In\nSitu MXene-Controlled Synthesis of Polycrystalline\nTiO<sub>2</sub> for Highly Efficient Enrichment of Phosphopeptides

Phosphopeptide\nenrichment methods based on commercial TiO<sub>2</sub> suffer from\ndifficulties in regulating intermolecular interactions,\nresulting in low coverage rate and the loss of information on multiphosphorylation\nsites, thereby limiting comprehensive phosphoproteomic analysis. In\nthis work, MXene Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> was incorporated into the design of enrichment materials,\nwith its surface structure functionalized and regulated to address\nthe low elution efficiency of TiO<sub>2</sub> for multiphosphorylated\npeptides. Upon oxidation treatment, the Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> material formed numerous uniformly\ndistributed TiO<sub>2</sub> nanoparticles on the surface of Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>-O, providing abundant\naffinity sites (Ti–O) for selective phosphopeptide enrichment.\nThe polycrystalline structure and rich oxygen vacancies of the material\neffectively regulated its binding affinity with phosphate groups,\nachieving simultaneous high-efficiency enrichment of both monophosphorylated\nand multiphosphorylated peptides. Its performance was significantly\nsuperior to that of commercial TiO<sub>2</sub> and IMAC materials.\nThis study presents great promise for the practical application of\ncomprehensive phosphoproteomic analysis in the future and broadens\nthe application of MXene in the biological field.