Analysis of Circulating microRNAs and Their Post-Transcriptional Modifications in Cancer Serum by On-Line Solid-Phase Extraction-Capillary Electrophoresis-Mass Spectrometry

Label-Free Direct Identification of MicroRNAs Based on a Narrow Constant-Inner-Diameter Emitter Mass Spectrometry Analysis

MicroRNAs (miRNAs) are a class of endogenous noncoding small RNAs that play important roles in various biological processes and diseases. Direct determination of miRNAs is a cost-efficient and accurate method for analysis. Herein, we established a novel method for the analysis of miRNAs based on a narrow constant-inner-diameter mass spectrometry emitter. We utilized the gravity-assisted sleeving etching method to prepare a constant-inner-diameter mass spectrometry emitter with a capillary inner diameter of 5.5 μm, coupled it with a high-voltage power supply and a high-resolution mass spectrometer, and used it for miRNA direct detection. The method showed high sensitivity and reproducibility for the analysis of four miRNAs, with a limit of detection of 100 nmol/L (170 amol) for the Hsa-miR-1290 analysis. Compared with commercial ion sources, our method achieved higher sensitivity for miRNA detection. In addition, we analyzed the total miRNAs in the A549 cells. The result indicated that both spiked and endogenous miRNAs could be quantified with high accuracy. As a result, this method offers a promising platform for highly sensitive and accurate miRNA analysis. Furthermore, this approach can be extended to the analysis of other small oligonucleotides and holds the potential for studying clinical samples and facilitating disease diagnosis.

miRNA and DNA analysis by negative ion electron transfer dissociation and infrared multiple-photon dissociation mass spectrometry

BACKGROUND

The use of simple and hybrid fragmentation techniques for the identification of molecules in tandem mass spectrometry provides different and complementary information on the structure of molecules. Nevertheless, these techniques have not been as widely explored for oligonucleotides as for peptides or proteins. The analysis of microRNAs (miRNAs) warrants special attention, given their regulatory role and their relationship with several diseases. The application of different fragmentation techniques will be very interesting for their identification.

RESULTS

Four synthetic miRNAs and a DNA sequence were fragmented in an ESI-FT-ICR mass spectrometer using both simple and hybrid fragmentation techniques: CID, nETD followed by CID, IRMPD, and, for the first time, nETD in combination with IRMPD. The main fragmentation channel was base loss. The use of nETD-IRMPD resulted in d/z, a/w, and c/y ions at higher intensities. Moreover, nETD-IRMPD provided high sequence coverage and low internal fragmentation. Native MS analysis revealed that only miR159 and the DNA sequence formed stable dimers under physiological ionic strength. The use of organic co-solvents or additives resulted in a lower sequence coverage due to lesser overall ionization efficiency.

NOVELTY

This work demonstrates that the combination of nETD and IRMPD for miRNA fragmentation constitutes a suitable alternative to common fragmentation methods. This strategy resulted in efficient fragmentation of [miRNA]5- using low irradiation times and fewer internal fragments while ensuring a high sequence coverage. Moreover, given that such low charge states predominate upon spraying in physiological-like conditions, native MS can be applied for obtaining structural information at the same time.

LC-MS-Based Direct Quantification of MicroRNAs in Rat Blood

MicroRNA (miRNA) has recently garnered significant research attention, owing to its potential as a diagnostic biomarker and therapeutic target. Liquid chromatography-mass spectrometry (LC-MS) offers accurate quantification, multiplexing capacity, and high compatibility with various matrices. These advantages establish it as a preferred technique for detecting miRNA in biological samples. In this study, we presented an LC-MS method for directly quantifying seven miRNAs (rno-miR-150, 146a, 21, 155, 223, 181a, and 125a) associated with immune and inflammatory responses in rat whole blood. To ensure miRNA stability in the samples and efficiently purify target analytes, we compared Trizol- and proteinase K-based extraction methods, and the Trizol extraction proved to be superior in terms of analytical sensitivity and convenience. Chromatographic separation was carried out using an oligonucleotide C18 column with a mobile phase composed of N-butyldimethylamine, 1,1,1,3,3,3-hexafluoro-2-propanol, and methanol. For MS detection, we performed high-resolution full scan analysis using an orbitrap mass analyzer with negative electrospray ionization. The established method was validated by assessing its selectivity, linearity, limit of quantification, accuracy, precision, recovery, matrix effect, carry-over, and stability. The proposed assay was then applied to simultaneously monitor target miRNAs in lipopolysaccharide-treated rats. Although potentially less sensitive than conventional methods, such as qPCR and microarray, this direct-detection-based LC-MS method can accurately and precisely quantify miRNA. Given these promising results, this method could be effectively deployed in various miRNA-related applications.

