Measuring technique for thermal ionisation mass spectrometry of human tracer kinetic study with stable cerium isotopes

Thermal ionisation mass spectrometry (TIMS) method has been developed for the simultaneous detection of different cerium isotopes in biological samples (i.e., blood and urine) at very low concentrations. The work has been done in the frame of a biokinetic study, where different stable cerium isotopes have been administered orally and intravenously as tracers to the human body.

In order to develop an appropriate detection method for the tracers in the biological samples, an optimum sample preparation technique has been set and adapted to the specific requirements of the analysis technique used, i.e., TIMS. For sample evaporation and ionisation, the double tantalum filament technique showed the best results. The ions produced were simultaneously collected on a secondary electron multiplier so that the isotopic ratios of the cerium isotopes in the biological samples could be measured.

The technique has been optimised for the determination of cerium down to 1 ng loaded on the evaporation filament corresponding to cerium concentrations of down to 1 ng ml^?1 in the blood or urine samples. It has been shown that the technique is reliable in application and enables studies on cerium metabolism and biokinetics in humans without employing radioactive tracers.     

Determination of Isotope Enrichment in 13C-or 2H-Labelled Branched-Chain l-Amino Acids From Physiological Fluids by Gas Chromatography-Mass Spectrometry: Use of l-Leucine Dehydrogenase for Specific Preparation of the Quinoxalinol Derivatives

A procedure is described which allows the specific and sensitive estimation of ¹³C- or ²H-label enrichment in branched-chain l-amino acids from physiological fluids: Amino acids are isolated from deproteinized samples by cation exchange chromatography. Specific conversion of branched-chain l-amino acids to their respective 2-oxo acids is achieved by treatment with l-leucine dehydrogenase from Bacillus sp. Reaction of the 2-oxo acids with o-phenylenediamin yields the branched-chain quinoxalinol derivatives which are purified by solid phase extraction. Isotopic label enrichment is then determined by gas chromatographic-mass spectrometric analysis of the O-trimethylsilyl quinoxalinol derivatives using an ammonia-chemical ionisation mode and selected ion monitoring of the quasi-molecular ions [MH]⁺ and [MH + 1]⁺. Applicability of the method is demonstrated by serum analysis in an oral loading test with l-[1-¹³C]leucine.     

Recent progress in tissue optical clearing

Tissue optical clearing technique provides a prospective solution for the application of advanced optical methods in life sciences. This paper gives a review of recent developments in tissue optical clearing techniques. The physical, molecular and physiological mechanisms of tissue optical clearing are overviewed and discussed. Various methods for enhancing penetration of optical‐clearing agents into tissue, such as physical methods, chemical‐penetration enhancers and combination of physical and chemical methods are introduced. Combining the tissue optical clearing technique with advanced microscopy image or labeling technique, applications for 3D microstructure of whole tissues such as brain and central nervous system with unprecedented resolution are demonstrated. Moreover, the difference in diffusion and/or clearing ability of selected agents in healthy versus pathological tissues can provide a highly sensitive indicator of the tissue health/pathology condition. Finally, recent advances in optical clearing of soft or hard tissue for in vivo imaging and phototherapy are introduced.     

Measurement of Glucose Concentration in Blood Plasma Based on a Wireless Magnetoelastic Biosensor

Abstract

A wireless magnetoelastic glucose biosensor in blood plasma is described, based on using a mass sensitive magnetoelastic sensor as transducer. The glucose biosensor was fabricated by coating the ribbon‐like, magnetoelastic sensor with a pH sensitive polymer and a biolayer of glucose oxidase (GOx) and catalase. The pH response polymer swells or shrinks, thereby changing sensor mass loading, respectively, in response to increase or decrease of pH values. The GOx–catalyzed oxidation of the glucose in blood plasma produces gluconic acid, resulting in the pH sensitive polymer shrinking, which in turn decreases the sensor mass loading. The results show that the proposed magnetoelastic glucose biosensor can be successfully applied to determine the concentration of glucose in blood plasma. At glucose concentration range of 2.5–20.0 mmol/l, the biosensor responses are reversible and linear, with a detection limit of 1.2 mmol/l. Since no physical connections between the sensor and the monitoring instruments are required, this proposed biosensor can potentially be applied to in vivo and in situ measurement of glucose concentration in physiological fluids.     

Novel Bis-Crown-Ether Derivatives For Potassium Sensors

Abstract

A variety of bis-benzo-15-crown-5 derivatives were designed and studied with the aim of developing potassium sensors of biological relevance. the significant advantages of bis-/o-nitrophenyl/urethanes have been explained by the existence of NO²-NH hydrogen bonds proved indirectly. the performance characteristics of the prime ligands based sensors were compiled together with potassium assays in biological matrices.     

Solid-Phase Extraction Combined with UHPLC-MS/MS Method for Determination of Remifentanil in Human Whole Blood

A sensitive and reliable method have been developed and validated using solid phase extraction (SPE) combined with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) to determine remifentanil in human blood. Quantification was performed by external standard calibration (r = 0.9991, n = 5). Remifentanil was separated on an ACQUITY UPLC BEH C18 column (50 mm × 2.1 mm, 1.7 µm) and analyzed in positive-ion electrospray-ionization (ESI +) mode. The mobile phase was methanol and water with a gradient elution program. The total run time was 4.5 min and injection volume was 5 μL. Limit of detection (LOD) and limit of quantitation (LOQ) were 0.20 ng/mL and 0.60 ng/mL, respectively. Remifentanil was eluted at 1.89 min. Recoveries of remifentanil ranged between 91.88%–93.79%. The intra-day and the inter-day precision (RSD) for remifentanil were 2.51%–3.48% and 2.76%–3.78%, respectively. The performance of the method was successfully verified for the determination of remifentanil in human blood.     

