In-depth analysis of monoclonal antibodies using microfluidic capillary electrophoresis and native mass spectrometry

Lab-on-a-chip: an advanced technology for the modernization of traditional Chinese medicine

Benefiting from the complex system composed of various constituents, medicament portions, species, and places of origin, traditional Chinese medicine (TCM) possesses numerous customizable and adaptable efficacies in clinical practice guided by its theories. However, these unique features are also present challenges in areas such as quality control, screening active ingredients, studying cell and organ pharmacology, and characterizing the compatibility between different Chinese medicines. Drawing inspiration from the holistic concept, an integrated strategy and pattern more aligned with TCM research emerges, necessitating the integration of novel technology into TCM modernization. The microfluidic chip serves as a powerful platform for integrating technologies in chemistry, biology, and biophysics. Microfluidics has given rise to innovative patterns like lab-on-a-chip and organoids-on-a-chip, effectively challenging the conventional research paradigms of TCM. This review provides a systematic summary of the nature and advanced utilization of microfluidic chips in TCM, focusing on quality control, active ingredient screening/separation, pharmaceutical analysis, and pharmacological/toxicological assays. Drawing on these remarkable references, the challenges, opportunities, and future trends of microfluidic chips in TCM are also comprehensively discussed, providing valuable insights into the development of TCM.

Characterization of Therapeutic Antibody Charge Heterogeneity Under Stress Conditions by Microfluidic Capillary Electrophoresis Coupled with Mass Spectrometry

Therapeutic antibodies are a major class of biopharmaceutics that are applied in disease treatment because of their many advantages, including high specificity and high affinity to molecular targets. Between their production and administration, therapeutic antibodies are exposed to multiple stress conditions. Forced degradation and stress stability studies are conducted to simulate the risk of degradation and the effects of these stresses, thereby enhancing understanding of the drug product to support strategies to mitigate the impact from stressed conditions. These types of studies are also routinely conducted to evaluate product comparability when major process changes are implemented during the production. Charge variant analysis helps understand the changes in the electrostatic environment of biotherapeutics and can uncover underlying molecular level alterations associated with charge variants. Herein, we used ZipChip native capillary electrophoresis-mass spectrometry (nCE-MS) to elucidate the changes in charge variant profiles at the molecular level. In two case studies under thermal stress conditions, we observed that charge variants arose from both post-translational modifications (including deamidation, oxidation, and pyroglutamate formation) and sequence truncations at the hinge regions. Under oxidative stress conditions, oxidation was found to be the major contributor to the changes in the charge variant profiles. Under pH stress conditions, the changes in the charge variant profile were due to increased levels of deamidation, oxidation, and pyroglutamate formation. ZipChip nCE-MS analysis enables identification of charge variant species under various stress conditions, thus supporting process and formulation development of biotherapeutics.

Research of saccharides and related biocomplexes: A review with recent techniques and applications

Saccharides and biocompounds as saccharide (sugar) complexes have various roles and biological functions in living organisms due to modifications via nucleophilic substitution, polymerization, and complex formation reactions. Mostly, mono-, di-, oligo-, and polysaccharides are stabilized to inactive glycosides, which are formed in metabolic pathways. Natural saccharides are important in food and environmental monitoring. Glycosides with various functionalities are significant in clinical and medical research. Saccharides are often studied with the chromatographic methods of hydrophilic interaction liquid chromatography and anion exchange chromatograpy, but also with capillary electrophoresis and mass spectrometry with their on-line coupling systems. Sample preparation is important in the identification of saccharide compounds. The cases discussed here focus on bioscience, clinical, and food applications.

Antibodies, repertoires and microdevices in antibody discovery and characterization

Therapeutic antibodies are paramount in treating a wide range of diseases, particularly in auto-immunity, inflammation and cancer, and novel antibody candidates recognizing a vast array of novel antigens are needed to expand the usefulness and applications of these powerful molecules. Microdevices play an essential role in this challenging endeavor at various stages since many general requirements of the overall process overlap nicely with the general advantages of microfluidics. Therefore, microfluidic devices are rapidly taking over various steps in the process of new candidate isolation, such as antibody characterization and discovery workflows. Such technologies can allow for vast improvements in time-lines and incorporate conservative antibody stability and characterization assays, but most prominently screenings and functional characterization within integrated workflows due to high throughput and standardized workflows. First, we aim to provide an overview of the challenges of developing new therapeutic candidates, their repertoires and requirements. Afterward, this review focuses on the discovery of antibodies using microfluidic systems, technological aspects of micro devices and small-scale antibody protein characterization and selection, as well as their integration and implementation into antibody discovery workflows. We close with future developments in microfluidic detection and antibody isolation principles and the field in general.

Capillary electrophoresis-mass spectrometry for protein analyses under native conditions: Current progress and perspectives

Native mass spectrometry is a rapidly emerging technique for fast and sensitive structural analysis of protein constructs, maintaining the protein higher order structure. The coupling with electromigration separation techniques under native conditions enables the characterization of proteoforms and highly complex protein mixtures. In this review, we present an overview of current native CE-MS technology. First, the status of native separation conditions is described for capillary zone electrophoresis (CZE), affinity capillary electrophoresis (ACE), and capillary isoelectric focusing (CIEF), as well as their chip-based formats, including essential parameters such as electrolyte composition and capillary coatings. Further, conditions required for native ESI-MS of (large) protein constructs, including instrumental parameters of QTOF and Orbitrap systems, as well as requirements for native CE-MS interfacing are presented. On this basis, methods and applications of the different modes of native CE-MS are summarized and discussed in the context of biological, medical, and biopharmaceutical questions. Finally, key achievements are highlighted and concluded, while remaining challenges are pointed out.

