Determination of serum glucose by isotope dilution liquid chromatography-tandem mass spectrometry: a candidate reference measurement procedure

Advances in Chromatographic and Mass Spectrometric Techniques for Analyzing Reducing Monosaccharides and Their Phosphates in Biological Samples

Reducing monosaccharides and their phosphates are critical metabolites in the central carbon metabolism pathway of living organisms. Variations in their content can indicate abnormalities in metabolic pathways and the onset of certain diseases, necessitating their analysis and detection. Reducing monosaccharides and their phosphates exhibit significant variations in content within biological samples and are present in many isomers, which makes the accurate quantification of reducing monosaccharides and their phosphates in biological samples a challenging task. Various analytical methods such as spectroscopy, fluorescence detection, colorimetry, nuclear magnetic resonance spectroscopy, sensor-based techniques, chromatography, and mass spectrometry are employed to detect monosaccharides and phosphates. In comparison, chromatography and mass spectrometry are highly favored for their ability to simultaneously analyze multiple components and their high sensitivity and selectivity. This review thoroughly evaluates the current chromatographic and mass spectrometric methods used for detecting reducing monosaccharides and their phosphates from 2013 to 2023, highlighting their efficacy and the advancements in these analytical technologies.

Do We Need the Replacement of YSI 2300? A View from the Clinical Laboratory

In this issue of Journal of Diabetes Science and Technology, Baumstark et al. evaluated the analytical performance of a bench-top laboratory glucose analyzer (SUPER-GL) intended for replacement for the YSI2300-STAT analyzer, that served for several decades as a comparator method in clinical and analytical studies of blood glucose monitoring systems (BGMS). The authors concluded that the SUPER-GL's overall performance is comparable to that of YSI2300-STAT, and has the potential to be a candidate comparator analyzer. However, the question is if we need to recommend as a "comparator method," a specific device, that measure glucose using the same analytical method with most BGMS. In this analysis we present our point of view hoping to generate a discussion on the necessity for such a replacement.

Quantification of 2-NBDG, a probe for glucose uptake, in GLUT1 overexpression in HEK293T cells by LC-MS/MS

The growth and proliferation of most cancer cells involve the excessive uptake of glucose mediated by glucose transporters. An effective strategy for cancer therapy has been to inhibit the GLUTs that are usually overexpressed in a variety of tumor cells. 2-NBDG is a GLUT1 substrate that can be used as a probe for GLUT1 inhibitors. An accurate and simple assay for 2-NBDG in a HEK293T cell model overexpressing GLUT1 was developed using liquid chromatography-tandem mass spectrometry. Chromatographic separation was achieved using a Xbridge® Amide column (3.5 μm, 2.1 mm × 150 mm, Waters) with acetonitrile-water containing 2 μM ammonium acetate (80:20, v/v) at a flow rate of 0.25 mL/min. Mass detection was conducted in the parallel reaction monitoring (PRM) mode. The calibration curve for 2-NBDG showed good linearity in the concentration range of 5-500 ng/mL with satisfactory precision, a relative standard deviation ranging from 2.92 to 9.59% and accuracy with a relative error ranging from -13.14 to 7.34%. This method was successfully applied to quantify the uptake of GLUT1-mediated 2-NBDG, and the results clearly indicated inhibition of GLUT1 by WZB117 and quercetin (two potent glucose transporter inhibitors) in the GLUT1-HEK293T cell model. This study provides a convenient and accurate method for high-throughput screening of selective and promising GLUT1 inhibitors.

Candidate reference measurement procedure based on HPAEC-PAD for the development of certified reference materials for monosaccharides in serum

To achieve the measurement reliability of monosaccharides used as diagnostic markers in clinical fields, it is essential to establish certified reference materials (CRMs). The purpose of this study is to develop a serum CRM by adopting high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) as a new candidate reference measurement procedure for the measurement of glucose and galactose, common diagnostic markers of diabetes and galactosemia, respectively. Using various monosaccharides as internal standards, the accuracy of the HPAEC-PAD method was tested by measuring glucose CRM following treatment with three different deproteinization methods: ultrafiltration, protein precipitation by trichloroacetic acid (TCA), and protein precipitation by acetonitrile. Results showed that ultrafiltration and 5% TCA provided good accuracy with every tested monosaccharide as the internal standard. Accordingly, serum samples in this study were treated by ultrafiltration after adding 2-deoxy-D-glucose and arabinose, which were selected as internal standards for galactose and glucose, respectively. Both intra- and inter-day recovery tests showed good precision and accuracy within 2%. From the serum CRM batches prepared at two levels, 11 units were analyzed by exact-matched calibration methods, and the mass fractions of galactose and glucose were determined via HPAEC-PAD. The between-unit relative standard deviations were not more than 1.5%, showing homogeneity. The expanded uncertainties (%) of galactose and glucose for both levels were less than 3.6% and 2.3% at 95% confidence. The HPAEC-PAD method presented in this study can significantly improve the accuracy and precision of simultaneous monosaccharide analysis, allowing for the development of further serum CRMs for monosaccharides. Graphical abstract.

