Direct identification of microribonucleic acid miR-451 from plasma using liquid chromatography mass spectrometry

Advances in analytical technologies for emerging drug modalities and their separation challenges in LC-MS systems

The last few years have seen a rise in the identification and development of bio-therapeutics through the use of cutting-edge delivery methods or bio-formulations, which has created bio-analytical difficulties. Every year, new bio-pharmaceutical product innovations come out, but the analytical development of these products is challenging. Quantifying the products and components of conjugated molecular structures is essential for preclinical and clinical research in order to guide therapeutic development, given their intrinsic complexity. Furthermore, a significant amount of information is needed for the measurement of these unique modalities by LC-MS techniques. Numerous LC-MS based methods have been developed, including AEX-HPLC-MS, RP-IP-LCMS, HILIC-MS, LCHRMS, Microflow-LC-MS, ASMS, Hybrid LBA/LC-MS, and more. However, these methods continue to face problems, prompting the development of alternative approaches. Therefore, developing bio-molecules that are this complicated and, low in concentration requires a skilled LC-MS based approach and knowledgeable personnel. This review covers general novel modalities classifications, sample preparation techniques, current status and bio-analytical strategies for analyzing various novel modalities, including gene bio-therapeutics, oligonucleotides, antibody-drug conjugates, monoclonal antibodies and PROTACs. It also covers how these strategies have been used in the past and how they are being used now to address challenges in the development of LC-MS based methods, as well as improvement strategies, current advancements and recent developed methods. We additionally covered on the benefits and drawbacks of different LC-MS based techniques for the examination of bio-pharmaceutical products and the future perspectives.

Comparison of multiple bioanalytical assay platforms for the quantitation of siRNA therapeutics

Aim: Oligonucleotide therapeutics can be quantified using various bioanalytical methods, and these methods have been compared extensively. However, few comparisons exist where the same analyte is evaluated by multiple assay platforms.Materials & methods: Hybrid LC-MS, SPE-LC-MS, HELISA and SL-RT-qPCR methods were developed for an siRNA analyte, and samples from a pharmacokinetic study were analyzed by all four methods.Results: All assay platforms provided comparable data, though higher concentrations were observed using the non-LC-MS assays. Hybrid LC-MS and SL-RT-qPCR were the most sensitive methodologies, and SL-RT-qPCR and HELISA demonstrated the highest throughput.Conclusion: Each assay platform is suitable for oligonucleotide bioanalysis, and the ultimate choice of methodology will depend on the prioritization of needs such as sensitivity, specificity and throughput.

Abundance of Modifications in Mature miRNAs Revealed by LC-MS/MS Method Coupled with a Two-Step Hybridization Purification Strategy

Accurate detection of endogenous miRNA modifications, such as N6-methyladenosine (m6A), 7-methylguanosine (m7G), and 5-methylcytidine (m5C), poses significant challenges, resulting in considerable uncertainty regarding their presence in mature miRNAs. In this study, we demonstrate for the first time that liquid chromatography coupled with a tandem mass spectrometry (LC-MS/MS) nucleoside analysis method is a practical tool for quantitatively analyzing human miRNA modifications. The newly designed liquid-solid two-step hybridization (LSTH) strategy enhances specificity for miRNA purification, while LC-MS/MS offers robust capability in recognizing modifications and sufficient sensitivity with detection limits ranging from attomoles to low femtomoles. Therefore, it provides a more reliable approach compared to existing techniques for revealing modifications in endogenous miRNAs. With this approach, we characterized m6A, m7G, and m5C modifications in miR-21-5p, Let-7a/e-5p, and miR-10a-5p isolated from cultured cells and observed unexpectedly low abundance (<1% at each site) of these modifications.

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.

Observations from a decade of oligonucleotide bioanalysis by LC-MS

There is a growing need for efficient bioanalysis of oligonucleotide therapeutics. This broad class of molecules presents numerous challenges relative to traditional small molecule therapeutics. Methodologies including ligand-binding assays or polymerase chain reaction may be fit-for-purpose in many instances, but liquid chromatography coupled to mass spectrometry (LC-MS) often delivers the best balance of sensitivity and selectivity. Over the last decade, we have engaged with many such molecules and derived insights into challenges and solutions. Herein, we provide four case studies illustrating challenges we have encountered. These issues include low or variable analyte recovery, poor resolution from related species, chromatographic abnormalities or challenging sensitivity. We present a summary of considerations, based on these experiences, to assist others working in the area.

