Magnetically Responsive Fe3O4@C@SnO2 Core-Shell Microspheres: Synthesis, Characterization and Application in Phosphoproteomics

In this work, we synthesized core-shell magnetic tin dioxide (Fe3O4@C@SnO2) microspheres. The Fe3O4@C@SnO2 microspheres were applied to enrich phosphopeptides for mass spectrometry analysis. Different from titanium and zirconium,the regular sol-gel process is not effective in generating tin dioxide on the magnetite particles because the tin oxide tends to crystallize during the reaction. Herein, we reported a simple but effective method combining solvothermal and hydrothermal reactions to synthesize Fe3O4@C@SnO2 microspheres. The obtained Fe3O4@C@SnO2 microspheres have a mean diameter of 340 nm, well-crystallized SnO2 shell (similar to 30 in thickness), and high magnetization (63.8 emu/g). We have also demonstrated that Fe3O4@C@SnO2 microspheres are the promising materials for convenient, efficient enrichment of phosphopeptides by the analysis of phosphopeptides in standard protein digestion and real samples using MALDI MS and LC-ESI MS.