Chromatographic media for bioseparation

Microfluidic devices with templated regular macroporous structures for HIV viral capture

There is a need to develop inexpensive, portable and easy-to-use devices for viral sample processing for resource-limited settings. Here we offer a solution to efficient virus capture by incorporating macroporous materials with regular structures into microfluidic devices for affinity chromatography. Two-dimensional simulations were first conducted to investigate the effects of two structures, a nanopost array and a spherical pore network, on nanoparticle capture. Then, the two structures were created in polymers by templating anodic aluminum oxide films and 3D close-packed silica particles, respectively. When the microdevices containing functionalized porous materials were tested for human immunodeficiency virus (HIV) isolation, capture efficiencies of 80-99% were achieved under a continuous flow. Comparatively, functionalized flatbed microchannels captured around 10% of HIV particles. As the characteristic dimensions of the nanostructures are tunable, such devices can be adapted for the capture of different submicron bioparticles. The high capture efficiency and easy-to-operate nature suit the needs of resource-limited settings and may find applications in point-of-care diagnostics.

Purification of Monoclonal Antibodies Using a Fiber Based Cation-Exchange Stationary Phase: Parameter Determination and Modeling

Monoclonal antibodies (mAb) currently dominate the market for protein therapeutics. Because chromatography unit operations are critical for the purification of therapeutic proteins, the process integration of novel chromatographic stationary phases, driven by the demand for more economic process schemes, is a field of ongoing research. Within this study it was demonstrated that the description and prediction of mAb purification on a novel fiber based cation-exchange stationary phase can be achieved using a physico-chemical model. All relevant mass-transport phenomena during a bind and elute chromatographic cycle, namely convection, axial dispersion, boundary layer mass-transfer, and the salt dependent binding behavior in the fiber bed were described. This work highlights the combination of model adaption, simulation, and experimental parameter determination through separate measurements, correlations, or geometric considerations, independent from the chromatographic cycle. The salt dependent binding behavior of a purified mAb was determined by the measurement of adsorption isotherms using batch adsorption experiments. Utilizing a combination of size exclusion and protein A chromatography as analytic techniques, this approach can be extended to a cell culture broth, describing the salt dependent binding behavior of multiple components. Model testing and validation was performed with experimental bind and elute cycles using purified mAb as well as a clarified cell culture broth. A comparison between model calculations and experimental data showed a good agreement. The influence of the model parameters is discussed in detail.

Cryogels with affinity ligands as tools in protein purification

Affinity chromatography is one of the well-known separation techniques especially if high purity is desired. Introducing ligands on monolithic structure gives the possibility for purifying complex media such as plasma and crude extract. This chapter is focusing on the preparation of cryogels as monolithic column and immobilization of concanavalin A on its surface as ligand for capturing the glycoprotein horseradish peroxidase.

Effects of polymer graft properties on protein adsorption and transport in ion exchange chromatography: a multiscale modeling study

Multiscale simulation is used to study the adsorption of lysozyme onto ion exchangers obtained by grafting charged polymers into a porous matrix, in systems with various polymer properties and strengths of electrostatic interaction. Molecular dynamics simulations show that protein partitioning into the polymer-filled pore space increases with the overall charge content of the polymers, while the diffusivity in the pore space decreases. However, the combination of greatly increased partitioning and modestly decreased diffusion results in macroscopic transport rates that increase as a function of charge content, as the large concentration driving force due to enhanced pore space partitioning outweighs the reduction in the pore space diffusivity. Matrices having greater charge associated with the grafted polymers also exhibit more diffuse intraparticle concentration profiles during transient adsorption. In systems with a high charge content per polymer and a low protein loading, the polymers preferentially partition toward the surface due to favorable interactions with the surface-bound protein. These results demonstrate the potential of multiscale modeling to illuminate qualitative trends between molecular properties and the adsorption equilibria and kinetic properties observable on macroscopic scales.

