Comparison of antibody binding to immobilized group specific affinity ligands in high performance monolith affinity chromatography

Purification of monoclonal antibodies using novel 3D printed ordered stationary phases

3D printing offers the unprecedented ability to fabricate chromatography stationary phases with bespoke 3D morphology as opposed to traditional packed beds of spherical beads. The restricted range of printable materials compatible with chromatography is considered a setback for its industrial implementation. Recently, we proposed a novel ink that exhibits favourable printing performance (printing time ∼100 mL/h, resolution ∼200 µm) and broadens the possibilities for a range of chromatography applications thanks to its customisable surface chemistry. In this work, this ink was used to fabricate 3D printed ordered columns with 300 µm channels for the capture and polishing of therapeutic monoclonal antibodies. The columns were initially assessed for leachables and extractables, revealing no material propensity for leaching. Columns were then functionalised with protein A and SO3 ligands to obtain affinity and strong cation exchangers, respectively. 3D printed protein A columns showed >85 % IgG recovery from harvested cell culture fluid with purities above 98 %. Column reusability was evaluated over 20 cycles showing unaffected performance. Eluate samples were analysed for co-eluted protein A fragments, host cell protein and aggregates. Results demonstrate excellent HCP clearance (logarithmic reduction value of > 2.5) and protein A leakage in the range of commercial affinity resins (<100 ng/mg). SO3 functionalised columns employed for polishing achieved removal of leaked Protein A (down to 10 ng/mg) to meet regulatory expectations of product purity. This work is the first implementation of 3D printed columns for mAb purification and provides strong evidence for their potential in industrial bioseparations.

Affinity monolith chromatography: A review of general principles and recent developments

Affinity monolith chromatography (AMC) is a liquid chromatographic technique that utilizes a monolithic support with a biological ligand or related binding agent to isolate, enrich, or detect a target analyte in a complex matrix. The target-specific interaction exhibited by the binding agents makes AMC attractive for the separation or detection of a wide range of compounds. This article will review the basic principles of AMC and recent developments in this field. The supports used in AMC will be discussed, including organic, inorganic, hybrid, carbohydrate, and cryogel monoliths. Schemes for attaching binding agents to these monoliths will be examined as well, such as covalent immobilization, biospecific adsorption, entrapment, molecular imprinting, and coordination methods. An overview will then be given of binding agents that have recently been used in AMC, along with their applications. These applications will include bioaffinity chromatography, immunoaffinity chromatography, immobilized metal-ion affinity chromatography, and dye-ligand or biomimetic affinity chromatography. The use of AMC in chiral separations and biointeraction studies will also be discussed.

An insight into chiral monolithic stationary phases for enantioselective high-performance liquid chromatography applications

In this review, three main classes of chiral monolithic stationary phases, namely silica-, organic polymer-, and hybrid-based monolithic stationary phases, are covered. Their preparations, applications, and advantages compared with the conventional-packed and open-tubular capillary columns are discussed. A detailed description of the different types and techniques used for the introduction of chiral selectors into the monolithic matrices such as immobilization, functionalization, coating, encapsulation, and bonding. Special emphasis is given to the recent developments of chiral selectors in HPLC monolithic stationary phases during the past 18 years.

Monolith affinity chromatography for the rapid quantification of a single-chain variable fragment immunotoxin

We developed a novel analytical method for concentration determination of tandem single‐chain antibody diphtheria toxin (immunotoxin). The method is based on polymethacrylate monoliths with Protein L ligands as the binding moiety. Different buffers were tested for elution of the Protein L‐bound immunotoxin and 4.5 M guanidinium hydrochloride performed best. We optimized the elution conditions and the method sequence resulting in a fast and robust method with a runtime <10 min. Fast determination of immunotoxin is critical if any process decisions rely on this data. We determined method performance and a lower limit of detection of 27 μg/mL and a lower limit of quantification of 90 μg/mL was achieved. The validity of the method in terms of residual analysis, precision, and repeatability was proven in a range from 100 to 375 μg/mL. The short runtime and ease of use of a high‐performance liquid chromatography method is especially useful for a process analytical tool approach. Bioprocesses related to immunotoxin where fermentation or other process parameters can be adjusted in accordance to the immunotoxin levels will be benefited from this method to achieve the highest possible purity and productivity.