Progress in on-line, at-line, and in-line coupling of sample treatment with capillary and microchip electrophoresis over the past 10 years: A review

The review presents an evaluation of the development of on-line, at-line and in-line sample treatment coupled with capillary and microchip electrophoresis over the last 10 years. In the first part, it describes different types of flow-gating interfaces (FGI) such as cross-FGI, coaxial-FGI, sheet-flow-FGI, and air-assisted-FGI and their fabrication using molding into polydimethylsiloxane and commercially available fittings. The second part deals with the coupling of capillary and microchip electrophoresis with microdialysis, solid-phase, liquid-phase, and membrane based extraction techniques. It mainly focuses on modern techniques such as extraction across supported liquid membrane, electroextraction, single drop microextraction, head space microextraction, and microdialysis with high spatial and temporal resolution. Finally, the design of sequential electrophoretic analysers and fabrication of SPE microcartridges with monolithic and molecularly imprinted polymeric sorbents are discussed. Applications include the monitoring of metabolites, neurotransmitters, peptides and proteins in body fluids and tissues to study processes in living organisms, as well as the monitoring of nutrients, minerals and waste compounds in food, natural and wastewater.

Aptamer affinity-based microextraction in-line coupled to capillary electrophoresis mass spectrometry using a porous layer/nanoparticle -modified open tubular column

An aptamer affinity based microextraction column is developed to be directly in-line coupled to capillary electrophoresis-mass spectrometry (CE-MS) for analyzing mycotoxins in food samples. Single-stranded DNA aptamers for selective recognition of aflatoxin B1 (AFB1) and ochratoxin A (OTA) targets are co-immobilized via covalent bonds on the surface of the inlet end of a capillary, which is pre-modified with three-dimensional porous layer and gold nanoparticles to enhance the specific surface area and loading capacity. The outlet of the capillary is designed as a porous tip to serve as the spray source for injection to the mass spectrometry. All the necessary processes for pretreatment and analysis of a sample are accomplished in one injection, including aptamer affinity-based microextraction, CE separation and MS detection of analytes. AFB1 and OTA are simultaneously determined in a wide linear range with sample consumption of only 1 μL and the limit-of-detection as low as 1 pg/mL. The microextraction column exhibits excellent repeatability and stability, which can be used over 45 runs within a month with CE separation efficiency and only MS intensity slightly decreased. Mycotoxins in three kinds of cereal based infant foods are accurately analyzed using the proposed method. The study provides a robust and universal approach that would have potential applications in a variety of analytical fields based on selective molecular recognition coupling to CE-MS analysis.

Characterization of the Interaction of Polymeric Micelles with siRNA: A Combined Experimental and Molecular Dynamics Study

The simulation of large molecular systems remains a daunting challenge, which justifies the exploration of novel methodologies to keep computers as an ideal companion tool for everyday laboratory work. Whole micelles, bigger than 20 nm in size, formed by the self-assembly of hundreds of copolymers containing more than 50 repeating units, have until now rarely been simulated, due to a lack of computational power. Therefore, a flexible amphiphilic triblock copolymer (mPEG45-α-PLL10-PLA25) containing a total of 80 repeating units, has been emulated and synthesized to embody compactified nanoconstructs of over 900 assembled copolymers, sized between 80 and 100 nm, for siRNA complexing purposes. In this study, the tailored triblock copolymers containing a controlled number of amino groups, were used as a support model to address the binding behavior of STAT3-siRNA, in the formation of micelleplexes. Since increasingly complex drug delivery systems require an ever more optimized physicochemical characterization, a converging description has been implemented by a combination of experimentation and computational simulations. The computational data were advantageous in allowing for the assumption of an optimal N/P ratio favoring both conformational rigidifications of STAT3-siRNA with low competitive phenomena at the binding sites of the micellar carriers. These calculations were consistent with the experimental data showing that an N/P ratio of 1.5 resulted in a sufficient amount of complexed STAT3-siRNA with an electrical potential at the slipping plane of the nanopharmaceuticals, close to the charge neutralization.