Biobased monoliths for adenovirus purification

Adenoviruses are important platforms for vaccine development and vectors for gene therapy, increasing the demand for high titers of purified viral preparations. Monoliths are macroporous supports regarded as ideal for the purification of macromolecular complexes, including viral particles. Although common monoliths are based on synthetic polymers as methacrylates, we explored the potential of biopolymers processed by clean technologies to produce monoliths for adenovirus purification. Such an approach enables the development of disposable and biodegradable matrices for bioprocessing. A total of 20 monoliths were produced from different biopolymers (chitosan, agarose, and dextran), employing two distinct temperatures during the freezing process (-20 °C and -80 °C). The morphological and physical properties of the structures were thoroughly characterized. The monoliths presenting higher robustness and permeability rates were further analyzed for the nonspecific binding of Adenovirus serotype 5 (Ad5) preparations. The matrices presenting lower nonspecific Ad5 binding were further functionalized with quaternary amine anion-exchange ligand glycidyltrimethylammonium chloride hydrochloride by two distinct methods, and their performance toward Ad5 purification was assessed. The monolith composed of chitosan and poly(vinyl) alcohol (50:50) prepared at -80 °C allowed 100% recovery of Ad5 particles bound to the support. This is the first report of the successful purification of adenovirus using monoliths obtained from biopolymers processed by clean technologies.

Combined effects of potassium chloride and ethanol as mobile phase modulators on hydrophobic interaction and reversed-phase chromatography of three insulin variants

The two main chromatographic modes based on hydrophobicity, hydrophobic interaction chromatography (HIC) and reversed-phase chromatography (RPC), are widely used for both analytical and preparative chromatography of proteins in the pharmaceutical industry. Despite the extensive application of these separation methods, and the vast amount of studies performed on HIC and RPC over the decades, the underlying phenomena remain elusive. As part of a systematic study of the influence of mobile phase modulators in hydrophobicity-based chromatography, we have investigated the effects of both KCl and ethanol on the retention of three insulin variants on two HIC adsorbents and two RPC adsorbents. The focus was on the linear adsorption range, separating the modulator effects from the capacity effects, but some complementary experiments at higher load were included to further investigate observed phenomena. The results show that the modulators have the same effect on the two RPC adsorbents in the linear range, indicating that the modulator concentration only affects the activity of the solute in the mobile phase, and not that of the solute-ligand complex, or that of the ligand. Unfortunately, the HIC adsorbents did not show the same behavior. However, the insulin variants displayed a strong tendency toward self-association on both HIC adsorbents; on one in particular. Since this causes peak fronting, the retention is affected, and this could probably explain the lack of congruity. This conclusion was supported by the results from the non-linear range experiments which were indicative of double-layer adsorption on the HIC adsorbents, while the RPC adsorbents gave the anticipated increased tailing at higher load.

Evaluation of synthesized lipid tethered ligands for surface functionalization of polypropylene capillary-channeled polymer fiber stationary phases

A straight forward approach to the synthesis of ligand tethered ligands (LTLs) circumvents the purchase of less-robust, PEG-phospholipids.

Recovery of Proteins Affected by Mobile Phase Trifluoroacetic Acid Concentration in Reversed-Phase Chromatography

It was found that recoveries of proteins depend on trifluoroacetic acid concentration in the mobile phase and showed maximum in the range of 0.01-0.1 v/v%. Transferrin and lysozyme were used to evaluate the recoveries of proteins from dedicated reversed-phase columns. Different types of reversed-phase columns were evaluated, such as core shell type materials (Aeris Widepore with C4, C8 and C18 modification) as well as fully porous hybrid particles (Waters BEH, modified with C4 and C18 alkyl chains). Recoveries ranged between 60.7-95.2% for transferrin and 72.1-99.8% for lysozyme. Based on the data presented, at least two different adsorption effects, the well-known hydrophobic and silanophilic/polar interaction might influence the recovery. In addition to this, conformational effects due to ion pairing with the acidic mobile phase additive might change them.

HPLC enrichment/isolation of proteins for post-translational modification studies from complex mixtures

The paper describes a macroporous RP-HPLC method for separation and isolation/enrichment of proteins from complex mixtures. The method is robust and efficient; using 2.1 or 4.6mm diameter columns provides sufficient material for subsequent proteomic analysis. The main advantage of the method is that most protein variants are isolated in the same fraction, as separation is not based on differences in isoelectric point. This is highly advantageous for studying complex mixtures and post-translational modifications. Examples related to glycosylation analysis are discussed in detail.

