WO2014067605A1 - Surface modification of porous base supports - Google Patents
Surface modification of porous base supports Download PDFInfo
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- WO2014067605A1 WO2014067605A1 PCT/EP2013/002967 EP2013002967W WO2014067605A1 WO 2014067605 A1 WO2014067605 A1 WO 2014067605A1 EP 2013002967 W EP2013002967 W EP 2013002967W WO 2014067605 A1 WO2014067605 A1 WO 2014067605A1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/281—Sorbents specially adapted for preparative, analytical or investigative chromatography
- B01J20/282—Porous sorbents
- B01J20/283—Porous sorbents based on silica
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D15/00—Separating processes involving the treatment of liquids with solid sorbents; Apparatus therefor
- B01D15/08—Selective adsorption, e.g. chromatography
- B01D15/26—Selective adsorption, e.g. chromatography characterised by the separation mechanism
- B01D15/38—Selective adsorption, e.g. chromatography characterised by the separation mechanism involving specific interaction not covered by one or more of groups B01D15/265 - B01D15/36
- B01D15/3804—Affinity chromatography
- B01D15/3809—Affinity chromatography of the antigen-antibody type, e.g. protein A, G, L chromatography
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/281—Sorbents specially adapted for preparative, analytical or investigative chromatography
- B01J20/286—Phases chemically bonded to a substrate, e.g. to silica or to polymers
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/281—Sorbents specially adapted for preparative, analytical or investigative chromatography
- B01J20/286—Phases chemically bonded to a substrate, e.g. to silica or to polymers
- B01J20/289—Phases chemically bonded to a substrate, e.g. to silica or to polymers bonded via a spacer
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/30—Processes for preparing, regenerating, or reactivating
- B01J20/3085—Chemical treatments not covered by groups B01J20/3007 - B01J20/3078
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/30—Processes for preparing, regenerating, or reactivating
- B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
- B01J20/3202—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the carrier, support or substrate used for impregnation or coating
- B01J20/3204—Inorganic carriers, supports or substrates
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/30—Processes for preparing, regenerating, or reactivating
- B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
- B01J20/3214—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the method for obtaining this coating or impregnating
- B01J20/3217—Resulting in a chemical bond between the coating or impregnating layer and the carrier, support or substrate, e.g. a covalent bond
- B01J20/3219—Resulting in a chemical bond between the coating or impregnating layer and the carrier, support or substrate, e.g. a covalent bond involving a particular spacer or linking group, e.g. for attaching an active group
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/30—Processes for preparing, regenerating, or reactivating
- B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
- B01J20/3214—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the method for obtaining this coating or impregnating
- B01J20/3225—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the method for obtaining this coating or impregnating involving a post-treatment of the coated or impregnated product
- B01J20/3227—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the method for obtaining this coating or impregnating involving a post-treatment of the coated or impregnated product by end-capping, i.e. with or after the introduction of functional or ligand groups
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/30—Processes for preparing, regenerating, or reactivating
- B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
- B01J20/3231—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the coating or impregnating layer
- B01J20/3234—Inorganic material layers
- B01J20/3236—Inorganic material layers containing metal, other than zeolites, e.g. oxides, hydroxides, sulphides or salts
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/30—Processes for preparing, regenerating, or reactivating
- B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
- B01J20/3231—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the coating or impregnating layer
- B01J20/3242—Layers with a functional group, e.g. an affinity material, a ligand, a reactant or a complexing group
- B01J20/3268—Macromolecular compounds
- B01J20/3278—Polymers being grafted on the carrier
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F292/00—Macromolecular compounds obtained by polymerising monomers on to inorganic materials
Definitions
- the present invention relates to new separation materials with improved binding capacity, its manufacturing, and use, especially for binding protein A.
- Protein A is initially a 56 kDa surface protein originally found in the cell wall of the bacterium Staphylococcus aureus. It is encoded by the spa gene and its regulation is controlled by DNA topology, cellular osmolarity, and a two- component system called ArlS-ArlR. It has found use in biochemical research because of its ability to bind immunoglobulins. It is originally composed of five homologous Ig-binding domains that fold into a three-helix bundle.
- Each domain is able to bind proteins from many mammalian species, most notably IgGs. It binds the heavy chain within the Fc region of most immunoglobulins and also within the Fab region in the case of the human VH3 family. Through these interactions in serum, where IgG molecules are bound in the wrong orientation (in relation to normal antibody function), the bacteria disrupts opsonization and phagocytosis.
- Protein A and “Prot A” are used interchangeably and encompasses Protein A recovered from a native source thereof, Protein A produced synthetically (e.g., by peptide synthesis or by recombinant techniques), and variants thereof which retain the ability to bind proteins which have a CH 2 /CH 3 region, such as an Fc region.
- Protein A can be purchased commercially from Repligen, GE or Fermatech. Protein A is generally immobilized on a chromatography matrix.
- An interaction compliant with such value for the binding constant is termed "high affinity binding" in the present context.
- such functional derivative or variant of Protein A comprises at least part of a functional IgG binding domain of wild-type Protein A, selected from the natural domains E, D, A, B, C or engineered mutants thereof which have retained IgG binding functionality.
- Protein A derivatives or variants engineered to allow a single-point attachment to a solid support may also be used in the affinity
- Single point attachment generally means that the protein moiety is attached via a single covalent bond to a chromatographic support material of the Protein A affinity chromatography. Such single-point attachment may also occur by use of suitably reactive residues which are placed at an exposed amino acid position, namely in a loop, close to the N- or C-terminus or elsewhere on the outer circumference of the protein fold. Suitable reactive groups are e.g. sulfhydryl or amino functions.
- Protein A derivatives of variants are attached via multi-point attachment to suitable a chromatography matrix.
- Protein A affinity chromatography is one of the most crucial purification steps in the downstream processing of monoclonal antibodies mAbs.
- the crude multi-component solution passes through a column packed with a stationary phase comprising immobilized protein A on a solid porous support.
- the desired mAb is captured by specific interactions between mAb and protein A while the impurities leave the column together with the leaving solvent.
- the captured mAb is recovered by usage of an appropriate eluant [P. Cuatrecasas, M. Wilchek, C. B. Anfinsen, Proc. Natl. Acad. Sci. USA, 61 , 636 (1968)].
- this bind and elute operation consists of a sequence of several steps.
- the column is washed with the buffer in which the target molecule containing feed-stream will be loaded.
- feed stream containing target mAb and impurities
- the column containing protein A stationary phase.
- the target mAb molecule is captured by the virtue of its specific affinity towards protein A, while the impurities mostly pass through.
- the stationary protein A phase is flushed with the washing buffer to remove remaining impurities.
- the captured mAb molecules are recovered (eluted) by passing elution buffer through the column.
- the elution of mAb is caused by the chemical environment generated by the elution buffer, which induces a shift in affinity between target mAb molecule and protein A.
- the column is finally cleaned and regenerated for repeat bind and elute of mAb for several more cycles.
- affinity chromatography relies on very specific bonding interactions between target mAb and the surface of stationary phase. Ideally this specific binding should occur in such a way that every component of the starting mixture without substantial affinity to the surface passes through the chromatographic column, while the desirable molecule is retained.
- Various physiochemical interactions including electrostatic, hydrophobic, van der Waals and hydrogen bonding, the nature of the medium carrying the starting mixture, the complementary arrangement of the target molecule and the binding sites on the surface of the resin are typically responsible for a desired biospecifity [K. Huse, H.-J. Bohme and G.H. Scholz, J. Biochem.
- Protein A is a successfully applied and well proved affinity ligand for the capture of monoclonal immunoglobulin G antibodies.
- Affinity chromatography for industrial applications consists of four stages: adsorption, washing, elution, regeneration [S.R. Narayanan, J.
- the high specifically bindings of mAb to immobilized protein A in affinity chromatography for purification of mAb is caused by interactions with the fragmental crystallisable (FC) regions of mAb and appropriate sites of protein A.
