"Iridium Signature" Mass Spectrometric Probes: New Tools Integrated in a Liquid Chromatography-Mass Spectrometry Workflow for Routine Profiling of Nitric Oxide and Metabolic Fingerprints in Cells

Nitric oxide (NO) is a highly reactive signaling molecule involved in diverse biological processes. Simultaneous profiling of NO and associated metabolic fingerprints in a single assay allows more accurate assessments of cell states and offers the possibility to better understand its exact biological roles. Herein, a multiplexing LC-MS workflow was established for simultaneous detection of intracellular NO and various metabolites based on a novel "iridium signature" mass spectrometric probe (Ir-MSP841). This Ir-MSP841 can convert highly liable NO to a stable permanently charged triazole product (Ir-TP852), enabling direct MS detection of NO. This ^191/193Ir-signature mass spectrometric probe-based approach is endowed with overwhelming advantages of interference-free, high quantitative accuracy, and great sensitivity (limit of detection down to 0.14 nM). It also reveals good linearity over a wide concentration range 12.5-500 nM and has been successfully employed for exploring the release behaviors of three representative NO donors in cells. Meanwhile, metabolic profiling results reveal that varying the concentrations of NO has distinct effects on various cellular metabolites. This study provides a robust, sensitive, and versatile method for simultaneous detection of NO and numerous metabolites in a single LC-MS run and expands its applications in biomedical research.

Quantitative determination of nitric oxide from tissue samples using liquid chromatography-Mass spectrometry

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We report a method to measure NO by reacting it with carboxy-PTIO to form carboxy-PTI.

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The carboxy-PTI is quantified by liquid chromatography – mass spectrometry (LCMS).

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This method can quantitate NO concentrations ranging from 5 nM to 1 μM.

Ever since it was found to mediate the endothelium-dependent dilation of blood vessels, nitric oxide (NO) has generated enormous research interest throughout the biological sciences. Over thirty years of research has identified NO as a ubiquitous and versatile regulatory factor utilized by both vertebrates and invertebrates. The short lifetime and low concentration of NO make quantitation difficult. Here we report a method for measuring NO using the selective reaction with 2-​(4-​carboxyphenyl)-​4,​5-​dihydro-​4,​4,​5,​5-​tetramethyl-1H-​imidazolyl-​1-​oxy-​3-​oxide (carboxy-PTIO) to form carboxy-PTI. We used tandem mass spectrometry to verify the validity of this reaction, and liquid chromatography – mass spectrometry to quantitate the amount of carboxy-PTI formed. Using diethylamine nonoate as a NO donor we demonstrate this method can quantitate NO concentrations with a detection limit of 5 nM. We successfully determined the amount of NO generated endogenously by frog heart/aorta when stimulated by carbachol, a non-selective acetylcholine receptor agonist. Based on these results, we suggest that this technique can be useful for the quantitative determination of NO in biological samples.•

We report a method to measure NO by reacting it with carboxy-PTIO to form carboxy-PTI.

•

The carboxy-PTI is quantified by liquid chromatography mass spectrometry (LCMS).

•

This method can quantitate NO concentrations ranging from 5 nM to 1 µM

Sensitive electrochemical detection of nitric oxide based on AuPt and reduced graphene oxide nanocomposites

Since nitric oxide (NO) plays a critical role in many biological processes, its precise detection is essential toward an understanding of its specific functions. Here we report on a facile and environmentally compatible strategy for the construction of an electrochemical sensor based on reduced graphene oxide (rGO) and AuPt bimetallic nanoparticles. The prepared nanocomposites were further employed for the electroanalysis of NO using differential pulse voltammetry (DPV) and amperometric methods. The dependence of AuPt molar ratios on the electrochemical performance was investigated. Through the combination of the advantages of the high conductivity from rGO and highly electrocatalytic activity from AuPt bimetallic nanoparticles, the AuPt-rGO based NO sensor exhibited a high sensitivity of 7.35 μA μM(-1) and a low detection limit of 2.88 nM. Additionally, negligible interference from common ions or organic molecules was observed, and the AuPt-rGO modified electrode demonstrated excellent stability. Moreover, this optimized electrochemical sensor was practicable for efficiently monitoring the NO released from rat cardiac cells, which were stimulated by l-arginine (l-arg), showing that stressed cells generated over 10 times more NO than normal cells. The novel sensor developed in this study may have significant medical diagnostic applications for the prevention and monitoring of disease.

Gasotransmitter Heterocellular Signaling

SIGNIFICANCE

The family of gasotransmitter molecules, nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H₂S), has emerged as an important mediator of numerous cellular signal transduction and pathophysiological responses. As such, these molecules have been reported to influence a diverse array of biochemical, molecular, and cell biology events often impacting one another. Recent Advances: Discrete regulation of gasotransmitter molecule formation, movement, and reaction is critical to their biological function. Due to the chemical nature of these molecules, they can move rapidly throughout cells and tissues acting on targets through reactions with metal groups, reactive chemical species, and protein amino acids.

CRITICAL ISSUES

Given the breadth and complexity of gasotransmitter reactions, this field of research is expanding into exciting, yet sometimes confusing, areas of study with significant promise for understanding health and disease. The precise amounts of tissue and cellular gasotransmitter levels and where they are formed, as well as how they react with molecular targets or themselves, all remain poorly understood.

FUTURE DIRECTIONS

Elucidation of specific molecular targets, characteristics of gasotransmitter molecule heterotypic interactions, and spatiotemporal formation and metabolism are all important to better understand their true pathophysiological importance in various organ systems. Antioxid. Redox Signal. 26, 936-960.

Ratiometric SERS imaging and selective biosensing of nitric oxide in live cells based on trisoctahedral gold nanostructures

Herein, a ratiometric SERS probe was created for monitoring nitric oxide (NO) by designing a novel molecule, 3,4-diaminobenzene-thiol, and immobilizing this molecule onto trisoctahedral gold nanostructures with superior SERS capability. The established probe possessed good selectivity and biocompatibility, high sensitivity and accuracy, thus enabling imaging and biosensing of NO in live cells.