Purification and analysis of mono-PEGylated HSA by hydrophobic interaction membrane chromatography

Ultrahigh speed, ultrahigh resolution preparative separation of protein biopharmaceuticals using membrane chromatography

This paper discusses ultrahigh speed, ultrahigh resolution preparative protein separation using an in-house designed membrane chromatography device. The performance of the membrane chromatography device was systematically compared with an equivalent resin-packed preparative column. Experiments carried out using model proteins showed that membrane chromatography gave more than 4-times greater resolution than the preparative column, while at the same time being more than 19-times faster. Membrane chromatography was therefore a better option, not only in terms of higher productivity, but also in terms of higher product purity. Membrane chromatography was also superior in terms of resolving and presenting tracer impurity peaks in the chromatogram. Experiments carried out using monoclonal antibody samples showed that membrane chromatography was suitable to ultrahigh speed, ultrahigh resolution fractionation of charge variants. This paper highlights and explains the need for proper device design for enabling the use of membrane chromatography for efficient purification of protein biopharmaceuticals. This article is protected by copyright. All rights reserved.

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.

Isolation of ellagic acid from pomegranate peel extract by hydrophobic interaction chromatography using graphene oxide grafted cotton fiber adsorbent

Ellagic acid, a natural polyphenol, was isolated from pomegranate peel extract by hydrophobic interaction using graphene oxide grafted cotton fiber as a stationary adsorbent. The grafted graphene oxide moieties served as hydrophobic interaction-binding sites for ellagic acid adsorption. The graphene oxide grafted cotton fiber was made into a membrane-like sheet in order to complete ellagic acid purification by using a binding-elution mode. The effects of operational parameters, such as the composition of the binding buffer/elution buffer, buffer pH, and buffer concentration, on the isolation process were investigated. It was found that 5 mmol/L sodium carbonate aqueous solution is a proper-binding buffer, and sodium hydroxide aqueous solution ranging from 0.04 to 0.06 mol/L is a suitable elution solution for ellagic acid purification. Under the optimized condition, the purity of ellagic acid increased significantly from 7.5% in the crude extract to 75.0-80.0%. The pH value was found to be a key parameter that determines the adsorption and desorption of ellagic acid. No organic solvent is involved in the entire purification process. Thus, a simple and environmentally friendly method is established for ellagic acid purification using a graphene oxide-modified biodegradable and bio-sourced fibrous adsorbent.

PEGylated Human Serum Albumin: Review of PEGylation, Purification and Characterization Methods

Human serum albumin (HSA) is a non-glycosylated, negatively charged protein (Mw: about 65-kDa) that has one free cystein residue (Cys 34), and 17 disulfide bridges that these bridges have main role in its stability and longer biological life-time (15 to 19 days). As HSA is a multifunctional protein, it can also bind to other molecules and ions in addition to its role in maintaining colloidal osmotic pressure (COP) in various diseases. In critical illnesses changes in the level of albumin between the intravascular and extravascular compartments and the decrease in its serum concentration need to be compensated using exogenous albumin; but as the size of HSA is an important parameter in retention within the circulation, therefore increasing its molecular size and hydrodynamic radius of HSA by covalent attachment of poly ethylene glycol (PEG), that is known as PEGylation, provides HSA as a superior volume expander that not only can prevent the interstitial edema but also can reduce the infusion frequency. This review focuses on various PEGylation methods of HSA (solid phase and liquid phase), and compares various methods to purifiy and characterize the pegylated form.

Functionalizing Microporous Membranes for Protein Purification and Protein Digestion

This review examines advances in the functionalization of microporous membranes for protein purification and the development of protease-containing membranes for controlled protein digestion prior to mass spectrometry analysis. Recent studies confirm that membranes are superior to bead-based columns for rapid protein capture, presumably because convective mass transport in membrane pores rapidly brings proteins to binding sites. Modification of porous membranes with functional polymeric films or TiO₂ nanoparticles yields materials that selectively capture species ranging from phosphopeptides to His-tagged proteins, and protein-binding capacities often exceed those of commercial beads. Thin membranes also provide a convenient framework for creating enzyme-containing reactors that afford control over residence times. With millisecond residence times, reactors with immobilized proteases limit protein digestion to increase sequence coverage in mass spectrometry analysis and facilitate elucidation of protein structures. This review emphasizes the advantages of membrane-based techniques and concludes with some challenges for their practical application.

Universal method for the determination of nonionic surfactant content in the presence of protein

A new analytical method has been developed for the quantitative determination of ethylene glycol-containing nonionic surfactants, such as polyethylene glycol 8000, polysorbate 80, and Pluronic F-68. These surfactants are commonly used in pharmaceutical protein preparations, thus, testing in the presence of protein is required. This method is based on the capillary gas chromatographic analysis of ethylene glycol diacetate formed by hydrolysis and acetylation of surfactants that contain ethylene glycol. Protein samples containing free surfactants were hydrolyzed and acetylated with acetic anhydride in the presence of p-toluene sulfonic acid. Acetylated ethylene glycol was extracted with dichloromethane and analyzed by gas chromatography using a flame ionization detector. The amount of nonionic surfactant in the sample was determined by comparing the released ethylene glycol diacetate signal to that measured from calibration standards. The limits of quantitation of the method were 5.0 μg/mL for polyethylene glycol 8000 and Pluronic F-68, and 50 μg/mL for polysorbate 80. This method can be applied to determine the polyethylene glycol content in PEGylated proteins or the final concentration of polysorbate 80 in a protein drug in a quality control environment.

PEGylated human serum albumin (HSA) nanoparticles: preparation, characterization and quantification of the PEGylation extent

Modification with poly(ethylene glycol) (PEG) is a widely used method for the prolongation of plasma half-life of colloidal carrier systems such as nanoparticles prepared from human serum albumin (HSA). However, the quantification of the PEGylation extent is still challenging. Moreover, the influence of different PEG derivatives, which are commonly used for nanoparticle conjugation, has not been investigated so far. The objective of the present study is to develop a method for the quantification of PEG and to monitor the influence of diverse PEG reagents on the amount of PEG linked to the surface of HSA nanoparticles. A size exclusion chromatography method with refractive index detection was established which enabled the quantification of unreacted PEG in the supernatant. The achieved results were confirmed using a fluorescent PEG derivative, which was detected by photometry and fluorimetry. Additionally, PEGylated HSA nanoparticles were enzymatically digested and the linked amount of fluorescently active PEG was directly determined. All the analytical methods confirmed that under optimized PEGylation conditions a PEGylation efficiency of up to 0.5 mg PEG per mg nanoparticle could be achieved. Model calculations made a 'brush' conformation of the PEG chains on the particle surface very likely. By incubating the nanoparticles with fetal bovine serum the reduced adsorption of serum proteins on PEGylated HSA nanoparticles compared to non-PEGylated HSA nanoparticles was demonstrated using sodium dodecylsulfate polyacrylamide gel electrophoresis. Finally, the positive effect of PEGylation on plasma half-life was demonstrated in an in vivo study in mice. Compared to unmodified nanoparticles the PEGylation led to a four times larger plasma half-life.