Rapid chromatographic determination of caseins in milk with photometric and fluorimetric detection using a hydrophobic monolithic column

Reverse-phase liquid chromatographic methods using a hydrophobic C18 monolithic column and on-line photometric and fluorimetric detection for the determination of the major casein (CN) proteins in milk are presented. The separation of αs1-CN, αs2-CN, β-CN and κ-CN was achieved in only five minutes. Fluorimetric detection enabled better analytical results than photometric detection. Thus, the dynamic ranges of the calibration graphs and detection limits obtained using fluorimetric detection were (mgmL(-)(1)): αs1-CN (0.74-10.0, 0.22), αs2-CN (0.15-10.0, 0.045), β-CN (0.68-10.0, 0.20) and κ-CN (0.21-10.0, 0.06). The analytical features of the photometric method, which does not allow the quantification of β-casein, were (mgmL(-)(1)): αs1-CN (1.5-9.0, 0.45), αs2-CN (1.4-10.0, 0.43) and κ-CN (0.4-9.0, 0.12). Precision data, expressed as relative standard deviation, ranged between 0.6% and 5.3% for the fluorimetric method and between 2.4% and 6.2% for the photometric method. Both methods were applied to the analysis of three different milk samples, obtaining recoveries in the ranges of 86.6-103.2% and 92.0-106.5% using fluorimetric and photometric detection, respectively.

Modeling of ion exchange expanded-bed chromatography for the purification of C-phycocyanin

This work is focused on the experimental evaluation and mathematical modeling of ion exchange expanded-bed chromatography for the purification of C-phycocyanin from crude fermentative broth containing Spirulina platensis cells. Experiments were carried out in different expansion degree to evaluate the process performance. The experimental breakthrough curves were used to estimate the mass transfer and kinetics parameters of the proposed model, using the Particle Swarm Optimization algorithm (PSO). The proposed model satisfactorily fitted the experimental data. The results from the model application pointed out that the increase in the initial bed height does not influence the process efficiency, however enables the operation of expanded-bed column at high volumetric flow rates, improving the productivity. It was also shown that the use of mathematical modeling was a good and promising tool for the optimization of chromatographic processes.

Adsorption of milk proteins on to calcium phosphate particles

The adsorption of caseins from sodium caseinate (SC) and whey proteins from whey protein isolate (WPI) on to particles of hydroxyapatite (HA) was studied. Confocal microscopy and zeta-potential measurements showed that both caseins and whey proteins bound to HA, resulting in an increase in the absolute value of the zeta-potential of the particles. This adsorption improved the suspension stability of the HA particles in water. For both protein sources, there was a preference in the protein adsorption: in the order β-casein > α(s)-casein > κ-casein for sodium-caseinate-coated particles; in the order β-lactoglobulin > α-lactalbumin for WPI-coated particles. The adsorption of caseins and whey proteins on to HA could be fitted using a simple Langmuir model, suggesting a single layer adsorption of caseins and whey proteins on to the HA surface. Possible mechanisms involved in the interaction between milk proteins and HA are discussed, in relation to the structure and the surface properties of both milk proteins and HA particles.

Principles and applications of steric exclusion chromatography

We introduce a chromatography method for purification of large proteins and viruses that works by capturing them at a non-reactive hydrophilic surface by their mutual steric exclusion of polyethylene glycol (PEG). No direct chemical interaction between the surface and the target species is required. We refer to the technique as steric exclusion chromatography. Hydroxyl-substituted polymethacrylate monoliths provide a hydrophilic surface and support convective mass transport that is unaffected by the viscosity of the PEG. Elution is achieved by reducing PEG concentration. Selectivity correlates with molecular size, with larger species retained more strongly than smaller species. Retention increases with PEG size and concentration. Salts weaken retention in proportion to their concentration and Hofmeister ranking. Retention is enhanced near the isoelectric point of the target species. Virus binding capacity was measured at 9.9×10(12) plaque forming units per mL of monolith. 99.8% of host cell proteins and 93% of DNA were eliminated. Mass recovery exceeded 90%. IgM capacity was greater than 60 mg/mL. 95% of host cell proteins were eliminated from IgM produced in protein-free media, and mass recovery was up to 90%. Bioactivity was fully conserved by both viruses and antibodies. Process time ranged from less than 30 min to 2 h depending on the product concentration in the feed stream.