Wide Calibration Research Articles

Calibration of the IXPE Focal Plane X-Ray Polarimeters to Polarized Radiation

The Imaging X-ray Polarimetry Explorer (IXPE) is a NASA Small Explorer mission—in partnership with the Italian Space Agency—dedicated to X-ray polarimetry in the 2–8 keV energy band. The IXPE telescope comprises three grazing incidence mirror modules coupled to three detector units hosting each one a Gas Pixel Detector, a gas detector that allows measuring the polarization degree by using the photoelectric effect. A wide and accurate ground calibration was carried out on the IXPE Detector Units at INAF-IAPS, in Italy, where a dedicated facility was setup at this aim. In this paper, we present the results obtained from this calibration campaign to study the IXPE focal plane detector response to polarized radiation. In particular, we report on the modulation factor, which is the main parameter to estimate the sensitivity of a polarimeter.

MO571: Novel Insights Into Uremic Toxins in CKD: Rapid Detection of Microbiota-Derived Indoxyl Sulfate in CKD Patients

Abstract BACKGROUND AND AIMS Emerging evidence suggest that uremic toxins are involved in the progression of chronic kidney disease (CKD). Indoxyl Sulfate (IxS) is one of the most studied since resulted as strong predictor of cardiovascular disease (CVD) and linked with the prognosis of patients with CKD. Indeed, blood levels of IxS increase during CKD stages reaching a maximum in patients with end-stage renal disease (ESRD). Additionally, hemodialysis is able to eliminate only the blood-free fraction as the IxS albumin bond hides its removal. As a result, patients on dialysis show the highest IxS levels resulting in worsening condition, enhancement of CVD-related complication. Thus, IxS rapid quantification could offers clinicians an alternative method for monitoring CKD progression and address the dialysis effectiveness. Liquid chromatography/tandem mass spectrometry (LC-MS/MS) is commonly used for IxS detection and require dedicated equipment and skills, long analysis times and costly analytical instruments. To address these issues, the development of a simple and rapid analytical method for IxS detection is needed. Here, we present a study focused on the development and validation of a rapid and simple method of IxS determination based on colorimetric array-based analysis exploitable in clinical practice for CKD patients. METHOD A total of 20 blood samples (10 healthy people and 10 CKD patients) were used to assess the feasibility of our colorimetric assay. IxS from serum sample was quantified at time of inclusion by LC-MS/MS. Next, from the same samples, we used a derivatization reaction for splitting the serum IxS into indigo-blue. This method enables the rapid quantification of IxS-derived indigo by a smart spectrophotometer at λ = 420–450 nm. Analyte concentration was instantly calculated from absorbance/concentration calibration curve of indigo-blue. Finally, a correlation between the two methods were carried out for the colorimetric analysis validation. RESULTS To accurately determine concentrations of IxS in the low µM range for practical diagnostic purposes, a wide linear calibration curve of was successfully established. The calibration curve ranged from ‘0 µM to 330 µM’ for indigo blue. The regression equation between absorbance and concentration was y = 0.0003 x + 0.0192, and the correlation coefficient (r2) was 0.9941. The feasibility was confirmed by detecting IxS in serum samples from healthy people and CKD patient. A positive correlation was observed between IxS quantified by LC-MS/MS and IxS-derived indigo quantified by spectrophotometry (P < 0 001, r = 0.088). Furthermore, the results of colorimetric analysis were compared with those obtained using LC–MS/MS, and no significant difference was found between them (Fig. 2). This result indicated that the colorimetric detection of IxS is comparable to LC–MS/MS, but it is simpler and faster for CKD monitoring in clinical practice. CONCLUSION The aim of our study was to develop and validate a quantitative method for the rapid estimation of serum IxS employable to monitor CKD progression in clinical setting, identify patient at risk and help further dialysis therapies aimed to lowering blood uremic toxins. Conventionally, LC-MS/MS is the most used diagnostic tool for the IxS quantification due to high sensitivity and accuracy. However, the great rigorousness analysis together with the requirement of real-time results hinders its employment in the clinical practice. Our results provide a low-cost, easy-to-operate, label-free, rapid and sensitive method for IxS determination for application in tracking IxS in blood and studying CKD progression.