Analysis of therapeutic nucleic acids by capillary electrophoresis

Nucleic acids are getting increased attention to fulfill unmet medical needs. The past five years have seen more than ten FDA approvals of nucleic acid based therapeutics. New analytical challenges have been posed in discovery, characterization, quality control and bioanalysis of therapeutic nucleic acids. Capillary electrophoresis (CE) has proven to be an efficient separation technique and has been widely used for analyzing oligonucleotides and nucleic acids. This review discusses the recent technical advances of CE in nucleic acid analysis such as polymeric matrices, separation conditions and detection methods, and the applications of CE to various therapeutic nucleic acids including antisense oligonucleotide (ASO), small interfering ribonucleic acid (siRNA), messenger RNA (mRNA), gene editing tools such as clustered regularly interspaced short palindromic repeats (CRISPR)-based gene and cell therapy, and other nucleic acid related therapeutics.

Pseudophase microextraction for in-line sample concentration in micellar electrokinetic chromatography

Pseudophase microextraction (PPME) as a simple in-line sample concentration technique in micellar electrokinetic chromatography (MEKC) is presented. In contrast to popular electric-field driven stacking techniques in MEKC such as sweeping, PPME is pressure-driven. The technique afforded up to 403-2968x improvements in peak heights for fenoprop, dichlorprop, 1- and 2-naphthol compared to typical injection. Under the same MEKC conditions, the improvements in PPME were up to 23-59x better compared to sweeping. Briefly in PPME, the entire capillary was loaded (up to 20 capillary volumes) with the sample prepared in a dilute solution of cetyltrimethylammonium bromide ([CTAB] > critical surface aggregation concentration). The CTAB formed aggregates at the inner capillary walls and these aggregates acted as a stationary chromatographic pseudophase. After clean-up via flushing the capillary with purified water, the MEKC background solution (BGS) with sodium dodecyl sulfate was then introduced by pressure from the outlet end to elute the retained analytes. The analytes concentrate at front of the BGS and the front was moved to the inlet end of the capillary prior to MEKC. Optimization strategies and current limitations in PPME-MEKC are described. The linear ranges using a 4 capillary volume sample load obtained for fenoprop, dichlorprop, 1- and 2-naphthol were between 1 and 160 ng/mL (r²s ≥ 0.996), LOQs = 1-2.5 ng/mL and repeatability %RSDs (n = 6) were ≤5% (intra-day) and ≤7% (inter-day) (using low analyte concentrations 1-5x LOQ). PPME-MEKC with simple dilution of fortified real samples (no off-line sample concentration) was also able to detect low levels of dichlorprop (10 ng/mL, limit set in Australia) and 1- and 2-naphthol (7.5-15 ng/mL) in a drinking water and natural water sample, respectively (% recovery = 84-108%). The concept of PPME may find use in other modes of capillary electrophoresis and other nano-microscale separations.

Impact of Nonspecific Adsorption to Metal Surfaces in Ion Pair-RP LC-MS Impurity Analysis of Oligonucleotides

Nonspecific adsorption has been a consistent challenge in the analysis of oligonucleotides. Nonspecific adsorption is a result of interactions between charged acidic analytes and adsorption sites present in metallic surfaces located in the fluidic path of chromatography systems. Due to their high surface area, adsorption to column frits is especially concerning. Poor peak shape, low recovery and compromised LOQ have been associated with this phenomenon. Alternative methods including substitution of stainless steel for different hardware materials and mobile phase additives have been explored in an attempt to minimize this issue. Chemical modification of metal surfaces using hybrid surface technology (HST) by-passes the limitation of stainless steel construction material by forming a hybrid organic/inorganic layer that acts as a barrier and limits nonspecific interactions. In this study we explore the implications of this new technology in sensitive analysis and determination of relative impurity levels of oligonucleotides. Higher relative impurity levels and better reproducibility were obtained with columns using HST.