Flexible enzyme cascade sensing platform based on a G-quadruplex nanofiber biohydrogel for target colorimetric sensing

Enzyme cascade reactions can greatly improve catalytic efficiency and achieve selective and sensitive detection of targets. This paper presents a novel strategy for colorimetric sensing of targets by loading natural enzymes into a hemin-doped G-quadruplex (G4-hemin) biohydrogel to form a flexible enzyme cascade sensing (FECS) platform. The biohydrogel has advantages of biocompatibility, printability and flexibility. The biohydrogel not only participates in the cascade reaction as the mimic enzyme but also provides a mild microenvironment for the natural enzyme. The FECS platform has a linear range from 0.4 μM to 120 μM and a detection limit of 3.6 × 10^-6 M for hydrogen peroxide detection. Additionally, the FECS platform has a low detection limit and wide linear range for glucose and xanthine by loading xanthine oxidase (XOD) and glucose oxidase (GOD) into the biohydrogel, respectively. These results indicate that the novel FECS platform is an effective detection platform that can detect multiple targets and is expected to be widely used in flexible sensing.

Measurement of serum 17-hydroxyprogesterone using isotope dilution liquid chromatography-tandem mass spectrometry candidate reference method and evaluation of the performance for three routine methods

OBJECTIVES

Accurate measurements of serum 17-hydroxyprogesterone (17OHP) are essential for diagnosis and treatment monitoring for congenital adrenal hyperplasia patients. The performance of serum 17OHP routine methods remains highly variable that calls for a candidate reference measurement procedure (cRMP) to improve the standardization of serum 17OHP measurements.

METHODS

Serum samples spiked with internal standards were extracted with a combination of solid-phase extraction and liquid-liquid extraction. The 17OHP was quantified by the isotope dilution coupled with liquid chromatography/tandem mass spectrometry (ID-LC/MS/MS) with electrospray ionization in positive ion mode. Nine structural analogs of 17OHP were evaluated for interferences. The precision and analytical recovery were assessed. Twenty native and 40 spiked serum for performance evaluation were measured by the cRMP and two clinical LC/MS routine methods.

RESULTS

No apparent interferences were found with the 17OHP measurement. The within-run, between-run, and total precision for our method were 0.4-0.8%, 0.6-2.0%, and 1.0-2.1% for four pooled serum (2.46-102.72 nmol/L), respectively. The recoveries of added 17OHP were 100.0-100.2%. For the performance of two LC/MS routine methods, they showed relative deviation ranges of -22.1 to 1.1% and -6.7 to 12.8%, respectively.

CONCLUSIONS

We developed and validated a reliable serum 17OHP method using ID-LC/MS/MS. The desirable accuracy and precision of this method enable it to serve as a promising cRMP to improve the standardization for serum 17OHP routine measurements.

The Oral Glucose Tolerance Test-Is It Time for a Change?-A Literature Review with an Emphasis on Pregnancy

Globally, gestational diabetes (GDM) is increasing at an alarming rate. This increase is linked to the rise in obesity rates among women of reproductive age. GDM poses a major global health problem due to the related micro- and macro-vascular complications of subsequent Type 2 diabetes and the impact on the future health of generations through the long-term impact of GDM on both mothers and their infants. Therefore, correctly identifying subjects as having GDM is of utmost importance. The oral glucose tolerance test (OGTT) has been the mainstay for diagnosing gestational diabetes for decades. However, this test is deeply flawed. In this review, we explore a history of the OGTT, its reproducibility and the many factors that can impact its results with an emphasis on pregnancy.

Inductively Coupled Plasma Mass Spectrometry as a Reference Method to Evaluate Serum Calcium Measurement Bias and the Commutability of Processed Materials during Routine Measurements

Background:

Measuring total serum calcium is important for the diagnosis of diseases. Currently, results from commercial kits for calcium measurement are variable. Generally, the performance of serum calcium measurements is monitored by external quality assessment (EQA) or proficiency testing schemes. However, the commutability of the EQA samples and calibrators is often unknown, which limits the effectiveness of EQA schemes. The aim of this study was to evaluate the bias of serum calcium measurements and the commutability of processed materials.