Aptamer-Initiated Catalytic Hairpin Assembly Fluorescence Assay for Universal, Sensitive Exosome Detection.

Cancer-cell-derived exosomes are regarded as noninvasive biomarkers for early cancer diagnosis because of their critical roles in intercellular communication and molecular exchange. A robust aptamer-initiated catalytic hairpin assembly (AICHA) fluorescence assay is proposed for universal, sensitive detection of cancer-derived exosomes. The AICHA was verified with the specific detection of MCF-7 cell-derived exosomes with a wide calibration range of 8.4 particles/μL to 8.4 × 105 particles/μL and a low detection limit (LOD) of 0.5 particles/μL. The universality of the AICHA method was verified for PANC-1 cell-derived exosomes, the LOD of which was determined to be 0.1 particles/μL. The performances in serum samples were detected with a recovery rate range of 95.45-106.2%, which demonstrates its significant potential for protein biomarker analysis and cancer diagnosis.

28-GHz CMOS Direct-Conversion RF Transmitter with Precise and Wide-Range Mismatch Calibration Techniques

A millimeter-wave direct-conversion radio-frequency (RF) transmitter requires precise in-/quadrature-phase (I/Q) mismatch calibration and dc offset cancellation to minimize image rejection ratio (IRR) and LO feedthrough (LOFT) for ensuring satisfactory output spectral purity. We present a 28-GHz CMOS RF transmitter with an improved calibration technique for fifth generation (5G) wireless communication applications. The RF transmitter comprises a baseband amplifier, quadrature up-conversion mixer, power amplifier driver, and quadrature LO generator. The I/Q amplitude mismatch is calibrated by tuning the gate biases of the switching stage FETs of the mixer, the I/Q phase mismatch is calibrated by tuning the varactor capacitances at the LC load of LO buffer, and the dc offset is cancelled by tuning the body voltages of the differential-pair FETs at the baseband amplifier. The proposed technique provides precise calibration accuracy by employing mV-resolution tuning voltage generation via 6-bit voltage digital-to-analog converters. It also covers wide calibration range while minimizing the impact on the circuit’s bias point and dissipated current during calibration. Implemented in a 65 nm CMOS process, the RF transmitter integrated circuit shows output-referred 1 dB compression power of +6.5 dBm, saturated output power of +12.6 dBm, and an operating band of 27.5–29.3 GHz while demonstrating satisfactory performances of −55.9 dBc of IRR and −36.8 dBc of LOFT.

An UHPLC-MS/MS method for quantification of the CDK4/6 inhibitor abemaciclib in human serum

BackgroundAbemaciclib is a new oral targeted treatment option for patients with advanced breast cancer. The emerging field of oral antitumor therapeutics presents challenges for both patients and healthcare teams; non-adherence and high inter-individual pharmacokinetic variability can influence response rates. MethodsFor monitoring abemaciclib in human sera, a rapid novel ultra-high-performance liquid chromatography-tandem mass spectrometry method was developed and fully validated. Sample preparation was based on a protein precipitation step followed by on-line solid phase extraction. Chromatographic separation was achieved using a biphenyl column and the isotope labeled standard abemaciclib-d8 was used for quantification. ResultsThe method showed linearity over a wide calibration range from 20.0 to 2500 ng/mL. With accuracies and precisions of ≤13.9% and ≤4.42%, respectively, the validation results were within the criteria of acceptance. The fitness of the method was tested by monitoring abemaciclib levels under compassionate use for a single individual. ConclusionsThe novelty of the presented two dimensional isotope dilution UHPLC-MS/MS method is in the semi-automated sample preparation, which results in negligible matrix effects, thereby allowing the introduction of abemaciclib into robust routine therapeutic drug monitoring (TDM). This method provides an efficient tool to verify the usefulness of personalized anticancer therapy in clinical practice.