High-capacity protein A affinity chromatography for the fast quantification of antibodies: Two-wavelength detection expands linear range

The high‐throughput analysis of antibodies from processes can be enhanced when the linear range is expanded and sample preparation is kept to a minimum. We developed a fast chromatography method based on a hexameric variant of staphylococcal protein A immobilized on Toyopearl matrix, TSK 5 PW using two wavelengths. A protocol with 5 min runtime and a single‐wavelength detection at 280 nm yielded an upper limit of quantification of 2.10 mg/mL and a lower limit of quantification of 0.06 mg/mL. The optimized method with a runtime of 2 min and two‐wavelength detection at 280 and 300 nm allowed us to span a valid concentration range of 0.01–5.20 mg/mL using two calibration curves. Sample selectivity was tested using mock supernatant mixed with antibody concentrations of 0.1–2.1 mg/mL, sample stability in the autosampler was shown for at least 24 h. We also tested the capabilities of the method to determine purity of an antibody sample by calculating the ratio of peak area of elution to peak area of flow‐through, which correlated well with the expected purity. The method will be very useful for process development and in‐process control, spanning concentrations from seed fermentation to harvest and purification.

Affinity monolith chromatography: A review of general principles and applications

Affinity monolith chromatography, or AMC, is a liquid chromatographic method in which the support is a monolith and the stationary phase is a biological-binding agent or related mimic. AMC has become popular for the isolation of biochemicals, for the measurement of various analytes, and for studying biological interactions. This review will examine the principles and applications of AMC. The materials that have been used to prepare AMC columns will be discussed, which have included various organic polymers, silica, agarose, and cryogels. Immobilization schemes that have been used in AMC will also be considered. Various binding agents and applications that have been reported for AMC will then be described. These applications will include the use of AMC for bioaffinity chromatography, immunoaffinity chromatography, dye-ligand affinity chromatography, and immobilized metal-ion affinity chromatography. The use of AMC with chiral stationary phases and as a tool to characterize biological interactions will also be examined.

In-line coupling of an aptamer based miniaturized monolithic affinity preconcentration unit with capillary electrophoresis and Laser Induced Fluorescence detection

A composite 30-cm capillary was prepared. The head of the capillary was a 1.5-cm original and miniaturized aptamer-based monolithic affinity support that was in-line coupled to the end of the capillary used for capillary electrophoresis (CE) with laser induced fluorescence (LIF) detection. The device was used for the preconcentration, separation and quantification of ochratoxin A (OTA) as a test solute. The 1.5-cm preconcentration unit consists of a fritless affinity monolithic bonded with 5'-SH-modified oligonucleotide aptamers. A vinyl spacer was used for thiol-ene photoclick chemistry with a 5min irradiation at 365nm. Photografting allowed to confine the binding reaction to the desired silica monolithic segment, upstream the empty section of the CE capillary using an UV mask. The photografting procedure was optimized preparing 10-cm capillary monoliths for nano-LC. The retention factors of cationic solutes in ion-exchange nano-LC allowed to follow the aptamer binding on the monolith. The reproducibility of the photografting process was satisfactory with inter-capillary variation lower than 10%. The aptamer bonding density can be increased by successive graftings of 100μM aptamer concentration solution (5pmol/cm/grafting). The optimal conditions to successfully perform the in-line coupling (preconcentration, elution and separation of OTA) with the composite capillary were adjusted depending on individual requirements of each step but also insuring compatibility. Under optimized conditions, OTA was successfully preconcentrated and quantified down to 0.1pg (percolation of 2.65μL of a 40ng/L OTA solution). A quantitative recovery of OTA (93±2%) was achieved in a single elution of 30pg percolated OTA amount. The reproducibility of the overall process was satisfactory with a relative standard deviation lower than 10% with negligible non-specific adsorption. This device was applied for the preconcentration and analysis of OTA in beer and wine at the ppb level within a total analysis time of 30min.

