Simple and reliable serotonin assay in human serum by LC-MS/MS method coupled with one step protein precipitation for clinical testing in patients with carcinoid tumors

Melt-blown polypropylene nonwoven as an efficient and eco-economic sorbent for pipette tip micro-solid phase extraction for the determination of tyrosine kinase inhibitors

BACKGROUND

The detection of tyrosine kinase inhibitors (TKIs) in biological fluids is essential due to their critical role in cancer therapy and the variability in individual drug metabolism, which necessitates precise dosing. Traditional methods for analyzing TKIs in biological fluids, such as blood plasma, typically involve complex sample preparation techniques that can be resource-intensive, environmentally burdensome, and not sufficiently sensitive for low-concentration analytes. There is a pressing need for more efficient, economical, and environmentally friendly methods that can enhance sensitivity and throughput without compromising accuracy.

RESULTS

This study explores the use of melt-blown polypropylene nonwoven (MBPP), commonly found in face masks, as a novel sorbent for pipette-tip micro-solid phase extraction (PT-μSPE). MBPP demonstrated excellent hydrophobicity and significant mesoporous adsorption capacity. An extraction device was fashioned by inserting a segment of MBPP (15 mg) into a 200 μL disposable plastic pipette tip, which was then attached to a 2.5 mL disposable plastic syringe. The MBPP's fabric form removes the need for a frit, allowing the extraction process to be completed in just 3 min through simple plunger manipulation. The method achieved extraction recoveries ranging from 60.5 % to nearly 100 %. Subsequent method validation using liquid chromatography-tandem mass spectrometry (LC-MS/MS) showed satisfactory linearity (coefficient of determination R2 > 0.993), accuracy (relative recoveries: 86.3%-114.8 %), and precision (relative standard deviation: 3.4%-11.3 %), with detection limits between 0.022 and 0.135 ng mL-1.

SIGNIFICANCE

The introduction of MBPP for PT-μSPE represents a significant advancement in the bioanalytical detection of TKIs, offering a highly efficient, cost-effective, and environmentally sustainable method. It compares favorably with existing techniques, offering advantages in terms of cost, environmental impact, and ease of use. This approach has the potential to be widely adopted for routine monitoring of TKIs in clinical settings.

Sialic Acid-Functionalized Gold Nanoparticles for Sensitive and Selective Colorimetric Determination of Serotonin

We present a novel colorimetric method inspired by nature's complex mechanisms, capable of selectively determining serotonin with high sensitivity. This method exploits the inherent binding affinity of serotonin with sialic acid (SA) molecules anchored to gold nanoparticles (SA-AuNPs). Upon serotonin binding, SA-AuNPs aggregate, and a characteristic red shift in the absorbance of SA-AuNPs accompanied by a dramatic color change (red to blue) occurs, readily observable even without instrumentation. The proposed method effectively eliminates interventions from potential interfering species such as dopamine, epinephrine, l-tyrosine, glucosamine, galactose, mannose, and oxalic acid. The absence of a color change with l-tryptophan, a structurally related precursor of serotonin, further confirms the high selectivity of this approach for serotonin detection. The colorimetric method has a wide linear dynamic range (0.05-1.0 μM), low limit of detection (0.02 μM), and fast response time (5 min). The limit of detection of the method is lower than other colorimetric serotonin sensors reported so far. The possible use of the proposed method in biological sample analysis was evaluated by employing a serotonin recovery assay in processed human plasma. The recoveries ranged from 90.5 to 104.2%, showing promising potential for clinical applications.

Fluorescent-Based Neurotransmitter Sensors: Present and Future Perspectives

Neurotransmitters (NTs) are endogenous low-molecular-weight chemical compounds that transmit synaptic signals in the central nervous system. These NTs play a crucial role in facilitating signal communication, motor control, and processes related to memory and learning. Abnormalities in the levels of NTs lead to chronic mental health disorders and heart diseases. Therefore, detecting imbalances in the levels of NTs is important for diagnosing early stages of diseases associated with NTs. Sensing technologies detect NTs rapidly, specifically, and selectively, overcoming the limitations of conventional diagnostic methods. In this review, we focus on the fluorescence-based biosensors that use nanomaterials such as metal clusters, carbon dots, and quantum dots. Additionally, we review biomaterial-based, including aptamer- and enzyme-based, and genetically encoded biosensors. Furthermore, we elaborate on the fluorescence mechanisms, including fluorescence resonance energy transfer, photon-induced electron transfer, intramolecular charge transfer, and excited-state intramolecular proton transfer, in the context of their applications for the detection of NTs. We also discuss the significance of NTs in human physiological functions, address the current challenges in designing fluorescence-based biosensors for the detection of NTs, and explore their future development.

