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

In this work, we synthesized core−shell magnetic tin dioxide (Fe 3 O 4 @C@SnO 2 ) microspheres. The Fe 3 O 4 @C@SnO 2 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 Fe 3 O 4 @C@SnO 2 microspheres. The obtained Fe 3 O 4 @C@SnO 2 microspheres have a mean diameter of 340 nm, well-crystallized SnO 2 shell (∼30 in thickness), and high magnetization (63.8 emu/g). We have also demonstrated that Fe 3 O 4 @C@SnO 2 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.