Development and thermodynamic evaluation of novel lipid raft stationary phase chromatography for screening potential antitumor agents

Novel lipid raft stationary phase chromatography (LRSC), with lipid rafts that contain abundant tropomyosin-related tyrosine kinase A receptors immobilized on the stationary phase, was developed for a high-throughput screening of potentially active antitumor agents. Lestaurtinib was used as a model compound to determine the operational parameters of the LRSC. Of all the factors considered, the particle size of column packing, the column temperature and the flow rate were of immense importance in determining the performance of the established LRSC system. In order to profoundly comprehend the binding interaction between the model drug and the receptors on the column, thermodynamic studies were employed. The results revealed that the interaction was spontaneous and exothermic, a typical enthalpy-driven process. Additionally, the primary forces were hydrogen bonding and van der Waals forces. In evaluating the applicability of the method, active extracts from Albizziae Cortex were screened out using the LRSC system under the optimized conditions. The bioactive components were successfully confirmed by the MTT assay. In conclusion, it could be said that the LRSC is a good model for screening potential antitumor agents because of its viability, rapid response and scalable features.

Affinity chromatography of proteins on monolithic columns

At present, monolithic stationary phases, because of their morphology, are widely used for development and realization of fast dynamic and static processes based on mass transition between liquid and solid phases. These are liquid chromatography, solid phase synthesis, microarrays, flow-through enzyme reactors, etc. High-performance liquid chromatography on monoliths, including bioaffinity mode, represents a unique technique appropriate for fast and efficient separation of biological (macro)molecules of different sizes and shapes (proteins, nucleic acids, peptides), as well as such supramolecular systems as viruses.In this work, the examples of application of commercially available macroporous monoliths for modern affinity processing are presented. In particular, the original methods developed for efficient isolation and fractionation of monospecific antibodies from rabbit blood sera, the possibility of simultaneous affinity separation of protein G and serum albumin from human serum, the isolation of recombinant products, such as protein G and tissue plasminogen activator from E. coli cell lysate and Chinese Hamster Ovary cell culture supernatant, respectively, are described in detail. The suggested and realized multifunctional fractionation of polyclonal pools of antibodies by combination of several short monolithic columns (disks) with different affinity functionalities stacked in the same cartridge represents an original and practically valuable method that can be used in biotechnology.

High throughput isolation and glycosylation analysis of IgG-variability and heritability of the IgG glycome in three isolated human populations

All immunoglobulin G molecules carry N-glycans, which modulate their biological activity. Changes in N-glycosylation of IgG associate with various diseases and affect the activity of therapeutic antibodies and intravenous immunoglobulins. We have developed a novel 96-well protein G monolithic plate and used it to rapidly isolate IgG from plasma of 2298 individuals from three isolated human populations. N-glycans were released by PNGase F, labeled with 2-aminobenzamide and analyzed by hydrophilic interaction chromatography with fluorescence detection. The majority of the structural features of the IgG glycome were consistent with previous studies, but sialylation was somewhat higher than reported previously. Sialylation was particularly prominent in core fucosylated glycans containing two galactose residues and bisecting GlcNAc where median sialylation level was nearly 80%. Very high variability between individuals was observed, approximately three times higher than in the total plasma glycome. For example, neutral IgG glycans without core fucose varied between 1.3 and 19%, a difference that significantly affects the effector functions of natural antibodies, predisposing or protecting individuals from particular diseases. Heritability of IgG glycans was generally between 30 and 50%. The individual's age was associated with a significant decrease in galactose and increase of bisecting GlcNAc, whereas other functional elements of IgG glycosylation did not change much with age. Gender was not an important predictor for any IgG glycan. An important observation is that competition between glycosyltransferases, which occurs in vitro, did not appear to be relevant in vivo, indicating that the final glycan structures are not a simple result of competing enzymatic activities, but a carefully regulated outcome designed to meet the prevailing physiological needs.