Mass Spectrometry-Based Targeted Serum Monomethylated Ribonucleosides Profiling for Early Detection of Breast Cancer

RNA methylation plays a significant regulatory role in various of physiological activities and it has gradually become a hotspot of epigenetics in the past decade. 2′-O-methyladenosine (Am), 2′-O-methylguanosine (Gm), 2′-O-methylcytidine (Cm), 2′-O-methyluridine (Um), N⁶-methyladenosine (m⁶A), N¹-methylguanosine (m¹G), 5-methylcytidine (m⁵C), and 5-methyluridine (m⁵U) are representative 2′-O-methylation and base-methylation modified epigenetic marks of RNA. Abnormal levels of these ribonucleosides were found to be related to various diseases including cancer. Serum is an important source of biofluid for the discovery of biomarkers, and novel tumor biomarkers can be explored by measuring these ribonucleoside modifications in human serum. Herein, we developed and applied a hydrophilic interaction liquid chromatography tandem mass spectrometry (HILIC-MS/MS) method to determine the content of monomethylated ribonucleosides in human serum. The developed method enabled sensitive and accurate determination of these monomethylated ribonucleosides. By applying this robust method, we demonstrated the presence of Gm and Um in human serum for the first time, and we successfully quantified m⁶A, Gm, m¹G, Cm, Um and m⁵U in serum samples collected from 61 patients with breast cancer and 69 healthy controls. We discovered that the levels of Gm, m¹G, Cm, Um and m⁵U in serum were all significantly decreased in breast cancer patients whereas m⁶A was increased. We performed receiver operating characteristic (ROC) curve analysis, and obtained highest area under curve (AUC) value when combining these six monomethylated ribonucleosides together. These results suggest that m⁶A, Gm, m¹G, Cm, Um and m⁵U might have great potential to be novel biomarkers for detection of breast cancer in the early stage. In addition, this study may stimulate future investigations about the regulatory roles of monomethylated ribonucleosides on the initiation and development of breast cancer.

Quantitative Analysis of Methylated Adenosine Modifications Revealed Increased Levels of N 6-Methyladenosine (m6A) and N 6,2'-O-Dimethyladenosine (m6Am) in Serum From Colorectal Cancer and Gastric Cancer Patients

Colorectal cancer and gastric cancer are the most prevalent gastrointestinal malignancies worldwide, and early detection of these cancers is crucial to reduce their incidence and mortality. RNA methylation plays an important regulatory role in a variety of physiological activities, and it has drawn great attention in recent years. Methylated adenosine (A) modifications such as N⁶-methyladenosine (m⁶A), N¹-methyladenosine (m¹A), 2′-O-methyladenosine (Am), N⁶,2′-O-dimethyladenosine (m⁶Am), and N⁶,N⁶-dimethyladenosine (m⁶₂A) are typical epigenetic markers of RNA, and they are closely correlated to various diseases including cancer. Serum is a valuable source of biofluid for biomarker discovery, and determination of these adenosine modifications in human serum is desirable since they are emerging biomarkers for detection of diseases. In this work, a targeted quantitative analysis method using hydrophilic interaction liquid chromatography–tandem mass spectrometry (HILIC-MS/MS) was developed and utilized to analyze these methylated adenosine modifications in serum samples. The concentration differences between the healthy volunteers and cancer patients were evaluated by Mann–Whitney test, and receiver operator characteristic (ROC) curve analysis was performed to access the potential of these nucleosides as biomarkers. We demonstrated the presence of the m⁶Am in human serum for the first time, and we successfully quantified the concentrations of A, m⁶A, m¹A, and m⁶Am in serum samples from 99 healthy controls, 51 colorectal cancer patients, and 27 gastric cancer patients. We found that the levels of m⁶A and m⁶Am in serum were both increased in colorectal cancer or gastric cancer patients, compared to that in healthy controls. These results indicate that m⁶A and m⁶Am in serum may act as potential biomarkers for early detection and prognosis of colorectal cancer and gastric cancer. In addition, the present work will stimulate investigations on the effects of adenosine methylation on the initiation and progression of colorectal cancer and gastric cancer.

