resistance coupled to a poor development pipeline, clinicians are exploring antimicrobial combinations to improve treatment outcomes. In vitro hollow-fiber infection model (HFIM) is employed to simulate human in vivo drug clearance and investigate pharmacodynamic synergism of antibiotics. Our overarching aim was to optimize the HFIM-based pharmacokinetic (PK) assay by using rifampicin and polymyxin B as probe drugs. An ultrapressure liquid chromatography tandem mass spectrometry method was validated for the quantification of rifampicin and polymyxin B components. In vitro profiling studies demonstrated that the experimental PK profiles of polymyxin B monotherapy were well correlated with the human population PK data while monotherapy with rifampicin failed to achieve the expected maximum plasma concentration. Chemical stability studies confirmed polymyxin B was stable in broth at 37 °C up to 12 h while rifampicin was unstable under the same conditions over 12 and 80 h. The calculated mean clearance of rifampicin due to chemical degradation was 0.098 ml/min accounting for 12.2 % of its clinical total clearance (CL?=?0.8 ml/min) based on population PK data. Our novel finding reinforces the importance to optimize HFIM-based PK assay by performing chemical stability study so as to account for potential discrepancy between experimental and population PK profiles of antimicrobial agents.

New whole blood methods and instruments: glucose measurement and test menus for critical care.

A glucose oxidase-H 2O 2 substrate-selective electrode (SSE) along with eight other electrodes allows the Stat Profile 5 (SP5) to measure glucose, electrolytes, blood gases, pH, and hematocrit simultaneously in whole blood. For heparinized blood gas syringe samples (n=178), orthogonal (Deming) regression showed y=0.43 + 1.00x (mmol/L), where y is whole blood glucose, and x is plasma glucose measured with the Ektachem 400 glucose oxidase slide method. For heparinized plasma (n=197), y=0.25 + 1.02x. Least squares linear regression showed y=0.25 + 1.00x (s yxx=0.49) for whole blood versus plasma, y = 0.30 + 1.01x (s yxx=0.49) for plasma versus plasma, and r=0.994 for both cases. Whole blood and plasma glucose in the same samples measured by SSE differed by less than 1%. The SP5 combines the largest number of whole blood tests currently available in a rapid response instrument well-suited for care of the critically ill patient.     

Characterisation of temperature-dependent phase transitions in 2,2-trimethylenedioxy- 4,4,6,6-tetrachlorocyclotriphosphazene, N3P3Cl4[O(CH2)3O]

Background  

The crystal structure of 2,2-trimethylenedioxy-4,4,6,6-tetrachlorocyclo triphosphazene has been determined at 120, 274 and 293 K. The result at 293 K confirms the room temperature Cmc2 ₁ structure, but at the lower temperatures the space group is Pna2 ₁. Nevertheless the basic structure remains the same, with only small displacements of the atoms, amounting to an average of 25 pm between 120 and 293 K.     

Analytical challenges in quantifying abiraterone with LC–MS/MS in human plasma

A method was developed and validated to quantify abiraterone in human plasma. During assay development, several analytical challenges were encountered: limited stability in patient samples, adsorption to glass, coelution with metabolites and carry‐over issues. Limited stability (2 h) was found for abiraterone in fresh plasma as well as whole blood at ambient temperature. When kept at 2–8°C, abiraterone in plasma was stable for 24 h and in whole blood for 8 h. Adsorption of abiraterone to glass materials was addressed by using polypropylene throughout the method. Carry‐over was reduced to acceptable limits by incorporating a third mobile phase into the gradient. The chromatographic separation of abiraterone with its multiple metabolites was addressed by using a longer analytical column and adjusting the gradient. Abiraterone was extracted by protein precipitation, separated on a C18 column with gradient elution and analyzed with tandem quadrupole mass spectrometry in positive ion mode. A stable deuterated isotope was used as the internal standard. The assay ranges from 1 to 500 ng/mL. Within‐ and‐between‐day precisions and accuracies were below 13.4% and within 95–102%. This bioanalytical method was successfully validated and applied to determine plasma concentrations of abiraterone in clinical studies and in regular patient care for patients with metastatic castration‐resistant prostate cancer.     

Measurement of thermo-oxidative stability of isotactic polypropylene by isothermal long-term differential thermal analysis

The thermo-oxidative stability of isotactic polypropylene with different antioxidant concentrations between 0% and 0·1% has been studied using isothermal long-term differential thermal analysis (ILDTA). In the temperature range from 90°C to 210°C the oxidation maximum times were measured up to 2000 h. The Arrhenius plot of the reaction maxima showed straight lines over the whole temperature range, which were not affected by the crystallite melting range. Thus, extrapolations from short-term experiments at elevated temperatures to long-term behaviour at lower temperatures are possible.Ageing tests in a circulating-air oven at 140°C showed that the loss of thermo-oxidative stability with increasing ageing time was nearly linear. So the state of thermo-oxidative deterioration of isotactic polypropylene can be estimated by measurement of residual life time in an ILDTA experiment.The end of the oven life of polypropylene coincided with the loss of mechanical properties which was confirmed by a long-term tensile test at 100°C and 120°C.     

