Selective removal of immunoglobulin E from rat blood by membrane-immobilized antibody

Isolation and analysis of amyloid-β 1-42 monomer and oligomers in liquid droplets using an immunoaffinity membrane

Monomeric molecules such as amyloid-β can aggregate and transform into oligomeric and fibrous forms, which are implicated in the development and progression of Alzheimer's disease. Novel analytical techniques for the formation of oligomers are required to examine the neurotoxic amyloid-β oligomers involving fibrils. After isolating amyloid-β monomer 1-42 using a biotinylated antibody bound to membrane-immobilized avidin (immunoaffinity membrane), their masses were determined by MALDI-TOF MS. Fluorometric determination of more than 0.5μM of aggregated amyloid-β in pipette droplets was performed after aggregation and dilution of 1mM amyloid-β. Thus, large (>105nm) amyloid-β oligomers in microliter volumes of fluids were isolated using the immunoaffinity membrane and quantitatively analyzed after removal of amyloid-β monomers and small oligomers by non-denaturing electrophoresis. In addition, amyloid-β oligomers were specifically isolated from a mixture of human plasma and aggregated amyloid-β and then fluorometrically analyzed. Our results show that the combination of immunoaffinity membrane-binding and fluorescence determinations together with one drop analysis could be used to isolate and detect huge neurotoxic amyloid-β oligomers such as fibrils in plasma samples.

Nanomagnet-based removal of lead and digoxin from living rats

In a number of clinical conditions such as intoxication, bacteraemia or autoimmune diseases the removal of the disease-causing factor from blood would be the most direct cure. However, physicochemical characteristics of the target compounds limit the applicability of classical filtration and diffusion-based processes. In this work, we present a first in vivo magnetic blood purification rodent animal model and demonstrate its ability to rapidly clear toxins from blood circulation using two model toxins with stable plasma levels (lead (Pb(2+)) and digoxin). Ultra-strong functionalized metal nanomagnets are employed to eliminate the toxin from whole blood in an extracorporeal circuit. In the present experimental demonstration over 40% of the toxin (i.e. lead or digoxin) was removed within the first 10 minutes and over 75% within 40 minutes. After capturing the target substance, a magnetic trap prevents the toxin-loaded nanoparticles from entering the blood circulation. Elemental analysis and magnetic hysteresis measurements confirm full particle recovery by simple magnetic separation (residual particle concentration below 1 μg mL(-1) (detection limit)). We demonstrate that magnetic separation-based blood purification offers rapid blood cleaning from noxious agents, germs or other deleterious materials with relevance to a number of clinical conditions. Based on this new approach, current blood purification technologies can be extended to efficiently remove disease-causing factors, e.g. overdosed drugs, bacteria or cancer cells without being limited by filter cut-offs or column surface saturation.

Membrane adsorbers as purification tools for monoclonal antibody purification

Downstream purification processes for monoclonal antibody production typically involve multiple steps; some of them are conventionally performed by bead-based column chromatography. Affinity chromatography with Protein A is the most selective method for protein purification and is conventionally used for the initial capturing step to facilitate rapid volume reduction as well as separation of the antibody. However, conventional affinity chromatography has some limitations that are inherent with the method, it exhibits slow intraparticle diffusion and high pressure drop within the column. Membrane-based separation processes can be used in order to overcome these mass transfer limitations. The ligand is immobilized in the membrane pores and the convective flow brings the solute molecules very close to the ligand and hence minimizes the diffusional limitations associated with the beads. Nonetheless, the adoption of this technology has been slow because membrane chromatography has been limited by a lower binding capacity than that of conventional columns, even though the high flux advantages provided by membrane adsorbers would lead to higher productivity. This review considers the use of membrane adsorbers as an alternative technology for capture and polishing steps for the purification of monoclonal antibodies. Promising industrial applications as well as new trends in research will be addressed.

Protein separation using membrane chromatography: opportunities and challenges

Some of the problems associated with packed bed chromatography can be overcome by using synthetic macroporous and microporous membranes as chromatographic media. This paper reviews the current state of development in the area of membrane chromatographic separation of proteins. The transport phenomenon of membrane chromatography is briefly discussed and work done in this area is reviewed. The various separation chemistries which have been utilised for protein separation, along with different applications, are also reviewed. The technical challenges facing membrane chromatography are highlighted and the scope for future work is discussed.

Affinity membrane chromatography for the analysis and purification of proteins

Affinity chromatography is unique among separation methods as it is the only technique that permits the purification of proteins based on biological functions rather than individual physical or chemical properties. The high specificity of affinity chromatography is due to the strong interaction between the ligand and the proteins of interest. Membrane separation allows the processing of a large amount of sample in a relatively short time owing to its structure, which provides a system with rapid reaction kinetics. The integration of membrane and affinity chromatography provides a number of advantages over traditional affinity chromatography with porous-bead packed columns, especially with regard to time and recovery of activity. This review gives detailed descriptions of materials used as membrane substrates, preparation of basic membranes, coupling of affinity ligands to membrane supports, and categories of affinity membrane cartridges. It also summarizes the applications of cellulose/glycidyl methacrylate composite membranes for proteins separation developed in our laboratory.

