Hydrophobic interaction chromatography for purification of monoPEGylated RNase A

A monolithic stationary phase with dendritic nanostructures for the separation of PEGylated proteins

Separation of PEGylated protein mixtures into individual species is a challenging procedure, and many efforts have been focused on creating novel chromatographic supports for this purpose. In this study, a new monolithic stationary phase with hyperbranched nanostructures was chemically synthesized. For this, monoliths with a support matrix of poly (glycidyl methacrylate-co-ethylene dimethacrylate) and ethylenediamine chemistry were modified with third-generation dendrons with butyl-end groups. The new monolith was analyzed by infrared spectroscopy, confirming the dendron with butyl ligands and exhibited low mass transfer resistance as observed by breakthrough frontal analysis. This support was able to separate mono-PEG ribonuclease A from the PEGylation mixture, indicated by a single band (∼30 kDa) in the electrophoretic analysis. Moreover, the separation of mono-PEGylated positional isomers was probably observed, as the protein with ∼30 kDa was found in two separate peaks. Interestingly, the dendronized monolith allowed the separation of the reaction mixture into individual PEGylated species when using high ammonium sulfate concentrations (2 M). A correlation between the PEGylation degree and the strength of the hydrophobic interactions on the monolith was observed. This chromatographic approach combines the natural branched architecture of dendrons and the higher capabilities of the monoliths enhancing the hydrophobic surface area, and therefore the interaction between the PEGylated proteins and ligands. Thus, the novel support represents a novel platform for the purification of PEGylated from non-PEGylated proteins with biotechnological applications.

Process Development for the Production and Purification of PEGylated RhG-CSF Expressed in Escherichia coli

Background and objective:

Recombinant human granulocyte-colony stimulating factor (rhG-CSF) and its PEGylated form (PEG-GCSF) are used in the cancer therapy. Thus the development of a more cost-effectively method for expressing rhG-CSF and the PEGylation optimization of rhG-CSF by reaction engineering and subsequent the purification strategy is necessary.

Methods:

RhG-CSF expression in Escherichia coli BL21 (DE3) was carried out by auto-induction batch fermentation and improved for maximizing rhG-CSF productivity. After that, purified rhG-CSF was PEGylated using methoxy polyethylene glycol propionaldehydes (mPEG20-ALD). The various conditions effect of extraction and purification of rhG-CSF and PEG-GCSF were assayed.

Results:

The assessment results revealed that auto-induction batch cultivation strategy had maximum productivity and rhG-CSF purity was more than 99%. The obtained Data of rhG-CSF PEGylation displayed that the optimized conditions of rhG-CSF PEGylation and purification enhanced hemogenisity PEG-GCSF and managed reaction toward optimal yield of PEG-GCSF (70%) and purity of 99.9%. Findings from FTIR, CD, and fluorescence spectroscopy and bioassay revealed that PEGylation was executed exactly in the rhG-CSF N-terminus, and products maintained their conformation properties.

Conclusion:

Overall, the developed approach expanded strategies for high yield rhG-CSF by simplified auto-induction batch fermentation system and rhG-CSF PEGylation, which are simple and time-saving, economical and high efficiency.

Purification of Modified Therapeutic Proteins Available on the Market: An Analysis of Chromatography-Based Strategies

Proteins, which have inherent biorecognition properties, have long been used as therapeutic agents for the treatment of a wide variety of clinical indications. Protein modification through covalent attachment to different moieties improves the therapeutic's pharmacokinetic properties, affinity, stability, confers protection against proteolytic degradation, and increases circulation half-life. Nowadays, several modified therapeutic proteins, including PEGylated, Fc-fused, lipidated, albumin-fused, and glycosylated proteins have obtained regulatory approval for commercialization. During its manufacturing, the purification steps of the therapeutic agent are decisive to ensure the quality, effectiveness, potency, and safety of the final product. Due to the robustness, selectivity, and high resolution of chromatographic methods, these are recognized as the gold standard in the downstream processing of therapeutic proteins. Moreover, depending on the modification strategy, the protein will suffer different physicochemical changes, which must be considered to define a purification approach. This review aims to deeply analyze the purification methods employed for modified therapeutic proteins that are currently available on the market, to understand why the selected strategies were successful. Emphasis is placed on chromatographic methods since they govern the purification processes within the pharmaceutical industry. Furthermore, to discuss how the modification type strongly influences the purification strategy, the purification processes of three different modified versions of coagulation factor IX are contrasted.