Voltammetric studies and spectroscopic investigations of the interaction of an anticancer drug bevacizumab-DNA and analytical applications of disposable pencil graphite sensor

A sensitive, simple, fast electrochemical biosensor for the DNA interaction of bevacizumab (BEVA), which is used as a targeted drug in cancer treatment, was developed using the differential pulse voltammetry (DPV) technique with pencil graphite electrode (PGE). In the work, PGE was electrochemically activated in a supporting electrolyte medium of +1.4 V/60 s (PBS pH 3.0). Surface characterization of PGE was carried out by SEM, EDX, EIS, and CV techniques. Determination and electrochemical properties of BEVA were examined with CV and DPV techniques. BEVA gave a distinct analytical signal on the PGE surface at a potential of +0.90 V (vs. Ag/AgCl). In the procedure proposed in this study, BEVA gave a linear response on PGE in PBS (pH 3.0 containing 0.02 M NaCl) (0.1 mg mL-1 - 0.7 mg mL-1) with LOD and LOQ values of 0.026 mg mL-1 and 0.086 μg mL-1, respectively. BEVA was reacted with 20 μg mL-1 DNA in PBS for 150 s and analytical peak signals for adenine and guanine bases were evaluated. The interaction between BEVA-DNA was supported by UV-Vis. Absorption spectrometry and the binding constant was determined as 7.3 × 104.

Recent advances in structural mass spectrometry methods in the context of biosimilarity assessment: from sequence heterogeneities to higher order structures

Biotherapeutics and their biosimilar versions have been flourishing in the biopharmaceutical market for several years. Structural and functional characterization is needed to achieve analytical biosimilarity through the assessment of critical quality attributes as required by regulatory authorities. The role of analytical strategies, particularly mass spectrometry-based methods, is pivotal to gathering valuable information for the in-depth characterization of biotherapeutics and biosimilarity assessment. Structural mass spectrometry methods (native MS, HDX-MS, top-down MS, etc.) provide information ranging from primary sequence assessment to higher order structure evaluation. This review focuses on recent developments and applications in structural mass spectrometry for biotherapeutic and biosimilar characterization.

Rapid Intact Mass Analysis and Evaluation of the Separation Potential of Microfluidic Capillary Electrophoresis Mass Spectrometry for Oligonucleotides

Oligonucleotide characterization is a rapidly advancing field in the biopharmaceutical industry. Understanding critical quality attributes, such as intact mass and impurities, requires a toolbox of analytical techniques, which commonly includes liquid chromatography-mass spectrometry (LC-MS). Oligonucleotide LC-MS analysis frequently requires sample run times upward of 15 min to achieve separation of multiple oligonucleotide species. Additionally, LC methods frequently employ mobile phase additives such as triethylamine and 1,1,1,3,3,3-hexafluoro-2-propanol that are not always desired for use in MS instrumentation. Here, microfluidic capillary electrophoresis mass spectrometry (CE-MS) via ZipChip technology was employed to enable rapid intact mass analysis of oligonucleotide single strands. Baseline separation of equal length oligonucleotides was achieved in less than 4 min. Additionally, the potential of the ZipChip platform for separation of oligonucleotide full-length products (FLPs) and their impurities was evaluated.

Exploring proteoforms of the IgG2 monoclonal antibody panitumumab using microchip capillary electrophoresis-mass spectrometry

The IgG2 type monoclonal antibody panitumumab is an anti-epidermal growth factor receptor (EGFR) drug used for the treatment of EGFR-expressing, chemotherapy resistant, metastatic colorectal carcinoma. In this study, panitumumab drug product was first analysed using size exclusion chromatography coupled to mass spectrometry for rapid identity testing. The experimental data led to the identification of two panitumumab isoforms with several prominent forms remaining unidentified, despite apparently low sample complexity. Microchip capillary electrophoresis-mass spectrometry (CE-MS) was subsequently utilised for a more detailed characterization. It was observed that panitumumab is subject to partial N-terminal pyroglutamate formation. Incomplete conversion is uncharacteristic for N-terminally exposed glutamines and in case of panitumumab gives rise to forms which show successive mass offsets of 17 Da, respectively. If not separated before mass spectrometric analysis, e.g. by capillary electrophoresis, such near isobaric species coalesce into single MS peaks, which subsequently hampers or prevents their assignment. With a total of 42 panitumumab isoforms assigned by CE-MS, these observations highlight a potential pitfall of commonly applied rapid identity testing workflows and demonstrate that even low complexity biopharmaceuticals can require separation strategies which offer high separation selectivity for species close in mass.

Development of a High-Field "Brick" Mass Spectrometer with Extended Mass Range and Capable of Characterizing Native Proteins

One of the main challenges of analyzing intact proteins on an ion trap mass spectrometer is the mass range limitation, especially for miniature mass spectrometers. In this study, a high-field frequency scanning ion trap miniature mass spectrometer, namely the high-field "Brick" mass spectrometer, was developed to analyze intact proteins. A high-voltage broadband radio frequency (rf) amplifier was designed with a maximum output of 900 Vp-p over a frequency range of 130-700 kHz. Compared to the 600 Vp-p rf amplifier equipped in the conventional "Brick" mass spectrometer, the mass range of the instrument could be extended from 2000 to over 8000 Th. Sensitivity and mass resolution for native protein analyses were also evaluated and compared. Various proteins as well as their mixtures were analyzed on the high-field "Brick" mass spectrometer. The noncovalent interaction between protein-ligand complexes, lysozyme with triN-acetylchitotriose, was also analyzed. In addition, a hybrid ion scan mode was explored to further expand the mass range of the instrument at both low- and high-mass ends. In the hybrid ion scan mode, both rf frequency and amplitude were tuned, and a mass range from 100 to 12,000 Th was realized. As a result, both small drugs and proteins could be analyzed in a single mass scan. As proof-of-concept demonstrations, a mixture of atenolol and bovine serum albuminand oligomers of transferrin were analyzed.