Mobile Phase Aging and Its Impact on Electrospray Ionization of Oligonucleotides

The implementation of fluoroalcohol/alkylamine mobile phase systems in oligonucleotide LC-MS provides a good balance between chromatographic separations and MS sensitivity. Since its introduction, several parameters including mobile phase composition, additive concentration, alkylamine hydrophobicity, and different fluoroalcohols have been carefully evaluated and optimized. While our understanding of this mobile phase system has increased over the years, there are challenges that continue to hinder method performance and remain poorly understood. One of these challenges is the constant loss of MS sensitivity over time, commonly termed mobile phase aging. This study investigates two aging mechanisms associated with loss of MS sensitivity: alkylamine oxidation and aggregate formation. The relationship between pH, organic solvent, oxygen, and mobile phase aging is characterized, and mitigation strategies to extend mobile phase lifetime are discussed.

Exploring the theranostic potentials of miRNA and epigenetic networks in autoimmune diseases: A comprehensive review

BACKGROUND

Autoimmune diseases (AD) are severe pathophysiological ailments that are stimulated by an exaggerated immunogenic response towards self-antigens, which can cause systemic or site-specific organ damage. An array of complex genetic and epigenetic facets majorly contributes to the progression of AD, thus providing significant insight into the regulatory mechanism of microRNA (miRNA). miRNAs are short, non-coding RNAs that have been identified as essential contributors to the post-transcriptional regulation of host genome expression and as crucial regulators of a myriad of biological processes such as immune homeostasis, T helper cell differentiation, central and peripheral tolerance, and immune cell development.

AIMS

This article tends to deliberate and conceptualize the brief pathogenesis and pertinent epigenetic regulatory mechanism as well as miRNA networks majorly affecting five different ADs namely rheumatoid arthritis (RA), type 1 diabetes, multiple sclerosis (MS), systemic lupus erythematosus (SLE) and inflammatory bowel disorder (IBD) thereby providing novel miRNA-based theranostic interventions.

RESULTS & DISCUSSION

Pertaining to the differential expression of miRNA attributed in target tissues and cellular bodies of innate and adaptive immunity, a paradigm of scientific expeditions suggests an optimistic correlation between immunogenic dysfunction and miRNA alterations.

CONCLUSION

Therefore, it is not astonishing that dysregulations in miRNA expression patterns are now recognized in a wide spectrum of disorders, establishing themselves as potential biomarkers and therapeutic targets. Owing to its theranostic potencies, miRNA targets have been widely utilized in the development of biosensors and other therapeutic molecules originating from the same.

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.

Evaluating the use of locked nucleic acid capture probes in hybrid LC-MS/MS analysis of siRNA analytes

Background: Hybrid LC-MS assays for oligonucleotides rely on capture probes to develop assays with high sensitivity and specificity. Locked nucleic acid (LNA) probes are thermodynamically superior to existing capture probes, but are not currently used for hybrid LC-MS assays. Materials & methods: Using two lipid-conjugated double-stranded siRNA compounds as model analytes, hybrid LC-MS/MS assays using LNA probes were developed. Results: The workflows demonstrated the superiority of the LNA probes, optimized sample preparation conditions to maximize analyte recovery, evaluated the need for analyte-specific internal standards, and demonstrated that advanced mass spectrometric technology can increase assay sensitivity by up to 20-fold. Conclusion: The workflow can be used in future bioanalytical studies to develop effective hybrid LC-MS/MS methods for siRNA analytes.

Managing nonspecific adsorption to liquid chromatography hardware: A review

The choice of alternative materials over stainless steel hardware in the construction of liquid chromatography systems has unveiled the degree to which nonspecific adsorption impacts the reproducibility of LC methods. Some of the major contributors to nonspecific adsorption losses are charged metallic surfaces and leached metallic impurities, that may interact with the analyte and result in analyte loss and overall poor chromatographic performance. In this review, we describe several mitigation strategies available to chromatographers to minimize nonspecific adsorption to chromatographic systems. Alternative surfaces to stainless steel such as titanium, PEEK, and hybrid surface technologies are discussed. Furthermore, mobile phase additives used to prevent metal ion-analyte interactions are reviewed. Nonspecific adsorption of analytes is not reserved to metallic surfaces, as analytes may adsorb to the surfaces of filters, tubes, and pipette tips during sample preparation. Identifying the source of nonspecific interactions is paramount, as mitigation strategies may differ depending on what stage nonspecific losses are taking place. With this in mind, we discuss diagnostic methods that may help the chromatographer to differentiate losses resulting from sample preparation, and losses during LC runs.

