Facile synthesis of thiazole-functionalized magnetic microspheres for highly specific separation of heme proteins

A thiazole group containing two kinds of heteroatoms N and S has a large conjugated π bond and strong electronic ability, and it easily binds with metal ions to form metal complexes. In this paper, thiazole as an affinity group was designed to achieve the selective adsorption of heme proteins which have an iron-containing heme group. Thiazole-functionalized magnetic microspheres (Fe3O4@SiO2@AT) were synthesized by immobilizing 2-aminothiazole onto the surface of aminopropyl modified magnetic microspheres through a crosslinking reaction in which glutaraldehyde was a crosslinking agent. The elemental analysis and thermogravimetric data confirmed and quantified the immobilization of the thiazole group. Due to the covalent coordination between the thiazole group (lone pair electrons of the N atom) and the iron ion in the heme group, Fe3O4@SiO2@AT exhibited a high binding capacity for hemoglobin (2.02 g g−1) and a relatively low binding capacity for other proteins (lysozyme as a model protein) without a heme group. Moreover, the whole separation process required only 15 minutes, which was favorable for the separation of unstable proteins. In addition, Fe3O4@SiO2@AT was successfully applied to selectively separate hemoglobin from a binary protein mixture and human blood samples. These results demonstrated that the microspheres had potential use in the separation of heme proteins.