A hybrid nano-MOF/polymer material for trace analysis of fluoroquinolones in complex matrices at microscale by on-line solid-phase extraction capillary electrophoresis

A hybrid material (nano-metal organic framework@organic polymer, named as nano-MOF@polymer) was applied for the first time as sorbent for on-line solid-phase extraction capillary electrophoresis with ultraviolet detection (SPE-CE-UV). The resulting material was prepared building layer-by-layer a HKUST-1 (Hong Kong University of Science and Technology-1) nano-MOF onto the polymer surface, which allowed controlling the thickness and maximizing the active surface area. The sorbent was widely characterized at micro- and nano-scale to validate the synthesis and to establish the material properties. Then, fritless microcartridges (2 mm) were assembled by packing only a few micrograms of sorbent particles and investigated for preconcentration of fluoroquinolones (FQs) in several real samples (river water, human urine and whole cow milk). Under the optimized conditions, the sample (ca. 60 μL) was loaded in separation background electrolyte (BGE, 50 mM phosphate (pH 7)), and retained analytes were eluted using a small volume of 2% v/v formic acid in methanol (ca. 50 nL). The SPE-CE-UV method was validated in terms of linearity, limit of detection (LOD), limit of quantification (LOQ), repeatability, reproducibility and reusability. The developed method showed a LOD decreasing until 1 ng L^-1 when larger volumes of sample were loaded (ca. 180 μL), which was 500,000 times lower than by CE-UV. This undescribed sensitivity enhancement would arise from the homogenous and populated MOF nano-domains and the appropriate permeability of the hybrid material, which would promote high extraction efficiency and loading capacity. Furthermore, the sorbent showed appropriate selectivity regardless the analyzed complex environmental, biological or food matrix samples, achieving excellent detectability and recoveries (>90%).

Recent developments in the characterization of nucleic acids by liquid chromatography, capillary electrophoresis, ion mobility, and mass spectrometry (2010-2020)

The development of new strategies for the analysis of nucleic acids has gained momentum due to the increased interest in using these biomolecules as drugs or drug targets. The application of new mass spectrometry ion activation techniques and the optimization of separation methods including liquid chromatography, capillary electrophoresis, and ion mobility have allowed more detailed characterization of nucleic acids and oligonucleotide therapeutics including confirmation of sequence, localization of modifications and interaction sites, and structural analysis as well as identification of failed sequences and degradation products. This review will cover tandem mass spectrometry methods as well as the recent developments in liquid chromatography, capillary electrophoresis, and ion mobility coupled to mass spectrometry for the analysis of nucleic acids and oligonucleotides.

Ionic matrices for matrix-assisted laser desorption/ionization mass spectrometry analysis of microRNA biomarkers

The use of ionic matrices (IMs) was evaluated as an alternative to conventional matrices to analyze microRNAs (miRNAs) by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). 2, 4, 6-Trihydroxyacetophenone (THAP), 6-aza-2-thiothymine (ATT) and 3-hydroxypicolinic acid (3-HPA) and their IMs with pyridine (PYR) and butylamine (BA) were studied to analyze a standard mixture of miRNAs: miR-21, let-7g and iso-miR-16. Among all the studied matrices, ATT-PYR at 75 mg/mL in acetonitrile (MeCN):H₂O (50:50, v/v) was selected as the optimal. Furthermore, addition of ammonium citrate dibasic (AC) as signal enhancer was mandatory to obtain an appropriate miRNA detection. ATT-PYR provided the best sensitivity, with limit of detection (LOD) up to 5 nM (equivalent to 1 fmol in the spot) and excellent spot-to-spot repeatability due to the improved homogeneity of the spots compared to the conventional matrices. The applicability of the established method to direct, multiplex and untargeted analysis of miRNAs in serum samples was also investigated.

