Preparation of magnetic metal-organic framework nanocomposites for highly specific separation of histidine-rich proteins.

This work reports a novel metal-organic framework (MOF)-based metal affinity platform for the rapid and highly specific separation of histidine-rich proteins using zeolitic imidazolate framework-8 coated magnetic nanocomposites (denoted as Fe3O4@ZIF-8). The coating of the ZIF-8 layer on the Fe3O4 core was performed in aqueous solution at room temperature and merely took 10 minutes. The monodisperse Fe3O4@ZIF-8 has an average diameter of 190 nm, displays superparamagnetism with a saturation magnetization value of 47.9 emu g-1, and possesses a large external surface area of 131.0 m2 g-1. Due to the high density of low-coordinated Zn atoms on the surface of ZIF-8, Fe3O4@ZIF-8 exhibited a large adsorption capacity for model histidine-rich proteins (>6000 mg g-1 for bovine hemoglobin) and relatively low adsorption capacities for other proteins which contain fewer surface-exposed histidine residues. Moreover, Fe3O4@ZIF-8 showed excellent recyclability (more than 10 times) with high recovery (88.4%). In addition, Fe3O4@ZIF-8 can be used to selectively separate hemoglobin from a protein mixture and human blood samples. The good results demonstrate the potential of Fe3O4@ZIF-8 in the separation of histidine-rich proteins.