Quantification of Free Sialic Acid in Human Plasma through a Robust Quinoxalinone Derivatization and LC–MS/MS Using Isotope-labeled Standard Calibration

We report an accurate quantification of free sialic acid (SA) in human plasma using LC–MS/MS method with isotope-labeled standard calibration (ILSC) and robust derivatization. Specifically, derivatization of SA with a stable and inexpensive 3,4-diaminotoluene (DAT) provides a stable product of SA with high MS response, proving a convenient and cost-effective LC–MS/MS analysis of free SA. In addition, the use of 13C3-SA as calibration standard ensured the accuracy for the measurement. This assay used ultra high performance liquid chromatography (UHPLC) for separation of native/labeled SA and IS from matrix interference, and employed mass spectrometry in multiple reaction monitoring (MRM) mode for sensitive and selective detection. We have achieved a lower limit of quantification (LLOQ) of 20 ng/mL and a total running time of 4.2 min, which is the most sensitive and quick measurement for free SA in biomatrices

Quantification of Free Sialic Acid in Human Plasma through a Robust Quinoxalinone Derivatization and LC–MS/MS Using Isotope-labeled Standard Calibration

We report an accurate quantification of free sialic acid (SA) in human plasma using LC–MS/MS method with isotope-labeled standard calibration (ILSC) and robust derivatization. Specifically, derivatization of SA with a stable and inexpensive 3,4-diaminotoluene (DAT) provides a stable product of SA with high MS response, proving a convenient and cost-effective LC–MS/MS analysis of free SA. In addition, the use of 13C3-SA as calibration standard ensured the accuracy for the measurement. This assay used ultra high performance liquid chromatography (UHPLC) for separation of native/labeled SA and IS from matrix interference, and employed mass spectrometry in multiple reaction monitoring (MRM) mode for sensitive and selective detection. We have achieved a lower limit of quantification (LLOQ) of 20 ng/mL and a total running time of 4.2 min, which is the most sensitive and quick measurement for free SA in biomatrices

Development and validation of a deep learning-based model to distinguish acetabular fractures on pelvic anteroposterior radiographs

Objective: To develop and test a deep learning (DL) model to distinguish acetabular fractures (AFs) on pelvic anteroposterior radiographs (PARs) and compare its performance to that of clinicians.Materials and methods: A total of 1,120 patients from a big level-I trauma center were enrolled and allocated at a 3:1 ratio for the DL model’s development and internal test. Another 86 patients from two independent hospitals were collected for external validation. A DL model for identifying AFs was constructed based on DenseNet. AFs were classified into types A, B, and C according to the three-column classification theory. Ten clinicians were recruited for AF detection. A potential misdiagnosed case (PMC) was defined based on clinicians’ detection results. The detection performance of the clinicians and DL model were evaluated and compared. The detection performance of different subtypes using DL was assessed using the area under the receiver operating characteristic curve (AUC).Results: The means of 10 clinicians’ sensitivity, specificity, and accuracy to identify AFs were 0.750/0.735, 0.909/0.909, and 0.829/0.822, in the internal test/external validation set, respectively. The sensitivity, specificity, and accuracy of the DL detection model were 0.926/0.872, 0.978/0.988, and 0.952/0.930, respectively. The DL model identified type A fractures with an AUC of 0.963 [95% confidence interval (CI): 0.927–0.985]/0.950 (95% CI: 0.867–0.989); type B fractures with an AUC of 0.991 (95% CI: 0.967–0.999)/0.989 (95% CI: 0.930–1.000); and type C fractures with an AUC of 1.000 (95% CI: 0.975–1.000)/1.000 (95% CI: 0.897–1.000) in the test/validation set. The DL model correctly recognized 56.5% (26/46) of PMCs.Conclusion: A DL model for distinguishing AFs on PARs is feasible. In this study, the DL model achieved a diagnostic performance comparable to or even superior to that of clinicians