Fast and high-resolution purification of a PEGylated protein using a z2 laterally-fed membrane chromatography device

PEGylated proteins comprise a class of value-added biopharmaceuticals. High-resolution separation techniques are required for the purification of these molecules. In this study, we discuss the application of a newly developed z² laterally-fed membrane chromatography (or z²LFMC) device for carrying out high-resolution purification of a PEGylated protein drug. The device used in the current study contained a stack of anion exchange (Q) membranes. The membrane bed-height of this z²LFMC device being small, it could be operated at very high flow rates, at relatively low back pressures. The primary goal was to speedily and efficiently separate a mono-PEGylated protein from impurities present in the PEGylation reaction mixture. A resin-based anion exchange column having the same ligand and bed-volume was used as the control device. The purification performance of the z²LFMC device and the control column were compared terms of resolution, recovery and purity. The z²LFMC device outperformed the control column in terms of every metric compared in this study. Higher purity (85.4% as opposed to 77.9%) and higher recovery (28% greater) of the target mono-PEGylated protein were obtained using the z²LFMC device at 20-time higher speed. These results clearly demonstrate that the z²LFMC device could be a faster and more efficient alternative to resin-based columns for purification of biopharmaceuticals.

Recent advances on protein separation and purification methods

Protein, as the material basis of vita, is the crucial undertaker of life activities, which constitutes the framework and main substance of human tissues and organs, and takes part in various forms of life activities in organisms. Separating proteins from biomaterials and studying their structures and functions are of great significance for understanding the law of life activities and clarifying the essence of life phenomena. Therefore, scientists have proposed the new concept of proteomics, in which protein separation technology plays a momentous role. It has been diffusely used in the food industry, agricultural biological research, drug development, disease mechanism, plant stress mechanism, and marine environment research. In this paper, combined with the recent research situation, the progress of protein separation technology was reviewed from the aspects of extraction, precipitation, membrane separation, chromatography, electrophoresis, molecular imprinting, microfluidic chip and so on.

High-resolution purification of a therapeutic PEGylated protein using a cuboid packed-bed device

PEGylated proteins which are a class of protein-synthetic polymer conjugates that have shown significant promise in the area of biotherapeutics are difficult to purify. A cuboid packed-bed device was used to purify a mono-PEGylated therapeutic protein from impurities such as high molecular weight (HMW) species (e.g., tri- and/or di-PEGylated forms), and low molecular weight (LMW) species such as unreacted protein and polyethylene glycol (or PEG). The separation efficiency of this device was compared with that of an equivalent cylindrical column. The effects of operating conditions such as flow rate, buffer composition, elution gradient, and column loading were systematically compared. An equivalent column with the same bed volume, same resin and same bed height was served as control. In mono-PEGylated protein purifications experiments, the cuboid packed-bed device exhibited sharper peaks and gave better resolution at all conditions examined in this study. The purity of mono-PEGylated protein in the samples collected from the cuboid packed-bed device and the column were comparable, i.e., 98.1% and 97.9% respectively. The recovery of mono-PEGylated protein in the pooled eluate from the cuboid packed-bed device was 31.7% greater than that recovered in the pooled eluate from the column. Therefore, significantly higher recovery of mono-PEGylated protein was obtained with the cuboid packed-bed device while maintaining the same purity specification as obtained with the column.

Modelling of electrokinetic phenomena for capture of PEGylated ribonuclease A in a microdevice with insulating structures

Synthesis of PEGylated proteins results in a mixture of protein-polyethylene glycol (PEG) conjugates and the unreacted native protein. From a ribonuclease A (RNase A) PEGylation reaction, mono-PEGylated RNase A (mono-PEG RNase A) has proven therapeutic effects against cancer, reason for which there is an interest in isolating it from the rest of the reaction products. Experimental trapping of PEGylated RNase A inside an electrokinetically driven microfluidic device has been previously demonstrated. Now, from a theoretical point of view, we have studied the electrokinetic phenomena involved in the dielectrophoretic streaming of the native RNase A protein and the trapping of the mono-PEG RNase A inside a microfluidic channel. To accomplish this, we used two 3D computational models, a sphere and an ellipse, adapted to each protein. The effect of temperature on parameters related to trapping was also studied. A temperature increase showed to rise the electric and thermal conductivities of the suspending solution, hindering dielectrophoretic trapping. In contrast, the dynamic viscosity of the suspending solution decreased as the temperature rose, favoring the dielectrophoretic manipulation of the proteins. Also, our models were able to predict the magnitude and direction of the velocity of both proteins indicating trapping for the PEGylated conjugate or no trapping for the native protein. In addition, a parametric sweep study revealed the effect of the protein zeta potential on the electrokinetic response of the protein. We believe this work will serve as a tool to improve the design of electrokinetically driven microfluidic channels for the separation and recovery of PEGylated proteins in one single step.

