Pseudo-specific bioaffinity chromatography of immunoglobulin-G

Polyoxometalate-Coated Magnetic Nanospheres for Highly Selective Isolation of Immunoglobulin G

Polyoxometalate [{a-PW₁₁O₃₉Zr(μ-OH)(H₂O)}₂]^8- (POM1) is first prepared by sandwiching Zr^IV among 2 mono-lacunary α-Keggin polyoxometalates, and then novel magnetic nanoparticles (NPs), Fe₃O₄@polyethyleneimine (PEI)@POM1, are fabricated by coating POM1 onto the surface of magnetic Fe₃O₄@PEI NPs under electrostatic interaction. The obtained Fe₃O₄@PEI@POM1 NPs are characterized by Fourier transform infrared, zeta potential, vibrating sample magnetometer, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. Ascribed to the hydrogen-bonding and electrostatic interactions, the NPs exhibit high adsorption selectivity toward IgG, and the adsorption capacity is high up to 304 mg g^-1 under optimal adsorption conditions. By using 0.01% cetyl trimethylammonium bromide to strip the adsorbed protein species, an elution efficiency of 95% is achieved. The feasibility of Fe₃O₄@PEI@POM1 NPs in real-world sample assay has been demonstrated by the selective isolation of IgG heavy chain and light chain from human serum, as confirmed by the sodium dodecyl sulfate polyacrylamide gel electrophoresis assay.

Oriented immobilized anti-hIgG via F(c) fragment-imprinted PHEMA cryogel for IgG purification

Antibodies are used in many applications, especially as diagnostic and therapeutic agents. Among the various techniques used for the purification of antibodies, immunoaffinity chromatography is by far the most common. For this purpose, oriented immobilization of antibodies is an important step for the efficiency of purification step. In this study, F(c) fragment-imprinted poly(hydroxyethyl methacrylate) cryogel (MIP) was prepared for the oriented immobilization of anti-hIgG for IgG purification from human plasma. Non-imprinted poly(hydroxyethyl methacrylate) cryogel (NIP) was also prepared for random immobilization of anti-hIgG to compare the adsorption capacities of oriented (MIP/anti-hIgG) and random (NIP/anti-hIgG) cryogel columns. The amount of immobilized anti-hIgG was 19.8 mg/g for the NIP column and 23.7 mg/g for the MIP column. Although the amount of immobilized anti-hIgG was almost the same for the NIP and MIP columns, IgG adsorption capacity was found to be three times higher than the NIP/anti-hIgG column (29.7 mg/g) for the MIP/anti-hIgG column (86.9 mg/g). Higher IgG adsorption capacity was observed from human plasma (up to 106.4 mg/g) with the MIP/anti-hIgG cryogel column. Adsorbed IgG was eluted using 1.0 M NaCl with a purity of 96.7%. The results obtained here are very encouraging and showed the usability of MIP/anti-hIgG cryogel prepared via imprinting of Fc fragments as an alternative to conventional immunoaffinity techniques for IgG purification.

Concanavalin A immobilized poly(ethylene glycol dimethacrylate) based affinity cryogel matrix and usability of invertase immobilization

Concanavalin A (Con A) immobilized supermacroporous poly(ethylene glycol dimethacrylate) [poly(EGDMA)] monolithic cryogel column was prepared by radical cryocopolymerization of EGDMA as a monomer and N,N'-methylene-bisacrylamide as a crosslinker. Bioligand Con A was then immobilized by covalent binding onto poly(EGDMA) cryogel via glutaraldehyde activation [Con A-poly(EGDMA)]. Con A-poly(EGDMA) cryogel was characterized by swelling studies and scanning electron microscopy. The monolithic cryogel contained a continuous polymeric matrix having interconnected pores of 10-50 μm size. The equilibrium swelling degree of the cryogel was 15.01 g H₂O/g dry cryogel. Con A-poly(EGDMA) cryogel was used in the adsorption/desorption of invertase from aqueous solutions. The maximum amount of invertase adsorption from aqueous solution in acetate buffer was 55.45 mg/g polymer at pH 5.0. Con A-poly(EGDMA) cryogels were used for repetitive adsorption/desorption of invertase without noticeable loss in invertase adsorption capacity after 10 cycles.