MASS SPECTROMETRY-BASED PERSONALIZED DRUG THERAPY

Personalized drug therapy aims to provide tailored treatment for individual patient. Mass spectrometry (MS) is revolutionarily involved in this area because MS is a rapid, customizable, cost-effective, and easy to be used high-throughput method with high sensitivity, specificity, and accuracy. It is driving the formation of a new field, MS-based personalized drug therapy, which currently mainly includes five subfields: therapeutic drug monitoring (TDM), pharmacogenomics (PGx), pharmacomicrobiomics, pharmacoepigenomics, and immunopeptidomics. Gas chromatography-MS (GC-MS) and liquid chromatography-MS (LC-MS) are considered as the gold standard for TDM, which can be used to optimize drug dosage. Matrix-assisted laser desorption ionization-time of flight-MS (MALDI-TOF-MS) significantly improves the capability of detecting biomacromolecule, and largely promotes the application of MS in PGx. It is becoming an indispensable tool for genotyping, which is used to discover and validate genetic biomarkers. In addition, MALDI-TOF-MS also plays important roles in identity of human microbiome whose diversity can explain interindividual differences of drug response. Pharmacoepigenetics is to study the role of epigenetic factors in individualized drug treatment. MS can be used to discover and validate pharmacoepigenetic markers (DNA methylation, histone modification, and noncoding RNA). For the emerging cancer immunotherapy, personalized cancer vaccine has effective immunotherapeutic activity in the clinic. MS-based immunopeptidomics can effectively discover and screen neoantigens. This article systematically reviewed MS-based personalized drug therapy in the above mentioned five subfields. © 2020 John Wiley & Sons Ltd. Mass Spec Rev.

Comparison of capillary electrophoresis and zwitterionic-hydrophilic interaction capillary liquid chromatography with ultraviolet and mass spectrometry detection for the analysis of microRNA biomarkers

This study evaluates zwitterionic-hydrophilic interaction capillary liquid chromatography (capZIC-HILIC) and capillary electrophoresis (CE) with ultraviolet (UV) and mass spectrometry (MS) detection for the direct, label-free and multiplex analysis of microribonucleic acids (miRNAs). CapZIC-HILIC-UV and CE-UV methods were first optimized, resulting in similar separations for a mixture of three miRNAs (hsa-iso-miR-16-5p, hsa-let-7g-5p, and hsa-miR-21-5p) but with reversal of elution/migration orders and small differences in repeatability, linearity, limit of detection (LOD) and separation efficiency. The established UV methods were transferred and validated in these terms with mass spectrometry (MS) detection, which allowed identifying the miRNAs and characterizing their post-transcriptional modifications. LOD by capZIC-HILIC-MS was 1 μM of miRNA, around 5 times lower than by CE-MS due to the analyte dilution with the sheathflow CE-MS interface and to the slightly increased abundance of alkali metals adducts in the CE-MS mass spectra. In addition, the suction effect promoted by the nebulizer gas in CE-MS negatively affected the already compromised separations. In contrast, CE-MS showed superior repeatabilities with spiked serum samples, as well as reduced costs, extended capillary column durabilities and shorter conditioning times. The comparison of the different methods allows disclosing the current advantages and disadvantages of capZIC-HILIC and CE for the analysis of miRNA biomarkers.

Improvement in Detection Limit for Lateral Flow Assay of Biomacromolecules by Test-Zone Pre-enrichment

Lateral flow assay (LFA) is one of the most prevalent commercially available techniques for point-of-care tests due to its simplicity, celerity, low cost and robust operation. However, conventional colorimetric LFAs have inferior limits of detection (LODs) compared to sophisticated laboratory-based assays. Here, we report a simple strategy of test-zone pre-enrichment to improve the LOD of LFA by loading samples before the conjugate pad assembly. The developed method enables visual LODs of miR-210 mimic and human chorionic gonadotropin protein, to be improved by 10–100 fold compared with a conventional LFA setup without introducing any additional instrument and reagent except for phosphate running buffer, while no obvious difference occurred for Aflatoxin B1 (AFB1). It takes about 6–8 min to enrich every 50 μL of sample diluted with phosphate running buffer, therefore we can get visual results within 20 min. We identified a parameter by modeling the entire process, the concentration of probe-analyte conjugate at test zone when signaling unit being loaded, to be important for the improvement of visual limit of detection. In addition, the test-zone pre-enrichment did not impair the selectivity when miR-210 mimic was adopted as target. Integrated with other optimization, amplification and modification of LFAs, the developed test-zone pre-enrichment method can be applied to further improve LOD of LFAs.