Characterization and electrical transport properties of polyaniline and multiwall carbon nanotube composites

Polyaniline/multiwalled carbon nanotube (PANI/MWNT) composites were prepared by in situ polymerization. Scanning electron microscope, X‐ray diffraction, Fourier transform infrared, Uv‐Visible spectroscopy, Fluorescence spectrophotometry were done to characterize the PANI/MWNT composites. Thermal stability was measured by thermogravimetry analysis. The thermal stability of PANI/MWNT composites becomes higher than PANI. Electrical transport properties of different PANI/MWNT composites were investigated in the temperature range 77 ≤ T ≤ 300 K with and without magnetic field up to 1 T. The dc resistivity of PANI/MWNT composites shows different behavior compared to the sample without MWNT. The room temperature dc magnetoconductivity of the samples is negative; however, its sign changes to positive by lowering the temperature, which has been explained by hopping type charge transport. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1767–1775, 2010     

Determination of the thermal stability of the fullerene dimers C120, C120O, and C120O2

We have produced the fullerene dimers C(120), C(120)O, and C(120)O(2) by a high-speed vibration milling technique. The thermal stability of C(120), C(120)O, and C(120)O(2) has been studied in the temperature range 150-350 degrees C for up to 4 h under vacuum. The bridging oxygen atoms were found to substantially increase the stability of the fullerene dimer molecules.     

A Stability-Indicating LC Assay and Degradation Behavior of Temozolomide Drug Substances

This study deals with a stability indicating HPLC reverse phase method for quantitative determination of temozolomide. A chromatographic separation was achieved on an Inertsil ODS 3V, 250 × 4.6 mm ID, 5 μm column using mobile phase A (buffer 5 mL glacial acetic acid in 1,000 mL of Milli Q water ) and mobile phase B (methanol). Forced degradation studies were performed on bulk sample of temozolomide using acid (0.5 N hydrochloric acid), base (0.5 N sodium hydroxide), oxidation (10% v/v hydrogen peroxide), heat (60 °C) and UV light (254 nm). Degradation of the drug substance was observed in base hydrolysis and oxidation. Degradation product formed under these conditions was found to be Imp-A. When the stress samples were assayed, the mass balance was close to 99.5%. The sample solution was stable up to 48 h at 5 °C and mobile phase was found to be stable up to 48 h at 25 °C. The developed method was validated with respect to linearity, accuracy, precision, robustness and forced degradation studies prove the stability indicating power of the method.     

Plasma protein adsorption: In vitro and ex vivo observations

The in vitro and ex vivo adsorption of blood proteins is studied in order to elucidate the protein-surface interactions which determine the thrombogenicity and thus the applicability of various polymers in blood contacting devices. The in vitro adsorption of albumin and fibrinogen to four polymers shows that at low solution concentrations, more fibrinogen is adsorbed than albumin. At higher solution concentrations, albumin adsorbs in multilayers while fibrinogen adsorbs, and then partially desorbs spontaneously from the surface. Sequential adsorption studies show that fibrinogen and albumin can partially replace each other. Fibrinogen is preferentially adsorbed over albumin in competitive adsorption studies. In ex vivo experiments, more albumin than fibrinogen is adsorbed from blood during the first 120 minutes of whole blood contact. When exposed to flowing whole blood, pre-adsorbed fibrinogen desorbs more rapidly than albumin.     

The stability of doxorubicin and ldarubicin in plasma and whole blood

Summary The stability of doxorubicin and idarubicin was studied in spiked human EDTA-, heparin-plasma and whole blood at room temperature (RT) and at +4°C. The analysis was performed by capillary electrophoresis (CE). Under each sel of conditions, doxorubicin and idarubicin concentrations decreased rapidly with time; the decrease was insignificantly more rapid with doxorubicin. Neither doxorubicinol nor idarubicinol were detectable. In order to obtain comparable plasma levels, doxorubicin and idarubicin containing blood samples should be centrifuged and stored at −20°C immediately.     