Bioaffinity chromatography on monolithic supports

Affinity chromatography on monolithic supports is a powerful analytical chemical platform because it allows for fast analyses, small sample volumes, strong enrichment of trace biomarkers and applications in microchips. In this review, the recent research using monolithic materials in the field of bioaffinity chromatography (including immunochromatography) is summarized and discussed. After giving an introduction into affinity chromatography, information on different biomolecules (antibodies, enzymes, lectins, aptamers) that can act as ligands in bioaffinity chromatography is presented. Subsequently, the history of monoliths, their advantages, preparation and formats (disks, capillaries and microchips) as well as ligand immobilization techniques are mentioned. Finally, analytical and preparative applications of bioaffinity chromatography on monoliths are presented. During the last four years 37 papers appeared. Protein A and G are still most often used as ligands for the enrichment of immunoglobulins. Antibodies and lectins remain popular for the analysis of mainly smaller molecules and saccharides, respectively. The highly porous cryogels modified with ligands are applied for the sorting of different cells or bacteria. New is the application of aptamers and phages as ligands on monoliths. Convective interaction media (epoxy CIM disks) are currently the most used format in monolithic bioaffinity chromatography.

Depletion of high-abundance proteins from human plasma using a combination of an affinity and pseudo-affinity column

Human serum albumin (HSA) and immunoglobulin G (IgG) represent over 75% of all proteins present in human plasma. These high-abundance proteins prevent the detection of low-abundance proteins which are potential markers for various diseases. The depletion of HSA and IgG is therefore essential for further proteome analysis. In this paper we describe the optimization of conditions for selective depletion of HSA and IgG using affinity and pseudo-affinity chromatography. A BIA Separations CIM (convective interaction media) Protein G disk was applied for the removal of IgG and the Mimetic Blue SA A6XL stationary phase for the removal of HSA. The binding and the elution buffer for CIM Protein G disk were chosen on the basis of the peak shape. The dynamic binding capacity was determined. It was shown to be dependent on the buffer system used and independent of the flow rate and of the concentration of IgG. Beside the binding capacity for the IgG standard, the binding capacity was also determined for IgG in human plasma. The Mimetic Blue SA A6XL column was characterized using human plasma. The selectivity of the depletion was dependent on the amount of human plasma that was loaded on the column. After the conditions on both supports had been optimized, the Mimetic Blue SA A6XL stationary phase was combined with the CIM Protein G disk in order to simultaneously deplete samples of human plasma. A centrifuge spin column that enables the removal of IgG and HSA from 20 microL of human plasma was designed. The results of the depletion were examined using sodium dodecyl sulfate polyacrylamide gel electrophoresis and two-dimensional gel electrophoresis.

Analysis of bovine immunoglobulin G in milk, colostrum and dietary supplements: a review

The immunoprotective properties of bovine milk immunoglobulin G (IgG) have led to a recent proliferation of nutritional products incorporating this protein. It has therefore become critical that reliable analytical techniques for the measurement of the IgG content in such products are available. This literature review surveys current methods of analysis for IgG, including separation-based or immuno-based concentration analysis. The review also discusses nutraceutical applications, regulatory issues, stability of IgG and the significance of primary reference material in IgG analysis.

Development of sulfhydryl-reactive silica for protein immobilization in high-performance affinity chromatography

Two techniques were developed for the immobilization of proteins and other ligands to silica through sulfhydryl groups. These methods made use of maleimide-activated silica (the SMCC method) or iodoacetyl-activated silica (the SIA method). The resulting supports were tested for use in high-performance affinity chromatography by employing human serum albumin (HSA) as a model protein. Studies with normal and iodoacetamide-modified HSA indicated that these methods had a high selectivity for sulfhydryl groups on this protein, which accounted for the coupling of 77-81% of this protein to maleimide- or iodoacetyl-activated silica. These supports were also evaluated in terms of their total protein content, binding capacity, specific activity, nonspecific binding, stability, and chiral selectivity for several test solutes. HSA columns prepared using maleimide-activated silica gave the best overall results for these properties when compared to HSA that had been immobilized to silica through the Schiff base method (i.e., an amine-based coupling technique). A key advantage of the supports developed in this work is that they offer the potential of giving greater site-selective immobilization and ligand activity than amine-based coupling methods. These features make these supports attractive in the development of protein columns for such applications as the study of biological interactions and chiral separations.