Applications of Mass Spectrometry for Clinical Diagnostics: The Influence of Turnaround Time

This critical review discusses how the need for reduced clinical turnaround times has influenced chemical instrumentation. We focus on the development of modern mass spectrometry (MS) and its application in clinical diagnosis. With increased functionality that takes advantage of novel front-end modifications and computational capabilities, MS can now be used for non-traditional clinical analyses, including applications in clinical microbiology for bacteria differentiation and in surgical operation rooms. We summarize here recent developments in the field that have enabled such capabilities, which include miniaturization for point-of-care testing, direct complex mixture analysis via ambient ionization, chemical imaging and profiling, and systems integration.

Analysis of glycopeptide biomarkers by on-line TiO2 solid-phase extraction capillary electrophoresis-mass spectrometry

In this study is described an on-line titanium dioxide solid-phase extraction capillary electrophoresis-mass spectrometry (TiO₂-SPE-CE-MS) method for the analysis of the glycopeptide glycoforms obtained from the tryptic digests of recombinant human erythropoietin (rhEPO). The O₁₂₆-glycopeptide of rhEPO was used to optimize the methodology given its importance in quality control of biopharmaceuticals and doping analysis. Several aspects that affect the selective retention and elution, peak efficiency and electrophoretic separation of the O₁₂₆ glycoforms were investigated to maximize detection sensitivity while minimizing non-specific retention of peptides. Under the optimized conditions, the microcartridge lifetime was around 10 analyses and repeatability was acceptable (%RSD values of 9-11% and 6-11% for migration times and peak areas, respectively). The method was linear between 0.5 and 50 mg L^-1 and 10-50 mg L^-1 for O₁₂₆ glycoforms containing NeuAc and NeuGc, respectively, and limits of detection (LODs) were up to 100 times lower than by CE-MS. Although optimized for O-glycopeptides, the method proved also successful for preconcentration of N₈₃-glycopeptides, without compromising the separation between glycopeptide glycoforms with different number of sialic acids. Tryptic digests of other glycoproteins (i.e. human apolipoprotein CIII (APO-C3) and bovine alpha-1-acid glycoprotein (bAGP)) were also analyzed, demonstrating the applicability to glycopeptides with different glycan composition and nature.

A triple signal amplification method for chemiluminescent detection of the cancer marker microRNA-21

Mesoporous silica nanospheres (MSNs) are used in a triple signal amplification chemiluminescent (CL) assay for microRNA-21. It is based on (a) the synergistic amplification via loading and controlled-release of signal reagents by MSNs, (b) target recycling amplification, and (c) the enhancement effect of graphene oxide quantum dots (GOQD). CL is generated by the bis(2,4,6-trichlorophenyl) oxalate (TCPO) and H₂O₂ reaction in the presence of the fluorophore rhodamine B (RB). RB is firstly loaded into the pores of MSNs modified with amino groupsand coupled with ssDNA. Then, the pores are capped by GOQD. Upon the addition of microRNA-21 into the system, the designed ssDNA assumes a double stranded structure. With the aid of duplex-specific nuclease, the double strand structure is cleaved and the free microRNA-21 enters into the next cycling process to combine with other ssDNA forming double strand structures. After several cycling process, amounts of GOQDs departing from the surface of MSNs cause the opening of the pores of MSNs and the release of RB causes the CL of TCPO-H₂O₂ reaction system. Free GOQDs can lead to a further CL enhancement. By this method, even a low amount of microRNA-21 leads to a large number of released RB molecules and triggers high-intensity CL. The method was applied in an assay where the CL signal increases linearly with the logarithm of the microRNA-21 concentration in the range of 0.005-50 pmol L^-1 and the detection limit is 1.7 fmol L^-1 (at 3σ). Graphical abstract Schematic presentation of a triple signal amplification chemiluminescence (CL) analysis platform based on rodamine B (RB) loading and controlled release, target recycling amplification and graphene oxide quantum dots (GOQD) as the enhancer for analysis of microRNA-21 in human serum.