Quantitative Analysis of Daporinad (FK866) and Its In Vitro and In Vivo Metabolite Identification Using Liquid Chromatography-Quadrupole-Time-of-Flight Mass Spectrometry

Daporinad (FK866) is one of the highly specific inhibitors of nicotinamide phosphoribosyl transferase (NAMPT) and known to have its unique mechanism of action that induces the tumor cell apoptosis. In this study, a simple and sensitive liquid chromatography–quadrupole-time-of-flight–mass spectrometric (LC-qTOF-MS) assay has been developed for the evaluation of drug metabolism and pharmacokinetics (DMPK) properties of Daporinad in mice. A simple protein precipitation method using acetonitrile (ACN) was used for the sample preparation and the pre-treated samples were separated by a C18 column. The calibration curve was evaluated in the range of 1.02~2220 ng/mL and the quadratic regression (weighted 1/concentration²) was used for the best fit of the curve with a correlation coefficient ≥ 0.99. The qualification run met the acceptance criteria of ±25% accuracy and precision values for QC samples. The dilution integrity was verified for 5, 10 and 30-fold dilution and the accuracy and precision of the dilution QC samples were also satisfactory within ±25% of the nominal values. The stability results indicated that Daporinad was stable for the following conditions: short-term (4 h), long-term (2 weeks), freeze/thaw (three cycles). This qualified method was successfully applied to intravenous (IV) pharmacokinetic (PK) studies of Daporinad in mice at doses of 5, 10 and 30 mg/kg. As a result, it showed a linear PK tendency in the dose range from 5 to 10 mg/kg, but a non-linear PK tendency in the dose of 30 mg/kg. In addition, in vitro and in vivo metabolite identification (Met ID) studies were conducted to understand the PK properties of Daporinad and the results showed that a total of 25 metabolites were identified as ten different types of metabolism in our experimental conditions. In conclusion, the LC-qTOF-MS assay was successfully developed for the quantification of Daporinad in mouse plasma as well as for its in vitro and in vivo metabolite identification.     

Validation and application of a liquid chromatography‐tandem mass spectrometric method for the determination of GDC‐0152 in human plasma using solid‐phase extraction

A liquid chromatography–tandem mass spectrometric (LC‐MS/MS) method was developed and validated for the determination of GDC‐0152 in human plasma to support clinical development. The method consisted of a solid‐phase extraction for sample preparation and LC‐MS/MS analysis in the positive ion mode using TurboIonSpray^TM for analysis. d₇‐GDC‐0152 was used as the internal standard. A linear regression (weighted 1/concentration²) was used to fit calibration curves over the concentration range of 0.02–10.0 ng/mL for GDC‐0152. There were no endogenous interference components in the blank human plasma tested. The accuracy at the lower limit of quantitation was 99.3% with a precision (%CV) of 13.9%. For quality control samples at 0.0600, 2.00 and 8.00 ng/mL, the between‐run %CV was ≤8.64. Between‐run percentage accuracy ranged from 98.2 to 99.6%. GDC‐0152 was stable in human plasma for 363 days at ?20°C and for 659 days at ?70°C storage. GDC‐0152 was stable in human plasma at room temperature for up to 25 h and through three freeze–thaw cycles. In whole blood, GDC‐0152 was stable for 12 h at 4°C and at ambient temperature. This validated LC‐MS/MS method for determination of GDC‐0152 was used to support clinical studies. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis of nonlinear optical polyimides containing azodiamine derivative chromophores and their electrooptic and thermal properties

Some thermally stable second‐order nonlinear optical (NLO) polyimides were synthesized. The polyimides were prepared by the ring‐opening polyaddition of 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride and pyromellitic dianhydride with two aromatic azodiamine derivatives as the NLO chromophores. These chromophores, based on a nitro group connected with azobenzene as the acceptor end of a donor–π‐bridge–acceptor chromophore and a diamine group as the donor end, had specific chemical stability. On the basis of ZERNER'S INDO methods, according to the sum‐over‐states formula, a program for the calculation of nonlinear second‐order optical susceptibilities was devised. The resulting polyimides had high number‐average and weight‐average molecular weights of up to 26,000 and 53,500, respectively, and a large glass‐transition temperature of 248 °C. With an in situ poling and temperature ramping technique, the optimal temperatures (T_opt's) for corona poling were obtained for the largest second‐order NLO response. The electrooptic coefficient (γ₃₃) of a polyimide at a wavelength of 830 nm was up to 21 pm/V after corona poling under its T_opt, and the value remained at elevated temperatures (>90.6% was retained at 240 °C for >120 h). The thermal stability of the NLO polyimides was studied with UV spectrometry after poling of the films. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2478–2486, 2002     

High‐pressure DTA of poly(butylene terephthalate), poly(hexamethylene terephthalate), and poly(ethylene terephthalate)