A Novel Hybridization LC-MS/MS Methodology for Quantification of siRNA in Plasma, CSF and Tissue Samples

Therapeutic oligonucleotides, such as antisense oligonucleotide (ASO) and small interfering RNA (siRNA), are a new class of therapeutics rapidly growing in drug discovery and development. A sensitive and reliable method to quantify oligonucleotides in biological samples is critical to study their pharmacokinetic and pharmacodynamic properties. Hybridization LC-MS/MS was recently established as a highly sensitive and specific methodology for the quantification of single-stranded oligonucleotides, e.g., ASOs, in various biological matrices. However, there is no report of this methodology for the bioanalysis of double-stranded oligonucleotides (e.g., siRNA). In this work, we investigated hybridization LC-MS/MS methodology for the quantification of double-stranded oligonucleotides in biological samples using an siRNA compound, siRNA-01, as the test compound. The commonly used DNA capture probe and a new peptide nucleic acid (PNA) probe were compared for the hybridization extraction of siRNA-01 under different conditions. The PNA probe achieved better extraction recovery than the DNA probe, especially for high concentration samples, which may be due to its stronger hybridization affinity. The optimized hybridization method using the PNA probe was successfully qualified for the quantitation of siRNA-01 in monkey plasma, cerebrospinal fluid (CSF), and tissue homogenates over the range of 2.00-1000 ng/mL. This work is the first report of the hybridization LC-MS/MS methodology for the quantification of double-stranded oligonucleotides. The developed methodology will be applied to pharmacokinetic and toxicokinetic studies of siRNA-01. This novel methodology can also be used for the quantitative bioanalysis of other double-stranded oligonucleotides.

Bioanalysis of Oligonucleotide by LC-MS: Effects of Ion Pairing Regents and Recent Advances in Ion-Pairing-Free Analytical Strategies

Oligonucleotides (OGNs) are relatively new modalities that offer unique opportunities to expand the therapeutic targets. Reliable and high-throughput bioanalytical methods are pivotal for preclinical and clinical investigations of therapeutic OGNs. Liquid chromatography-mass spectrometry (LC-MS) is now evolving into being the method of choice for the bioanalysis of OGNs. Ion paring reversed-phase liquid chromatography (IP-RPLC) has been widely used in sample preparation and LC-MS analysis of OGNs; however, there are technical issues associated with these methods. IP-free methods, such as hydrophilic interaction liquid chromatography (HILIC) and anion-exchange techniques, have emerged as promising approaches for the bioanalysis of OGNs. In this review, the state-of-the-art IP-RPLC-MS bioanalytical methods of OGNs and their metabolites published in the past 10 years (2012-2022) are critically reviewed. Recent advances in IP-reagent-free LC-MS bioanalysis methods are discussed. Finally, we describe future opportunities for developing new methods that can be used for the comprehensive bioanalysis of OGNs.

Microflow LC-MS/MS to improve sensitivity for antisense oligonucleotides bioanalysis: critical role of sample cleanness

Background: Quantitative bioanalysis of antisense oligonucleotides (ASOs) is crucial to study their pharmacokinetic properties. An ultrasensitive bioanalytical method is often desired for quantifying low-concentration ASOs. Results: Effects of microflow LC and sample cleanness on sensitivity improvement of ASOs were evaluated. Sixfold sensitivity improvement of ASO-001 was achieved using microflow LC-MS/MS compared with conventional analytical flow method. Different sample extracts (hybridization, SPE and protein precipitation) were evaluated for sensitivity improvement by microflow LC. More sensitivity improvement was observed in the cleaner sample extract. Conclusion: Microflow LC increases sensitivity for ASO bioanalysis. The cleaner the sample extract, the better the sensitivity improvement. An ultrasensitive hybridization microflow LC-MS/MS method with lower limit of quantification of 0.100 ng/ml was developed and qualified for quantifying ASO-001 in plasma.

