A deep eutectic solvent modified magnetic β-cyclodextrin particle for solid-phase extraction of trypsin

An environmentally friendly deep eutectic solvent (DES) composed of trifluoroacetamide and benzyltrimethylammonium chloride modified β-cyclodextrin (CD) grafted magnetic beads (MB-NH₂@CD@DES) were synthesized for the first time and applied to the solid-phase extraction of trypsin. Among the five trypsin extractants prepared in this work (MB, MB-NH₂, MB-NH₂@CD, MB-NH₂@DES, MB-NH₂@CD@DES), the extractant MB-NH₂@CD@DES with higher extraction capacity for trypsin was selected as final extractant. The extraction capacity of MB-NH₂@CD@DES for trypsin can reach up to 549.87 mg⋅g^-1 under the optimized conditions. The Langmuir adsorption equilibrium was found fitted better with equilibrium relation between MB-NH₂@CD@DES and trypsin than Freundlich adsorption equilibrium. And a superior extraction for trypsin was verified by comparing the extraction capacity of MB-NH₂@CD@DES for trypsin and four other common proteins. Compared with some reported trypsin extractants, the MB-NH₂@CD@DES had a shorter extraction process, higher extraction capacity, more convenient operation of separation, a safer and more environmentally friendly synthesis process. With the optimized eluent, a great elution rate (74.32%) of trypsin was achieved. The absolute recovery of trypsin in trypsin standard solution was calculated to be 16.8%. And the extraction capacity of MB-NH₂@CD@DES toward trypsin still maintained well after ten times recycling and reuse. The detection limit (LOD) and quantitative limit (LOQ) were 0.072 mg⋅mL^-1 and 0.240 mg⋅mL^-1 respectively. By sodium dodecyl sulfate polyacrylamide gel electrophoresis experiment, the extraction ability of MB-NH₂@CD@DES to trypsin from real sample was fully demonstrated. All above results showed the potential of fabricated MB-NH₂@CD@DES as a superior extractant for trypsin from real complex samples.