Study of dynamic adsorption behavior of large-size protein-bearing particles

The subject of this paper is an investigation of the peculiarities of dynamic adsorption behavior of nanoparticles. For this purpose, virus-mimicking synthetic particles bearing different proteins at their outer surface were specially constructed using two approaches, e.g. the cross-linking of proteins and modification of polystyrene microsphere surface by proteins. Two chromatographic modes, namely ion-exchange and affinity liquid chromatography on ultra-short monolithic columns [Convective Interaction Media (CIM) DEAE and CIM QA disks] have been used as a tool for dynamic adsorption experiments. Such parameters as maximum adsorption capacity and its dependence on applied flow rate were established and compared with those obtained for individual proteins. Similarly to individual proteins, it was shown that the maximum of adsorption capacity was not changed at different flow rates. In addition, the permeability of porous space of used monolithic sorbents appeared to be sufficient for efficient separation of large particles and quite similar to the well-studied process applied for individual proteins.

Sequential injection affinity chromatography utilizing an albumin immobilized monolithic column to study drug–protein interactions

In this study, sequential injection affinity chromatography was used for drug-protein interactions studies. The analytical system used consisted of a sequential injection analysis (SIA) manifold directly connected with convective interaction media (CIM) monolithic epoxy disks modified by ligand-immobilization of protein. A non-steroidal, anti-inflammatory drug, naproxen (NAP) and bovine serum albumin (BSA) were selected as model drug and protein, respectively. The SIA system was used for sampling, introduction and propulsion of drug towards to the monolithic column. Association equilibrium constants, binding capacity at various temperatures and thermodynamic parameters (free energy DeltaG, enthalpy DeltaH) of the binding reaction of naproxen are calculated by using frontal analysis mathematics. The variation of incubation time and its effect in on-line binding mode was also studied. The results indicated that naproxen had an association equilibrium constant of 2.90 x 10(6)M(-1) at pH 7.4 and 39 degrees C for a single binding site. The associated change in enthalpy (DeltaH) was -27.36 kcal mol(-1) and the change in entropy (DeltaS) was -73 cal mol(-1)K(-1) for a single type of binding sites. The location of the binding region was examined by competitive binding experiments using a biphosphonate drug, alendronate (ALD), as a competitor agent. It was found that the two drugs occupy the same class of binding sites on BSA. All measurements were performed with fluorescence (lambda(ext)=230 nm, lambda(em)=350 nm) and spectrophotometric detection (lambda=280 nm).

Affinity monolith chromatography

The combined use of monolithic supports with selective affinity ligands as stationary phases has recently given rise to a new method known as affinity monolith chromatography (AMC). This review will discuss the basic principles behind AMC and examine the types of supports and ligands that have been employed in this method. Approaches for placing affinity ligands in monoliths will be considered, including methods based on covalent immobilization, biospecific adsorption, entrapment, and the formation of coordination complexes. Several reported applications will then be presented, such as the use of AMC for bioaffinity chromatography, immunoaffinity chromatography, immobilized metal-ion affinity chromatography, dye-ligand affinity chromatography, and biomimetic chromatography. Other applications that will be discussed are chiral separations and studies of biological interactions based on AMC.

Integrated lectin affinity microfluidic chip for glycoform separation

Lectin affinity chromatography was miniaturized into a microfluidic format, which results in improvement of performance, as compared to the conventional method. A lectin affinity monolith column was prepared in the microchannel of a microfluidic chip. The porous monolith was fabricated by UV-initiated polymerization of ethylene dimethacrylate (EDMA) and glycidyl methacrylate (GMA) in the presence of porogeneities, followed by immobilization of pisum sativum agglutinin (PSA) on the monolith matrix. Using electroosmosis as the driven force, lectin affinity chromatographies of three kinds of glycoprotein, turkey ovalbumin (TO), chicken ovalbumin (CO), and ovomucoid (OM), were carried out on the microfluidic system. All the glycoproteins were successfully separated into several fractions with different affinities toward the immobilized PSA. The integrated system reduces the time required for the lectin affinity chromatography reaction to approximately 3%, thus, the overall analysis time from 4 h to 400 s. Only 300 pg of glycoprotein is required for the whole separation process. Moreover, troublesome operations for lectin affinity chromatography are simplified.