- Protein A originates from the bacteria Staphylococcus aureus and has actually the purpose to protect the bacteria from mammal's immune systems while binding IgG on a way that makes it inoperative. This skill is basically utilized, using protein A as affinity chromatography ligand. Protein A has five structurally related, homologous domains which can all bind to respective FC region of IgG [K. Huse, H.-J. Bohme and G.H. Scholz, J. Biochem. Biophys. Methods, 2002, 51 , 217; S.
- Proteins are macromolecules and their activity is based on tertiary structures (e.g. FC region) so that their orientation in space and conditions like the media's pH are important influencing parameters for successfully complex building between ligand and target molecule - in this case between protein A and IgG. But the requirement of an appropriate, specific binding environment is on the other hand the key for the detachment during elution.
- the complex building of IgG FC region with protein A requires an appropriate orientation in pores.
- the difference in size dimensions is based on the molecular weight of both proteins, IgG (144 kDa) is significant bigger than protein A (40 -60 kDa).
- Multiple-point attachment compared with one-point attachment, for example, promises an improvement of durability of protein A immobilization to prevent any protein A leaching during mAb purification.
- Thiols are generally more reactive than amines due to their stronger nucleophilic nature so that thiol containing protein A can be immobilized very efficiently on epoxy groups providing surfaces.
- the efficiency of the protein A medium is generally measured in terms of the binding capacity (in static or dynamic mode) per unit volume of the resin.
- the binding capacity is a function of the physical attributes of the porous beads, such as surface area, pore size, pore volume, and bead size.
- surface area provides more functional groups per unit volume for attachment of protein A, and in turn, can increase the binding capacity.
- increasing surface area may come at the cost of mechanical stability of the porous beads packed in a column.
- the mechanically stability is necessary for the porous beads to withstand the operating flow rates and resulting pressure, because it is economical to operate at high flow rates as compared to low flow rates at the same dynamic binding capacity.
- high rates cause dense packing of porous beads in the columns, and high pressure drops. From this point of view, it is desirable to use a material that has uniform particle size and narrow pore size distribution, and therefore, allows accurate packing.
- Particles with small pore diameter usually provide high surface areas.
- the pore size needs to be sufficient to allow diffusion of the biomolecules. Beside these physical attributes, the support material should also possess several chemical attributes. Because protein A chromatography operates on the principle of selective affinity between the desired molecule and the stationary phase, the stationary phase should ideally lack any potential of interaction (typically referred to as non-specific adsorptive interaction or binding) with the desired molecule. [A. Jungbauer, G. Carta, in: Protein Chromatography, Process Development and Scale-Up; WILEY-VCH Verlag, Weinheim (Germany) 2010]
- a porous agarose gel can be prepared by cooling a hot agarose solution.
- Primary feature of those materials is their hydrophilic character (low non-specific adsorption) and the accessibility to a high amount of hydroxyl groups for chemical modification and ligand immobilization so that high capacities are reachable.
- carbohydrates are chemically resistant at extreme alkaline conditions, and therefore suitable for CI P.
- these agarose-based materials lack mechanical stability restricting their use at very high flow rates and pressure.
- the mechanical stability of these materials can be improved by chemical crosslinking.
- chemical crosslinking typically use the hydroxyl groups as handles, limiting the extent to which the agarose gel can be crosslinked without sacrificing the hydroxyl groups available as handles for further ligand immobilization.
- the mechanical strength of these crosslinked agarose gels may not match competitive materials like inorganic materials.
- Porous synthetic polymer beads are also used as stationary phase for affinity chromatography.
- These synthetic polymer beads of desired particle sizes are usually prepared by suspension or emulsion polymerization using a judiciously chosen porogen, which also yields high surface areas. This suspension
- polymerization typically involves seeding a radical polymerization of a monomer with porogen, and has been proven to yield narrow distribution of particle sizes [T. Ellingsen, O. Aune, J. Ugelstad and S. Hagen, J. Chromatogr., 1990, 535, 147].
- synthetic polymers can be significantly more hydrophobic than natural carbohydrate polymers.
- polymer beads can also provide a high density of functional groups, available for surface
- HEMA 2-Hydroxyethyl methacrylate
- a third class of supporting materials is inorganic, or ceramic, particles.
- Particles of that class are for example so called controlled pore glass (CPG) particles.
- Figure 1 shows such particles and their pore structure.
- Silica based beads such as CPG as commercialized by Merck Millipore, have the highest solid density, and offer excellent mechanical strength.
- CIP is the main limitation in using inorganic supporting materials such as CPG [M. Rogers, M. Hiraoka-Sutow, P. Mak, F. Mann and B. Lebreton, J.
- each of the base matrices provides one or more advantages for protein A affinity media, but the most desirable improvement is in the caustic stability of CPG.
- the object of the present invention are separating materials for affinity chromatography based on hydroxyl-containing porous base supports, to the surfaces of which polymer chains are grafted by covalent bonding, in that a) two or more grafted polymer chains are initiated from one hydroxyl group on the surface, and that
- the porous base material for the production of the separating material may consist of a porous ceramic medium or a porous polymer support having hydroxyl groups at the surface.
- Suitable porous ceramic media as base support may comprise oxides of silicium, zirconium titanium, and their mixtures. Experiments have shown, that the new separating materials show good properties if the porous base support is a silica based porous medium or if the silica based porous medium is coated with zirconia or titanium oxide.
- separating materials for affinity chromatography with improved properties are provided by materials which are treated in a first production step with a tri- or more functional epoxide. Under suitable conditions the reacted tri- or more functional epoxides form a crosslinked coating rich in epoxy functionality.
- an improved separating material can be produced, comprising a porous base support covered with a crosslinked coating rich in aliphatic hydroxyl or diol groups for covalent bonding of graft polymer chains comprising acrylic acid or its derivative providing carboxylic acid groups.
- Particularly suitable separating material according to the invention are those in which a porous base support is covered with a crosslinked coating rich in aliphatic hydroxyl or diol groups for covalent bonding of graft polymer chains by surface initiated polymerization of monomers selected from the group glycidyl methacrylate, vinyl azlactone, acrylic acid /V-hydroxysuccinimide ester, methacrylic acid N-hydroxysuccinimide ester, providing reactive groups for further functionalization.
- inventive separating materials wherein the porous base support is covered with a crosslinked coating rich in aliphatic hydroxyl or diol groups for covalent bonding of graft polymer chains built of acrylic acid or its derivative and a further monomer providing carboxylic acid groups and if each polymer chain of the separating material possesses multiple derivatizable groups for coupling protein A.
- protein A is coupled to reactive groups of the grafted polymer chains.
- hydrophobic monomers comprising linear or branched alkyl, aryl, alkylaryl, arylalkyl having up to 18 carbon atoms, which optionally contain hydrophilic groups selected from the group consisting of alkoxy, cyano, carboxy, acetoxy and acetamino.
- Separating materials for affinity chromatography of the present invention are prepared in a process characterised in that a porous base support medium is a) reacted with a trifunctional epoxide,
- step a) graft polymerized with chains comprising acrylic acid or its derivative providing carboxylic acid groups onto the coating of step a), which is rich in aliphatic hydroxyl or diol groups
- c) protein A is coupled to reactive groups of the grafted polymer chains.
- a porous silica base support medium is coated with zirconium oxide or titanium oxide before reacting with a multifunctional epoxide, especially with a tri- or more functional epoxide, to improve the caustic stability of the produced separating material.
- a further object of the present invention are chromatography columns, containing a separating material as disclosed here and their use for the removal of biopolymers from liquid media.
- inventive separating materials are suitable for use in affinity chromatography, whereby the biopolymer is adsorbed to the separating material by interaction with coupled protein A and /or the ionic groups of grafted polymer chains and optionally with hydrophobic groups and is desorbed either by
- Protein A possesses different reactive groups which can be used for immobilization on a suitable carrier.
- Thiols or amines are common functional groups of protein A for reaction [H. Ahmed, Principles and Reactions of
- amine containing ligands are coupled to the carrier surface by hydroxyl groups, using reagents, such as, cyanogen bromide, oxiranes, tresyl chloride, divinylsulfone, benzoquinone carbodiimidazole.
