The Effect of Temperature in Sodium Dodecyl Sulfate Capillary Gel Electrophoresis of Protein Therapeutics

Application of Analytical Quality by Design to the development and validation of reduced and non-reduced capillary electrophoresis analytical procedures for mAb purity determination

Capillary electrophoresis-sodium dodecyl sulfate (CE-SDS) is a common analytical procedure used to quantitate critical quality attributes relating to the purity and glycosylation of monoclonal antibodies (mAbs). In this study, the application of an Analytical Quality by Design framework incorporating Design of Experiments was used to develop and validate both non-reduced (CE-NR) and reduced (CE-R) versions of this analytical procedure. Formal risk assessments were used to identify critical method attributes for optimization based on their potential impacts to performance criteria outlined in an analytical target profile. The resulting response surfaces connecting these critical factors to method performance were then utilized to generate a harmonized procedure to reduce execution risk across CE-R and CE-NR applications. Validation of these procedures according to regulatory guidelines support that they meet their required performance criteria, and a multivariate assessment of procedure robustness indicates that method parameters are in a sufficient state of control to ensure appropriate quantitation of mAb quality. Overall, this study demonstrates the utility of adopting an Analytical Quality by Design framework to leverage multidimensional knowledge from multiple critical method parameters to ensure an analytical procedure is fit-for-purpose.

Recent advances in microscale separation techniques for glycome analysis

The glycomic analysis holds significant appeal due to the diverse roles that glycans and glycoconjugates play, acting as modulators and mediators in cellular interactions, cell/organism structure, drugs, energy sources, glyconanomaterials, and more. The glycomic analysis relies on liquid-phase separation technologies for molecular purification, separation, and identification. As a miniaturized form of liquid-phase separation technology, microscale separation technologies offer various advantages such as environmental friendliness, high resolution, sensitivity, fast speed, and integration capabilities. For glycan analysis, microscale separation technologies are continuously evolving to address the increasing challenges in their unique manners. This review discusses the fundamentals and applications of microscale separation technologies for glycomic analysis. It covers liquid-phase separation technologies operating at scales generally less than 100 µm, including capillary electrophoresis, nanoflow liquid chromatography, and microchip electrophoresis. We will provide a brief overview of glycomic analysis and describe new strategies in microscale separation and their applications in glycan analysis from 2014 to 2023.

Size separation of sodium dodecyl sulfate-proteins by capillary electrophoresis in dilute and ultra-dilute dextran solutions

SDS capillary gel electrophoresis is a widely used in the biopharma and the biomedical fields for rapid size separation of proteins. However, very limited information is available on the use of dilute and ultra-dilute sieving matrices for SDS-protein analysis. Here, background electrolytes (BGEs) containing 1%-0% dextran were used in borate-based BGE to separate a protein sizing ladder (PSL) ≤225 kDa and the intact and subunit forms of a therapeutic monoclonal antibody (mAb). The separation performance for the PSL and mAb components differed significantly with decreasing dextran concentration. Ferguson and reptation plots were used to elucidate the separation mechanism. Highly diluted dextran solutions resulted in linear Ferguson plots for both solute types (cf. Ogston theory) in spite of this model assumes a rigid pore structure, thus cannot describe the separation mechanism in ultra-dilute polymer solutions with no reticulations. The saddle differences between the resolution of the PSL and the intact/subunit mAb forms in ultra-dilute dextran-borate matrices suggested the importance of shape selectivity, manifested by the adequate separation of the SDS covered intact as well as light and heavy chain subunits of the therapeutic mAb even at zero dextran concentration.

Gels in Microscale Electrophoresis

Gel matrices are fundamental to electrophoresis analyses of biopolymers in microscale channels. Both capillary gel and microchannel gel electrophoresis systems have produced fundamental advances in the scientific community. These analytical techniques remain as foundational tools in bioanalytical chemistry and are indispensable in the field of biotherapeutics. This review summarizes the current state of gels in microscale channels and provides a brief description of electrophoretic transport in gels. In addition to the discussion of traditional polymers, several nontraditional gels are introduced. Advances in gel matrices highlighted include selective polymers modified to contain added functionality as well as thermally responsive gels formed through self-assembly. This review discusses cutting-edge applications to challenging areas of discovery in DNA, RNA, protein, and glycan analyses. Finally, emerging techniques that result in multifunctional assays for real-time biochemical processing in capillary and three-dimensional channels are identified.