Dual biomineralized metal−organic frameworks-mediated conversion of chemical energy to electricity enabling portable PEC sensing of telomerase activity in bladder cancer tissues

In this work, we report on a portable photoelectrochemical (PEC) sensing system for telomerase activity detection based on dual biomineralized ZIF-8 nanoparticles (NPs)-medicated conversion of chemical energy to electricity and terminal deoxynucleoside transferase (TdTase)-catalyzed elongation of Y-junction DNA structure. Two kinds of biomineralized ZIF-8 NPs including glucose oxidase (GOx)-encapsulated ZIF-8 (GZIF) and horseradish peroxidase (HRP)-encapsulated ZIF-8 (HZIF) are involved in this assay system. The recognition of telomerase is started with telomerase-catalyzed elongation of a telomerase substrate (TS) primer, which generates a longer elongation chain to trigger the formation of a Y-junction DNA structure. The Y-junction DNA with abundant 3′-OH terminal and small steric hindrance facilitates the implement of TdTase-catalyzed elongation reaction, in which the branches of Y-junction DNA are elongated and endowed with biotin moiety to capture streptavidin-modified GZIF (SA-GZIF). The signal transduction is then achieved on a luminol/HZIF/CdS-based photoelectrode. Once the H2O2 produced from GZIF-catalyzed hydrolysis of glucose is introduced to the photoelectrode, chemiluminescence of HRP-luminol–H2O2–p-iodo-phenol (PIP) system confined in HZIF is activated to excite photocurrent of CdS NPs, which is then recorded by a portable digital multimeter (DMM). The developed PEC sensing system possesses a wide calibration range from 50 to 5000 HeLa cells and a low detection limit of 46 cells. Significantly, the sensing platform is successfully applied to evaluate the telomerase activity in resected bladder tumor tissues. This work not only provides a diagnostic tool for telomerase-related diseases but also open a new avenue for establishing PEC assay methods using metal-organic framework (MOF) NPs.

Новые данные по хронологии и стратиграфии памятника Ракушечный Яр

Rakushechny Yar site, located in the Lower Don basin, is a multilayered floodplain settlement with a series of buried soils, where Neolithic-Eneolithic and Bronze Age cultural layers have been investigated. Dates with a wide calibration interval for materials from excavation # 1 obtained from total organic content of ceramics, food crust, and charcoal previously demonstrated the length of the Early Neolithic period ranging from the mid 7th millennium BC to the end of the 6th millennium cal BC. The new data allowed us to significantly adjust chronology of the site. A new series of dating based on animal bones from the Early Neolithic layers concentrate within a narrow chronological interval of a few decades around 5600 cal BC. This suggests that burying of archaeological remains was very rapid, and sand interlayers which separated them do not form significant temporal hiatuses. The archaeological layers are distributed within restricted surfaces and correspond to different episodes of coastal zone inhabitation. The variation in the number, thickness and character of the archaeological layers points to repeated episodes of inhabitation during Early Neolithic. The time when the Early Neolithic strata might have been closed differs at various parts – from the 5th mill to the 4th millennium cal BC (based on OSL and AMS dates). The contradictions that existed between the individual dates can be explained either by the reservoir effect (for food crust dating) or by the correlation of the dating from different sections, where layers were not deposited at the same time. It is complicated to determine the rate of deposition of Early Neolithic cultural strata, which may have occurred in a single season or possibly over a longer period of time. The series of dates obtained indicate successive occupation of the site. The change in the pattern of coastal inhabitation from small-scale households’ areas with shell paved platforms and pits to dwelling complexes with clay pavement floors and clay-covered walls/roofs occurred over a very short time. This may explain the homogenous nature of the Early Neolithic material culture and the production of a certain set of clay vessels, stone, bone industry, and shell tools.

Surface Plasmon Coupling Electrochemiluminescence Immunosensor Based on Polymer Dots and AuNPs for Ultrasensitive Detection of Pancreatic Cancer Exosomes.