Methods:

Inductively coupled plasma mass spectrometry was applied as a comparative method, and 14 routine methods were chosen as test methods. Forty-eight serum samples from individual patients and 25 processed materials were quantified. A scatter plot was generated from patient samples, and 95% prediction intervals were calculated to evaluate the commutability of the processed materials and measurement bias at three concentration levels was used to determine the accuracy of routine assays.

Results:

All assays showed high precision (total coefficient of variation [CV] <2.26%) and correlation coefficients (r > 0.99). For all assays, the mean bias for the 48 patient samples ranged from −0.13 mmol/L to 0.00 mmol/L (−5.61–0.01%), and the ranges for the three concentrations were −0.10–0.04 mmol/L (−5.71–2.35%), −0.14–−0.01 mmol/L (−5.80–−0.30%), and −0.19–0.04 mmol/L (−6.24–1.22%). The EQA samples, calibrators, and animal sera exhibited matrix effects in some assays; human serum pools were commutable in all assays; certificate reference materials were commutable in most assays, and only GBW09152 exhibited a matrix effect in one assay; and aqueous reference materials exhibited matrix effects in most assays.

Conclusions:

Biases for most assays were within the acceptable range, although the accuracy of some assays needs improvement. Human serum pools prepared from patient samples were commutable, and the other tested materials exhibited a matrix effect.

An adapted isotope dilution 1H-13C heteronuclear single-quantum correlation (ID-HSQC) for rapid and accurate quantification of endogenous and exogenous plasma glucose

A wide variety of methods, such as enzymatic methods, LC-MS, and LC-MS/MS, are currently available for the concentration determination of plasma glucose in studies of diabetes, obesity, exercise, etc. However, these methods rarely discriminate endogenous and exogenous glucose in plasma. A novel NMR strategy for discriminative quantification of the endogenous and exogenous glucose in plasma has been developed using an adapted isotope dilution ¹H-¹³C heteronuclear single-quantum correlation (ID-HSQC) with uniformly ¹³C-labeled glucose as a tracer of exogenous glucose. This method takes advantage of the distinct ¹H-¹³C chemical shifts of the hemiacetal group of the α-D-glucopyranose and makes use of the ¹³C-¹³C one-bond J-coupling (¹J_CC) in uniformly ¹³C-labeled glucose to differentiate the ¹H-¹³C HSQC signal of labeled glucose from that of its natural counterpart when data are acquired in high-resolution mode. The molar ratio between the endogenous and exogenous plasma glucose can then be calculated from the peak intensities of the natural and labeled glucose. The accuracy and precision of the method were evaluated using a series of standard mixtures of natural and uniformly ¹³C-labeled glucose with varied but known concentrations. Application of this method is demonstrated for the quantification of endogenous and exogenous glucose in plasma derived from healthy and diabetic cynomolgus monkeys. The results nicely agree with our previous LC-MS/MS results. Considering the natural abundance of ¹³C isotope at the level of 1.1% in endogenous glucose, comparable peak intensities of quantitatively measurable signals derived from natural and labeled glucose imply that the ID-HSQC can tolerate a significantly high ratio of isotope dilution, with labeled/natural glucose at ~ 1%. We expect that the ID-HSQC method can serve as an alternative approach to the biomedical or clinical studies of glucose metabolism.

Glucose Sensing Using Capacitive Biosensor Based on Polyvinylidene Fluoride Thin Film

A polyvinylidene fluoride (PVDF) film-based capacitive biosensor was developed for glucose sensing. This device consists of a PVDF film sandwiched between two electrodes. A capacitive biosensor measures the dielectric properties of the dielectric layers at the interface between the electrolyte and the electrode. A glucose oxidase (GOx) enzyme was immobilized onto the electrode to oxidize glucose. In practice, the biochemical reaction of glucose with the GOx enzyme generates free electron carriers. Consequently, the potential difference between the electrodes is increased, resulting in a measurable voltage output of the biosensor. The device was tested for various glucose concentrations in the range of 0.013 to 5.85 M, and various GOx enzyme concentrations between 4882.8 and 2.5 million units/L. We found that the sensor output increased with increasing glucose concentration up to 5.85 M. These results indicate that the PVDF film-based capacitive biosensors can be properly applied to glucose sensing and provide opportunities for the low-cost fabrication of glucose-based biosensors based on PVDF materials.

A novel analytical approach for the determination of parathion methyl in water: quadrupole isotope dilution mass spectrometry-dispersive liquid–liquid microextraction using multivariate optimization

Dispersive liquid–liquid microextraction was coupled with quadruple isotope dilution mass spectrometry for the sensitive and accurate determination of parathion methyl in water.