Direct Determination of Lead in Whole Blood Using Electrothermal Vaporization Inductively Coupled Plasma Atomic Emission Spectrometry

Abstract

A carbon rod atomizer was used for sample introduction into a commercial inductively coupled plasma for the determination of lead in whole blood. Samples of known lead concentration were either treated with Triton-X or nitric acid or diluted 1+5 with distilled water and analyzed by comparison against graphs obtained using aqueous solutions and using the standard additions method. Both approaches produced similar results indicating no appreciable matrix influence. The Pb concentration values obtained were in close agreement with those previously determined by ETA-AAS, Delves′ cup-FAAS and anodic stripping voltammetry. Signal integration and careful selection of the measurement period were critical to obtain accurate results. Derived concentrations were shown to be essentially independent of the heating rate of the vaporization unit and the length of tubing used to transport the material into the plasma. Using a 1 μg ml^?1 lead aqueous standard, a signal to background ratio of 5.5 was obtained under optimized conditions. Relative standard deviations of the blank and the analytical signal were 0.2 and 1.8%., respectively. An aqueous solution detection limit of 0.007 μg ml^?1 was calculated for lead.     

A proteome signature for intrauterine growth restriction derived from multifactorial analysis of mass spectrometry-based cord blood serum profiling

Intrauterine growth restriction (IUGR) is defined as a condition in which the fetus does not reach its genetically given growth potential, resulting in low birth weight. IUGR is an important cause of perinatal morbidity and mortality, thus contributing substantially to medically indicated preterm birth in order to prevent fetal death. We subjected umbilical cord blood serum samples either belonging to the IUGR group (n = 15) or to the control group (n = 15) to fractionation by affinity chromatography using a bead system with hydrophobic interaction capabilities. So prepared protein mixtures were analyzed by MALDI-TOF mass spectrometric profiling. The six best differentiating ion signals at m/z 8205, m/z 8766, m/z 13 945, m/z 15 129, m/z 15 308, and m/z 16 001 were collectively assigned as IUGR proteome signature. Separation confidence of our IUGR proteome signature reached a sensitivity of 0.87 and a specificity of 0.93. Assignment of ion signals in the mass spectra to specific proteins was substantiated by SDS-PAGE in conjunction with peptide mass fingerprint analysis of cord blood serum proteins. One constituent of this proteome signature, apolipoprotein C-III(0) , a derivative lacking glycosylation, has been found more abundant in the IUGR cord blood serum samples, irrespective of gestational age. Hence, we suggest apolipoprotein C-III(0) as potential key-marker of the here proposed IUGR proteome signature, as it is a very low-density lipoprotein (VLDL) and high-density lipoprotein (HDL) member and as such involved in triglyceride metabolism that itself is discussed as being of importance in IUGR pathogenesis. Our results indicate that subtle alterations in protein glycosylation need to be considered for improving our understanding of the pathomechanisms in IUGR.     

LC-ESI-MS/MS determination of paclitaxel on dried blood spots

A simple and rapid high‐performance liquid chromatography–tandem mass spectrometric assay for determination of paclitaxel on rat dried blood spots was developed and validated. The extracted sample was chromatographed without further treatment using a reverse‐phase Oyster ODS3, 4.6 × 50 mm, 3 µm column with mass spectrometry detection. The mobile phase comprised of acetonitrile–water, 60:40 v/v, with a flow rate of 0.4 mL/min was used. The calibration was linear over the range 0.2–20 ng/mL. The limits of detection and quantification were 0.08 and 0.2 ng/mL, respectively. The intra‐ and inter‐day precision (CV%) and accuracy (relative error %) were less than 10 and 12%, respectively. Copyright © 2011 John Wiley & Sons, Ltd.     

Exploring dried blood spot sampling technique for simultaneous quantification of antiretrovirals: lamivudine, stavudine and nevirapine in a rodent pharmacokinetic study

A high‐performance liquid chromatography/positive ion electrospray tandem mass spectrometry method for the simultaneous quantification of lamivudine, stavudine and nevirapine was developed and validated in dried blood spot (DBS) cards. The analytes were separated using an isocratic mobile phase on a reverse phase column and analyzed by MS/MS in the MRM mode using the respective [M + H]⁺ ions, m/z 230–112 for lamivudine, m/z 225–127 for stavudine, m/z 267–226 for nevirapine, m/z 383–337 for zidovudine (IS). The lower limit of quantification was 1 ng/mL for both lamivudine and stavudine and 10 ng/mL for nevirapine. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The method was successfully applied to quantify them in a rat pharmacokinetic study in whole blood, plasma and DBS cards after a single oral co‐administration at the dose of 10, 2 and 13 mg/kg for lamivudine, stavudine and nevirapine, respectively, to male Wistar rats. Following oral administration the pharmacokinetic results in all the matrices are in close agreement. Thus accomplishment of this method would facilitate the ease of collection of clinical samples on DBS cards for lamivudine, stavudine and nevirapine during human clinical trials and therapeutic drug monitoring. Copyright © 2012 John Wiley & Sons, Ltd.