Development of the Method for Nusinersen and Its Metabolites Identification in the Serum Samples of Children Treated with Spinraza for Spinal Muscular Atrophy

The application of oligonucleotides as drugs for different genetic diseases is increasing rapidly. Since 2016 they are used during spinal muscular atrophy treatment with the use of nusinersen oligonucleotide. The purpose of this study was to improve methods for the analysis of serum samples of patients treated with nusinersen. The results showed that liquid-liquid extraction (with phenol/chloroform) is insufficient and an additional purification step using solid-phase extraction is necessary. The best results were obtained for microextraction by packed sorbents. Important parameters in the optimization of the method were mainly the type of amine in the mobile phase and the stationary phase. Both influenced the selectivity of metabolite separation and thus their correct identification; while amine type impacted also the intensity of signals. Finally, the highest resolution of separation and the highest peak areas were obtained for N,N-dimethylbutylamine or N,N-diisopropylthylamine with an octadecyl column with a terminal aryl group. Over a dozen of metabolites were successfully identified with the use of methods developed during the study. The 3′ exonucleases and 5′ exonucleases were mainly responsible for nusinersen metabolism, consequently, 3′end shortmers, and 5′end shortmers were observed, as well as metabolites with simultaneous loss of bases at both ends of the sequence. However, some depurination and depyrimidination products were also identified. To the best of our knowledge, this is the first report on nusinersen and its metabolite identification in serum samples by liquid chromatography and mass spectrometry.

Oligonucleotides Isolation and Separation—A Review on Adsorbent Selection

Oligonucleotides have many important applications, including as primers in polymerase chain reactions and probes for DNA sequencing. They are proposed as a diagnostic and prognostic tool for various diseases and therapeutics in antisense therapy. Accordingly, it is necessary to develop liquid chromatography and solid phase extraction methods to separate oligonucleotides and isolate them from biological samples. Many reviews have been written about the determination of these compounds using the separation technique or sample preparation for their isolation. However, presumably, there are no articles that critically review the adsorbents used in liquid chromatography or solid phase extraction. The present publication reviews the literature from the last twenty years related to supports (silica, polymers, magnetic nanoparticles) and their modifications. The discussed issues concern reversed phase (alkyl, aromatic, cholesterol, mixed ligands), ion-exchange (strong and weak ones), polar (silica, polyhydroxy, amide, zwitterionic), and oligonucleotide-based adsorbents.

Validation and application of hybridization liquid chromatography-tandem mass spectrometry methods for quantitative bioanalysis of antisense oligonucleotides

Background: Antisense oligonucleotide (ASO), an emerging modality in drug research and development, demands accurate and sensitive bioanalysis to understand its pharmacokinetic and pharmacodynamic properties. Results: By combining the advantages of both ligand binding and liquid chromatography-mass spectrometry/tandem mass (LC-MS/MS), hybridization LC-MS/MS methods were successfully developed and validated/qualified in a good lab practice (GLP) environment for the quantitation of an ASO drug candidate in monkey serum, cerebrospinal fluid (CSF) and tissues in the range of 0.5-500 ng/ml. Special treatment of CSF samples was employed to mitigate nonspecific binding, improve long-term storage stability and enable the usage of artificial CSF as a more accessible surrogate matrix. The method was also qualified and applied to ASO quantitation in various monkey tissue samples using a cocktail tissue homogenate as a surrogate matrix. Conclusion: This work was the first reported GLP validation and application of ASO bioanalysis using the hybridization LC-MS/MS platform.

Effect of ion-pairing reagent hydrophobicity on liquid chromatography and mass spectrometry analysis of oligonucleotides

We performed a systematic study of thirteen alkylamines used as ion-pairing reagents for ion-pair reversed-phase liquid chromatography (IP RP LC) separations of oligonucleotides on a C18 column. We proposed a method to classify the hydrophobicity of alkylamines by their retention in RP LC. The IP reagent hydrophobicity correlated with the retention and resolution of oligonucleotides in the corresponding IP mobile phases. The baseline resolution was achieved up to 30 mer for hydrophilic, or up to 50 mer for hydrophobic IP reagents. Hydrophobic alkylamines permitted useful oligonucleotide separations at relatively low buffer concentrations, such as 5-10 mM alkylamine-acetate IP systems. These buffers were compatible with mass spectrometry detection, however, replacement of acetic acid with hexafluoroisopropanol in the mobile phase improved the MS signal by 2-3 orders of magnitude. Experiments with native and chemically modified oligonucleotides highlighted the mixed-mode nature of IP RP LC. When using hydrophobic IP reagents, the ionic retention mechanism of oligonucleotides is enhanced while hydrophobic retention is diminished.

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.

