Evaluation of loading characteristics and IgG binding performance of Staphylococcal protein A on polypropylene capillary-channeled polymer fibers

Quantitative Recoveries of Exosomes and Monoclonal Antibodies from Chinese Hamster Ovary Cell Cultures by Use of a Single, Integrated Two-Dimensional Liquid Chromatography Method

Cultured cell lines are very commonly used for the mass production of therapeutic proteins, such as monoclonal antibodies (mAbs). In particular, Chinese hamster ovary (CHO) cell lines are widely employed due to their high tolerance to variations in experimental conditions and their ability to grow in suspension or serum free media. CHO cell lines are known for their ability to produce high titers of biotherapeutic products such as immunoglobulin G (IgG). An emergent alternative means of treating diseases, such as cancer, is the use of gene therapies, wherein genetic cargo is "packaged" in nanosized vesicular structures, referred to as "vectors". One particularly attractive vector option is extracellular vesicles (EVs), of which exosomes are of greatest interest. While exosomes can be harvested from virtually any human body fluid, bovine milk, or even plants, their production in cell cultures is an attractive commercial approach. In fact, the same CHO cell types employed for mAb production also produce exosomes as a natural byproduct. Here, we describe a single integrated 2D liquid chromatography (2DLC) method for the quantitative recovery of both exosomes and antibodies from a singular sample aliquot. At the heart of the method is the use of polyester capillary-channeled polymer (C-CP) fibers as the first dimension column, wherein exosomes/EVs are captured from the supernatant sample and subsequently determined by multiangle light scattering (MALS), while the mAbs are captured, eluted, and quantified using a protein A-modified C-CP fiber column in the second dimension, all in a 10 min workflow. These efforts demonstrate the versatility of the C-CP fiber phases with the capacity to harvest both forms of therapeutics from a single bioreactor, suggesting an appreciable potential impact in the field of biotherapeutics production.

Alleviation of the necessity for supernatant prefiltering in the protein a recovery of Monoclonal antibodies from Chinese hamster ovary cell cultures

Protein A (ProA) chromatography is a mainstay in the analytical and preparative scale isolation/purification of monoclonal antibodies (mAbs). One area of interest is continuous processing or continuous chromatography, where ProA chromatography is used in the large-scale purification of mAbs. However, filtration is required prior to all ProA isolations to remove large particulates in cell culture supernatant, consisting of a mixture of cell debris, host cell contaminants, media components, etc. Currently, in-line filters are used to remove particles in the supernatant, requiring replacement over time due to fouling; regardless of the scale. Here we demonstrate the ProA isolation of unfiltered Chinese hamster ovary (CHO) cell media using capillary-channel polymer (C-CP) fiber stationary phases modified with S. aureus Protein A (rSPA). The base polymer of the analytical scale C-CP columns costs ∼$5 per 30 cm column, and when modified with ProA, the base cost is ∼$25 per 30 cm column, a cost-effective option in comparison to analytical-scale commercial columns. To directly sample unfiltered media, a 5 cm gap was created at the head of the C-CP column, where the large particulates are trapped, while molecular solutes flow through the capillary channels without sacrifice in analytical performance, mAb loading capacity, or backpressure increases. The binding capacity of the gap ProA C-CP column was ∼ 2 mg mL-1 of IgG per bed volume. The same analytical column could be operated after processing a total of ∼ 56 column bed volumes of supernatant (>25 analytical cycles) without the need for caustic clean-in-place processing.

Loading characteristics of streptavidin on polypropylene capillary channeled polymer fibers and capture performance towards biotinylated proteins

The development of higher-throughput, potentially lower-cost means to isolate proteins, for a variety of end uses, is of continuing emphasis. Polypropylene (PP) capillary-channeled polymer (C-CP) fiber columns are modified with the biotin-binding protein streptavidin (SAV) to capture biotinylated proteins. The loading characteristics of SAV on fiber supports were determined using breakthrough curves and frontal analysis. Based on adsorption data, a 3-min on-column loading at a flow rate of 0.5 mL min-1 (295.2 cm h-1) with a SAV feed concentration of 0.5 mg mL-1 produces a SAV loading capacity of 1.4 mg g-1 fiber. SAV has an incredibly high affinity for the small-molecule biotin (10-14 M), such that this binding relationship can be exploited by labeling a target protein with biotin via an Avi-tag. To evaluate the capture of the biotinylated proteins on the modified PP surface, the biotinylated versions of bovine serum albumin (b-BSA) and green fluorescent protein (b-GFP) were utilized as probe species. The loading buffer composition and flow rate were optimized towards protein capture. The non-ionic detergent Tween-20 was added to the deposition solutions to minimize non-specific binding. Values of 0.25-0.50% (v/v) Tween-20 in PBS exhibited better capture efficiency, while minimizing the non-specific binding for b-BSA and b-GFP, respectively. The C-CP fiber platform has the potential to provide a fast and low-cost method to capture targeted proteins for applications including protein purification or pull-down assays.