- reagents such as, cyanogen bromide, oxiranes, tresyl chloride, divinylsulfone, benzoquinone carbodiimidazole.
- the metal oxides need to be activated to increase the amount of surface hydroxyls.
- Methods concerning this issue are described in literature, applying common chemical treatments with mineral acids, sodium hydroxide or plasma.
- Zirconia lacks the modifiable surface hydroxyl groups and further surface activations is desirable to increase the chance of homogenously polymer grafting.
- TMTGE offers the possibility of building up a crosslinked horizontal network due to its epoxy residues in order to cover surfaces that lack modifiable hydroxyl groups, and to make them accessible for grafting polymerization.
- the already synthesized polymer reacts via one or multiple anchor groups with reactive groups on the surface.
- Main feature of this technique is the option to use tailor made chains with desirable molecular weight and weight distribution as well as composition of copolymers, block co-polymers or other special polymer architectures [Huang, J., Koepsel, R. R., Murata, H., Lee, S. B., Kowalewski, T., Russell, A. J., Matyjaszewski, K.;Langmuir, 2008, 24, 6785].
- the initiation of polymerization is located at the solid surface so that the polymer chains grow up from the solid matrix by conventional
- the grafting-from technique allows for high grafting density of polymer chains as compared to grafting-to technique because of easier mass transfer of small monomers as compared to the long polymer chains that need to access the reactive sites in the surface through the continuously building polymer layer. With high enough graft density, polymer chains extend away from the surface due to the repulsion between the neighboring chains to form a "polymer brush".
- ATRP and Ce(IV)-initiated polymerization were adapted to the grafting polymerization due to their unique advantages: while ATRP is a well-controlled polymerization method, Ce(IV) is simple and can be directly performed from the surface with hydroxyl groups. Controlled radical polymerization combines the benefits of living
- Radicals are generated by reversible atom transfer of a halogen atom X from the alkyl halide (dormant species) to the transition metal complex M x (L) y .
- alkyl halide dispermant species
- M x (L) y transition metal complex
- Termination reactions are promoted by high radical concentration, and therefore, the concentration of active species needs to be regulated.
- activator generated by electron transfer atom transfer radical polymerization (AGET ATRP).
- GAT ATRP electron transfer atom transfer radical polymerization
- the transition metal in the oxidation stage that allows the atom transfer for activation is generated in situ using a reducing agent.
- AGET ATRP Principle of AGET ATRP is shown by Jakubowski, W., et al.
- AGET ATRP can be easily used for grafting from polymerization by the immobilization of an ATRP initiator on substrate surface.
- Substrates need to provide appropriate anchor functionality to immobilize initiator molecules, even polymers including respective halides can be used such as polyvinyl benzyl chloride) so that no immobilization is necessary in this case.
- ATRP has been successfully applied to various monomers, containing substituents which can stabilize the propagating radicals, such as styrenes, (meth)acrylates, (meth)acrylamides, dienes and acrylonitrile. Due to the chemical nature, each monomer causes a unique equilibrium rate so that optimized polymerization conditions are not easily transferable. Acidic monomers like (meth)acrylic acid can poison the catalyst by coordinating to the transition metal. They can also protonate nitrogen containing ligands, which interferes with the metal complexation ability.
- ATRP initiators are alkyl halides including halogenated alkanes, benzylic halides, a-haloester, a- haloketones, a-halonitriles and sulfonyl halides. Structural resemblance of monomer and initiator are beneficial so that a-bromoisobutyrates (A) are good initiators for the ATRP of methacrylates (B), while a-bromoproptionates (C) are used for the polymerization of acrylates (D).
- A a-bromoisobutyrates
- B methacrylates
- C a-bromoproptionates
- the initiator is supposed to be immobilized on the substrate surface. According numerous reports, the immobilization succeeds using suitable silane chlorides (E), alkoxysilanes (F) on silica surfaces or a-bromo isobutyryl bromide (G) on any hydroxyl groups providing substrate
- catalyst systems for ATRP are described in literature, including transition metals from 6 th to 11 th group of periodic table of the elements. Of all the transition metals, copper catalysts are the most propagated, superior in terms of versatility and costs. Besides the transition metal species, for a working catalyst system is also a suitable ligand required which usually promotes solubility as well as the activity of the catalyst. Multidentate aliphatic amines are established as ligands for copper catalyzed ATRP; 2,2'- bipyridine (Bpy) and ⁇ /, ⁇ /, ⁇ /', ⁇ /', ⁇ /''-pentamethyl-diethylenetriamine (PMDETA) are common ligands for copper complexes in ATRP.
- Bpy 2,2'- bipyridine
- PMDETA ⁇ /, ⁇ /, ⁇ /', ⁇ /', ⁇ /''-pentamethyl-diethylenetriamine
- ATRP As mentioned before, the crucial distinction of ATRP to AGET ATRP is the application of a reducing agent to generate activating transition metal complexes in situ. In copper based systems, this means the in situ
- reducing agent e.g. tin (I I) species (e.g. thin(ll) 2- ethylhexanoate), phenols, glucose, hydrazine, gallate, and ascorbic acid.
- I I tin species
- phenols e.g. glucose, hydrazine, gallate, and ascorbic acid.
- the initiation of polymerization may also be caused by a cerium(IV) salt, such as, cerium ammonium nitrate.
- a cerium(IV) salt such as, cerium ammonium nitrate.
- the reaction is based on the release of free radicals as a consequence of a redox reaction, first described in 1958 by G. Mino and S. Kaizerman [Mino, G., Kaizerman, S., J. Polym. Sci., 1958, 31 , 242].
- the oxidation-reduction system usually consists of the cerium salt and an organic reducing agent such as alcohols, thiols, glycols, aldehydes, and amines.
- grafting polymerization from hydroxyl groups with Ce(IV) salts is described for numerous vinyl monomers, where the chain growth is initiated by the generated radical. Mechanism and kinetic is similar to a free radical polymerization, including termination and transfer reactions. Compared with free radical polymerization in solution, the surface initiated version usually shows increased terminations caused by high local radical concentration. Typical substrates are polyvinyl alcohol), cellulose, starch, and other natural carbohydrates. The general process brings the benefit of high robustness compared with other surface initiated polymerization. Furthermore, compared with SI ATRP, no specialized initiator needs to be immobilized in a separate reaction step for Ce(IV) initiated graft polymerization. In addition, the polymerization of acidic monomer is easily possible, even ideal because the Ce(IV) initiation is typically performed in acidic aqueous media.
- proteins and especially monoclonal antibodies unfortunately are obtained from cell cultures in low concentrations and with a high amount of impurities.
- exceptional purities are necessary if these compounds are desired products for pharmaceutical applications.
- mAbs monoclonal antibodies
- the set of the complex isolation and purification steps for recovery of proteins is generally referred to as downstream processes [R. Freitag and C. Horvath, Adv. Biochem. Eng./Biotechnol., 1996, 53, 17].
- protein A chromatography (also referred to as affinity chromatography) is one of the most crucial steps in mAb purification due to high specific affinity of protein A to mAbs.
- the crude multi-component solution passes through a column packed with a stationary phase with immobilized protein A.
- the desired mAb is captured by specific interactions between mAb and protein A while the impurities leave the column with the solvent. Afterwards the captured mAb is recovered by usage of an appropriate eluant [P. Cuatrecasas, M. Wilchek and C.B. Anfinsen, Proc. Natl. Acad. Sci. U. S. A., 1968, 61 , 636 ].
- carbohydrate polymers e.g. agarose, cellulose
- - inorganic materials e.g. silica, porous glass, zirconia oxide or titanium oxide.
- each material shows several advantages and disadvantages.
- inorganic materials like porous glass are preferred because of their high rigidity in comparison to the polymeric competitors. They offer constancy in shape and pore size while increasing the flow rate and consequently the pressure. Large pores, well defined and variable in diameter, together with excellent flow properties, despite their non-spherical shape allow controlled pore glass (CPG) the application as protein A resin in large scale therapeutic antibody purification, but the challenge is its lack of caustic stability this inorganic porous separation material.