Pd nanoparticles decorated ultrathin 2D metal-organic framework nanosheets with enhanced peroxidase-mimic activity and colorimetric assay of glucose

In addition to size, shape and morphology, enzyme-mimetic property could be efficiently regulated by controlling composition, forming complexes or hybrids, and surface modification. Herein, Pd nanoparticles with an average diameter of 2.52 nm were decorated on ultrathin 2D copper(ii)-porphyrin derived metal-organic framework (MOF) nanosheets by a simple reduction method for catalytic activity regulation. In comparison with other nanozymes, the as-synthesized Pd modified 2D MOF hybrid nanosheets (Pd@Cu-TCPP(Fe)) presented excellent peroxidase-mimic activity, exhibiting an even superior catalytic ability towards H2O2 with a Michaelis-Menten constant as low as 2.33 mM. Based on a cascade reaction between glucose oxidase and Pd@Cu-TCPP(Fe), a colorimetric method for the detection of glucose was established and validated with a wide linear range (0.2-8.0 mM), good recovery (89.5-94.2%) and nice reproducibility (3.65%). All these features guaranteed its excellent ability for glucose determination in human cerebrospinal fluids. This study could offer a valuable reference for constructing novel optical biosensors.

Simultaneous Determination of Metabolites Related to Arginine Metabolism in Rat plasma by Hydrophilic Interaction Chromatography-Tandem Mass Spectrometry

Arginine and its metabolites play important roles in pain and analgesia. This study aimed to develop a comprehensive quantification method for amino acids and metabolites related to arginine metabolism in rat plasma by hydrophilic interaction chromatography-tandem mass spectrometry (HILIC-MS/MS). Rat plasma was diluted to reduce the matrix effect and deproteinized with acetonitrile. The analytes were separated on a Syncronis HILIC column with a gradient elution. MS analysis was performed in positive ion mode with an electrospray ionization source using multiple reaction monitoring technology. All calibration curves for the 10 analytes showed good linear regression (R2 > 0.99). The limits of detection (LODs) were in the range of 0.9-13.4 μg/L. The established method was validated for intra-day and inter-day precisions (relative standard deviation [RSDs] < 6.21%) and accuracy (average recovery ranged from 87.34% to 100.35% with the RSD values less than 11.41%). This method was successfully applied to characterize dynamic alterations in the plasma of rats with neuropathic pain and thus provide service to explore the mechanism of action between metabolite changes and clinical disease.

New quantification method for monitoring eighteen L-amino acids levels in schizophrenic patients by high-performance liquid chromatography coupled to tandem quadrupole mass spectrometer

A fast, uncomplicated, sensitive, and fully validated high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method has been developed for estimating L-amino acids in the plasma of schizophrenic patients. The gradient-elution chromatographic method was implemented with the Luna® PFP column (50 × 2.0 mm, 5-μm), and a mobile phase of 0.1% formic acid in water and methanol was used. The intraday and interday variability of the L-amino acids were less than 13.11%, and their accuracy ranged from 85.14 - 116.75% at the quality control levels and the lower limit of quantification (LLOQ) ranged from 2.5 - 15 nM. The extraction efficiency (apparent recovery) of amino acids from healthy plasma was employed by spiking the plasma with standard amino acids at the quality control levels. Their percentage recoveries ranged from 80.4% to 119.94%. Our method has a short run time and fast sample preparation compared with existing methods, which are suffered from long preparative steps and/or time-consuming analysis, restricted reagents, and suboptimal performance characteristics presently available technologies. Therefore, the proposed HPLC-MS/MS method was effectively applied for monitoring the L-amino acids in the plasma of schizophrenic patients and healthy volunteers.

A simple and reliable bile acid assay in human serum by LC-MS/MS

Background

Bile acids, as important signaling molecules and regulatory factors acting on glucose, lipid, and energy metabolism, are always involved in liver, biliary, and intestinal diseases. Development and validation of a simple liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method for determination of bile acids is significant for the routine clinical testing.

Methods

Fifty microlitre of serum was mixed with 10 μl of the internal standard working solution and then 140 μl of methanol for protein precipitation. After centrifuged, the supernatant was directly used for LC‐MS/MS analysis.

Results

Good separation of all bile acid species was achieved. The method was validated with consistent linearity for individual bile acids, good recovery, low carryover, satisfactory sample stability, and analytical specificity against hemolysis, lipemia, and bilirubinemia. The intra‐day and the inter‐day imprecision values were in the range of 1.53%–10.63% and 3.01%–13.98%, respectively. No obvious matrix effect was observed. The reference intervals of bile acids in adults have been established for the clinical testing.