Two-dimensional separation of water-soluble polymers using size exclusion and reversed phase chromatography employing capillary-channeled polymer fiber columns

Polymeric materials are readily available, durable materials that have piqued the interest of many diverse fields, ranging from biomedical engineering to construction. The physiochemical properties of a polymer dictate the behavior and function, where large polydispersity among polymer properties can lead to problems; however, current polymer analysis methods often only report results for one particular property. Two-dimensional liquid chromatography (2DLC) applications have become increasingly popular due to the ability to implement two chromatographic modalities in one platform, meaning the ability to simultaneously address multiple physiochemical aspects of a polymer sample, such as functional group content and molar mass. The work presented employs size exclusion chromatography (SEC) and reversed-phase (RP) chromatography, through two coupling strategies: SEC x RP and RP x RP separations of the water-soluble polymers poly(methacrylic acid) (PMA) and polystyrene sulfonic acid (PSSA). Capillary-channeled polymer (C-CP) fiber (polyester and polypropylene) stationary phases were used for the RP separations. Particularly attractive is the fact that they are easily implemented as the second dimension in 2DLC workflows due to their low backpressure (<1000 psi at ∼70 mm sec^-1) and fast separation times. In-line multi-angle light scattering (MALS) was also implemented for molecular weight determinations of the polymer samples, with the molecular weight of PMA ranging from 5 × 10⁴ to 2 × 10⁵ g mol^-1, while PSSA ranges from 10⁵ to 10⁸ g mol^-1. While the orthogonal pairing of SEC x RP addresses polymer sizing and chemistry, this approach is limited by long separation times (80 min), the need for high solute concentrations (PMA = 1.79 mg mL^-1 and PSSA = 0.175 mg mL^-1 to yield comparable absorbance responses) due to on-column dilution and subsequently limited resolution in the RP separation space. With RP x RP couplings, separation times were significantly reduced (40 min), with lower sample concentrations (0.595 mg mL^-1 of PMA and 0.05 mg mL^-1 of PSSA) required. The combined RP strategy provided better overall distinction in the chemical distribution of the polymers, yielding 7 distict species versus 3 for the SEC x RP coupling.

Comparison of the separation of proteins of wide-ranging molecular weight via trilobal polypropylene capillary-channeled polymer fiber, commercial superficiously porous, and commercial size exclusion columns

Reversed phase and size-exclusion chromatography methods are commonly used for protein separations, though based on distinctly different principles. Reversed phase methods yield hydrophobicity-based (loosely-termed) separation of proteins on porous supports, but tend to be limited to proteins with modest molecular weights based on mass transfer limitations. Alternatively, size-exclusion provides complementary benefits in the separation of higher-mass proteins based on entropic, not enthalpic, processes, but tend to yield limited peak capacities. In this study, microbore columns packed with a novel trilobal polypropylene capillary-channeled polymer fiber were used in a reversed phase modality for the separation of polypeptides and proteins of molecular weights ranging from 1.4 to 660 kDa. Chromatographic parameters including gradient times, flow rates and trifluoroacetic acid concentrations in the mobile phase were optimized to maximize resolution and throughput. Following optimization, the performance of the trilobal fiber column was compared to two commercial-sourced columns, a superficially porous C4-derivatized silica and size exclusion, both of which are sold specifically for protein separations and operated according to the manufacturer-specified conditions. In comparison to the commercial columns, the fiber-based column yielded better separation performance across the entirety of the suite, at much lower cost and shorter separation times. This article is protected by copyright. All rights reserved.

Nanoparticle transfer biosensors for the non-invasive detection of SARS-CoV-2 antigens trapped in surgical face masks

Detecting SARS-CoV-2 antigens in respiratory tract samples has become a widespread method for screening new SARS-CoV-2 infections. This requires a nasopharyngeal swab performed by a trained healthcare worker, which puts strain on saturated healthcare services. In this manuscript we describe a new approach for non-invasive COVID-19 diagnosis. It consists of using mobile biosensors for detecting viral antigens trapped in surgical face masks worn by patients. The biosensors are made of filter paper containing a nanoparticle reservoir. The nanoparticles transfer from the biosensor to the mask on contact, where they generate colorimetric signals that are quantified with a smartphone app. Sample collection requires wearing a surgical mask for 30 min, and the total assay time is shorter than 10 min. When tested in a cohort of 27 patients with mild or no symptoms, an area under the receiving operating curve (AUROC) of 0.99 was obtained (96.2 % sensitivity and 100 % specificity). Serial measurements revealed a high sensitivity and specificity when masks were worn up to 6 days after diagnosis. Surgical face masks are inexpensive and widely available, which makes this approach easy to implement anywhere. The excellent sensitivity, even when tested with asymptomatic patient samples, along with the mobile detection scheme and non-invasive sampling procedure, makes this biosensor design ideal for mass screening.

