Hydrophobic chromatography on homologous series of alkylagaroses

Practical method development for the separation of monoclonal antibodies and antibody-drug-conjugate species in hydrophobic interaction chromatography, part 1: optimization of the mobile phase

The goal of this work is to provide some recommendations for method development in HIC using monoclonal antibodies (mAbs) and antibody-drug conjugates (ADCs) as model drug candidates. The effects of gradient steepness, mobile phase pH, salt concentration and type, as well as organic modifier were evaluated for tuning selectivity and retention in HIC. Except the nature of the stationary phase, which was not discussed in this study, the most important parameter for modifying selectivity was the gradient steepness. The addition of organic solvent (up to 15% isopropanol) in the mobile phase was also found to be useful for mAbs analysis, since it could provide some changes in elution order, in some cases. On the contrary, isopropanol was not beneficial with ADCs, since the most hydrophobic DAR species (DAR6 and DAR8) cannot be eluted from the stationary phase under these conditions. This study also illustrates the possibility to perform HIC method development using optimization software, such as Drylab. The optimum conditions suggested by the software were tested using therapeutic mAbs and commercial cysteine linked ADC (brentuximab-vedotin) and the average retention time errors between predicted and experimental retention times were ∼ 1%.

Effect of phenyl sepharose ligand density on protein monomer/aggregate purification and separation using hydrophobic interaction chromatography

In the large-scale manufacturing and purification of protein therapeutics, multiple chromatography adsorbent lots are often required due to limited absorbent batch sizes or during replacement at the end of the useful column lifetime. Variability in the adsorbent performance from lot to lot should be minimal in order to ensure that consistent product purity and product quality attributes are achieved when a different lot or lot mixture is implemented in the process. Vendors of chromatographic adsorbents will often provide release specifications, which may possess a narrow range of acceptable values. Despite relatively narrow release specifications, the performance of the adsorbent in a given purification process could still vary from lot to lot. In this case, an alternative use test (one that properly captures the lot to lot variability) may be required to determine an acceptable range of variability for a specific process. In this work, we describe the separation of therapeutic protein monomer and aggregate species using hydrophobic interaction chromatography, which is potentially sensitive to adsorbent lot variability. An alternative use test is formulated, which can be used to rapidly screen different adsorbent lots prior to implementation in a large-scale manufacturing process. In addition, the underlying mechanism responsible for the adsorbent lot variability, which was based upon differences in protein adsorption characteristics, was also investigated using both experimental and modeling approaches.

Hydrophobic interaction chromatography of proteins. II. Binding capacity, recovery and mass transfer properties

Hydrophobic interaction chromatography media suited for large scale separations were compared regarding dynamic binding capacity, recovery and mass transfer properties. In all cases, pore diffusion was the rate limiting step. Reduced heights equivalent to a theoretical plate for bovine serum albumin derived from breakthrough curves at reduced velocities between 60 and 1500 ranged from 10 to 700. Pore diffusion coefficients were derived from pulse response experiments for the model proteins alpha-lactalbumin, lysozyme, beta-lactoglobulin, bovine serum albumin and immunoglobulin G. Diffusivity of lysozyme did not follow the trend of decreasing diffusivity with increasing molecular mass, as observed for the rest of the proteins. In general, mass transfer coefficients were smaller compared to ion-exchange chromatography. Dynamic binding capacities for the model protein bovine serum albumin varied within a broad range. However, sorbents based on polymethacrylate showed a lower dynamic capacity than media based on Sepharose. Some sorbents could be clustered regarding binding capacity affected by salt. These sorbents exhibited a disproportional increase of binding capacity with increasing ammonium sulfate concentration. Recovery of proteins above 75% could be observed for all sorbents. Several sorbents showed a recovery close to 100%.

Cyanogen bromide and tresyl chloride chemistry revisited: the special reactivity of agarose as a chromatographic and biomaterial support for immobilizing novel chemical groups

The cyanogen bromide and tresyl chloride (2,2,2-trifluoroethanesulfonyl chloride) methods belong to the best-known activation procedures for solid supports in biochemistry. In both cases the originally proposed reaction mechanisms were revised many years later. In this paper important aspects of these two major activation reactions in connection with the singular polysaccharide support, agarose, will be treated with emphasis on the novel reaction mechanism recently proposed for tresyl chloride. In addition, the special role played by sulfur in the new uncharged alkyl-S-S-gels is examined in connection with the phenomenon of base-atom recognition.

