Magnetic solid-phase extraction of protein with deep eutectic solvent immobilized magnetic graphene oxide nanoparticles

• A strategy for the solid-phase extraction of protein based on deep eutectic solvent (DES-SPE).
• Choline chloride-glycerin DES immobilized magnetic graphene oxide nanoparticles(Fe3O4–NH2@GO) was selected as the extractant.
• Ovalbumin, bovine serum albumin, bovine hemoglobin and lysozyme were used as the analyst.
• The desorption behavior of protein was evaluated.

As a new type of green solvent, four kinds of choline chloride (ChCl)-based deep eutectic solvents (DESs) have been synthesized, and then a core–shell structure magnetic graphene oxide (Fe3O4–NH2@GO) nanoparticles have been prepared and coated with the ChCl-based DESs. Magnetic solid-phase extraction (MSPE) based Fe3O4–NH2@GO@DES was studied for the first time for the extraction of proteins. The characteristic results of vibrating sample magnetometer (VSM), X-ray diffraction (XRD), Fourier transform infrared spectrometry (FT-IR), thermal gravimetric analysis (TGA) and field emission scanning electron microscopy (FESEM) indicated the successful preparation of Fe3O4–NH2@GO@DES. The concentrations of proteins in studies were determined by a UV–vis spectrophotometer. The advantages of Fe3O4–NH2@GO@DES in protein extraction were compared with Fe3O4–NH2@GO and Fe3O4–NH2, and Fe3O4–NH2@GO@ChCl–glycerol was selected as the suitable extraction solvent. The influence factors of the extraction process such as the pH value, the temperature, the extraction time, the concentration of protein and the amount of Fe3O4–NH2@GO@ChCl–glycerol were evaluated. Desorption experimental result showed 98.73% of BSA could be eluted from the solid extractant with 0.1 mol/L Na2HPO4 solution contained 1 mol/L NaCl. Besides, the conformation of BSA was not changed during the elution by the investigation of circular dichromism (CD) spectra. Furthermore, the analysis of real sample demonstrated that the prepared magnetic nanoparticles did have extraction ability on proteins in bovine whole blood.

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