In Situ MXene-Controlled Synthesis of Polycrystalline TiO₂ for Highly Efficient Enrichment of Phosphopeptides

Phosphopeptide enrichment methods based on commercial TiO₂ suffer from difficulties in regulating intermolecular interactions, resulting in low coverage rate and the loss of information on multiphosphorylation sites, thereby limiting comprehensive phosphoproteomic analysis. In this work, MXene Ti₃C₂T_x was incorporated into the design of enrichment materials, with its surface structure functionalized and regulated to address the low elution efficiency of TiO₂ for multiphosphorylated peptides. Upon oxidation treatment, the Ti₃C₂T_x material formed numerous uniformly distributed TiO₂ nanoparticles on the surface of Ti₃C₂T_x-O, providing abundant affinity sites (Ti-O) for selective phosphopeptide enrichment. The polycrystalline structure and rich oxygen vacancies of the material effectively regulated its binding affinity with phosphate groups, achieving simultaneous high-efficiency enrichment of both monophosphorylated and multiphosphorylated peptides. Its performance was significantly superior to that of commercial TiO₂ and IMAC materials. This study presents great promise for the practical application of comprehensive phosphoproteomic analysis in the future and broadens the application of MXene in the biological field.