Manufacture of recombinant proteins with safe and validated chromatographic sorbents

Purification of recombinant proteins to achieve homogeneity, purity, consistency and potency as required for therapeutic proteins and in vivo diagnostics is performed under stringent and validated conditions. As liquid chromatography is one of the major technologies used for this purpose, it has to be carried out according to special regulatory guidelines. One of the reported aspects is the long-term consistency of a chromatographic process and validation of its operation; other aspects described are more sorbent oriented. In-place cleaning and sterilization are also very important aspects, the efficiency of which is dependent on the chosen working conditions and the chemical nature of the sorbents. Drastic cleaning may deteriorate the chromatographic matrices, releasing chemicals that may contaminate the biologicals of interest, which modifying the behaviour of the chromatographic columns. Moreover, leachable compounds, when present, could have adverse effects in case of high toxicity. Determination of leaching levels and toxicity tests are part of the validation steps to turn chromatographic separations into consistent, effective and safe production processes for biologicals.

The effect of hydrophobic interaction on endotoxin adsorption by polymeric affinity matrix

Endotoxin, a major pyrogen of concern to the biological industry, is a lipopolysaccharide containing a highly hydrophobic region, lipid A, in its structure. The effect of hydrophobic interaction on endotoxin adsorption from an aqueous solution was studied by covalently bonding aminoalkyl groups with varying hydrocarbon lengths to a cellulose and acrylic composite matrix. The amount of endotoxin adsorbed on the matrix increased with the increasing length of alkyl groups, demonstrating the contribution of hydrophobic interaction between endotoxin and the solid matrix. Both the hydrophobic and the charge interaction prove to be effective for endotoxin adsorption, and a synergistic effect from the dual chemical forces is achievable under specified conditions. The effect of solvent, pH and salts on endotoxin adsorption provides further evidence for the importance of hydrophobic force as a means of removing endotoxin from aqueous solutions.

Protein chromatography with pyridine- and alkyl-thioether-based agarose adsorbents

In an attempt to identify the part of the ligand of 3-(2-pyridylthiol)-2-hydroxypropylagarose that is responsible for the specific adsorption of immunoglobulins and alpha 2-macroglobulin from serum, nine agarose derivatives were prepared: (I) 3-(N-2-iminopyridyl)-2-hydroxypropyl-, (II) 3-(4-pyridylthio)-2-hydroxypropyl-, (III) 3-(2-pyridylthio-N-oxide)-2-hydroxypropyl-, (IV) 3-(2-pyridylthio)-2-hydroxypropyl-, (V) 3-(ethylthio)-2-hydroxypropyl-, (VI) 3-(n-butylthio)-2-hydroxypropyl-, (VII) 3-(2-aminoethylthio)-2-hydroxypropyl-, (VIII) 3-(2-hydroxyethylthiol)-2-hydroxypropyl- and (IX) 3-(N-2-pyridyl-2-one)-2-hydroxypropylagarose. The selective adsorption of the above serum proteins to these derivatives was analysed by chromatography. The electron distributions were calculated for three of the investigated pyridine derivatives in order to establish whether there is any relationship between the electron distribution in the molecule and the absorption properties of the pyridine derivatives. By optimizing the preparation methods for the different derivatives, the possible side-reactions were minimized and checked. The adsorbed serum proteins were determined by the Ouchterlony technique and electrophoresis. The concentration of human serum albumin in the different fractions was determined by conventional radioimmunological methods. These data make it possible to classify the adsorbents according to their selectivity and hydrophobic thiophilic behaviour.

Synthesis of new hydrophobic adsorbents based on homologous series of uncharged alkyl sulphide agarose derivatives

A homologous series of uncharged thioalkyl derivatives of agarose were prepared by a simplified synthetic route and their adsorption behaviour towards human serum proteins was evaluated and compared with that of a commercially available alkyl ether derivative of agarose. The influence of the spacer arm length on the adsorption efficiency was also investigated. The degree of substitution of the derivatives can be estimated conveniently by sulphur analysis. The four different types of thiolkyl derivatives (C6, C8, C12 and C14) investigated here behave in all respects like hydrophobic adsorbents. The coupling yield obtained is high (75% or more) and is better than that obtained by alternative synthetic routes reported so far. The adsorption capacity towards serum proteins of the various derivatives increases with increasing alkyl chain length and degree of substitution. Desorption is achieved by a progressive decrease in the polarity of the eluent and the recovery of the applied material is in the range 80-90%. The role played by the thioether as a possible modulator of the observed hydrophobic adsorption is discussed. For the group separation of serum proteins the optimum adsorbent, as regards capacity combined with ease of elution of adsorbed material, should be substituted with chains of six or eight carbon atoms and have a ligand concentration in the range 80-120 mumole g-1 dry gel.