High-performance immunoaffinity chromatography, an immunoaffinity membrane for selective removal of plasma components, and safety evaluation of the latter system

This article reviews our studies on evaluating the suitability of high-performance immunoaffinity chromatography (HPIAC), an immunoaffinity membrane (IAM) for removing unwanted plasma component, and the safety of the IAM. In an attempt to resolve the problem of amyloid deposition in dialysis patients, we used an HPIAC column, bearing anti-beta 2-microglobulin to remove specifically beta 2-MG from human plasma. The use of a membrane as an affinity ligand support was also studied. A specific antibody immobilized on the membrane was highly effective for the removal of rat immunoglobulin E and of a human serum amyloid P component passed through an extracorporeal circulation (EC) system. Biocompatibility of the specific antibody-bearing IAM was also examined. These techniques should prove useful for medical applications and may have broad applicability to the elimination of any unwanted plasma component. The IAM exerts two functions simultaneously, usual dialysis and elimination by immunoaffinity binding. The rat EC model has been applied as an evaluation system for the safety of medical devices in contact with the blood stream. Combining commonly used hemodialysis (HD) membranes with rat EC, we evaluated the elicitation of immunological responses, as well as the effect of repeated EC. The data suggest that this EC model can reproduce similar immunological responses in HD patients, and can be employed to evaluate medical devices and materials for their delayed, systemic, and repeated exposure effects. The EC system described here can reproduce human HD treatment, remove unwanted substances, and evaluate medical devices and materials for toxicological responses.

Rat extracorporeal circulation model for evaluation of systemic immunotoxicity

We have applied a rat extracorporeal circulation (EC) model as an evaluation system for the immunotoxicity of medical devices in contact with the blood stream. Combining popular hemodialysis (HD) membranes [a non-biocompatible membrane, Cupurophane (CUP), and more biocompatible membranes, Cu-ammonium rayon (CAR) and polyacrylonitrile (PAN)] with rat EC, we evaluated the elicitation of acute and delayed immunological responses, as well as the effect of repeated EC. Acute effect markers such as the production of tumor necrosis factor (TNF)-alpha and complement activity during EC, and delayed effect markers such as beta2-microglobulin (beta2-M), IgG, and complement 3 levels, were monitored. Acute markers after EC passage showed responses similar to those previously reported in patients with long-term hemodialysis such as TNF-alpha production and increased complement activity. Although beta2-M and IgG levels increased to 3- to 5-fold of the initial concentration within 4 weeks after rat EC, the trend of IgG increase was inversely correlated with membrane biocompatibility (CUP > CAR = PAN), but this did not occur for elevations in beta2-M (PAN > CAR > CUP). These data suggest that this EC model can reproduce similar immunological responses as seen in HD patients, and can be employed to evaluate medical devices and materials for their delayed, systemic, and repeated exposure effects with respect to immunotoxicity.

Selective removal of plasma components by high-performance immunoaffinity chromatography

Affinity chromatography employing immobilized antibody is a rapid and specific technique for isolating biologically active materials from different sources, and high-performance immunoaffinity chromatography (HPIAC) has been used to isolate antibodies and antigens for medical application. In an attempt to resolve the problem of amyloid deposition in dialysis patients, we used HPIAC to specifically remove beta2-microglobulin from human plasma. The use of a membrane as an affinity ligand support was also studied. The specific antibody immobilized on a membrane was highly effective for removal of rat immunoglobulin E passed through an extracorporeal circulation system (ECS). Then we investigated the removal of injected human serum amyloid P component from the blood of rats by means of the ECS. Biocompatibility of the specific antibody-bearing immunoaffinity membrane was also examined in terms of nonspecific binding of other plasma components. These techniques should prove useful for medical application and may have broad applicability for the elimination of any unwanted plasma component.

Selective removal of human serum amyloid P component from rat blood by use of an immunoaffinity membrane in an extracorporeal circulation system

We examined the suitability of an immunoaffinity membrane (IAM) bearing specific antibody as a ligand for removing human serum amyloid P component (hSAP) from blood passed through a simple extracorporeal circulation system established in rats. The specific antibody was the most effective of the various ligands tested for removing hSAP from human blood. To determine the value of the hSAP in human or rat plasma, we also developed a simple ELISA. In the rat extracorporeal circulation system, the hSAP level in the inlet blood to the IAM module decreased to 49% of the initial concentration within 60 min. In contrast, the hSAP remained at the initial concentration throughout the study in the module without the IAM. The use of this extracorporeal circulation system in this case allows preclinical evaluation of the ex vivo removal of a human plasma component in an animal model. Biocompatibility of the IAM was also examined. No change in blood cell counts or activation of the coagulation system occurred after contact with the IAM. Non-specific adsorption was not observed, since there was no statistically significant difference in IgG, complement C3, or albumin level between the pre- and post-treatment with this module. The immunological effects of the IAM were also examined using this system. Four weeks after the termination of the extracorporeal circulation, the rats examined showed no detectable antibody titer to the ligand.