Ionic liquid-coated Fe3O4/APTES/graphene oxide nanocomposites: synthesis, characterization and evaluation in protein extraction processes

Abstract

A magnetic solid-phase extraction (MSPE) procedure with a betaine-based ionic liquid (IL) coated 3-aminopropyltriethoxysilane (APTES)–Fe₃O₄ grafted graphene oxide (GO) nanocomposite (Fe₃O₄/APTES/GO/IL) as a magnetic adsorbent has been developed for protein extraction. A series of environmentally friendly ionic liquids (ILs) based on betaine and carboxylic acids have been prepared, and their structures have been confirmed by ¹H nuclear magnetic resonance (¹HNMR). Then the synthetic ionic liquids have been used to modify magnetic graphene oxide nanoparticles (Fe₃O₄/APTES/GO) to form Fe₃O₄/APTES/GO/IL. The as-prepared Fe₃O₄/APTES/GO/IL has been used to extract bovine serum albumin (BSA). After extraction, the concentration of protein in the supernatant was measured by UV-vis spectrophotometry. Several significant factors that affect the extraction amount, such as solution temperature, extraction time, protein concentration, ionic strength and pH value, were investigated. Experimental results show that the extraction amount could reach 139.1 mg g⁻¹. The advantages of Fe₃O₄/APTES/GO/IL in protein extraction were compared with bare Fe₃O₄ nanoparticles and Fe₃O₄/APTES/GO. Moreover, the extraction process of protein from bovine calf whole blood by Fe₃O₄/APTES/GO/IL has been performed to evaluate the practical applicability of the proposed method.