Precisely designed rattle-type mTiO2@P(NIPAM-co-MBA) microspheres with screening gel network for highly selective extraction of phosphopeptidome

Abstract

The selective extraction of phosphopeptidome from complicated biological samples is of great importance for the development of diagnostic and prognostic biomarkers, but still remains a challenge. In this work, rattle-type mTiO₂@P(NIPAM-co-MBA) composite microspheres comprising a mesoporous crystalline mTiO₂ core, an intermediate hollow space and a crosslinked P(NIPAM-co-MBA) network shell were elaborately designed and fabricated via two-step reflux-precipitation polymerization followed by a hydrothermal process. First, a non-crosslinked PMAA layer was directly coated onto the surface of the TiO₂ core without any pretreatment. Then, the formed TiO₂@PMAA was encapsulated with another crosslinked P(NIPAM-co-MBA) layer with the aid of the strong hydrogen-bonding interaction between the two polymer layers. Finally, a hydrothermal process was adopted to convert the TiO₂ core into a crystalline and mesoporous counterpart. At the same time, a non-crosslinked PMAA layer was selectively removed to form a rattle-type structure. The crosslinked P(NIPAM-co-MBA) shell makes the rattle-type mTiO₂@P(NIPAM-co-MBA) possess great size-exclusion effect against both high-molecular-weight nonphosphoproteins and high-molecular-weight phosphoproteins, while the mTiO₂ core was responsible of the selective enrichment of the low-molecular-weight phosphopeptides. With the help of these unique properties, the rattle-type mTiO₂@P(NIPAM-co-MBA) microspheres show excellent potential for the one-step selective extraction of the phosphopeptidome.