The Construction of an Aqueous Two-Phase System to Solve Weak-Aggregation of Gigaporous Poly(Styrene-Divinyl Benzene) Microspheres

Gigaporous poly(styrene-divinyl benzene) microspheres made via the surfactant reverse micelles swelling method had a controllable pore size of 100⁻500 nm. These microspheres had unique advantages in biomacromolecule separation and enzymes immobilization. However, the obtained microspheres adhered to each other in the preparation process. Though the weak aggregation could be re-dispersed easily by mechanical force, it will be difficult to scale up. By analyzing the formation mechanism of the aggregates, a method was presented to rebuild the interface between the internal aqueous channel and the external continuous phase by constructing an aqueous two-phase system (ATPS). Based on the ATPS, the method of emulsification, stirring speed, and surfactant concentration in oil phase were optimized. Under the optimum condition (screen emulsification method, 120 rpm for polymerization and 55% surfactant), the microspheres with a controllable particle size of 10⁻40 μm and a pore size of about 150 nm were obtained. This new method could significantly decrease the weak-aggregation of microspheres.

Methods of protein surface PEGylation under structure preservation for the emulsion-based formation of stable nanoparticles

We evaluated different methods for a high surface PEGylation of lysozyme. The resulting lipophilic enzymes can be used for the formation of stable nanoparticles.

Dielectrophoretic behavior of PEGylated RNase A inside a microchannel with diamond-shaped insulating posts

Ribonuclease A (RNase A) has proven potential as a therapeutic agent, especially in its PEGylated form. Grafting of PEG molecules to this protein yields mono-PEGylated (mono-PEG) and di-PEGylated (di-PEG) RNase A conjugates, and the unreacted protein. Mono-PEG RNase A is of great interest. The use of electrokinetic forces in microdevices represents a novel alternative to chromatographic methods to separate this specie. This work describes the dielectrophoretic behavior of the main protein products of the RNase A PEGylation inside a microchannel with insulators under direct current electric fields. This approach represents the first step in route to design micro-bioprocesses to separate PEGylated RNase A from unreacted native protein. The three proteins exhibited different dielectrophoretic behaviors. All of them experienced a marked streaming pattern at 3000 V consistent with positive dielectrophoresis. Native protein was not captured at any of the conditions tested, while mono-PEG RNase A and di-PEG RNase A were captured presumably due to positive dielectrophoresis at 4000 and 2500 V, respectively. Concentration of mono-PEG RNase A with a maximal enrichment efficiency of ≈9.6 times the feed concentration was achieved in few seconds. These findings open the possibility of designing novel devices for rapid separation, concentration, and recovery of PEGylated RNase A in a one-step operation.

Solid-phase polyethylene glycol conjugation using hydrophobic interaction chromatography

PEGylation is a widely applied approach to improve the pharmacokinetic and pharmacodynamic properties of protein therapeutics. The current solution-phase PEGylation protocols often suffer from poor yield of homogeneously PEGylated bioactive products and hence fall short of being commercially attractive. To improve upon these techniques, here we developed a novel, solid-phase PEGylation methodology using a hydrophobic interaction chromatography (HIC) resin. Two variations of the HIC-based PEGylation are described that are tailored towards conjugation of proteins with hydrophobicity index above (lysozyme) and below (fibroblast growth factor 1, FGF-1) that of the mPEG-butyraldehyde (mPEG) chain used. In the case of lysozyme, the protein was first immobilized on the HIC, and the HIC-bound protein was then conjugated by passing over the column. In the case of FGF-1, the mPEG solution was first immobilized on the HIC, and the FGF-1 solution was then passed through the column. Circular dichroism (CD) spectroscopy demonstrated HIC-based PEGylation almost retained the secondary structures of proteins. Bioactivity assay showed that the recovery of activity of HIC-based PEGylated rhFGF-1 (i.e. 92%) was higher than that of liquid-phase PEGylated rhFGF-1 (i.e. 61%), while HIC-based PEGylated lysozyme showed the same activity recovery (i.e. 7%) as the liquid-phase PEGylated form. For specific proteins, the HIC-based solid-phase PEGylation maybe offer a more promising alternative than the current PEGylation methods and is expected to have a major impact in the area of protein-based therapeutics.