Dynamic evaluation of a trilobal capillary-channeled polymer fiber shape for reversed phase protein separations and comparison to the eight-channeled form

A new, trilobal-shaped capillary-channeled polymer fiber is under development to address the issues of poor A-term performance of the previous eight-channeled form. The trilobal geometry should provide better packing homogeneity due to the fewer potential orientations of the symmetric fiber geometry. Comparisons of separation efficiency and peak shape were made between the two fiber shapes through several dynamic parameters. Column hydrodynamics were investigated with two marker compounds, uracil and bovine serum albumin, with van Deemter plots of those two compounds revealing differences in the packing qualities between the different fiber shapes. Parametric fitting to the van Deemter, Knox, and Giddings equations provides insights into the column physical structures. Separation quality for both shapes was evaluated across differences in fiber packing density, gradient rate, and mobile phase linear velocity for the reversed phase separation of a four protein mixture, containing ribonuclease A, cytochrome c, lysozyme, and myoglobin. The results of this study lay the ground work for future efforts in the use of trilobal fibers for the separation of biomacromolecules.

Application of protein A-modified capillary-channeled polymer polypropylene fibers to the quantitation of IgG in complex matrices

Polypropylene (PP) capillary-channeled polymer (C-CP) fibers loaded with recombinant Staphyloccocus aureus protein A (rSPA) were used as an affinity chromatography stationary phase for the quantitation of immunoglobulin G (IgG) in complex biological matrices. Optimization of the chromatographic method regarding mobile phase components and load/elution conditions was performed. The six-minute analysis, including a load step with 12mM phosphate at pH 7.4, an elution step with 0.025% phosphoric acid and a re-equilibration step, was employed for quantitation of IgG1 from 0.075 to 3.00mgmL^-1 in an IgG-free CHO cell supernatant matrix. Quantification of IgG1 content in a different CHO cell line was accomplished using the external calibration curve as well as using a standard addition approach. The high level of agreement between the two approaches suggests that the protein A-modified C-CP fiber phase is immune from matrix effects due to concomitant species such as host cell proteins (HCPs), host cell DNA, media components and other leachables and extractables. The inter-day and intra-day precision of the method were 3.1 and 3.5%RSD respectively for a single column. Column-to-column variability was 1.31 and 6.62%RSD for elution time and peak area, respectively, across columns prepared in different batches. The method reported here is well-suited for IgG analysis in complex harvest cell culture media in both the development and production environments.

Microwave-assisted grafting polymerization modification of nylon 6 capillary-channeled polymer fibers for enhanced weak cation exchange protein separations

A weak cation exchange liquid chromatography stationary phase (nylon-COOH) was prepared by grafting polyacrylic acid on to native nylon 6 capillary-channeled polymer (C-CP) fibers via a microwave-assisted radical polymerization. To the best of our knowledge, this is the first study of applying microwave-assisted grafting polymerization to affect nylon material for protein separation. The C-CP fiber surfaces were characterized by attenuated total reflection (ATR) infrared spectroscopy and scanning electron microscope (SEM). The anticipated carbonyl peak at 1722.9 cm^-1 was found on the nylon-COOH fibers, but was not found on the native fiber, indicating the presence of the polyacrylic acid on nylon fibers after grafting. The nylon-COOH phase showed a ∼12× increase in lysozyme dynamic binding capacity (∼12 mg mL^-1) when compared to the native fiber phase (∼1 mg mL^-1). The loading capacity of the nylon-COOH phase is nearly independent of the lysozyme loading concentration (0.05-1 mg mL^-1) and the mobile phase linear velocity (7.3-73 mm s^-1). The reproducibility of the lysozyme recovery from the nylon-COOH (RSD = 0.3%, n = 10) and the batch-to-batch variability in the functionalization (RSD = 3%, n = 5) were also investigated, revealing very high levels of consistency. Fast baseline separations of myoglobin, α-chymotrypsinogen A, cytochrome c and lysozyme were achieved using the nylon-COOH column. It was found that a 5× increase in the mobile phase linear velocity (7.3-to-36.5 mm s^-1) had little effect on the separation resolution. The microwave-assisted grafting polymerization has great potential as a generalized surface modification methodology across the applications of C-CP fibers.