A novel dianionic amino acid ionic liquid-coated PEG 4000 modified Fe3O4 nanocomposite for the magnetic solid-phase extraction of trypsin

A novel magnetic extractant, PEG 4000 modified Fe3O4 nanomaterial that coated with dianionic amino acid ionic liquid (Fe3O4@PEG@DAAAIL), was successfully synthesized and characterized. X-ray diffraction (XRD), transmission electron microscope (TEM), vibrating sample magnetometer (VSM), fourier transform infrared spectrometry (FT-IR), thermal gravimetric analysis (TGA) and zeta potentials were used to confirm that the novel nanocomposite was successfully synthesized. Subsequently, the prepared Fe3O4@PEG@DAAAIL nano composite was used as the extractant for trypsin coupled with magnetic solid-phase extraction (MSPE). The concentrations of trypsin in the supernatant were detected by UV vis spectrophotometer at 278 nm. The extraction ability turned out to be better than the other four kinds of extractants prepared in this work. Furthermore, the influence of a series of factors, such as extraction time and temperature, initial trypsin concentration, the value of pH and ionic strength, was systematically investigated. Under the optimal extraction condition, the extraction capacity for trypsin could reach up to 718.73 mg/g, absolutely higher than that of other adsorbents reported. This satisfactory extraction capacity could be maintained unchangeable after at least eight days, and kept over 90% of initial extraction capacity after eight recycles. What's more, the activity of trypsin after extraction retained 92.29% of initial activity, verifying the biocompatibility of the prepared extractant. Finally, the developed Fe3O4@PEG@DAAAIL-MSPE method was successfully applied to the real sample analysis with satisfactory results. All of above proves the potential value of Fe3O4@PEG@DAAAIL-MSPE in the analysis of biomass.