Polymeric ionic liquid-assembled graphene-immobilized silica composite for selective isolation of human serum albumin from human whole blood

Polymeric ionic liquids (PILs) with 1-vinyl-3-ethylimidazolium cations and two different anions of Br- and PF6 (-) were assembled onto the surface of graphene (G) nanosheets. The derived two composites, i.e., PIL(Br)-G and PIL(PF6)-G, were further efficiently immobilized onto the surface of silica nanoparticles via self-assembly technique. The obtained two PIL-G/SiO2 nanocomposites exhibited diverse adsorption performances toward proteins through adjusting the anions of PILs. Electrostatic attractions between proteins and the nanocomposites dominated protein adsorption, while the presence of PF6 (-) anions weakened electrostatic interactions and deteriorated the selective adsorption of target protein, i.e., bovine serum albumin (BSA) in this case. Specifically, PIL(Br)-G/SiO2 nanocomposite displayed high selectivity toward BSA and a high adsorption efficiency of ca. 98% was achieved for 100 mg L-1 BSA in a Britton-Robinson (B-R) buffer at pH 5. HPLC analysis demonstrated the selectivity of PIL(Br)-G/SiO2 nanocomposite toward BSA in the presence of abundant hemoglobin and cytochrome c. The practical applicability was verified by performing selective isolation of human serum albumin (HSA) from human whole blood.