Measurement of gas composition using ultrasonic sensors

An improved experimental apparatus for measuring the speed of sound (SoS) of binary gas mixtures using a single acoustic sensor in an on-line mode is described in this thesis. The SoS sensor has a fixed acoustic path and is operated at a fixed frequency of 121362 Hz. A pair of piezoelectric transducers are used in the sensor as the ultrasound pulse transmitter and receiver, respectively. A single-pulse time of flight (ToF) based approach with a novel wave interpolation algorithm allowed the SoS to be resolved typically better than 1 part in 500,000 at one second measurement intervals. Suitability for precise rapid on-line measurement and simplicity are the two most important factors considered in the selection of SoS determination method. Real gas SoS is functionally dependent upon gas composition, temperature, pressure and acoustic frequency, which is the fundamental principle of the SoS technique for measuring the composition of binary gas mixtures. Pure reference gases including Ar, He and N2 were used in the experiment for analysing the SoS measurement uncertainty. For CO2/N2, the experimental CO2 mole fraction ranged from 0 to 0.3 and the uncertainty of the measured SoS results was estimated to be 0.1%. For any other tested binary gas mixture which consists of water vapour or an organic vapour, including n-hexane, n-heptane, n-octane, n-nonane, n-decane, toluene, cyclohexane, acetone, methyl ethyl ketone, ethyl acetate, methanol, ethanol, isopropanol, dichloromethane, chloroform, 1,2-dichloroethane, m-/o-/p-xylene, ethylbenzene, n-butylamine, limonene and α-pinene, as one component and dry air as the other, the mole fraction of the vapour component in the experiments was in the range from 0 to 95% of the saturated vapour mole fraction (0 to 95%SAT), and the SoS measurement uncertainty was estimated to be 0.14%. The experimental temperature range was from 5 to 55 °C, and each experiment was performed isothermally under atmospheric pressure. The temperature of the gas in the acoustic cavity of the SoS sensor can be measured with an uncertainty of 12.5 m°C by using the calibrated SoS sensor’s PT100. With the use of a barometric sensor mounted in the SoS sensor electronics board, a measurement of atmospheric pressure with 0.75 mbar uncertainty can be achieved. The carrier gas, N2 or dry air, was employed as the reference gas in each isothermal experiment for the calibration of the acoustic pathlength. The true gas composition of the binary gas mixtures was determined using a novel gas density measurement based on Archimedes’ Principle. The relationships between gas composition and density was established with an equation of state analysis using the Helmholtz equations stored in the NIST REFPROP software or the Van der Waals equation. Mixture density was measured with an uncertainty of 0.0015 kg/m3. A plot of measured SoS versus composition under different isothermal conditions is given for each investigated mixture. The deviation between the lossless real gas SoS determined using the NIST REFPROP software and the measured SoS was analysed for the mixtures with available thermodynamic data in the software including CO2/N2 and n-hexane, n-heptane, n-octane, n-nonane, n-decane, toluene, cyclohexane, water/dry air. Since CO2 is a strongly dispersive gas, the deviation for CO2/N2 is large and the maximum deviation reaches about 1.8%. For the other mixtures the deviation is below 0.5% and is reasonably small. By correlating the measured composition with SoS and temperature, SoS measurements allow rapid and real time gas composition determinations. Under atmospheric pressure and within the respective experimental composition ranges, for example for CO2/N2 at temperatures from 10 to 50 °C, SoS based technique is able to give compositions with an uncertainty of 0.0006 in mole fraction; for n-heptane/dry air mixtures at temperatures from 25 to 55 °C the uncertainty is between 0.16 and 0.40%SAT. This thesis also reports the most complete set of SoS data for organic vapour/dry air mixtures yet reported, including twenty-three different organic solvents across a range of temperatures, typically 5 to 55 °C. This study confirmed the versatility of SoS (ToF) ultrasonic measurements for the rapid and accurate composition measurement of binary gas mixtures for potential deployment in industrial or scientific instrumentation. Manufacture of the SoS sensor is practicable, and the difference in composition measurement uncertainty between a manufactured sensor and the prototype sensor used in this project should be negligible. In comparison with traditional gas composition measurement techniques, this technique is not only robust but also has the potential to be faster, simpler, more cost-effective, more precise and more accurate.Open Acces

Development and validation of a liquid chromatography-tandem mass spectrometry assay for serum 25-hydroxyvitamin D2/D3 using a turbulent flow online extraction technology

Background: Vitamin D is important to health and disease. Liquid chromatography-tandem mass spectrometry (LC-MSMS) is considered the most accurate technology for quantification of serum 25-hydroxyvitamin D (25OHD) which is the best biomarker for estimating vitamin D nutritional status. Methods: Serum was mixed with acetonitrile containing hexadeuterated 25-hydroxyvitamin D3 (d6-25OHD3) and centrifuged 10 min at 15,634×g. The supernatant was injected onto a turbulent flow preparatory column then transferred to a polar endcapped C18 analytical column. The mass spectrometer was set for positive atmospheric pressure chemical ionization. Results: The analytical cycle time was 5.5 min. Inter- and intra-assay CV for both analytes across three concentrations ranged from 3.8% to 14.2%. The method was linear from 3.0 to 283.6 nmol/L for 25-hydroxyvitamin D3 (25OHD3) and 4.6 to 277.9 nmol/L for 25-hydroxyvitamin D2 (25OHD2), with an accuracy of 88.7%–118.7% and 90.7%–100.3%, respectively. No carryover or ion suppression was observed. Comparison with a radioimmunoassay using patient specimens (n=527) showed a mean difference of 5.2%, and diagnostic agreement of 80.9% with Deming regression of slope 0.867, intercept 12.8, standard error of estimate (SEE) 17.4, and r=0.8425. Conclusions: The LC-MSMS method coupled with turbulent flow technology for serum 25OHD quantitation is rapid, efficient, and suitable for clinical testing. Clin Chem Lab Med 2009;47:1565–72.Peer Reviewe

Antibody drugs targeting SARS-CoV-2: Time for a rethink?

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) heavily burdens human health. Multiple neutralizing antibodies (nAbs) have been issued for emergency use or tested for treating infected patients in the clinic. However, SARS-CoV-2 variants of concern (VOC) carrying mutations reduce the effectiveness of nAbs by preventing neutralization. Uncoding the mutation profile and immune evasion mechanism of SARS-CoV-2 can improve the outcome of Ab-mediated therapies. In this review, we first outline the development status of anti-SARS-CoV-2 Ab drugs and provide an overview of SARS-CoV-2 variants and their prevalence. We next focus on the failure causes of anti-SARS-CoV-2 Ab drugs and rethink the design strategy for developing new Ab drugs against COVID-19. This review provides updated information for the development of therapeutic Ab drugs against SARS-CoV-2 variants