Immobilization of proteins on gold coated porous membranes via an activated self-assembled monolayer of thioctic acid

Abstract

A new methodology for efficient protein (e.g., antibodies, enzymes, etc.) immobilization on microporous nylon membranes for use in a variety of bioanalytical systems is introduced. The method utilizes an activated self-assembled monolayer (SAM) of thioctic acid on gold coated forms of the membranes. Via a carbodiimide mediated reaction, the protein is anchored to the gold surface through an amide bond with the terminal carboxyl group of the adsorbed thioctic acid. The immobilization efficiency is high (∼95% for a monoclonal immunoglobulin G(IgG) and the surface bound protein appears to be stable enough to resist any displacement by other proteins in a matrix as complex as serum. Immunological activity of immobilized antibody is retained as demonstrated via use of such membrances in colorimetric ELISA for human chorionic gonadatropin (hCG). The high protein immobilization efficiency, the high tensile strength of microporous nylon membranes, and the excellent electrochemical characteristics of gold make this approach very attractive for preparing biomembranes that should be useful in affinity chromatography, electrochemical immunosensing systems, flow-through enzyme reactors, etc.