Gel Electrophoresis Chip Using Joule Heat Self-Dissipation, Short Run Time, and Online Dynamic Imaging

Gel electrophoresis (GE) is one of the most general tools in biomedicine. However, it suffers from low resolution, and its mechanism has not been fully revealed yet. Herein, we presented the dispersion model of w² (t) ∝ Tt, showing the band dispersion (w) via temperature (T) and running time (t) control. Second, we designed an efficient GE chip via the time control and rapid Joule heat self-dissipation by thermal conductive plastic (TCP) and electrode buffer. Third, we conducted the simulations on TCP and polymethylmethacrylate (PMMA) chips, unveiling that (i) the temperature of TCP was lower than the PMMA one, (ii) the temperature uniformity of TCP was better than the PMMA one, and (iii) the resolution of TCP was superior to the PMMA one. Fourth, we designed both TCP and PMMA chips for experimentally validating the dispersion model, TCP chip, and simulations. Finally, we applied the TCP chip to thalassemia and model urine protein assays. The TCP chip has merits of high resolution, rapid run of 6-10 min, and low cost. This work paves the way for greatly improving electrophoretic techniques in gel, chip, and capillary via temperature and time control for biologic study, biopharma quality control, clinical diagnosis, and so on.

Capillary sodium dodecyl sulfate gel electrophoresis of proteins: Introducing the three dimensional Ferguson method

One of the most extensively utilized rapid characterization, release and stability testing methods of therapeutic proteins in the biopharmaceutical field today is capillary SDS gel electrophoresis using borate cross-linked high molecular weight dextran. In spite of its widespread use, however, the gel composition dependent separation characteristics of this very unique sieving matrix has not been investigated yet. Introduction of three dimensional (3D) Ferguson plots, based on simultaneous variation of the dextran (D) and borate (B) concentrations generating 16 different D/B ratio gels, allowed better understanding of the electromigration process of the SDS-protein complexes. As a result of this comprehensive study, non-linear 3D logarithmic mobility vs dextran and borate concentration surfaces were obtained. Both, the molecular weight protein standards and the new modality fusion protein etanercept resulted in concave 3D Ferguson plots. The interplay between the electroosmotic flow and the viscosity of the matrices played a key role in the resulting migration time and resolution. Selectivity values were defined and evaluated in 3D graph formats for the regular and de-N-glycosylated subunits of etanercept, as well as for the latter with the 10 kDa internal standard to understand both the dextran-borate complexation and sized based selectivities. K_R plots of the retardation coefficients as the function of the logarithmic molecular weights were used to more precisely assess the Mw of the samples and to obtain information about the molecular characteristics of the electromigrating SDS-protein complexes.

Fundamentals of Capillary Electrophoretic Migration and Separation of SDS Proteins in Borate Cross-Linked Dextran Gels

Recent progress in the development and production of new, innovative protein therapeutics require rapid and adjustable high-resolution bioseparation techniques. Sodium dodecyl sulfate capillary gel electrophoresis (SDS-CGE) using a borate (B) cross-linked dextran (D) separation matrix is widely employed today for rapid consistency analysis of therapeutic proteins in manufacturing and release testing. Transient borate cross-linking of the semirigid dextran polymer chains leads to a high-resolution separation gel for SDS-protein complexes. To understand the migration and separation basis of the D/B gel, the present work explores various gel formulations of dextran monomer (2, 5, 7.5, and 10%) and borate cross-linker (2 and 4%) concentrations. Ferguson plots were analyzed for a mixture of protein standards with molecular weights ranging from 20 to 225 kDa, and the resulting nonlinear concave curves pointed to nonclassical sieving behavior. While the 2% D/4% B gel resulted in the fastest analysis time, the 10% D/2% B gel was found to produce the greatest separation window, even higher than with the 10% D/4% B gel, due to a significant increase in the electroosmotic flow of the former composition in the direction opposite to SDS-protein complex migration. The study then focused on SDS-CGE separation of a therapeutic monoclonal antibody and its subunits. A combination of molecular weight and shape selectivity as well as, to a lesser extent, surface charge density differences (due to glycosylation on the heavy chain) influenced migration. Greater molecular weight selectivity occurred for the higher monomer concentration gels, while improved glycoselectivity was obtained using a more dilute gel, even as low as 2% D/2% B. This latter gel took advantage of the dextran-borate-glycoprotein complexation. The study revealed that by modulating the dextran (monomer) and borate (cross-linker) concentration ratios of the sieving matrix, one can optimize the separation for specific biopharmaceutical modalities with excellent column-to-column, run-to-run, and gel-to-gel migration time reproducibilities (<0.96% relative standard deviation (RSD)). The widely used 10% dextran/4% borate gel represents a good screening option, which can then be followed by a modified composition, optimized for a specific separation as necessary.