In-depth size and charge variants characterization of monoclonal antibody with native mass spectrometry

Although the reversed-phase liquid chromatography (RPLC) is the most used separation front for mass spectrometry, many other separation modes are critical for enabling characterization of the protein therapeutics. Specifically, chromatographic separations under native conditions, such as those based on size exclusion chromatography (SEC) and ion-exchange chromatography (IEX), are used for characterizing important biophysical properties of protein variants in drug substance and drug product. Because most native state separation modes use non-volatile buffers with high salt concentration, optical detection has been traditionally used. However, there is an increasing need to understand and identify the optical underlying peaks by mass spectrometry for structure elucidation. For size variant separation by SEC, the native MS helps to understand the nature of the high molecular weight species, as well as clipping sites for low molecular weight fragments. For charge variant separation by IEX, native MS can reveal the post-translational modifications or other important factors contributing to charge heterogeneity at the intact level. Here, we demonstrate the power of native MS by direct coupling of SEC and IEX eluent to a time-of-flight mass spectrometer to characterize bevacizumab and NISTmAb. Our studies exemplify the effectiveness of native SEC-MS for characterizing bevacizumab's high molecular weight species at less than 0.3% (based on SEC/UV peak area%) and analyzing the fragment pathway with single amino acid difference for its low molecular weight species at less than 0.05%. Good IEX charge variant separation was obtained with consistent UV and MS profiles. The identity of separated acidic and basic variants were elucidated by native MS at intact level. We successfully differentiated several charge variants including glycoform variants that have not been reported before. In addition, native MS allowed identification of higher molecular weight species as late eluted variants. Overall, the SEC and IEX separation combined with high resolution and high sensitivity native MS, which is significantly different from the traditional RPLC-MS workflows, can be an effective tool that offers valuable insights for us to understand protein therapeutics at native state.

High-throughput capillary electrophoresis analysis of biopharmaceuticals utilizing sequential injections

The complexity of biotherapeutic products implies an ever-increasing list of product quality attributes that need to be monitored and characterized. In addition, the growing interest in implementing process analytical technology in biopharmaceutical production has further increased the testing burden, together with the need for rapid testing that can facilitate real-time or near-real-time decision-making. Capillary electrophoresis (CE) has made a place in biopharmaceutical analysis but is regarded as a low-throughput method, with the instrument dead time constituting more than 80% of the total time of analysis. In this study, the dead time of CE was utilized to analyse 3 mAb samples in a single-CE run. This approach resulted in an up to 77% reduction in the total analysis time and increased the productivity by up to 300%, compared to traditional single CE-ultraviolet runs, without compromising resolution or relative peak areas. Additionally, good method reproducibility was observed. The compatibility of the method has been demonstrated with protein A eluate and cation exchange chromatography fractions. We, thus, propose that sequential injections can be applied for fast and robust CE analysis of biopharmaceuticals.

Analytical Techniques for the Characterization and Quantification of Monoclonal Antibodies

Monoclonal antibodies (mAbs) are a fast-growing class of biopharmaceuticals. They are widely used in the identification and detection of cell makers, serum analytes, and pathogenic agents, and are remarkably used for the cure of autoimmune diseases, infectious diseases, or malignancies. The successful application of therapeutic mAbs is based on their ability to precisely interact with their appropriate target sites. The precision of mAbs rely on the isolation techniques delivering pure, consistent, stable, and safe lots that can be used for analytical, diagnostic, or therapeutic applications. During the creation of a biologic, the key quality features of a particular mAb, such as structure, post-translational modifications, and activities at the biomolecular and cellular levels, must be characterized and profiled in great detail. This implies the requirement of powerful state of the art analytical techniques for quality control and characterization of mAbs. Until now, various analytical techniques have been developed to characterize and quantify the mAbs according to the regulatory guidelines. The present review summarizes the major techniques used for the analyses of mAbs which include chromatographic, electrophoretic, spectroscopic, and electrochemical methods in addition to the modifications in these methods for improving the quality of mAbs. This compilation of major analytical techniques will help students and researchers to have an overview of the methodologies employed by the biopharmaceutical industry for structural characterization of mAbs for eventual release of therapeutics in the drug market.

Concepts and recent advances in microchip electrophoresis coupled to mass spectrometry: Technologies and applications

The online coupling of microchip electrophoresis (ME) as a fast, highly efficient, and low-cost miniaturized separation technique to mass spectrometry (MS) as an information-rich and sensitive characterization technique results in ME-MS an attractive tool for various applications. In this paper, we review the basic concepts and latest advances in technology for ME coupled to MS during the period of 2016-2021, covering microchip materials, structures, fabrication techniques, and interfacing to electrospray ionization (ESI)-MS and matrix-assisted laser desorption/ionization-MS. Two critical issues in coupling ME and ESI-MS include the electrical connection used to define the electrophoretic field strength along the separation channel and the generation of the electrospray for MS detection, as well as, a miniaturized ESI-tip. The recent commercialization of ME-MS in zone electrophoresis and isoelectric focusing modes has led to the widespread application of these techniques in academia and industry. Here we summarize recent applications of ME-MS for the separation and detection of antibodies, proteins, peptides, carbohydrates, metabolites, and so on. Throughout the paper these applications are discussed in the context of benefits and limitations of ME-MS in comparison to alternative techniques.