Polymer dots (Pdots) have become attractive electrochemiluminescence (ECL) luminophores due to their facile synthesis, easy modification, and stable electrochemical and optical properties. However, their ECL efficiency is not high enough for practical applications. In this work, we proposed an ECL immunosensor based on localized surface plasmon resonance (LSPR) between AuNPs and Pdots for the determination of pancreatic cancer exosomes. Based on the finite-difference time-domain simulations and the band energy of Pdots and AuNPs, we proposed the possible LSPR mechanism. The hot electrons of plasmonic AuNPs were photoexcited to surface plasmon states by ECL emission of Pdots, and then the excited hot electrons were transferred to the conduction band of Pdots, which significantly improved the ECL efficiency of Pdots. The ECL immunosensor displayed a wide calibration range of 1.0 × 103 to 1.0 × 106 particles/mL with a detection limit of 400 particles/mL. Cancer-related protein profiling revealed high selectivity toward different expressions of exosomal surface proteins from PANC-01, HeLa, MCF-7, and HPDE6-C7 cell lines. The proposed ECL system exhibits a promising prospect for protein biomarker profiling and early cancer-related diagnosis.

Wide Range Calibration Method for Direct Interface Circuits and Application to Resistive Force Sensors

A novel approach to interface resistive sensors directly to a Field Programmable Gate Array (FPGA) is presented in this paper. The circuit is based on Direct Interface Circuits (DICs), which make the sensor reading through a magnitude-to-time-to-digital conversion using just a few passive elements and a programmable digital device. Specifically, the system uses two calibration resistors of known value, two capacitors, and a new equation to estimate the sensor resistance in order to obtain an improved estimation in both the high and low parts of the resistance range. Furthermore, the new method can be used for reading resistive force sensors, with the advantage that the equations can be adapted for the output to directly provide the force exerted, thus avoiding the need for a resistance-to-force conversion. The circuit has been implemented using an FPGA as the programmable digital device to characterize the system, which allows both the reading of discrete resistors and those of a commercial force sensor. When discrete resistors are measured, estimation error in the low part of the range (a few hundred ohms) is reduced between twofold and fivefold compared to the results provided by other DICs. Moreover, the most significant errors produced by the new method when reading a force sensor come in the high part of the range (several tens of Newtons), standing at just 0.88%, compared to errors between 1.94% and 5.23% of other methods proposed in the literature.

Determination of BTEX Compounds in Contaminated Water Using the Novel Vacuum-Assisted-Total Vaporization SPME Method and GO-APTES Fiber.

A novel and reliable microextraction technique was used for the fast determination of benzene, toluene, ethylbenzene and xylenes (BTEX) from contaminated water without any extra steps for the preparation or extraction of the aqueous sample. Vacuum-assisted-total vaporization-solid-phase microextraction (SPME) eliminated one of the partitioning steps in conventional headspace SPME and caused an increase in the sensitivity and speed of the method. A home-made graphene oxide/3-aminopropyl-triethoxysilane nanocomposite SPME fiber was synthesized and used as the extraction phase for efficient extraction. Several crucial parameters were optimized, such as the vaporization time and temperature, extraction time and desorption conditions. At the optimum experimental conditions, a linear wide range calibration curve over a wide range of 1-5,000ngmL-1 and a relative standard deviation (n = 6) of 6.6-7.3% were obtained. The result of the determination of BTEX as a human health risk from real samples, using the proposed method, revealed an acceptable agreement with a valid method.

Development and Validation CFIA / MZ System as a Green Method for Determination of Thiol Drug (D-PEN)

A simple, automated and sensitive continues flow-injection analysis/merging zones technique (CFIA/MZ) method was developed for the determination of D-Penicillamine (thiol drug) in pure, pharmaceutical formulations and biological sample. This method involved the reaction of 1,2-Naphthoquinone-4-Sulphonic acid Sodium Salt (NQS) with D-Penicillamine to produce a brawn-colored complex which has maximum absorbance at 463nm. The method was cheap, economic, precise and accurate where the limit of detection was 6.3 µg.mL-1 and the RSD% was 0.34 and Recovery was 99.31%. Various chemical and physical conditions that affected the reaction have been studied. A wide calibration curve was rectilinear within the concentration range (15-1000) μg.mL-1 with a sample through put of 103 sample.hour-1. The proposed procedure was applied successfully for the estimation of PEN in pharmaceutics and biological sample and the results obtained were favorably compared with those given by a reference method of United States Pharmacopoeia (USP), and there was no significant difference between the obtained results, regarding accuracy and precision at the 95% confidence level.

