Recent advancements in the sensitivity of chemical instrumentation have led to increased interest in the use of microsamples for translational and biomedical research. Paper substrates are by far the ...most widely used media for biofluid collection, and mass spectrometry is the preferred method of analysis of the resultant dried blood spot (DBS) samples. Although there have been a variety of review papers published on DBS, there has been no attempt to unify the century old DBS methodology with modern applications utilizing modified paper and paper‐based microfluidics for sampling, storage, processing, and analysis. This critical review will discuss how mass spectrometry has expanded the utility of paper substrates from sample collection and storage, to direct complex mixture analysis to on‐surface reaction monitoring.
The identification of new photocatalytic pathways expands our knowledge of chemical reactivity and enables new environmentally friendly synthetic applications. However, the development of ...miniaturized screening procedures/platforms to expedite the discovery of photochemical reactions remains challenging. Herein, we describe a picomole‐scale, real‐time photoreaction screening platform in which a handheld laser source is coupled with nano‐electrospray ionization mass spectrometry. By using this method, we discovered an accelerated dehydrogenation pathway for the conversion of tetrahydroquinolines into the corresponding quinolines. This transformation is readily promoted by an off‐the‐shelf Ru(bpy)3Cl2⋅6 H2O complex in air at ambient temperature in direct sunlight, or with the aid of an energy‐saving lamp. Moreover, radical cations and trans‐dihydride intermediates captured by the screening platform provided direct evidence for the mechanism of the photoredox reaction.
The here and now of it: A picomole‐scale, real‐time platform based on mass spectrometry for the screening of photoredox reactions enabled the discovery of an accelerated photocatalytic transformation of tetrahydroquinolines into quinolines under ambient conditions (see scheme). The screening platform also has the advantage that key mechanistic information can be derived from captured intermediates.
Chemical analysis by analytical instrumentation has played a major role in disease diagnosis, which is a necessary step for disease treatment. While the treatment process often targets specific ...organs or compounds, the diagnostic step can occur through various means, including physical or chemical examination. Chemically, the genome may be evaluated to give information about potential genetic outcomes, the transcriptome to provide information about expression actively occurring, the proteome to offer insight on functions causing metabolite expression, or the metabolome to provide a picture of both past and ongoing physiological function in the body. Mass spectrometry (MS) has been elevated among other analytical instrumentation because it can be used to evaluate all four biological machineries of the body. In addition, MS provides enhanced sensitivity, selectivity, versatility, and speed for rapid turnaround time, qualities that are important for instance in clinical procedures involving the diagnosis of a pediatric patient in intensive care or a cancer patient undergoing surgery. In this review, we provide a summary of the use of MS to evaluate biomarkers for newborn screening and cancer diagnosis. As many reviews have recently appeared focusing on MS methods and instrumentation for metabolite analysis, we sought to describe the biological basis for many metabolomic and additional omics biomarkers used in newborn screening and how tandem MS methods have recently been applied, in comparison to traditional methods. Similar comparison is done for cancer screening, with emphasis on emerging MS approaches that allow biological fluids, tissues, and breath to be analyzed for the presence of diagnostic metabolites yielding insight for treatment options based on the understanding of prior and current physiological functions of the body.
Current analytical methods, either point-of-care or centralized detection, are not able to meet recent demands of patient-friendly testing and increased reliability of results. Here, we describe a ...two-point separation on-demand diagnostic strategy based on a paper-based mass spectrometry immunoassay platform that adopts stable and cleavable ionic probes as mass reporter; these probes make possible sensitive, interruptible, storable, and restorable on-demand detection. In addition, a new touch paper spray method was developed for on-chip, sensitive, and cost-effective analyte detection. This concept is successfully demonstrated via (i) the detection of Plasmodium falciparum histidine-rich protein 2 antigen and (ii) multiplexed and simultaneous detection of cancer antigen 125 and carcinoembryonic antigen.