Microchip electrophoresis separation coupled to mass spectrometry (MCE-MS) for the rapid monitoring of multiple quality attributes of monoclonal antibodies

Therapeutic monoclonal antibodies (mAbs) are highly heterogeneous as a result of posttranslational modifications (PTMs) during bioprocessing and storage. The modifications that impact mAb product quality are regarded as critical quality attributes and require monitoring. The conventional LC-mass spectrometer (MS) method used for product quality monitoring may require protein A purification prior to analysis. In this paper, we present a high-throughput microchip electrophoresis (<4 min) in-line with MS (MCE-MS) that enables baseline separation and characterization of Fc, Fd', and light chain (LC) domains of IdeS-treated mAb sample directly from bioreactor. The NISTmAb was used to optimize the MCE separation and to assess its capability of multiple attribute monitoring. The MCE-MS can uniquely separate and characterize deamidated species at domain level compared to LC-MS method. Two case studies were followed to demonstrate the method capability of monitoring product quality of mAb samples from stability studies or directly from bioreactors.

Structural and Functional Analysis of CEX Fractions Collected from a Novel Avastin® Biosimilar Candidate and Its Innovator: A Comparative Study

Avastin^® is a humanized recombinant monoclonal antibody used to treat cancer by targeting VEGF-A to inhibit angiogenesis. SIMAB054, an Avastin^® biosimilar candidate developed in this study, showed a different charge variant profile than its innovator. Thus, it is fractionated into acidic, main, and basic isoforms and collected physically by Cation Exchange Chromatography (CEX) for a comprehensive structural and functional analysis. The innovator product, fractionated into the same species and collected by the same method, is used as a reference for comparative analysis. Ultra-Performance Liquid Chromatography (UPLC) ESI-QToF was used to analyze the modifications leading to charge heterogeneities at intact protein and peptide levels. The C-terminal lysine clipping and glycosylation profiles of the samples were monitored by intact mAb analysis. The post-translational modifications, including oxidation, deamidation, and N-terminal pyroglutamic acid formation, were determined by peptide mapping analysis in the selected signal peptides. The relative binding affinities of the fractionated charge isoforms against the antigen, VEGF-A, and the neonatal receptor, FcRn, were revealed by Surface Plasmon Resonance (SPR) studies. The results show that all CEX fractions from the innovator product and the SIMAB054 shared the same structural variants, albeit in different ratios. Common glycoforms and post-translational modifications were the same, but at different percentages for some samples. The dissimilarities were mostly originating from the presence of extra C-term Lysin residues, which are prone to enzymatic degradation in the body, and thus they were previously assessed as clinically irrelevant. Another critical finding was the presence of different glyco proteoforms in different charge species, such as increased galactosylation in the acidic and afucosylation in the basic species. SPR characterization of the isolated charge variants further confirmed that basic species found in the CEX analyses of the biosimilar candidate were also present in the innovator product, although at lower amounts. The charge variants’ in vitro antigen- and neonatal receptor-binding activities varied amongst the samples, which could be further investigated in vivo with a larger sample set to reveal the impact on the pharmacokinetics of drug candidates. Minor structural differences may explain antigen-binding differences in the isolated charge variants, which is a key parameter in a comparability exercise. Consequently, such a biosimilar candidate may not comply with high regulatory standards unless the binding differences observed are justified and demonstrated not to have any clinical impact.

Analytical Similarity Assessment of Biosimilars: Global Regulatory Landscape, Recent Studies and Major Advancements in Orthogonal Platforms

Biopharmaceuticals are one of the fastest-growing sectors in the biotechnology industry. Within the umbrella of biopharmaceuticals, the biosimilar segment is expanding with currently over 200 approved biosimilars, globally. The key step towards achieving a successful biosimilar approval is to establish analytical and clinical biosimilarity with the innovator. The objective of an analytical biosimilarity study is to demonstrate a highly similar profile with respect to variations in critical quality attributes (CQAs) of the biosimilar product, and these variations must lie within the range set by the innovator. This comprises a detailed comparative structural and functional characterization using appropriate, validated analytical methods to fingerprint the molecule and helps reduce the economic burden towards regulatory requirement of extensive preclinical/clinical similarity data, thus making biotechnological drugs more affordable. In the last decade, biosimilar manufacturing and associated regulations have become more established, leading to numerous approvals. Biosimilarity assessment exercises conducted towards approval are also published more frequently in the public domain. Consequently, some technical advancements in analytical sciences have also percolated to applications in analytical biosimilarity assessment. Keeping this in mind, this review aims at providing a holistic view of progresses in biosimilar analysis and approval. In this review, we have summarized the major developments in the global regulatory landscape with respect to biosimilar approvals and also catalogued biosimilarity assessment studies for recombinant DNA products available in the public domain. We have also covered recent advancements in analytical methods, orthogonal techniques, and platforms for biosimilar characterization, since 2015. The review specifically aims to serve as a comprehensive catalog for published biosimilarity assessment studies with details on analytical platform used and critical quality attributes (CQAs) covered for multiple biotherapeutic products. Through this compilation, the emergent evolution of techniques with respect to each CQA has also been charted and discussed. Lastly, the information resource of published biosimilarity assessment studies, created during literature search is anticipated to serve as a helpful reference for biopharmaceutical scientists and biosimilar developers.