Investigation of the impact of grapefruit juice, pomegranate juice and tomato juice on pharmacokinetics of brexpiprazole in rats using UHPLC-QTOF-MS.

Brexpiprazole (BRX) is approved for the treatment of schizophrenia and major depressive disorders and it is mainly metabolized by CYP3A4 and CYP2D6. Grapefruit juice (GFJ), pomegranate juice (PJ) and tomato juice (TJ) have the potential to inhibit CYP3A4 enzymes in the body. However, fruit juice-drug interactions between BRX and GFJ, PJ and TJ have not been studied extensively. The present study describes the influence of GFJ, PJ and TJ on the pharmacokinetic parameters of BRX in rats. The study samples were analyzed using a mass-accurate and single-step bioanalytical method by ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry over a wide calibration range of 20-1,500 ng/ml. The results of the pharmacokinetic study denoted that the combined administration of GFJ and PJ could increase systemic exposure of BRX. The area under the curve of BRX increased 3.43- and 1.88-fold with co-administration of GFJ and PJ, respectively, while TJ with BRX had no effect on the area under the curve. Time to peak concentration and half-life were not significantly changed by any juice co-administration. The results show that GFJ and PJ affect the pharmacokinetic profile of BRX and hence advice needs to be given to patients.

HPLC-DAD-CAD-based approach for the simultaneous analysis of hydrophobic drugs and lipid compounds in liposomes and for cyclodextrin/drug inclusion complexes

In recent decades liposomes have become attractive carriers for hydrophobic drugs to enhance their solubility and improve their therapeutic application. For liposomal drug products, both drug and lipid quantification are required by regulatory authorities, making the implementation of precise quantification methods a step of crucial importance in formulation development and quality control. Therefore, the present study is focused on the development and validation of a simple and time-saving method for the simultaneous analysis of hydrophobic drugs and conventional liposomal components. The new HPLC method was established with a combined detection by a diode array detector (DAD) and a corona charged aerosol detector (CAD). As a wide calibration range of the liposomal components can be achieved (10−1000 μg/mL), the analysis of samples with different drug to lipid ratios is enabled. Moreover, an excellent precision including repeatability and low limits of detection (≤ 1.8 μg/mL) and limits of quantification (≤ 5.9 μg/mL) were accomplished for all analytes. The method was successfully applied to liposomes incorporating mitotane. Everolimus was additionally analyzed as hydrophobic model drug. Furthermore, cyclodextrin/mitotane inclusion complexes were investigated to proof a broad range of applications for the developed method.

Surfactant-coupled titanium dioxide coated iron-aluminium mixed metal hydroxide for magnetic solid phase extraction of bisphenols in carbonated beverages

In this work, the magnetic sorbents based on different surfactant-coupled titanium dioxide coated iron-aluminium mixed metal hydroxide were investigated as sorbent for extraction of bisphenol compounds. The structure, morphology, and magnetic property of the synthesized sorbents were investigated. The cetyltrimethylammonium bromide-titanium dioxide coated iron-aluminium mixed metal hydroxide (Fe–Al MMH@TiO2-CTAB) exhibited excellent extraction performance toward bisphenols and was selected as the sorbent for development of magnetic solid phase extraction (MSPE) method. The entire MSPE process was optimized, and the extract was analyzed by high performance liquid chromatography with photodiode array detector. The method provided wide linear calibration ranges for bisphenols between 0.3–6000 μg L−1 with maximum enrichment factors of 280. The limits of detection and limits of quantification were in the ranges of 0.08–0.3 and 0.3–1.0 μg L−1, respectively. The proposed MSPE method was tested for determination of bisphenols in carbonated beverages. The studied carbonated beverages were mostly free of bisphenol contamination; however, BPS, BPA and BPB were detected in samples taken from defective cans. The relative recoveries ranging of 80.2–118.9% were obtained. The as-prepared Fe–Al MMH@TiO2-CTAB sorbent provided high sorption capacities in the range of 2215–2451 mg kg−1 and could be a promising material for bisphenols in beverage samples.