Metathesis polymerization-derived monolithic membranes for solid-phase extraction coupled with diffuse reflectance spectroscopy

Novel monolithic disks were prepared via ring opening metathesis polymerization (ROMP) from norborn-2-ene (NBE), a crosslinker, i.e., 1,4,5,8,8a-hexahydro-1,4,4,5,8, exo, endo-dimethanonaphthalene (DMN-H6) and tris(norborn-5-ene-2-ylmethylenoxy)methylsilane, respectively, 2-propanol and toluene (25:25:41:9, all %, w/w) using RuCl2(PCy3)2(CHPh) (Cy=cyclohexyl) as initiator and triphenylphosphine (PPh3) as modulator. Disks 1-2 mm thick were prepared by polymerization in a mold, disks thinner than 1mm were prepared by impregnation of nylon or other porous filters prior to the polymerization step. These disks were evaluated for the preconcentration of iodine and selected organic solutes from dilute aqueous samples by solid-phase extraction (SPE). Quantitative measurement of the extracted solutes was achieved by diffuse-reflectance spectroscopy (DRS) directly on the surface of the disk.

Thermostable carbohydrate-binding modules in affinity chromatography

Affinity chromatography is routinely used mostly on a preparative scale to isolate different biomolecules such as proteins and carbohydrates. To this end a variety of proteins is in common use as ligands. To extend the arsenal of binders intended for separation of carbohydrates, we have explored the use of carbohydrate-binding modules (CBM) in affinity chromatography. The thermostable protein CBM4-2 and two variants (X-6 and A-6) thereof, selected from a newly constructed combinatorial library, were chosen for this study. The CBM4-2 predominantly binds to xylans but also crossreacts with glucose-based oligomers. The two CBM-variants X-6 and A-6 had been selected for binding to xylan and Avicel (a mixture of amorphous and microcrystalline cellulose), respectively. To assess the ability of these proteins to separate carbohydrates, they were immobilized to macroporous microparticulate silica and analyses were conducted at temperatures ranging from 25 to 65 degrees C. With the given set of CBM-variants, we were able to separate cello- and xylo-oligomers under isocratic conditions. The affinities of the CBMs for their targets were weak (in the mM-microM range) and by adjusting the column temperature we could optimize peak resolution and chromatographic retention times. The access to thermostable CBM-variants with diverse affinities and selectivities holds promise to be an efficient tool in the field of affinity chromatography for the separation of carbohydrates.

Chromatographic investigation of macromolecular affinity interactions

High-performance monolithic disk affinity chromatography was applied to the investigation of formation of complexes between (1) complementary polyriboadenylic and polyribouridylic acids, e.g. poly(A) and poly(U), respectively, (2) poly(A) and synthetic polycation poly(allylamine), pAA. Polyriboadenylic acid and poly(allylamine) were immobilized on macroporous disks (CIM disks). Quantitative parameters of affinity interactions between macromolecules were established using frontal analysis at different flow rates.

Short monolithic beds: history and introduction to the field

The history of the development of short monolithic beds is described.

Protein L-agarose for Adsorption of Autoantibodies: A Potential Tool for Extracorporeal Treatment

This work investigated the adsorption of autoantibodies such as anti-SS-A/Ro, anti-SS-B/La, anti-Sm, and anti-dsDNA on protein L-agarose gel. In order to determine better conditions for IgG adsorption on this matrix, some buffer systems were tested. Adsorption data were analyzed using the Langmuir and Langmuir-Freundlich isotherm models. The experimental isotherms were best described by the Langmuir-Freundlich model, which indicated negative and positive cooperativities for binding in the presence of PBS and HEPES buffers, respectively. The K(d) values for phosphate buffered saline solution (PBS) and hydroxyethylpiperazine ethanesulfonic acid (HEPES) were 2.8 x 10(-7) M and 3.2 x 10(-7) M, respectively, which indicate a high affinity between IgG and the immobilized protein L. The amount of protein adsorbed per amount of protein loaded was high for anti-Sm (44%) and anti-dsDNA (46%), but low for anti-SS-B/La (9%). The amount of albumin adsorbed was lower than 0.06 mg/mL, which may remove the need for a plasma replacement solution in clinical apheresis.