An improved capillary isoelectric focusing-mass spectrometry method for high-resolution characterization of monoclonal antibody charge variants

Routine and high-resolution characterization of monoclonal antibody (mAb) charge variants is vital for controlling mAb quality as therapeutics. Capillary isoelectric focusing-mass spectrometry (cIEF-MS) has emerged as a powerful tool for characterizing mAb charge variants because it can achieve high-resolution separation and highly sensitive detection of proteins. It provides much better identification of charge variants than the traditionally used cIEF-UV method. However, further improvement of cIEF-MS regarding stability and separation resolution is needed. Here, we improved the stability and enhanced separation resolution of automated cIEF-MS by bettering the quality of capillary neutral coating, reducing catholyte pH to 10 for cIEF-MS for the first time, and systematically optimizing the cIEF separation conditions. The improved cIEF-MS method was applied to characterize charge variants of three previously well characterized mAbs (NISTmAb, cetuximab, trastuzumab) and one tool mAb (mAb1). The charge variants of the studied mAbs were well resolved, and the majority of post-translational modifications (PTMs) found in those mAbs agreed with the literature. cIEF-MS analyses of mAb1 were capable of discovering ten charge variants with various interesting PTMs, such as PGK amidation, incomplete C-terminal lysine clipping, glycosylation, and deamination. cIEF-MS was successfully used for accurately determining the isoelectric points (pIs) of mAb1 charge variants via analyzing the pI markers and spiking in a standard protein (cytochrome c) to samples for migration time normalization, which is beneficial for evaluating pI-related pharmacokinetic properties. Our cIEF-MS agreed with and, in some cases (i.e., cetuximab and mAb1), outperformed cIEF-UV for detecting mAb charge variants.

Rapid Analysis of Biotherapeutics Using Protein A Chromatography Coupled to Orbitrap Mass Spectrometry

Monoclonal antibodies (mAbs) and related products undergo a wide range of modifications, many of which can often be directly associated to culture conditions during upstream processing. Ideally, such conditions should be monitored and fine-tuned based on real-time or close to real-time information obtained by the assessment of the product quality attribute (PQA) profile of the biopharmaceutical produced, which is the fundamental idea of process analytical technology. Therefore, methods that are simple, quick and robust, but sufficiently powerful, to allow for the generation of a comprehensive picture of the PQA profile of the protein of interest are required. A major obstacle for the analysis of proteins directly from cultures is the presence of impurities such as cell debris, host cell DNA, proteins and small-molecule compounds, which usually requires a series of capture and polishing steps using affinity and ion-exchange chromatography before characterization can be attempted. In the current study, we demonstrate direct coupling of protein A affinity chromatography with native mass spectrometry (ProA-MS) for development of a robust method that can be used to generate information on the PQA profile of mAbs and related products in as little as 5 min. The developed method was applied to several samples ranging in complexity and stability, such as simple and more complex monoclonal antibodies, as well as cysteine-conjugated antibody–drug conjugate mimics. Moreover, the method demonstrated suitability for the analysis of protein amounts of <1 μg, which suggests applicability during early-stage development activities.

Faster, better, and cheaper: harnessing microfluidics and mass spectrometry for biotechnology

High-throughput screening technologies are widely used for elucidating biological activities. These typically require trade-offs in assay specificity and sensitivity to achieve higher throughput. Microfluidic approaches enable rapid manipulation of small volumes and have found a wide range of applications in biotechnology providing improved control of reaction conditions, faster assays, and reduced reagent consumption. The integration of mass spectrometry with microfluidics has the potential to create high-throughput, sensitivity, and specificity assays. This review introduces the widely-used mass spectrometry ionization techniques that have been successfully integrated with microfluidics approaches such as continuous-flow system, microchip electrophoresis, droplet microfluidics, digital microfluidics, centrifugal microfluidics, and paper microfluidics. In addition, we discuss recent applications of microfluidics integrated with mass spectrometry in single-cell analysis, compound screening, and the study of microorganisms. Lastly, we provide future outlooks towards online coupling, improving the sensitivity and integration of multi-omics into a single platform.

Immunoaffinity Capillary Electrophoresis in the Era of Proteoforms, Liquid Biopsy and Preventive Medicine: A Potential Impact in the Diagnosis and Monitoring of Disease Progression

Over the years, multiple biomarkers have been used to aid in disease screening, diagnosis, prognosis, and response to therapy. As of late, protein biomarkers are gaining strength in their role for early disease diagnosis and prognosis in part due to the advancements in identification and characterization of a distinct functional pool of proteins known as proteoforms. Proteoforms are defined as all of the different molecular forms of a protein derived from a single gene caused by genetic variations, alternative spliced RNA transcripts and post-translational modifications. Monitoring the structural changes of each proteoform of a particular protein is essential to elucidate the complex molecular mechanisms that guide the course of disease. Clinical proteomics therefore holds the potential to offer further insight into disease pathology, progression, and prevention. Nevertheless, more technologically advanced diagnostic methods are needed to improve the reliability and clinical applicability of proteomics in preventive medicine. In this manuscript, we review the use of immunoaffinity capillary electrophoresis (IACE) as an emerging powerful diagnostic tool to isolate, separate, detect and characterize proteoform biomarkers obtained from liquid biopsy. IACE is an affinity capture-separation technology capable of isolating, concentrating and analyzing a wide range of biomarkers present in biological fluids. Isolation and concentration of target analytes is accomplished through binding to one or more biorecognition affinity ligands immobilized to a solid support, while separation and analysis are achieved by high-resolution capillary electrophoresis (CE) coupled to one or more detectors. IACE has the potential to generate rapid results with significant accuracy, leading to reliability and reproducibility in diagnosing and monitoring disease. Additionally, IACE has the capability of monitoring the efficacy of therapeutic agents by quantifying companion and complementary protein biomarkers. With advancements in telemedicine and artificial intelligence, the implementation of proteoform biomarker detection and analysis may significantly improve our capacity to identify medical conditions early and intervene in ways that improve health outcomes for individuals and populations.