Pressure effect on the melting behavior of poly(butylene terephthalate) (PBT) and poly(hexamethylene terephthalate) (PHT) was studied by high‐pressure DTA (HP‐DTA) up to 320 and 530 MPa, respectively. Cooling rate dependence on the DSC melting curves of the samples cooled from the melt was shown at atmospheric pressure. Stable and metastable samples were prepared by cooling from the melt at low and normal cooling rates, respectively. DTA melting curves for the stable samples showed a single peak, and the peak profile did not change up to high pressure. Phase diagrams for PBT and PHT were newly determined. Fitting curves of melting temperature (T_m) versus pressure expressed by quadratic equation were obtained. Pressure coefficients of T_m at atmospheric pressure, dT_m/dp, of PBT and PHT were 37 and 33 K/100 MPa, respectively. HP‐DTA curves of the metastable PBT showed double melting peaks up to about 70 MPa. In contrast, PHT showed them over the whole pressure region. HP‐DTA of stable poly(ethylene terephthalate) (PET) was also carried out up to 200 MPa, and the phase diagram for PET was determined. dT_m/dp for PET was 49 K/100 MPa. dT_m/dp increased linearly with reciprocal number of ethylene unit. The decrease of dT_m/dp for poly(alkylene terephthalate) with increasing a segmental fraction of an alkyl group in a whole molecule is explained by the increase of entropy of fusion. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 262–272, 2000     

Dielectric study of low-temperature relaxations in poly(isobutyl methacrylate), poly(n-butyl methacrylate), poly(isopropyl methacrylate), and poly(4-methylpentene-1)

Isochronal measurements of dielectric constant and loss are made for poly(isobutyl methacrylate) (PiBMA), poly(n-butyl methacrylate) (PnBMA), poly(isopropyl methacrylate) (PiBMA), and poly(4-methylpentene-1) (P4MP1) at temperatures ranging from 4°K to 250°K. Loss peaks are found around 120°K (10–100 Hz) for PiBMA, PnBMA, and P4MP1. By comparing the activation energy with the calculated potential barrier for the internal rotation of alkyl group in the side chain, the motion responsible for the 120°K peak is concluded to be essentially the rotation of the isopropyl group as a whole for PiBMA and P4MP1 but, for PnBMA, the rotation of n-propyl group accompanied by the rotation of the end ethyl group. Multiple paths of internal rotation are involved with the 120°K peaks of PiBMA and, in particular, PnBMA, which explain differences between PiBMA and PnBMA in the broadness and the temperature location of the 120°K peak. The 120°K peak is in general assigned to a side chain including a sequence? O? C? C? C or ? C? C? C? C. PiPMA without this sequence in the side chain does not show the 120°K peak, but it exhibits the 50°K peak (1 kHz) like poly(ethyl methacrylate). The 50°K peak is assigned to the rotation of ethyl or isopropyl group attached to COO group. Poly-L-valine in which the isopropyl group is directly attached to carbon does not have the 50°K peak. An additional loss peak at 20°K (1 kHz) for P4MP1 is also discussed on the basis of the calculated potential.     

Temperature variations of NMR second moments for drawn tapes based on polypropylene and polyethylene

Isotropic and drawn tapes prepared from isotactic polypropylene (PP), low density polyethylene (LDPE) and their blend PP/LDPE (70/30) have been studied by broad‐line nuclear magnetic resonance (NMR) in the temperature range from 120 up to 320 K. The glass‐transition temperatures, T_g, for studied samples have been determined from the temperature dependencies of the NMR second moments. It was found that the NMR spectra and their second moments are additive for isotropic blend in the whole temperature range, while a significant differences from addition rule appear for drawn PP/LDPE blend, when weighted average second moment is calculated by means of second moments of equally drawn homopolymers. It was found out that the LDPE component in the blend is drawn to a greater extent than PP component.     

Molecular dynamics study of ferrocene topology under various temperatures

We present the first quantum mechanical Atom-Centered Density-Matrix Propagation molecular dynamic (MD) study to investigate ferrocene (Fc) conformation in gas phase. The MD simulations were performed at several temperatures (7, 18, 80, 120, 180, 293, and 500 K) for a period of 10 ps. It is found that, at very low temperatures (≤18 K), ferrocene prefers eclipsed-like conformation. At higher temperatures (>18 K), the cyclopentadienyl rings (Cp) of ferrocene exhibit apparent fluxional rotations, leading to configurations with the rotational angle δ distributing within a range of 0° (eclipsed) to 18° (approximately half of 36° for the staggered conformation), accompanied by the cyclopentadienyl ring tilt up to approximately 12° at 500 K. The simulated mean inferred (IR) spectrum of ferrocene at 7 K is clearly dominant by a doublet-splitting band of eclipsed-like Fc features in the region of 400 to 600 cm⁻¹, in agreement with previous IR studies. The animation obtained from the MD simulations indicates that, at room temperature, the Fe-C distances in ferrocene are in fact not strictly congruent but 2:2:1-fold.