Novel poly-deep eutectic solvent-functionalized magnetic graphene oxide nanomaterials for high-performance solid-phase extraction of trypsin†

Three novel polymethacrylic acid-based deep eutectic solvent (DES)-functionalized magnetic graphene oxide composites were designed and successfully synthesized via the radical polymerization method. The aim was to achieve the selective solid-phase extraction of trypsin (Tryp). Among them, the magnetic extractant (MGO@PDES₂) functionalized with a poly-deep eutectic solvent composed of tetraethylammonium chloride and methylpropionic acid at a molar ratio of 1 : 2 exhibited the highest extraction efficiency for Tryp. Owing to the high specific surface area of MGO and the abundant carboxyl functional groups in PDES₂, the prepared MGO@PDES₂ exhibited excellent selectivity and stability for Tryp extraction. Under optimal conditions, the extraction capacity of Tryp by MGO@PDES₂ reached 708.85 mg g⁻¹. The extraction driving forces between MGO@PDES₂ and Tryp were hydrogen-bonding interactions and electrostatic interactions. Among the seven biomacromolecules, MGO@PDES₂ displayed outstanding selectivity for Tryp. In addition, the results of cycling experiments indicated that MGO@PDES₂ could be reused many times without a significant change in extraction capacity. Moreover, the proposed method was successfully applied to extract Tryp from the crude extract of bovine pancreas, yielding satisfactory results. All the results suggest that MGO@PDES₂ is a promising magnetic extractant, which is expected to provide new ideas for the extraction and separation of proteins.