Development of a miniature protein mass spectrometer capable of analyzing native proteins

Current miniature mass spectrometers were usually designed for the detection of small and medium size molecules, including volatile (semi-volatile) compounds, drugs and lipids. In this study, a miniature protein mass spectrometer was developed in this work, which could serve as a biosensor for the rapid identification of proteins as well as their conformations. A linear ion trap with a field radius of 2.5 mm was designed to extend mass range of the instrument to over 6500 Th. Mass resolution and sensitivity of the instrument were also optimized for protein ions by increasing the buffer gas pressure and using a high-gain Faraday detector. It is then demonstrated that the mass spectra of native proteins, such as IgG1, could be acquired by coupling the instrument with a soft electrospray ionization source. As a proof-of-concept demonstration, results suggest that the current instrument could be used to identify target proteins and probe/distinguish their conformations in solutions.

Applications of capillary electrophoresis for biopharmaceutical product characterization

Capillary electrophoresis (CE), after being introduced several decades ago, has carved out a niche for itself in the field of analytical characterization of biopharmaceutical products. It does not only offer fast separation, high resolution in miniaturized format, but equally importantly represents an orthogonal separation mechanism to high-performance liquid chromatography. Therefore, it is not surprising that CE-based methods can be found in all major pharmacopoeias and are recommended for the analysis of biopharmaceutical products during process development, characterization, quality control, and release testing. Different separation formats of CE, such as capillary gel electrophoresis, capillary isoelectric focusing, and capillary zone electrophoresis are widely used for size and charge heterogeneity characterization as well as purity and stability testing of therapeutic proteins. Hyphenation of CE with MS is emerging as a promising bioanalytical tool to assess the primary structure of therapeutic proteins along with any impurities. In this review, we confer the latest developments in capillary electrophoresis, used for the characterization of critical quality attributes of biopharmaceutical products covering the past 6 years (2015-2021). Monoclonal antibodies, due to their significant share in the market, have been given prioritized coverage.

Recent biopharmaceutical applications of capillary electrophoresis methods on recombinant DNA technology-based products

Biopharmaceuticals (recombinant technology-based products, vaccines, whole blood and blood components, gene therapy, cells, tissues, etc.,) are described as biological medical products produced from various living sources such as human, microbial, animal, and so on by manufacturing, extraction, or semi-synthesis. They are complex molecules having high molecular weights. For their safety and efficacy, their structural, clinical, physicochemical, and chemical features must be carefully controlled, and they must be well characterized by analytical techniques before the approval of the final product. Capillary electrophoresis (CE) having versatile modes can provide valuable safety and efficacy information, such as amino acid sequence, size variants (low and high molecular weight variants), charged variants (acidic and basic impurities), aggregates, N-linked glycosylation, and O-linked glycosylation. There are numerous applications of CE in the literature. In this review, the most significant and recent studies on the analysis of recombinant DNA technology-based products using different CE modes in the last ten years have been overviewed. It was seen that the researches mostly focus on the analysis of mAbs and IgG. In addition, in recent years, researchers have started to prefer CE combined mass spectrometry (MS) techniques to provide a more detailed characterization for protein and peptide fragments.

Filamentous Bacteriophage-A Powerful Carrier for Glioma Therapy

Glioma is a life-threatening malignant tumor. Resistance to traditional treatments and tumor recurrence present major challenges in treating and managing this disease, consequently, new therapeutic strategies must be developed. Crossing the blood-brain barrier (BBB) is another challenge for most drug vectors and therapy medications. Filamentous bacteriophage can enter the brain across the BBB. Compared to traditional drug vectors, phage-based drugs offer thermodynamic stability, biocompatibility, homogeneity, high carrying capacity, self-assembly, scalability, and low toxicity. Tumor-targeting peptides from phage library and phages displaying targeting peptides are ideal drug delivery agents. This review summarized recent studies on phage-based glioma therapy and shed light on the developing therapeutics phage in the personalized treatment of glioma.

Hitting the sweet spot with capillary electrophoresis: advances in N-glycomics and glycoproteomics

N-glycosylation is of paramount importance for understanding the mechanisms of various human diseases and ensuring the safety and efficacy of biotherapeutics. Traditional glycan analysis techniques include LC-based separations and MALDI-TOF-MS identification. However, the current state-of-the-art methods lack throughput and structural information, include laborious sample preparation procedures and require large sample volumes. Capillary electrophoresis (CE) has long been used for the screening and reliable quantitation of glycans, but its applications have been limited. Because of its speed, sensitivity and complementarity with standard glycan analysis techniques, CE is currently emerging as one of the most versatile and adaptable methods for glycan analysis in both academia and industry. Herein, we review the latest advancements in CE-based applications to glycomics and glycoproteomics within both the biopharmaceutical and clinical sectors.