Sensitive, wide-range and high-throughput quantification of cyclosporine in whole blood using ultra-performance liquid chromatography coupled to tandem mass spectrometry and comparison with an antibody-conjugated magnetic immunoassay.

Because either trough or peak concentration at 2 h after administration is measured in routine therapeutic drug monitoring for cyclosporine A (CyA), a quantification method with a wide-range calibration curve capable of simultaneously measuring both concentrations is required. We developed a sensitive, wide-range and high-throughput quantification method for CyA in whole blood using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), and compared patients' blood CyA levels measured by UPLC-MS/MS and antibody-conjugated magnetic immunoassay (ACMIA). Whole blood samples were prepared by solid-phase extraction using Oasis HLB μElution plate. The UPLC-MS/MS assay showed excellent linearity over a wide calibration range of 5-2500 ng/mL. Within-batch accuracy and precision as well as batch-to-batch accuracy and precision fulfilled the criteria of US Food and Drug Administration guidelines. The blood CyA concentrations measured by the UPLC-MS/MS assay correlated strongly with those measured by ACMIA. A Bland-Altman plot showed a fixed error between CyA concentrations measured by the two methods, and the concentrations measured by the UPLC-MS/MS method were consistently lower than those measured by ACMIA. We have succeeded to develop a sensitive, wide-range and high-throughput quantification method for CyA in whole blood using UPLC-MS/MS.

A Label-free Electrochemical Immunosensor for Highly Sensitive Detection of TNF α, Based on Star Polymer-modified disposable ITO Electrode

Background: Biomarkers are very important disease-related biomolecules which should be analyzed sensitive and selective in related physiological fluids or tissues. Tumor necrosis factor-α is a type of cytokine which plays vitlly important roles in different methabolic pathways such as cell death, survival, differentiation, proliferation and migration, and infectious and inflammatory diseases including rheumatoid arthritis, diabetes. Objective: In this study, it was aimed to develop a reliable tool based on star-shaped poly(glycidyl methacrylate) polymer coated disposable indium tin oxide electrode for determination of Tumor necrosis factor-α, an important disease biomarker. Methods: Star shaped polymer was used as an interface material for anti- Tumor necrosis factor α antibodies immobilization. The antibodies were immobilized covalently onto polymer coated indium tin oxide electrode. Electrochemical impedance spectroscopy and cyclic voltammetry techniques were used for all electrochemical measurements. Results: The suggested immunosensor exhibited a linear range between 0.02 and 4 pg/mL Tumor necrosis factor-α, and the detection limit was found as 6 fg/mL. Scanning electron microscopy and atomic force microscopy were used for electrode surface characterization. In addition, the suggested immunosensor was used for Tumor necrosis factor-α sensing in human serum samples. The results displayed recoveries between 97.07 and 100.19%. Moreover, this immunosensor had a simple fabrication procedure and a long storage-stability. Conclusion: A new biosensor based on a Star shaped polymer for the ultra sensitive determination of a biomarker Tumor necrosis factor-α was developed. The biosensor presented excellent repeatability and reproducubility, and also wide calibration range for Tumor necrosis factor- α.

Trace-Level Determination of Acrylonitrile Generated in the Manufacturing Process of Oligonucleotides by Static Headspace Gas Chromatography with an Electron Impact(+) Mass Detector

A static headspace capillary gas chromatography (HS-GC) method featured with a short run time, a wide calibration range, and a diluent with strong buffering and stabilizing capability has been deve...

In situ adsorbent formation based dispersive micro-solid phase extraction using a deep eutectic solvent as an elution solvent for the extraction of some pesticides from honey samples prior to GC-MS analysis