- CPG controlled pore glass
- the success of particle modification is primarily measured by ligand density LD B CA and the static binding capacity Q s for Immunoglobulin G.
- cerium(IV)salt initiation and by surface initiated activator generated by electron transfer atom transfer radical polymerization SI AGET ATRP
- Si AGET ATRP electron transfer atom transfer radical polymerization
- the modified particles are characterized by elemental analysis and titration of functional groups to determine the grafting quantity.
- CPG porous inorganic carrier
- protein A is attached to the potentially handles represented as pendant functional groups.
- the resulting chromatographic performance, dependent on polymerization conditions, is mostly measured by ligand density and static binding capacity, and the findings are compared with literature reports for grafting performance under respective conditions.
- ProSepHC is used as a control for variability and as a performance target. In addition to simply testing the chromatographic performance as a function of various
- TMTGE trimethylolpropane triglycidyl ether
- TMTGE coating proceeds as a thermal statistical reaction involving surface hydroxyl groups and the epoxy groups of TMTGE. At first, TMTGE coating was followed by direct protein A coupling with residual epoxy groups as anchor using the customary epoxy-amine
- Figure 3 shows the dependence of the LD B CA on reaction time
- FIG. 4a and Fig 4b show the effect of TMTGE coating on static binding capacity and ligand density of the final resin at different concentrations of AA and CAN, respectively [Static binding capacity (a) and ligand density (b) of coated and uncoated samples with different monomer concentration at 40°C, and [CAN] of 0.03M] and Figure 5 show the static binding capacity (a) and ligand density (b) of coated and uncoated samples with different initiator concentration at 40°C, 0. 5M acrylic acid.
- separating materials for ion-exchange chromatography are especially porous base support materials covered with a coating rich in aliphatic hydroxyl or diol groups for covalent bonding of graft polymer chains composed of
- hydrophobic monomers comprising linear or branched alkyl, aryl, alkylaryl, arylalkyl having up to 18 carbon atoms, which optionally contain hydrophilic groups selected from the group consisting of alkoxy, cyano, carboxy, acetoxy and acetamino.
- each of these monomers offer derivatizable pendant groups after polymerization.
- Particular preference is given to separating materials which comprise a co- valently bonded graft polymer on the surface, prepared using at least one monomer unit which has a pronounced hydrophobic content in the form of at least one alkyl and/or aryl group having a suitable number of carbon atoms. Separating materials of this type have proven particularly effective in accordance with the invention owing to the possibility of interacting with the bio- polymer to be removed both by means of the hydrophobic content and also by means of the charged content of the graft polymer.
- derivatisation using at least one monomer unit having a hydrophobic content selected from the group of the alkyl vinyl ketones, aryl vinyl ketones, arylalkyl vinyl ketones, styrene, alkyl acrylates, aryl acrylates, arylalkyl acrylates, alkylaryl acrylates, alkyl methacrylates, aryl methacryl- ates, arylalkyl methacrylates and alkylaryl methacrylates is particularly desir- able.
- Separating materials in accordance with the present invention can therefore be prepared using at least one monomer unit comprising a hydrophic group which is selected from the group methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, 2-, 3-, or 4- oxapentyl, 2-, 3-, 4- or 5- oxahexyl, 2-, 3-, 4-, 5- or 6- oxaheptyl, 3-butoxy propyl, isopropyl, 3-butyl, isobutyl,
- 2-methylbutyl isopentyl, 2-methylpentyl and 3-methylpentyl, but also from the group 2-oxa-3-methylbutyl, 2-methyl-3-oxahexyl, 2-phenyI-2-oxoethyl, phenoxyethyl, phenyl, benzyl, phenylethyl and phenylpropyl, whereby the latter group induces a hydrophilic effect, which can enter into desirable interaction with biological molecules.
- GMA was polymerized because it can be directly coupled with protein A whereas other carboxylic groups typically require an intermediate.
- polymerization is followed by elemental analysis. Using the carbon content C% of the grafted CPG and the initial applied GMA per gram of CPG for polymerization HQMA.O, the grafting yield Y% is calculable according the following equations: C%
- nGMA,Q riGMA.cpG mol GMA per g of grafted CPG
- results for Qs and LDBCA for pGMA grafted CPG with different monomer concentrations are plotted in Figure 6 [LD BC A and Q s of GMA grafted CPG with GMA concentration of 0.025M, 0.1 M, and 0.27M; comparing with pure CPG and ProsepHC].
- pGMA-grafted CPG after the protein A coupling step possesses either no or negligible ligand density and static binding capacity.
- the Qs values are either the same or lower than the values observed with bare CPG due to non-specific binding. Additionally, the Qs values are lower than values obtained with pAA-grafted CPG synthesized at comparable [AA] at unoptimized conditions.
- Suitable monomers may be: monomers containing a functional group with a negative charge selected from the group maleic acid, acrylic acid, methacrylic acid,
- carboxylacrylamide carboxymethacrylamide, carboxypropylacrylamide, carboxymethylacrylamide, 2-acrylamido-2-methylsulphonic acid, and acrylamideethnae sulphonic acid;
- monomers containing a functional group with a positive charge selected from the group 2-(diethylaminoethyl)acrylamide, 2- (diethylaminoethyl)methacrylamide, 2- (acryloylaminoethyl)trimethylammonium chloride, 3- (acryloylaminopropyl)trimethylammonium chloride, 2- (dimethylaminoethyl)methacrylamide, 2-(dimethylaminoethyl)acrylamide, 2- (diethylaminopropyl)acrylamide, 2-(diethylaminopropyl)methacrylamide, 2- (methacryloylaminoethyl)trimethylammonium chloride, and 3- (methacryloylaminopropyl)trimethylammonium chloride; or monomers, which lead to hydrophobic interaction in chromatographic separation.
- functional groups from monomers like acrylic acid, glycidyl methacrylate, vinyl azlactone can be further functionalized with amines containing hydrophobic groups such as an alkylamine with 6 to18 carbon atoms, benzylamine, phenyethylamine, phenoxylethylamine,
- cerium ammonium nitrate concentration The influence of cerium ammonium nitrate concentration on graft
- Figure 9 shows that for the two series with two different EDC concentrations, static capacity and ligand density have reached a maximum value at certain CAN concentration (0.03mol/L). Further increasing or decreasing of CAN concentration causes lower values for immobilized protein A. Moreover, the reaction is more sensitive to the changes in initiator concentration with high acrylic acid concentration, as compared to the changes at low acrylic acid concentration. With 0.005M CAN, attempts with high acrylic acid
- Concentration of cerium ammonium nitrate is responsible for the amount of free radicals (predominantly at the hydroxyl group providing surface), created due to the redox reaction, described above. Radicals propagate via reaction with the vinyl bonds in the propagation step to form polymer grafts, such that grafting yield increases with the amount of released radicals. However, for CAN concentrations higher than optimum, termination reactions become more significant. Additionally, the formation of homopolymer in solution increases with CAN concentration. Homopolymerization and grafting polymerization are competing reactions.
- EDC Effect of EDC concentration on protein A immobilization
- EDC is used for carboxylic acid groups' activation to form peptide bounds with amine groups of protein A. Since the coupling was performed with the same concentration for EDC and protein A, the ratio of EDC and protein A to carboxylic acid groups is changed with the significant increase of grafted pAA amount. Therefore, a set of experiments for coupling with varied EDC concentration and two different protein A amounts (15 mg and 30 mg of protein A per ml_ of resin) is set up and performed, using the same batch of grafted CPG. Results for this set of experiments are plotted in Figures 12a) and b).
- Table 2 shows results for Q s and LDBCA for varied EDC concentration with two different amounts of protein A loading. As shown in Figure 12 B, LDBCA increases continuously with increasing amount of EDC in solution until
- EDC concentration affects protein A coupling very sensitively, with respect of maximum achievable static binding capacity and ligand density.
