In vitro Characterization of a Membrane-Based Low-Density Lipoprotein Affinity Adsorption Device

Abstract

The objective of this study was to explore the use of microporous membranes as an alternative substrate to porous beads in affinity adsorption of low-density lipoprotein (LDL) for therapeutic purposes. Flat sheet immunoaffinity membranes containing a polyclonal antibody preparation were utilized as the affinity substrate. The antibody was covalently immobilized to the surface through a poly(ethylene glycol) (PEG) spacer. Equilibrium adsorption of LDL from plasma was measured. Adsorption from plasma and elution of bound LDL using citrate buffer were studied as a function of flow rate.Specific capacity was as great as 2 mg apolipoprotein B per milliliter membrane volume. The superior transport properties of the membrane allowed rapid adsorption and regeneration, which translated to a large number of adsorptive cycles that can be performed within a given treatment time. On the basis of in vitro performance characteristics, it is estimated that an immunoaffinity membrane device can provide a reduction in patient plasma LDL concentration comparable to that provided by packed columns, but with almost an 80% reduction in the device volume.