Affinity processes realized on high-flow-through methacrylate-based macroporous monoliths

The technology for preparation of rigid macroporous polymers suggested in the late 1980s has become a powerful instrument for the development of a novel scientific and practical field. At present, monolithic stationary phases are widely used in the processes of bioseparation (chromatography), bioconversion (enzyme reactors) as well as in other processes based on interphase mass distribution (for example, solid phase peptide and oligonucleotide synthesis). Bioaffinity modes of suggested dynamic methods are very promising for their use in different analytical processes (immunological, ecological, medical and other types of analytical monitoring), preparative isolation of blood proteins such as myoglobin, hemoglobin, immunoglobulins, etc. and also recombinant products directly from cell supernatants or lysates. For the first time, it has been shown that bioaffinity pairing with participation of immobilized on carefully designed rigid supports is very fast and the whole process of affinity separation can be realized within second time scale. The principle of bioaffinity recognition is generaly at the construction of biological reactors (for example, enzyme reactors). Improved kinetics of biocatalized reactions is explained by a minimal influence on the surface of the used sorbent. Very perspective field is the use of discussed monoliths for solid phase chemical synthesis of fragments of biological macromolecules (peptides and oligonucleotides). Several examples of these applications will be presented and discussed.

Convective Interaction Media (CIM)--short layer monolithic chromatographic stationary phases

Modern downstream processing requires fast and highly effective methods to obtain large quantities of highly pure substances. Commonly applied method for this purpose is chromatography. However, its main drawback is its throughput since purification, especially of large molecules, requires long process time. To overcome this problem several new stationary phases were introduced, among which short layer monoliths show superior properties for many applications. The purpose of this review is to give an overview about short methacrylate monolithic columns commercialised under the trademark Convective Interaction Media (CIM). Their unique properties are described from different perspectives, explaining reasons for their application on various areas. Approaches to prepare large volume methacrylate monolithic column are discussed and optimal solutions are given. Different examples of CIM monolithic column implementation are summarised in the last part of the article to give the reader an idea about their advantages.

High-Performance Affinity Monolith Chromatography: Development and Evaluation of Human Serum Albumin Columns

Several immobilization methods were explored for the preparation of high-performance affinity monolithic columns containing human serum albumin (HSA). These monoliths were based on a copolymer of glycidyl methacrylate and ethylene dimethacrylate. In one method, the epoxy groups of this copolymer were used directly for the immobilization of HSA through its amine residues (i.e., the epoxy method); in other approaches, these epoxy groups were converted to diols for later use in the carbonyldiimidazole, disuccinimidyl carbonate, and Schiff base methods. Each HSA monolith was evaluated in terms of its total protein content and its retention of several model compounds, including (R/S)-warfarin and D/L-tryptophan. The greatest amount of immobilized HSA was obtained by the Schiff base method, whereas the epoxy method gave the lowest protein content. The Schiff base method also gave the best resolution in chiral separations of (R/S)-warfarin and D/L-tryptophan. All of the immobilization methods gave similar relative activities for HSA in its binding to (R)- and (S)-warfarin, but some differences were noted in the activity of the immobilized HSA for D- and L-tryptophan. The efficiency of these monoliths was found to be greater than that of silica-based HSA columns for (R/S)-warfarin (i.e., analytes with high retention), but little or no difference was seen for D- and L-tryptophan (analytes with weak retention).

Monoliths for fast bioseparation and bioconversion and their applications in biotechnology

Monoliths have consolidated their position in bioseparation. More than 200 different applications have been reported in the past two decades and their advantages compared to conventional chromatography demonstrated. These include the high mass transfer efficiency due to the convective flow enabled by the macroporous character of the matrix. Recently plasmid DNA and viruses were separated with high efficiency and cryogels and monolithic superporous agarose were developed for capture of proteins from crude homogenates and separation of microorganisms or lymphocytes. Currently four companies manufacture monoliths mainly for analytical applications although monoliths with a volume of 0.8 liter are commercially available and 8 L are available as prototypes. A book entitled "Monolithic materials: preparation, properties and applications" was published in 2003 and became standard reference of the status of this area. This review focuses on the progress in monoliths that goes beyond the scope of this reference book. Less progress has been made in the field of bioconversions in spite of the fact that monolithic supports exhibit better performance than beads in enzymatic processing of macromolecules. It appears that the scientific community has not yet realized that supports for these applications are readily available. In addition, monoliths will further substantially advance bioseparations of both small and large molecules in the future.