Assessing the impact of nonspecific binding on oligonucleotide bioanalysis

Aim: Accurate and reliable quantification of oligonucleotides can be difficult, which has led to an increased focus on bioanalytical methods for more robust analyses. Recent advances toward mitigating sample losses on liquid chromatography (LC) systems have produced recovery advantages for oligonucleotide separations. Results & methodology: LC instruments and columns constructed from MP35N metal alloy and stainless steel columns were compared against LC hardware modified with hybrid inorganic-organic silica surfaces. Designed to minimize metal-analyte adsorption, these surfaces demonstrated a 73% increase in 25-mer phosphorothioate oligonucleotide recovery using ion-pairing reversed-phase LC versus standard LC surfaces, most particularly upon initial use. Conclusion: Hybrid silica chromatographic surfaces improve the performance, detection limits and reproducibility of oligonucleotide bioanalytical assays.

Label-free microRNA detection through analyzing the length distribution pattern of the residual fragments of probe DNA produced during exonuclease III assisted signal amplification by mass spectrometry

Biosensors based on various spectroscopic techniques discriminate the target microRNA (miRNA) from non-target ones with single nucleotide polymorphisms (SNPs) according to the differences in signal intensities which can be caused by other factors besides SNPs. As a result, they are liable to produce false positive results. Herein, we report an attempt to develop a false-positive resistance, sensitive and reliable mass spectrometric platform for miRNA detection. In the proposed platform, the qualitative and quantitative information of the target miRNA was obtained through analyzing mass spectral responses of the multiply charged ions of the residual fragments of the probe DNA produced during exonuclease III assisted signal amplification reaction using an advanced data analysis method. The proposed platform could achieve sensitive and accurate quantitative results for the target miRNA (e.g., miRNA-141) in complex medium with a detection limit of about 1 pM, and unambiguously identify non-target miRNAs with SNPs based on the length distribution patterns of residual fragments of probe DNA. The findings obtained in this study might open an avenue for the design of new miRNA detection methods based on mass spectrometry in combination with various nuclease assisted signal amplification strategies.

BIOANALYSIS AND BIOTRANSFORMATION OF OLIGONUCLEOTIDE THERAPEUTICS BY LIQUID CHROMATOGRAPHY-MASS SPECTROMETRY

Since 2016, eight new oligonucleotide therapies have been approved which has led to increased interest in oligonucleotide analysis. There is a particular need for powerful bioanalytical tools to study the metabolism and biotransformation of these molecules. This review provides the background on the biological basis of these molecules as currently used in therapies. The article also reviews the current state of analytical methodology including state of the art sample preparation techniques, liquid chromatography-mass spectrometry methods, and the current limits of detection/quantitation. Finally, the article summarizes the challenges in oligonucleotide bioanalysis and provides future perspectives for this emerging field. © 2020 John Wiley & Sons Ltd.

A label-free mass spectrometry detection of microRNA by signal switching from high-molecular-weight polynucleotides to highly sensitive small molecules

MicroRNAs (miRNAs) are associated with various cellular processes and have been recognized as potential biomarkers for many human diseases. The sensitive and accurate determination of miRNA expression levels in biological specimens is highly significant for understanding their biological functions and clinical diagnosis. Mass spectrometry (MS) has shown its potential to study bioactive molecules, however, direct MS analysis of miRNAs is often hampered by limited sensitivity. For sensitive detection of miRNAs, indirect methods are generally employed through the use of DNA probes labeled with peptides or metal elements. In this work, we proposed a novel MS-based label-free strategy for miRNA quantification. A dual-amplification system was developed by using a padlock probe containing the poly(thymine) sequence in combination with rolling circle amplification (RCA). The specific recognition of target miRNA by the padlock probes produced long single-stranded DNAs containing poly (adenine) segments, which guaranteed the specificity of detection and realized primary amplification. Then the RCA products were extracted and treated with acid to release a large number of free adenines as reporter molecules for secondary signal amplification. Overall, the quantification of target miRNA was carried out by signal switching from high-molecular-weight RCA products to highly sensitive small molecule of adenine. The developed method achieved a linear detection range from 200 amol to 100 fmol for miRNA-21 with a limit of detection of 50 amol, and successfully applied to detect endogenous miRNA-21 levels from lung cancer cells. Overall, the present study provides a sensitive, specific MS-based method for miRNA detection and holds great potential for further application of MS technology to detect other biomarkers in biomedical research and early clinical diagnosis.