In this work, a simple, inexpensive, green, and fast dispersive micro-solid phase extraction method has been developed for the extraction of several pesticides from honey samples. In this approach, a solution of curcumin was prepared in ethanol and it was dispersed into a sample solution with the aid of a syringe. Curcumin was precipitated in the sample solution as tiny particles and the analytes were adsorbed onto them. After centrifugation the adsorbed analytes were eluted with tetrabutylammonium chloride:dichloroacetic acid deep eutectic solvent. The dissolved analytes in the deep eutectic solvent were analyzed by gas chromatography-mass spectrometry. Parameters affecting the extraction efficiency of the method including sorbent amount, dispersive solvent type and volume, elution solvent type and volume, salting out effect, and sonication time were investigated. Extraction recovery of the method was obtained in the range of 70-83%. Also wide calibration ranges and low detection limits (0.22-0.81 ng g-1) were obtained. Relative standard deviation values for intra- and inter-day precisions were ≤10.2% for all analytes at a concentration of 5 ng g-1 of each (n = 6). Finally, ten honey samples were analyzed and data showed that all of the studied samples were free of the analytes.

Label-Free Detection of Staphylococcus aureus Based on Bacteria-Imprinted Polymer and Turn-on Fluorescence Probes.

The effective identification and quantitative determination of Staphylococcus aureus is a major public health concern. Here, an innovative strategy that combines a bacteria-imprinted polydimethylsiloxane film for bacterial recognition and fluorescence resonance energy transfer platform for turn-on fluorescence sensing is demonstrated. The bacteria-imprinted polydimethylsiloxane film was facilely fabricated to generate corresponding specific sites on the polydimethylsiloxane surface via stamp imprinting using Staphylococcus aureus as template followed by modification with 1H,1H,2H,2H-perfluorooctyltriethoxysilane. The fluorescence resonance energy transfer platform was developed through electrostatic interaction between citrate-functional copper clusters and dopamine-stabilized gold nanoparticles. When the Staphylococcus aureus are present, the 1H,1H,2H,2H-perfluorooctyltriethoxysilane-modified bacteria-imprinted polydimethylsiloxane film can precisely capture the target; subsequently, the negatively charged bacteria compete with citrate-functional copper clusters and bind to dopamine-stabilized gold nanoparticles, leading to the fluorescence recovery of citrate-functional copper clusters. The entire detection process was achieved within 135 min, showing a wide linear calibration response from 10 to 1 × 107 cfu mL-1 with a low detection limit of 11.12 cfu mL-1. Furthermore, the recoveries from spiked samples were from 97.7 to 101.90% with relative standard derivations lower than 10%. The established label-free assay of measuring Staphylococcus aureus is rapid, sensitive, specific, and efficient.

Low-volume LC-MS/MS method for the pharmacokinetic investigation of carvedilol, enalapril and their metabolites in whole blood and plasma: Application to a paediatric clinical trial.

Evidence-based pharmacotherapy with carvedilol and enalapril in children suffering from heart failure is insufficient owing to limited pharmacokinetic data. Although a few data sets regarding enalapril, its metabolite enalaprilat and carvedilol in children have been published, pharmacokinetic data on carvedilol metabolites are missing. However, for both drug substances, their active metabolites contribute substantially to drug efficacy. As data can hardly be derived from adults owing to the unknown impacts of enzymatic maturation and ontogeny during childhood, customised assays are important to facilitate paediatric evidence-based pharmacotherapy. Considering ethical paediatric constraints, a low-volume liquid chromatography coupled to mass spectrometry (LC-MS/MS) assay was developed using whole blood or plasma for the quantification of enalapril, enalaprilat, carvedilol, O-desmethyl carvedilol, 4- and 5-hydroxyphenyl carvedilol as well as 3- and 8-hydroxy carvedilol. To facilitate broader applications in adults, the elderly and children, a wide calibration range-between 0.024/0.049 and 50.000 ng/ml-was achieved with good linearity (r ≥ 0.995 for all analytes). In compliance with international bioanalytical guidelines, accuracy, precision, sensitivity and internal standard normalised matrix effects were further successfully validated with the exception of those for 3-hydroxy carvedilol, which was therefore assessed semi-quantitatively. Distinct haematocrits did not impact matrix effects or recoveries when analysing whole blood. Blood-to-plasma ratios were determined for all analytes to form the basis for pharmacokinetic modelling. Finally, incurred sample reanalysis of paediatric samples confirmed the reproducibility of the developed low-volume LC-MS/MS method during study sample analysis. The assay facilitates the reliable generation of important data and contributes towards a safe drug therapy in children.