Monosize microbeads for pseudo-affinity adsorption of human insulin

Affinity adsorption technique is increasingly used for protein purification, separation and other biochemical applications. Therapeutic molecules such as antibodies, cytokines, therapeutic DNA and plasma proteins must be purified before characterization and utilization. The aim of this study was to prepare micronsized spherical polymeric beads and to investigate the extent of their human insulin adsorption capability. Monosize poly(ethylene glycol dimethacrylate-N-methacryloyl-(L)-histidine) [poly(EDMA-MAH)] beads were prepared by modified suspension copolymerization. Functional monomer (MAH) was synthesized using methacryloyl chloride and L-histidine. The beads were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, swelling test and elemental analysis. MAH incorporation into monosize polymeric beads, having an average size around 2-3 μm, was estimated as 55.3 μmol MAH/g bead. Equilibrium swelling ratios of poly(EDMA-MAH) and poly(EDMA) beads were 65% and 55%, respectively. Adsorption experiments were performed under different conditions (i.e., pH, temperature, protein concentration and ionic strength). It was found that adsorption characteristics are strongly depend on these conditions. Maximum insulin adsorption capacity was achieved as 24.7 mg insulin/g poly(EDMA-MAH) beads. Results were well fitted to the Langmuir isotherm model. Compared with poly(EDMA-MAH), nonspecific insulin adsorption onto poly(EDMA) beads was very low (0.61 mg insulin/g bead) and can be negligible. It was observed that insulin could be repeatedly adsorbed and desorbed (at least 10 times) without significant loss in adsorption capacity.

High capacity binding of antibodies by poly(hydroxyethyl methacrylate) nanoparticles

Poly(hydroxyethyl methacrylate) (PHEMA) nanoparticles with an average size of 150 nm in diameter and with a poly-dispersity index of 1.171 were produced by a surfactant free emulsion polymerization. Specific surface area of the PHEMA nanoparticles was found to be 1779 m(2)/g. Reactive imidazole containing 3-(2-imidazoline-1-yl)propyl(triethoxysilane) (IMEO) was used as a pseudo-specific ligand. IMEO was attached covalently onto the nanoparticles. PHEMA-IMEO nanoparticles were used for the affinity binding of immunoglobulin-G (IgG) from human plasma. To evaluate the degree of IMEO loading, the PHEMA nanoparticles were subjected to Si analysis by using flame atomizer atomic absorption spectrometer and it was estimated as 64.5 mg/g of polymer. The nanoparticles were characterized by transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). IgG binding onto the PHEMA nanoparticles was found to be 5.2 mg/g. Much higher binding values (up to 843 mg/g) were obtained for the PHEMA-IMEO nanoparticles. IgG could be repeatedly bound and eluted on PHEMA-IMEO nanoparticles without noticeable loss in the IgG binding capacity.

Affinity separation of immunoglobulin G subclasses on dye attached poly(hydroxypropyl methacrylate) beads

