Hybrid alginate–protein cryogel beads: efficient and sustainable bio-based materials to purify immunoglobulin G antibodies

Abstract

Antibodies present in mammal's serum are of high relevance for therapeutic purposes, particularly in passive immunization and in the treatment of some chronic diseases. However, their widespread use is still compromised by the requirement of several process steps for their purification and the difficulty in keeping antibodies stable to guarantee their therapeutic efficiency. These challenges significantly contribute to the current high cost of biopharmaceuticals, namely antibodies such as immunoglobulin G (IgG). Accordingly, the development of effective and sustainable purification strategies for antibodies and other biopharmaceuticals is in critical demand to decrease economic, environmental and health burdens. Herein, bio-based and low-cost hybrid alginate–protein cryogel beads were prepared, characterized, and applied as novel adsorbent materials for the purification of IgG from human serum. It is shown that hybrid materials are more efficient than the respective alginate beads since the presence of proteins increases the material selectivity for IgG, which is due to the specific interactions occurring between the target antibody and amino acid residues in the hybrid materials. Several operating conditions, such as pH, adsorption time and serum concentration, were optimized to improve the recovery yield and purity of IgG. Adsorption isotherms were determined to infer the adsorption mechanism of IgG onto the cryogel beads and to determine their adsorption capacity (175 mg of IgG per g of cryogel beads). Under the optimized conditions, IgG can be recovered from the hybrid materials using buffered aqueous solutions, with a purity of 80% and a recovery yield of 91%. The stability and integrity of the antibody are retained after the desorption step. Finally, the regeneration and reuse of the cryogel beads were evaluated, with no losses in the IgG adsorption performance and antibody stability. Although significant efforts have been put on the development of novel affinity ligands to replace the standard chromatographic methods to purify IgG, this work demonstrates the potential of bio-based and low-cost hybrid materials as promising alternatives, in which proteins can be used to improve the material selectivity.