The fusion of non‐thermal plasma with charged microdroplets facilitates catalyst‐free N‐alkylation for a variety of primary amines, without halide salt biproduct generation. Significant reaction ...enhancement (up to >200×) is observed over microdroplet reactions generated from electrospray. This enhancement for the plasma‐microdroplet system is attributed to the combined effects of energetic collisions and the presence of reactive oxygen species (ROS). The ROS (e.g., O2⋅−) act as a proton sink to increase abundance of free neutral amines in the charged microdroplet environment. The effect of ROS on N‐alkylation is confirmed through three unique experiments: (i) utilization of radical scavenging reagent, (ii) characterization of internal energy distribution, and (iii) controls performed without plasma, which lacked reaction acceleration. Establishing plasma discharge in the wake of charged microdroplets as a green synthetic methodology overcomes two major challenges within conventional gas‐phase plasma chemistry, including the lack of selectivity and product scale‐up. Both limitations are overcome here, where dual tunability is achieved by controlling reagent concentration and residence time in the microdroplet environment, affording single or double N‐alkylated products. Products are readily collected yielding milligram quantities in eight hours. These results showcase a novel synthetic strategy that represents a straightforward and sustainable C−N bond‐forming process.
The uncatalyzed N‐alkylation of primary amines via a dual tunable plasma‐microdroplet reaction platform is enabled by the in situ generation of reactive oxygen species during electrospray. Tuning the initial reagent concentration and timescale of the plasma‐microdroplet system allows selected N‐alkylation products to be collected under ambient conditions.
Positional isomers of alkenes are frequently transparent to the mass spectrometer and it is difficult to provide convincing data to support their presence. This work focuses on the development of a ...new reactive nano-electrospray ionization (nESI) platform that utilizes non-inert metal electrodes (
e.g.
, Ir and Ru) for rapid detection of fatty acids by mass spectrometry (MS), with concomitant localization of the C&z.dbd;C bond to differentiate fatty acid isomers. During the electrospray process, the electrical energy (direct current voltage) is harnessed for
in situ
oxide formation on the electrode surface
via
electro-oxidation. The as-formed surface oxides are found to facilitate
in situ
epoxide formation at the C&z.dbd;C bond position and the products are analyzed by MS in real-time. This phenomenon has been applied to analyze isomers of unsaturated fatty acids from complex serum samples, without pre-treatment.
An electrocatalytic nESI MS platform enables positional isomer differentiation through the localization of C&z.dbd;C bonds in fatty acids present in complex biofluids.
Online, droplet-based in-source chemical derivatization is accomplished using a coaxial-flow contained-electrospray ionization (contained-ESI) source to enhance sensitivity for the mass spectrometric ...analysis of saccharides. Derivatization is completed in microseconds by exploiting the reaction rate acceleration afforded by electrospray microdroplets. Significant improvements in method sensitivity are realized with minimal sample preparation and few resources when compared to traditional benchtop derivatizations. For this work, the formation of easily ionizable phenylboronate ester derivatives of several mono-, di-, and oligosaccharides is achieved. Various reaction parameters including concentration and pH were evaluated, and a Design of Experiments approach was used to optimize ion source parameters. Signal enhancements of greater than two orders of magnitude were observed for many mono- and disaccharides using in-source phenylboronic acid derivatization, resulting in parts-per-trillion (picomolar) limits of detection. In addition, amino sugars such as glucosamine, which do not ionize in negative mode, were detected at low parts-per-billion concentrations, and isobaric sugars such as lactose and sucrose were easily distinguished. The new in-source derivatization approach can be employed to expand the utility of ESI-MS analysis for compounds that historically experience limited sensitivity and detectability, while avoiding resource-intensive, bulk-phase derivatization procedures.