- the plateau observed in LD B CA as a function of EDC concentration might be attributable to two limitations in the current system. Firstly, the limited amount of provided protein A can simply limit the maximum achievable ligand density, considering that a higher protein A amount leads to a slightly higher level plateau. Secondly, every protein A molecule occupies a certain segment of polymer tentacles. The exhaustion of all accessible carboxylic acid groups might be responsible for the plateau at the examined grafting quantity.
- Static binding capacity reaches a maximum at the point where the plateau of ligand density begins and the binding capability decreases drastically with further EDC increase.
- a high excess of EDC might be responsible for changes of the active sites of protein A.
- carboxylic acid groups of proteins may be activated, and may lead to dimerization or cross linking of protein molecules and, thus, to a limited capability for IgG capturing.
- EDC is applied as a hydrochloric so that varied EDC concentration leads to a change in pH and in the salt concentration of the coupling solution. These shifts might be responsible for changes in the chain conformation.
- Poly(acrylic acid) is a weak poly electrolyte and shows stretched chains under alkaline conditions. High salt concentration and decrease of the pH usually support the coil conformation. Compared to stretched chains, the coil might lead to unfavorable positioning of the immobilized protein A.
- Figures 14a) and b) show dependencies of LD B CA (A) and Qs (B) on acrylic acid concentration and different EDC concentrations with high protein amount (30 mg protein A per 1 mL of resin).
- Figures 15a) and b) show dependencies of DBCA (A) and Qs (B) on acrylic acid concentration and different EDC concentrations with low protein amount ( 5 mg protein A per 1 mL of resin).
- Figure 14 and Figure 15 show an increase of ligand density with increase in the acrylic acid concentration. From 0.65M acrylic acid, the values for detected protein stay constant at approximately 1 1 mg/mL for the low protein loading (15 mg of protein A per mL of resin), and at ⁇ 20 mg/mL for the application of high protein quantity (30 mg of protein A per mL of resin). At the same time, the very low EDC concentrations of 0.0025 and
- Figure 16 illustrates that high grafting quantity (related to acrylic acid concentration) results in high achievable LDBCA-
- Table 3 gives a final overview about the dimension of grafted pAA and immobilized PrA for the specification of used CPG particles, calculated with the aid of carbon content and BCA assay measurements. Table 3: Dimensions of obtained graft polymer and immobilized protein A on CPG.
- CPG800 differ in their important attributes.
- CPG800 possesses pores with a mean diameter of 859A and a surface area of 46.4m 2 /mL (CPG1000: 1065A, 26.6m 2 /mL). The particles size and size distribution is the same.
- the results for the investigation of Ce(IV) initiated pAA grafting on CPG with smaller pore size are plotted in Figures 17a) and b) which show the dependencies of ligand density (A) and static binding capacity (B) dependent on acrylic acid concentration on small pore sized CPG with different EDC concentration, and 15 mg protein A per 1 mL of resin.
- Figure 17 a shows that under investigated coupling conditions, the achievable LDBCA increases from 9.0 g/mL to 12.2 mg/mL from 0.1 M to 0.2M acrylic acid. With 0.425M acrylic acid, the highest detected LD B CA is
- the ligand density is stronger influenced by EDC concentration at low AA concentration. More EDC leads clearly to higher ligand density with 0.1M acrylic acid.
- CPG 1000 Compared with 1065A pores (CPG 1000), the grafting of AA via Ce(lV) initiation on CPG with 859A mean pore size (CPG800) results in best chromatographic performance with different coupling conditions as well as polymerization conditions.
- CPG800 provides a significant higher surface area than CPG 000, more grafted pAA chains per mL resin are expected to be needed under the same polymerization conditions. This assumption means that less repetitive units per polymer chain can provide the same amount of functional groups. Therefore, it is reasonable that the same ligand density and static binding capacity for CPG800 and CPG1000 is reached at different AA concentration: - CPG800: QS-60 mg/mL, BCA-11 mg/mL at 0.2M acrylic acid
- SI AGET ATRP A further object of the present invention is the applicability of surface initiated AGET ATRP to activate the surfaces of porous metal oxide particles for the usage in protein A chromatography.
- Ce(IV) initiated graft polymerization potential influencing parameter for graft polymer attributes are varied and the effect of these variables on PrA immobilization ability is determined by static binding capacity and ligand density measurement in order to find out whether SI AGET ATRP can be applied to a porous system to synthesize a material for use as an affinity chromatography medium.
- GMA is chosen as a monomer, and the grafted polymer can be directly coupled using protein A.
- acrylic acid is a weekly acidic monomer and can hinder the process of ATRP.
- the model of SI AGET ATRP requires that the initiator is immobilized on the surface of the support material before polymerization step.
- the amount of immobilized initiator molecules is determinative for the number of growing chains and, thus, the graft density. Varying the amount of attached initiator is attempted by varying the concentration of initiator molecules during the immobilization step.
- the initiator immobilization step does not allow accurate reproducible results. While polymer grafting under same conditions from the same immobilization batch results in comparable values for Q S and LD B CA, these values show significant batch-to-batch variations.
- the initiator grafted CPG is also tested for bromine content.
- the bromine content determined by elemental analysis, amounts to
- the solvent for the polymerization needs to meet the following attributes: 1) all components - catalyst, ligand, monomer, and at least partially the reducing agent - need to be soluble. 2)
- the solvent should be miscible with water, considering the subsequently treatment in aqueous environment; non polar, organic solvents would hamper pore accessibility.
- Ascorbic acid, CuBr 2 , GMA, and Bpy are sufficiently soluble in DMF. In THF, only small quantities of CuBr 2 are soluble with the aid of PMDETA as ligand. Ascorbic acid is only partially soluble in THF.
- Figures 20a) and b) show the influence of GMA concentration on static binding capacity (A) and ligand density (B) on CPG, grafted via SI AGET ATRP.
- Figure 20 shows Qs and LDBCA for the range of 0.03M to 0.55M GMA. While, it is observed that the ligand density does not change significantly (4 - 6 mg/mL for the range of [GMA] tested), Q s continuously decreases with the increase in GMA concentration.
- pGMA While the protein coupling via pAA is shaped by the influence of EDC, pGMA provides immediately reactive epoxy group with every repetitive unit, which may lead to unfavorable positioning of protein A.
- pGMA is insoluble in water. Grafted chains are shrunk on the surface, or at least not dilated as in the case of pAA. Most of the epoxy groups are not reachable for protein A macromolecules
- Achievable graft density is usually higher with SI ATRP than with Ce(IV) graft polymerization.
- Table 4 Results for static binding capacity and ligand denisty obtained by different protein coupling conditions on the same batch of pGMA grafted CPG.
- Table 4 shows only slight changes for static binding capacity for the applied protein coupling conditions. Protein A coupling in 50% ethanol and in the presence of 1.1 M sodium sulfate result in the highest values for Q s with 29.8 mg/mL. With 10.5 mg/mL the LD B CA is significantly higher using sodium sulfate than with the conventional coupling procedure.
- the primary object of the present invention is to provide alkaline resistant porous ceramic particles for protein A
- Morphological attributes are not significantly affected by zirconia coating. Because of less usable surface hydroxyl groups on zirconia surfaces, even for the same morphology as for CPG, it is not expected that identical conditions for surface activation and polymerization will result in the same chromatographic performance. However, in a fashion similar to the
- Figure 22 shows the influence of acrylic acid concentration on ligand density and static binding capacity of Ce(IV) initiated polymerization on zirconia coated CPG.
- LDBCA is increasing with acrylic acid concentration until it reaches a plateau level at 15 mg/mL.
- the plot of static binding capacity shows a maximum in Q s of 51.3 mg/mL at 0.17M AA. From this point, Q s rapidly decreases as [AA] increases. This optimum [AA] is lower as compared to both CPG1000 and CPG800. Apart from the absolute values of optimum monomer concentration, these two plots show a similar trend as shown in case of CPG of both the sized studied.