High-Resolution Native Mass Spectrometry

Native mass spectrometry (MS) involves the analysis and characterization of macromolecules, predominantly intact proteins and protein complexes, whereby as much as possible the native structural features of the analytes are retained. As such, native MS enables the study of secondary, tertiary, and even quaternary structure of proteins and other biomolecules. Native MS represents a relatively recent addition to the analytical toolbox of mass spectrometry and has over the past decade experienced immense growth, especially in enhancing sensitivity and resolving power but also in ease of use. With the advent of dedicated mass analyzers, sample preparation and separation approaches, targeted fragmentation techniques, and software solutions, the number of practitioners and novel applications has risen in both academia and industry. This review focuses on recent developments, particularly in high-resolution native MS, describing applications in the structural analysis of protein assemblies, proteoform profiling of—among others—biopharmaceuticals and plasma proteins, and quantitative and qualitative analysis of protein–ligand interactions, with the latter covering lipid, drug, and carbohydrate molecules, to name a few.

Chip-Based Capillary Zone Electrophoresis Mass Spectrometry for Rapid Resolution and Quantitation of Critical Quality Attributes in Protein Biotherapeutics

The aspiration of the multi-attribute method (MAM) is to utilize a single mass spectrometry-based method that can measure multiple attributes simultaneously, thus enabling data-driven decisions more quickly and efficiently. However, challenges associated with identifying and quantitating critical quality attributes such as asparagine deamidation and isoaspartic acid using conventional ultrahigh-pressure liquid chromatography (UHPLC) coupled to mass spectrometry have necessitated long gradients to ensure sufficient separation for quantitation. Microfluidic chip-based capillary zone electrophoresis mass spectrometry (CZE-MS) shows potential to enable rapid charge-based separation of peptide mixtures, and this approach was evaluated using multipeptide mixtures of synthetic peptides as well as digested protein therapeutics. In these experiments, repeatability, linearity, and peak-to-peak resolution of several peptide families containing asparagine deamidation and/or isoaspartic acid were demonstrated. In addition, a comparison of peptide map results acquired with both UHPLC-MS and CZE-MS for two enzymatically digested biological therapeutics showed comparable sequence coverage and quantitation results between the two approaches. As MAM becomes increasingly utilized for analysis of biological therapeutics, MS instrument demand will rapidly increase, resulting in a bottleneck. A CZE-based separation shows potential to alleviate this bottleneck by drastically increasing MAM throughput while providing results comparable to those acquired using conventional UHPLC separations.

Solving Complex Biologics Truncation Problems by Top-Down Mass Spectrometry

With increasing protein therapeutics being designed as non-mAb (non-monoclonal antibody) modalities, additional efforts and resources are required to develop and characterize such therapeutic proteins. Truncation is an emerging issue for manufacturing of non-mAb drug substances and requires sophisticated methods to investigate. In this paper, we describe two cases with complex truncation problems where traditional methods such as intact mass spectrometry led to inclusive or wrong identifications. Therefore, we developed an online top-down LC-MS (liquid chromatography-mass spectrometry) based workflow to study truncated drug substances, and we successfully identified the clipping locations. Compared to other orthogonal methods, this method provides a unique capability of solving protein clipping problems. The successful identification of truncated species and the high compatibility to routine intact MS make it a very valuable tool for resolving truncation problems during protein production in the pharmaceutical industry.

Denaturing and Native Mass Spectrometric Analytics for Biotherapeutic Drug Discovery Research: Historical, Current, and Future Personal Perspectives

Mass spectrometry (MS) plays a key role throughout all stages of drug development and is now as ubiquitous as other analytical techniques such as surface plasmon resonance, nuclear magnetic resonance, and supercritical fluid chromatography, among others. Herein, we aim to discuss the history of MS, both electrospray and matrix-assisted laser desorption ionization, specifically for the analysis of antibodies, evolving through to denaturing and native-MS analysis of newer biologic moieties such as antibody-drug conjugates, multispecific antibodies, and interfering nucleic acid-based therapies. We discuss challenging therapeutic target characterization such as membrane protein receptors. Importantly, we compare and contrast the MS and hyphenated analytical chromatographic methods used to characterize these therapeutic modalities and targets within biopharmaceutical research and highlight the importance of appropriate MS deconvolution software and its essential contribution to project progression. Finally, we describe emerging applications and MS technologies that are still predominantly within either a development or academic stage of use but are poised to have significant impact on future drug development within the biopharmaceutic industry once matured. The views reflected herein are personal and are not meant to be an exhaustive list of all relevant MS performed within biopharmaceutical research but are what we feel have been historically, are currently, and will be in the future the most impactful for the drug development process.

Rapid and comprehensive monoclonal antibody Characterization using microfluidic CE-MS

The identification and control of monoclonal antibody (mAb) critical quality attributes (CQAs) is a key component of quality by design (QbD). In this work, rapid peptide mapping and native intact charge variants analysis have been developed to comprehensively characterize and monitor mAb CQAs using a microfluidic capillary electrophoresis - mass spectrometry (CE-MS) platform. The ultrafast peptide mapping simultaneously analyzed multiple CQAs, including protein primary structure, oxidation, deamidation, succinimide, C-terminal lysine (Lys) clipping, N-terminal cyclization, and glycosylation. The microfluidic CE-MS based peptide mapping acquired results comparable to conventional but lengthy liquid chromatography - MS (LC-MS) based approach. The native intact analysis resolved mAb charge variants with a comparable resolution as commonly achieved using capillary isoelectric focusing (cIEF). Charge variants' identities were assigned based on characteristic mass shifts, knowledge learned from peptide mapping, and changes in electrophoretic mobility. Major mAb glycoforms of each charge variants were resolved and identified in the deconvoluted mass spectra. Furthermore, a model simulation was performed to reconstruct intact deconvoluted mass spectra using peptide mapping results. The reconstructed and experimentally determined intact deconvoluted mass spectra were highly correlated, suggesting that our data collected at the peptide level and intact level were consistent and highly comparable. Overall, the microfluidic CE-MS based peptide mapping and native intact charge variants analysis are high-throughput methods that have great potential to support biopharmaceutical development.