Hydrophobic chromatography of cells: adsorption and resolution on homologous series of alkylagaroses

Implantation of hydrocarbon chains on beaded agarose results in column materials capable of adsorbing erythrocytes or lymphocytes from various sources. In a homologous series of such columns, identical in all structural respects (ligand density, charge density and ultrastructure) except for the length of their hydrocarbon chains, the capacity to adsorb these cells generally increases with increase in the number of carbon atoms per chain. The cells can be desorbed from the columns by repeated gentle pipetting in the presence of bovine serum albumin (for erythrocytes) or foetal calf serum (for lymphocytes). Under the conditions used for adsorption and desorption there is neither physical entrapment of the cells in the column nor apparent damage to their integrity, as indicated by the facts that (a) 95-98% of the cells applied on the column can be recovered; (b) erythrocytes eluted from the column and those yet to be applied are morphologically indistinguishable, exhibit an identical osmotic fragility profile and, (after desorption) retain the same adsorption profile for the columns; and (c) over 95% of the mouse spleen lymphocytes, eluted from the columns, continue to exclude the dye Trypan blue, suggesting that they preserve their viability. Cells from different sources exhibit different adsorption profiles on homologous series of alkylagaroses, allowing the detection of differences in the surface of these cells and their resolution by these columns. Exploratory experiments with artificial cell mixtures are described, illustrating the possibility of enriching the mixture with one of the cell types by preferential adsorption or exclusion on an appropriate alkylagarose. The best resolution was obtained with a mixture of erythrocytes and spleen lymphocytes (both from DBA/1 mice). After appropriate "tailoring" of the column material used (an ethylagarose) it was possible to apply a 1:1 mixture of these cells and to obtain (after preferential adsorption) essentially pure erythrocytes (98% of the excluded cells).(ABSTRACT TRUNCATED AT 400 WORDS)

Wide-pore silica-based ether-bonded phases for separation of proteins by high-performance hydrophobic-interaction and size-exclusion chromatography

This paper examines the use of wide-pore silica-based hydrophilic ether-bonded phases for the chromatographic separation of proteins under mild elution conditions. In particular, ether phases of the following structure identical to Si-(CH2)3-O-(CH2-CH2-O)n-R, where n = 1, 2, 3 and R = methyl, ethyl or n-butyl, have been prepared. These phases can be employed either in high-performance hydrophobic-interaction or size-exclusion chromatography, depending on mobile phase conditions. In the hydrophobic-interaction mode, a gradient of decreasing salt concentration, e.g., from 3 M ammonium sulfate (pH 6.0, 25 degrees C), yields sharp peaks with high mass recovery of active proteins. In this mode, retention can be controlled by salt type and concentration, as well as by column temperature. In the size-exclusion mode, use of medium ionic strength, e.g., 0.5 M ammonium acetate (pH 6.0) yields linear calibration of log (MW[eta]) vs. retention volume. Even at 0.05 M salt concentration, no stationary phase charge effects on protein elution are observed. These bonded-phase columns exhibit good column-to-column reproducibility and constant retention for at least five months of continual use. Examples of the high-performance separation of proteins in both modes are illustrated.

A study on the separation of reconstituted proteoliposomes and unincorporated membrane proteins by use of hydrophobic affinity gels, with special reference to band 3 from bovine erythrocyte membranes

Alkyl-Sepharose 4B with octyl, decyl, or dodecyl groups as an alkyl chain was a good adsorbent for any type of detergents and a variety of proteins, but not for phospholipids in a vesicle form. When these gels were added to the mixtures of reconstituted proteoliposomes prepared by using bovine band 3 and the protein unincorporated into liposomes, free band 3 in solution was adsorbed onto the gels and the proteoliposomes could be recovered by filtration, suggesting that this procedure, when applicable, permits a rapid isolation of proteoliposomes without loss and dilution of the sample. In addition, the results indicated that Bio-Beads SM-2 resin, which is virtually nonadsorbing for most proteins, can be used in removing any kind of detergents from those protein-detergent mixtures.