- the DBC was determined for CPG1000 activated by ATRP and Ce(IV) mediated pAA grafting, in addition to CPG800, and zirconia coated CPG1000, grafted with pAA via Ce(IV) initiation. Additionally, the DBC of commercial available ProSepHC was determined as a well known standard.
- Figure 23 shows the course of curves for tested protein A resins. After switching from bypass to column-loading-mode, the duration of optimal column loading is reflected by the length of arising plateau until significant amount of IgG from the feed breaks through the column and, thus, the UV absorption accumulates. The general rule is, the longer the plateau, the higher the dynamic binding capacity. The slope of the curve after the plateau shows how much IgG is captured afterwards, and affects mainly the DBC for high IgG break through.
- First look at the plot for different resins shows the difference between all the resins, and that ProSepHC and resins prepared by the Ce(IV) initiated pAA grafting have different mass transfer properties.
- Figure 25 shows comparisons of column loading behavior with 3 min and 9 min residence time, for ProSepHC (a), ATRP treated CPG (b), CPG1000 with pAA tentacles (c), and ZrO 2 coated CPG with pAA tentacles (d).
- Figure 25 a) and Figure 25 b) are showing an only slightly varying course of curve at changed residence time for ProSepHC (a) and the ATRP treated resin (b).
- the variation is mainly attributed to the slightly lower IgG feed concentration (see bypass peak).
- the almost consistent values for DBC 10% in Table 6 confirm the absence of residence time influence on these two resins.
- the current DBC study indicates that surface activation of CPG via SI AGET ATRP of pGMA leads to protein immobilization, limited to the surface area, comparable to surface activation with small molecules. This fact leads to unhindered mass transfer in the DBC measurement and, thus, a sharp signal.
- the high achievable static binding capacity of CPG, activated with Ce(IV) initiated grafting of pAA is accompanied by hindered mass transfer for IgG capturing, as has been proven in the current DBC study.
- ProSepHC and polymer grafted CPG suggest differences in the mass transfer properties of the two resins: due to the uniform pore structure of ProSepHC, there is no significant difference between the DBC measured at high and low residence time as compared to polymer grafted CPG, which shows significant difference at two different residence times.
- the special advantage of the present invention is the multiplication of functional groups available at the surface of porous ceramic based particles, started from initial available hydroxyl groups. Cerium(IV)salt initiated polymerization and SI AGET ATRP. The use of acrylic acid and glycidyl methacrylate as monomer provides appropriate functional groups for subsequent protein immobilization.
- SI AGET ATRP even allows facile control over the amount of epoxy groups via graft polymerization as shown in its linear dependence on monomer concentration.
- ligand density and resulting static binding capacity are sensitively influenced by coupling conditions, especially the EDC concentration.
- the graft polymerization of GMA via SI AGET ATRP leads to reasonable amounts of reactive epoxy groups (as shown by the titration results), increasing with the polymer chain growth.
- two different grafting-from two different grafting-from
- polymerization techniques are carried out on controlled pore glass with an aliphatic coating which provides required hydroxyl groups. Both techniques, SI AGET ATRP of glycidyl methacrylate and cerium(IV) salt initiated graft polymerization with acrylic acid as monomer, allow the subsequent protein A immobilization for protein A chromatographic application. Basically, more grafted pAA allows the immobilization of more protein A. The increase of resulting capability for IgG capturing, however, is limited and pore clogging has to be avoided. In the range of parameter variation, acrylic acid concentration is identified as the main influencing parameter for grafting quantity. The ligand density and static binding capacity is also strongly affected by the EDC concentration in the coupling process.
- the way of protein coupling is affected by the polymer chain conformation as well as the number of simultaneously activated handles. While the chain conformation is primarily determined by the chemical environment during coupling process (solvent, pH, salt concentration), the number of activated handles in pGMA is predetermined because every repetitive unit provides one epoxy group. For pAA the EDC concentration is determining.
- the principle is transferred to a zirconia coated CPG, which leads to alkaline resistant ceramic based particles.
- CPG surface hydroxyl groups
- a 20 mL column equipped with a frit For this purpose, the CPG is slurried in pure water and settled in the column. The column needs to be tapped before the volume is determined because tapping leads to further consolidation of the CPG and, thus, to true volume measurement.
- the measured CPG is transferred to a 20 mL reaction vial, along with 10 mL of 5% nitric acid, and the slurry is rotated for 2.5h at 80°C in a hybridizer. Subsequently, the particles are washed with water for several times, until the pH of washing water is neutral.
- the TMTGE coating itself takes place in the 20 mL reaction vial, as well.
- To 5 mL of CPG are added 2.5 mL TMTGE (9.6 mmol) and 2.5 mL of DMF.
- the reaction mixture is heated up to 80°C for 4h.
- the coated particles are washed three times with DMF and three times with water.
- 10 mL of a 10% thioglycerol solution in 0.2M NaHC0 3 , containing 0.5M NaCI are added to the particles in a reaction vial.
- the quenching process is conducted overnight.
- the CPG particles are washed five times with water and, finally, they are either used for the next reaction step directly, or, stored in 20% ethanol.
- the CPG is only treated with 5% nitric acid at 80°C for 2.5h and washed with water before reaction.
- Ce(IV) initiated graft polymerization proceeds generally as follows. For 5 mL of pretreated CPG (with or without TMTGE treatment), a 5 mL acrylic acid solution in water (0.18M - 1.7M) and a 5 mL cerium ammonium nitrate solution in water (0.01 M - 0.2M) are prepared - each solution includes
- grafted beads are either used for protein A coupling or stored in 20% Ethanol.
- CPG particles are pretreated as described above, either only with nitric acid or coated with TMTGE.
- 100 ml_ of pretreated CPG are dried at 60°C for 96h under vacuum in a round bottom flask to ensure that residual moisture is removed completely.
- the round bottom flask is purged with nitrogen and sealed with a septum.
- Anhydrous THF (180 ml_) and triethylamine (14 mL, 100.4 mmol) are transferred to the round bottom flask, using a syringe.
- the suspension is cooled down to 0°C and slowly shaken in an ice bath while adding 10 mL Bib (80.9 mmol) drop wise during 10 min.
- the round bottom flask is still shaken in the ice bath for further 10 min. Then, the reaction mixture is positioned on an orbital shaker, where it is gently shaken at room temperature overnight. The suspension turns brown during the first 30 min. Afterwards, the particles with immobilized ATRP initiator are washed exhaustively with THF and water, alternately, until the supernatant of washing solvent stays colorless. The obtained particles are stored in the refrigerator, in THF.
- a typical surface activation of CPG via SI AGET ATRP proceeds as follows. First, the catalyst system is prepared in a stock solution. For this purpose, 46.8 mg CuBr 2 (0.21 mmol) and 164.2 mg Bpy (1.05 mmol) are dissolved in 50 mL DMF, and sonicated for 5 min. Afterwards, 5 mL of CPG with immobilized initiator are measured and washed two times with DMF in a 20 mL column with frit.
- the CPG (5 mL), 1 mL of initiator solution (4.2 pmol CuBr 2 ), 7.5 mL DMF, and 0.53 mL GMA (4.0 mmol) are transferred to a 20 mL reaction vial with septum, and the mixture is purged with nitrogen for 5 min.
- the actual initiation of the polymerization ensues by adding 1 mL DMF, including 50 mg ascorbic acid (0.28 mmol), with a syringe.
- the reaction mixture turns from turquoise to brown during the first 5 min.
- the reaction vial is spun for 22h at 30°C in a hybridizer. After polymerization, the particles are washed and reslurried five times in DMF, minimum, to remove free polymer, and three times in water before they are either used for PrA coupling or stored in 20% ethanol.
- CPG particles (5 mL), modified by poly(acrylic acid) grafting, are measured in a 20 mL column with frit, and washed three times with 0.1M aqueous
- the particles are transferred to a 20 mL reaction vial, flowed by the addition of 10 mL of a proteinA solution (15 mg/mL) in 0.1 M NaHC0 3 , containing 0.1 g EDC (0.52 mmol). ProteinA coupling takes place in a hybridizer at 37°C for 2.5h. Subsequently, the particles are washed three times with 0.1 M NaHC0 3 to remove unattached protein A. Obtained modified CPG is spun overnight at room temperature in 3% ethanol amine solution in 0.1M NaHC0 3 . Next day, the sample is washed three times with water.