A rapid, simple and sensitive microfluidic chip electrophoresis mass spectrometry method for monitoring amino acids in cell culture media

The development and optimization of cell culture media for biotech applications is a fundamental step of process development. The composition of cell culture media requires an ideal blend of amino acids, vitamins, nucleosides, lipids, carbohydrates, trace elements and other components. The ability to monitor these constituents is required to ensure that cells receive sufficient nutrients to facilitate growth, viability and productivity. Analysis of cell culture media is challenging due to the range and diversity of compounds contained in this matrix and normally requires time consuming methods. A rapid, simple and sensitive microfluidic chip CE-MS method is described to monitor amino acids in chemically defined cell culture media from a Chinese hamster ovary cell line cultured over a period of 10 days. The described platform enabled the separation of 16 amino acids in less than 2 minutes and without the requirement for extensive sample preparation. The analytical parameters evaluated were precision, linearity, limit of detection and limit of quantification. The majority of essential amino acids were present in cell culture growth in high concentrations compared to non-essential amino acids. Over the course of the 10 days cell culture the concentration of certain amino acids declined by up to 100%. Microfluidic chip based CE-MS methods can be used effectively to obtain the consumption rates of amino acids in cell culture media during cell growth and to perform at-line monitoring and screening of cell culture status.

In-capillary (electrophoretic) digestion-reduction-separation: A smart tool for middle-up analysis of mAb

Comprehensive characterization of physicochemical properties of monoclonal antibodies (mAbs) is a critical process to ensure their quality, efficacy, and safety. For this purpose, mAb analysis at different levels (bottom-up, middle-up) is a common approach that includes rather complex multistep sample preparation (reduction, digestion). To ensure high analysis performance, the development of fully integrated methodologies is highly valuable. Capillary zone electrophoresis is a particularly well-adapted technique for the multistep implementation of analytical strategies from sample preparation to detection. This feature was employed to develop novel integrated methodologies for the analysis of mAb at the middle-up level. Multiple in-line reactions (simultaneous reduction and digestion) were performed for the first time in the separation capillary. Tris (2-carboxyethyl) phosphine hydrochloride (TCEP) was used as an effective reducing agent under a broad pH range and IdeS (Immunoglobulin degrading enzyme from Streptococcus) as a highly specific enzyme for mAb digestion. Transverse diffusion of laminar flow profile (TDLFP) was applied for reactants mixing. Both in-line sample preparation and separation parameters were optimized under non-denaturing and denaturing conditions. The developed in-line methodologies provided good reproducibility and higher peak efficiencies comparing with off-line assays. They were successfully applied to different mAbs.

Characterization and monitoring of charge variants of a recombinant monoclonal antibody using microfluidic capillary electrophoresis-mass spectrometry

Rigorous characterization of biotherapeutics, and monoclonal antibodies in particular, is a challenging task in terms of ensuring safety, efficacy, and potency of a therapeutic agent because of structural heterogeneity during cell culture, purification and storage. In this work, we used microfluidic capillary electrophoresis-mass spectrometry to analyze intact monoclonal antibody and assess the root cause of increases in acidic and basic variants under stress at high temperature. The antibody was analyzed at multiple levels, including its intact state under native conditions, and subunit and peptide levels. The normal and degraded antibodies at different time points were characterized and compared with each other. We concluded that the basic variants in the unstressed sample were produced C-terminal amidation, while the acidic variants were produced by deamidation. In stressed samples, change in the acidic and main peaks were caused by deamidation, and changes in the basic peaks were caused by both deamidation and oxidation. These results demonstrate that microfluidic capillary electrophoresis-mass spectrometry (CE-MS) is a powerful direct and generic tool for separation and identification of charge heterogeneity of biotherapeutics.

Analysis of Monoclonal Antibodies by Capillary Electrophoresis: Sample Preparation, Separation, and Detection

Therapeutic monoclonal antibodies (mAbs) are dominating the biopharmaceutical field due to the fact of their high specificity in the treatment of diverse diseases. Nevertheless, mAbs are very complex glycoproteins exhibiting several macro- and microheterogeneities that may affect their safety, quality, and efficacy. This complexity is very challenging for mAbs development, formulation, and quality control. To tackle the quality issue, a combination of multiple analytical approaches is necessary. In this perspective, capillary electrophoresis has gained considerable interest over the last decade due to the fact of its complementary features to chromatographic approaches. This review provides an overview of the strategies of mAbs and derivatives analysis by capillary electrophoresis hyphenated to ultraviolet, fluorescence, and mass spectrometry detection. The main sample preparation approaches used for mAb analytical characterization (i.e., intact, middle-up/down, and bottom-up) are detailed. The different electrophoretic modes used as well as integrated analysis approaches (sample preparation and separation) are critically discussed.

Rapid fingerprinting of a highly glycosylated fusion protein by microfluidic chip-based capillary electrophoresis-mass spectrometry

Protein glycosylation can impact the efficacy, safety, and pharmacokinetics of therapeutic proteins. Achieving uniform and consistent protein glycosylation is an important requirement for product quality control at all stages of therapeutic protein drug discovery and development. The development of a new microfluidic CE device compatible with MS offers a fast and sensitive orthogonal mode of high-resolution separation with MS characterization. Here, we describe a fast and robust chip-based CE-MS method for intact glycosylation fingerprinting of a therapeutic fusion protein with complex sialylated N and O-linked glycoforms. The method effectively separates multiple sialylated glycoforms and offers a rapid detection of changes in glycosylation profile in 6 min.