A Thioether-Bridging Surface Modification of Polymeric Microspheres Offers Nonbiological Protein A-Mimetic Affinity for IgG

Surface modification of polymeric materials to control their interaction with proteins has been studied extensively, leading to widespread bio-applications. However, the development of nonbiological, smart polymer surfaces, mimicking the recognition ability of biomolecules, remains a challenge. The present study presents a thioether-bridging surface modification of polymeric microspheres as a new approach for mimicking protein A affinity for immunoglobulin G (IgG). The bridge-modified surface is created through an epoxide linking reaction of porous polymeric microspheres with potassium thioacetate in a 2:1 molar ratio, acting as a protein A ligand, which is essential for industrial IgG purification. This surface exhibits buffer responsiveness and selective high-affinity binding to the IgG Fc region. Remarkably, a comparison among the binding behaviors of a series of thioether-modified microspheres indicates that bridging structures composed of β,β′-dihydroxysulfide play a predominant role in IgG recognition. This straightforward approach can lead to the development of economical and practical nonbiological alternatives to protein A-conjugated materials, providing solutions for various applications such as biosensors and site-specific reagents utilizing the affinity of the IgG Fc region. The improved understanding of protein interactions at bridged/non-bridged interfaces can be valuable in various applications such as implant materials and biomaterials.