Ambient electrostatic paper spray ionization from a hydrophobic paper occurs when a DC potential is applied to the dry paper triangle. Online liquid/liquid extraction of small organic compounds from ...a drop of biological fluid present on the dry hydrophobic paper is achieved with an organic spray solvent in under 1 min and utilizes in situ electrostatic-spray ionization for more efficient detection of extracted molecules. Direct analysis of small volumes of biofluids with no sample pretreatment is possible, which is applicable in point-of-care analyses. High sensitivity and quantitative accuracy was achieved for the direct analysis of illicit drugs in 4 μL of raw blood, serum, and whole urine. The study was extended to monitor the activity of alanine transaminase enzyme, a key biomarker for the detection of liver injury in patients (with HIV and tuberculosis) who typically take several medications at once.
Determination of pesticide residues in a wide variety of matrices is an ongoing challenge due to low concentration and substantial amounts of interfering endogenous compounds that can be coextracted ...with the analytes. Herein, we describe the use of cellulose thread both as a suitable sampling medium for various matrices and as a direct analysis platform through an improved thread spray mass spectrometry (MS) approach. Enhanced extraction and the subsequent generation of tiny nanodroplets, after the application of DC potential to the wet thread, enabled ultra-sensitive detection of pesticides without prior sample treatment. This methodology was applied to quantify glyphosate and its metabolite, aminomethylphosphonic acid, in surface water at 12.2 μg mL
−1
limit of detection (LOD)
via
standard addition calibration. The method was also used for an internal standard calibration for the analysis of atrazine, which resulted in a LOD of 0.74 ng mL
−1
. The enhanced thread spray MS platform also proved effective when applied for direct analysis of diphenylamine and thiabendazole, which enabled the evaluation of post-harvest pesticide treatment of fruits (surface and interior) without complete destruction of the fruits.
Cellulose thread substrates enable sampling and direct mass spectrometry analysis of structurally different pesticides from various matrices without sample preparation.
Apohemoglobin (apoHb) is a dimeric globular protein with two vacant heme‐binding pockets that can bind heme or other hydrophobic ligands. Purification of apoHb is based on partial hemoglobin (Hb) ...unfolding to facilitate heme extraction into an organic solvent. However, current production methods are time consuming, difficult to scale up, and use highly flammable and toxic solvents. In this study, a novel and scalable apoHb production method was developed using an acidified ethanol solution to extract the hydrophobic heme ligand into solution and tangential flow filtration to separate heme from the resultant apoprotein. Total protein and active protein yields were >95% and ~75%, respectively, with <1% residual heme in apoHb preparations and >99% purity from sodium dodecyl sulfate–polyacrylamide gel electrophoresis analysis. Virtually no loss of apoHb activity was detected at 4°C, −80°C, and in lyophilized form during long term storage. Structurally, size exclusion chromatography (SEC) and circular dichroism indicated that apoHb was dimeric with a ~25% reduction of helical content compared to Hb. Furthermore, mass spectroscopy and reverse‐phase chromatography indicated that the mass of the α and β subunits were virtually identical to the theoretical mass of these subunits in Hb and had no detectable oxidative modifications upon heme removal from Hb. SEC confirmed that apoHb bound to haptoglobin at a similar ratio to that of native Hb. Finally, reconstituted Hb (rHb) was processed via a hemichrome removal method to isolate functional rHb for biophysical characterization in which the O2 equilibrium curve, O2 dissociation, and CO association kinetics of rHb were virtually identical to native Hb. Overall, this study describes a novel and improved method to produce apoHb, as well as presents a comprehensive biochemical analysis of apoHb and rHb.
Apohemoglobin (apoHb) is a dimeric globular protein with two vacant heme‐binding pockets that can bind heme or other hydrophobic ligands, making it useful for a diverse set of biomedical applications. Purification of apoHb is based on partial hemoglobin (Hb) unfolding to facilitate heme extraction into an organic solvent. In this article, the authors developed a novel manufacturing method to produce apohemoglobin using acidified ethanol as a heme‐extraction solvent and employing tangential flow filtration for separation. These process characteristics yield a safe, efficient and scalable method for producing apohemoglobin.
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