Poly(hydroxypropyl methacrylate) [poly(HPMA)] gel beads with an average size of 150-200 micro m were prepared by suspension polymerization of hydroxypropyl methacrylate (HPMA). The poly(HPMA) gel beads were characterized by swelling studies, surface area measurements, scanning electron microscopy (SEM) and elemental analysis. Poly(HPMA) gel beads had a specific surface area of 88.6 m(2)/g. The dye Reactive Green HE 4BD was chemically attached to yield dye-poly(HPMA) gel beads at an average concentration of 44.3 micro mol dye/g bead with a swelling ratio of 75%. These dye attached gel beads were used in the separation of immunoglobulin-G (IgG) through adsorption-elution studies. The non-specific adsorption of IgG on the poly(HPMA) gel beads was 0.5 mg/g. The attachment of Reactive Green HE 4BD significantly increased the adsorption of IgG up to 71 mg/g. The Langmuir adsorption model was found to be applicable in interpretation of data pertaining to the adsorption studies of IgG with Reactive Green HE 4BD attached to the poly(HPMA) gel beads. The adsorption of IgG was found to be optimal at pH 7.0. The adsorption of IgG was observed to decrease by about 76% as the NaCl concentration was increased from 0.001 to 0.1 M. The IgG adsorption capacity of the dye attached poly(HPMA) gel beads was determined for a commercially available IgG solution to be 4.2 mg/g for IgG(1), 64.5 mg/g for IgG(2), 7.1 mg/g for IgG(3) and 10.8 mg/g for IgG(4). The Reactive Green HE 4BD attached poly(HPMA) gel beads have a significant adsorption capacity for IgG(2). The quantity of adsorbed IgG(2) is three times higher than the quantity of the other subclasses, IgG(1), IgG(3) and IgG(4). A similar adsorption behaviour was observed when the albumin free human plasma was used. The quantity of adsorbed IgG(2) is higher than the quantity of the other subclasses, IgG(1), IgG(3) and IgG(4). Adsorption capacities for albumin free human plasma were obtained as 6.4 mg/g for IgG(1), 67.8 mg/g for IgG(2), 5.2 mg/g for IgG(3) and 8.6 mg/g for IgG(4). Significant amount of the adsorbed IgG (up to 95%) was eluted in 1h in the elution medium containing 2.0 M NaCl. Repeated adsorption/elution processes showed that these dye attached gel beads are suitable for IgG adsorption.

Synthesis and characterization of pseudo-affinity ligand for penicillin acylase purification

The aim of this work was to test a chromatographic affinity support containing methacryloyl antipyrine (MAAP) for penicillin acylase (PA) purification by using pure penicillin acylase and crude extract. First, MAAP as a pseudo-specific ligand was synthesized by using methacryloyl chloride and 4-aminoantipyrine. Polymer beads (average size diameter: 40-120 micro m) were prepared by suspension polymerization of ethylene glycol dimethacrylate (EGDMA) and MAAP. This approach for the preparation of adsorbent has several advantages over conventional preparation protocols. An expensive and time consuming step in the preparation of adsorbent is immobilization of a ligand to the adsorption matrix. In this procedure, affinity ligand MAAP acts as comonomer without further modification steps. Poly(EGDMA-MAAP) beads were characterized by FTIR, NMR and screen analysis. Elemental analysis of MAAP for nitrogen was estimated as 89.3 micro mol/g. The prepared adsorbent was then used for the capture of penicillin acylase in batch system. The maximum penicillin acylase adsorption capacity of the poly(EGDMA-MAAP) beads was found to be 82.2 mg/g at pH 5.0. Chromatography with crude feedstock resulted in 23.2-fold purification and 93% recovery with 1.0 M NaOH.

Purification of intravenous immunoglobulin G from human plasma – aspects of yield and virus safety

Plasma-derived intravenous immunoglobulin (IVIG) preparations have been successfully applied for the prophylactic prevention of infectious diseases in immunodeficient patients. In addition to its replacement therapy of primary and secondary antibody deficiencies, IVIG has found increased use in autoimmune and inflammatory diseases. IVIG has become the major plasma product on the global blood product market. The world wide consumption nearly tripled between 1992 and 2003, from 19.4 to 52.6 tons. Classical manufacturing processes of IVIG, but also new strategies for purification are discussed with respect to practicability and yield. Ethanol fractionation is still the basis for most IVIG processes, although isolation and purification of immunoglobulin G (IgG) by chromatography has gained ground. The efficiency of virus inactivation methods and virus removal techniques in terms of logarithmic reduction factors are analyzed, but also the IgG losses are taken into consideration. Some of these methods also have the ability to separate prions. High pathogen safety and high yields have become the dominant goals of the plasma fractionation industry.