- Protein A coupling takes place in a hybridizer at 37°C for 2.5h. Subsequently, the particles are washed three times with 0.1 M NaHC0 3 to remove
- the DBC provides the amount of IgG that can be attached in the column with constant feed flow until a defined percentage of feed IgG concentration is reached in the outlet, typically 10%. It is usually normalized to the column volume V c and can be expressed by the following equation.
- V b 103 ⁇ 4 , breakthrough load volume
- the DBC is basically dependent on the equilibrium binding capacity, also referred to as the static binding capacity Qs, but influenced by dispersive factors like mobile phase dispersion effects and mass transfer resistance of the solute.
- the static binding capacity reflects the thermodynamics of the system and can be used to characterize stationary phase regarding the theoretical maximal ability of IgG attachment.
- numerous of resin attributes are responsible for performance of a protein chromatographic column.
- DBC is an important index.
- Figure 26 shows the schematically flow scheme for the assembly of equipment in DBC measurement.
- Figure 27 shows a typical chromatogram for the DBC measurement of commercial available ProSepHC.
- the first signal which is caused by the bypass-switching determines the UV absorption for 100% IgG break through.
- the valve switches from bypass position to column load position, it needs about one column volume until the UV signal reaches a value that reflects a certain amount of "non-binding IgG", the 0%-point for DBC determination.
- the column is loaded with IgG what is reflected by a negligible slope of the UV signal while IgG enters the column with the feed stream. From the break through point, when all easy accessible protein A spots are occupied, the amount of detected IgG increases very fast.
- the DBCx % is calculable with the corresponding equation above.
- Bicinchoninic acid (BCA) assay for the determination of protein concentration has been introduced by P.K. Smith et al. in 985. Assumed that all the protein is immobilized and that the resin volume is known, it can be used for the measurement of ligand density of protein A chromatography media.
- the principle of the BCA assay is based on the formation of Cu(l) complexes from Cu(ll) in the presence of protein by the biuret reaction using
- This deep purple complex shows a light absorptive maximum at 562 nm so that the concentration can be quantified using a UV spectrometer. Since there is a protein-to-protein variation in the sensitivity, a standard curve with the respective protein is required for every measurement.
- the ligand density is specified in mg protein A per mL of resin.
- ligand density measurement is conducted as follows. 1 mL of resin is scaled exactly in a 5 mL column with frit by tapping it, avoiding air bubbles. The wet filter cake is diluted with 9 mL water, and the dispersion is homogenized with a stir bar for the transfer of three times 125 pL in each one 5 mL test tube. Then, 375 pL of water are added. For the standard curve, test tubes are filled with a protein A standard solution (1 mg/mL), according the following table:
- Static binding capacity Q s While the amount of protein A per volume of modified media is determined by the BCA assay, measurement of static binding capacity provides the amount of IgG that the media is able to capture. It is not mandatory that static binding capacity is linear increased with ligand density. The molecule orientation and the steric accessibility are important factors so that the knowledge of both values gives an idea of topology and nature of the pore structure after surface modification. While low Q s at high LDBCA hints to a lack of PrA accessibility, the opposite is an indicator for non-specific bindings.
- the principle of Qs measurement is as follows. A buffered IgG solution (feed) is added to a defined volume of modified resin. When the exhaustion of available PrA on surface is reached, the IgG concentration of the feed subtracted the IgG concentration of the supernatant is the amount of captured IgG per volume of stationary phase, the static binding capacity Q s . IgG concentration is determined by UV absorption at 280 nm, usually after 4h.
- ProSepHC Pro Sep vA High Capacity
- Epoxy titration is conducted based on a literature protocol. 1811 Right after SI AGET ATRP, 1 mL of the DMF washed particles is measured exactly, and washed with 5 mL 1 ,4-dioxane. The pGMA grafted CPG is transferred to a 20 mL reaction vial, and 10 mL of ⁇ 0.2M HCI in 1 ,4-dioxane are added. The mixture is shaken intensively for 5h and then, the residual acid is titrated with 0.05M NaOH in Ethanol, using phenolphthalein as indicator. The same procedure is conducted with blank CPG, so that the difference of needed NaOH means the amount of epoxy groups per mL of pGMA grafted CPG. Elemental analysis
- the LECO Carbon/Sulfur Determinator is designed to measure the carbon and sulfur in a wide variety of organic and inorganic materials by combustion and non-dispersive infrared detection. The sample is combusted at 1450 +_ 50°C in an atmosphere of pure oxygen using Thermolite as a combustion aid.
- Bromine content (Galbraith Labs, Inc. , Knoxville, TN): Samples are weighed into a combustion cup and mineral oil is added as a combustion aid. For Bromine (Br) determinations, 1 % hydrogen peroxide solution is added into the bomb. The sample and cup are sealed into a Parr oxygen combustion bomb along with a suitable absorbing solution. The bomb is purged with oxygen, then pressurized to 25-30 atm of oxygen pressure, and ignited. The contents of the bomb are well mixed and transferred to a beaker for subsequent ion chromatography.
- Example 7 Ce(IV)-initiated grafting from CPG: Comparison of uncoated and trimethylolpropane triglycidyl ether (TMTGE)-coated CPG (surface activation step).
- Ce(IV) (CAN)-initiated grafting of poly(acrylic acid) (pAA) is attempted on both uncoated and TMTGE-coated CPG.
- CPG is first treated with nitric acid for both “coated” and “uncoated” samples.
- nitric acid wash while “uncoated” CPG is directly grafted with pAA, "coated” CPG is first coated with T TGE, and the residual epoxy groups are quenched with thioglycerol to provide diol groups suitable for Ce(IV)-initiation.
- Zr0 2 coated CPG is treated in similar fashion as CPG.
- the Ce(IV)-initiated polymer grafting is performed with acrylic acid, and PrA is coupled to the pAA graft in the fashion similar to that of CPG to form PrA affinity medium.
- Figure 30 shows the effect of acrylic acid concentration on the Qs and LDBCA of PrA affinity media synthesized from Zr0 2 -coated CPG by Ce(IV)-grafting method.
- Ligand density is observed to increase with acrylic acid concentration until it reaches a plateau level at 15 mg/mL
- the plot of Qs shows a maximum in Qs of 51.3 mg/mL at 0.17M AA. From this point, Qs rapidly decreases as [AA] increases.
- the maximum Qs and LD B CA obtained with Zr02 coated CPG are comparable to that of CPG.
- Polymeric porous beads were grafted with pAA, and the pAA grafts were coupled with protein A to form PrA affinity medium.
- the surface does not need to be treated with TMTGE.
- the Ce(IV)-initiated grafting is performed directly from the beads without any pretreatment/activation step as described briefly below:
- Eshmuno® beads (5 ml) are mixed with the solution containing Ce(IV), 65% nitric acid, and acrylic acid of known concentrations, and mixed in the hybridizer at 40 C for 22 hours for grafting pAA to the beads.
- the pAA-grafted beads are mixed with protein A solution in suitable buffer containing known amount of activating agent, N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC). 4) Finally, the beads are quenched with ethanolamine to remove any residual reactive groups.
- activating agent N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC).
- Figure 32 shows an Qs and LDBCA of a representative protein A affinity medium synthesized using Eshmuno® beads by using Ce(IV)-initiated grafting process.
- a LDBCA of as high as 9.6 mg/ml has been achieved with the polymeric porous particles.
- the beads are first washed 5 times with deionized water and loading buffer each. Solutions of IgG and lysozyme are prepared in the loading buffer at the concentration of 5 mg/ml.
- the measured beads are suspended in 40 ml of IgG and lysozyme solution, and rotated slowly for 16 hours at room temperature.
- ) are measured using UV spectroscopy at the wavelength of 280 nm.