Affinity chromatography with monolithic capillary columns

Monolithic capillary columns with surface-immobilized mannan have been introduced for affinity-based micro-column separations by nano-liquid chromatography (nano-LC) and capillary electrochromatography (CEC). Two kinds of polymethacrylate monoliths were prepared, namely poly(glycidyl methacrylate-co-ethylene dimethacrylate) and poly(glycidyl methacrylate-co-ethylene dimethacrylate-co-[2-(methacryloyloxy)ethyl]trimethyl ammonium chloride) to yield neutral and cationic macroporous polymer, respectively. While neutral monoliths with immobilized mannan were only useful for affinity nano-LC, the cationic monoliths with surface-bound mannan were useful in both affinity nano-LC and affinity CEC. The cationic monoliths allowed a relatively high electro-osmotic flow (EOF) when mannan was immobilized to the epoxy monolith via a positively charged spacer arm, triethylenetetramine. The neutral monoliths exhibited lower permeability under pressure-driven flow (PDF) than the cationic monoliths indicating that the latter had wider flow-through pores than the former. Both types of monoliths with immobilized mannan exhibited strong affinity toward mannose-binding proteins (MBP) such as the plant lectins concanavalin A and Lens culinaris agglutinin and a mammalian lectin (e.g. rabbit serum mannose-binding protein). Due to the strong binding affinity, the monoliths with surface bound mannan allowed the injection of large volume of rabbit serum and to isolate in a single run the mannose-binding protein in an amount sufficient to run with it sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS), thus demonstrating their capability in "nano-proteomics".

Development of reactive thiol-modified monolithic capillaries and in-column surface functionalization by radical addition of a chromatographic ligand for capillary electrochromatography

Reactive thiol-modified capillary columns for capillary electrochromatography (CEC) were developed by transforming the pendent 2,3-epoxypropyl groups of poly(glycidyl methacrylate-co-ethylene dimethacrylate) (poly(GMA-co-EDMA)) monoliths into 3-mercapto-2-hydroxy-propyl residues by a nucleophilic substitution reaction, employing sodium-hydrogen sulfide as nucleophilic reagent. Conditions for this modification reaction were systematically optimized with respect to different parameters, such as reaction temperature, pH-value, reaction time, type and concentration of organic modifier, and concentration of the sodium-hydrogen sulfide solution. The amount of thiol groups that was generated on the monolith surface was determined directly in the capillaries by a disulfide-exchange reaction employing 2,2'-dipyridyl disulfide (DPDS). This reaction in the capillary liberates pyridine-2-thione in equimolar amount to the surface sulfhydryls, which was collected into a vial and determined photometrically at 343 nm by RP-HPLC. About 17% of the total lateral epoxide moieties of the monolithic substrate could be transformed to reactive sulfhydryl groups, which corresponds to about 0.7 mmol g(-1) monolithic polymer, with a column-to-column repeatability of 3.2% R.S.D. The reactive thiol groups can be utilized to attach any chromatographic ligand with appropriate anchor in a second step, e.g. by radical addition, graft polymerization, nucleophilic substitution, disulfide formation or Michael addition reaction. To demonstrate the feasibility of the concept, we chose an anion exchange type chromatographic ligand based on a quinine derivative, O-9-tert-butylcarbamoylquinine (t-BuCQN) which was attached to the monolith in a radical addition reaction, for a further in-column surface functionalisation. About 78% of the sulfhydryl groups were derivatized with t-BuCQN as determined from differential DPDS assays before and after the selector immobilization reaction. The applicability of these surface-functionalised monolithic capillary columns could be shown by an electrochromatographic separation of the enantiomers of N-3,5-dinitrobenzoyl-leucine, which performed fairly well compared to an analogous capillary that was fabricated by an in situ copolymerization approach.