Hybridization Liquid Chromatography-Tandem Mass Spectrometry: An Alternative Bioanalytical Method for Antisense Oligonucleotide Quantitation in Plasma and Tissue Samples

Quantitative bioanalysis in plasma and tissues samples is required to study the pharmacokinetic and pharmacodynamic properties of antisense oligonucleotides (ASOs). To overcome intrinsic drawbacks in specificity, sensitivity, and throughput of traditional ligand-binding assay (LBA) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods, an alternative bioanalytical method was developed by combining oligonucleotide hybridization and LC-MS/MS technologies. Target ASOs were extracted from biological samples by hybridization with biotinylated sense-strand oligonucleotides coupled to streptavidin magnetic beads. Using ion-pairing chromatography and tandem mass spectrometry, this method demonstrated high sensitivity (0.5 ng/mL using 100 μL of plasma), high specificity, wide linear range, complete automation, and generic applications in tests with multiple ASOs. The typical challenge of sensitivity drop in traditional ion-pairing LC-MS/MS was for the first time overcome by the introduction of a ternary pump system. Due to the high specificity, quantitation in various biological matrixes was achieved using calibration standards in plasma, largely improving efficiency and consistency. Another major advantage was the capability of simultaneous quantitation of ASO metabolites. The hybridization LC-MS/MS was considered an improved alternative for quantitation of ASOs and metabolites in plasma and tissue samples, showing a great potential to replace traditional LBA and LC-MS/MS methods.

Modeling cationic adduction of oligonucleotides using electrospray desorption ionization

RATIONALE

Cationic adduction causes poor sensitivity and increases spectral complexity during mass spectral analysis of oligonucleotides and alkylamines are used to reduce this adduction. It is unclear the effect of the physiochemical properties of the alkylamines on the reduction of the cationic adduction.

METHODS

All samples were directly infused into a Synapt G2 HDMS quadrupole time-of-flight (TOF) hybrid mass spectrometer in negative ion electrospray ionization mode through the native built-in fluidics system. The infusion flow rate was set to 50 μL/min. The TOFMS tuning parameters were as follows: capillary voltage -2.0 kV, cone voltage 25 V, extraction cone voltage 2 V, source temperature 125°C, desolvation temperature 450°C, cone gas flow rate 0 L/h, and desolvation gas (nitrogen) flow rate 1000 L/h.

RESULTS

A quantitative model was created to predict the optimized alkylamine for MS analysis, while a qualitative model was generated to explain the most important physiochemical properties: proton affinity (13.83%), gas-phase basicity (11.79%), pKa (11.47%), boiling point (10.73%), MW (10.3%), Henry's Law Constant (9.56%), and partition coefficient (logP) (9.44%). The quantitative model was applied to RNA (microRNA) and a phosphorothioate and predicts the trend of cationic adduction.

CONCLUSIONS

Two models are described to understand the physiochemical properties that contribute to the adduction and to provide users a quick mathematical tool to predict the best choice of alkylamine to lower cationic adduction and decrease spectral complexity while enhancing sensitivity.

LC-MS quantification of oligonucleotides in biological matrices with SPE or hybridization extraction

Aim: Quantitative LC-MS analysis of oligonucleotides (OGNs) in biological matrices is needed to support candidate selection of new therapeutic OGNs. Methodology & results: A set of 20 single stranded antisense oligonucleotides (ASO) and five siRNAs were extracted from plasma and tissue homogenates. Anion Exchange (AEX) SPE was selected as generic extraction approach, resulting in recoveries from plasma >70%. Extraction from tissue homogenates showed often more variation and lower recoveries. A proof of concept of a novel tailored hybridization extraction is demonstrated for two 16-mer reference OGNs. Conclusion: Two methods for extraction of OGNs were investigated and applied for quantitative analysis. The AEX-SPE is considered a more generic approach preferred when multiple compounds are evaluated. Hybridization extraction has great potential but critical reagents per analyte are needed.

MicroRNA targeting by quercetin in cancer treatment and chemoprotection

A growing number of evidences from clinical and preclinical studies have shown that dysregulation of microRNA (miRNA) function contributes to the progression of cancer and thus miRNA can be an effective target in therapy. Dietary phytochemicals, such as quercetin, are natural products that have potential anti-cancer properties due to their proven antioxidant, anti-inflammatory, and anti-proliferative effects. Available experimental studies indicate that quercetin could modulate multiple cancer-relevant miRNAs including let-7, miR-21, miR-146a and miR-155, thereby inhibiting cancer initiation and development. This paper reviews the data supporting the use of quercetin for miRNA-mediated chemopreventive and therapeutic strategies in various cancers, with the aim to comprehensively understand its health-promoting benefits and pharmacological potential. Integration of technology platforms for miRNAs biomarker and drug discovery is also presented.