- the ion-exchange capacity of the beads is calculated using following equation.
- Fig. 1 Scanning electron micrograph of controlled pore glass (CPG)
- FIG. 2 shows schematically the immobilization reaction of protein A with hydroxyl groups on the surface of a suitable carrier
- Fig. 3 a) and b) shows the dependence of the LD B CA on reaction time and temperature at identical coupling conditions [LDBCA of protein A coupled CPG, coated with TMTGE, as a function of reaction time at 80°C (a), and of reaction temperature for 4h reaction time (b)].
- Fig. 4 a) and b) show the effect of TMTGE coating on static binding
- Fig. 5 a) and b) show the static binding capacity (a) and ligand density (b) of coated and uncoated samples with different initiator concentration at 40°C, 0.15M acrylic acid.
- Fig. 6 shows polymerization results for Q s and LDBCA for pGMA grafted CPG with different monomer concentrations of 0.025M, 0. M, and 0.27M; comparing with pure CPG and ProsepHC. shows received ligand density and static capacity for different polymerization durations in polymerization of acrylic acid on uncoated CPG
- Fig. 8 shows received ligand density (a) and static capacity (b) dependent on polymerization temperature with two different acrylic acid concentrations.
- Fig. 9 shows ligand density and static capacity in dependency of CAN
- Fig. 10 shows the carbon content of grafted CPG for different acrylic acid concentrations
- Fig. 11 shows ligand density (A) and static binding capacity (B) in
- Fig. 12 a) and b) show static binding capacity (a) and ligand density (b) for attempts with varied EDC concentration and two different protein A amounts; 15 mg PrA/mL resin (low protein), 30 mg PrA mL resin (high protein). Graft polymerization is conducted on TMTGE coated CPG with 0.425M acrylic acid, 0.03M CAN, at 40°C.
- Fig. 13 shows the efficiency of immobilized protein A in regard to IgG
- Fig. 14a) and b) show dependencies of LD B CA (a) and Q s (b) on acrylic acid concentration and different EDC concentrations with high protein amount (30 mg protein A per 1 ml_ of resin)
- Fig. 15a) and b) show dependencies of LD B CA (A) and Q s (B) on acrylic acid concentration and different EDC concentrations with low protein amount (15 mg protein A per 1 ml_ of resin)
- Fig. 16 shows the static binding capacity versus ligand density for the acrylic acid concentrations of 0.21 M, 0.425M, 0.65M, and 0.85M.
- Fig. 17 shows the dependencies of ligand density (a) and static binding
- Fig 18a) and b) show ligand density (A) and static binding capacity (B) at varied EDC and acrylic acid concentration.
- Fig. 19 shows the determined number of epoxy groups by titration on pGMA grafted CPG via SI AGET ATRP with varied GMA concentration as a linear function.
- Fig. 20a) and b) show the i Influence of GMA concentration on static
- Fig. 21 EDX measurement of pure CPG (A), and zirconia coated CPG (B).
- Fig. 22a) and b) show the influence of acrylic acid concentration on ligand density (a) and static binding capacity (b) of zirconia coated CPG.
- EDC 0.025g/10ml_
- protein A 30 mg/mL resin.
- Fig 23 shows the results for dynamic binding capacity measurement of different resins on zirconia coated CPG.
- IgG feed concentration is 2 mg/mL
- residence time is 3 min.
- Fig. 24 shows Changes of DBC50% during five measurement runs.
- Fig, 25 a) - d) show comparisons of column loading behavior with 3 min and 9 min residence time, for ProSepHC (a), ATRP treated CPG (b), CPG1000 with pAA tentacles (c), and Zr0 2 coated CPG with pAA tentacles (d).
- Fig. 26 shows the schematically flow scheme for the assembly of equipment in DBC measurement
- Fig. 27 shows a typical chromatogram for the DBC measurement of
- Fig. 28a) and b) show static binding capacity (A) and ligand density (B) of coated and uncoated samples as a function of acrylic acid
- Fig. 29a) and b) show static binding capacity (A) and ligand density (B) of coated and uncoated samples as a function of initiator concentration at 40°C, 0.15M acrylic acid.
- Fig. 30a) and b) show the influence of acrylic acid concentration on ligand density (A) and static binding capacity (B) of Zr0 2 coated CPG.
- Fig. 31 shows the trace for dynamic binding capacity measurement of PrA affinity medium synthesized from Zr0 2 coated CPG.
- Fig. 32 shows an Qs and LD B CA of an example PrA affinity medium
Abstract
Description
Claims
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CA2889914A CA2889914C (en) | 2012-11-01 | 2013-10-02 | Surface modification of porous base supports |
SG11201503216SA SG11201503216SA (en) | 2012-11-01 | 2013-10-02 | Surface modification of porous base supports |
KR1020157014554A KR102132157B1 (en) | 2012-11-01 | 2013-10-02 | Surface modification of porous base supports |
EP13773613.8A EP2914377A1 (en) | 2012-11-01 | 2013-10-02 | Surface modification of porous base supports |
CN201380057311.5A CN104736236B (en) | 2012-11-01 | 2013-10-02 | The surface modification of porous matrix holder |
US14/440,269 US10166527B2 (en) | 2012-11-01 | 2013-10-02 | Surface modification of porous base supports |
JP2015540058A JP6336996B2 (en) | 2012-11-01 | 2013-10-02 | Surface modification of porous substrate support |
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US61/721,178 | 2012-11-01 |
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EP (1) | EP2914377A1 (en) |
JP (1) | JP6336996B2 (en) |
KR (1) | KR102132157B1 (en) |
CN (1) | CN104736236B (en) |
CA (1) | CA2889914C (en) |
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DE102014016412A1 (en) * | 2014-11-07 | 2016-05-12 | Instraction Gmbh | Chromatographic sorbent with lipophilic aliphatic radical and anionic or deprotonatable radical |
EP3042192A1 (en) * | 2013-09-04 | 2016-07-13 | Sten Ohlson | Weak affinity chromatography |
WO2017041868A1 (en) * | 2015-09-10 | 2017-03-16 | Sartorius Stedim Biotech Gmbh | Adsorption medium, method for production thereof, and use thereof for purification of biomolecules |
WO2020118371A1 (en) * | 2018-12-12 | 2020-06-18 | Newsouth Innovations Pty Limited | Resin for desalination and process of regeneration |
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Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
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EP3042192A1 (en) * | 2013-09-04 | 2016-07-13 | Sten Ohlson | Weak affinity chromatography |
EP3042192A4 (en) * | 2013-09-04 | 2017-04-26 | Sten Ohlson | Weak affinity chromatography |
DE102014016412A1 (en) * | 2014-11-07 | 2016-05-12 | Instraction Gmbh | Chromatographic sorbent with lipophilic aliphatic radical and anionic or deprotonatable radical |
WO2017041868A1 (en) * | 2015-09-10 | 2017-03-16 | Sartorius Stedim Biotech Gmbh | Adsorption medium, method for production thereof, and use thereof for purification of biomolecules |
WO2020118371A1 (en) * | 2018-12-12 | 2020-06-18 | Newsouth Innovations Pty Limited | Resin for desalination and process of regeneration |
Also Published As
Publication number | Publication date |
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US20150298097A1 (en) | 2015-10-22 |
SG10201703540WA (en) | 2017-06-29 |
EP2914377A1 (en) | 2015-09-09 |
SG11201503216SA (en) | 2015-05-28 |
TWI609717B (en) | 2018-01-01 |
CN104736236B (en) | 2017-06-13 |
CA2889914C (en) | 2021-09-14 |
JP2016502457A (en) | 2016-01-28 |
JP6336996B2 (en) | 2018-06-06 |
CA2889914A1 (en) | 2014-05-08 |
US10166527B2 (en) | 2019-01-01 |
KR102132157B1 (en) | 2020-07-09 |
TW201431604A (en) | 2014-08-16 |
CN104736236A (en) | 2015-06-24 |
KR20150082436A (en) | 2015-07-15 |
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