A critical retrospective and prospective review of designs and materials in in-line solid-phase extraction capillary electrophoresis

Several strategies have been developed to decrease the concentration limits of detection (LODs) in capillary electrophoresis (CE). Nowadays, chromatographic-based preconcentration using a microcartridge integrated in the separation capillary for in-line solid-phase extraction capillary electrophoresis (SPE-CE) is one of the best alternatives for high throughput and reproducible sample clean-up and analyte preconcentration. This review covers different designs (geometrical configurations, with frits or fritless, capillary types, compatibility with commercial instrumentation, etc.) and materials (sorbents, supports, affinity ligands, etc.) applied for almost 30 years to prepare in-line SPE-CE microcartridges (i.e. analyte concentrators), with emphasis on the conventional unidirectional configuration in capillary format. Advantages, disadvantages and future perspectives are analyzed in detail to provide the reader a wide overview about the great potential of this technique to enhance sensitivity and address trace analysis.

MicroRNA-494-3p protects rat cardiomyocytes against septic shock via PTEN

The aim of the present study was to investigate the role of microRNA (miR)-494-3p in myocardial injury in patients with septic shock and the underlying mechanism. A total of 22 patients with sepsis and 17 patients with septic shock were included in the present study. In addition, 20 healthy subjects were recruited as the control group. Peripheral blood was collected from all subjects and a rat cardiomyocyte model of myocardial injury was constructed. Reverse transcription-quantitative polymerase chain reaction was used to measure miR-494-3p expression, while cell counting kit-8 assays were performed to assess cell proliferation. Flow cytometry was performed to investigate cell cycle distribution and apoptosis. Lactate dehydrogenase (LDH) assays were performed to measure LDH levels. ELISA was also performed to measure LDH, tumor necrosis factor (TNF)-α and interleukin (IL)-6 levels in cell culture supernatants. Western blotting was employed to detect phosphatase and tensin homolog (PTEN) protein expression and dual luciferase reporter assays were performed to identify the interaction between miR-494-3p and PTEN mRNA. Reduced miR-494-3p expression was correlated with myocardial damage in patients with septic shock. Sera from patients with septic shock downregulated miR-494-3p expression in rat cardiomyocytes. miR-494-3p overexpression inhibited rat cardiomyocyte injury induced by treatment with sera from patients with septic shock. Furthermore, miR-494-3p overexpression reduced the synthesis and release of TNF-α and IL-6 from rat cardiomyocytes. PTEN knockdown alleviated rat cardiomyocyte injury following treatment with serum from patients with septic shock. PTEN was demonstrated to induce the release of TNF-α and IL-6 from rat cardiomyocytes treated with septic shock serum, while miR-494-3p was demonstrated to bind to the 3′-untranslated seed region of PTEN mRNA to regulate its expression. The results of the present study suggest that miR-494-3p is downregulated in the peripheral blood of patients with septic shock and is negatively correlated with myocardial injury. The present study also indicates that miR-494-3p regulates PTEN expression, inhibits sepsis-induced myocardial injury and protects the function of cardiomyocytes. The protective effect and mechanism of action of miR-494-3p indicate that it has potential for use in the clinical diagnosis and therapy of myocardial damage.

Recent advances in capillary electrophoresis-mass spectrometry: Instrumentation, methodology and applications

Capillary electrophoresis (CE) offers fast and high-resolution separation of charged analytes from small injection volumes. Coupled to mass spectrometry (MS), it represents a powerful analytical technique providing (exact) mass information and enables molecular characterization based on fragmentation. Although hyphenation of CE and MS is not straightforward, much emphasis has been placed on enabling efficient ionization and user-friendly coupling. Though several interfaces are now commercially available, research on more efficient and robust interfacing with nano-electrospray ionization (ESI), matrix-assisted laser desorption/ionization (MALDI) and inductively coupled plasma mass spectrometry (ICP) continues with considerable results. At the same time, CE-MS has been used in many fields, predominantly for the analysis of proteins, peptides and metabolites. This review belongs to a series of regularly published articles, summarizing 248 articles covering the time between June 2016 and May 2018. Latest developments on hyphenation of CE with MS as well as instrumental developments such as two-dimensional separation systems with MS detection are mentioned. Furthermore, applications of various CE-modes including capillary zone electrophoresis (CZE), nonaqueous capillary electrophoresis (NACE), capillary gel electrophoresis (CGE) and capillary isoelectric focusing (CIEF) coupled to MS in biological, pharmaceutical and environmental research are summarized.