Pseudomorphic synthesis of monodisperse magnetic mesoporous silica microspheres for selective enrichment of endogenous peptides

In this work, we describe a novel synthetic strategy of magnetic mesoporous silica spheres (Fe3O4@mSiO2) for the selective enrichment of endogenous peptides. Fe3O4 particles were coated with silica shell by a sol–gel method, followed by pseudomorphic synthesis to transform nonporous silica shell into ordered mesoporous silica shell. The core/shell structure and mesostructure were individually fabricated in two steps, which can be expedient to independently optimize the properties of monodispersion, magnetization and mesostructure. Actually, it was confirmed that the produced Fe3O4@mSiO2 particles possess good monodispersion, high magnetization, superparamagnetism, uniform accessible mesopores, and large surface area and pore volume. With these good properties, Fe3O4@mSiO2 spheres were applied to the rapid enrichment of peptides. Based on the size-exclusion mechanism and hydrophobic interaction with siloxane bridge group mainly on the surface of inside pores, Fe3O4@mSiO2 can selectively capture peptides and exclude high-MW proteins and salts. Furthermore, peptides in human plasma were successfully enriched by Fe3O4@mSiO2.

► A novel synthetic strategy of Fe3O4@mSiO2 was described.
► Monodispersion, magnetization and mesostructure were independently optimized.
► Fe3O4@mSiO2 could selectively enrich peptides and exclude proteins and salts.
► The S/N ratio of peptide signal increased obviously after enriched by Fe3O4@mSiO2.
► A fast and selective method for detection of peptides in human plasma was proposed.