Conclusions

The low sample volume, simple sample preparation, good separation of all species, and satisfying validation results make this LC‐MS/MS approach suitable for usage as a high‐throughput assay in routine clinical laboratories.

Development of a simple and reliable method for α-amanitin detection in rat plasma and its application to a toxicokinetic study

RATIONALE

α-Amanitin is a highly toxic peptide widely found in species of poisonous mushrooms. The matrix effect has been a major obstacle for accurate determination of α-amanitin in plasma samples by liquid chromatography/tandem mass spectrometry (LC/MS/MS). In this study, the strategy to eliminate the matrix effect of α-amanitin with a one-step dilution approach after deproteinization was applied.

METHODS

Rat plasma samples were processed by protein precipitation with methanol followed by a nine-fold dilution with pure water. The matrix effect value of α-amanitin was 19.7%-22.2% by protein precipitation and then changed to 87.5%-88.7% after dilution. α-Amanitin and the internal standard (roxithromycin) were analyzed on an ACQUITY UPLC® BEH C18 (50 mm × 2.1 mm, 1.7 μm) column within 3.0 min by gradient elution.

RESULTS

The linear ranges were 0.90-600 ng/mL with a correlation coefficient r >0.9958. A lower limit of quantification (LLOQ) of 0.90 ng/mL was achieved using only 50 μL of rat plasma. The intra- and inter-day precisions for the analyte ranged from 3.2% to 7.5% and 3.1% to 7.1%, respectively, and the accuracy ranged from -5.3% to -8.0%.

CONCLUSIONS

The matrix effect of α-amanitin was reduced by sample dilution after plasma deproteinization. A reliable LC/MS/MS method for the determination of α-amanitin in rat plasma was developed. This method was successfully applied for a toxicokinetic study of rats after intravenous injection of α-amanitin with a subacute toxicity dose at 0.10 mg/kg.

Simultaneous LC-MS/MS bioanalysis of alkaloids, terpenoids, and flavonoids in rat plasma through salting-out-assisted liquid-liquid extraction after oral administration of extract from Tetradium ruticarpum and Glycyrrhiza uralensis: a sample preparation strategy to broaden analyte coverage of herbal medicines

Herbal medicines have historically been practiced in combinatorial way, which achieves therapeutic efficacy by integrative effects of multi-components. Thus, the accurate and precise measurement of multi bioactive components in matrices is inalienable to understanding the metabolism and disposition of herbal medicines. In this study, aiming to provide a strategy that improves analyte coverage, evaluation of six protocols employing sample pretreatment methods- protein precipitation (PPT), liquid-liquid extraction (LLE), sugaring-out-assisted liquid-liquid extraction (SULLE), and salting-out-assisted liquid-liquid extraction (SALLE)- was performed by LC-MS/MS using rat plasma and a mixture of alkaloid (evodiamine, rutaecarpine, dehydroevodiamine), terpenoid (limonin, rutaevin, obacunone), and flavonoid (liquiritin, isoliquiritin, liquiritigenin) standards isolated from Tetradium ruticarpum and Glycyrrhiza uralensis. These protocols were as follows: (1) PPT with methanol, (2) PPT with acetonitrile, (3) LLE with methyl tertiary-butyl ether-dichloromethane, (4) LLE with ethyl acetate-n-butanol, (5) SALLE with ammonium acetate, (6) SULLE with glucose. The results suggested that SALLE produced broader analyte coverage with satisfactory reproducibility, acceptable recovery, and low matrix interference. Then, sample preparation procedure of SALLE, chromatographic conditions, and mass spectrometric parameters were optimized, followed by method validation, showing that good sensitivity (LLOQ ≤ 1 ng mL^-1), linearity (r ≥ 0.9933), precision (RSD ≤ 14.45%), accuracy (89.54~110.87%), and stability could be achieved. Next, the developed method was applied successfully to determine the pharmacokinetic behavior of the nine compounds in rat plasma after intragastric administration with an extract from Tetradium ruticarpum and Glycyrrhiza uralensis (Wuzhuyu-Gancao pair). Based on an extensive review and experiments, a sample preparation procedure that matches with LC-MS/MS technique and can get wider analyte coverage was outlined. The developed SALLE method is rapid, reliable, and suitable for bioanalysis of analytes with diverse polarity, which was expected to be a promising strategy for the pharmacokinetic studies of herbal medicines. Graphical abstract.